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Globular Cluster UVIT Legacy Survey (GlobULeS). III. Omega Centauri in far-ultraviolet
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(2022) Globular Cluster UVIT Legacy Survey (GlobULeS). III. Omega Centauri in far-ultraviolet. The Astrophysical Journal Letters, 939 (2). L20. doi:10.3847/2041-8213/ac9901 ISSN 2041-8205.
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Official URL: https://doi.org/10.3847/2041-8213/ac9901
Abstract
We present the first comprehensive study of the most massive globular cluster, Omega Centauri, in the far-ultraviolet (FUV), extending from the center to ∼28% of the tidal radius using the Ultraviolet Imaging Telescope on board AstroSat. A comparison of the FUV-optical color–magnitude diagrams with available canonical models reveals that horizontal branch (HB) stars bluer than the knee (hHBs) and the white dwarfs (WDs) are fainter in the FUV by ∼0.5 mag than model predictions. They are also fainter than their counterparts in M13, another massive cluster. We simulated HB with at least five subpopulations, including three He-rich populations with a substantial He enrichment of Y up to 0.43 dex, to reproduce the observed FUV distribution. We find the He-rich younger subpopulations to be radially more segregated than the He-normal older ones, suggesting an in situ enrichment from older generations. The ω Cen hHBs span the same Teff range as their M13 counterparts, but some have smaller radii and lower luminosities. This may suggest that a fraction of ω Cen hHBs are less massive than those of M13, similar to the result derived from earlier spectroscopic studies of outer extreme HB stars. The WDs in ω Cen and M13 have similar luminosity–radius–Teff parameters, and 0.44–0.46 M⊙ He-core WD model tracks evolving from progenitors with Y = 0.4 dex are found to fit the majority of these. This study provides constraints on the formation models of ω Cen based on the estimated range in age, [Fe/H], and Y (in particular) for the HB stars.
Item Type: | Journal Article | ||||||||||||||||||||||||||||||
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Subjects: | Q Science > QB Astronomy | ||||||||||||||||||||||||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||||||||||||||||||||||||
Library of Congress Subject Headings (LCSH): | Stars -- Globular clusters, Horizontal branch stars, Photometry, Ultraviolet, White dwarf stars, HR diagrams, Stars -- Evolution, B stars | ||||||||||||||||||||||||||||||
Journal or Publication Title: | The Astrophysical Journal Letters | ||||||||||||||||||||||||||||||
Publisher: | Institute of Physics Publishing, Inc. | ||||||||||||||||||||||||||||||
ISSN: | 2041-8205 | ||||||||||||||||||||||||||||||
Official Date: | 2 November 2022 | ||||||||||||||||||||||||||||||
Dates: |
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Volume: | 939 | ||||||||||||||||||||||||||||||
Number: | 2 | ||||||||||||||||||||||||||||||
Article Number: | L20 | ||||||||||||||||||||||||||||||
DOI: | 10.3847/2041-8213/ac9901 | ||||||||||||||||||||||||||||||
Status: | Peer Reviewed | ||||||||||||||||||||||||||||||
Publication Status: | Published | ||||||||||||||||||||||||||||||
Access rights to Published version: | Open Access (Creative Commons) | ||||||||||||||||||||||||||||||
Date of first compliant deposit: | 21 December 2022 | ||||||||||||||||||||||||||||||
Date of first compliant Open Access: | 21 December 2022 | ||||||||||||||||||||||||||||||
RIOXX Funder/Project Grant: |
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