Eric Thrane (Monash University & OzGrav)

Eric Thrane Colloquium: Dispatches from the black hole mass gaps: recent results from LIGO-Virgo

Remotely Hosted

Abstract

Conventional wisdom has it that the masses of stellar black holes are bounded below and above by gaps. The hypothesised low-mass gap, between ∼2.5 − 5 solar masses, is a prediction of supernovae physics. This gap separates neutron stars from the lightest black holes observed in Galactic X-ray binaries. The high-mass gap, between ∼50 − 120 solar masses, is predicted to occur due to the onset of pair-instability supernovae, which disrupt the stars that would otherwise populate this range of masses. However, recent results from the LIGO-Virgo Collaborations hint that reality is more complicated. The detection of GW190814, sourced from the coalescence of a 23 solar mass black hole with a 2.6 solar mass compact object, illustrates that compact objects exist in the purported low-mass gap. Meanwhile, claims of an electromagnetic counterpart to the binary black hole merger S190521g hint at > 75 solar mass black holes in the high-mass gap. In this talk, I review what we have learned about black holes from gravitational-wave astronomy, I discuss some of the challenges understanding the origin of GW190814, and I highlight how upcoming LIGO-Virgo results will shed new light on the properties of compact binaries.