A1 Refereed original research article in a scientific journal
PKS J0805-0111: A Second Owens Valley Radio Observatory Blazar Showing Highly Significant Sinusoidal Radio Variability—The Tip of the Iceberg
Authors: de la Parra, P. V.; Kiehlmann, S.; Mroz, P.; Readhead, A. C. S.; Synani, A.; Begelman, M. C.; Blandford, R. D.; Ding, Y.; Harrison, F.; Liodakis, I.; Max-Moerbeck, W.; Pavlidou, V.; Reeves, R.; Vallisneri, M.; Aller, M. F.; Graham, M. J.; Hovatta, T.; Lawrence, C. R.; Lazio, T. J. W.; Mahabal, A. A.; Molina, B.; O'Neill, S.; Pearson, T. J.; Ravi, V.; Tassis, K.; Zensus, J. A.
Publisher: American Astronomical Society
Publishing place: BRISTOL
Publication year: 2025
Journal:Astrophysical Journal
Journal name in sourceThe Astrophysical Journal
Journal acronym: ASTROPHYS J
Article number: 191
Volume: 987
Issue: 2
Number of pages: 11
ISSN: 0004-637X
eISSN: 1538-4357
DOI: https://doi.org/10.3847/1538-4357/addc60
Web address : https://doi.org/10.3847/1538-4357/addc60
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/499430213
Owens Valley Radio Observatory observations of the supermassive black hole binary (SMBHB) candidate PKS 2131-021 revealed, for the first time, six likely characteristics of the phenomenology exhibited by SMBHBs in blazars, of which the most unexpected and critical is sinusoidal flux density variations. We have now identified a second blazar, PKS J0805-0111, showing similar variations, with a period of 1.422 +/- 0.005 yr in the rest frame of the z = 1.388 object. PKS J0805-0111 displays five of the six characteristics observed in PKS 2131-021. To estimate the significance of the sinusoidal variations, we generate 106 simulated light curves that reproduce the radio variability characteristics of PKS J0805-0111 and show that the global probability that the periodicity we detect is due to the red-noise tail of the power spectral density is p = 6.7 x 10-5 (3.82 sigma). This shows that PKS 2131-021 is not a unique case. The discovery of these two objects in a sample of 1158 blazars allows us to reject, at a p-value similar to 0.003, the null hypothesis that the sinusoidal variations in these two blazars are all due to a red-noise process. We estimate that the number of SMBHB candidates among blazars is similar to 1 in 100.
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Funding information in the publication:
This work is supported by NSF grants AST2407603 and AST2407604. We thank the California Institute of Technology and the Max Planck Institute for Radio Astronomy for supporting the OVRO 40 m program under extremely difficult circumstances over the last eight years in the absence of agency funding. Without this private support this paper would not have been written. We also thank all the volunteers who have enabled this work to be carried out. Prior to 2016, the OVRO program was supported by NASA grants NNG06GG1G, NNX08AW31G, NNX11A043G, and NNX13AQ89G from 2006 to 2016 and NSF grants AST-0808050, and AST-1109911 from 2008 to 2014. The UMRAO program received support from NSF grants AST-8021250, AST-8301234, AST-8501093, AST-8815678, AST-9120224, AST-9421979, AST-9900723, AST-0307629, AST-0607523, and earlier NSF awards, and from NASA grants NNX09AU16G, NNX10AP16G, NNX11AO13G, and NNX13AP18G. Additional funding for the operation of UMRAO was provided by the University of Michigan. The NANOGrav project receives support from National Science Foundation (NSF) Physics Frontier Center award number 1430284. T.H. was supported by the Academy of Finland projects 317383, 320085, 322535, and 345899. S.K. and K.T. acknowledge support from the European Research Council (ERC) under the European Union's Horizon 2.20 research and innovation program under grant agreement No. 771282. I.L. and S.K. were funded by the European Union ERC-2022-STG-BOOTES-101076343. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council Executive Agency. Neither the European Union nor the granting authority can be held responsible for them. W.M. acknowledges support by the ANID BASAL project FB210003 and FONDECYT 11190853. R.R. and B.M. and P.V.d.l.P. acknowledge support from ANID Basal AFB-170002, from Nucleo Milenio TITANs (NCN2023_002), and CATA BASAL FB210003. P.V.d.l.P. also acknowledges support by the National Agency for Research and Development (ANID)/Scholarship Program/Doctorado Nacional/2023-21232103. M.V. performed part of this work at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). V.P. acknowledges support from the Foundation of Research and Technology-Hellas Synergy Grants Program through project MagMASim, jointly implemented by the Institute of Astrophysics and the Institute of Applied and Computational Mathematics and by the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the "First Call for H.F.R.I. Research Projects to support Faculty members and Researchers and the procurement of high-cost research equipment grant" (Project 1552 CIRCE). K.T. acknowledges support from the Foundation of Research and Technology-Hellas Synergy Grants Program through project POLAR, jointly implemented by the Institute of Astrophysics and the Institute of Computer Science. I.L. was supported by the NASA Postdoctoral Program at the Marshall Space Flight Center, administered by Oak Ridge Associated Universities under contract with NASA. The authors acknowledge the Kultrun Astronomy Hybrid Cluster (projects Conicyt Programa de Astronomia FondoQuimal QUIMAL170001, QUIMAL220002 and Conicyt PIA ACT172033) for providing HPC resources that have contributed to the research results reported in this paper.
