Population synthesis of Galactic subdwarf B stars

TL;DR

This paper reviews population synthesis methods for binary stars and explores the formation mechanisms of single subdwarf B stars and helium-core white dwarfs in the Galaxy, highlighting the potential roles of white dwarf mergers and sub-stellar interactions.

Contribution

It presents preliminary results on the Galactic population of sdB stars, emphasizing the possible formation channels involving white dwarf mergers and sub-stellar companions.

Findings

Both white dwarf mergers and sub-stellar interactions may produce single sdB stars.

Most helium white dwarfs likely form from interactions with sub-stellar companions.

Current observations support multiple formation mechanisms for these objects.

Abstract

I briefly review the method of population synthesis of binary stars and discuss the preliminary results of a study of the Galactic population of subdwarf B stars. In particular I focus on the formation of (apparently) single sdB stars and their relation to (apparently) single helium-core white dwarfs. I discuss the merits of mergers of two helium white dwarfs and interactions with sub-stellar companions for explaining these single objects. A preliminary conclusion is that the current observations suggest both mechanisms may contribute, but that the helium white dwarfs are likely formed in majority from interactions with sub-stellar companions.