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Title: DISCOVERY OF RELATIVELY HYDROGEN-POOR GIANTS IN THE GALACTIC GLOBULAR CLUSTER ω CENTAURI

Abstract

In this Letter, the results of our low-resolution spectroscopic survey for identifying hydrogen-deficient stars in the red giant sample of the globular cluster ω Cen are reported. Spectral analyses were carried out on the basis of the strengths of the (0, 0) MgH band and the Mg b triplet. In our sample, four giants were identified with weak/absent MgH bands in their observed spectra, which was unexpected for their well determined stellar parameters. The Mg abundances for the program stars were determined from the subordinate lines of the MgH band to the blue of the Mg b triplet, using the spectral synthesis technique. The derived Mg abundances for the program stars were as expected for the red giants of ω Cen, except for the four identified candidates. The determined Mg abundances of these four candidates are much lower than that expected for the red giants of ω Cen, and are unacceptable based on the strengths of the Mg b triplet in their observed spectra. Hence, a plausible explanation for the weak/absent MgH bands in the observed spectra of these stars is a relatively lower abundance of hydrogen in their atmospheres. These giants may belong to the group of helium-enriched red giants of ω Cen.

Authors:
;  [1]
  1. Indian Institute of Astrophysics, Bengaluru, Karnataka 560034 (India)
Publication Date:
OSTI Identifier:
22365094
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal Letters
Additional Journal Information:
Journal Volume: 792; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 2041-8205
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; ELEMENT ABUNDANCE; HELIUM; HYDROGEN; MAGNESIUM HYDRIDES; RED GIANT STARS; RESOLUTION; STAR CLUSTERS; SYNTHESIS; TRIPLETS

Citation Formats

Hema, B. P., and Pandey, Gajendra, E-mail: hema@iiap.res.in, E-mail: pandey@iiap.res.in. DISCOVERY OF RELATIVELY HYDROGEN-POOR GIANTS IN THE GALACTIC GLOBULAR CLUSTER ω CENTAURI. United States: N. p., 2014. Web. doi:10.1088/2041-8205/792/2/L28.
Hema, B. P., & Pandey, Gajendra, E-mail: hema@iiap.res.in, E-mail: pandey@iiap.res.in. DISCOVERY OF RELATIVELY HYDROGEN-POOR GIANTS IN THE GALACTIC GLOBULAR CLUSTER ω CENTAURI. United States. doi:10.1088/2041-8205/792/2/L28.
Hema, B. P., and Pandey, Gajendra, E-mail: hema@iiap.res.in, E-mail: pandey@iiap.res.in. Wed . "DISCOVERY OF RELATIVELY HYDROGEN-POOR GIANTS IN THE GALACTIC GLOBULAR CLUSTER ω CENTAURI". United States. doi:10.1088/2041-8205/792/2/L28.
@article{osti_22365094,
title = {DISCOVERY OF RELATIVELY HYDROGEN-POOR GIANTS IN THE GALACTIC GLOBULAR CLUSTER ω CENTAURI},
author = {Hema, B. P. and Pandey, Gajendra, E-mail: hema@iiap.res.in, E-mail: pandey@iiap.res.in},
abstractNote = {In this Letter, the results of our low-resolution spectroscopic survey for identifying hydrogen-deficient stars in the red giant sample of the globular cluster ω Cen are reported. Spectral analyses were carried out on the basis of the strengths of the (0, 0) MgH band and the Mg b triplet. In our sample, four giants were identified with weak/absent MgH bands in their observed spectra, which was unexpected for their well determined stellar parameters. The Mg abundances for the program stars were determined from the subordinate lines of the MgH band to the blue of the Mg b triplet, using the spectral synthesis technique. The derived Mg abundances for the program stars were as expected for the red giants of ω Cen, except for the four identified candidates. The determined Mg abundances of these four candidates are much lower than that expected for the red giants of ω Cen, and are unacceptable based on the strengths of the Mg b triplet in their observed spectra. Hence, a plausible explanation for the weak/absent MgH bands in the observed spectra of these stars is a relatively lower abundance of hydrogen in their atmospheres. These giants may belong to the group of helium-enriched red giants of ω Cen.},
doi = {10.1088/2041-8205/792/2/L28},
journal = {Astrophysical Journal Letters},
issn = {2041-8205},
number = 2,
volume = 792,
place = {United States},
year = {2014},
month = {9}
}