2020/09/21 by Christos Panagiotou, I. E. Papadakis, Iossif Papadakis +2 · 20 citations
Physics and Astronomy · #Accretion (finance) #Accretion disc #Active galactic nucleus #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Corona (planetary geology) #Emission spectrum #Galaxies: Formation, Evolution, Phenomena #Galaxy #Lag #Optics #Physics #Spectral line #Stellar, planetary, and galactic studies #Wavelength #astro-ph.GA
paper · pdf · doi:10.1093/mnras/staa2920
published in Monthly Notices of the Royal Astronomical Society 499(2), 1998-2006 (Oxford University Press) · 11 pages, 7 figures, in press by MNRAS
arxiv created 2020/09/21 · openalex publication_date 2020/09/25 · arxiv updated 2020/10/07 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
ABSTRACT NGC 5548 was recently monitored intensively from NIR to X-rays as part of the STORM campaign. Its disc emission was found to lag behind the observed X-rays, while the measured time lag was increasing with wavelength. These results are consistent with the assumption that short-term variability in AGN emission is driven by the X-ray illumination of the accretion disc. In this work, we studied the power spectrum of UV/optical and X-ray emission of NGC 5548, using the data of the STORM campaign as well as previous Swift data, in order to investigate the relation between the UV/optical and X-ray variability and to examine its consistency with the above picture. We demonstrate that even the power spectrum results are compatible with a standard disc being illuminated by X-rays, with low accretion rates, but the details are not entirely consistent with the results from the modelling of the ‘τ versus λ’ relation. The differences indicate that the inner disc might be covered by a ‘warm corona’ which does not allow the detection of UV/optical emission from the inner disc. Finally, we found strong evidence that the UV emission of NGC 5548 is not stationary.