Constraining Black Hole Natal Kicks with Astrometric Microlensing

Abstract Multiple pieces of evidence suggest that neutron stars receive large kicks when formed from the remnant a collapsing star. However, for whether black holes (BHs) natal is less clear, reliant on weak constraints analysis BH X-ray binaries and massive runaway walkaway stars. Here we show, first time, recent microlensing detections offer new method measuring BHs at birth. When identified through both photometric astrometric lensed star has known distance proper motion, mass, distance, motion can be determined. We study velocities components eccentric disrupted during supernova (SN), finding peculiar velocity correlates strongly with kick received birth, typically within 20%, even smaller than orbital velocity. Therefore, by or other compact object binary which core collapse, are in effect received. focus MOA-2011-BLG-191/OGLE-2011-BLG-0462, an isolated, single detected microlensing, consider range possible formation scenarios, including its disruption SN event. determine MOA-2011-BLG-191/OGLE-2011-BLG-0462 Milky Way orbit consistent thick-disk population, but if it was kinematic thin disk ≲100 km s −1 .