Yue Zhao

When a compact object is formed, an impulse (kick) will be imparted to the system by the mass lost during the core-collapse supernova (SN). A number of other mechanisms may impart an additional kick on the system, although evidence for these natal kicks in black hole systems remains limited. Updated Gaia astrometry has recently identified a number of high peculiar velocity (in excess of Galactic motion) compact objects. Here, we focus on the black hole low-mass X-ray binary H 1705−250, which has a peculiar velocity $\upsilon _{\mathrm{pec}}\, =\, 221^{+101}_{-108}\, \,\mathrm{km}\, \mathrm{s}^{-1}$. Using population synthesis to reconstruct its evolutionary history (assuming formation via isolated binary evolution within the Galactic plane), we constrain the properties of the progenitor and pre-SN orbit. The magnitude of a kick solely due to mass-loss is found to be ∼30 km s−1, which cannot account for the high present-day peculiar motion. We therefore deduce that the black hole received an additional natal kick at formation, and place limits on its magnitude, finding it to be ∼295 km s−1 (minimum 90 km s−1). This furthers the argument that these kicks are not limited to neutron stars.