Please use this identifier to cite or link to this item: http://hdl.handle.net/2248/8318
Title: Asteroseismology Sheds Light on the Origin of Carbon-deficient Red Giants: Likely Merger Products and Linked to the Li-rich Giants
Authors: Maben, Sunayana
Campbel, Simon W
Bharat Kumar, Y
Reddy, B. E
Zhao, Gang
Keywords: Asteroseismology
Low mass stars
Stellar abundances
Chemically peculiar giant stars
Stellar mergers
Issue Date: 1-Nov-2023
Publisher: IOP Publishing
Citation: The Astrophysical Journal, Vol. 957, No 1, 18
Abstract: Carbon-deficient red giants (CDGs) are a peculiar class of stars that have eluded explanation for decades. We aim to better characterize CDGs by using asteroseismology (Kepler, TESS) combined with spectroscopy (APOGEE, LAMOST), and astrometry (Gaia). We discovered 15 new CDGs in the Kepler field, and confirm that CDGs are rare, as they are only 0.15% of our background sample. Remarkably, we find that our CDGs are almost exclusively in the red clump (RC) phase. Asteroseismic masses reveal that our CDGs are primarily low-mass stars (M  2 Me), in contrast to previous studies, which suggested they are intermediate mass (M = 2.5–5.0 Me) based on HR diagrams. A very high fraction of our CDGs (50%) are also Li-rich giants. We observe a bimodal distribution of luminosity in our CDGs, with one group having normal RC luminosity and the other being a factor of 2 more luminous than expected for their masses. We find demarcations in chemical patterns and luminosities, which lead us to split them into three groups: (i) normal-luminosity CDGs, (ii) overluminous CDGs, and (iii) overluminous highly polluted CDGs. We conclude that a merger of a helium white dwarf with a red giant branch star is the most likely scenario for the two groups of overluminous stars. Binary mass-transfer from intermediate-mass asymptotic giant branch stars is a possibility for the highly polluted overluminous group. For the normal-luminosity CDGs, we cannot distinguish between core He-flash pollution or lower-mass merger scenarios. Due to the overlap with the CDGs, Li-rich giants may have similar formation channels
Description: Open Access
Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation, and DOI.
URI: http://hdl.handle.net/2248/8318
ISSN: 1538-4357
Appears in Collections:IIAP Publications

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