Multi-epoch properties of the warm absorber in the Seyfert 1 galaxy NGC
  985
  (Abridged) NGC 985 was observed by XMM-Newton twice in 2015, revealing that
the source was coming out from a soft X-ray obscuration event that took place
in 2013. These kinds of events are possibly recurrent since a previous
XMM-Newton archival observation in 2003 also showed signatures of partial
obscuration. We have analyzed the high-resolution X-ray spectra of NGC 985
obtained by the RGS in 2003, 2013, and 2015 in order to characterize the
ionized absorbers superimposed to the continuum and to study their response as
the ionizing flux varies. We found that up to four warm absorber (WA)
components were present in the grating spectra of NGC 985, plus a mildy ionized
(log xi ranging between 0.2 and 0.5) obscuring (log N(H) of about 22.3) wind
outflowing at about 6000 km/s. The absorbers have a log N(H) ranging from 21 to
about 22.5, and ionization parameters ranging from 1.6 to 2.9. The most ionized
component is also the fastest, moving away at 5100 km/s, while the others
outflow in two kinematic regimes, at about 600 and 350 km/s. These components
showed variability at different time scales in response to changes in the
ionizing continuum. Assuming that these changes are due to photoionization we
have obtained upper and lower limits on the density of the gas and therefore on
its distance, finding that the closest two components are at pc-scale
distances, while the rest may extend up to tens of pc from the central source.
The fastest, most ionized WA component accounts for the bulk of the kinetic
luminosity injected back into the ISM of the host galaxy, which is on the order
of 0.8% of the bolometric luminosity of NGC 985. According to the models, this
amount of kinetic energy per unit time would be sufficient to account for
cosmic feedback.
