Kavli Affiliate: Erin Kara
| First 5 Authors: Peter Kosec, Peter Kosec, , ,
| Summary:
X-ray binary accretion disk winds can carry away a significant fraction of
the originally infalling matter and hence strongly affect the accretion flow
and the long-term evolution of the binary system. However, accurate
measurements of their mass outflow rates are challenging due to uncertainties
in our understanding of the 3D wind structure. Most studies employ absorption
line spectroscopy that only gives us a single sightline through the wind
streamlines. Hercules X-1 is a peculiar X-ray binary which allows us to avoid
this issue, as its warped, precessing accretion disk naturally presents a range
of sightlines through the vertical structure of its disk wind. Here we present
the first results from a large, coordinated campaign on Her X-1 led by the new
XRISM observatory and supported by XMM-Newton, NuSTAR and Chandra. We perform a
time-resolved analysis and constrain the properties of the wind vertical
structure. Thanks to the precision spectroscopy of XRISM/Resolve, we directly
detect the Her X-1 orbital motion in the evolution of the outflow velocity.
After correcting for this effect, we observe an increase in velocity from 250
km/s to 600 km/s as the wind rises to greater heights above the disk. The wind
column density decreases with height, as expected, but its ionization parameter
only evolves weakly, and is consistent with freezing out as the wind expands
away. Additionally, we detect a new orbital dependence of the wind properties,
revealing a likely second wind component that appears only briefly after the
eclipse of Her X-1 by the secondary star.
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