Modeling He-rich subdwarfs through the hot-flasher scenario (brief version)

TL;DR

This study uses 1D simulations to explore the hot-flasher scenario for forming He-rich subdwarf stars, analyzing how different conditions affect surface abundances and the transformation of atmospheres.

Contribution

It provides a comprehensive set of models for hot-flasher evolution across various metallicities and examines the impact of convective mixing and element diffusion.

Findings

Hot-flasher scenario can explain He-sdO star formation

Element diffusion can turn He-rich atmospheres into He-deficient

Models match observed properties and distribution of He-sdO stars

Abstract

We present 1D numerical simulations aimed at studying the hot-flasher scenario for the formation of He-rich subdwarf stars. Sequences were calculated for a wide range of metallicities and with the He core flash at different points of the post-RGB evolution (i.e. different remnant masses). We followed the complete evolution from the ZAMS, through the hot-flasher event, and to the subdwarf stage for all kinds of hot-flashers. This allows us to present a homogeneous set of abundances for different metallicities and all flavors of hot-flashers. We extend the scope of our work by analyzing the effects in the predicted surface abundances of some standard assumptions in convective mixing and the effects of element diffusion. We find that the hot-flasher scenario is a viable explanation for the formation of He-sdO stars. Our results also show that element diffusion may produce the transformation of (post hot-flasher) He-rich atmospheres into He-deficient ones. If this is so, then the hot-flasher scenario is able to reproduce both the observed properties and distribution of He-sdO stars.