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American Astronomical Society, Astrophysical Journal, 1(929), p. 19, 2022

DOI: 10.3847/1538-4357/ac4e84

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Accretion Disk Size Measurements of Active Galactic Nuclei Monitored by the Zwicky Transient Facility

Journal article published in 2022 by Wei-Jian Guo, Yan-Rong Li ORCID, Zhi-Xiang Zhang ORCID, Luis C. Ho ORCID, Jian-Min Wang ORCID
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Preprint: archiving forbidden
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Postprint: archiving forbidden
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Published version: archiving allowed
Data provided by SHERPA/RoMEO

Abstract

Abstract We compile a sample of 92 active galactic nuclei (AGNs) at z < 0.75 with gri photometric light curves from the archival data of the Zwicky Transient Facility and measure the accretion disk sizes via continuum reverberation mapping. We employ Monte Carlo simulation tests to assess the influences of data sampling and broad emission lines and select out the sample with adequately high sampling cadences (3 days apart in average) and minimum contaminations of broad emission lines. The interband time delays of individual AGNs are calculated using the interpolated cross-correlation function, and then these delays are fitted with a generalized accretion disk model, in which interband time delays are a power function of wavelength, black hole mass, and luminosity. A Markov Chain Monte Carlo method is adopted to determine the best parameter values. Overall the interband time delays can be fitted with the τ ∝ λ 4/3 relation as predicted from a steady-state, optically thick, geometrically thin accretion disk; however, the yielded disk size is systematically larger than expected, although the ratio of the measured to theoretical disk sizes depends on using the emissivity- or responsivity-weighted disk radius. These results are broadly consistent with previous studies, all together raising a puzzle about the “standard” accretion disk model.