The elusive supermassive black hole binaries (SMBHBs) are thought to be the penultimate stage of galaxy mergers, preceding a final coalescence phase. SMBHBs are sources of continuous gravitational waves, possibly detectable by pulsar timing arrays; the identification of candidates could help in performing targeted gravitational wave searches. Due to SMBHBs’ origin in the innermost parts of active galactic nuclei (AGN), X-rays are a promising tool for unveiling their presence, by means of either double Fe Kα emission lines or periodicity in their light curve. Here we report on a new method for selecting SMBHBs by means of the presence of a periodic signal in their Swift Burst Alert Telescope (BAT) 105 month light curves. Our technique is based on Fisher’s exact g-test and takes into account the possible presence of colored noise. Among the 553 AGN selected for our investigation, only the Seyfert 1.5 galaxy Mrk 915 emerges as a candidate SMBHB; from subsequent analysis of its light curve we find a period P0 = 35 ± 2 months, and the null hypothesis is rejected at the 3.7σ confidence level. We also present a detailed analysis of the BAT light curve of the only previously X-ray-selected binary candidate source in the literature, the Seyfert 2 galaxy MCG+11-11-032. We find P0 = 26.3 ± 0.6 months, consistent with the one inferred from previously reported double Fe Kα emission lines.

Serafinelli R., Severgnini P., Braito V., Ceca R.D., Vignali C., Ambrosino F., et al. (2020). Unveiling Sub-Pc supermassive black hole binary candidates in active galactic nuclei. THE ASTROPHYSICAL JOURNAL, 902(1), 1-11 [10.3847/1538-4357/abb3c3].

Unveiling Sub-Pc supermassive black hole binary candidates in active galactic nuclei

Vignali C.
Membro del Collaboration Group
;
2020

Abstract

The elusive supermassive black hole binaries (SMBHBs) are thought to be the penultimate stage of galaxy mergers, preceding a final coalescence phase. SMBHBs are sources of continuous gravitational waves, possibly detectable by pulsar timing arrays; the identification of candidates could help in performing targeted gravitational wave searches. Due to SMBHBs’ origin in the innermost parts of active galactic nuclei (AGN), X-rays are a promising tool for unveiling their presence, by means of either double Fe Kα emission lines or periodicity in their light curve. Here we report on a new method for selecting SMBHBs by means of the presence of a periodic signal in their Swift Burst Alert Telescope (BAT) 105 month light curves. Our technique is based on Fisher’s exact g-test and takes into account the possible presence of colored noise. Among the 553 AGN selected for our investigation, only the Seyfert 1.5 galaxy Mrk 915 emerges as a candidate SMBHB; from subsequent analysis of its light curve we find a period P0 = 35 ± 2 months, and the null hypothesis is rejected at the 3.7σ confidence level. We also present a detailed analysis of the BAT light curve of the only previously X-ray-selected binary candidate source in the literature, the Seyfert 2 galaxy MCG+11-11-032. We find P0 = 26.3 ± 0.6 months, consistent with the one inferred from previously reported double Fe Kα emission lines.
2020
Serafinelli R., Severgnini P., Braito V., Ceca R.D., Vignali C., Ambrosino F., et al. (2020). Unveiling Sub-Pc supermassive black hole binary candidates in active galactic nuclei. THE ASTROPHYSICAL JOURNAL, 902(1), 1-11 [10.3847/1538-4357/abb3c3].
Serafinelli R.; Severgnini P.; Braito V.; Ceca R.D.; Vignali C.; Ambrosino F.; Cicone C.; Zaino A.; Dotti M.; Sesana A.; Gianolli V.E.; Ballo L.; La P...espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/808825
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