Estimates of black-hole natal kick velocities from observations of low-mass X-ray binaries

Understand

The birth kicks of black holes, arising from asymmetric mass ejection or neutrino emission during core-collapse supernovae, are of great interest for both observationally constraining supernova models and population-synthesis studies of binary evolution.

• Recently, several efforts were undertaken to estimate black hole birth kicks from observations of black-hole low-mass X-ray binaries.
• We follow up on this work, specifically focussing on the highest estimated black-hole kick velocities.
• We find that existing observations do not require black hole birth kicks in excess of approximately 100 km/s, although higher kicks are not ruled out.