Origin of α-rich young stars: clues from C, N, and O. Issue 3 (26th June 2019)

• Record Type: Journal Article
• Authors: Hekker, Saskia; Johnson, Jennifer A
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 487:Issue 3(2019)
• Page Start: 4343
• Page End: 4354
• Publication Date: 2019-06-26
• Subjects: stars: abundances -- Galaxy: abundances; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz1554
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: A small set of chemically old stars that appear young by their independently derived masses has been detected. These are so-called α-rich young stars. For a sample of 51 red-giant stars, for which spectra are available from SDSS/APOGEE and masses are available from asteroseismic measures based on Kepler lightcurves, we derive the C, N, and O abundances through an independent analysis. These stars span a wide range of N/C surface number density ratios. We interpret the high-mass stars with low N/C as being products of mergers or mass transfer during or after first dredge up, because the dredge-up features are the same as for low-mass stars. The α-rich young stars with high N/C follow the expected trend of N/C for their mass, and could be either genuine young stars (leaving their high [α/Fe] unexplained) or the results of mergers on the main sequence.