Institute of Astronomy

Helium Stars, Heavy Metals, High Velocities and Explosions 

SpeakerTalk DateTalk Series
Simon Jeffery (Armagh)31 January 2019Institute of Astronomy Colloquia


The term "hot subdwarf" refers to stars which are smaller than hydrogen-burning main-sequence stars and larger than white dwarfs. It includes stars in several different advanced stages of evolution. Most have surfaces severely depleted in either hydrogen or helium; some explanation exists for most of these. My talk will review the general properties of helium-poor and helium-rich subdwarfs and contemporary models for their origins.  I will introduce the extremely rare "intermediate helium subdwarfs", which pose significant challenges.  Several show extraordinary surface abundances of the heavy metals zirconium, yttrium, strontium, germanium and lead. All of these heavy-metal stars are on high-energy galactic orbits. Two pulsate in modes which, until now, were thought to be impossible. Now, new theoretical results force us toward new questions and new ideas about the origin of these stars.