2023/06/29 by Heechan Yuk, Xinyu Dai, Yuk, Heechan +1
Mathematics · Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #High Energy Astrophysical Phenomena (astro-ph.HE) #Statistical and numerical algorithms
paper · pdf · doi:10.48550/arxiv.2306.17334
openalex publication_date 2023/06/29 · openalex created_date 2023/07/04 · openalex updated_date 2026/07/28
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.