Multi-wavelength Campaign on the Super-Eddington NLS1 RX J0134.2-4258 --
  I. Peculiar X-ray Spectra and Variability
  We have conducted a new long-term multi-wavelength campaign on one of the
most super- Eddington narrow-line Seyfert 1s (NLS1s) known, namely RX
J0134.2-4258. In this first paper, we report deep simultaneous X-ray
observations performed by XMM-Newton and NuSTAR in 2019-12-19, during which RX
J0134.2-4258 was fortuitously at one of its lowest X-ray flux states. However,
there is a clear rise above 4 keV which implies that the intrinsic source flux
may be higher. The X-ray spectra observed between 1996 and 2019 show drastic
variability, probably due to complex, variable absorption along the line of
sight. Unusually, the soft X-ray excess appears extremely weak in all these
spectra, even when the hard X-ray spectrum has a steep slope of $\Gamma \simeq
2.2$. We explore the spectral-timing properties of the new (low X-ray flux) and
archival (high X-ray flux) XMM-Newton data, fitting their time-average, rms and
lag spectra simultaneously. The variability spectra indicate the presence of a
very weak soft X-ray Comptonisation component, whose shape is similar to the
soft excess in normal super-Eddington NLS1s, but with flux relative to the
power law which is lower by more than one order of magnitude. Above 4 keV the
low-flux data are dominated by a different component, which lags with respect
to the lower energy emission. This is consistent with an origin of reflection
or partial covering absorption from low ionization material located within 100
Rg. We interpret this as a further indication of the presence of a clumpy disc
wind.
