A soft X-ray reverberation lag in the AGN ESO 113-G010
  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 X-ray bands. At the lowest
frequencies available in the lightcurve (<1.5E-4 Hz), 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 (2-3)E-4 Hz we
find a soft lag of -325 +/- 89 s. 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 from the accretion
disk, with the reflection component responding to variability from the X-ray
corona. For a black hole mass of 7E6 M(solar) this corresponds to a
light-crossing time of ~9 R_g/c, 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.
