PKS 2131−021-Discovery of Strong Coherent Sinusoidal Variations from Radio to Optical Frequencies: Compelling Evidence for a Blazar Supermassive Black Hole Binary
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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en
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22
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Astrophysical Journal, Volume 985, issue 1
Abstract
Haystack and Owens Valley Radio Observatory observations recently revealed strong, intermittent, sinusoidal total flux-density variations that maintained their coherence between 1975 and 2021 in the blazar PKS 2131−021 (z = 1.283). This was interpreted as possible evidence of a supermassive black hole binary (SMBHB). Extended observations through 2023 show a coherence over 47.9 yr, with an observed period P15 GHz = (1739.8 ± 17.4) days. We reject, with p-value = 2.09 × 10−7, the hypothesis that the variations are due to random fluctuations in the red noise tail of the power spectral density. There is clearly a physical phenomenon in PKS 2131−021 producing coherent sinusoidal flux-density variations. We find the coherent sinusoidal intensity variations extend from below 2.7 GHz to optical frequencies, from which we derive an observed period Poptical = (1764 ± 36) days. Across this broad frequency range, there is a smoothly varying monotonic phase shift in the sinusoidal variations with frequency. Hints of periodic variations are also observed at γ-ray energies. The importance of well-vetted SMBHB candidates to searches for gravitational waves is pointed out. We estimate the fraction of blazars that are SMBHB candidates to be >1 in 100. Thus, monitoring programs covering tens of thousands of blazars could discover hundreds of SMBHB candidates.Description
Publisher Copyright: © 2025. The Author(s).
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Kiehlmann, S, de la Parra, P V, Sullivan, A G, Synani, A, Liodakis, I, Mróz, P, Næss, S K, Readhead, A C S, Begelman, M C, Blandford, R D, Chatziioannou, K, Ding, Y, Graham, M J, Harrison, F, Homan, D C, Hovatta, T, Kulkarni, S R, Lister, M L, Maiolino, R, Max-Moerbeck, W, Molina, B, O’Dea, C P, Pavlidou, V, Pearson, T J, Aller, M F, Lawrence, C R, Lazio, T J W, O’Neill, S, Prince, T A, Ravi, V, Reeves, R A, Tassis, K, Vallisneri, M & Zensus, J A 2025, 'PKS 2131−021-Discovery of Strong Coherent Sinusoidal Variations from Radio to Optical Frequencies: Compelling Evidence for a Blazar Supermassive Black Hole Binary', Astrophysical Journal, vol. 985, no. 1, 59. https://doi.org/10.3847/1538-4357/adc567