The effect of pair-instability mass loss on black-hole mergers

Abstract

Context. Mergers of two stellar origin black holes are a prime source of gravitational waves and are under intensive investigation. One crucial ingredient in their modeling has been neglected: pair-instability pulsation supernovae with associated severe mass loss may suppress the formation of massive black holes, decreasing black hole merger rates for the highest black hole masses. Aims. We demonstrate the effects of pair-instability pulsation supernovae on merger rate and mass using populations of double black hole binaries formed through the isolated binary classical evolution channel. Methods. The mass loss from pair-instability pulsation supernova is estimated based on existing hydrodynamical calculations. This mass loss is incorporated into the StarTrack population synthesis code. StarTrack is used to generate double black hole populations with and without pair-instability pulsation supernova mass loss. Results. The mass loss associated with pair-instability pulsation supernovae limits the Population I/II stellar-origin black hole mass to 50 M ⊙ , in tension with earlier predictions that the maximum black hole mass could be as high as 100 M ⊙ . In our model, neutron stars form with mass 1-2 M ⊙ , then we encounter the first mass gap at 2-5 M ⊙ with an absence of compact objects due to rapid supernova explosions, followed by the formation of black holes with mass 5-50 M ⊙ , with a second mass gap at 50-135 M ⊙ created by pairinstability pulsation supernovae and by pair-instability supernovae. Finally, black holes having masses above 135 M ⊙ may potentially form to arbitrarily high mass limited only by the extent of the initial mass function and the strength of stellar winds. Suppression of double black hole merger rates by pair-instability pulsation supernovae is negligible for our evolutionary channel. Our standard evolutionary model with the inclusion of pair-instability pulsation supernovae and pair-instability supernovae is fully consistent with the LIGO observations of black hole mergers: GW150914, GW151226, and LVT151012. The LIGO results are inconsistent with high ( 400 km s −1 ) BH natal kicks. We predict the detection of several, and up to as many as ∼ 60, BH-BH mergers with a total mass of 10-150 M ⊙ (most likely range: 20-80 M ⊙ ) in the forthcoming ∼ 60 effective days of the LIGO O2 observations, assuming the detectors reach the optimistic target O2 sensitivity. Conclusions.

Crossing the Eddington Limit: Examining Disk Spectra at High Accretion Rates

“…This mass gap covers the range of ∼60-130 M e over which it is thought that stellar black holes do not form due to disruption by pair instability supernovae (Marchant et al 2016). Furthermore, black holes below the mass gap may be limited to <50 M e by severe mass loss in pulsation pair instability supernovae (Belczynski et al 2016). Also, the collapse of massive stars is only thought to produce black hole spins of -< a 0.75 0.9 (Gammie et al 2004).…”

Modeling Dense Star Clusters in the Milky Way and Beyond with the CMC Cluster Catalog

“…As discussed in Spera et al (2019), massive stellar mergers occurring through binary evolution may have important consequences for the formation of massive BHs, specifically BHs lying within the so-called upper mass-gap expected from (pulsational) pair instability SNe (e.g., Belczynski et al 2016b;Woosley 2016;Spera & Mapelli 2017). In principle, dynamically-mediated stellar collisions of massive stars in GCs may have similar implications for BH formation.…”

“…• Black hole formation: we assume BHs are formed with mass fallback and calculate BH natal kicks by sampling from the same distribution as CCSN NSs but with BH kicks reduced in magnitude according to the fractional mass of fallback material (see Fryer et al 2012;Morscher et al 2015, for further details). We also implement prescriptions to treat pulsational-pair instabilities and pair-instability supernovae as described in Belczynski et al (2016b).…”

Parametrized ringdown spin expansion coefficients: A data-analysis framework for black-hole spectroscopy with multiple events

“…The 2N masses of the binary components are drawn from a log-flat distribution between [5,95]M for stellar-origin BHs, and from a uniform distribution within [10 6 , 10 7 ]M for massive BHs. For stellar-origin BHs we also require that m 1 + m 2 < 100M [93,94]. In both mass ranges the spins are sampled from a uniform distribution ∈ [−1, 1].…”