Abstract Details

Name: Savithri H Ezhikode
Affiliation: Inter-University Centre for Astronomy and Astrophysics
Conference ID: ASI2021_216
Title : Correlation between reflection fraction and photon index in AGN
Authors and Co-Authors : Savithri H. Ezhikode (IUCAA, Pune), Gulab C. Dewangan (IUCAA, Pune), Ranjeev Misra (IUCAA, Pune), Ninan Sajeeth Philip (Artificial Intelligence Research and Intelligent Systems, Thelliyoor, Kerala; IUCAA, Pune)
Abstract Type : Poster
Abstract Category : Extragalactic Astronomy
Abstract : The primary X-ray emission from Active Galactic Nuclei (AGN) is believed to be produced by the Comptonisation of the optical/UV photons from the accretion disc by the hot electrons in the corona. This primary power-law continuum irradiates the accretion disc and the circumnuclear material producing reflection features in the X-ray spectrum. The reflection features arising from the inner regions of the disc could be significantly modified by the relativistic effects near the black hole. Furthermore, the area of the reflecting medium and the location of the X-ray emitting region can affect the amount of reflection. Here, we investigate the relationship between the relativistic reflection fraction (R_f) and the hard X-ray photon index (Gamma) of a NuSTAR sample of Seyfert 1 galaxies. The X-ray spectra of the sources are modelled using RELXILL code which directly provides the reflection fraction of a relativistically smeared reflection component. R_f depends on the amount of Comptonised X-ray emission intercepted by the inner accretion disc and is defined as the ratio of the coronal intensity that illuminates the accretion disc to that observed directly. We found a strong positive correlation between Gamma and R_f in our sample. Seed photons from a larger area of an accretion disc entering the corona will increase the cooling of the coronal plasma, giving rise to steeper X-ray spectrum. Also, the corona irradiating a larger area of the disc will enhance reflection fraction. Thus, the observed R_f–Gamma correlation is most likely related to the changes in the disc–corona geometry of AGN.