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

Galaxy mergers, each hosting a supermassive black hole (SMBH), are thought to form SMBH binaries. Motivated by recent observations from the East Asian Very Long Baseline Interferometry (VLBI) Network (EAVN) showing periodic behavior in the M87 jet, a precession of about 11 yr and a transverse oscill...

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Main Authors: Motoki Kino, Masahiro Nagashima, Hyunwook Ro, Yuzhu Cui, Kazuhiro Hada, Jongho Park
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:The Astrophysical Journal
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Online Access:https://doi.org/10.3847/1538-4357/adceb6
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author Motoki Kino
Masahiro Nagashima
Hyunwook Ro
Yuzhu Cui
Kazuhiro Hada
Jongho Park
author_facet Motoki Kino
Masahiro Nagashima
Hyunwook Ro
Yuzhu Cui
Kazuhiro Hada
Jongho Park
author_sort Motoki Kino
collection DOAJ
description Galaxy mergers, each hosting a supermassive black hole (SMBH), are thought to form SMBH binaries. Motivated by recent observations from the East Asian Very Long Baseline Interferometry (VLBI) Network (EAVN) showing periodic behavior in the M87 jet, a precession of about 11 yr and a transverse oscillation of about 0.9 yr, 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 ≡ M _2 / M _1 ≤ 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 at nanohertz frequencies shown in the NANOGrav 15 yr data set; and (iii) a finite length of the semimajor axis of M _1 , which 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 × 10 ^−3 ≤ q ≤ 4.2 × 10 ^−2 for T ≈ 11 yr, and 3.7 × 10 ^−2 ≤ q ≤ 1 for T ≈ 0.9 yr. VLBI astrometric monitoring of the jet base of M87 is essential to explore the allowed parameter space for q and a .
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spelling doaj-art-5de59c8cec60439189939f206cf4fb7c2025-08-20T02:02:57ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198614910.3847/1538-4357/adceb6Constraining the Mass of a Hypothetical Secondary Black Hole in M87 with the NANOGrav 15 yr Data SetMotoki Kino0https://orcid.org/0000-0002-2709-7338Masahiro Nagashima1https://orcid.org/0000-0003-2938-7096Hyunwook Ro2https://orcid.org/0000-0002-7322-6436Yuzhu Cui3https://orcid.org/0000-0001-6311-4345Kazuhiro Hada4https://orcid.org/0000-0001-6906-772XJongho Park5https://orcid.org/0000-0001-6558-9053Kogakuin University of Technology & Engineering , Academic Support Center, 2665-1 Nakano-machi, Hachioji, Tokyo 192-0015, Japan ; motoki.kino@gmail.com; National Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, JapanFaculty of Education, Bunkyo University , 3337, Minami-ogishima, Koshigaya, Saitama 343-8511, JapanKorea Astronomy & Space Science Institute , Daedeokdae-ro 776, Yuseong-gu, Daejeon 34055, Republic of KoreaInstitute of Astrophysics, Central China Normal University , Wuhan 430079, People’s Republic of China; Research Center for Astronomical Computing , Zhejiang Lab, Hangzhou 311100, People’s Republic of ChinaGraduate School of Science, Nagoya City University , Yamanohata 1, Mizuho-cho, Mizuho-ku, Nagoya, 467-8501, Aichi, Japan; Mizusawa VLBI Observatory , National Astronomical Observatory of Japan, 2-12 Hoshigaoka-cho, Mizusawa, Oshu, 023-0861, Iwate, JapanSchool of Space Research, Kyung Hee University , 1732, Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 17104, Republic of Korea; Institute of Astronomy and Astrophysics , Academia Sinica, P.O. Box 23-141, Taipei 10617, TaiwanGalaxy mergers, each hosting a supermassive black hole (SMBH), are thought to form SMBH binaries. Motivated by recent observations from the East Asian Very Long Baseline Interferometry (VLBI) Network (EAVN) showing periodic behavior in the M87 jet, a precession of about 11 yr and a transverse oscillation of about 0.9 yr, 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 ≡ M _2 / M _1 ≤ 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 at nanohertz frequencies shown in the NANOGrav 15 yr data set; and (iii) a finite length of the semimajor axis of M _1 , which 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 × 10 ^−3 ≤ q ≤ 4.2 × 10 ^−2 for T ≈ 11 yr, and 3.7 × 10 ^−2 ≤ q ≤ 1 for T ≈ 0.9 yr. VLBI astrometric monitoring of the jet base of M87 is essential to explore the allowed parameter space for q and a .https://doi.org/10.3847/1538-4357/adceb6Active galactic nucleiGravitational wave astronomyRadio interferometrySupermassive black holesVery long baseline interferometry
spellingShingle Motoki Kino
Masahiro Nagashima
Hyunwook Ro
Yuzhu Cui
Kazuhiro Hada
Jongho Park
Constraining the Mass of a Hypothetical Secondary Black Hole in M87 with the NANOGrav 15 yr Data Set
The Astrophysical Journal
Active galactic nuclei
Gravitational wave astronomy
Radio interferometry
Supermassive black holes
Very long baseline interferometry
title Constraining the Mass of a Hypothetical Secondary Black Hole in M87 with the NANOGrav 15 yr Data Set
title_full Constraining the Mass of a Hypothetical Secondary Black Hole in M87 with the NANOGrav 15 yr Data Set
title_fullStr Constraining the Mass of a Hypothetical Secondary Black Hole in M87 with the NANOGrav 15 yr Data Set
title_full_unstemmed Constraining the Mass of a Hypothetical Secondary Black Hole in M87 with the NANOGrav 15 yr Data Set
title_short Constraining the Mass of a Hypothetical Secondary Black Hole in M87 with the NANOGrav 15 yr Data Set
title_sort constraining the mass of a hypothetical secondary black hole in m87 with the nanograv 15 yr data set
topic Active galactic nuclei
Gravitational wave astronomy
Radio interferometry
Supermassive black holes
Very long baseline interferometry
url https://doi.org/10.3847/1538-4357/adceb6
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