Thursday, July 25, 2013

1307.6223 (Main Pal et al.)

Variable X-ray reflection from 1H~0419--577    [PDF]

Main Pal, Gulab C. Dewangan
We present detailed broadband X-ray spectral variability of a Seyfert 1 galaxy 1H~0419--577 based on an archival \suzaku{} observation in July 2007, a new \suzaku{} observation performed in January 2010 and the two latest \xmm{} observations from May 2010. All the observations show soft X-ray excess emission below $2\kev$ and both \suzaku{} observations show a hard X-ray excess emission above $10\kev$ when compared to a power-law. We have tested three physical models -- a complex partial covering absorption model, a blurred reflection model and an intrinsic disk Comptonization model. Among these three models, the blurred reflection model provided statistically the best-fit to all the four observations. Irrespective of the models used, the soft X-ray excess emission requires contribution from a thermal component similar to that expected from an accretion disk. The partial covering absorption model results in a nonphysical high temperature ($kT_{in} \sim 100\ev$) for an accretion disk and is also statistically the worst fit among the three models. 1H~0419--577 showed remarkable X-ray spectral variability. The soft X-ray excess and the power-law both became weaker in January 2010 as well as in May 2010. A moderately broad iron line, detected in July 2007, is absent in the January 2010 observation. Correlated variability of the soft X-ray excess and the iron $K\alpha$ line strongly suggest reflection origin for both the components. However, such spectral variability cannot be explained by the light bending model alone and requires changes in the accretion disk/corona geometry possibly arising from changes in the accretion rate.
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