2025/11/12 by XueGuang, Zhang
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #High Energy Astrophysical Phenomena (astro-ph.HE)
paper · pdf · doi:10.48550/arxiv.2511.09304
openalex publication_date 2025/11/12 · openalex created_date 2025/11/14 · openalex updated_date 2026/07/28
In this manuscript, variations in optical spectral index α5100 are applied for detecting central sub-parsec binary black hole systems (sub-pc BBHs) in broad line active galactic nuclei (BLAGN), due to apparent effects of obscurations on central two BH accreting systems. For sub-pc BBHs in BLAGN, two main characteristics on α5100 can be expected. First, if a BLAGN harbours a central sub-pc BBH, the expected unique variability in α5100 should lead the BLAGN to be an outlier in the space of α5100 versus continuum luminosity L5100 determined from normal BLAGN. Second, BLAGN harbouring central sub-pc BBHs could lead to periodic variations in α5100. Here, after checking the two-epoch SDSS spectra of quasar SDSS J0012-1022 reported as a candidate of sub-pc BBH by large velocity offset between narrow and broad Balmer emission lines, unique variability of α5100 can be explained by effects of obscurations related to an assumed central sub-pc BBH. In the near future, to detect and report periodic variations of α5100 for sub-pc BBHs in BLAGN should be our main objective. The results provide a new method by applications of properties of optical continuum emissions for detecting sub-pc BBHs in BLAGN.