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Title: ANALYSIS OF THE PICO DOS DIAS SURVEY HERBIG Ae/Be CANDIDATES

Abstract

A large sample of Herbig Ae/Be (HAeBe) candidates, distributed in different Galactic regions south to declination +30 deg., were identified by the Pico dos Dias Survey (a search for young stellar objects based on IRAS colors). Most of the candidates are nearby or associated with star-forming clouds, but several others are considered isolated objects. Aiming to verify the young nature of 93 HAeBe candidates, we searched for additional information that could be useful to confirm if they are pre-main-sequence (PMS) stars or evolved objects, which coincidentally show similar IRAS colors. By adopting a spectral index that is related to the amount of infrared excess and the shape of the spectral energy distribution, we have classified the sample according to three groups, which are analyzed on the basis of (1) circumstellar luminosity; (2) spatial distribution; (3) optical polarization; (4) near-infrared colors; (5) stellar parameters (mass, age, effective temperature); and (5) intensity of emission lines. Our analysis indicates that only 76% of the studied sample, mainly the group with intermediate to low levels of circumstellar emission, can be more confidently considered PMS stars. The nature of the remaining stars, which are in the other group that contains the highest levels of infraredmore » excess, remains to be confirmed. They share the same characteristics of evolved objects, requiring complementary studies in order to correctly classify them. At least seven objects show characteristics typical of post-asymptotic giant branch or proto-planetary nebulae.« less

Authors:
 [1];  [2];  [3];  [4];  [5]
  1. Laboratorio Nacional de Astrofisica/MCT, Rua Estados Unidos 154, 37504-364 Itajuba, MG (Brazil)
  2. Universidade de Sao Paulo, IAG, Rua do Matao 1226, 05508-900 Sao Paulo, SP (Brazil)
  3. Instituto Nacional de Pesquisas Espaciais/MCT, Av. dos Astronautas 1758, 12227-010 Sao Jose dos Campos, SP (Brazil)
  4. Fundacao Santo Andre, FAENG, Rua Principe de Gales 821, 09060-650 Santo Andre, SP (Brazil)
  5. Evergreen Valley College, 3095 Yerba Buena Rd., San Jose, CA, 95135 (United States), E-mail: marilia@lna.br
Publication Date:
OSTI Identifier:
21301476
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (New York, N.Y. Online); Journal Volume: 139; Journal Issue: 1; Other Information: DOI: 10.1088/0004-6256/139/1/27; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; ASYMPTOTIC SOLUTIONS; EMISSION; ENERGY SPECTRA; LUMINOSITY; MASS; MATTER; PLANETARY NEBULAE; POLARIZATION; SPATIAL DISTRIBUTION; STARS

Citation Formats

Sartori, Marilia J., Gregorio-Hetem, Jane, Rodrigues, Claudia V., Annibal Hetem, and Batalha, Celso. ANALYSIS OF THE PICO DOS DIAS SURVEY HERBIG Ae/Be CANDIDATES. United States: N. p., 2010. Web. doi:10.1088/0004-6256/139/1/27; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Sartori, Marilia J., Gregorio-Hetem, Jane, Rodrigues, Claudia V., Annibal Hetem, & Batalha, Celso. ANALYSIS OF THE PICO DOS DIAS SURVEY HERBIG Ae/Be CANDIDATES. United States. doi:10.1088/0004-6256/139/1/27; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Sartori, Marilia J., Gregorio-Hetem, Jane, Rodrigues, Claudia V., Annibal Hetem, and Batalha, Celso. 2010. "ANALYSIS OF THE PICO DOS DIAS SURVEY HERBIG Ae/Be CANDIDATES". United States. doi:10.1088/0004-6256/139/1/27; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
@article{osti_21301476,
title = {ANALYSIS OF THE PICO DOS DIAS SURVEY HERBIG Ae/Be CANDIDATES},
author = {Sartori, Marilia J. and Gregorio-Hetem, Jane and Rodrigues, Claudia V. and Annibal Hetem and Batalha, Celso},
abstractNote = {A large sample of Herbig Ae/Be (HAeBe) candidates, distributed in different Galactic regions south to declination +30 deg., were identified by the Pico dos Dias Survey (a search for young stellar objects based on IRAS colors). Most of the candidates are nearby or associated with star-forming clouds, but several others are considered isolated objects. Aiming to verify the young nature of 93 HAeBe candidates, we searched for additional information that could be useful to confirm if they are pre-main-sequence (PMS) stars or evolved objects, which coincidentally show similar IRAS colors. By adopting a spectral index that is related to the amount of infrared excess and the shape of the spectral energy distribution, we have classified the sample according to three groups, which are analyzed on the basis of (1) circumstellar luminosity; (2) spatial distribution; (3) optical polarization; (4) near-infrared colors; (5) stellar parameters (mass, age, effective temperature); and (5) intensity of emission lines. Our analysis indicates that only 76% of the studied sample, mainly the group with intermediate to low levels of circumstellar emission, can be more confidently considered PMS stars. The nature of the remaining stars, which are in the other group that contains the highest levels of infrared excess, remains to be confirmed. They share the same characteristics of evolved objects, requiring complementary studies in order to correctly classify them. At least seven objects show characteristics typical of post-asymptotic giant branch or proto-planetary nebulae.},
doi = {10.1088/0004-6256/139/1/27; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)},
journal = {Astronomical Journal (New York, N.Y. Online)},
number = 1,
volume = 139,
place = {United States},
year = 2010,
month = 1
}
  • A survey for H/sub 2/ 1-0 S(1) emission in 16 Herbig-Haro (HH) objects and three exciting stars for HH objects is reported. Eleven HH objects which show low-excitation optical spectra exhibit H/sub 2/ emission. One object (HH 43) is more than twice as bright as any previously reported HH object. In addition, spectra in the range 1.6-2.55 microns are reported for HH 43 and HH 120, and a 2.0-2.55 micron spectrum is presented for HH 26. The spectra yield estimates of the H/sub 2/ density and temperature ranges in these objects. The role of ultraviolet H/sub 2/ emission-line fluorescence inmore » HH 43 with respect to cascading among excited vibrational states of the ground electronic state is discussed. Models which may account for the combined ultraviolet, optical, and near-IR spectra of HHs are briefly analyzed. 35 references.« less
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  • We have acquired submillimeter observations of 33 fields containing 37 Herbig Ae/Be (HAEBE) stars or potential HAEBE stars, including SCUBA maps of all but two of these stars. Nine target stars show extended dust emission. The other 18 are unresolved, suggesting that the dust envelopes or disks around these stars are less than a few arcseconds in angular size. In several cases, we find that the strongest submillimeter emission originates from younger, heavily embedded sources rather than from the HAEBE star, which means that previous models must be viewed with caution. These new data, in combination with far-infrared flux measurementsmore » available in the literature, yield spectral energy distributions (SEDs) from far-infrared to millimeter wavelengths for all the observed objects. Isothermal fits to these SEDs demonstrate excellent fits, in most cases, to the flux densities longward of 100 {mu}m. We find that a smaller proportion of B-type stars than A- and F-type stars are surrounded by circumstellar disks, suggesting that disks around B stars dissipate on shorter timescales than those around later spectral types. Our models also reveal that the mass of the circumstellar material and the value of {beta} are correlated, with low masses corresponding to low values of {beta}. Since low values of {beta} imply large grain sizes, our results suggest that a large fraction of the mass in low-{beta} sources is locked up in very large grains. Several of the isolated HAEBE stars have disks with very flat submillimeter SEDs. These disks may be on the verge of forming planetary systems.« less
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