Chad Bender (University of Arizona/Steward Observatory)
Title TBA
Abstract TBA

Koushik Sen (University of Arizona/Steward Observatory)
X-ray emission from black holes in orbit with helium stars
Tidally induced spin-up of stripped helium stars in short-period (< 1 d) binaries with black holes (BHs) has been proposed as one of the possible mechanisms to reproduce the high-spin tail of the BH spin distribution derived from gravitational wave (GW) merger observations. At such short periods, a fraction of the intense stellar wind from the stripped helium stars may be accreted by the BHs, and its gravitational potential energy may be released as X-rays. We estimate lower limits on the X-ray luminosity and its observability from the population of stripped helium star+BH binaries that evolve into GW mergers. We find that 10-50 % of stripped-helium stars in the above population transfer enough wind matter onto the BH to produce X-ray luminosities above 10**35 erg/s, up to 10**39 erg/s. We show that most of these X-ray-bright systems also have the shortest orbital periods where tides spin up the stripped helium star component, thereby establishing an empirically testable correlation.