Revisiting BH Natal Kicks using Gaia DR3 Kinematics

When massive stars die, they can deliver an impulse to their compact object remnants known as a natal kick. However, most black hole (BH) binaries are old and have likely been kinematically heated by processes other than kicks over their lifetimes. Motivated by this fact, I used stellar kinematic data from Gaia DR3 to revisit constraints on BH natal kicks from accreting and detached BH binaries. I compared the space velocities and Galactic orbits of a sample of 12 BHs in the Galactic disk with well-constrained distances to their local stellar populations. I found that 6 BHs had at least weak evidence for a kick, and that 4 BHs were kinematically hotter than 90% of their local stellar populations, suggesting that they were born with kicks of > 100 km/s. On the other hand, 6 BHs had kinematics typical of their local populations, disfavoring kicks of > 50 km/s. I pointed out that, in particular, V404 Cyg and VFTS 243 have strong independent evidence for being born with very weak kicks. Although uncertainties are still too large to assess whether the BH kick distribution is bimodal, I concluded that the data are consistent with a scenario where some BHs form by direct collapse and receive weak kicks, and others form in supernovae and receive strong kicks.

Read more about this research project in the associated publication here.

Read an Astrobites article about this work here.