| Name: | Shrabani Kumar |
| Affiliation: | Inter-University Centre for Astronomy And Astrophysics |
| Conference ID : | ASI2023_665 |
| Title : | Ultraviolet Grating Spectroscopy of AGN using AstroSat/UVIT |
| Authors : | Shrabani Kumar, G. C. Dewangan, K. P. Singh, Poshak Gandhi, I. E. Papadakis, Prakash Tripathi and Labani Mallick |
| Mode of Presentation: | Oral |
| Abstract Category : | Extragalactic Astronomy |
| Abstract : | We perform far ultra-violet grating spectroscopy of eight Seyfert 1-1.5 active galactic nuclei (AGN) using AstroSat/UVIT slitless grating observations and study the accretion discs in these AGN. We derive intrinsic continuum disc emission after correcting the observed spectra for the Galactic and intrinsic extinctions and possible contributions from host galaxy emission, FeII complex and emissions from broad and narrow line regions. We generally find a redder continuum slope than that predicted by the Standard disc model. To further understand the nature of discs, we used three accretion disc models - the multi-color disc blackbody (DISKBB), intrinsic Comptonised disc (OPTXAGNF) and fully relativistic disc (ZKERRBB). The observed inner disc temperatures derived using the DISKBB model lie in the range of ~ 31 - 3.6 eV, which decreases with increasing black hole mass. For a standard non-rotating disk, these temperatures are lower than that predicted. The intrinsic disc Comptonised model OPTXAGNF provided the Eddington luminosity ratios in the range of 0.003-69. The inner disc radius for most of the AGN could not be constrained and indicated a possibility of truncation of the disc above ISCO for some of the AGN. We could not constrain the parameters (accretion rate, inclination angle) in ZKERRBB. These results indicate that other emission components such as the soft X-ray excess and/or the broadband X-ray power law could be contributing to the UV emission. We are in the process of multi-wavelength UVIT+SXT+LAXPC spectral modeling of these AGN. |
