http://arxiv.org/abs/1802.06056
In addition to stochastic variability, a fraction of active galactic nuclei (AGN) are observed to exhibit dramatic variability in the X-ray band on timescales down to minutes. We introduce the case study of 1H 1934-063 (z = 0.0102), a Narrow-line Seyfert 1 (NLS1) among the brightest and most variable AGN ever observed with XMM-Newton. This work includes spectral and temporal analyses of a concurrent XMM-Newton and NuSTAR 2015 observation lasting 130 kiloseconds, during which the X-ray source exhibited a steep (factor of 6) plummet and subsequent full recovery of flux level. We rule out Compton-thin obscuration as the cause for this dramatic variability observed even at NuSTAR energies. In order to constrain coronal geometry, dynamics, and emission/absorption processes, we compare detailed spectral fitting with Fourier-based timing analysis. Similar to other well-studied, highly variable Seyfert 1s, this AGN is X-ray bright and displays strong reflection features. We find a narrower broad iron line component compared to most Seyfert 1s, and constrain black hole spin to be < 0.1, one of the lowest yet discovered for such systems. Combined spectral and timing results are consistent with a dramatic change in the continuum on timescales as short as a few kiloseconds dictating the nature of this variability. We also discover a Fe-K time lag and measure a delay of 20 seconds between relativistically-blurred reflection off the inner accretion flow (0.3-1 keV) and the hard X-ray continuum emission (1-4 keV).
S. Frederick, E. Kara, C. Reynolds, et. al.
Mon, 19 Feb 18
18/41
Comments: 12 pages, 11 figures