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., Vignali, C., Ambrosino, F., et al. (2020). Unveiling Sub-Pc supermassive black hole binary candidates in active galactic nuclei. THE ASTROPHYSICAL JOURNAL, 902(1), 10.
|Citazione:||Serafinelli, R., Severgnini, P., Braito, V., Ceca, R., Vignali, C., Ambrosino, F., et al. (2020). Unveiling Sub-Pc supermassive black hole binary candidates in active galactic nuclei. THE ASTROPHYSICAL JOURNAL, 902(1), 10.|
|Tipo:||Articolo in rivista - Articolo scientifico|
|Carattere della pubblicazione:||Scientifica|
|Presenza di un coautore afferente ad Istituzioni straniere:||Si|
|Titolo:||Unveiling Sub-Pc supermassive black hole binary candidates in active galactic nuclei|
|Autori:||Serafinelli, R; Severgnini, P; Braito, V; Ceca, R; Vignali, C; Ambrosino, F; Cicone, C; Zaino, A; Dotti, M; Sesana, A; Gianolli, V; Ballo, L; La Parola, V; Matzeu, G|
|Data di pubblicazione:||2020|
|Rivista:||THE ASTROPHYSICAL JOURNAL|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.3847/1538-4357/abb3c3|
|Appare nelle tipologie:||01 - Articolo su rivista|