A1 Refereed original research article in a scientific journal
The polarisation behaviour of OJ 287 viewed through radio, millimetre, and optical observations between 2015 and 2017
Authors: Jormanainen, J.; Hovatta, T.; Lindfors, E.; Berdyugin, A.; Chamani, W.; Ramazani, V. Fallah; Jermak, H.; Jorstad, S. G.; Lähteenmäki, A.; Mccall, C.; Nilsson, K.; Smith, P.; Steele, I. A.; Tammi, J.; Tornikoski, M.; Wierda, F.
Publisher: EDP Sciences
Publishing place: LES ULIS CEDEX A
Publication year: 2025
Journal: Astronomy and Astrophysics
Journal name in source: Astronomy & Astrophysics
Journal acronym: ASTRON ASTROPHYS
Article number: A206
Volume: 694
Number of pages: 8
ISSN: 0004-6361
eISSN: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202453009
Web address : https://doi.org/10.1051/0004-6361/202453009
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/491324485
OJ 287 is a bright blazar with century-long observations, and one of the strongest candidates to host a supermassive black hole binary. Its polarisation behaviour between 2015 and 2017 (MJD 57300-58000) contains several interesting events that we re-contextualise in this study. We collected optical photometric and polarimetric data from several telescopes and obtained high-cadence light curves from this period. In the radio band, we collected millimetre-wavelength polarisation data from the AMAPOLA programme. We combined them with existing multi-frequency polarimetric radio results and the results of very long-baseline interferometry imaging with the Global mm-VLBI Array at 86 GHz. In December 2015, an optical flare was seen according to the general relativistic binary black hole model. We suggest that the overall activity near the accretion disk and the jet base during this time may be connected to the onset of a new moving component, K, seen in the jet in March 2017. With the additional optical data, we find a fast polarisation angle rotation of similar to 210 degrees coinciding with the December 2015 flare, hinting at a possible link between these events. Based on the 86 GHz images, we calculated a new speed of 0.12 mas/yr for K, which places it inside the core at the time of the 2015 flare. This speed also supports the scenario in which the passage of K through the quasi-stationary feature S1 could have been the trigger for the very high-energy gamma-ray flare of OJ 287 seen in February 2017. With the millimetre-polarisation data, we establish that these bands follow the centimetre-band data but show a difference during the time when K passes through S1. This indicates that the millimetre bands trace substructures of the jet that are still unresolved in the centimetre bands.
Downloadable publication This is an electronic reprint of the original article. |  |
Funding information in the publication:
J.J. was supported by the Academy of Finland projects 320085, 322535, and 345899, as well as by the Alfred Kordelin Foundation. T.H. was supported by Academy of Finland projects 317383, 320085, 322535, and 345899. E.L. was supported by the Academy of Finland projects 317636, 320045 and 346071. We thank Dr. Seiji Kameno for providing the AMAPOLA data and Dr. Alok Gupta for providing the data published in Gupta et al. (2023). This publication makes use of data obtained at Metsähovi Radio Observatory, operated by Aalto University in Finland. The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. The research at Boston University was supported in part by the National Science Foundation grant AST-2108622, and a number of NASA Fermi Guest Investigator grants, the latest is 80NSSC23K1507. This study was based in part on observations conducted using the 1.8 m Perkins Telescope Observatory (PTO) in Arizona, which is owned and operated by Boston University. Data from the Steward Observatory spectropolarimetric monitoring project were used. This program is supported by Fermi Guest Investigator grants NNX08AW56G, NNX09AU10G, NNX12AO93G, and NNX15AU81G.
