Pulsations in hot subdwarf stars: recent advances and prospects for testing stellar physics

Abstract

Abstract. The evolved, core helium burning, extreme horizontal branch stars (also known as hot B subdwarfs) host several classes of pulsators showing either p-or g-modes, or both. They offer particularly favorable conditions for probing with asteroseismology their internal structure, thus constituting arguably the most interesting seismic window for this intermediate stage of stellar evolution. G-modes in particular have the power to probe deep inside these stars, down to the convective He-burning core boundary where uncertain physics (convection, overshooting, semi-convection) is at work. Space data recently obtained with CoRoT and Kepler are offering us the possibility to probe these regions in detail and possibly shed new light on how these processes shape the core structure. In this short paper, we present the most recent advances that have taken place in this field and we provide hints of the foreseen future achievements of hot subdwarf asteroseismology.

Discovery of a second pulsating intermediate helium-enriched sdOB star

“…Consequently they have masses close to the canonical value required for the He-flash (∼0.48 M ), to which their remaining hydrogen envelope contributes minimally ( < ∼ 0.02 M ). The discovery of the first pulsating sdB stars (Kilkenny et al 1997) two decades ago proved to be a stepping stone for our understanding of these particular objects (see Heber 2016 andCharpinet et al 2016 for recent reviews). Their asteroseismic modeling has allowed, among other things, the probing of their structural properties such as core size and composition (e.g.…”