Observing Intermediate-mass Black Holes and the Upper Stellar-mass gap with LIGO and Virgo

Using ground-based gravitational-wave detectors, we probe the mass function of intermediate-mass black holes (IMBHs) wherein we also include BHs in the upper mass gap at similar to 60-130 M-circle dot. Employing the projected sensitivity of the upcoming LIGO and Virgo fourth observing run (O4), we perform Bayesian analysis on quasi-circular nonprecessing, spinning IMBH binaries (IMBHBs) with total masses 50-500 M-circle dot, mass ratios 1.25, 4, and 10, and dimensionless spins up to 0.95, and estimate the precision with which the source-frame parameters can be measured. We find that, at 2 sigma, the mass of the heavier component of IMBHBs can be constrained with an uncertainty of similar to 10%-40% at a signal-to-noise ratio of 20. Focusing on the stellar-mass gap with new tabulations of , the C-12(alpha, gamma)O-16 reaction rate and its uncertainties, we evolve massive helium core stars using MESA to establish the lower and upper edges of the mass gap as similar or equal to 59(-13)( )(+34)M(circle dot )and similar or equal to 139(-14)(+30) M(circle dot )respectively, where the error bars give the mass range that follows from the +/- 3 sigma uncertainty in the C-12(alpha, gamma)O-1(6) nuclear reaction rate. We find that high resolution of the tabulated reaction rate and fine temporal resolution are necessary to resolve the peak of the BH mass spectrum. We then study IMBHBs with components lying in the mass gap and show that the O4 run will be able to robustly identify most such systems. Finally, we reanalyze GW190521 with a state-of-the-art aligned-spin waveform model, finding that the primary mass lies in the mass gap with 90% credibility.

Automated summary

The study utilizes ground-based gravitational-wave detectors to probe the mass function of intermediate-mass black holes. Bayesian analysis is performed on IMBHBs with projected sensitivity of upcoming LIGO and Virgo observing run, revealing the precision of measuring source-frame parameters. High resolution of reaction rate and fine temporal resolution are necessary for resolving the peak of the BH mass spectrum.