A1 Refereed original research article in a scientific journal
Identifying the Secondary Jet in the RadioAstron Image of OJ 287
Authors: Valtonen, Mauri J.; Dey, Lankeswar; Zola, Staszek; Gupta, Alok C.; Kishore, Shubham; Gopakumar, Achamveedu; Wiita, Paul J.; Gu, Minfeng; Nilsson, Kari; Zhang, Zhongli; Hudec, Rene; Matsumoto, Katsura; Drozdz, Marek; Ogloza, Waldemar; Berdyugin, Andrei V.; Reichart, Daniel E.; Mugrauer, Markus; Pursimo, Tapio; Ciprini, Stefano; Nakaoka, Tatsuya; Uemura, Makoto; Imazawa, Ryo; Zejmo, Michal; Kouprianov, Vladimir V.; Davidson Jr, James W.; Sadun, Alberto; Strobl, Jan; Jelinek, Martin; Susobhanan, Abhimanyu
Publisher: Institute of Physics Publishing
Publication year: 2025
Journal:: Astrophysical Journal
Article number: 110
Volume: 992
Issue: 1
ISSN: 0004-637X
eISSN: 1538-4357
DOI: https://doi.org/10.3847/1538-4357/ae057e
Web address : https://doi.org/10.3847/1538-4357/ae057e
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/504950025
The 136 yr long optical light curve of OJ 287 is explained by a binary black hole model where the secondary is in a 12 yr orbit around the primary. Impacts of the secondary on the accretion disk of the primary generate a series of optical flares that follow a quasi-Keplerian relativistic mathematical model. The orientation of the binary in space is determined from the behavior of the primary jet. Here, we ask how the jet of the secondary black hole projects onto the sky plane. Assuming that the jet is initially perpendicular to the disk, and that it is ballistic, we follow its evolution after the Lorentz transformation to the observer's frame. Since the orbital speed of the secondary is of the order of one-tenth of the speed of light, the result is a change in the jet direction by more than a radian during an orbital cycle. We match the theoretical jet line with the recent 12 mu as resolution RadioAstron map of OJ 287 and determine the only free parameter of the problem, the apparent speed of the jet relative to speed of light. It turns out that the Doppler factor of the jet, delta similar to 5, is much lower than in the primary jet. Besides following a unique shape of the jet path, the secondary jet is also distinguished by a different spectral shape than in the primary jet. The present result on the spectral shape agrees with the huge optical flare of 2021 November 12, also arising from the secondary jet.
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Funding information in the publication:
This work was partly funded by NCN grant No. 2018/29/B/ST9/01793 (S.Z.) and JSPS KAKENHI grant No. 19K03930 (K.M.). This work was partially supported by a program of the Polish Ministry of Science under the title “Regional Excellence Initiative,” project no. RID/SP/0050/2024/1. S.C. acknowledges support by ASI through contract ASI-INFN 2021-43-HH.0 for SSDC, and Instituto Nazionale di Fisica Nucleare (INFN). R.H. acknowledges the EU project H2020 AHEAD2020, grant agreement 871158, and internal CTU grant SGS21/120/OHK3/2T/13. M.F.G. is supported by the National Science Foundation of China (grant 12473019), the National SKA Program of China (grant No. 2022SKA0120102), the Shanghai Pilot Program for Basic Research-Chinese Academy of Science, Shanghai Branch (JCYJ-SHFY-2021-013), and the China Manned Space Project with No. CMS-CSST-2025-A07. Z.Z. is thankful for support from the National Natural Science Foundation of China (grant No. 12233005). M.J.V. acknowledges a grant from the Finnish Society for Sciences and Letters.
