Population synthesis of helium white dwarf--red giant star mergers and the formation of lithium-rich giants and carbon stars

Abstract

The formation histories of lithium-rich and carbon-rich red giants are not yet understood. It has been proposed that the merger of a helium-core white dwarf with a red giant branch star might provide a solution. We have computed an extended grid of post-merger evolution models and combined these with predictions of binary star population synthesis. The results strongly support the proposal that the merger of a helium white dwarf with a red giant branch star can provide the progenitors of both lithium-rich red clump stars and early-R carbon stars. The distribution of post-merger models in $T_{\mathrm{eff}}$, $\log g$, $\log L$, the surface abundances of lithium and carbon, and the predicted space densities agree well with the observed distributions of these parameters for Li-rich and early-R stars in the Galaxy.

14 pages, 19 figues, accepted to ApJ

References in corpus (15)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Near-Infrared Photometry of Globular Clusters Towards the Galactic Bulge: Observations and Photometric Metallicity Indicators
• Post-merger evolution of carbon-oxygen + helium white dwarf binaries and the origin of R Coronae Borealis and extreme helium stars
• Survey of Li-rich giants among Kepler and LAMOST fields: Determination of Li-rich giants Evolutionary Phase
• The Penn State - Torun Centre for Astronomy Planet Search stars. II. Lithium abundance analysis of the Red Giant Clump sample
• Enormous Li-enhancement preceding red giant phases in low-mass stars in the Milky Way halo
• Study of Lithium Rich Giants with the GALAH Spectroscopic Survey
• Origin of the early-type R stars: a binary-merger solution to a century-old problem?
• White-dwarf red-giant mergers, early-type R stars, J stars and lithium
• Evolution models of helium white dwarf--main sequence star merger remnants
• Common Envelope Mergers: A Possible Channel for Forming Single sdB Stars
• On Lithium-Rich Red Giants. II. Engulfment on the Giant Branch of Trumpler 20
• The Puzzling Li-rich Red Giant Associated with NGC 6819
• The gravitational-wave signal generated by a galactic population of double neutron-star binaries
• High-resolution spectroscopic analysis of a large sample of Li-rich giants found by LAMOST

Cited by in corpus (25)

• Most Lithium-rich Low-mass Evolved Stars Revealed as Red Clump stars by Asteroseismology and Spectroscopy
• Discovery of post-mass-transfer helium-burning red giants using asteroseismology
• Lithium Enrichment Signatures of Planetary Engulfment Events in Evolved Stars
• WIYN Open Cluster Study: The Old Open Cluster, NGC 188, and a Re-evaluation of Lithium-Richness Among Red Giants
• A close-in giant planet escapes engulfment by its star
• The carbon star mystery: forty years later
• Lithium Evolution of Giant Stars Observed by LAMOST and Kepler
• Evidence of extra-mixing in field giants as traced by lithium and carbon isotope ratio
• Li-rich Giants in LAMOST Survey. III. The statistical analysis of Li-rich giants
• Characterization of Kepler targets based on medium-resolution LAMOST spectra analyzed with ROTFIT
• Lithium in coalesced non-compact stars
• Li-rich and super Li-rich giants produced by element diffusion
• The population synthesis of Wolf-Rayet stars involving binary merger channels
• Are Lithium-Rich Giants Binaries? A Radial Velocity Variability Analysis of 1,400 Giants
• Lithium in Kepler Red Giants: Defining Normal and Anomalous
• Li-rich Giants Identified from LAMOST DR8 Low-Resolution Survey
• LAMOST/HRS Spectroscopic Analysis of Two New Li-rich Giants
• Anomalously low-mass core-He-burning star in NGC 6819 as a post-common-envelope phase product
• Convective Mixing: The Formation Channel of Li-rich Giants
• Discovery of a Metal-Poor Red Giant Star with the Highest Ultra-Lithium Enhancement
• An Unsupervised Machine Learning Approach to Identify Spectral Energy Distribution Outliers: Application to the S-PLUS DR4 data
• Unevolved Li-rich stars at low metallicity: a possible formation pathway through novae
• Exploring the History of Stellar Mergers with Chemistry: Examining the Origins of Massive $\alpha$-Enriched Stars using Carbon Isotope Ratios
• A Main Sequence CH-star in the globular cluster M55 (NGC 6809)
• A Near-Infrared and Optical Study of NGC 5822: An Open Cluster Hosting Barium-stars and Lithium-Enriched Giant Stars