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Title: NEON AND CNO ABUNDANCES FOR EXTREME HELIUM STARS-A NON-LTE ANALYSIS

Abstract

A non-LTE (NLTE) abundance analysis was carried out for three extreme helium stars (EHes): BD+10{sup 0} 2179, BD-9{sup 0} 4395, and LS IV+6{sup 0} 002, from their optical spectra with NLTE model atmospheres. NLTE TLUSTY model atmospheres were computed with H, He, C, N, O, and Ne treated in NLTE. Model atmosphere parameters were chosen from consideration of fits to observed He I line profiles and ionization equilibria of C and N ions. The program SYNSPEC was then used to determine the NLTE abundances for Ne as well as H, He, C, N, and O. LTE neon abundances from Ne I lines in the EHes: LSE 78, V1920 Cyg, HD 124448, and PV Tel, are derived from published models and an estimate of the NLTE correction applied to obtain the NLTE Ne abundance. We show that the derived abundances of these key elements, including Ne, are well matched with semi-quantitative predictions for the EHe resulting from a cold merger (i.e., no nucleosynthesis during the merger) of an He white dwarf with a C-O white dwarf.

Authors:
 [1]
  1. Indian Institute of Astrophysics, Bangalore, 560034 (India)
Publication Date:
OSTI Identifier:
21567518
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 727; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/727/2/122; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ELEMENT ABUNDANCE; HELIUM; NEON; STAR EVOLUTION; STELLAR ATMOSPHERES; WHITE DWARF STARS; ABUNDANCE; ATMOSPHERES; DWARF STARS; ELEMENTS; EVOLUTION; FLUIDS; GASES; NONMETALS; RARE GASES; STARS

Citation Formats

Pandey, Gajendra, and Lambert, David L., E-mail: pandey@iiap.res.in, E-mail: dll@astro.as.utexas.edu. NEON AND CNO ABUNDANCES FOR EXTREME HELIUM STARS-A NON-LTE ANALYSIS. United States: N. p., 2011. Web. doi:10.1088/0004-637X/727/2/122.
Pandey, Gajendra, & Lambert, David L., E-mail: pandey@iiap.res.in, E-mail: dll@astro.as.utexas.edu. NEON AND CNO ABUNDANCES FOR EXTREME HELIUM STARS-A NON-LTE ANALYSIS. United States. https://doi.org/10.1088/0004-637X/727/2/122
Pandey, Gajendra, and Lambert, David L., E-mail: pandey@iiap.res.in, E-mail: dll@astro.as.utexas.edu. 2011. "NEON AND CNO ABUNDANCES FOR EXTREME HELIUM STARS-A NON-LTE ANALYSIS". United States. https://doi.org/10.1088/0004-637X/727/2/122.
@article{osti_21567518,
title = {NEON AND CNO ABUNDANCES FOR EXTREME HELIUM STARS-A NON-LTE ANALYSIS},
author = {Pandey, Gajendra and Lambert, David L., E-mail: pandey@iiap.res.in, E-mail: dll@astro.as.utexas.edu},
abstractNote = {A non-LTE (NLTE) abundance analysis was carried out for three extreme helium stars (EHes): BD+10{sup 0} 2179, BD-9{sup 0} 4395, and LS IV+6{sup 0} 002, from their optical spectra with NLTE model atmospheres. NLTE TLUSTY model atmospheres were computed with H, He, C, N, O, and Ne treated in NLTE. Model atmosphere parameters were chosen from consideration of fits to observed He I line profiles and ionization equilibria of C and N ions. The program SYNSPEC was then used to determine the NLTE abundances for Ne as well as H, He, C, N, and O. LTE neon abundances from Ne I lines in the EHes: LSE 78, V1920 Cyg, HD 124448, and PV Tel, are derived from published models and an estimate of the NLTE correction applied to obtain the NLTE Ne abundance. We show that the derived abundances of these key elements, including Ne, are well matched with semi-quantitative predictions for the EHe resulting from a cold merger (i.e., no nucleosynthesis during the merger) of an He white dwarf with a C-O white dwarf.},
doi = {10.1088/0004-637X/727/2/122},
url = {https://www.osti.gov/biblio/21567518}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 727,
place = {United States},
year = {Tue Feb 01 00:00:00 EST 2011},
month = {Tue Feb 01 00:00:00 EST 2011}
}