Extreme ultra-soft X-ray variability in an eROSITA observation of the
  Narrow-Line Seyfert 1 Galaxy 1H 0707-495
  The ultra-soft narrow-line Seyfert 1 galaxy 1H 0707-495 is a well-known and
highly variable active galactic nucleus (AGN), with a complex, steep X-ray
spectrum, and has been studied extensively with XMM-Newton. 1H 0707-495 was
observed with the extended ROentgen Survey with an Imaging Telescope Array
(eROSITA) aboard the Spectrum-Roentgen-Gamma (SRG) mission on October 11, 2019,
for about 60,000 seconds as one of the first calibration and pointed
verification phase (CalPV) observations. The eROSITA light curves show
significant variability in the form of a flux decrease by a factor of 58 with a
1 sigma error confidence interval between 31 and 235. This variability is
primarily in the soft band, and is much less extreme in the hard band. No
strong ultraviolet variability has been detected in simultaneous XMM-Newton
Optical Monitor observations. The UV emission is about 10^44 erg s^-1, close to
the Eddington limit. 1H 0707-495 entered the lowest hard flux state seen in 20
years of XMM-Newton observations. In the eROSITA All-Sky Survey (eRASS)
observations taken in April 2020, the X-ray light curve is still more variable
in the ultra-soft band, but with increased soft and hard band count rates more
similar to previously observed flux states. A model including relativistic
reflection and a variable partial covering absorber is able to fit the spectra
and provides a possible explanation for the extreme light-curve behaviour. The
absorber is probably ionised and therefore more transparent to soft X-rays.
This leaks soft X-rays in varying amounts, leading to large-amplitude
soft-X-ray variability.
