Constraining the Mass of a Hypothetical Secondary Black Hole in M87 with the NANOGrav 15-Year Data Set

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Main Authors: Kino, Motoki, Nagashima, Masahiro, Ro, Hyunwook, Cui, Yuzhu, Hada, Kazuhiro, Park, Jongho
Format: Preprint
Published: 2025
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author Kino, Motoki
Nagashima, Masahiro
Ro, Hyunwook
Cui, Yuzhu
Hada, Kazuhiro
Park, Jongho
author_facet Kino, Motoki
Nagashima, Masahiro
Ro, Hyunwook
Cui, Yuzhu
Hada, Kazuhiro
Park, Jongho
contents Galaxy mergers, each hosting a supermassive black hole (SMBH), are thought to form SMBH binaries. Motivated by recent observations from the East Asian VLBI Network (EAVN) showing periodic behavior in the M87 jet, a precession of about 11 years and a transverse oscillation of about 0.9 years, we constrain the mass of a hypothetical secondary black hole orbiting the primary SMBH in M87. To constrain the mass ratio between the primary SMBH ($M_{1}$) and the secondary black hole ($M_{2}$) defined as $q \equiv M_{2}/M_{1} \leq 1$, and the length of the semimajor axis of the binary system ($a$), we impose the following three constraints: (i) the lower limit of $a$, below which the SMBH binary is expected to merge. (ii) the strain amplitude of the gravitational wave background (GWB) at nanohertz frequencies shown in the NANOGrav 15-year dataset. (iii) a finite length of the semimajor axis of $M_{1}$, that can induce periodic behavior in the jet. By combining these constraints, we obtain the allowed parameter space for $q$ and $a$. If either of the EAVN-detected periods ($T$) corresponds to the binary's orbital period, the allowed range of $q$ is $6.9 \times 10^{-3} \le q \le 4.2 \times 10^{-2}$ for $T \approx 11$ years, and $3.7\times 10^{-2} \le q \le 1$ for $T \approx 0.9$ years. VLBI astrometric monitoring of the jet base of M87 is essential to explore the allowed parameter space for $q$ and $a$.
format Preprint
id arxiv_https___arxiv_org_abs_2506_12313
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Constraining the Mass of a Hypothetical Secondary Black Hole in M87 with the NANOGrav 15-Year Data Set
Kino, Motoki
Nagashima, Masahiro
Ro, Hyunwook
Cui, Yuzhu
Hada, Kazuhiro
Park, Jongho
High Energy Astrophysical Phenomena
Astrophysics of Galaxies
General Relativity and Quantum Cosmology
Galaxy mergers, each hosting a supermassive black hole (SMBH), are thought to form SMBH binaries. Motivated by recent observations from the East Asian VLBI Network (EAVN) showing periodic behavior in the M87 jet, a precession of about 11 years and a transverse oscillation of about 0.9 years, we constrain the mass of a hypothetical secondary black hole orbiting the primary SMBH in M87. To constrain the mass ratio between the primary SMBH ($M_{1}$) and the secondary black hole ($M_{2}$) defined as $q \equiv M_{2}/M_{1} \leq 1$, and the length of the semimajor axis of the binary system ($a$), we impose the following three constraints: (i) the lower limit of $a$, below which the SMBH binary is expected to merge. (ii) the strain amplitude of the gravitational wave background (GWB) at nanohertz frequencies shown in the NANOGrav 15-year dataset. (iii) a finite length of the semimajor axis of $M_{1}$, that can induce periodic behavior in the jet. By combining these constraints, we obtain the allowed parameter space for $q$ and $a$. If either of the EAVN-detected periods ($T$) corresponds to the binary's orbital period, the allowed range of $q$ is $6.9 \times 10^{-3} \le q \le 4.2 \times 10^{-2}$ for $T \approx 11$ years, and $3.7\times 10^{-2} \le q \le 1$ for $T \approx 0.9$ years. VLBI astrometric monitoring of the jet base of M87 is essential to explore the allowed parameter space for $q$ and $a$.
title Constraining the Mass of a Hypothetical Secondary Black Hole in M87 with the NANOGrav 15-Year Data Set
topic High Energy Astrophysical Phenomena
Astrophysics of Galaxies
General Relativity and Quantum Cosmology
url https://arxiv.org/abs/2506.12313