Speaker
Description
X-ray binaries (XRBs) are our most accessible way to probe populations of Galactic compact objects in the X-ray regime, and offer crucial constraints on Galactic stellar evolution models. Previously reported distributions of XRBs plateau at intermediate luminosities of $10^{35}$ erg/s, and only reach fluxes down to a few $10^{-12}$ cgs. eROSITA’s improved sensitivity allows us to extend this further by a factor ≥ 10, reaching the little explored low luminosity regime, providing improved constraints on the log(N)-log(S) distributions of both persistently faint XRBs and transients in quiescence.
We present log(N)-log(S) distributions of high mass (HMXBs) and low mass X-ray binaries (LMXBs), as obtained using eROSITA detections of nearly 150 XRBs in the western Galactic hemisphere. We perform detailed comparisons to results from previous missions, which are reproduced after accounting for variability for the first time. We discuss the effects of including candidate XRBs identified during the survey. Since eROSITA detections are a proxy for persistent or quiescent activity, we report on neutron star HMXBs that remain observable at low luminosities even when not in outburst (long considered off states) and further remark on eROSITA’s discovery of several such neutron star HMXBs, providing new test cases for low luminosity accretion.
