The red giant branch phase transition: Implications for the RGB luminosity function bump and detections of Li-rich red clump stars

Abstract

We performed a detailed study of the evolution of the luminosity of He-ignition stage and of the red giant branch bump luminosity during the red giant branch phase transition for various metallicities. To this purpose we calculated a grid of stellar models that sample the mass range of the transition with a fine mass step equal to $0.01{\mathrm{M}}_{\odot }$. We find that for a stellar population with a given initial chemical composition, there is a critical age (of 1.1-1.2~Gyr) around which a decrease in age of just 20-30 million years causes a drastic drop in the red giant branch tip brightness. We also find a narrow age range (a few $10^7$ yr) around the transition, characterized by the luminosity of the red giant branch bump being brighter than the luminosity of He ignition. We discuss a possible link between this occurrence and observations of Li-rich core He-burning stars.

5 pages, 4 figures, Astronomy & Astrophysics in press

References in corpus (3)

• Old puzzle, new insights: a lithium rich giant quietly burning helium in its core
• On the red-giant luminosity bump
• Red Giant Branch Bump Star Counts in Data and Stellar Models

Cited by in corpus (6)

• Lithium in red giant stars: Constraining non-standard mixing with large surveys in the Gaia era
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters - XII. The RGB Bumps of multiple stellar populations
• The Gaia-ESO Survey: properties of newly discovered Li-rich giants
• New determination of abundances and stellar parameters for a set of weak G-band stars
• Lithium Inventory of 2 $M_{\odot }$ Red Clump Stars in Open Clusters: A Test of the Helium Flash Mechanism
• Constraining dark photon properties with Asteroseismology