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| Format: | Preprint |
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2025
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| Online Access: | https://arxiv.org/abs/2511.09304 |
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| _version_ | 1866911261896212480 |
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| author | XueGuang, Zhang |
| author_facet | XueGuang, Zhang |
| contents | In this manuscript, variations in optical spectral index $α_{5100}$ 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 $α_{5100}$ can be expected. First, if a BLAGN harbours a central sub-pc BBH, the expected unique variability in $α_{5100}$ should lead the BLAGN to be an outlier in the space of $α_{5100}$ versus continuum luminosity $L_{5100}$ determined from normal BLAGN. Second, BLAGN harbouring central sub-pc BBHs could lead to periodic variations in $α_{5100}$. 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 $α_{5100}$ 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 $α_{5100}$ 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. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2511_09304 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Variability of optical spectral index to support a central sub-parsec binary black hole system in quasar SDSS J001224-102226.51 XueGuang, Zhang Astrophysics of Galaxies High Energy Astrophysical Phenomena In this manuscript, variations in optical spectral index $α_{5100}$ 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 $α_{5100}$ can be expected. First, if a BLAGN harbours a central sub-pc BBH, the expected unique variability in $α_{5100}$ should lead the BLAGN to be an outlier in the space of $α_{5100}$ versus continuum luminosity $L_{5100}$ determined from normal BLAGN. Second, BLAGN harbouring central sub-pc BBHs could lead to periodic variations in $α_{5100}$. 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 $α_{5100}$ 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 $α_{5100}$ 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. |
| title | Variability of optical spectral index to support a central sub-parsec binary black hole system in quasar SDSS J001224-102226.51 |
| topic | Astrophysics of Galaxies High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2511.09304 |