National Library of Energy BETA

Sample records for lone star hub

  1. Clean Cities: Lone Star Clean Fuels Alliance (Central Texas)...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Lone Star Clean Fuels Alliance (Central Texas) Coalition The Lone Star Clean Fuels Alliance (Central Texas) coalition works with vehicle fleets, fuel providers, community leaders,...

  2. Lone Star Healthy Streams Final Report 

    E-Print Network [OSTI]

    Wagner, Kevin; Redmon, Larry

    2011-01-01

    2010. The Lone Star Healthy Streams Bibliography was then converted into an online searchable database accessible from http://lshs.tamu.edu. As information was collected, it was incorporated into the LSHS Power Point presentation and guidance manual... bacteria from grazing lands has been identified as a significant source of bacterial contamination in need of reductions to improve water quality. Development of best management practices to address these bacterial issues is critical to the success...

  3. Lone Star Transmission LLC | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIXsource History ViewInformationWindsCompressedListguided wavesLone Star I4Q07)

  4. Lone Star Healthy Streams: Teaching best management practices statewide 

    E-Print Network [OSTI]

    Lee, Leslie

    2010-01-01

    ) using Clean Water Act Nonpoint Source Grant funding from the U.S. Environmental Protection Agency. Since its inception, LSHS has involved numerous collabo- rators, including TSSWCB, U.S. The Lone Star Healthy Streams Program teaches owners...

  5. Lone Star Healthy Streams: Teaching best managment practices statewide 

    E-Print Network [OSTI]

    Lee, Leslie

    2011-01-01

    ) using Clean Water Act Nonpoint Source Grant funding from the U.S. Environmental Protection Agency. Since its inception, LSHS has involved numerous collabo- rators, including TSSWCB, U.S. The Lone Star Healthy Streams Program teaches owners...

  6. Lone Star I (Q2) Wind Farm | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIXsource History ViewInformationWindsCompressedListguided wavesLone Star I (4Q07)

  7. Lone Star I (Q3) Wind Farm | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIXsource History ViewInformationWindsCompressedListguided wavesLone Star I (4Q07)Q3)

  8. Lone Star Wind Alliance LSWA | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIXsource History ViewInformationWindsCompressedListguided wavesLone Star I4Q07)Wind

  9. Lone Star Reds: the Socialist Party and cotton tenancy in Texas, 1901-1917 

    E-Print Network [OSTI]

    Mellard, Jason Dean

    2000-01-01

    ideal, the party of Eugene Debs seized on the strong Texas tradition of agrarian revolt to build a formidable, if short-lived, Socialist movement in the Lone Star State. There were Socialist newspapers, unions, rural encampments, and a Socialist...

  10. Audit of Lone Star Gas Invoices and Billing Procedures, Task #3 

    E-Print Network [OSTI]

    Turner, W. D.; Liu, M.

    1997-01-01

    At the request of the TAMU Power Plant, the ESL staff audited the 1995 Lone Star Gas Company invoices. Gas consumption is measured and the measured volume is converted to standard volume (at T=60 °F, P= 14.65 psia) to determine the energy content...

  11. Development of a Synergistic, Comprehensive Statewide Lone Star Healthy Streams Program 

    E-Print Network [OSTI]

    Wagner, K.; Redmon, L.; Peterson, J.

    2013-01-01

    • October 19, 2010 • March 9, 2011 • June 23, 2011 • October 24, 2011 • February 15, 2012 Subtask 1.4: Development of Final Report The final report was compiled by TWRI staff and submitted on April 30, 2013. Task 2: LSHS Program Coordination... Technical Report 446 September 2013 Development of a Synergistic, Comprehensive Statewide Lone Star Healthy Streams Program 2 Executive Summary According to the 2008 Texas Water Quality Inventory and 303(d) List, 295 waterbodies...

  12. Lone Star I (4Q07) Wind Farm | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIXsource History ViewInformationWindsCompressedListguided wavesLone Star I (4Q07) Wind

  13. Lone Star II (1Q08) Wind Farm | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIXsource History ViewInformationWindsCompressedListguided wavesLone Star I (4Q07)Q3)II

  14. Lone Star II (2Q08) Wind Farm | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIXsource History ViewInformationWindsCompressedListguided wavesLone Star I

  15. Lone Star II (4Q07) Wind Farm | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIXsource History ViewInformationWindsCompressedListguided wavesLone Star I4Q07) Wind

  16. LoneSTAR Program: Maximizing Energy Efficiency while Protecting the Envrionment 

    E-Print Network [OSTI]

    Trevino, E.

    2014-01-01

    iency whi le Protect ing the Envi ronment LoanSTAR PROGRAM ESL-KT-14-11-31 CATEE 2014: Clean Air Through Efficiency Conference, Dallas, Texas Nov. 18-20 ? Executed 240 loans totaling $407,923,762.32 ? 93 loans to publ ic schools distr icts ? 80 loans...-11-31 CATEE 2014: Clean Air Through Efficiency Conference, Dallas, Texas Nov. 18-20 BASICS ? I t ’s al l about the ut i l i ty dollar savings ? Loan must have a composite simple payback of 10 years or less ? The simple payback is the loan term ? Each loan...

  17. Money earmarked for cervid research at Texas Tech -Texas Hunting & Fishing | Lone Star Outdoor News http://www.lsonews.com/money-earmarked-cervid-research-texas-tech/[8/11/2014 8:25:26 AM

    E-Print Network [OSTI]

    Rock, Chris

    Money earmarked for cervid research at Texas Tech - Texas Hunting & Fishing | Lone Star Outdoor News http://www.lsonews.com/money-earmarked-cervid-research-texas-tech/[8/11/2014 8:25:26 AM] Money earmarked for cervid research at Texas Tech By Conor Harrison on August 8, 2014 in Texas Hunting 0 Texas

  18. Energy Efficient Buildings Hub

    SciTech Connect (OSTI)

    2013-04-01

    Energy Efficient Buildings HUB Lunch Presentation for the 2013 Building Technologies Office's Program Peer Review

  19. Energy Efficient Buildings Hub

    Broader source: Energy.gov [DOE]

    The U.S. Department of Energy created the Energy Efficient Buildings Hub in Philadelphia, Pennsylvania to promote regional job creation and economic growth while also improving the energy...

  20. Hub Overview | JCESR

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefieldSulfateSciTechtail.Theory ofDid you notHeat Pumps Heat Pumps AnAbout Energy.govHonorsAbout » FieldHub

  1. Hubs | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on Delicious Rank EERE: Alternative Fuels Data CenterFinancial OpportunitiesDepartment ofScienceHow Much Do You SpendHubs

  2. Congestion delays at hub airports

    E-Print Network [OSTI]

    St. George, Martin J.

    1986-01-01

    A deterministic model was developed to study the effects of inefficient scheduling on flight delays at hub airports. The model bases the delay calculation on published schedule data and on user-defined airport capacities. ...

  3. An overview of the SUPERGEN Bioenergy Hub

    E-Print Network [OSTI]

    integrated assessment 8. Carbon capture & storage enabling technologies 9. Bio-oil upgrading SGB Hub Projects to national economy via employment and manufacturing Capital investment per unit of capacity Why we need a hub

  4. Lone Star Healthy Streams: Keeping Texas streams clean 

    E-Print Network [OSTI]

    Boutwell, Kathryn S.

    2013-01-01

    ,? said Jennifer Peterson, LSHS statewide coordinator. ?For each bacterial contributor, we created a manual and a presentation outlining BMPs that are operation- speci?c.? ?e program published manuals for poultry, beef ca?le, feral hogs, horses.... Dairy Cattle: Construct a waste treatment lagoon by building an embankment and/or excavating a pit or dugout to biologically treat waste. Feral Hogs: Although they require more effort to install and maintain, using corral traps is extremely...

  5. Fuels From Sunlight Hub | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    have the potential to transform America's energy future. The Joint Center for Artificial Photosynthesis (JCAP) The Fuels from Sunlight Energy Innovation Hub was specifically...

  6. Redesign of a wind turbine hub

    E-Print Network [OSTI]

    Hunter-Jones, Bridget I

    2014-01-01

    The current designs of wind turbine hubs contain many faults. The slew ring bearing that connects the blade to the hub takes on a large bending moment that in many cases causes the joints to fail and the blade to break ...

  7. doe energy innovation hubs | netl.doe.gov

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    DOE Energy Innovation Hubs The U.S. Department of Energy's Energy Innovation Hubs initiative addresses research challenges with potentially high impact on our national energy...

  8. Energy Innovation Hub Report Shows Philadelphia-area Building...

    Office of Environmental Management (EM)

    Innovation Hub Report Shows Philadelphia-area Building Retrofits Could Support 23,500 Jobs Energy Innovation Hub Report Shows Philadelphia-area Building Retrofits Could Support...

  9. Energy Department to Launch New Energy Innovation Hub Focused...

    Office of Environmental Management (EM)

    to Launch New Energy Innovation Hub Focused on Advanced Batteries and Energy Storage Energy Department to Launch New Energy Innovation Hub Focused on Advanced Batteries and Energy...

  10. Energy Innovation Hubs Online Q&A

    Broader source: Energy.gov [DOE]

    Energy Secretary Steven Chu hosted a live, streaming Q&A session with the directors of the Energy Innovation Hubs on March 6, 2012. The directors were asked questions regarding their teams' work...

  11. Wind turbine rotor hub and teeter joint

    DOE Patents [OSTI]

    Coleman, Clint (Warren, VT); Kurth, William T. (Warren, VT); Jankowski, Joseph (Stowe, VT)

    1994-10-11

    A rotor hub is provided for coupling a wind turbine rotor blade and a shaft. The hub has a yoke with a body which is connected to the shaft, and extension portions which are connected to teeter bearing blocks, each of which has an aperture. The blocks are connected to a saddle which envelops the rotor blade by one or two shafts which pass through the apertures in the bearing blocks. The saddle and blade are separated by a rubber interface which provides for distribution of stress over a larger portion of the blade. Two teeter control mechanisms, which may include hydraulic pistons and springs, are connected to the rotor blade and to the yoke at extension portions. These control mechanisms provide end-of-stroke damping, braking, and stiffness based on the teeter angle and speed of the blade.

  12. Evaluating the Web Hubs and Authorities

    E-Print Network [OSTI]

    Ullman, Jeffrey D.

    1 Evaluating the Web PageRank Hubs and Authorities #12;2 PageRank Intuition: solve the recursive = the principal eigenvector of the stochastic matrix of the Web. A few fixups needed. #12;3 Stochastic Matrix of the Web Enumerate pages. Page i corresponds to row and column i. M [i,j ] = 1/n if page j links to n pages

  13. Energy Efficient Buildings Hub | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on Delicious Rank EERE: AlternativeCommunication3-EDepartment of EnergyDepartmentEfficient Buildings Hub Energy

  14. Energy Department Announces Launch of Energy Innovation Hub for...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    since 2010. The other Energy Innovation Hubs are: The Joint Center for Artificial Photosynthesis, which focuses on advanced research to produce fuels directly from sunlight....

  15. Modeling and Simulation for Nuclear Reactors Hub | Department...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    to help the nuclear industry make reactors more efficient through computer modeling and simulation. The Department's Energy Innovation Hubs are helping to advance promising areas...

  16. EnergyHub | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIX E LISTStar2-0057-EA Jump to:of theClimateElgin,WindMap: Name:Data.govEnergy.govEnergyHub

  17. Applying a MEIO approach to manage Intel's VMI Hub Supply

    E-Print Network [OSTI]

    Hsieh, Min Fang, M.B.A. Massachusetts Institute of Technology

    2011-01-01

    To improve customer service levels, Intel implemented Vendor Managed Inventory (VMI) hub process for its Central Processing Unit (CPU) Finished Good (FG) inventory, which allows Intel's customers to pull inventory directly ...

  18. Innovation Hub / Engineering Central BREEAM Information Introduction what is BREEAM?

    E-Print Network [OSTI]

    Martin, Ralph R.

    Innovation Hub / Engineering Central BREEAM Information Introduction ­ what is BREEAM? BREEAM' and `Outstanding'. The predefined criteria are sorted into a number of different categories: Energy, Management Engineering Central forms part of the College of Engineering and focuses on advanced engineering

  19. Interface structure for hub and mass attachment in flywheel rotors

    DOE Patents [OSTI]

    Deteresa, S.J.; Groves, S.E.

    1998-06-02

    An interface structure is described for hub and mass attachment in flywheel rotors. The interface structure efficiently transmits high radial compression forces and withstands both large circumferential elongation and local stresses generated by mass-loading and hub attachments. The interface structure is comprised of high-strength fiber, such as glass and carbon, woven into an angle pattern which is about 45{degree} with respect to the rotor axis. The woven fiber is bonded by a ductile matrix material which is compatible with and adheres to the rotor material. This woven fiber is able to elongate in the circumferential direction to match the rotor growth during spinning. 2 figs.

  20. Physiological Ageing as it is Related to Gene Function in the Lone Star Tick, Amblyomma americanum 

    E-Print Network [OSTI]

    Catena, Amanda M.

    2010-07-14

    and appeared to remain at those low levels for the duration of the study. The female experimental group differed from the other three groups by gradually upregulating tick actin during the study. 19 Fig. 7. Four graphs plotting electrophoresis gel band...

  1. "Climate Wise" in the Lone Star State: A Successful Partnership for Energy Efficiency in Austin, Texas 

    E-Print Network [OSTI]

    Allen, S. J.; Schare, S.

    1997-01-01

    The City of Austin, Texas is forming partnerships with local companies to lower energy consumption and improve environmental performance within the industrial sector. As a local government participant in the federal Climate Wise program, Austin...

  2. Policy Recommendations for Establishing the LoneSTAR Monitoring and Analysis Program 

    E-Print Network [OSTI]

    Claridge, D. E.; O'Neal, D. L.; Turner, W. D.

    1989-01-01

    The major objectives of the Monitoring and Analysis Program (MAP) should be to: Verify energy and dollar savings of the retrofits; Reduce energy costs by identifying operational and maintenance improvements at facilities receiving retrofits; Improve...

  3. Department of Energy to Invest $366M in Energy Innovation Hubs...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Department of Energy to Invest 366M in Energy Innovation Hubs Department of Energy to Invest 366M in Energy Innovation Hubs December 22, 2009 - 12:00am Addthis Washington, DC -...

  4. Offshore Series Wind Turbine Variable Hub heights & rotor diameters

    E-Print Network [OSTI]

    Firestone, Jeremy

    3.6MW Offshore Series Wind Turbine GE Energy #12;Feature Variable Hub heights & rotor diameters-savings feature, considering the rigors of offshore power generation. The 3.6 MW offshore wind turbine also, for both on and offshore use. Special features include... As the world's first commercially available wind

  5. Offshore Series Wind Turbine Variable Hub heights & rotor diameters

    E-Print Network [OSTI]

    Firestone, Jeremy

    3.6MW Offshore Series Wind Turbine GE Energy #12;Feature Variable Hub heights & rotor diameters and providing longer turbine life GE's unique electronics provide transmission efficiencies and enable harmonious function within the local grid Allows wind turbines to stay on line generating power, even during

  6. Natural Gas Market Centers and Hubs: A 2003 Update

    Reports and Publications (EIA)

    2003-01-01

    This special report looks at the current status of market centers/hubs in today's natural gas marketplace, examining their role and their importance to natural gas shippers, marketers, pipelines, and others involved in the transportation of natural gas over the North American pipeline network.

  7. e-Ireland: Europe's New Internet Hub Hrvoje Benko

    E-Print Network [OSTI]

    Benko, Hrvoje

    e-Ireland: Europe's New Internet Hub Hrvoje Benko In a few years' time, there will be no Internet Europe and Asian-Pacific countries experience intensive growth in 2002. (Forrester) The amazing thing. It appears that Ireland is just coming out of the "catching up" phase with the rest of Europe

  8. Energy Innovation Hubs: A Home for Scientific Collaboration

    ScienceCinema (OSTI)

    Chu, Steven

    2013-05-29

    Secretary Chu will host a live, streaming Q&A session with the directors of the Energy Innovation Hubs on Tuesday, March 6, at 2:15 p.m. EST. The directors will be available for questions regarding their teams' work and the future of American energy. Ask your questions in the comments below, or submit them on Facebook, Twitter (@energy), or send an e-mail to newmedia@hq.doe.gov, prior or during the live event. Dr. Hank Foley is the director of the Greater Philadelphia Innovation Cluster for Energy-Efficient Buildings, which is pioneering new data intensive techniques for designing and operating energy efficient buildings, including advanced computer modeling. Dr. Douglas Kothe is the director of the Consortium for Advanced Simulation of Light Water Reactors, which uses powerful supercomputers to create "virtual" reactors that will help improve the safety and performance of both existing and new nuclear reactors. Dr. Nathan Lewis is the director of the Joint Center for Artificial Photosynthesis, which focuses on how to produce fuels from sunlight, water, and carbon dioxide. The Energy Innovation Hubs are major integrated research centers, with researchers from many different institutions and technical backgrounds. Each hub is focused on a specific high priority goal, rapidly accelerating scientific discoveries and shortening the path from laboratory innovation to technological development and commercial deployment of critical energy technologies. Ask your questions in the comments below, or submit them on Facebook, Twitter (@energy), or send an e-mail to newmedia@energy.gov, prior or during the live event. The Energy Innovation Hubs are major integrated research centers, with researchers from many different institutions and technical backgrounds. Each Hub is focused on a specific high priority goal, rapidly accelerating scientific discoveries and shortening the path from laboratory innovation to technological development and commercial deployment of critical energy technologies. Dr. Hank Holey is the director of the Greater Philadelphia Innovation Cluster for Energy-Efficient Buildings, which is pioneering new data intensive techniques for designing and operating energy efficient buildings, including advanced computer modeling. Dr. Douglas Kothe is the director of the Modeling and Simulation for Nuclear Reactors Hub, which uses powerful supercomputers to create "virtual" reactors that will help improve the safety and performance of both existing and new nuclear reactors. Dr. Nathan Lewis is the director of the Joint Center for Artificial Photosynthesis Hub, which focuses on how to produce biofuels from sunlight, water, and carbon dioxide.

  9. Beyond the Lone-Pair Model for Structurally Distorted Metal Oxides

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 Outreach Home Room News PublicationsAudits & InspectionsBeryllium and ChronicBestBeyond the Lone-Pair Model

  10. Revisiting Date and Party Hubs: Novel Approaches to Role Assignment in Protein Interaction Networks

    E-Print Network [OSTI]

    Sumeet Agarwal; Charlotte M. Deane; Mason A. Porter; Nick S. Jones

    2010-05-05

    The idea of 'date' and 'party' hubs has been influential in the study of protein-protein interaction networks. Date hubs display low co-expression with their partners, whilst party hubs have high co-expression. It was proposed that party hubs are local coordinators whereas date hubs are global connectors. Here we show that the reported importance of date hubs to network connectivity can in fact be attributed to a tiny subset of them. Crucially, these few, extremely central, hubs do not display particularly low expression correlation, undermining the idea of a link between this quantity and hub function. The date/party distinction was originally motivated by an approximately bimodal distribution of hub co-expression; we show that this feature is not always robust to methodological changes. Additionally, topological properties of hubs do not in general correlate with co-expression. Thus, we suggest that a date/party dichotomy is not meaningful and it might be more useful to conceive of roles for protein-protein interactions rather than individual proteins. We find significant correlations between interaction centrality and the functional similarity of the interacting proteins.

  11. DataHub project (Smart Grid Project) | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTIONRobertsdale, Alabama (UtilityInstruments Inc JumpIowa: EnergyDarkEnergy2007)DataHub project (Smart

  12. Energy Innovation Hub Directors Visit the Hill | Department of Energy

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 Outreach Home Room NewsInformation Current HABFES ScienceInformationInformationForDepartmentTheConsumptionHub

  13. Report of the Hubs+ Task Force | Department of Energy

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantityBonneville Power Administration wouldMassR&D100 Winners *ReindustrializationEnergyWind Energy WindHubs+ Task Force

  14. What are the Energy Innovation Hubs? | Department of Energy

    Office of Environmental Management (EM)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of Natural GasAdjustmentsShirley Ann Jackson About1996HowFOAShowingFuelWeatherize » Airare the Energy Innovation Hubs? What

  15. New Global Oil & Gas Hub in Oklahoma City | GE Global Research

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Selects Oklahoma City Site for New Global Hub of Oil & Gas Technology Innovation Click to email this to a friend (Opens in new window) Share on Facebook (Opens in new window) Click...

  16. Welcome and Overview of Workshop and Energy Innovation Hubs Video (Text Version)

    Broader source: Energy.gov [DOE]

    This is a text version of the welcome and overview of the workshop and energy innovation hubs video presented at the Critical Materials Workshop, held on April 3, 2012 in Arlington, Virginia.

  17. Development of Panama as a logistics hub and the impact on Latin America

    E-Print Network [OSTI]

    Muñoz, Daniel, M. Eng. Massachusetts Institute of Technology

    2010-01-01

    The Panamanian government is executing an aggressive economic growth initiative to transform the country into a regional logistics hub, like Singapore or Dubai. Two elements of the initiative are expansion of the Panama ...

  18. Evaluation and Demonstration of BMPs for Cattle on Grazing Lands for the Lone Star Healthy Streams Program 

    E-Print Network [OSTI]

    Wagner, K.; Redmon, L.; Gentry, T.; Clary, C.

    2013-01-01

    Committee .......................................................... 9 Subtask 1.8 Development of the final project report ........................................................................... 9 Task 2: Quality Assurance... Report ? November 15, 2010 TWRI Submitted Quarter 2 Progress Report ? March 14, 2011 TWRI Submitted Quarter 3 Progress Report ? June 14, 2011 TWRI Submitted Quarter 4 Progress Report ? September 15, 2011 TWRI Submitted Quarter 5 Progress Report...

  19. Surface--micromachined rotatable member having a low-contact-area hub

    DOE Patents [OSTI]

    Rodgers, M. Steven (Albuquerque, NM); Sniegowski, Jeffry J. (Edgewood, NM)

    2002-01-01

    A surface-micromachined rotatable member formed on a substrate and a method for manufacturing thereof are disclosed. The surface-micromachined rotatable member, which can be a gear or a rotary stage, has a central hub, and an annulus connected to the central hub by an overarching bridge. The hub includes a stationary axle support attached to the substrate and surrounding an axle. The axle is retained within the axle support with an air-gap spacing therebetween of generally 0.3 .mu.m or less. The rotatable member can be formed by alternately depositing and patterning layers of a semiconductor (e.g. polysilicon or a silicon-germanium alloy) and a sacrificial material and then removing the sacrificial material, at least in part. The present invention has applications for forming micromechanical or microelectromechanical devices requiring lower actuation forces, and providing improved reliability.

  20. Surface-micromachined rotatable member having a low-contact-area hub

    DOE Patents [OSTI]

    Rodgers, M. Steven; Sniegowski, Jeffry J.; Krygowski, Thomas W.

    2003-11-18

    A surface-micromachined rotatable member formed on a substrate and a method for manufacturing thereof are disclosed. The surface-micromachined rotatable member, which can be a gear or a rotary stage, has a central hub, and an annulus connected to the central hub by an overarching bridge. The hub includes a stationary axle support attached to the substrate and surrounding an axle. The axle is retained within the axle support with an air-gap spacing therebetween of generally 0.3 .mu.m or less. The rotatable member can be formed by alternately depositing and patterning layers of a semiconductor (e.g. polysilicon or a silicon-germanium alloy) and a sacrificial material and then removing the sacrificial material, at least in part. The present invention has applications for forming micromechanical or microelectromechanical devices requiring lower actuation forces, and providing improved reliability.

  1. Why Do Hubs in the Yeast Protein Interaction Network Tend To Be Essential: Reexamining the Connection

    E-Print Network [OSTI]

    O'Leary, Dianne P.

    National Center of Biotechnology Information, National Library of Medicine, National Institutes of Health were supported by the Intramural Research Program of the NIH and the National Library of Medicine. DPO for the centrality-lethality rule, one relating the essentiality of hubs to their role in the overall network

  2. License Usage and Changes: A Large-Scale Study of Java Projects on GitHub

    E-Print Network [OSTI]

    Poshyvanyk, Denys

    License Usage and Changes: A Large-Scale Study of Java Projects on GitHub Christopher Vendome1 -- 4 University of Victoria, BC, Canada Abstract--Software licenses determine, from a legal point of view, under which conditions software can be integrated, used, and above all, redistributed. Licenses

  3. Does CO2 Permeate through Aquaporin-1? Jochen S. Hub and Bert L. de Groot

    E-Print Network [OSTI]

    de Groot, Bert

    Does CO2 Permeate through Aquaporin-1? Jochen S. Hub and Bert L. de Groot Computational molecular dynamics simulations that address the question of CO2 permeation through human aquaporin-1. Free for a palmitoyloleoylphosphatidylethanolamine lipid bilayer membrane. The results indicate that significant aquaporin- 1-mediated CO2 permeation

  4. Expansion of point-to-point routes by low-cost carriers in hub networks : traffic and revenue impacts

    E-Print Network [OSTI]

    Zerbib, Gregory (Gregory Jean-Jacques)

    2006-01-01

    Legacy carriers developed hub networks to achieve a high concentration of operations, increase frequency, and serve multiple Origin-Destination markets with maximum efficiency. By contrast, the rapid emergence of low-cost ...

  5. Establishment of a Hub for the Light Water Reactor Sustainability Online Monitoring Community

    SciTech Connect (OSTI)

    Nancy J. Lybeck; Magdy S. Tawfik; Binh T. Pham

    2011-08-01

    Implementation of online monitoring and prognostics in existing U.S. nuclear power plants will involve coordinating the efforts of national laboratories, utilities, universities, and private companies. Internet-based collaborative work environments provide necessary communication tools to facilitate interaction between geographically diverse participants. Available technologies were considered, and a collaborative workspace was established at INL as a hub for the light water reactor sustainability online monitoring community.

  6. Kepler-424 b: A 'lonely' hot Jupiter that found A companion

    SciTech Connect (OSTI)

    Endl, Michael; Caldwell, Douglas A.; Barclay, Thomas; Huber, Daniel; Havel, Mathieu; Howell, Steve B.; Quintana, Elisa; Isaacson, Howard; Buchhave, Lars A.; Brugamyer, Erik; Robertson, Paul; Cochran, William D.; MacQueen, Phillip J.; Lucas, Phillip; Fischer, Debra; Ciardi, David R.

    2014-11-10

    Hot Jupiter systems provide unique observational constraints for migration models in multiple systems and binaries. We report on the discovery of the Kepler-424 (KOI-214) two-planet system, which consists of a transiting hot Jupiter (Kepler-424b) in a 3.31 day orbit accompanied by a more massive outer companion in an eccentric (e = 0.3) 223 day orbit. The outer giant planet, Kepler-424c, is not detected transiting the host star. The masses of both planets and the orbital parameters for the second planet were determined using precise radial velocity (RV) measurements from the Hobby-Eberly Telescope (HET) and its High Resolution Spectrograph (HRS). In stark contrast to smaller planets, hot Jupiters are predominantly found to be lacking any nearby additional planets; they appear to be {sup l}onely{sup .} This might be a consequence of these systems having a highly dynamical past. The Kepler-424 planetary system has a hot Jupiter in a multiple system, similar to ? Andromedae. We also present our results for Kepler-422 (KOI-22), Kepler-77 (KOI-127), Kepler-43 (KOI-135), and Kepler-423 (KOI-183). These results are based on spectroscopic data collected with the Nordic Optical Telescope (NOT), the Keck 1 telescope, and HET. For all systems, we rule out false positives based on various follow-up observations, confirming the planetary nature of these companions. We performed a comparison with planetary evolutionary models which indicate that these five hot Jupiters have heavy element contents between 20 and 120 M {sub ?}.

  7. Wind Turbine Towers for Greater Hub Heights Why higher wind turbine tower can contribute to increase energy

    E-Print Network [OSTI]

    McCalley, James D.

    towers represent 26% of the total WTG (Wind Turbine Generator) cost #12;Why concrete towerWind Turbine Towers for Greater Hub Heights Why higher wind turbine tower can contribute to increase energy output? · Energy output is proportional to the cube of wind velocity, 100m towers (versus

  8. Electron lone pair distortion facilitated metal-insulator transition in ?-Pb{sub 0.33}V{sub 2}O{sub 5} nanowires

    SciTech Connect (OSTI)

    Wangoh, L.; Quackenbush, N. F.; Marley, P. M.; Banerjee, S.; Sallis, S.; Fischer, D. A.; Woicik, J. C.; Piper, L. F. J.

    2014-05-05

    The electronic structure of ?-Pb{sub 0.33}V{sub 2}O{sub 5} nanowires has been studied with x-ray photoelectron spectroscopy techniques. The recent synthesis of defect-free ?-Pb{sub 0.33}V{sub 2}O{sub 5} nanowires resulted in the discovery of an abrupt voltage-induced metal insulator transition. First principle calculations predicted an additional V-O-Pb hybridized “in-gap” state unique to this vanadium bronze playing a significant role in facilitating the transition. We confirm the existence, energetic position, and orbital character of the “in-gap” state. Moreover, we reveal that this state is a hybridized Pb 6s–O 2p antibonding lone pair state resulting from the asymmetric coordination of the Pb{sup 2+} ions.

  9. A Multi-Objective, Hub-and-Spoke Supply Chain Design Model For Densified Biomass

    SciTech Connect (OSTI)

    Md S. Roni; Sandra Eksioglu; Kara G. Cafferty

    2014-06-01

    In this paper we propose a model to design the supply chain for densified biomass. Rail is typically used for long-haul, high-volume shipment of densified biomass. This is the reason why a hub-and-spoke network structure is used to model this supply chain. The model is formulated as a multi-objective, mixed-integer programing problem under economic, environmental, and social criteria. The goal is to identify the feasibility of meeting the Renewable Fuel Standard (RFS) by using biomass for production of cellulosic ethanol. The focus in not just on the costs associated with meeting these standards, but also exploring the social and environmental benefits that biomass production and processing offers by creating new jobs and reducing greenhouse gas (GHG) emissions. We develop an augmented ?-constraint method to find the exact Pareto solution to this optimization problem. We develop a case study using data from the Mid-West. The model identifies the number, capacity and location of biorefineries needed to make use of the biomass available in the region. The model estimates the delivery cost of cellulosic ethanol under different scenario, the number new jobs created and the GHG emission reductions in the supply chain.

  10. A Multi-Objective, Hub-and-Spoke Supply Chain Design Model for Densified Biomass

    SciTech Connect (OSTI)

    Jacob J. Jacobson; Md. S. Roni; Kara G. Cafferty; Sandra D. Eksioglu

    2014-06-01

    In this paper we propose a model to design the supply chain for densified biomass. Rail is typically used for longhaul, high-volume shipment of densified biomass. This is the reason why a hub-and-spoke network structure is used to model this supply chain. The model is formulated as a multi-objective, mixed-integer programing problem under economic, environmental, and social criteria. The goal is to identify the feasibility of meeting the Renewable Fuel Standard (RFS) by using biomass for production of cellulosic ethanol. The focus is not just on the costs associated with meeting these standards, but also exploring the social and environmental benefits that biomass production and processing offers by creating new jobs and reducing greenhouse gas (GHG) emissions. We develop an augmented ?-constraint method to find the exact Pareto solution to this optimization problem. We develop a case study using data from the Mid-West. The model identifies the number, capacity and location of biorefineries needed to make use of the biomass available in the region. The model estimates the delivery cost of cellulosic ethanol under different scenario, the number new jobs created and the GHG emission reductions in the supply chain.

  11. Joint Center for Artificial Photosynthesis (JCAP): DOE's Solar Fuels Energy Innovation Hub (2011 EFRC Summit)

    ScienceCinema (OSTI)

    Lewis, Nate (Director, Joint Center for Artificial Photosynthesis and Professor at Caltech)

    2012-03-14

    The Joint Center for Artificial Photosynthesis (JCAP) is a DOE Energy Innovation Hub focused on fuels from sunlight. JCAP's Director, Nate Lewis, spoke at the 2011 EFRC Summit about what JCAP is and how it is partnering with the EFRC community to accelerate the progress towards new solar fuels. The 2011 EFRC Summit and Forum brought together the EFRC community and science and policy leaders from universities, national laboratories, industry and government to discuss "Science for our Nation's Energy Future." In August 2009, the Office of Science established 46 Energy Frontier Research Centers. The EFRCs are collaborative research efforts intended to accelerate high-risk, high-reward fundamental research, the scientific basis for transformative energy technologies of the future. These Centers involve universities, national laboratories, nonprofit organizations, and for-profit firms, singly or in partnerships, selected by scientific peer review. They are funded at $2 to $5 million per year for a total planned DOE commitment of $777 million over the initial five-year award period, pending Congressional appropriations. These integrated, multi-investigator Centers are conducting fundamental research focusing on one or more of several ?grand challenges? and use-inspired ?basic research needs? recently identified in major strategic planning efforts by the scientific community. The purpose of the EFRCs is to integrate the talents and expertise of leading scientists in a setting designed to accelerate research that transforms the future of energy and the environment.

  12. STARS no star on Kauai

    SciTech Connect (OSTI)

    Jones, M.

    1993-04-01

    The island of Kuai, home to the Pacific Missile Range Facility, is preparing for the first of a series of Star Wars rocket launches expected to begin early this year. The Strategic Defense Initiative plans 40 launches of the Stategic Target System (STARS) over a 10-year period. The focus of the tests appears to be weapons and sensors designed to combat multiple-warhead ICBMs, which will be banned under the START II Treaty that was signed in January. The focus of this article is to express the dubious value of testing the STARS at a time when their application will not be an anticipated problem.

  13. Star Power

    ScienceCinema (OSTI)

    None

    2014-11-18

    The U.S. Department of Energy's Princeton Plasma Physics Laboratory has released ''Star Power,'' a new informational video that uses dramatic and beautiful images and thought-provoking interviews to highlight the importance of the Laboratory's research into magnetic fusion.

  14. Star Power

    SciTech Connect (OSTI)

    2014-10-17

    The U.S. Department of Energy's Princeton Plasma Physics Laboratory has released ''Star Power,'' a new informational video that uses dramatic and beautiful images and thought-provoking interviews to highlight the importance of the Laboratory's research into magnetic fusion.

  15. Preparation of Nucleic Acid Libraries for Personalized Sequencing Systems Using an Integrated Microfluidic Hub Technology (Seventh Annual Sequencing, Finishing, Analysis in the Future (SFAF) Meeting 2012)

    ScienceCinema (OSTI)

    Patel, Kamlesh D [Ken]; SNL,

    2013-01-25

    Kamlesh (Ken) Patel from Sandia National Laboratories (Livermore, California) presents "Preparation of Nucleic Acid Libraries for Personalized Sequencing Systems Using an Integrated Microfluidic Hub Technology " at the 7th Annual Sequencing, Finishing, Analysis in the Future (SFAF) Meeting held in June, 2012 in Santa Fe, NM.

  16. Analytical Formulation for Sizing and Estimating the Dimensions and Weight of Wind Turbine Hub and Drivetrain Components

    SciTech Connect (OSTI)

    Guo, Y.; Parsons, T.; King, R.; Dykes, K.; Veers, P.

    2015-06-09

    This report summarizes the theory, verification, and validation of a new sizing tool for wind turbine drivetrain components, the Drivetrain Systems Engineering (DriveSE) tool. DriveSE calculates the dimensions and mass properties of the hub, main shaft, main bearing(s), gearbox, bedplate, transformer if up-tower, and yaw system. The level of fi¬ delity for each component varies depending on whether semiempirical parametric or physics-based models are used. The physics-based models have internal iteration schemes based on system constraints and design criteria. Every model is validated against available industry data or finite-element analysis. The verification and validation results show that the models reasonably capture primary drivers for the sizing and design of major drivetrain components.

  17. Social networks for lonely objects

    E-Print Network [OSTI]

    Kestner, John Anthony

    2010-01-01

    Visions of ubiquitous computing describe a network of devices that quietly supports human goals, but this may also add complexity to an already frustrating relationship between humans and their electronic objects. As we ...

  18. Nucleosynthesis in barium stars

    E-Print Network [OSTI]

    Trimble, V; Trimble, V

    1984-01-01

    problem of apparent nucleosynthesis in barium stars, thoughSE24 9JF. Astronomy Nucleosynthesis in barium stars fromopportunity to see that nucleosynthesis really is taking

  19. Star Formation triggered by cloud-cloud collisions

    E-Print Network [OSTI]

    Balfour, S K; Hubber, D A; Jaffa, S E

    2015-01-01

    We present the results of SPH simulations in which two clouds, each having mass $M_{_{\\rm{o}}}\\!=\\!500\\,{\\rm M}_{_\\odot}$ and radius $R_{_{\\rm{o}}}\\!=\\!2\\,{\\rm pc}$, collide head-on at relative velocities of $\\Delta v_{_{\\rm{o}}} =2.4,\\;2.8,\\;3.2,\\;3.6\\;{\\rm and}\\;4.0\\,{\\rm km}\\,{\\rm s}^{-1}$. There is a clear trend with increasing $\\Delta v_{_{\\rm{o}}}$. At low $\\Delta v_{_{\\rm{o}}}$, star formation starts later, and the shock-compressed layer breaks up into an array of predominantly radial filaments; stars condense out of these filaments and fall, together with residual gas, towards the centre of the layer, to form a single large-$N$ cluster, which then evolves by competitive accretion, producing one or two very massive protostars and a diaspora of ejected (mainly low-mass) protostars; the pattern of filaments is reminiscent of the hub and spokes systems identified recently by observers. At high $\\Delta v_{_{\\rm{o}}}$, star formation occurs sooner and the shock-compressed layer breaks up into a network of f...

  20. When Stars Blow Up What Stars Explode?

    E-Print Network [OSTI]

    Walter, Frederick M.

    When Stars Blow Up #12;What Stars Explode? ·Cataclysmic variables ·Novae ·Supernovae #12;Cataclysmic Variables ·Binary star systems incorporating a white dwarf ·Outbursts due to disk instabilities the temperature reaches a few MK, fusion begins ·Degenerate fusion is a runaway. ·All the H fuses to He

  1. Evaluation of WRF predicted near hub-height winds and ramp events over a Pacific Northwest site with complex terrain

    SciTech Connect (OSTI)

    Yang, Qing; Berg, Larry K.; Pekour, Mikhail S.; Fast, Jerome D.; Newsom, Rob K.; Stoelinga, Mark; Finley, Cathy

    2013-08-16

    The WRF model version 3.3 is used to simulate near hub-height winds and power ramps utilizing three commonly used planetary boundary-layer (PBL) schemes: Mellor-Yamada-Janji? (MYJ), University of Washington (UW), and Yonsei University (YSU). The predicted winds have small mean biases compared with observations. Power ramps and step changes (changes within an hour) consistently show that the UW scheme performed better in predicting up ramps under stable conditions with higher prediction accuracy and capture rates. Both YSU and UW scheme show good performance predicting up- and down- ramps under unstable conditions with YSU being slightly better for ramp durations longer than an hour. MYJ is the most successful simulating down-ramps under stable conditions. The high wind speed and large shear associated with low-level jets are frequently associated with power ramps, and the biases in predicted low-level jet explain some of the shown differences in ramp predictions among different PBL schemes. Low-level jets were observed as low as ~200 m in altitude over the Columbia Basin Wind Energy Study (CBWES) site, located in an area of complex terrain. The shear, low-level peak wind speeds, as well as the height of maximum wind speed are not well predicted. Model simulations with 3 PBL schemes show the largest variability among them under stable conditions.

  2. Star-ND (Multi-Dimensional Star-Identification) 

    E-Print Network [OSTI]

    Spratling, Benjamin

    2012-07-16

    of iterations of the run-time algorithm. The associated algorithms, star pattern parameters, and database preparation are collectively referred to as Multi-dimensional Star-Identification (Star-ND). The star pattern parameters developed may also be extended...

  3. The Biological and Molecular Analysis of a Tick-Encoded Serine Protease Inhibitor (S6) and its Role in the Feeding Cycle of the Lone Star Tick, Amblyomma americanum (L) (Acari: ixodidae) 

    E-Print Network [OSTI]

    Chalaire, Katelyn Cox

    2011-10-21

    silencing of S6 and S6/S17 mRNA was achieved, post-transcriptional gene knockdown had no effect on tick feeding efficiency or fecundity. These findings have been discussed in regards to the development of a vaccine against A. americanum and necessary future...

  4. Critical Materials Hub

    Broader source: Energy.gov [DOE]

    Critical materials, including some rare earth elements that possess unique magnetic, catalytic, and luminescent properties, are key resources needed to manufacture products for the clean energy economy. These materials are so critical to the technologies that enable wind turbines, solar panels, electric vehicles, and energy-efficient lighting that DOE's 2010 and 2011 Critical Materials Strategy reported that supply challenges for five rare earth metals—dysprosium, neodymium, terbium, europium, and yttrium—could affect clean energy technology deployment in the coming years.1, 2

  5. Hubs | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    research to produce fuels directly from sunlight (the Joint Center for Artificial Photosynthesis) to improving battery technology for transportation and the grid (the Joint...

  6. SEAB Hubs+ Report

    Broader source: Energy.gov [DOE]

    This report presents the findings and recommendations for the Secretary of Energy Advisory Board (SEAB) Task Force to Support Evaluation of the new Funding Constructs for Energy Research and...

  7. DOE Energy Innovation Hubs

    Office of Science (SC) Website

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantityBonneville Power AdministrationRobust,Field-effectWorkingLosThe 26thI D- 6 0 4Contract Management Thomas Jefferson SiteResearch

  8. Energy Efficient Buildings Hub

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on Delicious Rank EERE:FinancingPetroleum12, 2015 Infographic courtesyEducation Data JamDepartment ofEERE

  9. Metal-Poor Stars

    E-Print Network [OSTI]

    Anna Frebel

    2008-02-13

    The abundance patterns of metal-poor stars provide us a wealth of chemical information about various stages of the chemical evolution of the Galaxy. In particular, these stars allow us to study the formation and evolution of the elements and the involved nucleosynthesis processes. This knowledge is invaluable for our understanding of the cosmic chemical evolution and the onset of star- and galaxy formation. Metal-poor stars are the local equivalent of the high-redshift Universe, and offer crucial observational constraints on the nature of the first stars. This review presents the history of the first discoveries of metal-poor stars that laid the foundation to this field. Observed abundance trends at the lowest metallicities are described, as well as particular classes of metal-poor stars such as r-process and C-rich stars. Scenarios on the origins of the abundances of metal-poor stars and the application of large samples of metal-poor stars to cosmological questions are discussed.

  10. EXTENDED SCHMIDT LAW: ROLE OF EXISTING STARS IN CURRENT STAR...

    Office of Scientific and Technical Information (OSTI)

    We propose an 'extended Schmidt law' with explicit dependence of the star formation efficiency (SFE SFRMsub gas) on the stellar mass surface density (Sigmasub star). This...

  11. The neutron star mass distribution

    E-Print Network [OSTI]

    Kiziltan, B; Kottas, A; De Yoreo, M; Thorsett, SE

    2013-01-01

    Science Library, Vol. 326, Neutron Stars 1 : Equation ofBlack holes, white dwarfs, and neutron stars: The physics ofPhys. Rev. , 55, 364 The Neutron Star Mass Distribution van

  12. Neutrostriction in Neutron stars

    E-Print Network [OSTI]

    V. K. Ignatovich

    2006-06-29

    It is demonstrated that not only gravity, but also neutrostriction forces due to optical potential created by coherent elastic neutron-neutron scattering can hold a neutron star together. The latter forces can be stronger than gravitational ones. The effect of these forces on mass, radius and structure of the neutron star is estimated.

  13. Dark Stars: A Review

    E-Print Network [OSTI]

    Katherine Freese; Tanja Rindler-Daller; Douglas Spolyar; Monica Valluri

    2015-01-10

    Dark Stars (DS) are stellar objects made (almost entirely) of ordinary atomic material but powered by the heat from Dark Matter (DM) annihilation (rather than by fusion). Weakly Interacting Massive Particles (WIMPs), among the best candidates for DM, can be their own antimatter and can accumulate inside the star, with their annihilation products thermalizing with and heating the DS. The resulting DSs are in hydrostatic and thermal equilibrium. The first phase of stellar evolution in the history of the Universe may have been dark stars. Though DM constituted only $star, this amount was sufficient to power the star for millions to billions of years. Depending on their DM environment, early DSs can become very massive ($>10^6 M_\\odot$), very bright ($>10^9 L_\\odot$), and potentially detectable with the James Webb Space Telescope (JWST). Once the DM runs out and the dark star dies, it may collapse to a black hole; thus DSs can provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The current review briefly discusses DSs existing today but focuses on the early generation of dark stars.

  14. Home Performance with ENERGY STAR

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    that support expanded participation in the Home Performance with ENERGY STAR Program. Our Vision Home Performance with ENERGY STAR is accessible to all American households....

  15. Neutron Stars and Fractal Dimensionality

    E-Print Network [OSTI]

    Burra G. Sidharth

    2008-05-06

    We argue that the material inside Neutron stars behaves anomalously with fractal statistics and that in principle, we could induce mini Neutron stars, with the release of energy.

  16. The Department of Architectural Engineering is providing the technical leadership on the recently awarded Department of Energy Innovation Hub for Energy Efficient Buildings. This initiative was led on behalf of the

    E-Print Network [OSTI]

    Yener, Aylin

    awarded Department of Energy Innovation Hub for Energy Efficient Buildings. This initiative was led the building industry and radically improve the energy efficiency of building systems." See below, the Department should be playing a pivotal role in the development of the next generation of energy

  17. SmartGrid: Quarterly Data Summaries from the Data Hub and SmartGrid Project Information (from OpenEI and SmartGrid.gov)

    DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

    Both OpenEI and SmartGrid.gov are DOE portals to a wealth of information about the federal initiatives that support the development of the technologies, policies and projects transforming the electric power industry. Projects funded through the U.S. Recovery Act are organized by type and pinned to an interactive map at http://en.openei.org/wiki/Gateway:Smart_Grid. Each project title links to more detailed information. The Quarterly Data Summaries from the Data Hub at SmartGrid.gov are also available on OpenEI at http://en.openei.org/datasets/node/928. In addition, the SmartGrid Information Center contains documents and reports that can be searched or browsed. Smart Grid Resources introduces international SmartGrid programs and sites, while OpenEI encourages users to add SmartGrid information to the repository.

  18. Rising Stars 2015 3 Rising Stars

    E-Print Network [OSTI]

    Kastner, Marc A.

    such an esteemed group of women in computer science and electrical engineering. The Rising Stars program gives you part!" --Cynthia Barnhart Chancellor Ford Professor of Engineering Massachusetts Institute women in computer science and electrical engineering globally.You will help lead research, education

  19. Planets around active stars

    E-Print Network [OSTI]

    J. Setiawan; P. Weise; Th. Henning; A. P. Hatzes; L. Pasquini; L. da Silva; L. Girardi; O. von der Luhe; M. P. Dollinger; A. Weiss; K. Biazzo

    2007-04-17

    We present the results of radial velocity measurements of two samples of active stars. The first sample contains field G and K giants across the Red Giant Branch, whereas the second sample consists of nearby young stars (d 1999 - 2002) and continued since 2003 at 2.2 m MPG/ESO telescope. We observed stellar radial velocity variations which originate either from the stellar activity or the presence of stellar/substellar companions. By means of a bisector technique we are able to distinguish the sources of the radial velocity variation. Among them we found few candidates of planetary companions, both of young stars and G-K giants sample.

  20. Hypernuclear Physics for Neutron Stars

    E-Print Network [OSTI]

    Jurgen Schaffner-Bielich

    2008-01-24

    The role of hypernuclear physics for the physics of neutron stars is delineated. Hypernuclear potentials in dense matter control the hyperon composition of dense neutron star matter. The three-body interactions of nucleons and hyperons determine the stiffness of the neutron star equation of state and thereby the maximum neutron star mass. Two-body hyperon-nucleon and hyperon-hyperon interactions give rise to hyperon pairing which exponentially suppresses cooling of neutron stars via the direct hyperon URCA processes. Non-mesonic weak reactions with hyperons in dense neutron star matter govern the gravitational wave emissions due to the r-mode instability of rotating neutron stars.

  1. Masers and star formation

    E-Print Network [OSTI]

    Vincent L. Fish

    2007-04-02

    Recent observational and theoretical advances concerning astronomical masers in star forming regions are reviewed. Major masing species are considered individually and in combination. Key results are summarized with emphasis on present science and future prospects.

  2. Notes on Star Formation

    E-Print Network [OSTI]

    Krumholz, Mark R

    2015-01-01

    This book provides an introduction to the field of star formation at a level suitable for graduate students or advanced undergraduates in astronomy or physics. The structure of the book is as follows. The first two chapters begin with a discussion of observational techniques, and the basic phenomenology they reveal. The goal is to familiarize students with the basic techniques that will be used throughout, and to provide a common vocabulary for the rest of the book. The next five chapters provide a similar review of the basic physical processes that are important for star formation. Again, the goal is to provide a basis for what follows. The remaining chapters discuss star formation over a variety of scales, starting with the galactic scale and working down to the scales of individual stars and their disks. The book concludes with a brief discussion of the clearing of disks and the transition to planet formation. The book includes five problem sets, complete with solutions.

  3. ENERGY STAR Product Rebates

    Broader source: Energy.gov [DOE]

    When mail-in rebates are active, as a general rule, all appliances must be ENERGY STAR rated; however, additional requirements may apply to different types of appliances. Rebate requests must...

  4. Holographic Neutron Stars

    E-Print Network [OSTI]

    Jan de Boer; Kyriakos Papadodimas; Erik Verlinde

    2009-07-23

    We construct in the context of the AdS/CFT correspondence degenerate composite operators in the conformal field theory that are holographically dual to degenerate stars in anti de Sitter space. We calculate the effect of the gravitational back-reaction using the Tolman-Oppenheimer-Volkoff equations, and determine the "Chandrasekhar limit" beyond which the star undergoes gravitational collapse towards a black hole.

  5. STAR Facility Tritium Accountancy

    SciTech Connect (OSTI)

    R. J. Pawelko; J. P. Sharpe; B. J. Denny

    2007-09-01

    The Safety and Tritium Applied Research (STAR) facility has been established to provide a laboratory infrastructure for the fusion community to study tritium science associated with the development of safe fusion energy and other technologies. STAR is a radiological facility with an administrative total tritium inventory limit of 1.5g (14,429 Ci) [1]. Research studies with moderate tritium quantities and various radionuclides are performed in STAR. Successful operation of the STAR facility requires the ability to receive, inventory, store, dispense tritium to experiments, and to dispose of tritiated waste while accurately monitoring the tritium inventory in the facility. This paper describes tritium accountancy in the STAR facility. A primary accountancy instrument is the tritium Storage and Assay System (SAS): a system designed to receive, assay, store, and dispense tritium to experiments. Presented are the methods used to calibrate and operate the SAS. Accountancy processes utilizing the Tritium Cleanup System (TCS), and the Stack Tritium Monitoring System (STMS) are also discussed. Also presented are the equations used to quantify the amount of tritium being received into the facility, transferred to experiments, and removed from the facility. Finally, the STAR tritium accountability database is discussed.

  6. STAR facility tritium accountancy

    SciTech Connect (OSTI)

    Pawelko, R. J.; Sharpe, J. P.; Denny, B. J.

    2008-07-15

    The Safety and Tritium Applied Research (STAR) facility has been established to provide a laboratory infrastructure for the fusion community to study tritium science associated with the development of safe fusion energy and other technologies. STAR is a radiological facility with an administrative total tritium inventory limit of 1.5 g (14,429 Ci) [1]. Research studies with moderate tritium quantities and various radionuclides are performed in STAR. Successful operation of the STAR facility requires the ability to receive, inventory, store, dispense tritium to experiments, and to dispose of tritiated waste while accurately monitoring the tritium inventory in the facility. This paper describes tritium accountancy in the STAR facility. A primary accountancy instrument is the tritium Storage and Assay System (SAS): a system designed to receive, assay, store, and dispense tritium to experiments. Presented are the methods used to calibrate and operate the SAS. Accountancy processes utilizing the Tritium Cleanup System (TCS), and the Stack Tritium Monitoring System (STMS) are also discussed. Also presented are the equations used to quantify the amount of tritium being received into the facility, transferred to experiments, and removed from the facility. Finally, the STAR tritium accountability database is discussed. (authors)

  7. I-Love relation for incompressible stars and realistic stars

    E-Print Network [OSTI]

    T. K. Chan; Atma P. O. Chan; P. T. Leung

    2014-11-26

    In spite of the diversity in the equations of state of nuclear matter, the recently discovered I-Love-Q relations [Yagi and Yunes, Science {\\bf 341}, 365 (2013)], which relate the moment of inertia, tidal Love number (deformability) and the spin-induced quadrupole moment of compact stars, hold for various kinds of realistic neutron stars and quark stars. While the physical origin of such universality is still a current issue, the observation that the I-Love-Q relations of incompressible stars can well approximate those of realistic compact stars hints at a new direction to approach the problem. In this paper, by establishing recursive post-Minkowskian expansion for the moment of inertia and the tidal deformability of incompressible stars, we analytically derive the I-Love relation for incompressible stars and show that the so obtained formula can be used to accurately predict the behavior of realistic compact stars from the Newtonian limit to the maximum mass limit.

  8. ENERGY STAR Webinar: How to Apply for the ENERGY STAR

    Broader source: Energy.gov [DOE]

    The U.S. Environmental Protection Agency (EPA) is hosting a webinar on how to apply for ENERGY STAR certification in Portfolio Manager. Understand the value of the ENERGY STAR certification, see...

  9. Pre-main sequence stars, emission stars and recent star formation in the Cygnus Region

    E-Print Network [OSTI]

    Bhavya B; Blesson Mathew; Annapurni Subramaniam

    2008-04-09

    The recent star formation history in the Cygnus region is studied using 5 clusters (IC 4996, NGC 6910, Berkeley 87, Biurakan 2 and Berkeley 86). The optical data from the literature are combined with the 2MASS data to identify the pre-main sequence (pre-MS) stars as stars with near IR excess. We identified 93 pre-MS stars and 9 stars with H$_\\alpha$ emission spectra. The identified pre-MS stars are used to estimate the turn-on age of the clusters. The duration of star formation was estimated as the difference between the turn-on and the turn-off age. We find that, NGC 6910 and IC 4996 have been forming stars continuously for the last 6 -- 7 Myr, Berkeley 86 and Biurakan 2 for 5 Myr and Berkeley 87 for the last 2 Myr. This indicates that the Cygnus region has been actively forming stars for the last 7 Myr, depending on the location. 9 emission line stars were identified in 4 clusters, using slit-less spectra (Be 87 - 4 stars; Be 86 - 2 stars, NGC 6910 - 2 stars and IC 4996 - 1 star). The individual spectra were obtained and analysed to estimate stellar as well as disk properties. All the emission stars are in the MS, well below the turn-off, in the core hydrogen burning phase. These stars are likely to be Classical Be (CBe) stars. Thus CBe phenomenon can be found in very young MS stars which are just a few (2 -- 7) Myrs old. This is an indication that CBe phenomenon need not be an evolutionary effect.

  10. Cool Stars in Hot Places

    E-Print Network [OSTI]

    S. T. Megeath; E. Gaidos; J. J. Hester; F. C. Adams; J. Bally; J. -E. Lee; S. Wolk

    2007-04-08

    During the last three decades, evidence has mounted that star and planet formation is not an isolated process, but is influenced by current and previous generations of stars. Although cool stars form in a range of environments, from isolated globules to rich embedded clusters, the influences of other stars on cool star and planet formation may be most significant in embedded clusters, where hundreds to thousands of cool stars form in close proximity to OB stars. At the cool stars 14 meeting, a splinter session was convened to discuss the role of environment in the formation of cool stars and planetary systems; with an emphasis on the ``hot'' environment found in rich clusters. We review here the basic results, ideas and questions presented at the session. We have organized this contribution into five basic questions: what is the typical environment of cool star formation, what role do hot star play in cool star formation, what role does environment play in planet formation, what is the role of hot star winds and supernovae, and what was the formation environment of the Sun? The intention is to review progress made in addressing each question, and to underscore areas of agreement and contention.

  11. Synthetic guide star generation

    DOE Patents [OSTI]

    Payne, Stephen A. (Castro Valley, CA) [Castro Valley, CA; Page, Ralph H. (Castro Valley, CA) [Castro Valley, CA; Ebbers, Christopher A. (Livermore, CA) [Livermore, CA; Beach, Raymond J. (Livermore, CA) [Livermore, CA

    2008-06-10

    A system for assisting in observing a celestial object and providing synthetic guide star generation. A lasing system provides radiation at a frequency at or near 938 nm and radiation at a frequency at or near 1583 nm. The lasing system includes a fiber laser operating between 880 nm and 960 nm and a fiber laser operating between 1524 nm and 1650 nm. A frequency-conversion system mixes the radiation and generates light at a frequency at or near 589 nm. A system directs the light at a frequency at or near 589 nm toward the celestial object and provides synthetic guide star generation.

  12. A Star on Earth

    ScienceCinema (OSTI)

    Prager, Stewart; Zwicker, Andrew; Hammet, Greg; Tresemer, Kelsey; Diallo, Ahmed

    2014-06-06

    At the Energy Department's Princeton Plasma Physics Lab, scientists are trying to accomplish what was once considered the realm of science fiction: create a star on Earth. The National Spherical Torus Experiment (NSTX) is a magnetic fusion device that is used to study the physics principles of spherically shaped plasmas -- hot ionized gases in which, under the right conditions, nuclear fusion will occur. Fusion is the energy source of the sun and all of the stars. Not just limited to theoretical work, the NSTX is enabling cutting-edge research to develop fusion as a future energy source.

  13. A Star on Earth

    SciTech Connect (OSTI)

    Prager, Stewart; Zwicker, Andrew; Hammet, Greg; Tresemer, Kelsey; Diallo, Ahmed

    2014-03-05

    At the Energy Department's Princeton Plasma Physics Lab, scientists are trying to accomplish what was once considered the realm of science fiction: create a star on Earth. The National Spherical Torus Experiment (NSTX) is a magnetic fusion device that is used to study the physics principles of spherically shaped plasmas -- hot ionized gases in which, under the right conditions, nuclear fusion will occur. Fusion is the energy source of the sun and all of the stars. Not just limited to theoretical work, the NSTX is enabling cutting-edge research to develop fusion as a future energy source.

  14. Synthetic guide star generation

    SciTech Connect (OSTI)

    Payne, Stephen A.; Page, Ralph H.; Ebbers, Christopher A.; Beach, Raymond J.

    2004-03-09

    A system for assisting in observing a celestial object and providing synthetic guide star generation. A lasing system provides radiation at a frequency at or near 938 nm and radiation at a frequency at or near 1583 nm. The lasing system includes a fiber laser operating between 880 nm and 960 nm and a fiber laser operating between 1524 nm and 1650 nm. A frequency-conversion system mixes the radiation and generates light at a frequency at or near 589 nm. A system directs the light at a frequency at or near 589 nm toward the celestial object and provides synthetic guide star generation.

  15. The Austin Energy Star Program 

    E-Print Network [OSTI]

    Seiter, D. L.

    1988-01-01

    The Austin Energy Star Program is an Austin-specific energy rating system implemented in July, 1985. Since the first builders joined the program, Energy Star has gone through significant improvements vithout changing the fundamental marketing theme...

  16. Neutron stars - cooling and transport

    E-Print Network [OSTI]

    Potekhin, A Y; Page, Dany

    2015-01-01

    Observations of thermal radiation from neutron stars can potentially provide information about the states of supranuclear matter in the interiors of these stars with the aid of the theory of neutron-star thermal evolution. We review the basics of this theory for isolated neutron stars with strong magnetic fields, including most relevant thermodynamic and kinetic properties in the stellar core, crust, and blanketing envelopes.

  17. Radial stability in stratified stars

    E-Print Network [OSTI]

    Pereira, Jonas P

    2015-01-01

    We formulate within a generalized distributional approach the treatment of the stability against radial perturbations for both neutral and charged stratified stars in Newtonian and Einstein's gravity. We obtain from this approach the boundary conditions connecting two any phases within a star and underline its relevance for realistic models of compact stars with phase transitions, owing to the modification of the star's set of eigenmodes with respect to the continuous case.

  18. Radial stability in stratified stars

    E-Print Network [OSTI]

    Jonas P. Pereira; Jorge A. Rueda

    2015-01-12

    We formulate within a generalized distributional approach the treatment of the stability against radial perturbations for both neutral and charged stratified stars in Newtonian and Einstein's gravity. We obtain from this approach the boundary conditions connecting two any phases within a star and underline its relevance for realistic models of compact stars with phase transitions, owing to the modification of the star's set of eigenmodes with respect to the continuous case.

  19. High-gravity central stars

    E-Print Network [OSTI]

    Thomas Rauch

    2006-07-11

    NLTE spectral analyses of high-gravity central stars by means of state-of-the-art model atmosphere techniques provide information about the precursor AGB stars. The hydrogen-deficient post-AGB stars allow investigations on the intershell matter which is apparently exhibited at the stellar surface. We summarize recent results from imaging, spectroscopy, and spectropolarimetry.

  20. Spectral Modeling Hot Star Winds

    E-Print Network [OSTI]

    Cohen, David

    Spectral Modeling of X-Rays from Hot Star Winds Emma Wollman Advisor: David Cohen #12;Hot Stars ·· Short-livedShort-lived (~ 1-10 million yrs)(~ 1-10 million yrs) #12;Stellar Winds · Net momentum · More luminosity !"stronger wind · Mass-loss rate determines the fate of the star #12;X-ray Production

  1. Massive Hybrid Stars with Strangeness

    E-Print Network [OSTI]

    Tatsuyuki Takatsuka; Tetsuo Hatsuda; Kota Masuda

    2014-02-19

    How massive the hybrid stars could be is discussed by a "3-window model" proposed from a new strategy to construct the equation of state with hadron-quark transition. It is found that hybrid stars have a strong potentiality to generate a large mass compatible with two-solar-mass neutron star observations.

  2. Energy generation in stars

    E-Print Network [OSTI]

    B. V. Vasiliev

    2001-10-29

    It is a current opinion that thermonuclear fusion is the main source of the star activity. It is shown below that this source is not unique. There is another electrostatic mechanism of the energy generation which accompanies thermonuclear fusion. Probably, this approach can solve the solar neutrino problem.

  3. Isolating Triggered Star Formation

    E-Print Network [OSTI]

    Elizabeth J. Barton; Jacob A. Arnold; Andrew R. Zentner; James S. Bullock; Risa H. Wechsler

    2007-08-21

    Galaxy pairs provide a potentially powerful means of studying triggered star formation from galaxy interactions. We use a large cosmological N-body simulation coupled with a well-tested semi-analytic substructure model to demonstrate that the majority of galaxies in close pairs reside within cluster or group-size halos and therefore represent a biased population, poorly suited for direct comparison to ``field'' galaxies. Thus, the frequent observation that some types of galaxies in pairs have redder colors than ``field'' galaxies is primarily a selection effect. We select galaxy pairs that are isolated in their dark matter halos with respect to other massive subhalos (N=2 halos) and a control sample of isolated galaxies (N=1 halos) for comparison. We then apply these selection criteria to a volume-limited subset of the 2dF Galaxy Redshift Survey with M_Bj ~ 5 above their average past value, while only 10% of isolated galaxies in the control sample show this level of enhancement. Thus, 14% (20 %) of the galaxies in these close pairs show clear triggered star formation. The isolation criteria we develop provide a means to constrain star formation and feedback prescriptions in hydrodynamic simulations and a very general method of understanding the importance of triggered star formation in a cosmological context. (Abridged.)

  4. Magnetic fields in massive stars

    E-Print Network [OSTI]

    S. Hubrig; M. Schoeller; M. Briquet; M. A. Pogodin; R. V. Yudin; J. F. Gonzalez; T. Morel; P. De Cat; R. Ignace; P. North; G. Mathys; G. J. Peters

    2007-12-02

    We review the recent discoveries of magnetic fields in different types of massive stars and briefly discuss strategies for spectropolarimetric observations to be carried out in the future.

  5. Magnetic fields in massive stars

    E-Print Network [OSTI]

    Hubrig, S; Briquet, M; Pogodin, M A; Yudin, R V; González, J F; Morel, T; De Cat, P; Ignace, R; North, P; Mathys, G; Peters, G J

    2007-01-01

    We review the recent discoveries of magnetic fields in different types of massive stars and briefly discuss strategies for spectropolarimetric observations to be carried out in the future.

  6. Excavation of the first stars

    E-Print Network [OSTI]

    Toshikazu Shigeyama; Takuji Tsujimoto; Yuzuru Yoshii

    2003-02-17

    The external pollution of the first stars in the Galaxy is investigated. The first stars were born in clouds composed of the pristine gas without heavy elements. These stars accreted gas polluted with heavy elements while they still remained in the cloud. As a result, it is found that they exhibit a distribution with respect to the surface metallicity. We have derived the actual form of this distribution function. This metallicity distribution function strongly suggests that the recently discovered most metal-deficient star HE0107-5240 with [Fe/H]=-5.3 was born as a metal-free star and accreted gas polluted with heavy elements. Thus the heavy elements such as Fe in HE0107-5240 must have been supplied from supernovae of later generations exploding inside the cloud in which the star had been formed. The elemental abundance pattern on the surface of stars suffering from such an external pollution should not be diverse but exhibit the average pattern of numerous supernovae. Future observations for a number of metal-deficient stars with [Fe/H]<-5 will be able to prove or disprove this external pollution scenario. Other possibilities to produce a star with this metallicity are also discussed.

  7. Creating a Star on Earth

    Office of Energy Efficiency and Renewable Energy (EERE)

    At the Energy Department's Princeton Plasma Physics Lab, scientists are trying to accomplish what was once considered the realm of science fiction: creating a star on Earth.

  8. Cavitation from bulk viscosity in neutron stars and quark stars

    E-Print Network [OSTI]

    Jes Madsen

    2009-09-30

    The bulk viscosity in quark matter is sufficiently high to reduce the effective pressure below the corresponding vapor pressure during density perturbations in neutron stars and strange stars. This leads to mechanical instability where the quark matter breaks apart into fragments comparable to cavitation scenarios discussed for ultra-relativistic heavy-ion collisions. Similar phenomena may take place in kaon-condensed stellar cores. Possible applications to compact star phenomenology include a new mechanism for damping oscillations and instabilities, triggering of phase transitions, changes in gravitational wave signatures of binary star inspiral, and astrophysical formation of strangelets. At a more fundamental level it points to the possible inadequacy of a hydrodynamical treatment of these processes in compact stars.

  9. Cavitation from bulk viscosity in neutron stars and strange stars

    E-Print Network [OSTI]

    Madsen, Jes

    2009-01-01

    The bulk viscosity in quark matter is sufficiently high to reduce the effective pressure below the corresponding vapor pressure during density perturbations in neutron stars and strange stars. This leads to mechanical instability where the quark matter breaks apart into fragments comparable to cavitation scenarios discussed for ultra-relativistic heavy-ion collisions. Similar phenomena may take place in kaon-condensed stellar cores. Possible applications to compact star phenomenology include a new mechanism for damping oscillations and instabilities, triggering of phase transitions, changes in gravitational wave signatures of binary star inspiral, and astrophysical formation of strangelets. At a more fundamental level it points to the possible inadequacy of a hydrodynamical treatment of these processes in compact stars.

  10. Signed Quality Assurance Hub Memo

    Office of Environmental Management (EM)

    SECCTRITY PROGRAM ENVIRONMENTAL MANAGEMENT SUBJECT: Office of Environmental Management Quality Assurance Performance Assessment, Commitment, and Corrective Action Management...

  11. Becoming a Global Intellectual Hub

    E-Print Network [OSTI]

    Calgary, University of

    Highstrategicvisiondocument, published2011 Cover: Designed by renowned Spanish architect Santiago Calatrava, Calgary's Peace Bridge accommodates some 6000 pedestrians and cyclists who cross the Bow River each day to access the city's downtown

  12. High Impact Technology Hub- Results

    Broader source: Energy.gov [DOE]

    Highlights, outcomes and activities to support the adoption of High Impact Technologies.  Technology Highlights preview early results from current technology demonstrations.  Case Studies overview...

  13. Star Products for Relativistic Quantum Mechanics

    E-Print Network [OSTI]

    P. Henselder

    2007-05-24

    The star product formalism has proved to be an alternative formulation for nonrelativistic quantum mechanics. We want introduce here a covariant star product in order to extend the star product formalism to relativistic quantum mechanics in the proper time formulation.

  14. Physics of Neutron Star Crusts

    E-Print Network [OSTI]

    N. Chamel; P. Haensel

    2008-12-20

    The physics of neutron star crusts is vast, involving many different research fields, from nuclear and condensed matter physics to general relativity. This review summarizes the progress, which has been achieved over the last few years, in modeling neutron star crusts, both at the microscopic and macroscopic levels. The confrontation of these theoretical models with observations is also briefly discussed.

  15. Thermal Evolution of Strange Stars

    E-Print Network [OSTI]

    Zhou Xia; Wang Lingzhi; Zhou Aizhi

    2007-09-03

    We investigated the thermal evolution of rotating strange stars with the deconfinement heating due to magnetic braking. We consider the stars consisting of either normal quark matter or color-flavor-locked phase. Combining deconfinement heating with magnetic field decay, we find that the thermal evolution curves are identical to pulsar data.

  16. Verifying the ENERGY STAR® Certification Application

    Broader source: Energy.gov [DOE]

    Do you verify commercial building applications for ENERGY STAR certification? This webinar, based on the ENERGY STAR Guide for Licensed Professionals, covers the role of the licensed professional,...

  17. EPA ENERGY STAR Webcast: Value of ENERGY STAR Certification

    Broader source: Energy.gov [DOE]

    For thousands of organizations, ENERGY STAR is the simple choice for saving money and demonstrating environmental leadership to the public. Lower energy costs aren't the only financial benefit of...

  18. EPA ENERGY STAR Webinar: ENERGY STAR Portfolio Manager 201

    Office of Energy Efficiency and Renewable Energy (EERE)

    Continue to learn about EPA’s ENERGY STAR Portfolio Manager tool, with a deeper dive into more advanced functionalities such as: managing and tracking changes to your property uses over time; using...

  19. Stable Magnetic Fields in Static Stars

    E-Print Network [OSTI]

    A. Gruzinov

    2008-01-28

    We prove that static fluid stars can stably support magnetic fields (within the ideal MHD approximation).

  20. A Heavy Flavor Tracker for STAR

    SciTech Connect (OSTI)

    Xu, Z.; Chen, Y.; Kleinfelder, S.; Koohi, A.; Li, S.; Huang, H.; Tai, A.; Kushpil, V.; Sumbera, M.; Colledani, C.; Dulinski, W.; Himmi,A.; Hu, C.; Shabetai, A.; Szelezniak, M.; Valin, I.; Winter, M.; Surrow,B.; Van Nieuwenhuizen, G.; Bieser, F.; Gareus, R.; Greiner, L.; Lesser,F.; Matis, H.S.; Oldenburg, M.; Ritter, H.G.; Pierpoint, L.; Retiere, F.; Rose, A.; Schweda, K.; Sichtermann, E.; Thomas, J.H.; Wieman, H.; Yamamoto, E.; Kotov, I.

    2005-03-14

    We propose to construct a Heavy Flavor Tracker (HFT) for the STAR experiment at RHIC. The HFT will bring new physics capabilities to STAR and it will significantly enhance the physics capabilities of the STAR detector at central rapidities. The HFT will ensure that STAR will be able to take heavy flavor data at all luminosities attainable throughout the proposed RHIC II era.

  1. Nucleosynthesis in AGB Stars John Lattanzio

    E-Print Network [OSTI]

    Lattanzio, John

    Nucleosynthesis in AGB Stars John Lattanzio Dept of Mathematics and Statistics, Monash University of the nucleosynthesis occurring in AGB stars. We the summarise some new calculations of intermediate mass stars which include all thermal pulses until the star is about to leave the AGB, as well as a detailed nucleosynthesis

  2. 11/12/12 Take action on climate change OR THE PANDA GETS IT The Register 1/3www.theregister.co.uk/2012/11/12/climate_change_pandas/

    E-Print Network [OSTI]

    Earth' Mysterious galactic glow caused by Hitchhikers' Krikkit style stars Lone darknesswrapped suns food and shelter for other wildlife in the forest, including endangered species like the ploughshare

  3. Quantum Collapse in Quark Stars?

    SciTech Connect (OSTI)

    Perez Martinez, A.; Perez Rojas, H. [ICIMAF, Calle E esq 15 No. 309 Vedado (Cuba); Mosquera Cuesta, H. J. [Centro Brasileiro de Pesquisas Fisicas, Laboratorio de Cosmologia e Fisica Experimental de Altas Energias, Rua Dr. Xavier Sigaud 150, Urca, CEP 22290-180, Rio de Janeiro (Brazil)

    2006-06-19

    Quark matter is expected to exist in the interior of compact stellar objects as neutron stars or even the more exotic strange stars. Bare strange quark stars and (normal) strange quark-matter stars, those possessing a baryon (electron-supported) crust, are hypothesized as good candidates to explain the properties of a set of peculiar stellar sources. In this presentation, we modify the MIT Bag Model by including the electromagnetic interaction. We also show that this version of the MIT model implies the anisotropy of the Bag pressure due to the presence of the magnetic field. The equations of state of degenerate quarks gases are studied in the presence of ultra strong magnetic fields. The behavior of a system made-up of quarks having (or not) anomalous magnetic moment is reviewed. A structural instability is found, which is related to the anisotropic nature of the pressures in this highly magnetized matter.

  4. Neutron Stars : A Comparative Study

    E-Print Network [OSTI]

    Mehedi Kalam; Sk. Monowar Hossein; Sajahan Molla

    2015-10-23

    The inner structure of neutron star is considered from theoretical point of view and is compared with the observed data. We have proposed a form of an equation of state relating pressure with matter density which indicates the stiff equation of state of neutron stars. From our study we have calculated mass(M), compactness(u) and surface red-shift(Zs ) for the neutron stars namely PSR J1614-2230, PSR J1903+327, Cen X-3, SMC X-1, Vela X-1, Her X-1 and compared with the recent observational data. We have also indicated the possible radii of the different stars which needs further study. Finally we have examined the stability for such type of theoretical structure.

  5. ENERGY STAR Portfolio Manager 201

    Office of Energy Efficiency and Renewable Energy (EERE)

    Continue to learn about EPA’s new ENERGY STAR Portfolio Manager tool, with a deeper dive into more advanced functionalities such as: managing and tracking changes to your property uses over time;...

  6. ENERGY STAR Portfolio Manager 101

    Office of Energy Efficiency and Renewable Energy (EERE)

    Join us as we introduce and demonstrate the core functionality of EPA’s ENERGY STAR Portfolio Manager tool. Attendees will learn how to: navigate Portfolio Manager; add a property and enter details...

  7. Studying Young Stars with Large Spectroscopic Surveys

    E-Print Network [OSTI]

    Martell, Sarah L

    2015-01-01

    Galactic archaeology is the study of the history of star formation and chemical evolution in the Milky Way, based on present-day stellar populations. Studies of young stars are a key anchor point for Galactic archaeology, since quantities like the initial mass function and the star formation rate can be studied directly in young clusters and star forming regions. Conversely, massive spectroscopic Galactic archaeology surveys can be used as a data source for young star studies.

  8. Properties and Stability of Hybrid Stars

    E-Print Network [OSTI]

    S. Schramm; R. Negreiros; J. Steinheimer; T. Schürhoff; V. Dexheimer

    2011-12-09

    We discuss the properties of neutron stars and their modifications due to the occurrence of hyperons and quarks in the core of the star. More specifically, we consider the general problem of exotic particles inside compact stars in light of the observed two-solar mass pulsar. In addition, we investigate neutron star cooling and a possible explanation of the recently measured cooling curve of the neutron star in the supernova remnant Cas A.

  9. Upsilon Productions at STAR

    E-Print Network [OSTI]

    A. M. Hamed

    2010-05-22

    The $\\Upsilon(1S+2S+3S)\\to e^{+}e^{-}$ cross section is measured at mid-rapidity ($y$) in $p+p$ collisions and in d$+Au$ collisions at center-of-mass energy $\\sqrt{s}$ = 200 GeV with the STAR detector at RHIC. In $p+p$, the measured cross section is found to be consistent with the world data trend as a function of $\\sqrt{s}$, in agreement with the Color Evaportaion Model (CEM), and underestimated by the Color Singlet Model (CSM) up to the Next-to-Leading-Order Quantum Chromodynamics (NLO QCD) calculations. In d+$Au$, the measured cross section is in agreement with the CEM prediction with anti-shadowing effects, and the nuclear modification factor indicates that $\\Upsilon(1S+2S+3S)$ production follows binary scaling within the current uncertainties. These measurements provide a benchmark for the future measurements of $\\Upsilon$ production in $Au+Au$ collisions.

  10. The Quarkyonic Star

    E-Print Network [OSTI]

    Kenji Fukushima; Toru Kojo

    2015-11-10

    We discuss theoretical scenarios on crossover between nuclear matter (NM) and quark matter (QM). We classify various possibilities into three major scenarios according to the onset of diquark degrees of freedom that characterizes color-superconducting (CSC) states. In the conventional scenario NM occurs at the liquid-gas (or liquid-vacuum at zero temperature) phase transition and QM occurs next, after which CSC eventually appears. With the effect of strong correlation, the BEC-BCS scenario implies that CSC occurs next to NM and QM comes last in the BCS regime. We adopt the quarkyonic scenario in which NM, QM, and CSC are theoretically indistinguishable and thus these names refer to not distinct states but relevant descriptions of the same physical system. Based on this idea we propose a natural scheme to interpolate NM near normal nuclear density and CSC with vector coupling at high baryon density. We finally discuss the mass-radius relation of the neutron star and constraints on parameters in the proposed scheme.

  11. The Quarkyonic Star

    E-Print Network [OSTI]

    Fukushima, Kenji

    2015-01-01

    We discuss theoretical scenarios on crossover between nuclear matter (NM) and quark matter (QM). We classify various possibilities into three major scenarios according to the onset of diquark degrees of freedom that characterizes color-superconducting (CSC) states. In the conventional scenario NM occurs at the liquid-gas (or liquid-vacuum at zero temperature) phase transition and QM occurs next, after which CSC eventually appears. With the effect of strong correlation, the BEC-BCS scenario implies that CSC occurs next to NM and QM comes last in the BCS regime. We adopt the quarkyonic scenario in which NM, QM, and CSC are theoretically indistinguishable and thus these names refer to not distinct states but relevant descriptions of the same physical system. Based on this idea we propose a natural scheme to interpolate NM near normal nuclear density and CSC with vector coupling at high baryon density. We finally discuss the mass-radius relation of the neutron star and constraints on parameters in the proposed sc...

  12. The Quarkyonic Star

    E-Print Network [OSTI]

    Kenji Fukushima; Toru Kojo

    2015-09-01

    We discuss theoretical scenarios on crossover between nuclear matter (NM) and quark matter (QM). We classify various possibilities into three major scenarios according to the onset of diquark degrees of freedom that characterizes color-superconducting (CSC) states. In the conventional scenario NM occurs at the liquid-gas (or liquid-vacuum at zero temperature) phase transition and QM occurs next, after which CSC eventually appears. With the effect of strong correlation, the BEC-BCS scenario implies that CSC occurs next to NM and QM comes last in the BCS regime. We adopt the quarkyonic scenario in which NM, QM, and CSC are theoretically indistinguishable and thus these names refer to not distinct states but relevant descriptions of the same physical system. Based on this idea we propose a natural scheme to interpolate NM near normal nuclear density and CSC with vector coupling at high baryon density. We finally discuss the mass-radius relation of the neutron star and constraints on parameters in the proposed scheme.

  13. Kepler rapidly rotating giant stars

    E-Print Network [OSTI]

    Costa, A D; Bravo, J P; Paz-Chinchón, F; Chagas, M L das; Leão, I C; de Oliveira, G Pereira; da Silva, R Rodrigues; Roque, S; de Oliveira, L L A; da Silva, D Freire; De Medeiros, J R

    2015-01-01

    Rapidly rotating giant stars are relatively rare and may represent important stages of stellar evolution, resulting from stellar coalescence of close binary systems or accretion of sub-stellar companions by their hosting stars. In the present letter we report 17 giant stars observed in the scope of the Kepler space mission exhibiting rapid rotation behavior. For the first time the abnormal rotational behavior for this puzzling family of stars is revealed by direct measurements of rotation, namely from photometric rotation period, exhibiting very short rotation period with values ranging from 13 to 55 days. This finding points for remarkable surface rotation rates, up to 18 times the Sun rotation. These giants are combined with 6 other recently listed in the literature for mid-IR diagnostic based on WISE information, from which a trend for an infrared excess is revealed for at least a half of the stars, but at a level far lower than the dust excess emission shown by planet-bearing main-sequence stars.

  14. Testing Gravity Using Dwarf Stars

    E-Print Network [OSTI]

    Sakstein, Jeremy

    2015-01-01

    Generic scalar-tensor theories of gravity predict deviations from Newtonian physics inside astrophysical bodies. In this paper, we point out that low mass stellar objects, red and brown dwarf stars, are excellent probes of these theories. We calculate two important and potentially observable quantities: the radius of brown dwarfs and the minimum mass for hydrogen burning in red dwarfs. The brown dwarf radius can differ significantly from the GR prediction and upcoming surveys that probe the mass-radius relation for stars with masses $hydrogen burning can be larger than several presently observed Red Dwarf stars. This places a new and extremely stringent constraint on the parameters that appear in the effective field theory of dark energy and rules out several well-studied dark energy models.

  15. Testing Gravity Using Dwarf Stars

    E-Print Network [OSTI]

    Jeremy Sakstein

    2015-11-05

    Generic scalar-tensor theories of gravity predict deviations from Newtonian physics inside astrophysical bodies. In this paper, we point out that low mass stellar objects, red and brown dwarf stars, are excellent probes of these theories. We calculate two important and potentially observable quantities: the radius of brown dwarfs and the minimum mass for hydrogen burning in red dwarfs. The brown dwarf radius can differ significantly from the GR prediction and upcoming surveys that probe the mass-radius relation for stars with masses $hydrogen burning can be larger than several presently observed Red Dwarf stars. This places a new and extremely stringent constraint on the parameters that appear in the effective field theory of dark energy and rules out several well-studied dark energy models.

  16. Testing Gravity Theories Using Stars

    E-Print Network [OSTI]

    Jeremy Sakstein; Bhuvnesh Jain; Vinu Vikram

    2014-09-12

    Modified theories of gravity have received a renewed interest due to their ability to account for the cosmic acceleration. In order to satisfy the solar system tests of gravity, these theories need to include a screening mechanism that hides the modifications on small scales. One popular and well-studied theory is chameleon gravity. Our own galaxy is necessarily screened, but less dense dwarf galaxies may be unscreened and their constituent stars can exhibit novel features. In particular, unscreened stars are brighter, hotter and more ephemeral than screened stars in our own galaxy. They also pulsate with a shorter period. In this essay, we exploit these new features to constrain chameleon gravity to levels three orders of magnitude lower the previous measurements. These constraints are currently the strongest in the literature.

  17. First Stars III Conference Summary

    E-Print Network [OSTI]

    Brian W. O'Shea; Christopher F. McKee; Alexander Heger; Tom Abel

    2008-01-14

    The understanding of the formation, life, and death of Population III stars, as well as the impact that these objects had on later generations of structure formation, is one of the foremost issues in modern cosmological research and has been an active area of research during the past several years. We summarize the results presented at "First Stars III," a conference sponsored by Los Alamos National Laboratory, the Kavli Institute for Particle Astrophysics and Cosmology, and the Joint Institute for Nuclear Astrophysics. This conference, the third in a series, took place in July 2007 at the La Fonda Hotel in Santa Fe, New Mexico, U.S.A.

  18. Nuclear Physics of Neutron Stars

    E-Print Network [OSTI]

    J. Piekarewicz

    2009-01-28

    Understanding the equation of state (EOS) of cold nuclear matter, namely, the relation between the pressure and energy density, is a central goal of nuclear physics that cuts across a variety of disciplines. Indeed, the limits of nuclear existence, the collision of heavy ions, the structure of neutron stars, and the dynamics of core-collapse supernova, all depend critically on the equation of state of hadronic matter. In this contribution I will concentrate on the special role that nuclear physics plays in constraining the EOS of cold baryonic matter and its impact on the properties of neutron stars.

  19. Probing the Faintest Stars in a Globular Star Cluster

    E-Print Network [OSTI]

    Harvey B. Richer; Jay Anderson; James Brewer; Saul Davis; Gregory G. Fahlman; Brad M. S. Hansen; Jarrod Hurley; Jasonjot S. Kalirai; Ivan R. King; David Reitzel; R. Michael Rich; Michael M. Shara; Peter B. Stetson

    2007-02-07

    NGC 6397 is the second closest globular star cluster to the Sun. Using 5 days of time on the Hubble Space Telescope, we have constructed the deepest ever color-magnitude diagram for this cluster. We see a clear truncation in each of its two major stellar sequences. Faint red main sequence stars run out well above our observational limit and near to the theoretical prediction for the lowest mass stars capable of stable hydrogen-burning in their cores. We also see a truncation in the number counts of faint blue stars, namely white dwarfs. This reflects the limit to which the bulk of the white dwarfs can cool over the lifetime of the cluster. There is also a turn towards bluer colors in the least luminous of these objects. This was predicted for the very coolest white dwarfs with hydrogen-rich atmospheres as the formation of H2 causes their atmospheres to become largely opaque to infrared radiation due to collision-induced absorption.

  20. Probing the Faintest Stars in a Globular Star Cluster

    E-Print Network [OSTI]

    Richer, H B; Brewer, J; Davis, S; Fahlman, G G; Hansen, B M S; Hurley, J; Singh-Kalirai, J; King, I R; Reitzel, David B; Rich, R M; Shara, M M; Stetson, P B; Richer, Harvey B.; Anderson, Jay; Brewer, James; Davis, Saul; Fahlman, Gregory G.; Hansen, Brad M.S.; Hurley, Jarrod; Kalirai, Jasonjot S.; King, Ivan R.; Reitzel, David; Shara, Michael M.; Stetson, Peter B.

    2006-01-01

    NGC 6397 is the second closest globular star cluster to the Sun. Using 5 days of time on the Hubble Space Telescope, we have constructed the deepest ever color-magnitude diagram for this cluster. We see a clear truncation in each of its two major stellar sequences. Faint red main sequence stars run out well above our observational limit and near to the theoretical prediction for the lowest mass stars capable of stable hydrogen-burning in their cores. We also see a truncation in the number counts of faint blue stars, namely white dwarfs. This reflects the limit to which the bulk of the white dwarfs can cool over the lifetime of the cluster. There is also a turn towards bluer colors in the least luminous of these objects. This was predicted for the very coolest white dwarfs with hydrogen-rich atmospheres as the formation of H2 causes their atmospheres to become largely opaque to infrared radiation due to collision-induced absorption.

  1. Cold quark matter in compact stars

    SciTech Connect (OSTI)

    Franzon, B.; Fogaca, D. A.; Navarra, F. S.; Horvath, J. E.

    2013-03-25

    We used an equation of state for the cold quark matter to the study of properties of quark stars. We also discuss the absolute stability of quark matter and compute the mass-radius relation for self-bound stars.

  2. Equator Appliance: ENERGY STAR Referral (EZ 3720)

    Broader source: Energy.gov [DOE]

    DOE referred Equator Appliance clothes washer EZ 3720 to EPA, brand manager of the ENERGY STAR program, for appropriate action after DOE testing revealed that the model does not meet ENERGY STAR requirements.

  3. Quark stars: their influence on Astroparticle Physics

    E-Print Network [OSTI]

    Sanjay K. Ghosh

    2008-08-12

    We discuss some of the recent developments in the quark star physics along with the consequences of possible hadron to quark phase transition at high density scenario of neutron stars and their implications on the Astroparticle Physics.

  4. ENERGY STAR Webinar: Portfolio Manager 101

    Office of Energy Efficiency and Renewable Energy (EERE)

    Hosted by the U.S. Environmental Protection Agency's (EPA's) ENERGY STAR, this webinar will introduce and demonstrate the EPA's ENERGY STAR Portfolio Manager tool. Attendees will learn how to...

  5. Ralf Klessen: Acireale, May 19, 2005 Massive Stars fromMassive Stars from

    E-Print Network [OSTI]

    Klessen,Ralf

    and wherewhere stars form? What regulatesregulates the process and determines its efficiencyefficiency? How do

  6. Gas & Stars Aging low-mass stars eject their outer layers.

    E-Print Network [OSTI]

    Barnes, Joshua Edward

    Recycling Gas & Stars #12;Aging low-mass stars eject their outer layers. M57:The Ring Nebula #12;Thor's Emerald Helmet Winds from high-mass stars blow bubbles of hot gas. #12;Supernova blast waves in stars are mixed back into the gas. NGC 6992: Filaments of theVeil Nebula #12;Bubbles blown by high

  7. Bondi-Hoyle Accretion in Dense Star Clusters: Implications for Stars, Disks, and Planets

    E-Print Network [OSTI]

    Throop, Henry

    may take XX years to collapse, accrete mass, and begin fusion. Star formation in the cluster continuesBondi-Hoyle Accretion in Dense Star Clusters: Implications for Stars, Disks, and Planets Draft the Bondi-Hoyle accretion of gas from a GMC onto young star- disk systems in a cluster. This post

  8. Stellar Evolution: from star birth to star death and back again

    E-Print Network [OSTI]

    Cohen, David

    through the fusion of light elements into heavy ones #12;As stars age, they produce energy by fusionStellar Evolution: from star birth to star death and back again Prof. David Cohen Dept. of Physics old stars, as well as the interstellar gas that connects them. Some of this material is taken from one

  9. Abundance Signatures in Halo Stars: Clues to Nucleosynthesis in the First Stars

    E-Print Network [OSTI]

    Cowan, John

    Abundance Signatures in Halo Stars: Clues to Nucleosynthesis in the First Stars John J. Cowan-based telescopes to make extensive studies of Galactic halo stars. These stars contain the nucleosynthesis products the earliest Galactic r-process nucleosynthesis. These in turn will help to identify the characteristics

  10. NuSTAR: Nuclear Spectroscopic Telescope Array

    SciTech Connect (OSTI)

    Craig, Bill

    2012-06-13

    Bill Craig, an astrophysicist at Lawrence Livermore National Laboratory, describes the NASA NuSTAR mission, launched June 13, 2012.

  11. NuSTAR: Nuclear Spectroscopic Telescope Array

    ScienceCinema (OSTI)

    Craig, Bill

    2014-06-24

    Bill Craig, an astrophysicist at Lawrence Livermore National Laboratory, describes the NASA NuSTAR mission, launched June 13, 2012.

  12. Black Stars and Gamma Ray Bursts

    E-Print Network [OSTI]

    Tanmay Vachaspati

    2007-06-08

    Stars that are collapsing toward forming a black hole but are frozen near the Schwarzschild horizon are termed ``black stars''. Collisions of black stars, in contrast to black hole collisions, may be sources of gamma ray bursts, whose basic parameters are estimated quite simply and are found to be consistent with observed gamma ray bursts. Black star gamma ray bursts should be preceded by gravitational wave emission similar to that from the coalescence of black holes.

  13. STAR Highlights on Heavy Ion Physics

    E-Print Network [OSTI]

    Shusu Shi

    2014-09-30

    RHIC-STAR is a mid-rapidity collider experiment for studying high energy nuclear collisions. The main physics goals of STAR experiment are 1) studying the properties of the strongly coupled Quark Gluon Plasma, 2) explore the QCD phase diagram structure. In these proceedings, we will review the recent results of heavy ion physics at STAR.

  14. Motivation Examples Star Avoiding Ramsey Numbers

    E-Print Network [OSTI]

    Isaak, Garth

    Motivation Examples Star Avoiding Ramsey Numbers Jonelle Hook, Garth Isaak Department and Cryptography Jonelle Hook, Garth Isaak Star Avoiding Ramsey Numbers #12;Motivation Examples Graph Ramsey-coloring of K13 has a red C5 or a blue K4. Jonelle Hook, Garth Isaak Star Avoiding Ramsey Numbers #12

  15. Russian Conference on Physics of Neutron Stars

    E-Print Network [OSTI]

    Russian Conference on Physics of Neutron Stars ABSTRACTS June 24­27, 2008 Ioffe Physical-Technical Institute Saint-Petersburg #12;#12;Russian Conference on PHYSICS OF NEUTRON STARS ABSTRACTS June 24­27, 2008 2008 #12;Preface The conference on Physics of Neutron Stars at the Ioffe Physical-Technical Institute

  16. Bright Star Astrometry with URAT

    E-Print Network [OSTI]

    Zacharias, Norbert

    2015-01-01

    The U.S. Naval Observatory Robotic Astrometric Telescope (URAT) is observing the northern sky since April 2012 for an astrometric survey. Multiple overlaps per year are performed in a single bandpass (680$-$750 nm) using the "redlens" 20 cm aperture astrograph and a mosaic of large CCDs. Besides the regular, deep survey to magnitude 18.5, short exposures with an objective grating are taken to access stars as bright as 3rd magnitude. A brief overview of the program, observing and reductions is given. Positions on the 8 to 20 mas level are obtained of 66,202 Hipparcos stars at current epochs. These are compared to the Hipparcos Catalog to investigate its accuracy. About 20\\% of the observed Hipparcos stars are found to have inconsitent positions with the Hipparcos Catalog prediction on the 3 sigma level or over (about 75 mas or more discrepant position offsets). Some stars are now seen at an arcsec (or 25 sigma) off their Hipparcos Catalog predicted position.

  17. Maximally incompressible neutron star matter

    E-Print Network [OSTI]

    Timothy S. Olson

    2000-12-07

    Relativistic kinetic theory, based on the Grad method of moments as developed by Israel and Stewart, is used to model viscous and thermal dissipation in neutron star matter and determine an upper limit on the maximum mass of neutron stars. In the context of kinetic theory, the equation of state must satisfy a set of constraints in order for the equilibrium states of the fluid to be thermodynamically stable and for perturbations from equilibrium to propagate causally via hyperbolic equations. Application of these constraints to neutron star matter restricts the stiffness of the most incompressible equation of state compatible with causality to be softer than the maximally incompressible equation of state that results from requiring the adiabatic sound speed to not exceed the speed of light. Using three equations of state based on experimental nucleon-nucleon scattering data and properties of light nuclei up to twice normal nuclear energy density, and the kinetic theory maximally incompressible equation of state at higher density, an upper limit on the maximum mass of neutron stars averaging 2.64 solar masses is derived.

  18. BPS Skyrmions as neutron stars

    E-Print Network [OSTI]

    C. Adam; C. Naya; J. Sanchez-Guillen; R. Vazquez; A. Wereszczynski

    2015-02-26

    The BPS Skyrme model has been demonstrated already to provide a physically intriguing and quantitatively reliable description of nuclear matter. Indeed, the model has both the symmetries and the energy-momentum tensor of a perfect fluid, and thus represents a field theoretic realization of the "liquid droplet" model of nuclear matter. In addition, the classical soliton solutions together with some obvious corrections (spin-isospin quantization, Coulomb energy, proton-neutron mass difference) provide an accurate modeling of nuclear binding energies for heavier nuclei. These results lead to the rather natural proposal to try to describe also neutron stars by the BPS Skyrme model coupled to gravity. We find that the resulting self-gravitating BPS Skyrmions provide excellent results as well as some new perspectives for the description of bulk properties of neutron stars when the parameter values of the model are extracted from nuclear physics. Specifically, the maximum possible mass of a neutron star before black-hole formation sets in is a few solar masses, the precise value depending on the precise values of the model parameters, and the resulting neutron star radius is of the order of 10 km.

  19. Star Formation in the Local Milky Way

    E-Print Network [OSTI]

    Lada, Charles J

    2015-01-01

    Studies of molecular clouds and young stars near the sun have provided invaluable insights into the process of star formation. Indeed, much of our physical understanding of this topic has been derived from such studies. Perhaps the two most fundamental problems confronting star formation research today are: 1) determining the origin of stellar mass and 2) deciphering the nature of the physical processes that control the star formation rate in molecular gas. As I will briefly outline here, observations and studies of local star forming regions are making particularly significant contributions toward the solution of both these important problems.

  20. Star formation in 30 Doradus

    E-Print Network [OSTI]

    De Marchi, Guido; Panagia, Nino; Beccari, Giacomo; Spezzi, Loredana; Sirianni, Marco; Andersen, Morten; Mutchler, Max; Balick, Bruce; Dopita, Michael A; Frogel, Jay A; Whitmore, Bradley C; Bond, Howard; Clazetti, Daniela; Carollo, C Marcella; Disney, Michael J; Hall, Donald N B; Holtzman, Jon A; Kimble, Randy A; McCarthy, Patrick J; O'Connell, Robert W; Saha, Abhijit; Silk, Joseph I; Trauger, John T; Walker, Alistair R; Windhorst, Rogier A; Young, Erick T

    2011-01-01

    Using observations obtained with the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope (HST), we have studied the properties of the stellar populations in the central regions of 30 Dor, in the Large Magellanic Cloud. The observations clearly reveal the presence of considerable differential extinction across the field. We characterise and quantify this effect using young massive main sequence stars to derive a statistical reddening correction for most objects in the field. We then search for pre-main sequence (PMS) stars by looking for objects with a strong (> 4 sigma) Halpha excess emission and find about 1150 of them over the entire field. Comparison of their location in the Hertzsprung-Russell diagram with theoretical PMS evolutionary tracks for the appropriate metallicity reveals that about one third of these objects are younger than ~4Myr, compatible with the age of the massive stars in the central ionising cluster R136, whereas the rest have ages up to ~30Myr, with a median age of ~12Myr. Th...

  1. Evolution of Nuclear Star Clusters

    E-Print Network [OSTI]

    David Merritt

    2009-01-05

    Two-body relaxation times of nuclear star clusters are short enough that gravitational encounters should substantially affect their structure in 10 Gyr or less. In nuclear star clusters without massive black holes, dynamical evolution is a competition between core collapse, which causes densities to increase, and heat input from the surrounding galaxy, which causes densities to decrease. The maximum extent of a nucleus that can resist expansion is derived numerically for a wide range of initial conditions; observed nuclei are shown to be compact enough to resist expansion, although there may have been an earlier generation of low-density nuclei that were dissolved. An evolutionary model for NGC 205 is presented which suggests that the nucleus of this galaxy has already undergone core collapse. Adding a massive black hole to a nucleus inhibits core collapse, and nuclear star clusters with black holes always expand, due primarily to heat input from the galaxy and secondarily to heating from stellar disruptions. The expansion rate is smaller for larger black holes due to the smaller temperature difference between galaxy and nucleus when the black hole is large. The rate of stellar tidal disruptions and its variation with time are computed for a variety of initial models. The disruption rate generally decreases with time due to the evolving nuclear density, particularly in the faintest galaxies, assuming that scaling relations derived for luminous galaxies can be extended to low luminosities.

  2. X-ray emission from O stars

    E-Print Network [OSTI]

    David H. Cohen

    2008-02-01

    Young O stars are strong, hard, and variable X-ray sources, properties which strongly affect their circumstellar and galactic environments. After ~1 Myr, these stars settle down to become steady sources of soft X-rays. I use high-resolution X-ray spectroscopy and MHD modeling to show that young O stars like theta-1 Ori C are well explained by the magnetically channeled wind shock scenario. After their magnetic fields dissipate, older O stars produce X-rays via shock heating in their unstable stellar winds. Here too I use X-ray spectroscopy and numerical modeling to confirm this scenario. In addition to elucidating the nature and cause of the O star X-ray emission, modeling of the high-resolution X-ray spectra of O supergiants provides strong evidence that mass-loss rates of these O stars have been overestimated.

  3. Sequentially Triggered Star Formation in OB Associations

    E-Print Network [OSTI]

    Thomas Preibisch; Hans Zinnecker

    2006-10-27

    We discuss observational evidence for sequential and triggered star formation in OB associations. We first review the star formation process in the Scorpius-Centaurus OB association, the nearest OB association to the Sun, where several recent extensive studies have allowed us to reconstruct the star formation history in a rather detailed way. We then compare the observational results with those obtained for other OB associations and with recent models of rapid cloud and star formation in the turbulent interstellar medium. We conclude that the formation of whole OB subgroups (each consisting of several thousand stars) requires large-scale triggering mechanisms such as shocks from expanding wind and supernova driven superbubbles surrounding older subgroups. Other triggering mechanisms, like radiatively driven implosion of globules, also operate, but seem to be secondary processes, forming only small stellar groups rather than whole OB subgroups with thousands of stars.

  4. Dynamical evolution of fermion-boson stars

    E-Print Network [OSTI]

    Susana Valdez-Alvarado; Carlos Palenzuela; Daniela Alic; L. Arturo Ureña-López

    2015-11-01

    Compact objects, like neutron stars and white dwarfs, may accrete dark matter, and then be sensitive probes of its presence. These compact stars with a dark matter component can be modeled by a perfect fluid minimally coupled to a complex scalar field (representing a bosonic dark matter component), resulting in objects known as fermion-boson stars. We have performed the dynamical evolution of these stars in order to analyze their stability, and to study their spectrum of normal modes, which may reveal the amount of dark matter in the system. Their stability analysis shows a structure similar to that of an isolated (fermion or boson) star, with equilibrium configurations either laying on the stable or on the unstable branch. The analysis of the spectrum of normal modes indicates the presence of new oscillation modes in the fermionic part of the star, which result from the coupling to the bosonic component through the gravity.

  5. Radio Triggered Star Formation in Cooling Flows

    E-Print Network [OSTI]

    B. R. McNamara

    1999-11-08

    The giant galaxies located at the centers of cluster cooling flows are frequently sites of vigorous star formation. In some instances, star formation appears to have been triggered by the galaxy's radio source. The colors and spectral indices of the young populations are generally consistent with short duration bursts or continuous star formation for durations much less than 1 Gyr, which is less than the presumed ages of cooling flows. The star formation properties are inconsistent with fueling by a continuously accreting cooling flow, although the prevalence of star formation is consistent with repeated bursts and periodic refueling. Star formation may be fueled, in some cases, by cold material stripped from neighboring cluster galaxies.

  6. Storage and Assay of Tritium in STAR

    SciTech Connect (OSTI)

    Longhurst, Glen R.; Anderl, Robert A.; Pawelko, Robert J.; Stoots, Carl J.

    2005-07-15

    The Safety and Tritium Applied Research (STAR) facility at the Idaho National Engineering and Environmental Laboratory (INEEL) is currently being commissioned to investigate tritium-related safety questions for fusion and other technologies. The tritium inventory for the STAR facility will be maintained below 1.5 g to avoid the need for STAR to be classified as a Category 3 nuclear facility. A key capability in successful operation of the STAR facility is the ability to receive, inventory, and dispense tritium to the various experiments underway there. The system central to that function is the Tritium Storage and Assay System (SAS).The SAS has four major functions: (1) receiving and holding tritium, (2) assaying, (3) dispensing, and (4) purifying hydrogen isotopes from non-hydrogen species.This paper describes the design and operation of the STAR SAS and the procedures used for tritium accountancy in the STAR facility.

  7. EPA ENERGY STAR Webinar: How to Apply for the ENERGY STAR Certification

    Broader source: Energy.gov [DOE]

    Join us to learn about applying for ENERGY STAR Certification in Portfolio Manager. Understand the value of the ENERGY STAR certification, see the step-by-step process of applying, and gain tips to...

  8. EPA ENERGY STAR Webinar: How to Apply for the ENERGY STAR

    Broader source: Energy.gov [DOE]

    Join us to learn about applying for ENERGY STAR Certification in Portfolio Manager. Understand the value of the ENERGY STAR certification, see the step-by-step process of applying, and gain tips to...

  9. From nuclear matter to Neutron Stars

    E-Print Network [OSTI]

    T. K. Jha

    2009-02-02

    Neutron stars are the most dense objects in the observable Universe and conventionally one uses nuclear theory to obtain the equation of state (EOS) of dense hadronic matter and the global properties of these stars. In this work, we review various aspects of nuclear matter within an effective Chiral model and interlink fundamental quantities both from nuclear saturation as well as vacuum properties and correlate it with the star properties.

  10. The evolution of naked helium stars with a neutron-star companion in close binary systems

    E-Print Network [OSTI]

    J. D. M. Dewi; O. R. Pols; G. J. Savonije; E. P. J. van den Heuvel

    2002-01-15

    The evolution of helium stars with masses of 1.5 - 6.7 M_sun in binary systems with a 1.4 M_sun neutron-star companion is presented. Such systems are assumed to be the remnants of Be/X-ray binaries with B-star masses in the range of 8 - 20 M_sun which underwent a case B or case C mass transfer and survived the common-envelope and spiral-in process. The orbital period is chosen such that the helium star fills its Roche lobe before the ignition of carbon in the centre. We distinguish case BA (in which mass transfer is initiated during helium core burning) from case BB (onset of Roche-lobe overflow occurs after helium core burning is terminated, but before the ignition of carbon). We found that the remnants of case BA mass transfer from 1.5 - 2.9 M_sun helium stars are heavy CO white dwarfs. This implies that a star initially as massive as 12 M_sun is able to become a white dwarf. CO white dwarfs are also produced from case BB mass transfer from 1.5 - 1.8 M_sun helium stars, while ONe white dwarfs are formed from 2.1 - 2.5 M_sun helium stars. Case BB mass transfer from more-massive helium stars with a neutron-star companion will produce a double neutron-star binary. We are able to distinguish the progenitors of type Ib supernovae (as the high-mass helium stars or systems in wide orbits) from those of type Ic supernovae (as the lower-mass helium stars or systems in close orbits). Finally, we derive a "zone of avoidance" in the helium star mass vs. initial orbital period diagram for producing neutron stars from helium stars.

  11. Abundances of massive stars: some recent developments

    E-Print Network [OSTI]

    T. Morel

    2008-11-25

    Thanks to their usefulness in various fields of astrophysics (e.g. mixing processes in stars, chemical evolution of galaxies), the last few years have witnessed a large increase in the amount of abundance data for early-type stars. Two intriguing results emerging since the last reviews on this topic will be discussed: (a) nearby OB stars exhibit metal abundances generally lower than the solar/meteoritic estimates; (b) evolutionary models of single objects including rotation are largely unsuccessful in explaining the CNO properties of stars in the Galaxy and in the Magellanic clouds.

  12. Rapid cooling and structure of neutron stars

    SciTech Connect (OSTI)

    Van Riper, K.A.; Lattimer, J.M.

    1992-07-01

    This report discusses the following topics on neutron stars: direct URCA neutrino emission; thermal evolution models; analytic model for diffusion through the crust; and core superfluidity. (LSP).

  13. Rapid cooling and structure of neutron stars

    SciTech Connect (OSTI)

    Van Riper, K.A. ); Lattimer, J.M. . Dept. of Earth and Space Sciences)

    1992-01-01

    This report discusses the following topics on neutron stars: direct URCA neutrino emission; thermal evolution models; analytic model for diffusion through the crust; and core superfluidity. (LSP).

  14. A Galactic O-Star Catalog

    E-Print Network [OSTI]

    J. Maíz-Apellániz; N. R. Walborn; H. Á. Galué; L. H. Wei

    2003-11-09

    We have produced a catalog of 378 Galactic O stars with accurate spectral classifications which is complete for Vweb-based version with links to online services.

  15. Star Formation in the Gulf of Mexico

    E-Print Network [OSTI]

    Armond, Tina; Bally, John; Aspin, Colin

    2011-01-01

    We present an optical/infrared study of the dense molecular cloud, L935, dubbed "The Gulf of Mexico", which separates the North America and the Pelican nebulae, and we demonstrate that this area is a very active star forming region. A wide-field imaging study with interference filters has revealed 35 new Herbig-Haro objects in the Gulf of Mexico. A grism survey has identified 41 Halpha emission-line stars, 30 of them new. A small cluster of partly embedded pre-main sequence stars is located around the known LkHalpha 185-189 group of stars, which includes the recently erupting FUor HBC 722.

  16. TURBOVELOCITY STARS: KICKS RESULTING FROM THE TIDAL DISRUPTION OF SOLITARY STARS

    SciTech Connect (OSTI)

    Manukian, Haik; Guillochon, James; Ramirez-Ruiz, Enrico [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); O'Leary, Ryan M., E-mail: jfg@ucolick.org [Department of Astronomy, University of California, Berkeley, CA 94720 (United States)

    2013-07-10

    The centers of most known galaxies host supermassive black holes (SMBHs). In orbit around these black holes are a centrally concentrated distribution of stars, both in single and in binary systems. Occasionally, these stars are perturbed onto orbits that bring them close to the SMBH. If the star is in a binary system, the three-body interaction with the SMBH can lead to large changes in orbital energy, depositing one of the two stars on a tightly-bound orbit, and its companion into a hyperbolic orbit that may escape the galaxy. In this Letter, we show that the disruption of solitary stars can also lead to large positive increases in orbital energy. The kick velocity depends on the amount of mass the star loses at pericenter, but not on the ratio of black hole to stellar mass, and are at most the star's own escape velocity. We find that these kicks are usually too small to result in the ejection of stars from the Milky Way, but can eject the stars from the black hole's sphere of influence, reducing their probability of being disrupted again. We estimate that {approx} 10{sup 5} stars, {approx} 1% of all stars within 10 pc of the galactic center, are likely to have had mass removed by the central black hole through tidal interaction, and speculate that these 'turbovelocity' stars will at first be redder, but eventually bluer, and always brighter than their unharassed peers.

  17. STARS Training Needs Assessment Learner Instructions 07/2009 1 STARS Training Needs Assessment

    E-Print Network [OSTI]

    Ford, James

    STARS Training Needs Assessment Learner Instructions 07/2009 1 STARS Training Needs Assessment. · Click the STARS (Training) tab. · Click My Training Needs in the left menu. · Click the secure link to continue to My Training Needs. On the Training Needs Assessment page, click the box to the left of every

  18. Ralf Klessen: Basel: 29. 11, 2006 Star FormationStar Formation

    E-Print Network [OSTI]

    Klessen,Ralf

    (Hubble Ultra-Deep Field, from HST Web site) #12;Ralf Klessen: Basel: 29. 11, 2006 Antennae Stars in the Milky WayStars in the Milky Way On the night sky, you see stars and dark clouds Disks in Orion (data: Mark McCaughrean)protostellar disks: dark shades in front

  19. Star graphs and Seba billiards

    E-Print Network [OSTI]

    G. Berkolaiko; E. B. Bogomolny; J. P. Keating

    2000-10-26

    We derive an exact expression for the two-point correlation function for quantum star graphs in the limit as the number of bonds tends to infinity. This turns out to be identical to the corresponding result for certain Seba billiards in the semiclassical limit. Reasons for this are discussed. The formula we derive is also shown to be equivalent to a series expansion for the form factor - the Fourier transform of the two-point correlation function - previously calculated using periodic orbit theory.

  20. Energy Star | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTIONRobertsdale, AlabamaETEC GmbH JumpEllenville, NewLtd EILEnergy DatadataCentreCo LtdEnergy Star Jump

  1. ENERGY STAR | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIX E LISTStar2-0057-EA Jump to:of the NationalDynetek Europe GmbHEDENERGY STAR Jump to:

  2. Shooting Star | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION JEnvironmental Jump to:EA EIS ReportEurope GmbH Jump to: navigation, searchIndiaIIIIShooting Star

  3. Carbon Stars | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION JEnvironmentalBowerbank,Cammack Village, Arkansas:Fund for Spanish Firms FC2EPower &Stars Jump

  4. 2 Star formation and outflows: an overview 2.1 The current picture of lowmass star formation

    E-Print Network [OSTI]

    Stanke, Thomas

    #24; star is not yet high enough for hydrogen fusion at the time when accretion dies out temperature is high enough for hydrogen fusion, the star #12; 12 2 STAR FORMATION AND OUTFLOWS: AN OVERVIEW11 2 Star formation and outflows: an overview 2.1 The current picture of low­mass star formation

  5. STAR

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 Outreach Home RoomPreservation of Fe(II) byMultidayAlumni > The2/01/12 Page 1NEWSSupport Request To use this

  6. SDSS spectroscopic survey of stars

    E-Print Network [OSTI]

    Z. Ivezic; D. Schlegel; A. Uomoto; N. Bond; T. Beers; C. Allende Prieto; R. Wilhelm; Y. Sun Lee; T. Sivarani; M. Juric; R. Lupton; C. Rockosi; G. Knapp; J. Gunn; B. Yanny; S. Jester; S. Kent; J. Pier; J. Munn; G. Richards; H. Newberg; M. Blanton; D. Eisenstein; S. Hawley; S. Anderson; H. Harris; F. Kiuchi; A. Chen; J. Bushong; H. Sohi; D. Haggard; A. Kimball; J. Barentine; H. Brewington; M. Harvanek; S. Kleinman; J. Krzesinski; D. Long; A. Nitta; S. Snedden; for the SDSS Collaboration

    2007-01-17

    In addition to optical photometry of unprecedented quality, the Sloan Digital Sky Survey (SDSS) is also producing a massive spectroscopic database. We discuss determination of stellar parameters, such as effective temperature, gravity and metallicity from SDSS spectra, describe correlations between kinematics and metallicity, and study their variation as a function of the position in the Galaxy. We show that stellar parameter estimates by Beers et al. show a good correlation with the position of a star in the g-r vs. u-g color-color diagram, thereby demonstrating their robustness as well as a potential for photometric parameter estimation methods. Using Beers et al. parameters, we find that the metallicity distribution of the Milky Way stars at a few kpc from the galactic plane is bimodal with a local minimum at [Z/Zo]~ -1.3. The median metallicity for the low-metallicity [Z/Zo] -1.3 sample. We also find that the low-metallicity sample has ~2.5 times larger velocity dispersion and that it does not rotate (at the ~10 km/s level), while the rotational velocity of the high-metallicity sample decreases smoothly with the height above the galactic plane.

  7. Cooling of Color Superconducting Compact Stars

    E-Print Network [OSTI]

    David Blaschke

    2006-03-26

    We review the status of research on the cooling of compact stars, with emphasis on the influence of color superconducting quark matter phases. Although a consistent microscopic approach is not yet available, severe constraints on the phase structure of matter at high densities come from recent mass and cooling observations of compact stars.

  8. Search for Variable Stars in the WTS

    E-Print Network [OSTI]

    Pinfield, David J.

    Search for Variable Stars in the WTS Database Hristo Stoev Laboratory of Stellar Astrophysics of January 2010 at LAEX in Madrid, Spain #12;WTS Survey Release 0.1 Search for variable stars in the FOV Narrow down my selection only to one of the detectors ­ 15000 light curves #12;WTS Survey Release 0

  9. Long Baseline Interferometry of Be Stars

    E-Print Network [OSTI]

    Olivier Chesneau; Thomas Rivinius

    2005-10-24

    We give an introduction to interferometrical concepts and their applicability to Be stars. The first part of the paper concentrates on a short historic overview and basic principles of two-beam interferometric observations. In the second part, the VLTI/MIDI instrument is introduced and its first results on Be stars, obtained on alpha Ara and delta Cen, are outlined.

  10. FAINT RADIO SOURCES AND STAR FORMATION HISTORY

    E-Print Network [OSTI]

    Waddington, Ian

    FAINT RADIO SOURCES AND STAR FORMATION HISTORY Deborah B. Haarsma 1 , R. Bruce Partridge 1 , Ian 85287­1504 USA Abstract. Faint extragalactic radio sources provide important information about the global history of star formation. Sensitive radio observations of the Hubble Deep Field and other fields

  11. Fusion cycles in stars and stellar neutrinos

    E-Print Network [OSTI]

    G. Wolschin

    2002-10-01

    Starting from the early works by Weizsaecker and Bethe about fusion cycles and energy conversion in stars, a brief survey of thermonuclear processes in stars leading to contemporary research problems in this field is given. Special emphasis is put on the physics of stellar and, in particular, solar neutrinos which is at the frontline of current investigations.

  12. Fusion cycles in stars and stellar neutrinos

    E-Print Network [OSTI]

    Wolschin, G

    2003-01-01

    Starting from the early works by Weizsaecker and Bethe about fusion cycles and energy conversion in stars, a brief survey of thermonuclear processes in stars leading to contemporary research problems in this field is given. Special emphasis is put on the physics of stellar and, in particular, solar neutrinos which is at the frontline of current investigations.

  13. First Structure Formation and the First Stars

    E-Print Network [OSTI]

    Michael L. Norman; Tom Abel; Greg Bryan

    2000-05-11

    We discuss the results of recent 3D simulations of first structure formation in relationship to the formation of the first stars. On the basis of a new, high-resolution AMR simulation (spatial dynamic range = 30,000,000), we conclude that the first stars are likely to be massive.

  14. Nuclear and gravitational energies in stars

    SciTech Connect (OSTI)

    Meynet, Georges; Ekström, Sylvia [Astronomical Observatory of Geneva University (Switzerland); Courvoisier, Thierry [ISDC, Astronomical Observatory of Geneva University (Switzerland)

    2014-05-09

    The force that governs the evolution of stars is gravity. Indeed this force drives star formation, imposes thermal and density gradients into stars at hydrostatic equilibrium and finally plays the key role in the last phases of their evolution. Nuclear power in stars governs their lifetimes and of course the stellar nucleosynthesis. The nuclear reactions are at the heart of the changes of composition of the baryonic matter in the Universe. This change of composition, in its turn, has profound consequences on the evolution of stars and galaxies. The energy extracted from the gravitational, respectively nuclear reservoirs during the lifetimes of stars of different masses are estimated. It is shown that low and intermediate mass stars (M < 8 M{sub ?}) extract roughly 90 times more energy from their nuclear reservoir than from their gravitational one, while massive stars (M > 8 M{sub ?}), which explode in a supernova explosion, extract more than 5 times more energy from the gravitational reservoir than from the nuclear one. We conclude by discussing a few important nuclear reactions and their link to topical astrophysical questions.

  15. The Isotopic Abundances of Magnesium in Stars

    E-Print Network [OSTI]

    Pamela Gay; David L. Lambert

    1999-11-11

    Isotopic abundance ratios 24^Mg:25^Mg:26^Mg are derived for 20 stars from high- resolution spectra of the MgH A-X 0-0 band at 5140AA. With the exception of the weak g-band giant HR 1299, the stars are dwarfs that sample the metallicity range -1.8 < [Fe/H] <0.0. The abundance of 25^Mg amd 26^Mg relative to the dominant isotope 24^Mg decreases with decreasing [Fe/H] in fair accord with predictions from a recent model of galactic chemical evolution in which the Mg isotopes are synthesised by massive stars. Several stars appear especially enriched in the heavier Mg isotopes suggesting contamination by material from the envelopes of intermediate-mass AGB stars.

  16. Webinar: ENERGY STAR Hot Water Systems for High Performance Homes...

    Energy Savers [EERE]

    Webinar: ENERGY STAR Hot Water Systems for High Performance Homes Webinar: ENERGY STAR Hot Water Systems for High Performance Homes This presentation is from the Building America...

  17. ENERGY STAR Certified Homes, Version 3 (Rev. 07) National Program...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    National Program Requirements ENERGY STAR Certified Homes, Version 3 (Rev. 07) National Program Requirements ENERGY STAR Certified Homes, Version 3 (Rev. 07) National Program...

  18. Building Performance with ENERGY STAR Pilot Program Portfolio...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Performance with ENERGY STAR Pilot Program Portfolio Manager Fact Sheet Building Performance with ENERGY STAR Pilot Program Portfolio Manager Fact Sheet Building Performance with...

  19. The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission (Journal...

    Office of Scientific and Technical Information (OSTI)

    The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission Citation Details In-Document Search Title: The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission You are...

  20. The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission (Journal...

    Office of Scientific and Technical Information (OSTI)

    The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission Citation Details In-Document Search Title: The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission Authors: Harrison,...

  1. The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission (Journal...

    Office of Scientific and Technical Information (OSTI)

    Nuclear Spectroscopic Telescope Array (NuSTAR) Mission Citation Details In-Document Search Title: The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission Authors: Harrison,...

  2. On the co-existence of chemically peculiar Bp stars, slowly pulsating B stars and constant B stars in the same part of the H-R diagram

    E-Print Network [OSTI]

    M. Briquet; S. Hubrig; P. De Cat; C. Aerts; P. North; M. Scholler

    2007-02-05

    Aims. In order to better model massive B-type stars, we need to understand the physical processes taking place in slowly pulsating B (SPB) stars, chemically peculiar Bp stars, and non-pulsating normal B stars co-existing in the same part of the H-R diagram. Methods. We carry out a comparative study between samples of confirmed and well-studied SPB stars and a sample of well-studied Bp stars with known periods and magnetic field strengths. We determine their evolutionary state using accurate HIPPARCOS parallaxes and Geneva photometry. We discuss the occurrence and strengths of magnetic fields as well as the occurrence of stellar pulsation among both groups. Further, we make a comparison of Geneva photometric variability for both kinds of stars. Results. The group of Bp stars is significantly younger than the group of SPB stars. Longitudinal magnetic fields in SPB stars are weaker than those of Bp stars, suggesting that the magnetic field strength is an important factor for B type stars to become chemically peculiar. The strongest magnetic fields appear in young Bp stars, indicating a magnetic field decay in stars at advanced ages. Rotation periods of Bp and pulsation periods of SPB stars are of the same order and the behaviour of Geneva photometric variability of some Bp stars cannot be distinguished from the variability of SPB stars, illustrating the difficulty to interpret the observed variability of the order of days for B-type stars. We consider the possibility that pulsation could be responsible for the variability among chemically peculiar stars. In particular, we show that a non-linear pulsation model is not excluded by photometry for the Bp star HD175362.

  3. Gravitational waves from perturbed stars

    E-Print Network [OSTI]

    Valeria Ferrari

    2011-05-09

    Non radial oscillations of neutron stars are associated with the emission of gravitational waves. The characteristic frequencies of these oscillations can be computed using the theory of stellar perturbations, and they are shown to carry detailed information on the internal structure of the emitting source. Moreover, they appear to be encoded in various radiative processes, as for instance in the tail of the giant flares of Soft Gamma Repeaters. Thus, their determination is central to the theory of stellar perturbation. A viable approach to the problem consists in formulating this theory as a problem of resonant scattering of gravitational waves incident on the potential barrier generated by the spacetime curvature. This approach discloses some unexpected correspondences between the theory of stellar perturbations and the theory of quantum mechanics, and allows us to predict new relativistic effects.

  4. Adaptive Optics in Star Formation

    E-Print Network [OSTI]

    Wolfgang Brandner

    2003-09-29

    Over the past ten years, the concept of adaptive optics has evolved from early experimental stages to a standard observing tool now available at almost all major optical and near-infrared telescope facilities. Adaptive optics will also be essential in exploiting the full potential of the large optical/infrared interferometers currently under construction. Both observations with high-angular resolution and at high contrast, and with a high point source sensitivity are facilitated by adaptive optics. Among the areas which benefit most from the use of adaptive optics are studies of the circumstellar environment (envelopes, disks, outflows), substellar companions and multiple systems, and dense young stellar populations. This contribution highlights some of the recent advances in star formation studies facilitated by adaptive optics, and gives a brief tutorial on optimized observing and data reduction strategies.

  5. Magnetic fields in beta Cep, SPB, and Be stars

    E-Print Network [OSTI]

    Schoeller, M; Briquet, M; Ilyin, I

    2013-01-01

    Recent observational and theoretical results emphasize the potential significance of magnetic fields for structure, evolution, and environment of massive stars. Depending on their spectral and photometric behavior, the upper main-sequence B-type stars are assigned to different groups, such as beta Cep stars and slowly pulsating B (SPB) stars, He-rich and He-deficient Bp stars, Be stars, BpSi stars, HgMn stars, or normal B-type stars. All these groups are characterized by different magnetic field geometry and strength, from fields below the detection limit of a few Gauss up to tens of kG. Our collaboration was the first to systematically study the magnetic fields in representative samples of different types of main-sequence B stars. In this article, we give an overview about what we have learned during the last years about magnetic fields in beta Cep, SPB, and Be stars.

  6. Binary Neutron Stars with Arbitrary Spins in Numerical Relativity

    E-Print Network [OSTI]

    Tacik, Nick; Pfeiffer, Harald P; Haas, Roland; Ossokine, Serguei; Kaplan, Jeff; Muhlberger, Curran; Duez, Matt D; Kidder, Lawrence E; Scheel, Mark A; Szilágyi, Béla

    2015-01-01

    We present a code to construct initial data for binary neutron star systems in which the stars are rotating. Our code, based on a formalism developed by Tichy, allows for arbitrary rotation axes of the neutron stars and is able to achieve rotation rates near rotational breakup. We compute the neutron star angular momentum through quasi-local angular momentum integrals. When constructing irrotational binary neutron stars, we find a very small residual dimensionless spin of $\\sim 2\\times 10^{-4}$. Evolutions of rotating neutron star binaries show that the magnitude of the stars' angular momentum is conserved, and that the spin- and orbit-precession of the stars is well described by post-Newtonian approximation. We demonstrate that orbital eccentricity of the binary neutron stars can be controlled to $\\sim 0.1\\%$. The neutron stars show quasi-normal mode oscillations at an amplitude which increases with the rotation rate of the stars.

  7. Binary Neutron Stars with Arbitrary Spins in Numerical Relativity

    E-Print Network [OSTI]

    Nick Tacik; Francois Foucart; Harald P. Pfeiffer; Roland Haas; Serguei Ossokine; Jeff Kaplan; Curran Muhlberger; Matt D. Duez; Lawrence E. Kidder; Mark A. Scheel; Béla Szilágyi

    2015-08-27

    We present a code to construct initial data for binary neutron star systems in which the stars are rotating. Our code, based on a formalism developed by Tichy, allows for arbitrary rotation axes of the neutron stars and is able to achieve rotation rates near rotational breakup. We compute the neutron star angular momentum through quasi-local angular momentum integrals. When constructing irrotational binary neutron stars, we find a very small residual dimensionless spin of $\\sim 2\\times 10^{-4}$. Evolutions of rotating neutron star binaries show that the magnitude of the stars' angular momentum is conserved, and that the spin- and orbit-precession of the stars is well described by post-Newtonian approximation. We demonstrate that orbital eccentricity of the binary neutron stars can be controlled to $\\sim 0.1\\%$. The neutron stars show quasi-normal mode oscillations at an amplitude which increases with the rotation rate of the stars.

  8. Methanol Masers and Star Formation

    E-Print Network [OSTI]

    A. M. Sobolev; A. B. Ostrovskii; M. S. Kirsanova; O. V. Shelemei; M. A. Voronkov; A. V. Malyshev

    2006-01-12

    Methanol masers which are traditionally divided into two classes provide possibility to study important parts of the star forming regions: Class~II masers trace vicinities of the massive YSOs while class~I masers are likely to trace more distant parts of the outflows where newer stars can form. There are many methanol transitions which produce observed masers. This allows to use pumping analysis for estimation of the physical parameters in the maser formation regions and its environment, for the study of their evolution. Extensive surveys in different masing transitions allow to conclude on the values of the temperatures, densities, dust properties, etc. in the bulk of masing regions. Variability of the brightest masers is monitored during several years. In some cases it is probably caused by the changes of the dust temperature which follow variations in the brightness of the central YSO reflecting the character of the accretion process. A unified catalogue of the class II methanol masers consisting of more than 500 objects is compiled. Analysis of the data shows that: physical conditions within the usual maser source vary considerably; maser brightness is determined by parameters of some distinguished part of the object - maser formation region; class II methanol masers are formed not within the outflows but in the regions affected by their propagation. It is shown that the "near" solutions for the kinematic distances to the sources can be used for statistical analysis. The luminosity function of the 6.7 GHz methanol masers is constructed. It is shown that improvement of the sensitivity of surveys can increase number of detected maser sources considerably.

  9. AGB stars and presolar grains

    SciTech Connect (OSTI)

    Busso, M.; Trippella, O. [INFN and University of Perugia, Perugia (Italy); Maiorca, E. [INAF - Arcetri Astrophysical Observatory, Firenze, Italy and INFN - Section of Perugia, Perugia (Italy); Palmerini, S. [Departamento de Fìsica Teòrica y del Cosmsos, Universidad de Granada, Granada (Spain)

    2014-05-09

    Among presolar materials recovered in meteorites, abundant SiC and Al{sub 2}O{sub 3} grains of AGB origins were found. They showed records of C, N, O, {sup 26}Al and s-element isotopic ratios that proved invaluable in constraining the nucleosynthesis models for AGB stars [1, 2]. In particular, when these ratios are measured in SiC grains, they clearly reveal their prevalent origin in cool AGB circumstellar envelopes and provide information on both the local physics and the conditions at the nucleosynthesis site (the H- and He-burning layers deep inside the structure). Among the properties ascertained for the main part of the SiC data (the so-called mainstream ones), we mention a large range of {sup 14}N/{sup 15}N ratios, extending below the solar value [3], and {sup 12}C/{sup 13}C ratios ? 30. Other classes of grains, instead, display low carbon isotopic ratios (? 10) and a huge dispersion for N isotopes, with cases of large {sup 15}N excess. In the same grains, isotopes currently feeded by slow neutron captures reveal the characteristic pattern expected from this process at an efficiency slightly lower than necessary to explain the solar main s-process component. Complementary constraints can be found in oxide grains, especially Al{sub 2}O{sub 3} crystals. Here, the oxygen isotopes and the content in {sup 26}Al are of a special importance for clarifying the partial mixing processes that are known to affect evolved low-mass stars. Successes in modeling the data, as well as problems in explaining some of the mentioned isotopic ratios through current nucleosynthesis models are briefly outlined.

  10. The WISE View of RV Tauri Stars

    E-Print Network [OSTI]

    Gezer, I; Bozkurt, Z; De Smedt, K; Kamath, D; Hillen, M; Manick, R

    2015-01-01

    We present a detailed study based on infrared photometry of all Galactic RV Tauri stars from the General Catalogue of Variable Stars (GCVS). RV Tauri stars are the brightest among the population II Cepheids. They are thought to evolve away from the asymptotic giant branch (AGB) towards the white dwarf domain. IRAS detected several RV Tauri stars because of their large IR excesses and it was found that they occupy a specific region in the [12] - [25], [25] - [60] IRAS two-colour diagram. We used the all sky survey of WISE to extend these studies and compare the infrared properties of all RV Tauri stars in the GCVS with a selected sample of post-AGB objects with the goal to place the RV Tauri pulsators in the context of post-AGB evolution. Moreover, we correlated the IR properties of both the RV Tauri stars and the comparison sample with other observables like binarity and the presence of a photospheric chemical anomaly called depletion. We find that Galactic RV Tauri stars display a range of infrared propertie...

  11. Magnetic fields of HgMn stars

    E-Print Network [OSTI]

    Hubrig, S; Ilyin, I; Korhonen, H; Schoeller, M; Savanov, I; Arlt, R; Castelli, F; Curto, G Lo; Briquet, M; Dall, T H

    2012-01-01

    The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. We re-analyse available spectropolarimetric material by applying the moment technique on spectral lines of inhomogeneously distributed elements separately. Furthermore, we present new determinations of the mean longitudinal magnetic field for the HgMn star HD65949 and the hotter analog of HgMn stars, the PGa star HD19400, using FORS2 installed at the VLT. We also give new measurements of the eclipsing system AR Aur with a primary star of HgMn peculiarity which were obtained with the SOFIN spectropolarimeter installed at the Nordic Optical Telescope. We downloaded from the ESO archive the publically available HARPS spectra for eight HgMn stars and one normal and one superficially normal B-type star obtained in 2010. The application of the moment technique to the HARPS and SOFIN spectra allowed us to study the presence of the longitudina...

  12. The Evolution of Compact Binary Star Systems

    E-Print Network [OSTI]

    Konstantin Postnov; Lev Yungelson

    2014-03-21

    We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Mergings of compact binary stars are expected to be the most important sources for the forthcoming gravitational-wave (GW) astronomy. In the first part of the review, we discuss observational manifestations of close binary stars with NS and/or black components and their merger rate, crucial points in the formation and evolution of compact stars in binary systems, including the treatment of the natal kicks which NSs and BHs acquire during the core collapse of massive stars and the common envelope phase of binary evolution, which are most relevant to the merging rates of NS-NS, NS-BH and BH-BH binaries. The second part of the review is devoted mainly to formation and evolution of binary WDs and their observational manifestations, including their role as progenitors of cosmologically important thermonuclear SN Ia. We also consider AM CVn-stars which are thought to be the best verification binary GW sources for future low-frequency GW space interferometers.

  13. Static exteriors for nonstatic braneworld stars

    E-Print Network [OSTI]

    J. Ponce de Leon

    2008-03-04

    We study possible static non-Schwarzschild exteriors for nonstatic spherically symmetric stars in a Randall $&$ Sundrum type II braneworld scenario. Thus, the vacuum region outside the surface of a star is assumed to be a static solution to the equation $^{(4)}R = 0$, where $^{(4)}R $ is the scalar curvature of the 4-dimensional Ricci tensor with spherical symmetry. Firstly, we show that for nonstatic spheres the standard matching conditions are much more restrictive than for static ones; they lead to a specific requirement on the vacuum region outside of a nonstatic star, that is absent in the case of static stars. Secondly, without making any assumption about the bulk, or the material medium inside the star, we prove the following theorem on the brane: for {\\it any} nonstatic spherical star, without rotation, there are only two possible static exteriors; these are the Schwarzschild and the "Reissner-Nordstr{\\"o}m-like" exteriors. This is quite distinct from the case of stars in hydrostatic equilibrium which admit a much larger family of non-Schwarzschild static exteriors.

  14. Anisotropic pressure and hyperons in neutron stars

    E-Print Network [OSTI]

    A. Sulaksono

    2014-12-23

    We study the effects of anisotropic pressure on properties of the neutron stars with hyperons inside its core within the framework of extended relativistic mean field. It is found that the main effects of anisotropic pressure on neutron star matter is to increase the stiffness of the equation of state, which compensates for the softening of the EOS due to the hyperons. The maximum mass and redshift predictions of anisotropic neutron star with hyperonic core are quite compatible with the result of recent observational constraints if we use the parameter of anisotropic pressure model $h \\le 0.8$[1] and $\\Lambda \\le -1.15$ [2]. The radius of the corresponding neutron star at $M$=1.4 $M_\\odot$ is more than 13 km, while the effect of anisotropic pressure on the minimum mass of neutron star is insignificant. Furthermore, due to the anisotropic pressure in the neutron star, the maximum mass limit of higher than 2.1 $M_\\odot$ cannot rule out the presence of hyperons in the neutron star core.

  15. SUPERMASSIVE DARK STARS: DETECTABLE IN JWST

    SciTech Connect (OSTI)

    Freese, Katherine; Ilie, Cosmin; Spolyar, Douglas; Valluri, Monica; Bodenheimer, Peter

    2010-06-20

    The first phase of stellar evolution in the history of the universe may be dark stars (DSs), powered by dark matter (DM) heating rather than by nuclear fusion. Weakly interacting massive particles (WIMPs), which may be their own antipartners, collect inside the first stars and annihilate to produce a heat source that can power the stars for millions to billions of years. In this paper, we show that these objects can grow to be supermassive dark stars (SMDSs) with masses {approx_gt}(10{sup 5}-10{sup 7}) M{sub sun}. The growth continues as long as DM heating persists, since DSs are large and cool (surface temperature {approx_lt}5 x 10{sup 4} K) and do not emit enough ionizing photons to prevent further accretion of baryons onto the star. The DM may be provided by two mechanisms: (1) gravitational attraction of DM particles on a variety of orbits not previously considered and (2) capture of WIMPs due to elastic scattering. Once the DM fuel is exhausted, the SMDS becomes a heavy main-sequence star; these stars eventually collapse to form massive black holes (BHs) that may provide seeds for supermassive BHs in the universe. SMDSs are very bright, with luminosities exceeding (10{sup 9}-10{sup 11}) L{sub sun}. We demonstrate that for several reasonable parameters, these objects will be detectable with the James Webb Space Telescope. Such an observational discovery would confirm the existence of a new phase of stellar evolution powered by DM.

  16. Beryllium abundances in stars hosting giant planets

    E-Print Network [OSTI]

    N. C. Santos; R. J. Garcia Lopez; G. Israelian; M. Mayor; R. Rebolo; A. Garcia-Gil; M. R. Perez de Taoro; S. Randich

    2002-02-25

    We have derived beryllium abundances in a wide sample of stars hosting planets, with spectral types in the range F7V-K0V, aimed at studying in detail the effects of the presence of planets on the structure and evolution of the associated stars. Predictions from current models are compared with the derived abundances and suggestions are provided to explain the observed inconsistencies. We show that while still not clear, the results suggest that theoretical models may have to be revised for stars with Teff<5500K. On the other hand, a comparison between planet host and non-planet host stars shows no clear difference between both populations. Although preliminary, this result favors a ``primordial'' origin for the metallicity ``excess'' observed for the planetary host stars. Under this assumption, i.e. that there would be no differences between stars with and without giant planets, the light element depletion pattern of our sample of stars may also be used to further investigate and constraint Li and Be depletion mechanisms.

  17. Perceptions of and by lonely people in initial social interaction 

    E-Print Network [OSTI]

    Christensen, Peter Niels

    1996-01-01

    rated themselves and others on eleven personal characteristics, such as physical attractiveness, social skills, and anxiety. Each member also judged how he or she thought each other group member saw him or her on the eleven variables (meta...

  18. Lone Tree, Colorado: Energy Resources | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QAsource History View NewTexas:Montezuma, Arizona:Oregon: EnergyLloyd, New York:Lodi,NorthLomita,Londonderry,Tree,

  19. Discovery of magnetic fields in the beta Cephei star xi^1 CMa and in several Slowly Pulsating B stars

    E-Print Network [OSTI]

    S. Hubrig; M. Briquet; M. Schoeller; P. De Cat; G. Mathys; C. Aerts

    2006-04-12

    We present the results of a magnetic survey of a sample of eight beta Cephei stars and 26 Slowly Pulsating B stars with FORS1 at the VLT. A weak mean longitudinal magnetic field of the order of a few hundred Gauss is detected in the beta Cephei star xi^1 CMa and in 13 SPB stars. The star xi^1 CMa becomes the third magnetic star among the beta Cephei stars. Before our study, the star zeta Cas was the only known magnetic SPB star. All magnetic SPB stars for which we gathered several magnetic field measurements show a field that varies in time. We do not find a relation between the evolution of the magnetic field with stellar age in our small sample. Our observations imply that beta Cephei stars and SPBs can no longer be considered as classes of non-magnetic pulsators, but the effect of the fields on the oscillation properties remains to be studied.

  20. Comment on "Three-dimensional hydrodynamic simulations of the combustion of a neutron star into a quark star"

    E-Print Network [OSTI]

    M. I. Krivoruchenko; B. V. Martemyanov

    2015-03-04

    If strange matter is absolutely stable, the ordinary nuclei decay to strangelets, while neutron stars convert into strange stars. Lifetimes of the ordinary nuclei are constrained experimentally to be above $\\sim 10^{33}$ years, while lifetimes of the metastable neutron stars depend on the neutron star masses and can exceed the age of the Universe. As a consequence, the neutron stars and the strange stars can coexist in the Universe. We point out that numerical simulations of the conversion of neutron stars to strange stars, performed by M. Herzog and F. K. Roepke in Phys. Rev. D 84, 083002 (2011) [arXiv:1109.0539], are focused on a region in the parameter space of strange matter, in which low-mass neutron stars and strange stars are coexistent, whereas massive neutron stars are unstable and short lived on an astronomical timescale.

  1. Gravitational Waves from Neutron Stars: A Review

    E-Print Network [OSTI]

    Paul D. Lasky

    2015-08-26

    Neutron stars are excellent emitters of gravitational waves. Squeezing matter beyond nuclear densities invites exotic physical processes, many of which violently transfer large amounts of mass at relativistic velocities, disrupting spacetime and generating copious quantities of gravitational radiation. I review mechanisms for generating gravitational waves with neutron stars. This includes gravitational waves from radio and millisecond pulsars, magnetars, accreting systems and newly born neutron stars, with mechanisms including magnetic and thermoelastic deformations, various stellar oscillation modes and core superfluid turbulence. I also focus on what physics can be learnt from a gravitational wave detection, and where additional research is required to fully understand the dominant physical processes at play.

  2. Hypervelocity Stars and the Galactic Center

    E-Print Network [OSTI]

    Warren R. Brown

    2008-11-04

    A summary of the current knowledge on hypervelocity stars (HVSs). HVSs are fascinating because their properties are linked to Sgr A* and the stellar environment of the Galactic Center. Observing the distribution of HVSs can address: 1) the nature of the black hole ejection mechanism, 2) the in-fall history of stars onto Sgr A*, 3) the types of stars orbiting Sgr A*, and 4) a unique measurement the shape of the Galaxy's dark matter potential. The challenge to observers is to find new HVSs and strengthen the connection between HVSs and the Galactic Center.

  3. The evolution of very massive stars

    E-Print Network [OSTI]

    H. Belkus; J. Van Bever; D. Vanbeveren

    2007-01-11

    Core collapse of dense massive star clusters is unavoidable and this leads to the formation of massive objects, with a mass up to 1000 $\\msun$ and even larger. When these objects become stars, stellar wind mass loss determines their evolution and final fate, and decides upon whether they form black holes (with normal mass or with intermediate mass) or explode as a pair instability supernova. In the present paper, we discuss the evolution of very massive stars and we present a convenient evolution recipe that can be implemented in a gravitational N-body code to study the dynamics of dense massive clusters.

  4. Gravitational Waves from Neutron Stars: A Review

    E-Print Network [OSTI]

    Lasky, Paul D

    2015-01-01

    Neutron stars are excellent emitters of gravitational waves. Squeezing matter beyond nuclear densities invites exotic physical processes, many of which violently transfer large amounts of mass at relativistic velocities, disrupting spacetime and generating copious quantities of gravitational radiation. I review mechanisms for generating gravitational waves with neutron stars. This includes gravitational waves from radio and millisecond pulsars, magnetars, accreting systems and newly born neutron stars, with mechanisms including magnetic and thermoelastic deformations, various stellar oscillation modes and core superfluid turbulence. I also focus on what physics can be learnt from a gravitational wave detection, and where additional research is required to fully understand the dominant physical processes at play.

  5. Lithium abundances in exoplanet-hosts stars

    E-Print Network [OSTI]

    M. Castro; S. Vauclair; O. Richard; N. C. Santos

    2008-03-20

    Exoplanet-host stars (EHS) are known to present surface chemical abundances different from those of stars without any detected planet (NEHS). EHS are, on the average, overmetallic compared to the Sun. The observations also show that, for cool stars, lithium is more depleted in EHS than in NEHS. The overmetallicity of EHS may be studied in the framework of two different scenarii. We have computed main sequence stellar models with various masses, metallicities and accretion rates. The results show different profiles for the lithium destruction according to the scenario. We compare these results to the spectroscopic observations of lithium.

  6. KNOW THE STAR, KNOW THE PLANET. I. ADAPTIVE OPTICS OF EXOPLANET HOST STARS

    SciTech Connect (OSTI)

    Roberts, Lewis C.; Turner, Nils H.; Ten Brummelaar, Theo A.; Mason, Brian D.; Hartkopf, William I. E-mail: nils@chara-array.org E-mail: bdm@usno.navy.mil

    2011-11-15

    The results of an adaptive optics survey of exoplanet host stars for stellar companions are presented. We used the Advanced Electro-Optical System telescope and its adaptive optics system to collect deep images of the stars in the I band. Sixty-two exoplanet host stars were observed and fifteen multiple star systems were resolved. Of these eight are known multiples, while seven are new candidate binaries. For all binaries, we measured the relative astrometry of the pair and the differential magnitude in the I band. We improved the orbits of HD 19994 and {tau} Boo. These observations will provide improved statistics on the duplicity of exoplanet host stars and provide an increased understanding of the dynamics of known binary star exoplanet hosts.

  7. Combustion of a neutron star into a strange quark star: The neutrino signal

    E-Print Network [OSTI]

    G. Pagliara; M. Herzog; F. K. Roepke

    2013-05-02

    There are strong indications that the process of conversion of a neutron star into a strange quark star proceeds as a strong deflagration implying that in a few milliseconds almost the whole star is converted. Starting from the three-dimensional hydrodynamic simulations of the combustion process which provide the temperature profiles inside the newly born strange star, we calculate for the first time the neutrino signal that is to be expected if such a conversion process takes place. The neutrino emission is characterized by a luminosity and a duration that is typical for the signal expected from protoneutron stars and represents therefore a powerful source of neutrinos which could be possibly directly detected in case of events occurring close to our Galaxy. We discuss moreover possible connections between the birth of strange stars and explosive phenomena such as supernovae and gamma-ray-bursts.

  8. Combustion of a neutron star into a strange quark star: the neutrino signal

    E-Print Network [OSTI]

    Pagliara, G; Ropke, F K

    2013-01-01

    There are strong indications that the process of conversion of a neutron star into a strange quark star proceeds as a strong deflagration implying that in a few milliseconds almost the whole star is converted. Starting from the three-dimensional hydrodynamic simulations of the combustion process which provide the temperature profiles inside the newly born strange star, we calculate for the first time the neutrino signal that is to be expected if such a conversion process takes place. The neutrino emission is characterized by a luminosity and a duration that is typical for the signal expected from protoneutron stars and represents therefore a powerful source of neutrinos which could be possibly directly detected in case of events occurring close to our galaxy. We discuss moreover possible connections between the birth of strange stars and explosive phenomena such as Supernovae and Gamma-Ray-Bursts.

  9. Magnetic Channeling of Radiatively Driven Hot-Star Winds

    E-Print Network [OSTI]

    Owocki, Stanley P.

    in magnetic Bp stars like sigma Ori C. We conclude with an outlook for the general role of magnetic fields that of the solar wind. Their high surface temperatures mean that such stars lack the hydrogen recombination convection zone that induces the magnetic dynamo cycle of cooler, solar type stars [e.g., 3]. Such stars have

  10. Ralf Klessen: Lecture 2: 27.12.2006 Star Formation

    E-Print Network [OSTI]

    Klessen,Ralf

    efficiencyefficiency? How do globalglobal properties of the galaxy influence star formation (a locallocal process

  11. X-ray Emission from the Winds of Massive Stars

    E-Print Network [OSTI]

    Cohen, David

    X-ray Emission from the Winds of Massive Stars David Cohen Department of Physics & Astronomy-driven stellar winds are a characteristic of massive stars NGC 6888 Crescent Nebula - Tony Hallas #12;NGC 6888 Crescent Nebula - Tony Hallas O star - source of wind bubble: ~1 arc second instrumental resolution; star

  12. An Observational Study of Post-Asymptotic Giant Branch Stars

    E-Print Network [OSTI]

    helium-normal or helium-rich photospheres. 2. the detection and measurement of s-process element-AGB stars. We detected helium enrichment in the post-AGB stars Hen3-1428 and LSS4331. We did not detect any such as that seen in the extreme helium stars (EHes). High-resolution ´echelle spectra of several post-AGB stars

  13. Blue Straggler Stars in Galactic Open Clusters and the effect of field star contamination

    E-Print Network [OSTI]

    G. Carraro; R. A. Vazquez; A. Moitinho

    2008-02-25

    We investigate the distribution of Blue Straggler stars in the field of three open star clusters. The main purpose is to highlight the crucial role played by general Galactic disk fore-/back-ground field stars, which are often located in the same region of the Color Magnitude Diagram as Blue Straggler stars. We analyze photometry taken from the literature of 3 open clusters of intermediate/old age rich in Blue Straggler stars, and which are projected in the direction of the Perseus arm, and study their spatial distribution and the Color Magnitude Diagram. As expected, we find that a large portion of the Blue Straggler population in these clusters are simply young field stars belonging to the spiral arm. This result has important consequences on the theories of the formation and statistics of Blue Straggler stars in different population environments: open clusters, globular clusters or dwarf galaxies. As previously emphasized by many authors, a detailed membership analysis is mandatory before comparing the Blue Straggler population in star clusters against theoretical models. Moreover, these sequences of young field stars (blue plumes) are potentially powerful tracers of Galactic structure which require further consideration.

  14. Double Neutron Stars: Evidence For Two Different Neutron-Star Formation Mechanisms

    E-Print Network [OSTI]

    E. P. J. van den Heuvel

    2007-04-26

    Six of the eight double neutron stars known in the Galactic disk have low orbital eccentricities (neutron stars received only very small velocity kicks at birth. This is similar to the case of the B-emission X-ray binaries, where a sizable fraction of the neutron stars received hardly any velocity kick at birth (Pfahl et al. 2002). The masses of the second-born neutron stars in five of the six low-eccentricity double neutron stars are remarkably low (between 1.18 and 1.30 Msun). It is argued that these low-mass, low-kick neutron stars were formed by the electron-capture collapse of the degenerate O-Ne-Mg cores of helium stars less massive than about 3.5 Msun, whereas the higher-mass, higher kick-velocity neutron stars were formed by the collapses of the iron cores of higher initial mass. The absence of low-velocity single young radio pulsars (Hobbs et al. 2005) is consistent with the model proposed by Podsiadlowski et al. (2004), in which the electron-capture collapse of degenerate O-Ne-Mg cores can only occur in binary systems, and not in single stars.

  15. Relativistic harmonic oscillator model for quark stars

    E-Print Network [OSTI]

    Vishnu M. Bannur

    2008-10-06

    The relativistic harmonic oscillator (RHO) model of hadrons is used to study quark stars. The mass-radius relationship is obtained and compared with bag model of quark star, using Tolman-Oppenheimer-Volkoff equation. In this model, the outward degenerate pressure due to discrete Landau levels and Landau degeneracy balances the inward gravitational pressure. Where as in bag model the degenerate pressure is due to the standard continuum levels which balances the combined inward pressure due to gravitation and bag pressure. So in RHO model, the confinement effect is included in the degenerate pressure. We found a qualitative similarity, but quantitative differences in mass-radius relationship of quark stars in these two models. Masses and radii are relatively larger and the central energy densities, required for stable quark stars, are lower in RHO model than that of bag model.

  16. Midea: ENERGY STAR Referral (MWF-08CR)

    Broader source: Energy.gov [DOE]

    DOE referred the matter of Westpointe-brand room air conditioner model MWF-08CR to the EPA for appropriate action after DOE testing showed that the model does not meet the ENERGY STAR specification.

  17. ENERGY STAR® Solid-State Lighting Workshop

    Broader source: Energy.gov [DOE]

    Workshop Purpose: To prepare manufacturers for the launch of the ENERGY STAR SSL program in late September by sharing information on the state of the SSL market, status of relevant test procedures,...

  18. Axion Stars and Fast Radio Bursts

    E-Print Network [OSTI]

    A. Iwazaki

    2014-10-23

    We show that fast radio bursts arise from collisions between axion stars and neutron stars. The bursts are emitted in the atmosphere of the neutron stars. The observed frequencies of the bursts are given by the axion mass $m_a$ such as $m_a/2\\pi\\simeq 1.4\\,\\mbox{GHz}\\,\\big(m_a/(6\\times 10^{-6}\\mbox{eV})\\big)$. From the event rate $\\sim 10^{-3}$ per year in a galaxy, we can determine the mass $\\sim 10^{-11}M_{\\odot}$ of the axion stars. Using these values we can explain short durations ( $\\sim $ms ) and amount of radiation energies ( $\\sim 10^{43}$GeV ) of the bursts.

  19. ASKO: ENERGY STAR Referral (D5122XXLB)

    Broader source: Energy.gov [DOE]

    DOE referred the matter of ASKO dishwasher model D5122XXLB to the EPA for appropriate action after DOE testing showed that the model does not meet the ENERGY STAR specification.

  20. Whirlpool: ENERGY STAR Referral (ASD2524VE)

    Broader source: Energy.gov [DOE]

    DOE referred the matter of Whirlpool's Amana-brand dishwasher model ASD2524VE to the EPA for appropriate action after DOE testing showed that the model does not meet the ENERGY STAR specification.

  1. Hybrid Pulsators -- Pulsating Stars with Multiple Identities

    E-Print Network [OSTI]

    Zhou, A -Y

    2015-01-01

    We have carried out a statistic survey on the pulsating variable stars with multiple identities. These stars were identified to exhibit two types of pulsation or multiple light variability types in the literature, and are usually called hybrid pulsators. We extracted the hybrid information based on the Simbad database. Actually, all the variables with multiple identities are retrieved. The survey covers various pulsating stars across the Hertzsprung-Russell diagram. We aim at giving a clue in selecting interesting targets for further observation. Hybrid pulsators are excellent targets for asteroseismology. An important implication of such stars is their potential in advancing the theories of both stellar evolution and pulsation. By presenting the statistics, we address the open questions and prospects regarding current status of hybrid pulsation studies.

  2. Samsung: ENERGY STAR Referral (RF26VAB)

    Broader source: Energy.gov [DOE]

    DOE referred the matter of Samsung refrigerator-freezer model RF26VAB to the EPA for appropriate action after DOE testing showed that the model does not meet the ENERGY STAR specification.

  3. The Maximum Mass of a Neutron Star

    E-Print Network [OSTI]

    Vassiliki Kalogera; Gordon Baym

    1996-08-11

    Observational identification of black holes as members of binary systems requires the knowledge of the upper limit on the gravitational mass of a neutron star. We use modern equations of state for neutron star matter, fitted to experimental nucleon-nucleon scattering data and the properties of light nuclei, to calculate, within the framework of Rhoades & Ruffini (1974), the minimum upper limit on a neutron star mass. Regarding the equation of state as valid up to twice nuclear matter saturation density, rho_{nm}, we obtain a secure upper bound on the neutron star mass equal to 2.9 solar masses. We also find that in order to reach the lowest possible upper bound of 2.2 solar masses, we need understand the physical properties of neutron matter up to a density of about 4 times rho_{nm}.

  4. Neutron rich nuclei and neutron stars

    E-Print Network [OSTI]

    C. J. Horowitz

    2013-03-01

    The PREX experiment at Jefferson Laboratory measures the neutron radius of 208Pb with parity violating electron scattering in a way that is free from most strong interaction uncertainties. The 208Pb radius has important implications for neutron rich matter and the structure of neutron stars. We present first PREX results, describe future plans, and discuss a follow on measurement of the neutron radius of 48Ca. We review radio and X-ray observations of neutron star masses and radii. These constrain the equation of state (pressure versus density) of neutron rich matter. We present a new energy functional that is simultaneously fit to both nuclear and neutron star properties. In this approach, neutron star masses and radii constrain the energy of neutron matter. This avoids having to rely on model dependent microscopic calculations of neutron matter. The functional is then used to predict the location of the drip lines and the properties of very neutron rich heavy nuclei.

  5. Neutron stars in Einstein-aether theory

    E-Print Network [OSTI]

    Christopher Eling; Ted Jacobson; M. Coleman Miller

    2009-12-06

    As current and future experiments probe strong gravitational regimes around neutron stars and black holes, it is desirable to have theoretically sound alternatives to general relativity against which to test observations. Here we study the consequences of one such generalization, Einstein-aether theory, for the properties of non-rotating neutron stars. This theory has a parameter range that satisfies all current weak-field tests. We find that within this range it leads to lower maximum neutron star masses, as well as larger surface redshifts at a particular mass, for a given nuclear equation of state. For non-rotating black holes and neutron stars, the innermost stable circular orbit is only slightly modified in this theory.

  6. Michael Liebreich (Energy All Stars Presentation)

    Office of Energy Efficiency and Renewable Energy (EERE)

    Michael Liebreich, CEO of Bloomberg New Energy Finance, delivered this presentation on the energy economy at the Energy All Stars event on January 19, 2013, at the US Department of Energy in...

  7. William Fowler and Elements in the Stars

    Office of Scientific and Technical Information (OSTI)

    the chemical elements inside stars; the Big Bang origin of the universe; and the current Dark Matter debate over what most of the universe is made of. "It is a remarkable fact...

  8. ENERGY STAR Webinar: Portfolio Manager 101

    Office of Energy Efficiency and Renewable Energy (EERE)

    Join us as we introduce and demonstrate the core functionality of EPA’s new ENERGY STAR Portfolio Manager tool. Attendees will learn how to: navigate the new Portfolio Manager; add a property and...

  9. EPA ENERGY STAR Webcast: Portfolio Manager 101

    Office of Energy Efficiency and Renewable Energy (EERE)

    Join us as we introduce and demonstrate the core functionality of EPA’s new ENERGY STAR Portfolio Manager tool. Attendees will learn how to: navigate the new Portfolio Manager; add a property and...

  10. ENERGY STAR Webinar: Portfolio Manager 201

    Office of Energy Efficiency and Renewable Energy (EERE)

    This webinar continues on the U.S. Environmental Protection Agency's (EPA's) new ENERGY STAR Portfolio Manager tool. Attendees will learn the more advanced functionalities, such as managing and...

  11. EPA ENERGY STAR Webcast- Portfolio Manager 101

    Office of Energy Efficiency and Renewable Energy (EERE)

    Join us as we introduce and demonstrate the core functionality of EPA’s new ENERGY STAR Portfolio Manager tool. Attendees will learn how to: navigate the new Portfolio Manager; add a property and...

  12. ENERGY STAR Webinar: Portfolio Manager 301

    Office of Energy Efficiency and Renewable Energy (EERE)

    Hosted by the U.S. Environmental Protection Agency (EPA) ENERGY STAR, this webinar will show attendees how to upload templates to update property data, setting goals and targets to plan energy...

  13. EPA ENERGY STAR Webcast- Portfolio Manager 201

    Office of Energy Efficiency and Renewable Energy (EERE)

    Continue to learn about EPA’s new ENERGY STAR Portfolio Manager tool, with a deeper dive into more advanced functionalities such as: managing and tracking changes to your property uses over time;...

  14. EPA ENERGY STAR Webcast: Portfolio Manager 201

    Office of Energy Efficiency and Renewable Energy (EERE)

    Continue to learn about EPA’s new ENERGY STAR Portfolio Manager tool, with a deeper dive into more advanced functionalities such as: managing and tracking changes to your property uses over time;...

  15. The Number of Planets Around Stars

    E-Print Network [OSTI]

    Noam Soker

    1997-06-24

    Based on the large number of elliptical planetary nebulae I argue that about 55 per cent of all progenitors of planetary nebulae have planets around them. The planets spin up the stars when the later evolve along the red giant branch or along the asymptotic giant branch. The arguments, which were presented in several of my earlier works, and are summarized in the paper, suggest that the presence of four gas-giant planets in the solar system is the generality rather than the exception. I here continue and: (1) examine the possibility of detecting signatures of surviving Saturn-like planets inside planetary nebulae, and, (2) propose a model by which the second parameter of the horizontal branch, which determines the distribution of horizontal branch stars in the HR diagram, is the presence of planets. A red giant branch star that interacts with a planet will lose a large fraction of its envelope and will become a blue horizontal branch star.

  16. Nucleosynthesis in asymptotic giant branch stars

    SciTech Connect (OSTI)

    El Eid, Mounib F., E-mail: meid@aub.edu.lb [American University of Beirut, Department of Physics, P.O. Box 11-0236, Riad El-Solh, Beirut (Lebanon)

    2014-05-09

    The nucleosynthesis in asymptotic giant branch stars (briefly: AGB)is a challenging and fascinating subject in the theory of stellar evolution and important for observations as well. This is because about of half the heavy elements beyond iron are synthesized during thermal pulsation phases of these stars. Furthermore, the understanding of the production of the heavy elements and some light elements like carbon and fluorine represent a powerful tool to get more insight into the internal structure of these stars. The diversity of nuclear processing during the AGB phases may also motivate experimental activities in measuring important nuclear reactions. In this contribution, we emphasize several interesting feature of the nucleosynthesis in AGB stars which still needs further elaboration especially from theoretical point of view.

  17. Sue Tierney (Energy All Stars Presentation)

    Broader source: Energy.gov [DOE]

    Sue Tierney delivered this presentation" The Future of Energy: Toward the 21st Century Energy System We Need (With an Eye on the Rear View Mirror)" at the Energy All Stars event on January 19, 2013...

  18. Top 10 Problems on Massive Stars

    E-Print Network [OSTI]

    Cassio Barbosa; Donald Figer

    2005-10-18

    We have asked a number of researchers to compile their lists of the top 10 problems in the field of massive stars. This paper is a compilation of these lists. We attempted to survey observers and theorists and those studying all evolutionary stages in the lives of massive stars. Each list reflects the proposer's personal point of view, but hopefully, this compilation will motivate new young astronomers and begin a new series of discussion.

  19. STAR FORMATION IN TWO LUMINOUS SPIRAL GALAXIES

    SciTech Connect (OSTI)

    Hunter, Deidre A.; Ashburn, Allison; Wright, Teresa; Elmegreen, Bruce G.; Rubin, Vera C.; Józsa, Gyula I. G.; Struve, Christian

    2013-10-01

    We examined star formation in two very luminous (M{sub V} = –22 to –23) Sc-type spiral galaxies, NGC 801 and UGC 2885, using ultra-deep H? images. We combine these H? images with UBV and Two-Micron All-Sky Survey JHK images and H I maps to explore the star formation characteristics of disk galaxies at high luminosity. H? traces star formation in these galaxies to 4-6 disk scale lengths, but the lack of detection of H? further out is likely due to the loss of Lyman continuum photons. Considering gravitational instabilities alone, we find that the gas and stars in the outer regions are marginally stable in an average sense, but considering dissipative gas and radial and azimuthal forcing, the outer regions are marginally unstable to forming spiral arms. Star formation is taking place in spiral arms, which are regions of locally higher gas densities. Furthermore, we have traced smooth exponential stellar disks over four magnitudes in V-band surface brightness and 4-6 disk scale lengths, in spite of a highly variable gravitational instability parameter. Thus, gravitational instability thresholds do not seem relevant to the stellar disk. One possibility for creating an exponential disk is that the molecular cloud densities and star formation rates have exponential profiles and this fact forces the stellar disk to build up such a profile. Another possibility is that the stellar disk is continuously adjusted to an exponential shape regardless of the star formation profile, for example, through global dynamical processes that scatter stars. However, such scattering processes are only known to operate in spiral systems, in which case they cannot explain the same dilemma of smooth exponential disks observed in dwarf irregular galaxies.

  20. The Hubness Phenomenon: Fact or Artifact?

    E-Print Network [OSTI]

    Borgelt, Christian

    for Soft Computing, c/ Gonzalo Gutiâ??errez Quirâ??os s/n, E­33600 Mieres (Asturias), Spain, christian

  1. The Hubness Phenomenon: Fact or Artifact?

    E-Print Network [OSTI]

    Borgelt, Christian

    for Soft Computing, c/ Gonzalo Guti´errez Quir´os s/n, E-33600 Mieres (Asturias), Spain, christian

  2. High Impact Technology Hub- Host a Site

    Broader source: Energy.gov [DOE]

    We are always looking for partners to host technology demonstrations.  Host site participants receive recognition by the Department of Energy, site applicability analysis as well as the opportunity...

  3. Midwest Big Data Hub Edward Seidel

    E-Print Network [OSTI]

    -enabled Transformation of Science Astronomy 1500- 2000: · Single scientist looks through telescope · Record KB of data in notebook · Require reproducibility Sloan Digital Sky Survey 2000+ · Record data for decade (40TB) · Serve of chemists and materials scientists developing a "materials genome" · Industry access can speed product

  4. The Hub of Innovation for American Housing

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    New Homes: Recognizes builders with significantly above code performance INFRASTRUCTURE: HUD: Integrate proven innovations in low income housing programs MARKET LEADERS: Home...

  5. BUILDING A CO2 STORAGE HUB IN

    E-Print Network [OSTI]

    Painter, Kevin

    , once at the forefront of this innovative technology that can give us clean energy from abundant fossil technology we have in the battle to reduce CO2 emissions from power and industrial sources. Without it we and global reliance on low-cost energy from coal and gas shows no sign of diminishing, the time has come

  6. Malicious Hubs: Detecting Abnormally Malicious Autonomous Systems

    E-Print Network [OSTI]

    Gupta, Minaxi

    security or those that harbor cybercrime. I. INTRODUCTION The Internet is plagued by malicious activity is not necessarily evenly distributed across the Internet: some networks may employ lax security, resulting in large populations of compromised machines, while others may tightly secure their network and not have any malicious

  7. Solent Enterprise Hub | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page| Open Energy Information Serbia-Enhancing Capacity forSiliciumEnergy Inc Jump to: navigation,SolastaSolco

  8. Reading Enterprise Hub | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page onRAPID/Geothermal/Exploration/Colorado <RAPID/Geothermal/WaterEnergy MarketingNew Hampshire:

  9. Botswana Innovation Hub | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIX E LISTStar Energy LLC JumpBiossence JumpJersey Logo: Boston College Name: BostonBotswana

  10. SolarHub | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION JEnvironmental Jump to:EA EIS ReportEurope GmbH JumpSloughInfra

  11. High Impact Technology Hub | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on Delicious Rank EERE:FinancingPetroleum12,ExecutiveFinancing ProgramsDepartment of¡ ¢HelpHighJian Li,1and

  12. Presentation: Hubs+ Report | Department of Energy

    Energy Savers [EERE]

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on DeliciousMathematicsEnergyInterested PartiesBuilding energyDepartmentNEA-2011-03Presentation: DOE

  13. The Department of Energy's Energy Innovation Hubs

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on Delicious RankADVANCEDInstallers/ContractorsPhotovoltaicsState of Pennsylvania OAS-RA-L-11-11 September 2011

  14. The Hub of Innovation for American Housing

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on Delicious RankADVANCEDInstallers/ContractorsPhotovoltaicsState of Pennsylvania U.S.The First FiveThe

  15. Energy Efficient Buildings Hub | Department of Energy

    Broader source: Energy.gov (indexed) [DOE]

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of Natural GasAdjustmentsShirley Ann JacksonDepartment ofOffice ofofWind Projects |EnergyAll 50BatteriesitsEnergyofThis

  16. Fuels From Sunlight Hub | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on Delicious Rank EERE: Alternative Fuelsof Energy Services »Information Resources » FuelDepartment of

  17. Critical Materials Hub | Department of Energy

    Broader source: Energy.gov (indexed) [DOE]

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of Natural GasAdjustmentsShirleyEnergy A plug-in electric vehicle (PEV)Day-June2012environment 3D printer laser deposition

  18. Isotopic Anomalies in CP Stars: Helium, Mercury, Platinum, and Calcium

    E-Print Network [OSTI]

    C. R. Cowley; S. Hubrig; F. Castelli

    2007-11-15

    We review the classical observational results for isotopic abundance variations for several elements in CP stars. We concentrate on the "newest" anomaly, in calcium. The cosmically very rare isotope, Ca-48 can rival and even dominate the more common, alpha nuclide, Ca-40. Relevant examples are found in the hot, non-magnetic HgMn stars, and the field horizontal-branch star, Feige 86. The calcium anomaly is also present in cool, magnetic stars, including the notorious HD 101065, Przybylski's star.

  19. Neutron stars as laboratories for gravity physics

    SciTech Connect (OSTI)

    Deliduman, Cemsinan

    2014-01-01

    We study the structure of neutron stars in R+?R² gravity model with perturbative method. We obtain mass-radius relations for four representative equations of state (EoS). We find that, for |?|~10? cm², the results differ substantially from the results of general relativity. The effects of modified gravity are seen as mimicking a stiff or soft EoS for neutron stars depending upon whether ? is negative or positive, respectively. Some of the soft EoS that are excluded within the framework of general relativity can be reconciled for certain values of ? of this order with the 2 solar mass neutron star recently observed. Indeed, if the EoS is ever established to be soft, modified gravity of the sort studied here may be required to explain neutron star masses as large as 2 M{sub ?}. The associated length scale ?(?)~10? cm is of the order of the the typical radius of neutron stars implying that this is the smallest value we could find by using neutron stars as a probe. We thus conclude that the true value of ? is most likely much smaller than 10? cm².

  20. Massive Stars in the Arches Cluster

    E-Print Network [OSTI]

    Figer, D F; Gilmore, D; Morris, M; Kim, S S; Serabyn, E; McLean, I S; Gilbert, A M; Graham, J R; Larkin, J E; Levenson, N A; Teplitz, H I; Figer, Donald F.; Najarro, Francisco; Gilmore, Diane; Morris, Mark; Kim, Sungsoo S.; Serabyn, Eugene; Lean, Ian S. Mc; Gilbert, Andrea M.; Graham, James R.; Larkin, James E.; Teplitz, Harry I.

    2002-01-01

    We present and use new spectra and narrow-band images, along with previously published broad-band images, of stars in the Arches cluster to extract photometry, astrometry, equivalent width, and velocity information. The data are interpreted with a wind/atmosphere code to determine stellar temperatures, luminosities, mass-loss rates, and abundances. We have doubled the number of known emission-line stars, and we have also made the first spectroscopic identification of the main sequence for any population in the Galactic Center. We conclude that the most massive stars are bona-fide Wolf-Rayet (WR) stars and are some of the most massive stars known, having M_{initial} > 100 Msun, and prodigious winds, Mdot > 10^{-5} Msun yr^{-1}, that are enriched with helium and nitrogen; with these identifications, the Arches cluster contains about 5% of all known WR stars in the Galaxy. We find an upper limit to the velocity dispersion of 22 kms^{-1}, implying an upper limit to the cluster mass of 7(10^4) Msun within a radius...

  1. r-Process Enhanced Halo Stars

    E-Print Network [OSTI]

    J. J. Cowan; C. Sneden; J. E. Lawler; E. A. Den Hartog

    2006-10-13

    Abundance observations indicate the presence of rapid-neutron capture (i.e., r-process) elements in old Galactic halo and globular cluster stars. These observations provide insight into the nature of the earliest generations of stars in the Galaxy -- the progenitors of the halo stars -- responsible for neutron-capture synthesis of the heavy elements. The large star-to-star scatter observed in the abundances of neutron-capture element/iron ratios at low metallicities -- which diminishes with increasing metallicity or [Fe/H] -- suggests the formation of these heavy elements (presumably from certain types of supernovae) was rare in the early Galaxy. The stellar abundances also indicate a change from the r-process to the slow neutron capture (i.e., s-) process at higher metallicities in the Galaxy and provide insight into Galactic chemical evolution. Finally, the detection of thorium and uranium in halo and globular cluster stars offers an independent age-dating technique that can put lower limits on the age of the Galaxy, and hence the Universe.

  2. Storage and Assay of Tritium in STAR

    SciTech Connect (OSTI)

    Glen R. Longhurst; Robert A. Anderl; Robert J. Pawelko

    2004-09-01

    The Safety and Tritium Applied Research (STAR) facility has recently been commissioned to investigate tritium-related safety questions for fusion and other technologies. The authorized inventory of tritium is 1.6 grams, the threshold quantity for nuclear facility classification. A key capability in successful operation of the STAR facility is the ability to receive, inventory, and dispense tritium to the various experiments underway there. The system central to that function is the Tritium Storage and Assay System (SAS). The SAS has four major functions: (1) receiving and holding tritium from shipping containers brought into the STAR facility, (2) assaying the amount of tritium in the SAS, (3) dispensing tritium to secondary beds or containers used for transferring it to the experimental systems in the STAR facility, and (4) purifying hydrogen isotopes from non-hydrogen species. To that may be added a fifth, optional function, isotopic separation of hydrogen isotopes using bed-to-bed transfer techniques. This paper documents the design and operation of the STAR SAS and the procedures used for tritium accountancy in the STAR facility.

  3. Star formation relations in nearby molecular clouds

    SciTech Connect (OSTI)

    Evans, Neal J. II; Heiderman, Amanda; Vutisalchavakul, Nalin

    2014-02-20

    We test some ideas for star formation relations against data on local molecular clouds. On a cloud by cloud basis, the relation between the surface density of star formation rate and surface density of gas divided by a free-fall time, calculated from the mean cloud density, shows no significant correlation. If a crossing time is substituted for the free-fall time, there is even less correlation. Within a cloud, the star formation rate volume and surface densities increase rapidly with the corresponding gas densities, faster than predicted by models using the free-fall time defined from the local density. A model in which the star formation rate depends linearly on the mass of gas above a visual extinction of 8 mag describes the data on these clouds, with very low dispersion. The data on regions of very massive star formation, with improved star formation rates based on free-free emission from ionized gas, also agree with this linear relation.

  4. Massive stars on the verge of exploding: the properties of oxygen sequence Wolf-Rayet stars

    E-Print Network [OSTI]

    Tramper, F; Sanyal, D; Sana, H; de Koter, A; Gräfener, G; Langer, N; Vink, J S; de Mink, S E; Kaper, L

    2015-01-01

    Context. Oxygen sequence Wolf-Rayet (WO) stars represent a very rare stage in the evolution of massive stars. Their spectra show strong emission lines of helium-burning products, in particular highly ionized carbon and oxygen. The properties of WO stars can be used to provide unique constraints on the (post-)helium burning evolution of massive stars, as well as their remaining lifetime and the expected properties of their supernovae. Aims. We aim to homogeneously analyse the currently known presumed-single WO stars to obtain the key stellar and outflow properties and to constrain their evolutionary state. Methods. We use the line-blanketed non-local thermal equilibrium atmosphere code cmfgen to model the X-Shooter spectra of the WO stars and deduce the atmospheric parameters. We calculate dedicated evolutionary models to determine the evolutionary state of the stars. Results. The WO stars have extremely high temperatures that range from 150 kK to 210 kK, and very low surface helium mass fractions that range f...

  5. Preserving chemical signatures of primordial star formation in the first low-mass stars

    E-Print Network [OSTI]

    Ji, Alexander P; Bromm, Volker

    2015-01-01

    We model early star forming regions and their chemical enrichment by Population III (Pop III) supernovae with nucleosynthetic yields featuring high [C/Fe] ratios and pair-instability supernova (PISN) signatures. We aim to test how well these chemical abundance signatures are preserved in the gas prior to forming the first long-lived low-mass stars (or second-generation stars). Our results show that second-generation stars can retain the nucleosynthetic signature of their Pop III progenitors, even in the presence of nucleosynthetically normal Pop III core-collapse supernovae. We find that carbon-enhanced metal-poor stars are likely second-generation stars that form in minihaloes. Furthermore, it is likely that the majority of Pop III supernovae produce high [C/Fe] yields. In contrast, metals ejected by a PISN are not concentrated in the first star forming haloes, which may explain the absence of observed PISN signatures in metal-poor stars. We also find that unique Pop III abundance signatures in the gas are q...

  6. Wolf-Rayet stars in the Small Magellanic Cloud: I. Analysis of the single WN stars

    E-Print Network [OSTI]

    Hainich, R; Todt, H; Shenar, T; Sander, A; Hamann, W -R

    2015-01-01

    Wolf-Rayet (WR) stars have a severe impact on their environments owing to their strong ionizing radiation fields and powerful stellar winds. Since these winds are considered to be driven by radiation pressure, it is theoretically expected that the degree of the wind mass-loss depends on the initial metallicity of WR stars. Following our comprehensive studies of WR stars in the Milky Way, M31, and the LMC, we derive stellar parameters and mass-loss rates for all seven putatively single WN stars known in the SMC. Based on these data, we discuss the impact of a low-metallicity environment on the mass loss and evolution of WR stars. The quantitative analysis of the WN stars is performed with the Potsdam Wolf-Rayet (PoWR) model atmosphere code. The physical properties of our program stars are obtained from fitting synthetic spectra to multi-band observations. In all SMC WN stars, a considerable surface hydrogen abundance is detectable. The majority of these objects have stellar temperatures exceeding 75 kK, while ...

  7. EPA ENERGY STAR Webinar: How to Apply for the ENERGY STAR

    Broader source: Energy.gov [DOE]

    The U.S. Environmental Protection Agency (EPA) is hosting a webinar on how to apply for ENERGY STAR certification in Portfolio Manager. Understand the value of the ENERGY STAR certification, see the step-by-step process of applying, and gain tips to help your property get from application to award.

  8. Can star cluster environment affect dust input from massive AGB stars?

    E-Print Network [OSTI]

    Zhukovska, Svitlana; Henning, Thomas

    2015-01-01

    We examine the fraction of massive asymptotic giant branch (AGB) stars remaining bound in their parent star clusters and the effect of irradiation of these stars by intracluster ultraviolet (UV) field. We employ a set of N-body models of dynamical evolution of star clusters rotating in a galactic potential at the solar galactocentric radius. The cluster models are combined with stellar evolution formulae, a library of stellar spectra, and simple models for SiO photodissociation in circumstellar environment (CSE). The initial stellar masses of clusters are varied from $50\\rm M_\\odot$ to $10^{5}\\rm M_\\odot$. Results derived for individual clusters are combined using a mass distribution function for young star clusters. We find that about 30% of massive AGB stars initially born in clusters become members of the field population, while the rest evolves in star clusters. They are irradiated by strong intracluster UV radiation resulting in the decrease of the photodissociation radius of SiO molecules, in many stars...

  9. On the co-existence of chemically peculiar Bp stars, slowly pulsating B stars and constant B stars in the same part of the H-R diagram

    E-Print Network [OSTI]

    Briquet, M; De Cat, P; Aerts, C; North, P; Scholler, M; 10.1051/0004-6361:20066940

    2009-01-01

    Aims. In order to better model massive B-type stars, we need to understand the physical processes taking place in slowly pulsating B (SPB) stars, chemically peculiar Bp stars, and non-pulsating normal B stars co-existing in the same part of the H-R diagram. Methods. We carry out a comparative study between samples of confirmed and well-studied SPB stars and a sample of well-studied Bp stars with known periods and magnetic field strengths. We determine their evolutionary state using accurate HIPPARCOS parallaxes and Geneva photometry. We discuss the occurrence and strengths of magnetic fields as well as the occurrence of stellar pulsation among both groups. Further, we make a comparison of Geneva photometric variability for both kinds of stars. Results. The group of Bp stars is significantly younger than the group of SPB stars. Longitudinal magnetic fields in SPB stars are weaker than those of Bp stars, suggesting that the magnetic field strength is an important factor for B type stars to become chemically pec...

  10. Vacuum fluctuation inside a star and their consequences for neutron stars, a simple model

    E-Print Network [OSTI]

    Gunther Caspar; Isaac Rodriguez; Peter O. Hess; Walter Greiner

    2015-06-03

    Applying semi-classical Quantum Mechanics, the vacuum fluctuations within a star are determined, assuming a constant mass density and applying a monopole approximation. It is found that the density for the vacuum fluctuations does not only depend linearly on the mass density, as assumed in a former publication, where neutron stars up to 6 solar masses were obtained. This is used to propose a simple model on the dependence of the dark energy to the mass density, as a function of the radial distance r. It is shown that stars with up to 200 solar masses can, in principle, be obtained. Though, we use a simple model, it shows that in the presence of vacuum fluctuations stars with large masses can be stabilized and probably stars up to any mass can exist, which usually are identified as black holes.

  11. Progressive star formation in the young galactic super star cluster NGC 3603

    E-Print Network [OSTI]

    Beccari, Giacomo; De Marchi, Guido; Paresce, Francesco; Young, Erick; Andersen, Morten; Panagia, Nino; Balick, Bruce; Bond, Howard; Calzetti, Daniela; Carollo, C Marcella; Disney, Michael J; Dopita, Michael A; Frogel, Jay A; Hall, Donald N B; Holtzman, Jon A; Kimble, Randy A; McCarthy, Patrick J; O'Connell, Robert W; Saha, Abhijit; Silk, Joseph I; Trauger, John T; Walker, Alistair R; Whitmore, Bradley C; Windhorst, Rogier A

    2010-01-01

    Early release science observations of the cluster NGC3603 with the WFC3 on the refurbished HST allow us to study its recent star formation history. Our analysis focuses on stars with Halpha excess emission, a robust indicator of their pre-main sequence (PMS) accreting status. The comparison with theoretical PMS isochrones shows that 2/3 of the objects with Halpha excess emission have ages from 1 to 10 Myr, with a median value of 3 Myr, while a surprising 1/3 of them are older than 10 Myr. The study of the spatial distribution of these PMS stars allows us to confirm their cluster membership and to statistically separate them from field stars. This result establishes unambiguously for the first time that star formation in and around the cluster has been ongoing for at least 10-20 Myr, at an apparently increasing rate.

  12. Color superconducting quark matter in compact stars

    E-Print Network [OSTI]

    D. B. Blaschke; T. Klahn; F. Sandin

    2007-12-02

    Recent indications for high neutron star masses (M \\sim 2 M_sun) and large radii (R > 12 km) could rule out soft equations of state and have provoked a debate whether the occurence of quark matter in compact stars can be excluded as well. We show that modern quantum field theoretical approaches to quark matter including color superconductivity and a vector meanfield allow a microscopic description of hybrid stars which fulfill the new, strong constraints. For these objects color superconductivity turns out to be an essential ingredient for a successful description of the cooling phenomenology in accordance with recently developed tests. We discuss the energy release in the neutrino untrapping transition as a new aspect of the problem that hybrid stars masquerade themselves as neutron stars. Quark matter searches in future generations of low-temperature/high-density nucleus-nucleus collision experiments such as low-energy RHIC and CBM @ FAIR might face the same problem of an almost crossover behavior of the deconfinement transition. Therefore, diagnostic tools shall be derived from effects of color superconductivity.

  13. Stars and statistical physics: a teaching experience

    E-Print Network [OSTI]

    R. Balian; J. -P. Blaizot

    1999-09-20

    The physics of stars, their workings and their evolution, is a goldmine of problems in statistical mechanics and thermodynamics. We discuss many examples that illustrate the possibility of deepening student's knowledge of statistical mechanics by an introductory study of stars. The matter constituting the various stellar objects provides examples of equations of state for classical or quantal and relativistic or non-relativistic gases. Maximum entropy can be used to characterize thermodynamic and gravitational equilibrium which determines the structure of stars and predicts their instability above a certain mass. Contraction accompanying radiation induces either heating or cooling, which explains the formation of stars above a minimum mass. The characteristics of the emitted light are understood from black-body radiation and more precisely from the Boltzmann-Lorentz kinetic equation for photons. The luminosity is governed by the transport of heat by photons from the center to the surface. Heat production by thermonuclear fusion is determined by microscopic balance equations. The stability of the steady state of stars is controlled by the interplay of thermodynamics and gravitation.

  14. STARS MDT-II targets mission

    SciTech Connect (OSTI)

    Sims, B.A.; White, J.E.

    1997-08-01

    The Strategic Target System (STARS) was launched successfully on August 31, 1996 from the Kauai Test Facility (KTF) at the Pacific Missile Range Facility (PMRF). The STARS II booster delivered a payload complement of 26 vehicles atop a post boost vehicle. These targets were designed and the mission planning was achieved to provide for a dedicated mission for view by the Midcourse Space Experiment (MSX) Satellite Sensor Suite. Along with the MSX Satellite, other corollary sensors were involved. Included in these were the Airborne Surveillance Test Bed (AST) aircraft, the Cobra Judy sea based radar platform, Kwajalein Missile Range (KMR), and the Kiernan Reentry Measurements Site (KREMS). The launch was a huge success from all aspects. The STARS Booster flew a perfect mission from hardware, software and mission planning respects. The payload complement achieved its desired goals. All sensors (space, air, ship, and ground) attained excellent coverage and data recording.

  15. SED modeling of Young Massive Stars

    E-Print Network [OSTI]

    Thomas P. Robitaille

    2007-11-27

    In this contribution, I review the applications and potential limitations of the spectral energy distribution fitting tool that I have developed, with a strong emphasis on the limits to which this tool can be used to improve our understanding of massive star formation. I discuss why our current grid of models cannot be used to distinguish between the several competing theories of massive star formation. I also discuss stellar mass determinations, artificial correlations between parameters in the grid of models, multiplicity, confusion, dust assumptions, and unique fits. I briefly review the improvements we intend to carry out for our next grid of models, which will eliminate many of these limitations. Finally, I show examples of applications of this tool to massive young stars.

  16. Magnetized Atmospheres around Accreting Neutron Stars

    E-Print Network [OSTI]

    S. Zane; R. Turolla; A. Treves

    2000-02-01

    We present a detailed investigation of atmospheres around accreting neutron stars with high magnetic field ($B\\gtrsim 10^{12}$ G) and low luminosity ($L\\lesssim 10^{33}$ erg/s). We compute the atmospheric structure, intensity and emergent spectrum for a plane-parallel, pure hydrogen medium by solving the transfer equations for the normal modes coupled to the hydrostatic and energy balance equations. The hard tail found in previous investigations for accreting, non-magnetic neutron stars with comparable luminosity is suppressed and the X-ray spectrum, although still harder than a blackbody at the star effective temperature, is nearly planckian in shape. Spectra from accreting atmospheres, both with high and low fields, are found to exhibit a significant excess at optical wavelengths above the Rayleigh-Jeans tail of the X-ray continuum.

  17. General relativistic neutron stars with twisted magnetosphere

    E-Print Network [OSTI]

    A. G. Pili; N. Bucciantini; L. Del Zanna

    2014-12-12

    Soft Gamma-Ray Repeaters and Anomalous X-Ray Pulsars are extreme manifestations of the most magnetized neutron stars: magnetars. The phenomenology of their emission and spectral properties strongly support the idea that the magnetospheres of these astrophysical objects are tightly twisted in the vicinity of the star. Previous studies on equilibrium configurations have so far focused on either the internal or the external magnetic field configuration, without considering a real coupling between the two fields. Here we investigate numerical equilibrium models of magnetized neutron stars endowed with a confined twisted magnetosphere, solving the general relativistic Grad-Shafranov equation both in the interior and in the exterior of the compact object. A comprehensive study of the parameters space is provided to investigate the effects of different current distributions on the overall magnetic field structure.

  18. Texas LoanSTAR Monitoring and Analysis Program: Report to the Monitoring and Analysis Review Committee 

    E-Print Network [OSTI]

    Turner, W. D.; O'Neal, D. L.; Claridge, D. E.; Heffington, W.; Haberl, J. S.; Reddy, T. A.; Saman, N.

    1993-01-01

    .75, 1.0, 1.25, 1.5, 1.75 and 2.0 for each turbine speed. To provide a complete picture of hub cooling under rotating conditions, experiments with simultaneous injection of coolant gas through upstream and downstream injection are conducted for an of MFR...

  19. Precision age indicators that exploit chemically peculiar stars

    E-Print Network [OSTI]

    Worthey, Guy

    2015-01-01

    We would like to find a way to improve the determination of galaxy star formation history from integrated light spectroscopy. To this end, several classes of chemically peculiar (CP) stars arise during the course of normal evolution in single stars and noninteracting binary stars. An aging stellar population has periods of time in which CP stars contribute to the integrated light, and others in which the contributions fade. The HgMn stars, for example, occupy a narrow temperature range of 10500 to 16000 K, which maps to a narrow range of ages. Wolf-Rayet stars, He-poor stars, Bp-Ap stars, Am-Fm stars, and C stars all become very common in a normal stellar population at various ages between zero and several Gyr, fading in and out in a way that is analogous to features used in stellar spectral classification. We examine population fractions and light fractions in order to assess the feasibility of using CP stars as age tracers. We find that, even though CP stars do not usually dominate in number, there are enou...

  20. A new method to derive star formation histories of galaxies from their star cluster distributions

    E-Print Network [OSTI]

    Thomas Maschberger; Pavel Kroupa

    2007-05-07

    Star formation happens in a clustered way which is why the star cluster population of a particular galaxy is closely related to the star formation history of this galaxy. From the probabilistic nature of a mass function follows that the mass of the most-massive cluster of a complete population, M_max, has a distribution with the total mass of the population as a parameter. The total mass of the population is connected to the star formation rate (SFR) by the length of a formation epoch. Since due to evolutionary effects only massive star clusters are observable up to high ages it is convenient to use this M_max(SFR) relation for the reconstruction of a star formation history. The age-distribution of the most-massive clusters can therefore be used to constrain the star formation history of a galaxy. The method, including an assessment of the inherent uncertainties, is introduced with this contribution, while following papers will apply this method to a number of galaxies.

  1. Carbon Enhanced Metal-Poor Stars. I. Chemical Compositions of 26 Stars

    E-Print Network [OSTI]

    Wako Aoki; Timothy C. Beers; Norbert Christlieb; John E. Norris; Sean G. Ryan; Stelios Tsangarides

    2006-09-26

    The chemical compositions of 26 metal-poor stars that exhibit strong CH and/or C2 molecular bands are determined based on high-resolution spectroscopy. We define carbon-enhanced stars taking account of the carbon abundance ratio ([C/Fe]) and the evolutionary status. Twenty two stars in our sample satisfy our modified definition for Carbon-Enhanced Metal-Poor (CEMP) stars. In addition, we measure Na abundances for nine other carbon-enhanced stars for which abundances of other elements have been previously reported. Combining our new sample with the results of previous work, we investigate the abundance and evolutionary status of a total of 64 CEMP stars. In this paper, we separate the carbon-enhanced objects into Ba-rich and Ba-normal objects, and discuss on (1) the metallicity distributions, (2) the correlation between Ba and C (and C+N) abundances, (3) C abundance distributions, (3) the distributions of evolutionary status, and (5) Na abundances. The implications of these results on the origins of carbon in CEMP stars are discussed.

  2. LANL/Green Star spectrometer tests

    SciTech Connect (OSTI)

    Sampson, T.E.; Cremers, T.L.; Vo, D.T. [Los Alamos National Lab., NM (United States); Seldiakov, Y.P.; Dorin, A.B.; Kondrashov, M.V. [Green Star, Moscow (Russian Federation); Timoshin, V.I. [VNIINM, Moscow (Russian Federation)

    1997-12-01

    The US and Russia have agreed to the joint development of a nondestructive assay system for use to support the dismantlement of nuclear weapons in Russia. This nondestructive assay system will be used to measure plutonium produced by the conversion of Russian nuclear weapons. The NDA system for Russia will be patterned after the ARIES NDA system being constructed at Los Alamos. One goal of the program is to produce an NDA system for use in Russia that maximizes the use of Russian resources to facilitate maintenance and future upgrades. The Green Star SBS50 Single Board Spectrometer system (Green Star Ltd., Moscow, Russia) has been suggested for use as the data acquisition component for gamma ray instruments in the system. Possible uses are for plutonium isotopic analysis and also segmented gamma scanning. Green Star has also developed analysis software for the SBS50. This software, both plutonium isotopic analysis and uranium enrichment analysis, was developed specifically for customs/border inspection applications (low counting rate applications and identification as opposed to quantification) and was not intended for MC and A applications. Because of the relative immaturity of the Green Star plutonium isotopic analysis software (it has been under development for only one year and is patterned after US development circa 1980), it was tentatively agreed, before the tests, that the Russian NDA system would use the Los Alamos PC/FRAM software for plutonium isotopic analysis. However, it was also decided to include the Green Star plutonium isotopic software in the testing, both to quantify its performance for MC and A applications and also to provide additional data to Green Star for further development of their software. The main purpose of the testing was to evaluate the SBS-50 spectrometer as a data acquisition device for use with LANL software.

  3. Effective No-Hair Relations for Neutron Stars and Quark Stars: Relativistic Results

    E-Print Network [OSTI]

    Kent Yagi; Koutarou Kyutoku; George Pappas; Nicolas Yunes; Theocharis A. Apostolatos

    2014-09-08

    Astrophysical charge-free black holes are known to satisfy no-hair relations through which all multipole moments can be specified in terms of just their mass and spin angular momentum. We here investigate the possible existence of no-hair-like relations among multipole moments for neutron stars and quark stars that are independent of their equation of state. We calculate the multipole moments of these stars up to hexadecapole order by constructing uniformly-rotating and unmagnetized stellar solutions to the Einstein equations. For slowly-rotating stars, we construct stellar solutions to quartic order in spin in a slow-rotation expansion, while for rapidly-rotating stars, we solve the Einstein equations numerically with the LORENE and RNS codes. We find that the multipole moments extracted from these numerical solutions are consistent with each other. We confirm that the current-dipole is related to the mass-quadrupole in an approximately equation of state independent fashion, which does not break for rapidly rotating neutron stars or quark stars. We further find that the current-octupole and the mass-hexadecapole moments are related to the mass-quadrupole in an approximately equation of state independent way to $\\sim 10%$, worsening in the hexadecapole case. All of our findings are in good agreement with previous work that considered stellar solutions to leading-order in a weak-field expansion. The quartic in spin, slowly-rotating solutions found here allow us to estimate the systematic errors in the measurement of the neutron star's mass and radius with future X-ray observations, such as NICER and LOFT. We find that the effect of these quartic-in-spin terms on the quadrupole and hexadecapole moments and stellar eccentricity may dominate the error budget for very rapidly-rotating neutron stars. The new universal relations found here should help to reduce such systematic errors.

  4. Beryllium in Disk and Halo Stars -- Evidence for a Beryllium Dispersion in Old Stars

    E-Print Network [OSTI]

    Ann Merchant Boesgaard; Megan C. Novicki

    2005-12-13

    The study of Be in stars of differing metal content can elucidate the formation mechanisms and the Galactic chemical evolution of Be. We have obtained high-resolution, high signal-to-noise spectra of the resonance lines of Be II in eight stars with the high-dispersion spectrograph (HDS) on the Subaru 8.2 m telescope on Mauna Kea. Abundances of Be have been determined through spectrum synthesis. The stars with [Fe/H] values > -1.1 conform to the published general trend of Be vs Fe. We have confirmed the high Be abundance in HD 94028 and have found a similarly high Be abundance in another star, HD 132475, at the same metallicity: [Fe/H] = -1.5. These two stars are 0.5 - 0.6 dex higher in Be than the Be-Fe trend. While that general trend contains the evidence for a Galaxy-wide enrichment in Be and Fe, the higher Be abundances in those two stars indicates local Be enrichments. Possible enrichment mechanisms include hypernovae and multiple supernova explosions contained in a superbubble. The star G 64-37 has [Fe/] = -3.2; we have determined its Be abundance to look for evidence of a Be plateau. It's Be abundance appears to extend the Be-Fe trend to lower Fe abundances without any evidence for a plateau as had been indicated by a high Be abundance in another very metal-poor star, G 64-12. Although these two stars have similar Be abundances within the errors, it could be that their different Be values may be indicating that a Be dispersion exists even at the lowest metallicities.

  5. A planet orbiting the star Gliese 86

    E-Print Network [OSTI]

    D. Queloz; M. Mayor; L. Weber; A. Blecha; M. Burnet; B. Confino; D. Naef; F. Pepe; N. Santos; S. Udry

    1999-10-12

    A 4MJ planet with a 15.8day orbital period has been detected from very precise radial velocity measurements with the CORALIE echelle spectrograph. A second remote and more massive companion has also been detected. All the planetary companions so far detected in orbit closer than 0.08 AU have a parent star with a statistically higher metal content compared to the metallicity distribution of other stars with planets. Different processes occuring during their formation may provide a possible explanation for this observation.

  6. Integration and conventional systems at STAR

    SciTech Connect (OSTI)

    Matis, Howard S.; Brown, Ralph L.; Christie, William; Edwards, W.R.; Jared, Richard; Minor, Bob; Salz, Paul

    2002-02-20

    At the beginning of the design and construction of the STAR Detector, the collaboration assigned a team of physicists and engineers the responsibility of coordinating the construction of the detector. This group managed the general space assignments for each sub-system and coordinated the assembly and planning for the detector. Furthermore, as this group was the only STAR group with the responsibility of looking at the system as a whole, the collaboration assigned it several tasks that spanned the different sub-detectors. These items included grounding, rack layout, cable distribution, electrical, power and water, and safety systems. This paper describes these systems and their performance.

  7. UBV stellar photometry of bright stars in GC M5. II. Physical parameters of HB stars

    E-Print Network [OSTI]

    P. V. Baev; H. Markov; N. Spassova

    2001-08-09

    The physical parameters of the stars in the central region of the globular cluster M5 (NGC 5904) were determined from UBV photometry using Kurucz (1992) synthetic flux distributions and some empirical relations. It is found that the bluest horizontal branch stars have higher luminosities than predicted by canonical zero-age horizontal branch models. Parameters of the mass distribution on the HB stars are determined. It is shown that the gap in the blue HB previously reported (Markov et al. 1999) is probably a statistical fluctuation.

  8. Gamma-Ray Bursts and Afterglows from Rotating Strange Stars and Neutron Stars

    E-Print Network [OSTI]

    Z. G. Dai; T. Lu

    1998-10-21

    We here discuss a new model of $\\gamma$-ray bursts (GRBs) based on differentially rotating strange stars. Strange stars in this model and differentially rotating neutron stars in the Klu\\'zniak-Ruderman model can produce extremely relativistic, variable fireballs required by GRBs and then become millisecond pulsars. The effect of such pulsars on expansion of the postburst fireballs through magnetic dipole radiation is studied. We show that these two models can explain naturally not only various features of GRBs but also light curves of afterglows.

  9. Conversion of neutron stars to strange stars as the central engine of gamma-ray bursts

    E-Print Network [OSTI]

    Ignazio Bombaci; Bhaskar Datta

    2000-01-27

    We study the conversion of a neutron star to a strange star as a possible energy source for gamma-ray bursts. We use different recent models for the equation of state of neutron star matter and strange quark matter. We show that the total amount of energy liberated in the conversion is in the range of (1-4) 10^{53} ergs (one order of magnitude larger than previous estimates) and is in agreement with the energy required to power gamma-ray burst sources at cosmological distances.

  10. EPA ENERGY STAR: Tackling Growth in Home Electronics and Small Appliances

    E-Print Network [OSTI]

    Sanchez, Marla Christine

    2008-01-01

    ENERGY STAR as a national program platform ENERGY STAR is atreats ENERGY STAR as a leveraged national program strategyNational Laboratory best estimates. This methodology represents ENERGY STAR program

  11. Streamlining ENERGY STAR Appliance Testing | Department of Energy

    Energy Savers [EERE]

    purchase more than 300 million ENERGY STAR-qualified products -- making the ENERGY STAR blue label the gold standard for energy-efficient products. Since the joint program was...

  12. Columbia Water & Light- New Home ENERGY STAR Rebate

    Broader source: Energy.gov [DOE]

    Columbia Water and Light offers a $1,000 rebate to customers for the construction of new homes that achieve certification as Energy Star homes. The Energy Star designation is given to homes that...

  13. ENERGY STAR Residential Water Heaters to Save Americans Up to...

    Energy Savers [EERE]

    ENERGY STAR Residential Water Heaters to Save Americans Up to 823 Million in the Next Five Years ENERGY STAR Residential Water Heaters to Save Americans Up to 823 Million in the...

  14. Duke Energy (Electric)- Energy Star Homes Rate Discount Program

    Broader source: Energy.gov [DOE]

    Duke Energy encourages residential customers to buy energy-efficient homes through the utility's Energy Star Homes Program, which awards a rate discount to customers living in Energy Star homes. To...

  15. Duke Energy (Electric)- Energy Star Homes Rate Discount Program

    Broader source: Energy.gov [DOE]

    Duke Energy encourages residential customers to buy energy-efficient homes through the utility's Energy Star Homes Program, which awards a rate discount to customers living in Energy Star homes....

  16. Creating a Star on Earth | Department of Energy

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Creating a Star on Earth Creating a Star on Earth March 5, 2014 - 11:45am Addthis An error occurred. Try watching this video on www.youtube.com, or enable JavaScript if it is...

  17. ENERGY STAR Certified Homes, Version 3 (Rev. 07) National Program...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    with electric backup or ENERGY STAR certified dual-fuel backup heating, OR; Ground-source heat pump, any product type, ENERGY STAR certified 18 90 AFUE gas furnace,...

  18. Home Performance with ENERGY STAR -- 10 Years of Continued Growth...

    Energy Savers [EERE]

    ENERGY STAR -- 10 Years of Continued Growth Home Performance with ENERGY STAR -- 10 Years of Continued Growth Provides an overview of the HPwES program, HPwES successes, and...

  19. Energy Star for Hospitals 2011 Update: Progression or Regression? 

    E-Print Network [OSTI]

    Travis, B.

    2012-01-01

    The Energy Star performance rating system for buildings has achieved widespread adoption in the building sector as a standard benchmark for energy performance. In 2011, the U.S. EPA released an updated technical methodology for its Energy Star...

  20. Probing young massive clusters with laser guide star adaptive optics

    E-Print Network [OSTI]

    McCrady, Nate

    2009-01-01

    laser guide star adaptive optics Nate McCrady Received: 10laser guide star adaptive optics (LGS/AO) on the 10 m Keckof 4 Mpc. Our adaptive optics work is motivated by three

  1. Evaluation Prompts ENERGY STAR Program to Replace Web Tool, Saving...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Prompts ENERGY STAR Program to Replace Web Tool, Saving 90 Percent of Annual Costs Evaluation Prompts ENERGY STAR Program to Replace Web Tool, Saving 90 Percent of Annual Costs...

  2. Advanced Combustion Modeling with STAR-CD using Transient Flemelet...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Modeling with STAR-CD using Transient Flemelet Models: TIF and TPV Advanced Combustion Modeling with STAR-CD using Transient Flemelet Models: TIF and TPV Presentation given at the...

  3. 3D Simulations of Thermonuclear Supernovae From Very Massive Stars

    E-Print Network [OSTI]

    Crowther, Paul

    3D Simulations of Thermonuclear Supernovae From Very Massive Stars Ke-Jung (Ken) Chen Johnston #12;3D Simulations of Thermonuclear Supernovae From Very Massive Stars Ke-Jung (Ken) Chen Johnston

  4. Hitting the Target: ENERGY STAR® SSL Outdoor Area Lighting Webcast

    Broader source: Energy.gov [DOE]

    In this October 8, 2009 webcast, ENERGY STAR Program Manager Richard Karney gave an overview of ENERGY STAR criteria covering SSL-based outdoor area and roadway lighting, outdoor wall packs,...

  5. Calendar Year 2008 Program Benefits for ENERGY STAR Labeled Products

    E-Print Network [OSTI]

    Homan, GregoryK

    2010-01-01

    market shares are an industry estimate provided by Honeywell 3) ENERGY STAR exit signs, traffic signals, and transformers

  6. Calendar Year 2007 Program Benefits for ENERGY STAR Labeled Products

    E-Print Network [OSTI]

    Sanchez, Marla Christine

    2008-01-01

    market shares are an industry estimate provided by Honeywell 3) ENERGY STAR exit signs, traffic signals, and transformers

  7. Neutron star cooling: theoretical aspects and observational constraints

    E-Print Network [OSTI]

    Neutron star cooling: theoretical aspects and observational constraints D.G. Yakovlev a,*, O 2003 Abstract The cooling theory of isolated neutron stars is reviewed. The main cooling regulators of supranuclear matter in neutron star interiors by confronting cooling theory with observations of isolated

  8. ENERGY STAR Back-To-School Shopping Checklist

    E-Print Network [OSTI]

    ENERGY STAR® Back-To-School Shopping Checklist Students can make a difference by shopping "smart" with ENERGY STAR® . Computing the Savings ENERGY STAR Qualified Computer Equipment Computer Monitor ENERGY up to 90 percent more energy than standard monitors. Printer If every home office were powered

  9. X-rays from magnetically channeled winds of OB stars

    E-Print Network [OSTI]

    David H. Cohen

    2008-01-30

    OB stars with strong radiation-driven stellar winds and large-scale magnetic fields generate strong and hard X-ray emission via the Magnetically Channeled Wind Shock (MCWS) mechanism. In this brief paper, I describe four separate X-ray diagnostics of the MCWS mechanism in OB stars, with applications to the prototype young O star, theta-1 Ori C.

  10. Creating an intelligent agent for StarCraft: Brood War

    E-Print Network [OSTI]

    Ernst, Damien

    Creating an intelligent agent for StarCraft: Brood War University of Liège Faculty of Applied artificialintelligence (AI)? Video games Why real-time strategy (RTS) games? Introduction #12;StarCraft: Brood War a patrol unit #12;Implementation Chapter III #12;StarCraft is not open source! The Brood War Application

  11. Herbig Ae/Be Stars in the Magellanic Bridge

    E-Print Network [OSTI]

    Shogo Nishiyama; Yasuaki Haba; Daisuke Kato; Daisuke Baba; Hirofumi Hatano; Motohide Tamura; Yasushi Nakajima; Akika Ishihara; Tetsuya Nagata; Koji Sugitani; Noriyuki Matsunaga; Hinako Fukushi; Nobuhiko Kusakabe; Shuji Sato

    2007-02-20

    We have found Herbig Ae/Be star candidates in the western region of the Magellanic Bridge. Using the near infrared camera SIRIUS and the 1.4 m telescope IRSF, we surveyed about 3.0 deg x 1.3 deg (24 deg Bridge, we estimate that about 80 (about 40%) of the candidates are likely to be Herbig Ae/Be stars. We also found one concentration of the candidates at the young star cluster NGC 796, strongly suggesting the existence of pre-main-sequence (PMS) stars in the Magellanic Bridge. This is the first detection of PMS star candidates in the Magellanic Bridge, and if they are genuine PMS stars, this could be direct evidence of recent star formation. However, the estimate of the number of Herbig Ae/Be stars depends on the fraction of classical Be stars, and thus a more precise determination of the Be star fraction or observations to differentiate between the Herbig Ae/Be stars and classical Be stars are required.

  12. The angular velocity of the apsidal rotation in binary stars

    E-Print Network [OSTI]

    B. V. Vasiliev

    2004-05-19

    The shape of a rotating star consisting of equilibrium plasma is considered. The velocity of apsidal rotation of close binary stars (periastron rotation) which depends on the star shapes is calculated. The obtained estimations are in a good agreement with the observation data of the apsidal motion in binary systems.

  13. The compact star in the SU(3) sigma model

    E-Print Network [OSTI]

    Ryszard Manka; Ilona Bednarek

    2004-11-04

    The linear chiral SU(3)*SU(3) model is applied to describe properties of the compact star matter inside the quark, protoneutron and neutron star.The leads to the neutron star with the value of maximum mass close to 1.5 solar mass and radius 11 km and with the reduced value of proton fraction and very compact hyperon core.

  14. Modeling anisotropic charged neutron star in isotropic coordinates

    E-Print Network [OSTI]

    Ksh. Newton Singh; Narendra Pradhan; Manuel Malaver

    2015-02-03

    We present a spherically symmetric solution of the general relativistic field equations in isotropic coordinates for charged fluid with pressure anisotropy, compatible with a super dense star modeling. Further, we have constructed an anisotropic model of super dense star with all degree of suitability. We also observed that by increasing anisotropy, the maximum mass of super dense stars also decreases.

  15. Hot neutron star in generalized thermo-statistics

    E-Print Network [OSTI]

    Hot neutron star in generalized thermo-statistics K. Miyazaki E-mail: miyazakiro@rio.odn.ne.jp Abstract The hot neutron star (NS) is investigated for the ...rst time in the generalized thermo-statistics. The study of neutron star (NS) is an important subject in nuclear physics and astro- physics. The equation

  16. Islamic Star Patterns from Polygons in Contact Craig S. Kaplan

    E-Print Network [OSTI]

    Waterloo, University of

    ]. Star patterns are a harmonious fusion of mathematics, art, and spirituality, and expressionsIslamic Star Patterns from Polygons in Contact Craig S. Kaplan School of Computer Science University of Waterloo Abstract We present a simple method for rendering Islamic star patterns based

  17. Star cell type core configuration for structural sandwich materials

    DOE Patents [OSTI]

    Christensen, Richard M. (Danville, CA)

    1995-01-01

    A new pattern for cellular core material used in sandwich type structural materials. The new pattern involves star shaped cells intermixed with hexagonal shaped cells. The new patterned cellular core material includes star shaped cells interconnected at points thereof and having hexagonal shape cells positioned adjacent the star points. The new pattern allows more flexibility and can conform more easily to curved shapes.

  18. $?$-Minkowski star product in any dimension from symplectic realization

    E-Print Network [OSTI]

    Anna Pachol; Patrizia Vitale

    2015-10-25

    We derive an explicit expression for the star product reproducing the $\\kappa$-Minkowski Lie algebra in any dimension $n$. The result is obtained by suitably reducing the Wick-Voros star product defined on $\\mathbb{C}^{d}_\\theta$ with $n=d+1$. It is thus shown that the new star product can be obtained from a Jordanian twist.

  19. Energy star compliant voice over internet protocol (VoIP) telecommunications network including energy star compliant VoIP devices

    DOE Patents [OSTI]

    Kouchri, Farrokh Mohammadzadeh

    2012-11-06

    A Voice over Internet Protocol (VoIP) communications system, a method of managing a communications network in such a system and a program product therefore. The system/network includes an ENERGY STAR (E-star) aware softswitch and E-star compliant communications devices at system endpoints. The E-star aware softswitch allows E-star compliant communications devices to enter and remain in power saving mode. The E-star aware softswitch spools messages and forwards only selected messages (e.g., calls) to the devices in power saving mode. When the E-star compliant communications devices exit power saving mode, the E-star aware softswitch forwards spooled messages.

  20. BINARY CENTRAL STARS OF PLANETARY NEBULAE DISCOVERED THROUGH PHOTOMETRIC VARIABILITY. III. THE CENTRAL STAR OF ABELL 65

    E-Print Network [OSTI]

    Hillwig, Todd C.

    A growing number of close binary stars are being discovered among central stars of planetary nebulae. Recent and ongoing surveys are finding new systems and contributing to our knowledge of the evolution of close binary ...

  1. Post-AGB stars as testbeds of nucleosynthesis in AGB stars

    E-Print Network [OSTI]

    G. Stasinska; R. Szczerba; M. Schmidt; N. Siodmiak

    2006-01-23

    We construct a data base of 125 post-AGB objects (including R CrB and extreme helium stars) with published photospheric parameters (effective temperature and gravity) and chemical composition. We estimate the masses of the post-AGB stars by comparing their position in the (log Teff, log g) plane with theoretical evolutionary tracks of different masses. We construct various diagrams, with the aim of finding clues to AGB nucleosynthesis. This is the first time that a large sample of post-AGB stars has been used in a systematic way for such a purpose and we argue that, in several respects, post-AGB stars should be more powerful than planetary nebulae to test AGB nucleosynthesis. Our main findings are that: the vast majority of objects which do not show evidence of N production from primary C have a low stellar mass (M* nucleosynthesis.

  2. Thermal evolution of rotating hybrid stars

    E-Print Network [OSTI]

    kang Miao; Zheng Xiaoping

    2007-02-28

    As a neutron star spins down, the nuclear matter continuously is converted into quark matter due to the core density increase and then latent heat is released. We have investigated the thermal evolution of neutron stars undergoing such deconfinement phase transition. We have taken into account the conversion in the frame of the general theory of relativity. The released energy has been estimated as a function of change rate of deconfinement baryon number. Numerical solutions to cooling equation are obtained to be very different from the without heating effect. The results show that neutron stars may be heated to higher temperature which is well-matched with pulsar's data despite onset of fast cooling in neutron stars with quark matter core. It is also found that heating effect has magnetic field strength dependence. This feature could be particularly interesting for high temperature of low-field millisecond pulsar at late stage. The high temperature could fit the observed temperature for PSR J0437-4715.

  3. Constraints in the coupling Star-Life

    E-Print Network [OSTI]

    L. Sertorio; G. Tinetti

    2001-10-01

    If life is sustained by a process of photosynthesis, not necessarily the same existing on Earth, the surface temperature of the star and the orbit of the host planet cannot be whatsoever. In fact the global life cycle, no matter how complicated, must contain in general an upper photochemical branch and a lower dark branch, characterized by a higher and a lower temperature. These two temperatures are star-orbit related. The velocity along the cycle or, in other words, the power of the life machine, depends in general on several other parameters. First of all the Gibbs photon availability, which is a star-orbit parameter and is the input for the upper branch. Then follows the energy cascade that develops along the organic web with a large number of interactions and typical times that must match the typical times generated by the combination of spin value and orientation, eccentricity and precession. Finally, the capacity of the web to keep the global life cycle running along the life span of the star, comes from some inner form of self-endurance and self-balance. The property of not being transient could be the right way of introducing the concept of intelligent life.

  4. Singularity-free dark energy star

    E-Print Network [OSTI]

    Farook Rahaman; Anil Kumar Yadav; Saibal Ray; Raju Maulick; Ranjan Sharma

    2011-08-25

    We propose a model for an anisotropic dark energy star where we assume that the radial pressure exerted on the system due to the presence of dark energy is proportional to the isotropic perfect fluid matter density. We discuss various physical features of our model and show that the model satisfies all the regularity conditions and stable as well as singularity-free.

  5. Attenuation of Beaming Oscillations Near Neutron Stars

    E-Print Network [OSTI]

    M. Coleman Miller

    2000-07-17

    Observations with RXTE have revealed kilohertz quasi-periodic brightness oscillations (QPOs) from nearly twenty different neutron-star low-mass X-ray binaries (LMXBs). These frequencies often appear as a pair of kilohertz QPOs in a given power density spectrum. In many models the higher-frequency of these QPOs is a beaming oscillation at the frequency of a nearly circular orbit at some radius near the neutron star. In such models it is expected that there will also be beaming oscillations at the stellar spin frequency and at overtones of the orbital frequency, but no strong QPOs have been detected at these frequencies. We therefore examine the processes that can attenuate beaming oscillations near neutron stars, and in doing so extend the work on this subject that was initiated by the discovery of lower-frequency QPOs from LMXBs. Among our main results are (1)in a spherical scattering cloud, all overtones of rotationally modulated beaming oscillations are attenuated strongly, not just the even harmonics, and (2)it is possible to have a relatively high-amplitude modulation near the star at, e.g., the stellar spin frequency, even if no peak at that frequency is detectable in a power density spectrum taken at infinity. We discuss the application of these results to modeling of kilohertz QPOs.

  6. Boson stars from a gauge condensate

    E-Print Network [OSTI]

    V. Dzhunushaliev; K. Myrzakulov; R. Myrzakulov

    2006-12-28

    The boson star filled with two interacting scalar fields is investigated. The scalar fields can be considered as a gauge condensate formed by SU(3) gauge field quantized in a non-perturbative manner. The corresponding solution is regular everywhere, has a finite energy and can be considered as a quantum SU(3) version of the Bartnik - McKinnon particle-like solution.

  7. Disks around Brown Dwarfs and Cool Stars

    E-Print Network [OSTI]

    Daniel Apai; Kevin Luhman; Michael Liu

    2007-02-10

    We review the current picture of disks around cool stars and brown dwarfs, including disk fractions, mass estimates, disk structure and dispersal, accretion, dust composition, and the debris disk phase. We discuss these in the framework of recent planet formation models.

  8. Neutron star interiors and topology change

    E-Print Network [OSTI]

    Peter K. F. Kuhfittig

    2013-09-05

    Quark matter is believed to exist in the center of neutron stars. A combined model consisting of quark matter and ordinary matter is used to show that the extreme conditions existing in the center could result in a topology change, that is, in the formation of wormholes.

  9. Neutron stars: compact objects with relativistic gravity

    E-Print Network [OSTI]

    Ek?i, K Yavuz

    2015-01-01

    General properties of neutron stars are briefly reviewed with an emphasis on the indispensability of general relativity in our understanding of these fascinating objects. In Newtonian gravity the pressure within a star merely plays the role of opposing self-gravity. In general relativity all sources of energy and momentum contribute to the gravity. As a result the pressure not only opposes gravity but also enhances it. The later role of pressure becomes more pronounced with increasing compactness, $M/R$ where $M$ and $R$ are the mass and radius of the star, and sets a critical mass beyond which collapse is inevitable. This critical mass has no Newtonian analogue; it is conceptually different than the Stoner-Landau-Chandrasekhar limit in Newtonian gravity which is attained asymptotically for ultra-relativistic fermions. For white dwarfs the general relativistic critical mass is very close to the Stoner-Landau-Chandrasekhar limit. For neutron stars the maximum mass---so called Oppenheimer-Volkoff limit---is sig...

  10. Light curves from rapidly rotating neutron stars

    E-Print Network [OSTI]

    Numata, Kazutoshi

    2010-01-01

    We calculate light curves produced by a hot spot of a rapidly rotating neutron star, assuming that the spot is perturbed by a core $r$-mode, which is destabilized by emitting gravitational waves. To calculate light curves, we take account of relativistic effects such as the Doppler boost due to the rapid rotation and light bending assuming the Schwarzschild metric around the neutron star. We assume that the core $r$-modes penetrate to the surface fluid ocean to have sufficiently large amplitudes to disturb the spot. For a $l'=m$ core $r$-mode, the oscillation frequency $\\omega\\approx2m\\Omega/[l'(l'+1)]$ defined in the co-rotating frame of the star will be detected by a distant observer, where $l'$ and $m$ are respectively the spherical harmonic degree and the azimuthal wave number of the mode, and $\\Omega$ is the spin frequency of the star. In a linear theory of oscillation, using a parameter $A$ we parametrize the mode amplitudes such that ${\\rm max}\\left(|\\xi_\\theta|,|\\xi_\\phi|\\right)/R=A$ at the surface, w...

  11. Nucleosynthesis in AGB Stars Maria Lugaro

    E-Print Network [OSTI]

    Nucleosynthesis in AGB Stars Maria Lugaro A thesis submitted for the degree of Doctor of Philosophy.1 Evolution prior and through the AGB phase . . . . . . . . . . . . . . . 1 1.2 Nucleosynthesis and mixing and models 15 2.1 The Monash Stellar Nucleosynthesis code . . . . . . . . . . . . . . . . . 15 2.1.1 Nuclear

  12. SUPPRESSION OF STAR FORMATION IN NGC 1266

    SciTech Connect (OSTI)

    Alatalo, Katherine; Lanz, Lauranne; Bitsakis, Theodoros; Appleton, Philip N.; Ogle, Patrick M.; Lacy, Mark; Lonsdale, Carol J.; Nyland, Kristina; Meier, David S.; Cales, Sabrina L.; Chang, Philip; Davis, Timothy A.; De Zeeuw, P. T.; Martín, Sergio

    2015-01-01

    NGC 1266 is a nearby lenticular galaxy that harbors a massive outflow of molecular gas powered by the mechanical energy of an active galactic nucleus (AGN). It has been speculated that such outflows hinder star formation (SF) in their host galaxies, providing a form of feedback to the process of galaxy formation. Previous studies, however, indicated that only jets from extremely rare, high-power quasars or radio galaxies could impart significant feedback on their hosts. Here we present detailed observations of the gas and dust continuum of NGC 1266 at millimeter wavelengths. Our observations show that molecular gas is being driven out of the nuclear region at M-dot {sub out}?110 M{sub ?} yr{sup –1}, of which the vast majority cannot escape the nucleus. Only 2 M {sub ?} yr{sup –1} is actually capable of escaping the galaxy. Most of the molecular gas that remains is very inefficient at forming stars. The far-infrared emission is dominated by an ultra-compact (? 50 pc) source that could either be powered by an AGN or by an ultra-compact starburst. The ratio of the SF surface density (?{sub SFR}) to the gas surface density (?{sub H{sub 2}}) indicates that SF is suppressed by a factor of ?50 compared to normal star-forming galaxies if all gas is forming stars, and ?150 for the outskirt (98%) dense molecular gas if the central region is powered by an ultra-compact starburst. The AGN-driven bulk outflow could account for this extreme suppression by hindering the fragmentation and gravitational collapse necessary to form stars through a process of turbulent injection. This result suggests that even relatively common, low-power AGNs are able to alter the evolution of their host galaxies as their black holes grow onto the M-? relation.

  13. Gamma Ray Bursts from delayed collapse of neutron stars to quark matter stars

    E-Print Network [OSTI]

    Z. Berezhiani; I. Bombaci; A. Drago; F. Frontera; A. Lavagno

    2003-02-13

    We propose a model to explain how a Gamma Rays Burst can take place days or years after a supernova explosion. Our model is based on the conversion of a pure hadronic star (neutron star) into a star made at least in part of deconfined quark matter. The conversion process can be delayed if the surface tension at the interface between hadronic and deconfined-quark-matter phases is taken into account. The nucleation time (i.e. the time to form a critical-size drop of quark matter) can be extremely long if the mass of the star is small. Via mass accretion the nucleation time can be dramaticaly reduced and the star is finally converted into the stable configuration. A huge amount of energy, of the order of 10$^{52}$--10$^{53}$ erg, is released during the conversion process and can produce a powerful Gamma Ray Burst. The delay between the supernova explosion generating the metastable neutron star and the new collapse can explain the delay proposed in GRB990705 and in GRB011211.

  14. Combustion of a hadronic star into a quark star: the turbulent and the diffusive regimes

    E-Print Network [OSTI]

    Alessandro Drago; Giuseppe Pagliara

    2015-06-27

    We argue that the full conversion of a hadronic star into a quark or a hybrid star occurs within two different regimes separated by a critical value of the density of the hadronic phase $\\overline{n_h}$. The first stage, occurring for $n_h>\\overline{n_h}$, is characterized by turbulent combustion and lasts typically a few ms. During this short time-scale neutrino cooling is basically inactive and the star heats up thanks to the heat released in the conversion. In the second stage, occurring for $n_h<\\overline{n_h}$, turbulence is not active anymore, and the conversion proceeds on a much longer time scale (of the order of tens of seconds), with a velocity regulated by the diffusion and the production of strange quarks. At the same time, neutrino cooling is also active. The interplay between the heating of the star due to the slow conversion of its outer layers (with densities smaller than $\\overline{n_h}$) and the neutrino cooling of the forming quark star leads to a quasi-plateau in the neutrino luminosity which, if observed, would possibly represent a unique signature for the existence of quark matter inside compact stars. We will discuss the phenomenological implications of this scenario in particular in connection with the time structure of long gamma-ray-bursts.

  15. STAR FORMATION IN THE TAURUS FILAMENT L 1495: FROM DENSE CORES TO STARS

    SciTech Connect (OSTI)

    Schmalzl, Markus; Kainulainen, Jouni; Henning, Thomas; Launhardt, Ralf; Quanz, Sascha P.; Alves, Joao; Goodman, Alyssa A.; Pineda, Jaime E.; Roman-Zuniga, Carlos G.

    2010-12-10

    We present a study of dense structures in the L 1495 filament in the Taurus Molecular Cloud and examine its star-forming properties. In particular, we construct a dust extinction map of the filament using deep near-infrared observations, exposing its small-scale structure in unprecedented detail. The filament shows highly fragmented substructures and a high mass-per-length value of M{sub line} = 17 M{sub sun} pc{sup -1}, reflecting star-forming potential in all parts of it. However, a part of the filament, namely B 211, is remarkably devoid of young stellar objects. We argue that in this region the initial filament collapse and fragmentation is still taking place and star formation is yet to occur. In the star-forming part of the filament, we identify 39 cores with masses from 0.4 to 10 M{sub sun} and preferred separations in agreement with the local Jeans length. Most of these cores exceed the Bonnor-Ebert critical mass, and are therefore likely to collapse and form stars. The dense core mass function follows a power law with exponent {Gamma} = 1.2 {+-} 0.2, a form commonly observed in star-forming regions.

  16. LoanSTAR After 11 Years: A Report on the Successes and Lessons Learned from the LoanSTAR Program 

    E-Print Network [OSTI]

    Haberl, J.; Claridge, D.; Turner, W. D.; O'Neal, D.; Heffington, W.; Verdict, M.

    2002-01-01

    lessons that have been learned that are not as highly publicized. This paper will present an overview of 11 years of measured savings from the LoanSTAR program, including the cost effectiveness of the LoanSTAR loans, trends in LoanSTAR funding, lessons...

  17. Radial Oscillations of Rotating Strange Stars in Strong Magnetic Fields

    E-Print Network [OSTI]

    S. Singh; N. Chandrika Devi; V. K. Gupta; Asha Gupta; J. D. Anand

    2000-12-20

    In this paper we study radial oscillations of rotating strange stars in strong magnetic fields in the Density Dependent Quark Mass (DDQM) model. We see that increase of frequency i.e. difference in frequency of rotating and non-rotating stars is more for higher magnetic fields. The change is small for low mass stars but it increases with the mass of the star. This change of frequency is significant for maximum mass whereas it is marginal for a 1.4 solar mass star.

  18. Dilatonic Equation of Hydrostatic Equilibrium and Neutron Star Structure

    E-Print Network [OSTI]

    S. H. Hendi; G. H. Bordbar; B. Eslam Panah; M. Najafi

    2015-06-30

    In this paper, we present a new hydrostatic equilibrium equation related to dilaton gravity. We consider a spherical symmetric metric to obtain the hydrostatic equilibrium equation of stars in $4$-dimensions, and generalize TOV equation to the case of regarding a dilaton field. Then, we calculate the structure properties of neutron star using our obtained hydrostatic equilibrium equation employing the modern equations of state of neutron star matter derived from microscopic calculations. We show that the maximum mass of neutron star depends on the parameters of dilaton field and cosmological constant. In other words, by setting the parameters of new hydrostatic equilibrium equation, we calculate the maximum mass of neutron star.

  19. The evolution of dusty Debris disks around solar type stars

    SciTech Connect (OSTI)

    Vican, Laura [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Schneider, Adam, E-mail: lvican@astro.ucla.edu, E-mail: aschneid@physast.uga.edu [Department of Physics and Astronomy, University of Georgia, Athens, GA 30602 (United States)

    2014-01-10

    We used chromospheric activity to determine the ages of 2820 field stars. We searched these stars for excess emission at 22 ?m with the Wide-Field Infrared Survey Explorer. Such excess emission is indicative of a dusty debris disk around a star. We investigated how disk incidence trends with various stellar parameters, and how these parameters evolve with time. We found 22 ?m excesses around 98 stars (a detection rate of 3.5%). Of these 98 excess sources, 74 are presented here for the first time. We also measured the abundance of lithium in eight dusty stars in order to test our stellar age estimates.

  20. Kepler observations of variability in B-type stars

    E-Print Network [OSTI]

    Balona, L A; De Cat, P; Handler, G; Gutierrez-Soto, J; Engelbrecht, C A; Frescura, F; Briquet, M; Cuypers, J; Daszynska-Daszkiewicz, J; Degroote, P; Dukes, R J; Garcia, R A; Green, E M; Heber, U; Kawaler, S D; Ostensen, R; Pricopi, D; Roxburgh, I; Salmon, S; Smith, M A; Suarez, J C; Suran, M; Szabo, R; Uytterhoeven, K; Christensen-Dalsgaard,; Kjeldsen, H; Caldwell, D A; Girouard, F R; Sanderfer, D T

    2011-01-01

    The analysis of the light curves of 48 B-type stars observed by Kepler is presented. Among these are 15 pulsating stars, all of which show low frequencies characteristic of SPB stars. Seven of these stars also show a few weak, isolated high frequencies and they could be considered as SPB/beta Cep hybrids. In all cases the frequency spectra are quite different from what is seen from ground-based observations. We suggest that this is because most of the low frequencies are modes of high degree which are predicted to be unstable in models of mid-B stars. We find that there are non-pulsating stars within the beta Cep and SPB instability strips. Apart from the pulsating stars, we can identify stars with frequency groupings similar to what is seen in Be stars but which are not Be stars. The origin of the groupings is not clear, but may be related to rotation. We find periodic variations in other stars which we attribute to proximity effects in binary systems or possibly rotational modulation. We find no evidence fo...

  1. NEW X-RAY DETECTIONS OF WNL STARS

    SciTech Connect (OSTI)

    Skinner, Stephen L.; Zhekov, Svetozar A.; Guedel, Manuel; Schmutz, Werner; Sokal, Kimberly R.

    2012-05-15

    Previous studies have demonstrated that putatively single nitrogen-type Wolf-Rayet stars (WN stars) without known companions are X-ray sources. However, almost all WN star X-ray detections so far have been of earlier WN2-WN6 spectral subtypes. Later WN7-WN9 subtypes (also known as WNL stars) have proved more difficult to detect, an important exception being WR 79a (WN9ha). We present here new X-ray detections of the WNL stars WR 16 (WN8h) and WR 78 (WN7h). These new results, when combined with previous detections, demonstrate that X-ray emission is present in WN stars across the full range of spectral types, including later WNL stars. The two WN8 stars observed to date (WR 16 and WR 40) show unusually low X-ray luminosities (L{sub x} ) compared to other WN stars, and it is noteworthy that they also have the lowest terminal wind speeds (v{sub {infinity}}). Existing X-ray detections of about a dozen WN stars reveal a trend of increasing L{sub x} with wind luminosity L{sub wind} = (1/2)M-dot v{sup 2}{sub {infinity}}, suggesting that wind kinetic energy may play a key role in establishing X-ray luminosity levels in WN stars.

  2. Cotton Variety Experiments, 1912-1920, Substation No. 7, Spur, Texas. 

    E-Print Network [OSTI]

    Freeman, George Fouche; Dickson, R. E

    1922-01-01

    . S. No. Variety 11. ...................... .Lone Star. 14. ...................... .Unknown Long Staple. 1.18.. ..................... .Long Staple. 128. ...................... .Mebane Triumph. 169 ........................ Webber. 411.... S. No. Variety ........................ 413 Snowflake. 414 ...................... :.Durango. ...................... 443. .Half and Half. ....................... 446. Simpkin's Prolific. ........................ 466 Webber. 469...

  3. Coloniality and Border(ed) Violence: San Diego, San Ysidro and the U-S///Mexico Border

    E-Print Network [OSTI]

    Hernandez, Roberto D

    2010-01-01

    the most notable example being The Alamo. 50 In a relatedwhether the Battle of the Alamo stands as “a moment of gloryLone Star, “Forget the Alamo! ” 52 Not surprisingly, the

  4. Reprocessing the Hipparcos data for evolved giant stars II. Absolute magnitudes for the R-type carbon stars

    E-Print Network [OSTI]

    G. R. Knapp; D. Pourbaix; A. Jorissen

    2001-03-09

    The Hipparcos Intermediate Astrometric Data for carbon stars have been reprocessed using an algorithm which provides an objective criterion for rejecting anomalous data points and constrains the parallax to be positive. New parallax solutions have been derived for 317 cool carbon stars, mostly of types R and N. In this paper we discuss the results for the R stars. The most important result is that the early R stars (i.e., R0 - R3) have absolute magnitudes and V-K colors locating them among red clump giants in the Hertzsprung-Russell diagram. Stars with subtypes R4 - R9 tend to be cooler and have similar luminosity to the N-type carbon stars, as confirmed by their position in the (J-H, H-K) color-color diagram. The sample of early R-type stars selected from the Hipparcos Catalogue appears to be approximately complete to magnitude K_0 ~ 7, translating into a completeness distance of 600 pc if all R stars had M_K= -2 (400 pc if M_K= -1). With about 30 early R-type stars in that volume, they comprise about 0.04% (0.14% for M_K= -1) of the red clump stars in the solar neighborhood. Identification with the red clump locates these stars at the helium core burning stage of stellar evolution, while the N stars are on the asymptotic giant branch, where helium shell burning occurs. The present analysis suggests that for a small fraction of the helium core burning stars (far lower than the fraction of helium shell-burning stars), carbon produced in the interior is mixed to the atmosphere in sufficient quantities to form a carbon star.

  5. Laser Guide Star Adaptive Optics without Tip-tilt

    E-Print Network [OSTI]

    R. Davies; S. Rabien; C. Lidman; M. Le Louarn; M. Kasper; N. M. Forster Schreiber; V. Roccatagliata; N. Ageorges; P. Amico; C. Dumas; F. Mannucci

    2008-01-24

    Adaptive optics (AO) systems allow a telescope to reach its diffraction limit at near infrared wavelengths. But to achieve this, a bright natural guide star (NGS) is needed for the wavefront sensing, severely limiting the fraction of the sky over which AO can be used. To some extent this can be overcome with a laser guide star (LGS). While the laser can be pointed anywhere in the sky, one still needs to have a natural star, albeit fainter, reasonably close to correct the image motion (tip-tilt) to which laser guide stars are insensitive. There are in fact many astronomical targets without suitable tip-tilt stars, but for which the enhanced resolution obtained with the Laser Guide Star Facility (LGSF) would still be very beneficial. This article explores what adaptive optics performance one might expect if one dispenses with the tip-tilt star, and in what situations this mode of observing might be needed.

  6. Hypervelocity binary stars: smoking gun of massive binary black holes

    E-Print Network [OSTI]

    Youjun Lu; Qingjuan Yu; D. N. C. Lin

    2007-07-22

    The hypervelocity stars recently found in the Galactic halo are expelled from the Galactic center through interactions between binary stars and the central massive black hole or between single stars and a hypothetical massive binary black hole. In this paper, we demonstrate that binary stars can be ejected out of the Galactic center with velocities up to 10^3 km/s, while preserving their integrity, through interactions with a massive binary black hole. Binary stars are unlikely to attain such high velocities via scattering by a single massive black hole or through any other mechanisms. Based on the above theoretical prediction, we propose a search for binary systems among the hypervelocity stars. Discovery of hypervelocity binary stars, even one, is a definitive evidence of the existence of a massive binary black hole in the Galactic center.

  7. Period change and stellar evolution of $\\beta$ Cephei stars

    E-Print Network [OSTI]

    Neilson, Hilding R

    2015-01-01

    The $\\beta$ Cephei stars represent an important class of massive star pulsators probing the evolution of B-type stars and the transition from main sequence to hydrogen-shell burning evolution. By understanding $\\beta$ Cep stars, we gain insights into the detailed physics of massive star evolution such as rotational mixing, convective core overshooting, magnetic fields and stellar winds, all of which play important roles. Similarly, modeling their pulsation provides additional information into their interior structures. Furthermore, measurements of the rate of change of pulsation period offer a direct measure of $\\beta$ Cephei stellar evolution. In this work, we compute state-of-the-art stellar evolution models assuming different amounts of initial rotation and convective core overshoot and measure theoretical rates of period change for which we compare to rates previously measured for a sample of $\\beta$ Cephei stars. The results of this comparison are mixed. For three stars, the rates are too small to infer ...

  8. Magnetic fields in non-convective regions of stars

    E-Print Network [OSTI]

    Braithwaite, J

    2015-01-01

    We review the current state of knowledge of magnetic fields inside stars, concentrating on recent developments concerning magnetic fields in stably stratified (zones of) stars, leaving out convective dynamo theories and observations of convective envelopes. We include the observational properties of A, B and O-type main-sequence stars, which have radiative envelopes, and the fossil field model which is normally invoked to explain the strong fields sometimes seen in these stars. Observations seem to show that Ap-type stable fields are excluded in stars with convective envelopes. Most stars contain both radiative and convective zones, and there are potentially important effects arising from the interaction of magnetic fields at the boundaries between them, the solar cycle being one of the better known examples. Related to this, we discuss whether the Sun could harbour a magnetic field in its core. Recent developments regarding the various convective and radiative layers near the surfaces of early-type stars and...

  9. Bare Quark Stars or Naked Neutron Stars ? The Case of RX J1856.5-3754

    E-Print Network [OSTI]

    Roberto Turolla; Silvia Zane; Jeremy J. Drake

    2003-11-21

    In a cool neutron star (T 1.e13 G), a phase transition may occur in the outermost layers. As a consequence the neutron star becomes `bare', i.e. no gaseous atmosphere sits on the top of the crust. The surface of a cooling, bare neutron star does not necessarily emit a blackbody spectrum because the emissivity is strongly suppressed at energies below the electron plasma frequency, omega_p. Since omega_p ~ 1 keV under the conditions typical of the denseelectron gas in the condensate, the emission from a T ~ 100 eV bare neutron star will be substantially depressed with respect to that of a perfect Planckian radiator at most energies. Here we present a detailed analysis of the emission properties of a bare neutron star. In particular, we derive the surface emissivity for a Fe composition in a range of magnetic fields and temperatures representative of cooling isolated neutron stars, like RX J1856.5-3754. We find that the emitted spectrum is strongly dependent on the electron conductivity in the solid surface layers. In the cold electron gas approximation (no electron-lattice interactions), the spectrum turns out to be a featureless depressed blackbody in the 0.1-2 keV band with a steeper low-energy distribution. When damping effects due to collisions between electrons and the ion lattice (mainly due to electron-phonon interactions) are accounted for, the spectrum is more depressed depending on the magnetic field strength. Details of the emitted spectrum are found, however, to be strongly dependent of the assumed treatment of the transition from the external vacuum to the metallic surface. The implications of out results to RX J1856.5-3754 and other isolated neutron stars are discussed.

  10. SPIN EVOLUTION OF ACCRETING YOUNG STARS. I. EFFECT OF MAGNETIC STAR-DISK COUPLING

    SciTech Connect (OSTI)

    Matt, Sean P.; Greene, Thomas P.; Pinzon, Giovanni; De la Reza, Ramiro E-mail: thomas.p.greene@nasa.go E-mail: delareza@on.b

    2010-05-10

    We present a model for the rotational evolution of a young, solar mass star interacting with an accretion disk. The model incorporates a description of the angular momentum transfer between the star and the disk due to a magnetic connection, and includes changes in the star's mass and radius and a decreasing accretion rate. The model also includes, for the first time in a spin evolution model, the opening of the stellar magnetic field lines, as expected to arise from twisting via star-disk differential rotation. In order to isolate the effect that this has on the star-disk interaction torques, we neglect the influence of torques that may arise from open field regions connected to the star or disk. For a range of magnetic field strengths, accretion rates, and initial spin rates, we compute the stellar spin rates of pre-main-sequence stars as they evolve on the Hayashi track to an age of 3 Myr. How much the field opening affects the spin depends on the strength of the coupling of the magnetic field to the disk. For the relatively strong coupling (i.e., high magnetic Reynolds number) expected in real systems, all models predict spin periods of less than {approx}3 days, in the age range of 1-3 Myr. Furthermore, these systems typically do not reach an equilibrium spin rate within 3 Myr, so that the spin at any given time depends upon the choice of initial spin rate. This corroborates earlier suggestions that, in order to explain the full range of observed rotation periods of approximately 1-10 days, additional processes, such as the angular momentum loss from powerful stellar winds, are necessary.

  11. Constraining the neutron star equation of state with gravitational wave signals from coalescing binary neutron stars

    E-Print Network [OSTI]

    Michalis Agathos; Jeroen Meidam; Walter Del Pozzo; Tjonnie G. F. Li; Marco Tompitak; John Veitch; Salvatore Vitale; Chris Van Den Broeck

    2015-07-12

    Recently exploratory studies were performed on the possibility of constraining the neutron star equation of state (EOS) using signals from coalescing binary neutron stars, or neutron star-black hole systems, as they will be seen in upcoming advanced gravitational wave detectors such as Advanced LIGO and Advanced Virgo. In particular, it was estimated to what extent the combined information from multiple detections would enable one to distinguish between different equations of state through hypothesis ranking or parameter estimation. Under the assumption of zero neutron star spins both in signals and in template waveforms and considering tidal effects to 1 post-Newtonian (1PN) order, it was found that O(20) sources would suffice to distinguish between a hard, moderate, and soft equation of state. Here we revisit these results, this time including neutron star tidal effects to the highest order currently known, termination of gravitational waveforms at the contact frequency, neutron star spins, and the resulting quadrupole-monopole interaction. We also take the masses of neutron stars in simulated sources to be distributed according to a relatively strongly peaked Gaussian, as hinted at by observations, but without assuming that the data analyst will necessarily have accurate knowledge of this distribution for use as a mass prior. We find that especially the effect of the latter is dramatic, necessitating many more detections to distinguish between different EOS and causing systematic biases in parameter estimation, on top of biases due to imperfect understanding of the signal model pointed out in earlier work. This would get mitigated if reliable prior information about the mass distribution could be folded into the analyses.

  12. Exploring the origin of magnetic fields in massive stars: II. New magnetic field measurements in cluster and field stars

    E-Print Network [OSTI]

    Hubrig, S; Ilyin, I; Kharchenko, N V; Oskinova, L M; Langer, N; Gonzalez, J F; Kholtygin, A F; Briquet, M

    2013-01-01

    Theories on the origin of magnetic fields in massive stars remain poorly developed, because the properties of their magnetic field as function of stellar parameters could not yet be investigated. To investigate whether magnetic fields in massive stars are ubiquitous or appear only in stars with a specific spectral classification, certain ages, or in a special environment, we acquired 67 new spectropolarimetric observations for 30 massive stars. Among the observed sample, roughly one third of the stars are probable members of clusters at different ages, whereas the remaining stars are field stars not known to belong to any cluster or association. Spectropolarimetric observations were obtained during four different nights using the low-resolution spectropolarimetric mode of FORS2 (FOcal Reducer low dispersion Spectrograph) mounted on the 8-m Antu telescope of the VLT. Furthermore, we present a number of follow-up observations carried out with the high-resolution spectropolarimeters SOFIN mounted at the Nordic O...

  13. NLTE wind models for SMC stars

    E-Print Network [OSTI]

    Jiri Krticka

    2005-09-15

    We study stellar wind properties of selected late O stars in the Small Magellanic Cloud (SMC). We calculate NLTE line-driven wind models for these stars and compare predicted wind parameters with observed values. We found satisfactory agreement between theoretical and observed terminal velocities. On the other hand, predicted and observed mass-loss rates are in a good agreement only for higher mass-loss rates. For mass-loss rates lower than approximately 10^{-7} M_sun / year we found large discrepancy between theoretical and observed values. We propose a new explanation of this effect based on dynamical decoupling of some atoms. Finally, we study the dependence of wind terminal velocities and mass-loss rates on metallicity.

  14. COALESCING NEUTRON STARS AS GAMMA RAY BURSTERS ?

    E-Print Network [OSTI]

    M. Ruffert; H. -Th. Janka; W. Keil; G. Schaefer

    1995-03-06

    We investigate the dynamics and evolution of coalescing neutron stars. The three-dimensional Newtonian equations of hydrodynamics are integrated by the `Piecewise Parabolic Method' However, we do include the effects of the emission of gravitational waves on the hydrodynamics. The properties of neutron star matter are described by the equation of state of Lattimer & Swesty. In addition to the fundamental hydrodynamic quantities, density, momentum, and energy, we follow the time evolution of the electron density in the stellar gas. Energy losses and changes of the electron abundance due to the emission of neutrinos are taken into account by an elaborate ``neutrino leakage scheme'', which employs a careful calculation of the lepton number and energy source terms of all neutrino types. The grid is Cartesian and equidistant with a resolution of 64**3 or 128**3, which allows us to calculate the self-gravity via fast Fourier transforms.

  15. Northern JHK Standard Stars for Array Detectors

    E-Print Network [OSTI]

    L. K. Hunt; F. Mannucci; L. Testi; S. Migliorini; R. M. Stanga; C. Baffa; F. Lisi; L. Vanzi

    1999-10-22

    We report J, H and K photometry of 86 stars in 40 fields in the northern hemisphere. The fields are smaller than or comparable to a 4x4 arcmin field-of-view, and are roughly uniformly distributed over the sky, making them suitable for a homogeneous broadband calibration network for near-infrared panoramic detectors. K magnitudes range from 8.5 to 14, and J-K colors from -0.1 to 1.2. The photometry is derived from a total of 3899 reduced images; each star has been measured, on average, 26.0 times per filter on 5.5 nights. Typical errors on the photometry are about 0.012.

  16. Reconstructing the Star Formation Histories of Galaxies

    E-Print Network [OSTI]

    Uta Fritze; Thomas Lilly

    2007-01-15

    We present a methodological study to find out how far back and to what precision star formation histories of galaxies can be reconstructed from CMDs, from integrated spectra and Lick indices, and from integrated multi-band photometry. Our evolutionary synthesis models GALEV allow to describe the evolution of galaxies in terms of all three approaches and we have assumed typical observational uncertainties for each of them and then investigated to what extent and accuracy different star formation histories can be discriminated. For a field in the LMC bar region with both a deep CMD from HST observations and a trailing slit spectrum across exactly the same field of view we could test our modelling results against real data.

  17. A SECOND NEUTRON STAR IN M4?

    SciTech Connect (OSTI)

    Kaluzny, J.; Rozanska, A.; Rozyczka, M.; Krzeminski, W. [Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw (Poland); Thompson, Ian B. [Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2012-05-01

    We show that the optical counterpart of the X-ray source CX 1 in M4 is a {approx}20th magnitude star, located in the color-magnitude diagram on (or very close to) the main sequence of the cluster, and exhibiting sinusoidal variations of the flux. We find the X-ray flux to be also periodically variable, with X-ray and optical minima coinciding. Stability of the optical light curve, lack of UV-excess, and unrealistic mean density resulting from period-density relation for semidetached systems speak against the original identification of CX 1 as a cataclysmic variable. We argue that the X-ray active component of this system is a neutron star (probably a millisecond pulsar).

  18. Shocks, Star Formation, and the JWST

    E-Print Network [OSTI]

    Gusdorf, Antoine

    2015-01-01

    The interstellar medium (ISM) is constantly evolving due to unremitting injection of energy in various forms. Energetic radiation transfers energy to the ISM: from the UV photons, emitted by the massive stars, to X- and $\\gamma$-ray ones. Cosmic rays are another source of energy. Finally, mechanical energy is injected through shocks or turbulence. Shocks are ubiquitous in the interstellar medium of galaxies. They are associated to star formation (through jets and bipolar outflows), life (via stellar winds), and death (in AGB stellar winds or supernovae explosion). The dynamical processes leading to the formation of molecular clouds also generate shocks where flows of interstellar matter collide. Because of their ubiquity, the study of interstellar shocks is also a useful probe to the other mechanisms of energy injection in the ISM. This study must be conducted in order to understand the evolution of the ISM as a whole, and to address various questions: what is the peculiar chemistry associated to shocks, and ...

  19. Hyperon ordering in neutron star matter

    E-Print Network [OSTI]

    L. Mornas; J. P. Suarez Curieses; J. Diaz Alonso

    2002-09-16

    We explore the possible formation of ordered phases in neutron star matter. In the framework of a quantum hadrodynamics model where neutrons, protons and Lambda hyperons interact via the exchange of mesons, we compare the energy of the usually assumed uniform, liquid phase, to that of a configuration in which di-lambda pairs immersed in an uniform nucleon fluid are localized on the nodes of a regular lattice. The confining potential is calculated self-consistently as resulting from the combined action of the nucleon fluid and the other hyperons, under the condition of beta equilibrium. We are able to obtain stable ordered phases for some reasonable sets of values of the model parameters. This could have important consequences on the structure and cooling of neutron stars.

  20. Entanglement Entropy of Magnetic Electron Stars

    E-Print Network [OSTI]

    Tameem Albash; Clifford V. Johnson; Scott MacDonald

    2015-04-08

    We study the behavior of the entanglement entropy in $(2+1)$--dimensional strongly coupled theories via the AdS/CFT correspondence. We consider theories at a finite charge density with a magnetic field, with their holographic dual being Einstein-Maxwell-Dilaton theory in four dimensional anti--de Sitter gravity. Restricting to black hole and electron star solutions at zero temperature in the presence of a background magnetic field, we compute their holographic entanglement entropy using the Ryu-Takayanagi prescription for both strip and disk geometries. In the case of the electric or magnetic zero temperature black holes, we are able to confirm that the entanglement entropy is invariant under electric-magnetic duality. In the case of the electron star with a finite magnetic field, for the strip geometry, we find a discontinuity in the first derivative of the entanglement entropy as the strip width is increased.

  1. Electromagnetic Jets from Stars and Black Holes

    E-Print Network [OSTI]

    Samuel E. Gralla; Alexandru Lupsasca; Maria J. Rodriguez

    2015-04-08

    We present analytic force-free solutions modeling rotating stars and black holes immersed in the magnetic field of a thin disk that terminates at an inner radius. The solutions are exact in flat spacetime and approximate in Kerr spacetime. The compact object produces a conical jet whose properties carry information about its nature. For example, the jet from a star is surrounded by a current sheet, while that of a black hole is smooth. We compute an effective resistance in each case and compare to the canonical values used in circuit models of energy extraction. These solutions illustrate all of the basic features of the Blandford-Znajek process for energy extraction and jet formation in a clean setting.

  2. Electromagnetic Jets from Stars and Black Holes

    E-Print Network [OSTI]

    Gralla, Samuel E; Rodriguez, Maria J

    2015-01-01

    We present analytic force-free solutions modeling rotating stars and black holes immersed in the magnetic field of a thin disk that terminates at an inner radius. The solutions are exact in flat spacetime and approximate in Kerr spacetime. The compact object produces a conical jet whose properties carry information about its nature. For example, the jet from a star is surrounded by a current sheet, while that of a black hole is smooth. We compute an effective resistance in each case and compare to the canonical values used in circuit models of energy extraction. These solutions illustrate all of the basic features of the Blandford-Znajek process for energy extraction and jet formation in a clean setting.

  3. Topological characterization of neutron star crusts

    E-Print Network [OSTI]

    C. O. Dorso; P. A. Giménez Molinelli; J. A. López

    2012-08-23

    Neutron star crusts are studied using a classical molecular dynamics model developed for heavy ion reactions. After the model is shown to produce a plethora of the so-called "pasta" shapes, a series of techniques borrowed from nuclear physics, condensed matter physics and topology are used to craft a method that can be used to characterize the shape of the pasta structures in an unequivocal way.

  4. Folk Song 2, Sun, Moon, and Star

    E-Print Network [OSTI]

    Sgrol dkar skyid

    Literature Project staff on Wednesday, Tuesday, June 8, 2010 Accession Form for Individual Recordings: Collection / Collector Name Sitaigou Village Tibetan Collection/ Sgrol dkar skyid ?????????/??? ???????????????????????????????????? ???????????? Tape... No. / Track / Item No. Sitaigou Tibetan Folk Song 2.WAV Length of track 00:02:40 Related tracks (include description/relationship if appropriate) Title of track Sun?Moon, and Star ???????? ???????????? Translation of title Description (to be used...

  5. Superbubble Activity in Star-Forming Galaxies

    E-Print Network [OSTI]

    M. S. Oey

    2002-12-03

    Mechanical feedback from massive stars, primarily from supernovae, can dominate ISM structuring and phase balance, thereby profoundly affecting galactic evolutionary processes. Our understanding of mechanical feedback is based on the adiabatic, wind-driven bubble model, applied on size scales ranging over three decades. Tests of the model, and our consequent understanding of feedback, are reviewed. While the model is broadly successful, critical unknowns still prevent a comprehensive understanding of the consequences of feedback.

  6. Asymmetric nuclear matter and neutron star properties

    E-Print Network [OSTI]

    L. Engvik; M. Hjorth-Jensen; E. Osnes; G. Bao; E. Oestgaard

    1994-06-23

    We calculate properties of neutron stars such as mass and radius using a relativistic Dirac-Brueckner-hartree-Fock apprach for asymmetric nuclear matter. For pure neutron matter we find the maximum mass to be 2.4 solar masses with a radius of 12 km. For a proton fraction of 30% we find a max mass of 2.1 solar masses and a radius of 10.5 km. The implications are discussed.

  7. Energy Star Concepts for Highway Vehicles

    SciTech Connect (OSTI)

    Greene, D.L.

    2003-06-24

    The authors of this report, under the sponsorship of the U.S. Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy (EERE) Weatherization and Intergovernmental Program, have investigated the possible application of Energy Star ratings to passenger cars and light trucks. This study establishes a framework for formulating and evaluating Energy Star rating methods that is comprised of energy- and environmental-based metrics, potential vehicle classification systems, vehicle technology factors, and vehicle selection criteria. The study tests several concepts and Energy Star rating methods using model-year 2000 vehicle data--a spreadsheet model has been developed to facilitate these analyses. This study tests two primary types of rating systems: (1) an outcome-based system that rates vehicles based on fuel economy, GHG emissions, and oil use and (2) a technology-based system that rates vehicles based on the energy-saving technologies they use. Rating methods were evaluated based on their ability to select vehicles with high fuel economy, low GHG emissions, and low oil use while preserving a full range of service (size and acceleration) and body style choice. This study concludes that an Energy Star rating for passenger cars and light trucks is feasible and that several methods could be used to achieve reasonable tradeoffs between low energy use and emissions and diversity in size, performance, and body type. It also shows that methods that consider only fuel economy, GHG emissions, or oil use will not select a diverse mix of vehicles. Finally, analyses suggest that methods that encourage the use of technology only, may result in increases in acceleration power and weight rather than reductions in oil use and GHG emissions and improvements in fuel economy.

  8. The Dark Energy Star and Stability analysis

    E-Print Network [OSTI]

    Piyali Bhar; Farook Rahaman

    2015-01-12

    We have proposed a new model of dark energy star consisting of five zones namely, solid core of constant energy density, the thin shell between core and interior, an inhomogeneous interior region with anisotropic pressures, thin shell and the exterior vacuum region. We have discussed various physical properties. The model satisfies all the physical requirements. The stability condition under small linear perturbation has also been discussed.

  9. Pulsations of rapidly rotating stars: II. Realistic modelling for intermediate-mass stars

    E-Print Network [OSTI]

    Ouazzani, Rhita-Maria; Dupret, Marc-Antoine

    2015-01-01

    Very high precision seismic space missions such as CoRoT and Kepler provide the means for testing the modelling of transport processes in stellar interiors. For some stars, such as $\\delta$ Scuti $\\gamma$ Doradus and Be stars, for instance, the observed pulsation spectra are modified by rotation to such an extent that it prevents any fruitful interpretation. Our aim is to characterise acoustic pulsation spectra of realistic stellar models in order to be able to interpret asteroseismic data from such stars. The 2-dimensional oscillation code ACOR, which treats rotation in a non-perturbative manner, is used to study pulsation spectra of highly distorted evolved models of stars. 2D models of stars are obtained by a self-consistent method which distorts spherically averaged stellar models a posteriori, at any stage of evolution, and for any type of rotation law. Four types of modes are calculated in a very dense frequency spectrum, among which are island modes. The regularity of the island modes spectrum is confi...

  10. Obscured clusters.I. GLIMPSE30 - Young Milky Way Star Cluster Hosting Wolf-Rayet Stars

    E-Print Network [OSTI]

    Kurtev, R; Georgiev, L; Ortolani, S; Ivanov, V D

    2007-01-01

    Young massive clusters are perfect astrophysical laboratories for study of massive stars. Clusters with Wolf-Rayet (WR) stars are of special importance, since this enables us to study a coeval WR population at a uniform metallicity and known age. GLIMPSE30 (G30) is one of them. The cluster is situated near the Galactic plane (l=298.756deg, b=-0.408deg) and we aimed to determine its physical parameters and to investigate its high-mass stellar content and especially WR stars. Our analysis is based on SOFI/NTT JsHKs imaging and low resolution (R~2000) spectroscopy of the brightest cluster members in the K atmospheric window. For the age determination we applied isochrone fits for MS and Pre-MS stars. We derived stellar parameters of the WR stars candidates using a full nonLTE modeling of the observed spectra. Using a variety of techniques we found that G30 is very young cluster, with age t~4Myr. The cluster is located in Carina spiral arm, it is deeply embedded in dust and suffers reddening of Av~10.5+-1.1mag. T...

  11. Combustion of a hadronic star into a quark star: the turbulent and the diffusive regimes

    E-Print Network [OSTI]

    Drago, Alessandro

    2015-01-01

    We argue that the full conversion of a hadronic star into a quark or a hybrid star occurs within two different regimes separated by a critical value of the density of the hadronic phase $\\overline{n_h}$. The first stage, occurring for $n_h>\\overline{n_h}$, is characterized by turbulent combustion and lasts typically a few ms. During this short time-scale neutrino cooling is basically inactive and the star heats up thanks to the heat released in the conversion. In the second stage, occurring for $n_h<\\overline{n_h}$, turbulence is not active anymore, and the conversion proceeds on a much longer time scale (of the order of tens of seconds), with a velocity regulated by the diffusion and the production of strange quarks. At the same time, neutrino cooling is also active. The interplay between the heating of the star due to the slow conversion of its outer layers (with densities smaller than $\\overline{n_h}$) and the neutrino cooling of the forming quark star leads to a quasi-plateau in the neutrino luminosity...

  12. Classical T Tauri stars: magnetic fields, coronae, and star-disc interactions

    E-Print Network [OSTI]

    Johnstone, C P; Gregory, S G; Donati, J -F; Hussain, G

    2013-01-01

    The magnetic fields of young stars set their coronal properties and control their spin evolution via the star-disc interaction and outflows. Using 14 magnetic maps of 10 classical T Tauri stars (CTTSs) we investigate their closed X-ray emitting coronae, their open wind-bearing magnetic fields, and the geometry of magnetospheric accretion flows. The magnetic fields of all the CTTSs are multipolar. Stars with simpler (more dipolar) large-scale magnetic fields have stronger fields, are slower rotators, and have larger X-ray emitting coronae compared to stars with more complex large-scale magnetic fields. The field complexity controls the distribution of open and closed field regions across the stellar surface, and strongly influences the location and shapes of accretion hot spots. However, the higher order field components are of secondary importance in determining the total unsigned open magnetic flux, which depends mainly on the strength of the dipole component and the stellar surface area. Likewise, the dipol...

  13. Eruptive Mass Loss in Very Massive Stars and Population III Stars

    E-Print Network [OSTI]

    Nathan Smith

    2006-07-24

    I discuss the role played by short-duration eruptive mass loss in the evolution of very massive stars. Giant eruptions of Luminous Blue Variables (LBVs) like the 19th century event of eta Carinae can remove large quantities of mass almost instantaneously, making them significant in stellar evolution. They can potentially remove much more mass from the star than line-driven winds, especially if stellar winds are highly clumped such that previous estimates of O star mass-loss rates need to be revised downward. When seen in other galaxies as ``supernova impostors'', these LBV eruptions typically last for less than a decade, and they can remove of order 10 Msun as indicated by massive nebulae around LBVs. Such extreme mass-loss rates cannot be driven by radiation pressure on spectral lines, because the lines will completely saturate during the events. Instead, these outbursts must either be continuum-driven super-Eddington winds or outright hydrodynamic explosions, both of which are insensitive to metallicity. As such, this eruptive mode of mass loss could also play a pivotal role in the evolution and ultimate fate of massive metal-poor stars in the early universe. If they occur in these Population III stars, such eruptions would also profoundly affect the chemical yield and types of remnants from early supernovae and hypernovae thought to be the origin of long gamma ray bursts.

  14. Star Formation Histories in the Local Group

    E-Print Network [OSTI]

    Thomas M. Brown

    2004-07-09

    Deep color magnitude diagrams extending to the main sequence provide the most direct measure of the detailed star formation history in a stellar population. With large investments of observing time, HST can obtain such data for populations out to 1 Mpc, but its field of view is extremely small in comparison to the size of Local Group galaxies. This limitation severely constrains our understanding of galaxy formation. For example, the largest galaxy in the Local Group, Andromeda, offers an ideal laboratory for studying the formation of large spiral galaxies, but the galaxy shows substructure on a variety of scales, presumably due to its violent merger history. Within its remaining lifetime, HST can only sample a few sight-lines through this complex galaxy. In contrast, a wide field imager could provide a map of Andromeda's halo, outer disk, and tidal streams, revealing the spatially-dependent star formation history in each structure. The same data would enable many secondary studies, such as the age variation in Andromeda's globular cluster system, gigantic samples of variable stars, and microlensing tracers of the galaxy's dark matter distribution.

  15. GAPS IN THE GD-1 STAR STREAM

    SciTech Connect (OSTI)

    Carlberg, R. G. [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Grillmair, C. J., E-mail: carlberg@astro.utoronto.ca, E-mail: carl@ipac.caltech.edu [Spitzer Science Center, 1200 East California Boulevard, Pasadena, CA 91125 (United States)

    2013-05-10

    GD-1 is a long, thin, Milky Way star stream that has readily visible density variations along its length. We quantify the locations, sizes, and statistical significance of the density structure, i.e., gaps, using a set of scaled filters. The shapes of the filters are based on the gaps that develop in simulations of dark matter sub-halos crossing a star stream. The high Galactic latitude 8.4 kpc long segment of GD-1 that we examine has 8 {+-} 3 gaps of 99% significance or greater, with the error estimated on the basis of tests of the gap-filtering technique. The cumulative distribution of gaps more than three times the width of the stream is in good agreement with predictions for dark matter sub-halo encounters with cold star streams. The number of gaps narrower than three times the width of the GD-1 stream falls well below the cold stream prediction which is taken into account for the gap creation rate integrated over all sizes. Simple warm stream simulations scaled to GD-1 show that the falloff in gaps is expected for sub-halos below a mass of 10{sup 6} M{sub Sun }. The GD-1 gaps requires 100 sub-halos >10{sup 6} M{sub Sun} within 30 kpc, the apocenter of GD-1 orbit. These results are consistent with LCDM sub-halo predictions but further improvements in stream signal-to-noise and gap modeling will be welcome.

  16. On star formation in primordial protoglobular clouds

    E-Print Network [OSTI]

    Paolo Padoan; Raul Jimenez; Bernard Jones

    1996-04-11

    Using a new physical model for star formation (Padoan 1995) we have tested the possibility that globular clusters (GCs) are formed from primordial mass fluctuations, whose mass scale ($10^8$ - $10^9$ M$_{\\odot}$) is selected out of a CDM spectrum by the mechanism of non-equilibrium formation of $H_2$. We show that such clouds are able to convert about 0.003 of their total mass into a bound system (GC) and about 0.02 into halo stars. The metal enriched gas is dispersed away from the GC by supernova explosions and forms the galactic disk. These mass ratios between GCs, halo and disk depend on the predicted IMF which is a consequence of the universal statistics of fluid turbulence. They also depend on the ratio of baryonic over non-baryonic mass ,$X_b$, and are comparable with the values observed in typical spiral galaxies for $X_b \\approx 0.1-0.2$. The computed mass and radius for a GC ( $5\\times 10^5$ M$_{\\odot}$ and 30 pc) are in good agreement with the average values in the Galaxy. The model predicts an exponential cut off in the stellar IMF below 0.1 M$_{\\odot}$ in GCs and 0.6 M$_{\\odot}$ in the halo. The quite massive star formation in primordial clouds leads to a large number of supernovae and to a high blue luminosity during the first two Gyr of the life of every galaxy.

  17. The H? profiles of Be shell stars

    SciTech Connect (OSTI)

    Silaj, J.; Jones, C. E.; Sigut, T. A. A.; Tycner, C.

    2014-11-01

    A new set of theoretical H? emission line profiles of Be stars has been computed using the code BERAY, which solves the transfer equation along a series of rays passing through the star+disk system, representing an improved treatment over earlier work done by the authors. The new profiles were compared with the previous work, and general trends (such as line profile shapes and correlations between line equivalent widths as a function of initial density ?{sub 0} and power law index n) were recovered. Additionally, BERAY was employed to model the spectra of eight well-known Be shell stars. Some degeneracy was found in the choice of model parameters, highlighting the need to employ alternate observables to constrain the models. However, the inclination angle of the model seemed relatively insensitive to the choices of other parameters, and we show that, with our models, only a very small range of inclination angles can adequately reproduce the observations. Five of our eight targets were found to have inclination angles of 70° or higher, and two more were found to have inclination angles of 67° and 65°. The observation of one target—4 Aquilae—could only be reproduced by models created at an inclination angle of approximately 45°.

  18. Gravitational microlensing of stars with transiting planets

    E-Print Network [OSTI]

    Geraint F. Lewis

    2001-10-17

    If planetary systems are ubiquitous then a fraction of stars should possess a transiting planet when being microlensed. This paper presents a study of the influence of such planets on microlensing light curves. For the giant planets recently identified, the deviations in the light curve can be substantial, although the specifics of the perturbations are dependent upon the radius of the planet relative to that of the star, the location of the planet over the stellar surface and the orientation of the sweeping caustic. Given that the instantaneous probability of transiting hot-Jupiter like planets is small, less than a percent, and only a proportion of microlensing events exhibit caustic crossing events, the probability of detecting a transiting planet during a microlensing event is small, $\\sim10^{-6}$. However, a number of factors influencing this probability, such as the number of solar type star that possess planets, are uncertain, and the prospect of detecting transiting planets in future large catalogues of microlensing light curves may be viable. The results of this study also have bearing on the gravitational microlensing of spots on the stellar surface.

  19. Intergalactic stars in the Fornax Cluster

    E-Print Network [OSTI]

    Tom Theuns; S. J. Warren

    1996-09-10

    We have identified ten candidate intergalactic planetary nebulae in the Fornax galaxy cluster. These objects were found during observations in 1992 and 1993 in three fields chosen well away from any Fornax galaxy at 15 arcmin, 30 arcmin, and 45 arcmin from the centre of Fornax. We used the usual method of blinking images taken in a narrow OIII filter, with images taken in an adjacent broad filter. The measured fluxes in the narrow, broad, and I bands are consistent with these unresolved objects being planetary nebulae immersed in an intergalactic population of stars. Such a population is expected to arise as a consequence of tidal encounters between galaxies, and our findings strengthen the case for the existence of such tidal debris. The confirmation of some or all of these ten candidates as planetary nebulae would imply that intergalactic stars constitute a substantial fraction of all the stars in Fornax, up to an estimated 40 per cent. Intergalactic planetary nebulae could prove useful in probing the underlying cluster potential, since they would be far more abundant than galaxies. We discuss possible contamination of the sample by emission-line galaxies, but conclude that planetary nebulae is the most likely identification for the detected objects. keywords: intergalactic medium-- galaxies: interactions -- planetary nebulae: general -- clusters: individual: Fornax

  20. Massive Stars in the W33 Giant Molecular Complex

    E-Print Network [OSTI]

    Messineo, Maria; Figer, Donald F; Kudritzki, Rolf-Peter; Najarro, Francisco; Rich, R Michael; Menten, Karl M; Ivanov, Valentin D; Valenti, Elena; Trombley, Christine; Chen, C -H Rosie; Davies, Ben

    2015-01-01

    Rich in HII regions, giant molecular clouds are natural laboratories to study massive stars and sequential star formation. The Galactic star forming complex W33 is located at l=~12.8deg and at a distance of 2.4 kpc, has a size of ~10 pc and a total mass of (~0.8 - ~8.0) X 10^5 Msun. The integrated radio and IR luminosity of W33 - when combined with the direct detection of methanol masers, the protostellar object W33A, and protocluster embedded within the radio source W33 main - mark the region out as a site of vigorous ongoing star formation. In order to assess the long term star formation history, we performed an infrared spectroscopic search for massive stars, detecting for the first time fourteen early-type stars, including one WN6 star and four O4-7 stars. The distribution of spectral types suggests that this population formed during the last ~2-4 Myr, while the absence of red supergiants precludes extensive star formation at ages 6-30 Myr. This activity appears distributed throughout the region and does ...

  1. Neutron-capture nucleosynthesis in the first stars

    SciTech Connect (OSTI)

    Roederer, Ian U. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Preston, George W.; Thompson, Ian B.; Shectman, Stephen A. [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Sneden, Christopher, E-mail: iur@umich.edu [Department of Astronomy, University of Texas at Austin, 1 University Station C1400, Austin, TX 78712 (United States)

    2014-04-01

    Recent studies suggest that metal-poor stars enhanced in carbon but containing low levels of neutron-capture elements may have been among the first to incorporate the nucleosynthesis products of the first generation of stars. We have observed 16 stars with enhanced carbon or nitrogen using the MIKE Spectrograph on the Magellan Telescopes at Las Campanas Observatory and the Tull Spectrograph on the Smith Telescope at McDonald Observatory. We present radial velocities, stellar parameters, and detailed abundance patterns for these stars. Strontium, yttrium, zirconium, barium, europium, ytterbium, and other heavy elements are detected. In four stars, these heavy elements appear to have originated in some form of r-process nucleosynthesis. In one star, a partial s-process origin is possible. The origin of the heavy elements in the rest of the sample cannot be determined unambiguously. The presence of elements heavier than the iron group offers further evidence that zero-metallicity rapidly rotating massive stars and pair instability supernovae did not contribute substantial amounts of neutron-capture elements to the regions where the stars in our sample formed. If the carbon- or nitrogen-enhanced metal-poor stars with low levels of neutron-capture elements were enriched by products of zero-metallicity supernovae only, then the presence of these heavy elements indicates that at least one form of neutron-capture reaction operated in some of the first stars.

  2. Explosive Combustion of a Neutron Star into a Quark Star: the non-premixed scenario

    E-Print Network [OSTI]

    Ouyed, Rachid; Jaikumar, Prashanth

    2013-01-01

    We review aspects of the hydrodynamical combustion of nuclear matter to strange quark matter in a neutron star. Numerical studies on non-premixed combustion that consistently include hydrodynamical flows in a reactive-diffusive setup show that in 1D, the conversion (burning) front moves at sub-sonic speeds and stops short of converting the entire star to SQM, essentially due to advective forces. However, in the process, we also find that neutrino cooling of the interface causes it to wrinkle, laying a platform for a deflagrative-to-detonative transition (DDT). We outline progress on improvements in the burning code (Burn-UD: http://quarknova.ucalgary.ca/software/Burn-UD/) that will ultimately reveal the mechanism that can explode the outermost layers of even a dense compact object like a neutron star.

  3. Cooling of neutron stars and hybrid stars with a stiff hadronic EoS

    E-Print Network [OSTI]

    H. Grigorian; D. Blaschke; D. N. Voskresensky

    2015-03-16

    Within the "nuclear medium cooling" scenario of neutron stars all reliably known temperature - age data, including those of the central compact objects in the supernova remnants of Cassiopeia A and XMMU-J1732, can be comfortably explained by a set of cooling curves obtained by variation of the star mass within the range of typical observed masses. The recent measurements of the high masses of the pulsars PSR J1614-2230 and PSR J0348-0432 on the one hand, and of the low masses for PSR J0737-3039B and the companion of PSR J1756-2251 on the other, provide independent proof for the existence of neutron stars with masses in a broad range from $\\sim 1.2$ to 2 $M_\\odot$. The values $M>2 M_{\\odot}$ call for sufficiently stiff equations of state for neutron star matter. We investigate the response of the set of neutron star cooling curves to a stiffening of the nuclear equation of state so that maximum masses of about $2.4 M_\\odot$ would be accessible and to a deconfinement phase transition from such stiff nuclear matter in the outer core to color superconducting quark matter in the inner core. Without readjustment of cooling inputs the mass range required to cover all cooling data for the stiff DD2 equation of state should include masses of $2.426 M_\\odot$ for describing the fast cooling of CasA while the existence of a quark matter core accelerates the cooling so that CasA cooling data are described with a hybrid star of mass $1.674 M_\\odot$.

  4. Magnetic field studies of massive main sequence stars

    E-Print Network [OSTI]

    Schoeller, M; Ilyin, I; Kharchenko, N V; Briquet, M; Langer, N; Oskinova, L M

    2011-01-01

    We report on the status of our spectropolarimetric observations of massive stars. During the last years, we have discovered magnetic fields in many objects of the upper main sequence, including Be stars, beta Cephei and Slowly Pulsating B stars, and a dozen O stars. Since the effects of those magnetic fields have been found to be substantial by recent models, we are looking into their impact on stellar rotation, pulsation, stellar winds, and chemical abundances. Accurate studies of the age, environment, and kinematic characteristics of the magnetic stars are also promising to give us new insight into the origin of the magnetic fields. Furthermore, longer time series of magnetic field measurements allow us to observe the temporal variability of the magnetic field and to deduce the stellar rotation period and the magnetic field geometry. Studies of the magnetic field in massive stars are indispensable to understand the conditions controlling the presence of those fields and their implications on the stellar phy...

  5. STAR FORMATION AROUND SUPERGIANT SHELLS IN THE LARGE MAGELLANIC CLOUD

    SciTech Connect (OSTI)

    Book, Laura G.; Chu Youhua; Gruendl, Robert A.; Fukui, Yasuo

    2009-03-15

    We examine the recent star formation associated with four supergiant shells in the Large Magellanic Cloud (LMC): LMC 1, 4, 5, and 6, which have been shown to have simple expanding-shell structures. H II regions and OB associations are used to infer star formation in the last few Myr, while massive young stellar objects reveal the current ongoing star formation. Distributions of ionized H I and molecular components of the interstellar gas are compared with the sites of recent and current star formation to determine whether triggering has taken place. We find that a great majority of the current star formation has occurred in gravitationally unstable regions, and that evidence of triggered star formation is prevalent at both large and local scales.

  6. IAU Commission 37 "Star Clusters and Associations" Legacy report

    E-Print Network [OSTI]

    Carraro, Giovanni; Elmegreen, Bruce; Anthony-Twarog, Barbara; Geisler, Douglas; Goodwin, Simon; Stetson, Peter; Minniti, Dante

    2015-01-01

    It is widely accepted that stars do not form in isolation but result from the fragmentation of molecular clouds, which in turn leads to star cluster formation. Over time, clusters dissolve or are destroyed by interactions with molecular clouds or tidal stripping, and their members become part of the general field population. Star clusters are thus among the basic building blocks of galaxies. In turn, star cluster populations, from young associations and open clusters to old globulars, are powerful tracers of the formation, assembly, and evolutionary history of their parent galaxies. Although their importance had been recognised for decades, major progress in this area has only become possible in recent years, both for Galactic and extragalactic cluster populations. Star clusters are the observational foundation for stellar astrophysics and evolution, provide essential tracers of galactic structure, and are unique stellar dynamical environments. Star formation, stellar structure, stellar evolution, and stellar...

  7. HgMn Stars as apparent X-ray emitters

    E-Print Network [OSTI]

    Hubrig, S; Mathys, G

    1998-01-01

    In the ROSAT all-sky survey 11 HgMn stars were detected as soft X-ray emitters (Berghoefer, Schmitt & Cassinelli 1996). Prior to ROSAT, X-ray observations with the Einstein Observatory had suggested that stars in the spectral range B5-A7 are devoid of X-ray emission. Since there is no X-ray emitting mechanism available for these stars (also not for HgMn stars), the usual argument in the case of an X-ray detected star of this spectral type is the existence of an unseen low-mass companion which is responsible for the X-ray emission. The purpose of the present work is to use all available data for our sample of X-ray detected HgMn stars and conclude on the nature of possible companions.

  8. Dark matter transport properties and rapidly rotating neutron stars

    E-Print Network [OSTI]

    C. J. Horowitz

    2012-05-16

    Neutron stars are attractive places to look for dark matter because their high densities allow repeated interactions. Weakly interacting massive particles (WIMPs) may scatter efficiently in the core or in the crust of a neutron star. In this paper we focus on WIMP contributions to transport properties, such as shear viscosity or thermal conductivity, because these can be greatly enhanced by long mean free paths. We speculate that WIMPs increase the shear viscosity of neutron star matter and help stabilize r-mode oscillations. These are collective oscillations where the restoring force is the Coriolis force. At present r-modes are thought to be unstable in many observed rapidly rotating stars. If WIMPs stabilize the r-modes, this would allow neutron stars to spin rapidly. This likely requires WIMP-nucleon cross sections near present experimental limits and an appropriate density of WIMPs in neutron stars.

  9. Magnetic fields, spots and weather in chemically peculiar stars

    E-Print Network [OSTI]

    O. Kochukhov

    2007-11-30

    New observational techniques and sophisticated modelling methods has led to dramatic breakthroughs in our understanding of the interplay between the surface magnetism, atomic diffusion and atmospheric dynamics in chemically peculiar stars. Magnetic Doppler images, constructed using spectropolarimetric observations of Ap stars in all four Stokes parameters, reveal the presence of small-scale field topologies. Abundance Doppler mapping has been perfected to the level where distributions of many different chemical elements can be deduced self-consistently for one star. The inferred chemical spot structures are diverse and do not always trace underlying magnetic field geometry. Moreover, horizontal chemical inhomogeneities are discovered in non-magnetic CP stars and evolving chemical spots are observed for the first time in the bright mercury-manganese star alpha And. These results show that in addition to magnetic fields, another important non-magnetic structure formation mechanism acts in CP stars.

  10. [?/Fe] ABUNDANCES OF FOUR OUTER M31 HALO STARS

    SciTech Connect (OSTI)

    Vargas, Luis C.; Geha, Marla; Tollerud, Erik J. [Department of Astronomy, Yale University, 260 Whitney Avenue, New Haven, CT 06511 (United States); Gilbert, Karoline M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Kirby, Evan N. [California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, CA 91125 (United States); Guhathakurta, Puragra, E-mail: luis.vargas@yale.edu [UCO/Lick Observatory and Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2014-12-10

    We present alpha element to iron abundance ratios, [?/Fe], for four stars in the outer stellar halo of the Andromeda Galaxy (M31). The stars were identified as high-likelihood field halo stars by Gilbert et al. and lie at projected distances between 70 and 140 kpc from M31's center. These are the first alpha abundances measured for a halo star in a galaxy beyond the Milky Way. The stars range in metallicity between [Fe/H] = –2.2 and [Fe/H] = –1.4. The sample's average [?/Fe] ratio is +0.20 ± 0.20. The best-fit average value is elevated above solar, which is consistent with rapid chemical enrichment from Type II supernovae. The mean [?/Fe] ratio of our M31 outer halo sample agrees (within the uncertainties) with that of Milky Way inner/outer halo stars that have a comparable range of [Fe/H].

  11. ZZ Ceti Stars: Fractal Analogues of Excited Helium Ions?

    E-Print Network [OSTI]

    R. L. Oldershaw

    2006-02-20

    Multi-periodic pulsation phenomena of ZZ Ceti variable stars are analyzed within the context of a fractal cosmological paradigm that emphasizes discrete self-similarity in nature. A quantitative test comparing relevant stellar and atomic periods provides preliminary support for the analysis. This paper completes a 3-part series that explores the possibility of discrete cosmological self-similarity in variable stars; the first and second papers discussed RR Lyrae and delta Scuti stars, respectively.

  12. Resolving subdwarf B stars in binaries by HST imaging

    E-Print Network [OSTI]

    U. Heber; S. Moehler; R. Napiwotzki; P. Thejll; E. M. Green

    2002-01-07

    The origin of subluminous B stars is still an unsolved problem in stellar evolution. Single star as well as close binary evolution scenarios have been invoked but until now have met with little success. We have carried out a small survey of spectroscopic binary candidates (19 systems consisting of an sdB star and late type companion) with the Planetary Camera of the WFPC2 onboard Hubble Space Telescope to test these scenarios. Monte Carlo simulations indicate that by imaging the programme stars in the R-band about one third of the sample (6-7 stars) should be resolved at a limiting angular resolution of 0.1" if they have linear separations like main sequence stars ("single star evolution"). None should be resolvable if all systems were produced by close binary evolution. In addition we expect three triple systems to be present in our sample. Most of these, if not all, should be resolvable. Components were resolved in 6 systems with separations between 0.2" and 4.5". However, only in two systems do the magnitudes of the resolved components match the expectations from the deconvolution of the spectral energy distribution. These two stars could be physical binaries whereas in the other cases the nearby star may be a chance projection or a third component. Radial velocity measurements indicate that the resolved system TON 139 is a triple system, with the sdB having a close companion that does not contribute detectably to the integrated light of the system. Accordingly the success rate would be only 5% which is clearly below the prediction for single star evolution. We conclude that the distribution of separations of sdB binaries deviates strongly from that of normal stars. Our results add further evidence that close binary evolution is fundamental for the evolution of sdB stars. (abbreviated)

  13. Radio Observations of Masers in Post-AGB Stars

    E-Print Network [OSTI]

    R. M. Deacon; A. J. Green; J. M. Chapman

    2003-10-02

    We present observations of 86 post-Asymptotic Giant Branch (post-AGB) stars of OH maser transitions, taken with the Parkes Telescope between September 2002 and August 2003. Post-AGB stars are the precursors of planetary nebulae, which have a wide range of morphologies that are not well explained. By studying the circumstellar envelopes of post-AGB stars through the masers produced in them, we hope to shed light on the origin of planetary nebula morphologies.

  14. The Impulsive Heating Rate in Shocked O Star Winds

    E-Print Network [OSTI]

    Cohen, David

    The Impulsive Heating Rate in Shocked O Star Winds: Determined Directly from High-Resolution X; no corona #12;Radiation-driven O star winds Pup (O4 supergiant): M ~ few 10-6 Msun/yr UV spectrum: C IV with the stellar wind #12;Radiation-driven O star winds kinetic power in the wind = 1/2 Mv 2 (~10-3 Lbol) typically

  15. Star cell type core configuration for structural sandwich materials

    DOE Patents [OSTI]

    Christensen, R.M.

    1995-08-01

    A new pattern for cellular core material used in sandwich type structural materials is disclosed. The new pattern involves star shaped cells intermixed with hexagonal shaped cells. The new patterned cellular core material includes star shaped cells interconnected at points thereof and having hexagonal shape cells positioned adjacent the star points. The new pattern allows more flexibility and can conform more easily to curved shapes. 3 figs.

  16. OXYGEN ISOTOPIC RATIOS IN COOL R CORONAE BOREALIS STARS

    SciTech Connect (OSTI)

    Garcia-Hernandez, D. A. [Instituto de Astrofisica de Canarias (IAC), C/Via Lactea s/n, 38200 La Laguna, Tenerife (Spain); Lambert, David L. [W. J. McDonald Observatory, University of Texas at Austin. 1 University Station, C1400. Austin, TX 78712-0259 (United States); Rao, N. Kameswara [Indian Institute of Astrophysics, Bangalore 560 034 (India); Hinkle, Ken H. [National Optical Astronomy Observatory (NOAO), Tucson, AZ 85726 (United States); Eriksson, Kjell, E-mail: agarcia@iac.e, E-mail: dll@astro.as.utexas.ed, E-mail: nkrao@iiap.res.i, E-mail: hinkle@noao.ed, E-mail: Kjell.Eriksson@astro.uu.s [Department of Physics and Astronomy, Uppsala University, Box 515, 75120 Uppsala (Sweden)

    2010-05-01

    We investigate the relationship between R Coronae Borealis (RCB) stars and hydrogen-deficient carbon (HdC) stars by measuring precise {sup 16}O/{sup 18}O ratios for five cool RCB stars. The {sup 16}O/{sup 18}O ratios are derived by spectrum synthesis from high-resolution (R {approx} 50, 000) K-band spectra. Lower limits to the {sup 16}O/{sup 17}O and {sup 14}N/{sup 15}N ratios as well as Na and S abundances (when possible) are also given. RCB stars in our sample generally display less {sup 18}O than HdC stars-the derived {sup 16}O/{sup 18}O ratios range from 3 to 20. The only exception is the RCB star WX CrA, which seems to be an HdC-like star with {sup 16}O/{sup 18}O = 0.3. Our result of a higher {sup 16}O/{sup 18}O ratio for the RCB stars must be accounted for by a theory of the formation and evolution of HdC and RCB stars. We speculate that a late dredge-up of products of He burning, principally {sup 12}C and {sup 16}O, may convert an {sup 18}O-rich HdC star into an {sup 18}O-poor RCB star as the H-deficient star begins its final evolution from a cool supergiant to the top of the white dwarf cooling track.

  17. Stability of thin-shell interfaces inside compact stars

    E-Print Network [OSTI]

    Jonas P. Pereira; Jaziel G. Coelho; Jorge A. Rueda

    2015-01-05

    We use the thin-shell Darmois-Israel formalism to model and assess the stability of the interfaces separating phases, e.g. the core and the crust, within compact stars. We exemplify the relevance and non-triviality of this treatment in the simplest case of an incompressible star, in constant pressure phase transitions, and in the case of strange quark stars with crust.

  18. IDENTIFICATION OF MAIN-SEQUENCE STARS WITH MID-INFRARED EXCESSES USING GLIMPSE: PICTORIS ANALOGS?

    E-Print Network [OSTI]

    Clemens, Dan

    IDENTIFICATION OF MAIN-SEQUENCE STARS WITH MID-INFRARED EXCESSES USING GLIMPSE: #12; PICTORIS stars, 29 appear to be main-sequence stars on the basis of optical spectral classifications. Five of the 29 main-sequence stars are O or B stars with excesses that can be plausibly explained by thermal

  19. Discrete Cosmological Self-Similarity And Delta Scuti Stars

    E-Print Network [OSTI]

    R. L. Oldershaw

    2008-10-08

    Within the context of a fractal paradigm that emphasizes nature's well-stratified hierarchical organization, the delta Scuti class of variable stars is investigated for evidence of discrete cosmological self-similarity. Methods that were successfully applied to the RR Lyrae class of variable stars are used to identify Atomic Scale analogues to delta Scuti stars and their relevant range of energy levels. The mass, pulsation mode and fundamental oscillation period of a well-studied delta Scuti star are shown to be quantitatively self-similar to the counterpart parameters of a uniquely identified Atomic Scale analogue. Several additional tests confirm the specificity of the discrete fractal relationship.

  20. The Federal Guiding Principles Checklist in ENERGY STAR Portfolio

    Broader source: Energy.gov [DOE]

    This webcast will teach Federal energy and sustainability professionals how to use the ENERGY STAR measurement and tracking tool, Portfolio Manager, to help ensure compliance with the Guiding...

  1. NEW YOUNG STAR CANDIDATES IN CG4 AND Sa101

    SciTech Connect (OSTI)

    Rebull, L. M.; Laine, S.; Laher, R.; Legassie, M.; Hoette, V.; Kim, J. S.; Foster, M.; Mallory, C. R.; McCarron, K.; Sherry, W. H.

    2011-07-15

    The CG4 and Sa101 regions together cover a region of {approx}0.5 deg{sup 2} in the vicinity of a 'cometary globule' that is part of the Gum Nebula. There are seven previously identified young stars in this region; we have searched for new young stars using mid- and far-infrared data (3.6-70 {mu}m) from the Spitzer Space Telescope, combined with ground-based optical data and near-infrared data from the Two Micron All Sky Survey. We find infrared excesses in all six of the previously identified young stars in our maps and identify 16 more candidate young stars based on apparent infrared excesses. Most (73%) of the new young stars are Class II objects. There is a tighter grouping of young stars and young star candidates in the Sa101 region, in contrast to the CG4 region, where there are fewer young stars and young star candidates, and they are more dispersed. Few likely young objects are found in the 'fingers' of the dust being disturbed by the ionization front from the heart of the Gum Nebula.

  2. Scattering from Star Polymers including Excluded Volume Effects

    SciTech Connect (OSTI)

    Li, Xin [ORNL; Do, Changwoo [ORNL; Liu, Yun [National Institute of Standards and Technology (NIST); Sanchez-Diaz, Luis E [ORNL; Hong, Kunlun [ORNL; Smith, Greg [ORNL; Chen, Wei-Ren [ORNL

    2014-01-01

    In this work we present a new model for the form factor of a star polymer consisting of self-avoiding branches. This new model incorporates excluded volume effects and is derived from the two point correlation function for a star polymer.. We compare this model to small angle neutron scattering (SANS) measurements from polystyrene (PS) stars immersed in a good solvent, tetrahydrofuran (THF). It is shown that this model provides a good description of the scattering signature originating from the excluded volume effect and it explicitly elucidates the connection between the global conformation of a star polymer and the local stiffness of its constituent branch.

  3. Buying an Appliance this Holiday Season? ENERGY STAR Products...

    Broader source: Energy.gov (indexed) [DOE]

    When shopping for appliances or electronics for the holidays, look for the ENERGY STAR and EnergyGuide labels. | Photo by Dennis Schroeder, NREL 22090. When shopping for...

  4. Calendar Year 2009 Program Benefits for ENERGY STAR Labeled Products

    E-Print Network [OSTI]

    Homan, Gregory K

    2011-01-01

    of regional, national and international energy programsEnergy Commission Public Interest Research Program (PIER) by Lawrence Berkeley NationalEnergy Star Office Equipment Program. Lawrence Berkeley National

  5. Calendar Year 2008 Program Benefits for ENERGY STAR Labeled Products

    E-Print Network [OSTI]

    Homan, GregoryK

    2010-01-01

    of regional, national and international energy programsEnergy Commission Public Interest Research Program (PIER) by Lawrence Berkeley NationalEnergy Star Office Equipment Program. Lawrence Berkeley National

  6. Pair Winds in Schwarzschild Spacetime with Application to Strange Stars

    E-Print Network [OSTI]

    A. G. Aksenov; M. Milgrom; V. V. Usov

    2007-01-09

    We present the results of numerical simulations of stationary, spherically outflowing, electron-positron pair winds, with total luminosities in the range 10^{34}--10^{42} ergs/s. In the concrete example described here, the wind injection source is a hot, bare, strange star, predicted to be a powerful source of pairs created by the Coulomb barrier at the quark surface. We find that photons dominate in the emerging emission, and the emerging photon spectrum is rather hard and differs substantially from the thermal spectrum expected from a neutron star with the same luminosity. This might help distinguish the putative bare strange stars from neutron stars.

  7. Department of Energy Honors 50 ENERGY STAR® Partners that Saved...

    Energy Savers [EERE]

    security." ENERGY STAR began in 1992 as a voluntary, market-based partnership to reduce air pollution through increased energy efficiency. Today, DOE, in partnership with EPA,...

  8. Evaluation Prompts ENERGY STAR Program to Replace Web Tool, Saving...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Value of Program Evaluation Evaluation Prompts ENERGY STAR Program to Replace Web Tool, Saving 90 Percent of Annual Costs A program within the U.S. Environmental...

  9. STAR-CD es-aftertreatment | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    with STAR-CD using Transient Flemelet Models: TIF and TPV Development of Artificial Ash Accelerated Accumulation Test Diesel Particulate Filters: Market Introducution in...

  10. Energy All-Stars Shine Bright at Inaugural Lecture Series

    Broader source: Energy.gov [DOE]

    Last Saturday, the Energy Department held its first Energy All-Stars event -- an afternoon of TED-style talks from America's energy leaders.

  11. STAR Images: Image gallery from the Solenoidal Tracker at RHIC

    DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

    The primary physics task of STAR is to study the formation and characteristics of the quark-gluon plasma (QGP), a state of matter believed to exist at sufficiently high energy densities. STAR consists of several types of detectors, each specializing in detecting certain types of particles or characterizing their motion. These detectors allow final statements to be made about the collision. The gallery of STAR images makes available a small collection of event-generated images from Gold-Beam experiments, a simulation of TCP Drift, and a library of STAR instrument and construction photos.

  12. Carbon and Strontium Abundances of Metal-Poor Stars

    E-Print Network [OSTI]

    David K. Lai; Jennifer A. Johnson; Michael Bolte; Sara Lucatello

    2007-06-20

    We present carbon and strontium abundances for 100 metal-poor stars measured from R$\\sim $7000 spectra obtained with the Echellette Spectrograph and Imager at the Keck Observatory. Using spectral synthesis of the G-band region, we have derived carbon abundances for stars ranging from [Fe/H]$=-1.3$ to [Fe/H]$=-3.8$. The formal errors are $\\sim 0.2$ dex in [C/Fe]. The strontium abundance in these stars was measured using spectral synthesis of the resonance line at 4215 {\\AA}. Using these two abundance measurments along with the barium abundances from our previous study of these stars, we show it is possible to identify neutron-capture-rich stars with our spectra. We find, as in other studies, a large scatter in [C/Fe] below [Fe/H]$ = -2$. Of the stars with [Fe/H]$carbon-rich metal-poor stars. The Sr and Ba abundances show that three of the carbon-rich stars are neutron-capture-rich, while two have normal Ba and Sr. This fraction of carbon enhanced stars is consistent with other studies that include this metallicity range.

  13. X-ray Emission from Isolated Be Stars

    E-Print Network [OSTI]

    David H. Cohen

    2000-08-22

    I discuss the X-ray observations of Be stars, and how their properties compare to non-emission B stars. I focus on several specific stars that show high flux levels and variability but also report on several interesting survey results. The Be X-ray properties are discussed in the context of wind-shock X-ray emission from normal OB stars as well as in the context of general mechanisms that have been proposed to explain the Be phenomenon. Finally, I conclude with a discussion of the spectral diagnostics that will be available from the new generation of X-ray telescopes.

  14. Home Performance with ENERGY STAR Program Winners Are Committed...

    Broader source: Energy.gov (indexed) [DOE]

    in 33 states at the 2015 ENERGY STAR Partner of the Year Awards for their commitment to saving energy and protecting the environment through superior energy efficiency...

  15. ENERGY STAR Webinar: Energy Savings Plus Health: Indoor Air Quality...

    Office of Environmental Management (EM)

    Energy Savings Plus Health: Indoor Air Quality Guidelines for School Building Upgrades ENERGY STAR Webinar: Energy Savings Plus Health: Indoor Air Quality Guidelines for School...

  16. Nuclear Theory Helps Forecast Neutron Star Temperatures | U.S...

    Office of Science (SC) Website

    Nuclear Theory Helps Forecast Neutron Star Temperatures Nuclear Physics (NP) NP Home About Research Facilities Science Highlights Benefits of NP Funding Opportunities Nuclear...

  17. Gas flows, star formation and galaxy evolution

    E-Print Network [OSTI]

    John E. Beckman; Emilio Casuso; Almudena Zurita; Monica Relaño

    2004-05-31

    In the first part of this article we show how observations of the chemical evolution of the Galaxy: G- and K-dwarf numbers as functions of metallicity, and abundances of the light elements, D, Li, Be and B, in both stars and the interstellar medium (ISM), lead to the conclusion that metal poor HI gas has been accreting to the Galactic disc during the whole of its lifetime, and is accreting today at a measurable rate, ~2 Msun per year across the full disc. Estimates of the local star formation rate (SFR) using methods based on stellar activity, support this picture. The best fits to all these data are for models where the accretion rate is constant, or slowly rising with epoch. We explain here how this conclusion, for a galaxy in a small bound group, is not in conflict with graphs such as the Madau plot, which show that the universal SFR has declined steadily from z=1 to the present day. We also show that a model in which disc galaxies in general evolve by accreting major clouds of low metallicity gas from their surroundings can explain many observations, notably that the SFR for whole galaxies tends to show obvious variability, and fractionally more for early than for late types, and yields lower dark to baryonic matter ratios for large disc galaxies than for dwarfs. In the second part of the article we use NGC 1530 as a template object, showing from Fabry-Perot observations of its Halpha emission how strong shear in this strongly barred galaxy acts to inhibit star formation, while compression acts to stimulate it.

  18. Energy Star Appliances 1 Texas A&M AgriLife Extension Service ENERGY STAR Appliances

    E-Print Network [OSTI]

    Energy Star® Appliances 1 Texas A&M AgriLife Extension Service ENERGY STAR® Appliances ENERGY STAR®-labeled appliances save you money by using less electricity and water than other appliances. Better appliance energy efficiency comes from quality materials and technologically advanced materials. Although energy efficient

  19. Helium enhancements in globular cluster stars from Asymptotic Giant Branch star pollution

    E-Print Network [OSTI]

    Amanda Karakas; Yeshe Fenner; Alison Sills; Simon Campbell; John Lattanzio

    2006-05-21

    Using a chemical evolution model we investigate the intriguing suggestion that there are populations of stars in some globular clusters (e.g. NGC 2808, omega Centauri) with enhanced levels of helium (Y from about 0.28 to 0.40) compared to the majority of the population that presumably have a primordial helium abundance. We assume that a previous generation of massive low-metallicity Asymptotic Giant Branch (AGB) stars has polluted the cluster gas via a slow stellar wind. We use two independent sets of AGB yields computed from detailed models to follow the evolution of helium, carbon, nitrogen and oxygen in the cluster gas using a Salpeter initial mass function (IMF) and a number of top-heavy IMFs. In no case were we able to fit the observational constraints, Y > 0.30 and C+N+O approximately constant. Depending on the shape of the IMF and the yields, we either obtained Y approximately greater than 0.30 and large increases in C+N+O or Y < 0.30 and C+N+O approximately constant. These results suggest that either AGB stars alone are not responsible for the large helium enrichment or that any dredge-up from this generation of stars was less than predicted by standard models.

  20. LoanSTAR Database Overview, A LoanSTAR Deliverable Report 

    E-Print Network [OSTI]

    Sweeney, J., Jr.

    2003-01-01

    The data in this database is the LoanSTAR segment of the building energy information data system at the Texas A&M University's Energy Systems Lab. This portion of the data system has been exported to the afore-mentioned computer system in a my...

  1. Passive load follow analysis of the STAR-LM and STAR-H2 systems. 

    E-Print Network [OSTI]

    Moisseytsev, Anton

    2004-09-30

    cooled reactor on natural circulation and the supercritical carbon dioxide Brayton cycle. The STAR-H2 system uses the same reactor which is coupled to the hydrogen production plant, the Brayton cycle, and the water desalination plant. The Brayton cycle...

  2. Population III Stars in I Zw 18

    E-Print Network [OSTI]

    Heap, Sally; Hubeny, Ivan

    2015-01-01

    Ultraviolet and 21-cm observations suggest that the extremely low-metallicity galaxy, I Zw 18, is a stream-fed galaxy containing a "pocket" of pristine stars responsible for producing nebular He II recombination emission observed in I Zw18-NW. Far-UV spectra by Hubble/COS and the Far Ultraviolet Spectroscopic Explorer (FUSE) make this suggestion conclusive by demonstrating that the spectrum of I Zw 18-NW shows no metal lines like O VI 1032, 1038 of comparable ionization as the He II recombination emission.

  3. High-Precision Spectroscopy of Pulsating Stars

    E-Print Network [OSTI]

    Aerts, C; Desmet, M; Carrier, F; Zima, W; Briquet, M; De Ridder, J

    2007-01-01

    We review methodologies currently available to interprete time series of high-resolution high-S/N spectroscopic data of pulsating stars in terms of the kind of (non-radial) modes that are excited. We illustrate the drastic improvement of the detection treshold of line-profile variability thanks to the advancement of the instrumentation over the past two decades. This has led to the opportunity to interprete line-profile variations with amplitudes of order m/s, which is a factor 1000 lower than the earliest line-profile time series studies allowed for.

  4. High-Precision Spectroscopy of Pulsating Stars

    E-Print Network [OSTI]

    C. Aerts; S. Hekker; M. Desmet; F. Carrier; W. Zima; M. Briquet; J. De Ridder

    2007-01-16

    We review methodologies currently available to interprete time series of high-resolution high-S/N spectroscopic data of pulsating stars in terms of the kind of (non-radial) modes that are excited. We illustrate the drastic improvement of the detection treshold of line-profile variability thanks to the advancement of the instrumentation over the past two decades. This has led to the opportunity to interprete line-profile variations with amplitudes of order m/s, which is a factor 1000 lower than the earliest line-profile time series studies allowed for.

  5. Gravitomagnetism in superconductors and compact stars

    E-Print Network [OSTI]

    Cosimo Bambi

    2007-10-10

    There are three experimentally observed effects in rotating superconductors that are so far unexplained. Some authors have tried to interpret such a phenomena as possible new gravitational properties of coherent quantum systems: in particular, they suggest that the gravitomagnetic field of that kind of matter may be many orders of magnitude stronger than the one expected in the standard theory. Here I show that this interpretation would be in conflict with the common belief that neutron stars have neutrons in superfluid state and protons in superconductive one.

  6. Sound velocity bound and neutron stars

    E-Print Network [OSTI]

    Paulo F. Bedaque; Andrew W. Steiner

    2015-01-25

    It has been conjectured that the velocity of sound in any medium is smaller than the velocity of light in vacuum divided by $\\sqrt{3}$. Simple arguments support this bound in non-relativistic and/or weakly coupled theories. The bound has been demonstrated in several classes of strongly coupled theories with gravity duals and is saturated only in conformal theories. We point out that the existence of neutron stars with masses around two solar masses combined with the knowledge of the equation of state of hadronic matter at "low" densities is in strong tension with this bound.

  7. Photon emission from bare quark stars

    E-Print Network [OSTI]

    B. G. Zakharov

    2010-08-16

    We investigate the photon emission from the electrosphere of a quark star. It is shown that at temperatures T\\sim 0.1-1 MeV the dominating mechanism is the bremsstrahlung due to bending of electron trajectories in the mean Coulomb field of the electrosphere. The radiated energy for this mechanism is much larger than that for the Bethe-Heitler bremsstrahlung. The energy flux from the mean field bremsstrahlung exceeds the one from the tunnel e^{+}e^{-} pair creation as well. We demonstrate that the LPM suppression of the photon emission is negligible.

  8. Colored condensates deep inside neutron stars

    E-Print Network [OSTI]

    David Blaschke

    2014-07-28

    It is demonstrated how in the absence of solutions for QCD under conditions deep inside compact stars an equation of state can be obtained within a model that is built on the basic symmetries of the QCD Lagrangian, in particular chiral symmetry and color symmetry. While in the vacuum the chiral symmetry is spontaneously broken, it gets restored at high densities. Color symmetry, however, gets broken simultaneously by the formation of colorful diquark condensates. It is shown that a strong diquark condensate in cold dense quark matter is essential for supporting the possibility that such states could exist in the recently observed pulsars with masses of 2 $M_\\odot$.

  9. Nucleosynthesis in intermediate mass AGB stars

    E-Print Network [OSTI]

    John Lattanzio; Corinne Charbonnel; Manuel Forestini

    1999-12-15

    We present a summary of the main sites for nucleosynthesis in intermediate mass Asymptotic Giant Branch (AGB) stars. We then discuss some detailed evolutionary models and how these have been used to create a synthetic evolution code which calculates the nucleosynthesis very rapidly, enabling us to investigate changes in some uncertain parameters in AGB evolution, such as mass-loss and dredge-up. We then present results for C, C/O, Mg and Al. We also discuss the changes due to the recent NACRE compilation of reaction rates.

  10. On-brane data for braneworld stars

    E-Print Network [OSTI]

    Matt Visser; David L. Wiltshire

    2003-02-20

    Stellar structure in braneworlds is markedly different from that in ordinary general relativity. As an indispensable first step towards a more general analysis, we completely solve the ``on brane'' 4-dimensional Gauss and Codazzi equations for an arbitrary static spherically symmetric star in a Randall--Sundrum type II braneworld. We then indicate how this on-brane boundary data should be propagated into the bulk in order to determine the full 5-dimensional spacetime geometry. Finally, we demonstrate how this procedure can be generalized to solid objects such as planets.

  11. The Gaia Mission, Binary Stars and Exoplanets

    E-Print Network [OSTI]

    Eyer, Laurent; Holl, Berry; North, Pierre; Zucker, Shay; Evans, Dafydd W; Pourbaix, Dimitri; Hodgkin, Simon T; Thuillot, William; Mowlavi, Nami; Carry, Benoit

    2015-01-01

    On the 19th of December 2013, the Gaia spacecraft was successfully launched by a Soyuz rocket from French Guiana and started its amazing journey to map and characterise one billion celestial objects with its one billion pixel camera. In this presentation, we briefly review the general aims of the mission and describe what has happened since launch, including the Ecliptic Pole scanning mode. We also focus especially on binary stars, starting with some basic observational aspects, and then turning to the remarkable harvest that Gaia is expected to yield for these objects.

  12. Green's Functions for Translation Invariant Star Products

    E-Print Network [OSTI]

    Lizzi, Fedele; Vitale, Patrizia

    2015-01-01

    We calculate the Green functions for a scalar field theory with quartic interactions for which the fields are multiplied with a generic translation invariant star product. Our analysis involves both noncommutative products, for which there is the canonical commutation relation among coordinates, and nonlocal commutative products. We give explicit expressions for the one-loop corrections to the two and four point functions. We find that the phenomenon of ultraviolet/infrared mixing is always a consequence of the presence of noncommuting variables. The commutative part of the product does not have the mixing.

  13. Green's Functions for Translation Invariant Star Products

    E-Print Network [OSTI]

    Fedele Lizzi; Manolo Rivera; Patrizia Vitale

    2015-08-11

    We calculate the Green functions for a scalar field theory with quartic interactions for which the fields are multiplied with a generic translation invariant star product. Our analysis involves both noncommutative products, for which there is the canonical commutation relation among coordinates, and nonlocal commutative products. We give explicit expressions for the one-loop corrections to the two and four point functions. We find that the phenomenon of ultraviolet/infrared mixing is always a consequence of the presence of noncommuting variables. The commutative part of the product does not have the mixing.

  14. All-Star Nanocrystals | The Ames Laboratory

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 OutreachProductswsicloudwsiclouddenDVA N C E D B L O O D S TA I N P A T TSorbents forCOAll NewsSTEMEnergyAll-Star

  15. Five Star Technologies | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QAsource History View New PagesSustainable Urban Transport Jump to: navigation,FirstGeoThermtheForks, SouthStar

  16. StarSolar Corporation | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page| Open Energy Information Serbia-Enhancing CapacityVectren) Jump to:SpillDavid,EnergybyBiomass Jump to:SystemsStarSolar

  17. MagStar Technologies | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QAsource History View NewTexas:Montezuma,Information MHKMHK5 <Kentucky:York: Energy Resources JumpMagStar

  18. ARM - Campaign Instrument - 4star-air

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefieldSulfateSciTechtail.TheoryTuesday, August 10, 20102016StudyCHAPS: CampaigngovInstruments4star-air

  19. Alliance Star Energy LLC | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIX E LISTStar Energy LLC Jump to: navigation, search Name: Alliance Star Energy LLC Place:

  20. Star Power | Princeton Plasma Physics Lab

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantityBonneville Power AdministrationRobust,Field-effect Photovoltaics -7541C.3X-rays Illuminate aStructural BasisResidual energyStar

  1. Silver Star Wind Farm | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION JEnvironmental Jump to:EA EIS ReportEurope GmbH Jump to: navigation,ShowSikesSilvan PowerJumpStar

  2. CalStar Products | Open Energy Information

    Open Energy Info (EERE)

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIX ECoopButte County, California: Energy ResourcesCRED: A New Model(Redirected fromCalStar

  3. Could the Ultra Metal-poor Stars be Chemically Peculiar and Not Related to the First Stars?

    E-Print Network [OSTI]

    K. A. Venn; D. L. Lambert

    2008-01-04

    Chemically peculiar stars define a class of stars that show unusual elemental abundances due to stellar photospheric effects and not due to natal variations. In this paper, we compare the elemental abundance patterns of the ultra metal-poor stars with metallicities [Fe/H] $\\sim -5 $ to those of a subclass of chemically peculiar stars. These include post-AGB stars, RV Tauri variable stars, and the Lambda Bootis stars, which range in mass, age, binarity, and evolutionary status, yet can have iron abundance determinations as low as [Fe/H] $\\sim -5$. These chemical peculiarities are interpreted as due to the separation of gas and dust beyond the stellar surface, followed by the accretion of dust depleted-gas. Contrary to this, the elemental abundances in the ultra metal-poor stars are thought to represent yields of the most metal-poor supernova and, therefore, observationally constrain the earliest stages of chemical evolution in the Universe. The abundance of the elements in the photospheres of the ultra metal-poor stars appear to be related to the condensation temperature of that element; if so, then their CNO abundances suggest true metallicities of [X/H]~ -2 to -4, rather than their present metallicities of [Fe/H] < -5.

  4. On the nature of WO stars: a quantitative analysis of the WO3 star DR1 in IC 1613

    E-Print Network [OSTI]

    Tramper, F; Hartoog, O E; Sana, H; de Koter, A; Vink, J S; Ellerbroek, L E; Langer, N; Garcia, M; Kaper, L; de Mink, S E

    2013-01-01

    Context. Oxygen sequence Wolf-Rayet (WO) stars are thought to represent the final evolutionary stage of the most massive stars. The characteristic strong O vi emission possibly originates from an enhanced oxygen abundance in the stellar wind. Alternatively, the O vi emission can be caused by the high temperature of these stars, in which case the WO stars are the high-temperature extension of the more common carbon sequence Wolf-Rayet (WC) stars. Aims. By constraining the physical properties and evolutionary status of DR1, a WO star in the low-metallicity Local Group dwarf galaxy IC 1613 and one of only two objects of its class known in a SMC-like metallicity environment, we aim to investigate the nature of WO stars and their evolutionary connection with WC stars. Methods. We use the non-LTE atmosphere code cmfgen to model the observed spectrum of DR1 and to derive its stellar and wind parameters. We compare our values with other studies of WC and WO stars, as well as with the predictions of evolutionary model...

  5. Too massive neutron stars: The role of dark matter?

    E-Print Network [OSTI]

    Ang Li; Feng Huang; Ren-Xin Xu

    2012-08-18

    The maximum mass of a neutron star is generally determined by the equation of state of the star material. In this study, we take into account dark matter particles, assumed to behave like fermions with a free parameter to account for the interaction strength among the particles, as a possible constituent of neutron stars. We find dark matter inside the star would soften the equation of state more strongly than that of hyperons, and reduce largely the maximum mass of the star. However, the neutron star maximum mass is sensitive to the particle mass of dark matter, and a very high neutron star mass larger than 2 times solar mass could be achieved when the particle mass is small enough. Such kind of dark-matter- admixed neutron stars could explain the recent measurement of the Shapiro delay in the radio pulsar PSR J1614-2230, which yielded a neutron star mass of 2 times solar mass that may be hardly reached when hyperons are considered only, as in the case of the microscopic Brueckner theory. Furthermore, in this particular case, we point out that the dark matter around a neutron star should also contribute to the mass measurement due to its pure gravitational effect. However, our numerically calculation illustrates that such contribution could be safely ignored because of the usual diluted dark matter environment assumed. We conclude that a very high mass measurement of about 2 times solar mass requires a really stiff equation of state in neutron stars, and find a strong upper limit (<= 0.64 GeV) for the particle mass of non-self- annihilating dark matter based on the present model.

  6. The best and brightest metal-poor stars

    SciTech Connect (OSTI)

    Schlaufman, Kevin C.; Casey, Andrew R., E-mail: kschlauf@mit.edu, E-mail: arc@ast.cam.ac.uk [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2014-12-10

    The chemical abundances of large samples of extremely metal-poor (EMP) stars can be used to investigate metal-free stellar populations, supernovae, and nucleosynthesis as well as the formation and galactic chemical evolution of the Milky Way and its progenitor halos. However, current progress on the study of EMP stars is being limited by their faint apparent magnitudes. The acquisition of high signal-to-noise spectra for faint EMP stars requires a major telescope time commitment, making the construction of large samples of EMP star abundances prohibitively expensive. We have developed a new, efficient selection that uses only public, all-sky APASS optical, 2MASS near-infrared, and WISE mid-infrared photometry to identify bright metal-poor star candidates through their lack of molecular absorption near 4.6 microns. We have used our selection to identify 11,916 metal-poor star candidates with V < 14, increasing the number of publicly available candidates by more than a factor of five in this magnitude range. Their bright apparent magnitudes have greatly eased high-resolution follow-up observations that have identified seven previously unknown stars with [Fe/H] ? –3.0. Our follow-up campaign has revealed that 3.8{sub ?1.1}{sup +1.3}% of our candidates have [Fe/H] ? –3.0 and 32.5{sub ?2.9}{sup +3.0}% have –3.0 ? [Fe/H] ? –2.0. The bulge is the most likely location of any existing Galactic Population III stars, and an infrared-only variant of our selection is well suited to the identification of metal-poor stars in the bulge. Indeed, two of our confirmed metal-poor stars with [Fe/H] ? –2.7 are within about 2 kpc of the Galactic center. They are among the most metal-poor stars known in the bulge.

  7. Gravitational lensing in eclipsing binary stars

    E-Print Network [OSTI]

    T. R. Marsh

    2000-12-18

    I consider the effect of the gravitational deflection of light upon the light curves of eclipsing binary stars, focussing mainly upon systems containing at least one white dwarf component. In absolute terms the effects are small, however they are strongest at the time of secondary eclipse when the white dwarf transits its companion, and act to reduce the depth of this feature. If not accounted for, this may lead to under-estimation of the radius of the white dwarf compared to that of its companion. I show that the effect is significant for plausible binary parameters, and that it leads to ~25% reduction in the transit depth in the system KPD 1930+2752. The reduction of eclipse depth is degenerate with the stellar radius ratio, and therefore cannot be used to establish the existence of lensing. A second order effect of the light bending is to steepen the ingress and egress features of the secondary eclipse relative to the primary eclipse, although it will be difficult to see this in practice. I consider also binaries containing neutron stars and black-holes. I conclude that, although relatively large effects are possible in such systems, a combination of rarity, faintness and intrinsic variability make it unlikely that lensing will be detectable in them.

  8. Star formation and substructure in galaxy clusters

    SciTech Connect (OSTI)

    Cohen, Seth A.; Hickox, Ryan C.; Wegner, Gary A.; Einasto, Maret; Vennik, Jaan

    2014-03-10

    We investigate the relationship between star formation (SF) and substructure in a sample of 107 nearby galaxy clusters using data from the Sloan Digital Sky Survey. Several past studies of individual galaxy clusters have suggested that cluster mergers enhance cluster SF, while others find no such relationship. The SF fraction in multi-component clusters (0.228 ± 0.007) is higher than that in single-component clusters (0.175 ± 0.016) for galaxies with M{sub r}{sup 0.1}star-forming galaxies increases with clustercentric distance and decreases with local galaxy number density, and multi-component clusters show a higher SF fraction than single-component clusters at almost all clustercentric distances and local densities. Comparing the SF fraction in individual clusters to several statistical measures of substructure, we find weak, but in most cases significant at greater than 2?, correlations between substructure and SF fraction. These results could indicate that cluster mergers may cause weak but significant SF enhancement in clusters, or unrelaxed clusters exhibit slightly stronger SF due to their less evolved states relative to relaxed clusters.

  9. Evolution of star clusters on eccentric orbits

    E-Print Network [OSTI]

    Cai, Maxwell Xu; Heggie, Douglas C; Varri, Anna Lisa

    2015-01-01

    We study the evolution of star clusters on circular and eccentric orbits using direct $N$-body simulations. We model clusters with initially $N=8{\\rm k}$ and $N=16{\\rm k}$ single stars of the same mass, orbiting around a point-mass galaxy. For each orbital eccentricity that we consider, we find the apogalactic radius at which the cluster has the same lifetime as the cluster with the same $N$ on a circular orbit. We show that then, the evolution of bound particle number and half-mass radius is approximately independent of eccentricity. Secondly, when we scale our results to orbits with the same semi-major axis, we find that the lifetimes are, to first order, independent of eccentricity. When the results of Baumgardt and Makino for a singular isothermal halo are scaled in the same way, the lifetime is again independent of eccentricity to first order, suggesting that this result is independent of the Galactic mass profile. From both sets of simulations we empirically derive the higher order dependence of the lif...

  10. THE DYNAMICS OF STAR STREAM GAPS

    SciTech Connect (OSTI)

    Carlberg, R. G., E-mail: carlberg@astro.utoronto.ca [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada)

    2013-10-01

    A massive object crossing a narrow stream of stars orbiting in the halo of the galaxy induces velocity changes both along and transverse to the stream that can lead to the development of a visible gap. For a stream narrow relative to its orbital radius, the stream crossing time is sufficiently short that the impact approximation can be used to derive the changes in angular momenta and radial actions along the star stream. The epicyclic approximation is used to calculate the evolution of the density of the stream as it orbits around in a galactic potential. Analytic expressions are available for a point mass, however, the general expressions are easily numerically evaluated for perturbing objects with arbitrary density profiles. With a simple allowance for the velocity dispersion of the stream, moderately warm streams can be modeled. The predicted evolution agrees well with the outcomes of simulations of stellar streams for streams with widths up to 1% of the orbital radius of the stream. The angular momentum distribution within the stream shears out gaps with time, further reducing the visibility of streams, although the size of the shear effect requires more detailed simulations that account for the creation of the stream. An illustrative model indicates that shear will set a lower limit of a few times the stream width for the length of gaps that persist. In general, the equations are useful for dynamical insights into the development of stream gaps and their measurement.

  11. Mutual Friction in Superfluid Neutron Stars

    E-Print Network [OSTI]

    N. Andersson; T. Sidery; G. L. Comer

    2005-10-03

    We discuss vortex-mediated mutual friction in the two-fluid model for superfluid neutron star cores. Our discussion is based on the general formalism developed by Carter and collaborators, which makes due distinction between transport velocity and momentum for each fluid. This is essential for an implementation of the so-called entrainment effect, whereby the flow of one fluid imparts momentum in the other and vice versa. The mutual friction follows by balancing the Magnus force that acts on the quantised neutron vortices with a resistive force due to the scattering of electrons off of the magnetic field with which each vortex core is endowed. We derive the form of the macroscopic mutual friction force which is relevant for a model based on smooth-averaging over a collection of vortices. We discuss the coefficients that enter the expression for this force, and the timescale on which the two interpenetrating fluids in a neutron star core are coupled. This discussion confirms that our new formulation accords well with previous work in this area.

  12. Spin paramagnetic deformation of a neutron star

    E-Print Network [OSTI]

    Suvorov, A G; Melatos, A

    2015-01-01

    Quantum mechanical corrections to the hydromagnetic force balance equation, derived from the microscopic Schr\\"{o}dinger-Pauli theory of quantum plasmas, modify the equilibrium structure and hence the mass quadrupole moment of a neutron star. It is shown here that the dominant effect --- spin paramagnetism --- is most significant in a magnetar, where one typically has $\\mu_{B}|\\boldsymbol{B}|\\gtrsim k_B T_e$, where $\\mu_{B}$ is the Bohr magneton, $\\boldsymbol{B}$ is the magnetic field, and $T_e$ is the electron temperature. The spin paramagnetic deformation of a nonbarotropic magnetar with a linked poloidal-toroidal magnetic field is calculated to be up to ${{\\sim 10}}$ times greater than the deformation caused solely by the Lorentz force. It depends on the degree of Pauli blocking by conduction electrons and the propensity to form magnetic domains, processes which are incompletely modelled at magnetar field strengths. The star becomes more oblate, as the toroidal field component strengthens. The result impli...

  13. Radial velocities of southern visual multiple stars

    SciTech Connect (OSTI)

    Tokovinin, Andrei; Pribulla, Theodor; Fischer, Debra E-mail: pribulla@ta3.sk

    2015-01-01

    High-resolution spectra of visual multiple stars were taken in 2008–2009 to detect or confirm spectroscopic subsystems and to determine their orbits. Radial velocities of 93 late-type stars belonging to visual multiple systems were measured by numerical cross-correlation. We provide the individual velocities, the width, and the amplitude of the Gaussians that approximate the correlations. The new information on the multiple systems resulting from these data is discussed. We discovered double-lined binaries in HD 41742B, HD 56593C, and HD 122613AB, confirmed several other known subsystems, and constrained the existence of subsystems in some visual binaries where both components turned out to have similar velocities. The orbits of double-lined subsystems with periods of 148 and 13 days are computed for HD 104471 Aa,Ab and HD 210349 Aa,Ab, respectively. We estimate individual magnitudes and masses of the components in these triple systems and update the outer orbit of HD 104471 AB.

  14. Spectral analysis of Kepler SPB and Beta Cep candidate stars

    E-Print Network [OSTI]

    Lehmann, H; Semaan, T; Gutiérrez, J; Smalley, B; Briquet, M; Shulyak, D; Tsymbal, V; de Cat, P

    2010-01-01

    We determine the fundamental parameters of SPB and Beta Cep candidate stars observed by the Kepler satellite mission and estimate the expected types of non-radial pulsators by comparing newly obtained high-resolution spectra with synthetic spectra computed on a grid of stellar parameters assuming LTE and check for NLTE effects for the hottest stars. For comparison, we determine Teff independently from fitting the spectral energy distribution of the stars obtained from the available photometry. We determine Teff, log(g), micro-turbulent velocity, vsin(i), metallicity, and elemental abundance for 14 of the 16 candidate stars, two of the stars are spectroscopic binaries. No significant influence of NLTE effects on the results could be found. For hot stars, we find systematic deviations of the determined effective temperatures from those given in the Kepler Input Catalogue. The deviations are confirmed by the results obtained from ground-based photometry. Five stars show reduced metallicity, two stars are He-stro...

  15. Spatial Diffusion of Stars in the Inner Galactic Bulge

    E-Print Network [OSTI]

    Sungsoo S. Kim; Mark Morris

    2001-02-14

    Star formation in the inner few hundred pc of the Galactic bulge occurs in a flattened molecular layer called the central molecular zone (CMZ). Serabyn & Morris (1996) suggest that the star formation in the CMZ has been sustained for the lifetime of the Galaxy, and that the resulting agglomeration of stars formed in the CMZ has resulted in the prominent r^-2 stellar density cusp at the Galactic center having about the same physical extent as the CMZ. This "central cusp" is somewhat less flat than the CMZ; thus the population of stars formed in the CMZ appears to have diffused out to larger latitudes. We hypothesize that such vertical diffusion is driven by the scattering of stars off the giant molecular clouds (GMC) in the CMZ, and perform numerical simulations of the scattering between stars and GMCs in the presence of the non-axisymmetric background potential. The simulation results show that the time scale for an initially flattened stellar population to achieve an aspect ratio of the observed OH/IR stars in the inner bulge, 1 to 2 Gyr, agrees well with the estimated age of those OH/IR stars.

  16. grqc/9904009 Nonlinear Evolution of Rotating Relativistic Stars

    E-Print Network [OSTI]

    Kokkotas, Kostas D.

    ]. When the neutron star has cooled to #12; 2 about 10 10 K after its formation, it can be subject­amplitude oscillations, which are in excellent agreement with linear normal mode frequencies computed in the Cowling approximation. As a first application of our code, quasi­radial modes of rapidly rotating relativistic stars

  17. Massive runaway stars in the Small Magellanic Cloud

    E-Print Network [OSTI]

    Gvaramadze, V V; Kroupa, P

    2010-01-01

    Using archival Spitzer Space Telescope data, we identified for the first time a dozen runaway OB stars in the Small Magellanic Cloud (SMC) via detection of their bow shocks. The geometry of detected bow shocks allows us to infer the direction of motion of the associated stars and to determine their possible parent clusters and associations. One of the identified runaway stars, AzV 471, was already known as a high-velocity star on the basis of its high peculiar radial velocity, which is offset by ~40 km/s from the local systemic velocity. We discuss implications of our findings for the problem of the origin of field OB stars. Several of the bow shock-producing stars are found in the confines of associations suggesting that these may be "alien" stars contributing to the observed age spread in such associations. We also report the discovery of a kidney-shaped nebula attached to the early WN-type star SMC-WR3 (AzV 60a). We interpreted this nebula as an interstellar structure created owing to the interaction betwe...

  18. Spectroscopic Studies of Nearby Cool Stars: The DUNES Sample

    E-Print Network [OSTI]

    Complutense de Madrid, Universidad

    Spectroscopic Studies of Nearby Cool Stars: The DUNES Sample J. Maldonado , R. M. Martínez of our sample will be observed by DUNES, a Herschel OTKP aiming at detecting and studying cold, faint of the kinematics of the DUNES sample. Keywords: stars, fundamental parameters, kinematic, age PACS: 97.10.-q 97

  19. EU 'confident' of star power site By Jo Twist

    E-Print Network [OSTI]

    option because of its position on the war in Iraq. Star power After the International Space Station, Iter stations, and would pave the way for commercial power production. In a fusion reaction, energy is producedEU 'confident' of star power site By Jo Twist BBC News Online science staff Europe is still

  20. Hydrogen-Deficient Stars ASP Conference Series, Vol. xxx, 2008

    E-Print Network [OSTI]

    Barnstedt, Jürgen

    Hydrogen-Deficient Stars ASP Conference Series, Vol. xxx, 2008 Werner & Rauch Elemental Abundances.S.A. Abstract. The hydrogen-deficiency in extremely hot post-AGB stars of spec- tral class PG1159 is probably caused by a (very) late helium-shell flash or a AGB final thermal pulse that consumes the hydrogen