Jakub Klencki (ESO, Garching)
Massive stars in nearby dwarf galaxies: key to the origin of black hole mergers
The last few years have seen an unprecedented growth in all the aspects of gravitational-wave (GW) astrophysics. At the frontier is population modeling of GW sources and their potential progenitors: massive stars in binary systems. Various clues suggest that bulk of the population of binary black hole mergers may have formed in metal-poor environments. This is likely because low-metallicity stars experience reduced mass loss through winds, allowing them to form more massive black holes. The pressing question is thus now: how well do we really understand the ''basics'' of stellar evolution and the ''classical'' formation scenarios in the regime of low metallicity? In my talk, I will argue against the formation of massive binary black holes through the common-envelope evolution, one of the most prominent channels discussed in the literature. Furthermore, I will show that the textbook picture of mass transfer evolution, where a giant star is stripped of its envelope by an accreting companion, may no longer hold in the case of massive stars at low metallicity. I will discuss implications of our findings for various classes of objects (stripped stars, supernova projenitors, X-ray binaries, LIGO/Virgo sources) and highlight the crucial role of observational constraints coming from young stellar populations in nearby metal-poor dwarf galaxies, now and in the future.