A1 Refereed original research article in a scientific journal
A Search for Supermassive Black Hole Binary Candidates in 46 yr Radio Light Curves of 83 Blazars; 
Authors: Molina, B.; Mróz, P.; De la Parra, P. V.; Readhead, A. C. S.; Surti, T.; Aller, M. F.; Scargle, J. D.; Reeves, R. A.; Aller, H.; Begelman, M. C.; Blandford, R. D.; Ding, Y.; Graham, M. J.; Harrison, F.; Hovatta, T.; Liodakis, I.; Lister, M. L.; Max-Moerbeck, W.; Pavlidou, V.; Pearson, T. J.; Ravi, V.; Sullivan, A. G.; Synani, A.; Tassis, K.; Tremblay, S. E.; Zensus, J. A.
Publisher: Institute of Physics Publishing
Publication year: 2026
Journal: Astrophysical Journal
Article number: 72
Volume: 1000
Issue: 1
ISSN: 0004-637X
eISSN: 1538-4357
DOI: https://doi.org/10.3847/1538-4357/ae3141
Publication's open availability at the time of reporting: Open Access
Publication channel's open availability : Open Access publication channel
Web address : https://iopscience.iop.org/article/10.3847/1538-4357/ae3141
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/523517682
Self-archived copy's licence: CC BY
Self-archived copy's version: Publisher`s PDF
The combined University of Michigan Radio Astronomy Observatory and Owens Valley Radio Observatory blazar monitoring programs at 14.5/15 GHz provide uninterrupted light curves of ∼ 46–50 yr duration for 83 blazars, selected from among the brightest and most rapidly flaring blazars north of declination −20°. In a search for supermassive black hole binary (SMBHB) candidates, we carried out tests for periodic variability using generalized Lomb–Scargle (GLS), weighted wavelet-Z, and sine-wave fitting analyses of this sample. We used simulations to test the effects of the power-law spectrum of the power spectral density (PSD) on our findings, and show that the irregular sampling in the observed light curves has very little effect on the GLS spectra. Apparent periodicities and putative harmonics appear in all 83 of the GLS spectra of the blazars in our sample. We tested the reality of these apparent periodicities and harmonics with simulations, and found that in the overwhelming majority of cases, they must be due to the steep slope of the PSD and the random nature of blazar flares, implying that, in general, apparent periodicities and harmonics in blazar light curves observed in any energy band should be treated with great caution. We find one new SMBHB candidate: PKS 1309+1154, which exhibits a 17.9 yr periodicity. The fraction of SMBHB candidates in our sample is 2.4+3.2/-0.8%.
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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 10 yr (2014–2024) in the absence of agency funding for operation of the telescope. Without this private support, this program would have ended in 2016. We also thank all of 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 2006–2016 and NSF grants AST-0808050 and AST-1109911 from 2008–2014. The UMRAO program received support from NSF grants AST-8021250, AST-8301234, AST-8501093, AST-8815678, AST-9120224, AST-9421979, AST-9617032, AST-9900723, AST-0307629, and 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. W.M. acknowledges support from ANID projects Basal FB210003 and FONDECYT 11190853. A.S. and R.B acknowledge support by a grant from the Simons Foundation (00001470,RB,AS). Y.D. and F.A.H. acknowledge support through NASA under contract No. NNG08FD60C. R.R., B.M., and P.V.d.l.P. acknowledge support from ANID Basal AFB-170002, Núcleo Milenio TITANs (NCN2023_002), CATA BASAL FB210003 and UdeC-VRID 2025001479INV. T.H. acknowledges support from the Academy of Finland projects 317383, 320085, 345899, and 362571 and from the European Union ERC-2024-COG—PARTICLES—101169986. I.L. was 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.
