GW190521: A Binary Black Hole Merger with a Total Mass of 150  M⊙

Abstract

On May 21, 2019 at 03:02:29 UTC Advanced LIGO and Advanced Virgo observed a short duration gravitational-wave signal, GW190521, with a three-detector network signal-to-noise ratio of 14.7, and an estimated false-alarm rate of 1 in 4900 yr using a search sensitive to generic transients. If GW190521 is from a quasicircular binary inspiral, then the detected signal is consistent with the merger of two black holes with masses of 85 þ21 −14 M ⊙ and 66 þ17 −18 M ⊙ (90% credible intervals). We infer that the primary black hole mass lies within the gap produced by (pulsational) pair-instability supernova processes, with only a 0.32% probability of being below 65 M ⊙. We calculate the mass of the remnant to be 142 þ28 −16 M ⊙ , which can be considered an intermediate mass black hole (IMBH). The luminosity distance of the source is 5.3 þ2.4 −2.6 Gpc, corresponding to a redshift of 0.82 þ0.28 −0.34. The inferred rate of mergers similar to GW190521 is 0.13 þ0.30 −0.11 Gpc −3 yr −1 .

Properties and Astrophysical Implications of the 150 M⊙ Binary Black Hole Merger GW190521

“…The NRSurPHM waveform model is most faithful to NR simulations in the parameter range relevant for GW190521 (Varma et al 2019). Therefore, the inferred source parameters quoted in this paper and in Abbott et al (2020b) were obtained with the NRSurPHM model unless otherwise noted. In this section we also present results from the PhenomPHM and SEOBNRPHM models to check for systematic differences between waveform models.…”

“…We describe the detection of GW190521 in a companion paper (Abbott et al 2020b), where we detail the circumstances of the observation and the detection significance using three different search pipelines. The search results are consistent with a coherent astrophysical signal and inconsistent with an instrumental noise origin for the event.…”

“…Spins.-Due to its high total mass, GW190521 is the shortestduration signal (approximately 0.1 s) recorded so far in the LIGO and Virgo detectors. With only around four cycles (two orbits) in the frequency band 30-80 Hz (Abbott et al 2020b), information about spin evolution during the coalescence is limited. Still, analyses of GW190521 indicate that GW signal models including effects of spin-orbit precession are mildly preferred over those that omit such effects (i.e., allow only spins aligned with the orbital axis), with a -Bayes factor of 1.06±0.06 for the NRSurPHM model allowing generic BH spins versus limiting the effects of spin to the aligned components.…”

“…The gravitational-wave (GW) signal GW190521 (Abbott et al 2020b(Abbott et al , 2019b was observed by the Advanced LIGO (Aasi et al 2015) and Advanced Virgo (Acernese et al 2015) detectors during their third observing run (O3). The event was found with four different search pipelines, both at low latency and offline with improved background estimation; an offline search sensitive to generic transients found GW190521 with a three-detector network signal-to-noise ratio (S/N) of 14.7 and an estimated false-alarm rate of 1 in 4900 yr (Abbott et al 2020b). Another candidate GW signal was reported later on the same day (Abbott et al 2019c).…”

“…Under that interpretation, we find that the observed signal, including its frequency evolution, is entirely consistent both with three different waveform models derived from analytical and/or numerical solutions of general relativity (GR) and with direct comparisons to numerical relativity (NR) solutions. Therefore, most of the discussion in this paper and in Abbott et al (2020b) proceeds under that assumption, including our inferences on the inferred masses and spins and on the effect of including higher-order multipoles in the waveform models. However, as discussed below, other interpretations are possible, adding to the exceptional nature of this event.…”