High frequency breaks in optical active galactic nuclei power spectral density
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arXiv
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| Format: | Preprint |
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2023
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| _version_ | 1866918044542959616 |
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| author | Yuk, Heechan Dai, Xinyu |
| author_facet | Yuk, Heechan Dai, Xinyu |
| contents | Context. Variability is a ubiquitous feature of active galactic nuclei (AGNs), and the characterisation of the variability is crucial to constrain its physical mechanism and proper applications in AGN studies. The advent of all-sky and high-cadence optical surveys allows more accurate measurements of AGNs variability down to short timescales and direct comparisons with X-ray variability from the same sample of sources. Aims. We aim to analyse the optical power spectral density (PSDs) of AGNs with measured X-ray PSDs. Methods. We use light curves from the All-Sky Automated Survey for SuperNovae (ASAS-SN) and the Transiting Exoplanet Survey Satellite (TESS) and use the Lomb-Scargle periodogram to obtain PSDs. The joint optical PSD is measured over up to six orders of magnitude in frequency space from timescales of minutes to a decade. We fit either a damped random walk (DRW) or a broken power law (BPL) model to constrain the PSD model and break frequency. Results. We find a set of break frequencies ($\lesssim10^{-2}$ day$^{-1}$) from DRW and BPL fits that generally confirm previously reported correlations between break frequencies and the black hole mass. In addition, we find a second set of break frequencies at higher frequencies ($>10^{-2}$ day$^{-1}$). We observe a potential weak correlation between the high-frequency breaks with the X-ray break frequencies and black hole mass. We further explore the dependence of the correlations on other AGN parameters, finding that adding either X-ray, optical, or bolometric luminosity as the third correlation parameter can substantially improve the correlation significances. The newly identified high-frequency optical breaks can constrain different aspects of the physics of active galactic nuclei. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2306_17334 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | High frequency breaks in optical active galactic nuclei power spectral density Yuk, Heechan Dai, Xinyu High Energy Astrophysical Phenomena Astrophysics of Galaxies Context. Variability is a ubiquitous feature of active galactic nuclei (AGNs), and the characterisation of the variability is crucial to constrain its physical mechanism and proper applications in AGN studies. The advent of all-sky and high-cadence optical surveys allows more accurate measurements of AGNs variability down to short timescales and direct comparisons with X-ray variability from the same sample of sources. Aims. We aim to analyse the optical power spectral density (PSDs) of AGNs with measured X-ray PSDs. Methods. We use light curves from the All-Sky Automated Survey for SuperNovae (ASAS-SN) and the Transiting Exoplanet Survey Satellite (TESS) and use the Lomb-Scargle periodogram to obtain PSDs. The joint optical PSD is measured over up to six orders of magnitude in frequency space from timescales of minutes to a decade. We fit either a damped random walk (DRW) or a broken power law (BPL) model to constrain the PSD model and break frequency. Results. We find a set of break frequencies ($\lesssim10^{-2}$ day$^{-1}$) from DRW and BPL fits that generally confirm previously reported correlations between break frequencies and the black hole mass. In addition, we find a second set of break frequencies at higher frequencies ($>10^{-2}$ day$^{-1}$). We observe a potential weak correlation between the high-frequency breaks with the X-ray break frequencies and black hole mass. We further explore the dependence of the correlations on other AGN parameters, finding that adding either X-ray, optical, or bolometric luminosity as the third correlation parameter can substantially improve the correlation significances. The newly identified high-frequency optical breaks can constrain different aspects of the physics of active galactic nuclei. |
| title | High frequency breaks in optical active galactic nuclei power spectral density |
| topic | High Energy Astrophysical Phenomena Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2306.17334 |