Gravitational waves from an SMBH binary in M87

Abstract

In this paper, we study gravitational-wave (GW) emission from a hypothetical supermassive black-hole (SMBH) binary at the center of M87. The existence of a SMBH other than that usually identified with the central AGN is a possible explanation for the observed displacement ($\sim O(1)\mathrm{pc}$) between the AGN and the galactic centroid, and it is reasonable to assume consid- ering the evolution of SMBHs through galaxy mergers. Because the period of the binary and the resulting GWs is much longer than the observational time span, we calculate the variation of the GW amplitude, rather than the amplitude itself. We investigate the dependence on the orbital elements and the second BH mass taking the observational constraints into account. The frequency of the GWs is too low to be detected with the conventional pulsar timing array and we propose a new method to detect such low-frequency GWs with the distribution func- tion of pulsar spin-down rates. Although the GWs from a SMBH binary which explains the observed displacement is extremely hard to be detected even with the new method, GWs are still a useful way to probe the M87 center.

5 pages, 6 figures. Accepted for Publications of the Astronomical Society of Japan

References in corpus (7)

• The ATNF Pulsar Catalogue
• The stochastic gravitational-wave background from massive black hole binary systems: implications for observations with Pulsar Timing Arrays
• A Displaced Supermassive Black Hole in M87
• Recoiling Supermassive Black Holes: a search in the Nearby Universe
• Gravitational-Wave Detection and Astrophysics with Pulsar Timing Arrays
• Gravitational wave astronomy with the SKA
• A Cosmic Census of Radio Pulsars with the SKA

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• Detailed study of detection method for ultra-low-frequency gravitational waves with pulsar spin-down rate statistics
• Constraints on ultra-low-frequency gravitational waves with statistics of pulsar spin-down rates II: Mann-Whitney U test
• Constraints on ultra-low-frequency gravitational waves from an eccentric supermassive black hole binary
• SKA-Japan Pulsar Science with the Square Kilometre Array