E. M. Cackett, A. C. Fabian, A. Zoghbi, E. Kara, C. Reynolds, P. Uttley
Reverberation lags have recently been discovered in a handful of nearby, variable AGN. Here, we analyze a ~100 ksec archival XMM-Newton observation of the highly variable AGN, ESO 113-G010 in order to search for lags between hard (1.5 - 4.5 keV) and soft (0.3 - 0.9 keV) energy bands. At the lowest frequencies available in the lightcurve, we find hard lags where the power-law dominated hard band lags the soft band where the reflection fraction is high. However, at higher frequencies in the range 2E-4 - 3E-4 Hz we find a soft lag of 325 +/- 89 seconds at greater than the 3.5-sigma level. The general evolution from hard to soft lags as the frequency increases is similar to other AGN where soft lags have been detected. We interpret this soft lag as due to reverberation, with the reflection component responding to variability in the power-law. For a black hole mass of 7E6 M_solar this corresponds to a light-crossing time of ~9 GM/c^3, however, dilution effects mean that the intrinsic lag is likely longer than this. Based on recent black hole mass-scaling for lag properties, the lag amplitude and frequency are more consistent with a black hole a few times more massive than the best estimates, though flux-dependent effects could easily add scatter this large.
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http://arxiv.org/abs/1210.7874
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