Swift, NuStar and XMM-Newton observations of the NLS1 galaxy RX
  J2317.8-4422 in an extreme X-ray low flux state
  We report the discovery of RX J2317.8-4422 in an extremely low X-ray flux
state by the Neil Gehrels Swift observatory in 2014 April/May. In total, the
low-energy X-ray emission dropped by a factor 100. We have carried out
multi-wavelength follow-up observations of this Narrow-Line Seyfert 1 galaxy.
Here we present observations with Swift, XMM-Newton, and NuSTAR in October and
November 2014 and further monitoring observations by Swift from 2015 to 2018.
Compared with the beginning of the Swift observations in 2005, in the November
2014 XMM and NuSTAR observation RX J2317--4422.8 dropped by a factor of about
80 in the 0.3-10 keV band. While the high-state Swift observations can be
interpreted by a partial covering absorption model with a moderate absorption
column density of $N_H=5.4\times 10^{22}$ cm$^{-2}$ or blurred reflection, due
to dominating background at energies above 2 keV the low-state XMM data can not
distinguish between different multi-component models and were adequately fit
with a single power-law model.
  We discuss various scenarios like a long-term change of the accretion rate or
absorption as the cause for the strong variability seen in RX J2317.8--4422.
