Oral Presentation

Modelling the Extreme X-ray Spectrum of IRAS 13224-3809

Chia-Ying Chiang, Dominic Walton, Andy Fabian, Dan Wilkins, and Luigi Gallo

The extreme NLS1 galaxy IRAS 13224-3809 shows significant X-ray variability, frequency depended time lags, and strong Fe K line and Fe L features in the long 2011 XMM-Newton observation. We study the spectral properties of IRAS 13224-3809 in detail, and carry out a series of analyses to probe the nature of the source, focusing in particular on the spectral variability exhibited. We fit the 0.3-10.0 keV spectra with a model that includes relativistic reflection from the inner accretion disc, a standard powerlaw AGN continuum, and a low-temperature (~0.1 keV) blackbody, which may originate in the accretion disc, either as direct or reprocessed thermal emission. We find that the reflection model explains the time-averaged spectrum well, and we also undertake flux-resolved and time-resolved spectral analyses, which provide evidence of gravitational light-bending
effects.