GW190521 may be an intermediate mass ratio inspiral

Alexander H. Nitz; Collin D. Capano

doi:10.3847/2041-8213/abccc5

paper

GW190521 may be an intermediate mass ratio inspiral

arXiv:2010.12558 · doi:10.3847/2041-8213/abccc5

Abstract

GW190521 is the first confident observation of a binary black hole merger with total mass $M > 100 M_{⊙}$ . Given the lack of observational constraints at these masses, we analyze GW190521 considering two different priors for the binary's masses: uniform in mass ratio and source-frame total mass, and uniform in source-frame component masses. For the uniform in mass-ratio prior, we find that the component masses are $m_{1}^{src} = 16 8_{- 61}^{+ 15} M_{⊙}$ and $m_{2}^{src} = 1 6_{- 3}^{+ 33} M_{⊙}$ . The uniform in component-mass prior yields a bimodal posterior distribution. There is a low-mass-ratio mode ( $q < 4$ ) with $m_{1}^{src} = 10 0_{- 18}^{+ 17} M_{⊙}$ and $m_{2}^{src} = 5 7_{- 16}^{+ 17} M_{⊙}$ and a high-mass-ratio mode ( $q \geq 4$ ) with $m_{1}^{src} = 16 6_{- 35}^{+ 16} M_{⊙}$ and $m_{2}^{src} = 1 6_{- 3}^{+ 14} M_{⊙}$ . Although the two modes have nearly equal posterior probability, the maximum-likelihood parameters are in the high-mass ratio mode, with $m_{1}^{src} = 171 M_{⊙}$ and $m_{2}^{src} = 16 M_{⊙}$ , and a signal-to-noise ratio of $16$ . These results are consistent with the proposed "mass gap" produced by pair-instability in supernova. Our results differ from those published in Abbott et al. (2020b). We find that a combination of the prior used and the constraints applied may have prevented that analysis from sampling the high-mass-ratio mode. An accretion flare in AGN J124942.3+344929 was observed in possible coincidence with GW190521 by the Zwicky Transient Facility (ZTF). We report parameters assuming a common origin; however, the spatial agreement of GW190521 and the EM flare alone does not provide convincing evidence for the association ( $ln B ≳ - 4$ ).

9 pages, 5 figures, 1 table, corresponding data release at http://github.com/gwastro/gw190521, updated to match version accepted by ApJL

GW190521 may be an intermediate mass ratio inspiral

Abstract

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