Abstract Details

Name: Nabanita Das
Affiliation: Presidency University, Kolkata
Conference ID: ASI2021_400
Title : Contribution of X-ray Reprocessing in the Longterm Optical Variability of the Radio Galaxies 3C 120 and 3C 111
Authors and Co-Authors : Nabanita Das (Presidency University, Kolkata), Tathagata Saha (Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences, Warszawa, Poland), and Ritaban Chatterjee (Presidency University, Kolkata)
Abstract Type : Poster
Abstract Category : Extragalactic Astronomy
Abstract : The optical and ultraviolet radiation of active galactic nuclei (AGN) originates from the accretion disk and the X-rays are presumably produced at a tenuous distribution of high energy electrons called the corona. The mechanism of the coronal X-ray emission is believed to be inverse-Compton scattering of the optical-UV photons generated in the disk. Part of the optical-UV emission may be due to the reprocessing of the coronal X-rays at the disk. The origin of the optical-UV emission variability has been extensively debated in the literature in the last decade, the main candidates being intrinsic fluctuation of the disk and variability of the X-rays which are reprocessed in the disk. We analyze the long term (few years) time variability of the optical emission of the broad line radio galaxies 3C 111 and 3C 120 in the context of the above disk-corona connection. We have considered the lamp-post model, in which the corona is thought to be a point source above the plane of the disk. We find, for a large parameter space of the model, that reprocessing of the 2-10 keV X-ray emission alone without any intrinsic fluctuation of the accretion disk is not enough to reproduce the optical variability amplitude and flux level in either of the two sources. We model the variability of the underlying disk emission and the X-ray reprocessing in order to reproduce, approximately, the observed variability and the flux levels in the observed R-band light curves. In such a model with a variable disk emission, the reprocessed fraction contributes a minor part, approximately 15%, of the total R-band emission.