OXYGEN ISOTOPIC RATIOS IN COOL R CORONAE BOREALIS STARS

Garcia-Hernandez, D A; Lambert, David L; Rao, N Kameswara; Hinkle, Ken H; Eriksson, Kjell

doi:10.1088/0004-637X/714/1/144

Title: OXYGEN ISOTOPIC RATIOS IN COOL R CORONAE BOREALIS STARS

Full Record
Other Related Research

Abstract

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.

Authors:

Garcia-Hernandez, D A ^[1]; Lambert, David L ^[2]; Rao, N Kameswara ^[3]; Hinkle, Ken H ^[4]; Eriksson, Kjell ^[5]

Instituto de Astrofisica de Canarias (IAC), C/Via Lactea s/n, 38200 La Laguna, Tenerife (Spain)
W. J. McDonald Observatory, University of Texas at Austin. 1 University Station, C1400. Austin, TX 78712-0259 (United States)
Indian Institute of Astrophysics, Bangalore 560 034 (India)
National Optical Astronomy Observatory (NOAO), Tucson, AZ 85726 (United States)
Department of Physics and Astronomy, Uppsala University, Box 515, 75120 Uppsala (Sweden)

Publication Date:: Sat May 01 00:00:00 EDT 2010

OSTI Identifier:: 21448953

Resource Type:: Journal Article

Journal Name:: Astrophysical Journal

Additional Journal Information:: Journal Volume: 714; Journal Issue: 1; Other Information: DOI: 10.1088/0004-637X/714/1/144; Journal ID: ISSN 0004-637X

Country of Publication:: United States

Language:: English

Subject:: 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; CARBON; CARBON 12; HYDROGEN; ISOTOPE RATIO; NITROGEN 14; NITROGEN 15; OXYGEN 16; OXYGEN 17; OXYGEN 18; STAR EVOLUTION; WHITE DWARF STARS; CARBON ISOTOPES; DIMENSIONLESS NUMBERS; DWARF STARS; ELEMENTS; EVEN-EVEN NUCLEI; EVEN-ODD NUCLEI; EVOLUTION; ISOTOPES; LIGHT NUCLEI; NITROGEN ISOTOPES; NONMETALS; NUCLEI; ODD-EVEN NUCLEI; ODD-ODD NUCLEI; OXYGEN ISOTOPES; STABLE ISOTOPES; STARS

Citation Formats


                    Garcia-Hernandez, D A, Lambert, David L, Rao, N Kameswara, Hinkle, Ken H, and Eriksson, Kjell. OXYGEN ISOTOPIC RATIOS IN COOL R CORONAE BOREALIS STARS.  United States: N. p., 2010. 
        Web.  doi:10.1088/0004-637X/714/1/144.

Copy to clipboard


                    Garcia-Hernandez, D A, Lambert, David L, Rao, N Kameswara, Hinkle, Ken H, & Eriksson, Kjell. OXYGEN ISOTOPIC RATIOS IN COOL R CORONAE BOREALIS STARS.  United States.  https://doi.org/10.1088/0004-637X/714/1/144

Copy to clipboard


                    Garcia-Hernandez, D A, Lambert, David L, Rao, N Kameswara, Hinkle, Ken H, and Eriksson, Kjell. 2010.  
        "OXYGEN ISOTOPIC RATIOS IN COOL R CORONAE BOREALIS STARS".  United States.  https://doi.org/10.1088/0004-637X/714/1/144.

Copy to clipboard


                    
@article{osti_21448953,

  title        = {OXYGEN ISOTOPIC RATIOS IN COOL R CORONAE BOREALIS STARS},

  author       = {Garcia-Hernandez, D A and Lambert, David L and Rao, N Kameswara and Hinkle, Ken H and Eriksson, Kjell},

  abstractNote = {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.},

  doi          = {10.1088/0004-637X/714/1/144},

  url          = {https://www.osti.gov/biblio/21448953},
  journal      = {Astrophysical Journal},

  issn         = {0004-637X},

  number       = 1,

  volume       = 714,

  place        = {United States},

  year         = {Sat May 01 00:00:00 EDT 2010},

  month        = {Sat May 01 00:00:00 EDT 2010}

}

Copy to clipboard

Journal Article:

https://doi.org/10.1088/0004-637X/714/1/144

Other availability

Find in Google Scholar

Search WorldCat to find libraries that may hold this journal

Save / Share:

Export Metadata

Save to My Library

Similar records in OSTI.GOV collections:

CNO ABUNDANCES OF HYDROGEN-DEFICIENT CARBON AND R CORONAE BOREALIS STARS: A VIEW OF THE NUCLEOSYNTHESIS IN A WHITE DWARF MERGER

Journal Article Garcia-Hernandez, D; Hinkle, K; Lambert, David - Astrophysical Journal

We present high-resolution (R {approx} 50, 000) observations of near-IR transitions of CO and CN of the five known hydrogen-deficient carbon (HdC) stars and four R Coronae Borealis (RCB) stars. We perform an abundance analysis of these stars by using spectrum synthesis and state-of-the-art MARCS model atmospheres for cool hydrogen-deficient stars. Our analysis confirms reports by Clayton and colleagues that those HdC stars exhibiting CO lines in their spectrum and the cool RCB star S Aps are strongly enriched in {sup 18}O (with {sup 16}O/{sup 18}O ratios ranging from 0.3 to 16). Nitrogen and carbon are in the form ofmore »« less
https://doi.org/10.1088/0004-637X/696/2/1733; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)
Evolving R Coronae Borealis stars with mesa

Journal Article Lauer, Amber; Chatzopoulos, Emmanouil; Clayton, Geoffrey; ... - Monthly Notices of the Royal Astronomical Society

The R Coronae Borealis (RCB) stars are rare hydrogen-deficient, carbon-rich supergiants. They undergo extreme, irregular declines in brightness of many magnitudes due to the formation of thick clouds of carbon dust. It is thought that RCB stars result from the mergers of CO/He white dwarf (WD) binaries. We constructed post-merger spherically symmetric models computed with the mesa code, and then followed the evolution into the region of the Hertzsprung-Russell (H-R) diagram where the RCB stars are located. We also investigated nucleosynthesis in the dynamically accreting material of CO/He WD mergers which may provide a suitable environment for significant production ofmore »« less
https://doi.org/10.1093/mnras/stz1732
DO R CORONAE BOREALIS STARS FORM FROM DOUBLE WHITE DWARF MERGERS?

Journal Article Staff, Jan.; Clayton, Geoffrey; Tohline, Joel; ... - Astrophysical Journal

A leading formation scenario for R Coronae Borealis (RCB) stars invokes the merger of degenerate He and CO white dwarfs (WDs) in a binary. The observed ratio of {sup 16}O/{sup 18}O for RCB stars is in the range of 0.3-20 much smaller than the solar value of {approx}500. In this paper, we investigate whether such a low ratio can be obtained in simulations of the merger of a CO and a He WD. We present the results of five three-dimensional hydrodynamic simulations of the merger of a double WD system where the total mass is 0.9 M{sub Sun} and themore »« less
https://doi.org/10.1088/0004-637X/757/1/76
THE GALACTIC R CORONAE BOREALIS STARS: THE C{sub 2} SWAN BANDS, THE CARBON PROBLEM, AND THE {sup 12}C/{sup 13}C RATIO

Journal Article Hema, B; Pandey, Gajendra - Astrophysical Journal

Observed spectra of R Coronae Borealis (RCB) and hydrogen-deficient carbon (HdC) stars are analyzed by synthesizing the C{sub 2} Swan bands (1, 0), (0, 0), and (0, 1) using our detailed line list and the Uppsala model atmospheres. The (0, 1) and (0, 0) C{sub 2} bands are used to derive the {sup 12}C abundance, and the (1, 0) {sup 12}C{sup 13}C band to determine the {sup 12}C/{sup 13}C ratios. The carbon abundance derived from the C{sub 2} Swan bands is about the same for the adopted models constructed with different carbon abundances over the range 8.5 (C/He = 0.1%)more »« less
https://doi.org/10.1088/0004-637X/747/2/102
Evolving R Coronae Borealis stars with mesa

Journal Article Lauer, Amber; Chatzopoulos, Emmanouil; Clayton, Geoffrey; ... - Monthly Notices of the Royal Astronomical Society

ABSTRACT The R Coronae Borealis (RCB) stars are rare hydrogen-deficient, carbon-rich supergiants. They undergo extreme, irregular declines in brightness of many magnitudes due to the formation of thick clouds of carbon dust. It is thought that RCB stars result from the mergers of CO/He white dwarf (WD) binaries. We constructed post-merger spherically symmetric models computed with the mesa code, and then followed the evolution into the region of the Hertzsprung-Russell (H−R) diagram where the RCB stars are located. We also investigated nucleosynthesis in the dynamically accreting material of CO/He WD mergers which may provide a suitable environment for significant productionmore »« less
Cited by 17
https://doi.org/10.1093/mnras/stz1732

Similar Records