Speaker
Description
Accretion onto compact stellar remnants can give rise to luminous X-ray emission, whose properties depend on factors such as the accretion rate and geometry. The majority of the known stellar-mass black holes in the Galaxy have been discovered through their bright X-ray emission, predominantly during outbursts. However, while there are an estimated $10^8$ stellar-mass black holes in the Milky Way, only a few dozen confirmed and candidate black holes have been detected to date, most of which are in X-ray binary systems. However, such systems spend the majority of their time in a faint, quiescent state, and the recurrence times of transient outbursts can be several decades. Furthermore, the sensitivity of existing X-ray all-sky monitors such as RXTE, Swift/BAT, or MAXI limits our ability to detect low-luminosity outbursts. Recent efforts have attempted to detect quiescent accreting systems with deep X-ray observations of dense environments such as globular clusters or the Galactic Bulge. Over the past few years, optical spectroscopic and astrometric surveys have also begun to uncover a new population of black holes in very wide orbits, with extremely low accretion rates. In this talk I will give an overview of these efforts to detect new black hole and neutron star systems, and the insights they provide into the efficiency of accretion at the lowest luminosities. I will touch on how the sensitivity and sky coverage of eROSITA could contribute to these efforts, particularly when coupled with multi-wavelength follow-up in the optical and radio bands.
