Colloquium : Black hole X-ray binaries- accurate distances and natal kicks

© Pikky Atri (ICRAR - Curtin)

Even though the first black hole (BH) was detected decades ago, the mechanism by which BHs form is not well understood. Theoretical models suggest that BHs are born when a massive star dies, either with or without a supernova explosion. BHs formed following a supernova explosion are hypothesized to get strong natal kicks, whereas direct collapse BHs do not incur such a kick.

In order to obtain an observationally constrained natal kick distribution for Black hole X-ray binaries (BHXBs) we use Monte Carlo simulations to determine the probability distribution of the Plane crossing velocity for 16 systems. We measure the peculiar velocity of each system by combining their radial velocities, distances, archival and Gaia proper motions and track their Galactocentric orbits back to the time of Plane crossing.

We use the high resolution of Very Long Baseline Interferometry (VLBI) networks in the USA, Europe, and Australia to measure the proper motions of 3 new BHXBs. We also use VLBI to obtain the model-independent distance to a BHXB, MAXI J1820+070, by measuring the parallax of the source.

In this talk, I will present the implications of this newly constrained kick velocity distribution of BHXBs on the birth mechanism of BHs, on BH-BH mergers, on retention of BHs in globular clusters and on the spin-orbit misalignment of BHXBs. I will also report on the parallax measurement of MAXI J1820+070.