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#### Observing intermediate-mass black holes and the upper--stellar-mass gap with LIGO and Virgo

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2105.06366.pdf

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Mehta_2022_ApJ_924_39.pdf

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##### Citation

Mehta, A. K., Buonanno, A., Gair, J., Miller, M. C., Farag, E., deBoer, R. J., et al. (2022).
Observing intermediate-mass black holes and the upper--stellar-mass gap with LIGO and Virgo.* The Astrophysical
Journal,* *924*(1): 39. doi:10.3847/1538-4357/ac3130.

Cite as: https://hdl.handle.net/21.11116/0000-0009-CB7D-7

##### Abstract

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 $\sim 60-130~M_\odot$. Employing the projected sensitivity of

the upcoming LIGO and Virgo fourth observing (O4) run, we perform Bayesian

analysis on quasi-circular non-precessing, spinning IMBH binaries (IMBHBs) with

total masses $50\mbox{--} 500\, M_\odot$, 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

$\sim 10-40\%$ at a signal-to-noise ratio of $20$. Focusing on the stellar-mass

gap with new tabulations of the $^{12}\text{C}(\alpha, \gamma)^{16} \text{O}$

reaction rate and its uncertanties, we evolve massive helium core stars using

\MESA\, to establish the lower and upper edge of the mass gap as

$\simeq$\,59$^{+34}_{-13}$\,$M_{\odot}$ and

$\simeq$\,139$^{+30}_{-14}$\,$M_{\odot}$ respectively, where the error bars

give the mass range that follows from the $\pm 3\sigma$ uncertainty in the

$^{12}\text{C}(\alpha, \gamma) ^{16} \text{O}$ 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 re-analyse

GW190521 with a state-of-the-art aligned-spin waveform model, finding that the

primary mass lies in the mass gap with 90\% credibility.

of intermediate-mass black holes (IMBHs) wherein we also include BHs in the

upper mass gap $\sim 60-130~M_\odot$. Employing the projected sensitivity of

the upcoming LIGO and Virgo fourth observing (O4) run, we perform Bayesian

analysis on quasi-circular non-precessing, spinning IMBH binaries (IMBHBs) with

total masses $50\mbox{--} 500\, M_\odot$, 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

$\sim 10-40\%$ at a signal-to-noise ratio of $20$. Focusing on the stellar-mass

gap with new tabulations of the $^{12}\text{C}(\alpha, \gamma)^{16} \text{O}$

reaction rate and its uncertanties, we evolve massive helium core stars using

\MESA\, to establish the lower and upper edge of the mass gap as

$\simeq$\,59$^{+34}_{-13}$\,$M_{\odot}$ and

$\simeq$\,139$^{+30}_{-14}$\,$M_{\odot}$ respectively, where the error bars

give the mass range that follows from the $\pm 3\sigma$ uncertainty in the

$^{12}\text{C}(\alpha, \gamma) ^{16} \text{O}$ 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 re-analyse

GW190521 with a state-of-the-art aligned-spin waveform model, finding that the

primary mass lies in the mass gap with 90\% credibility.