On the Origin of Highly Ionized X-ray Absorbers Detected in the Galactic
  X-ray Binaries
  X-ray observations of the Galactic X-ray binaries (XRB) revealed numerous
highly ionized metal absorption lines. However, it is unclear whether such
lines are produced by the hot interstellar medium (ISM) or the circumstellar
medium (CSM) intrinsic to the binaries. Here we present a Chandra X-ray
absorption line study of 28 observations on 12 X-ray binaries, with a focus on
the NeIX and FeXVII lines. We report the first detections of these lines in a
significant amount of observations. We do not find significant dependence of
the line equivalent width on the distance of the XRBs, but we do see weak
dependence on the source X-ray luminosity. We also find two out of twelve
selected targets show strong temporal variation of the NeIX absorbers. While
the line ratio between the two ion species suggests a temperature consistent
with the previous predictions of the ISM, comparing with two theoretical models
of the ISM shows the observed column densities are significantly higher than
predictions. On the other hand, photoionzation by the XRBs provides reasonably
good fit to the data. Our findings suggest that a significant fraction of these
X-ray absorbers may originate in the hot gas intrinsic to the X-ray binaries,
and that the ISM makes small, if not negligible, contribution. We briefly
discuss the implications to the study of the Milky Way hot gas content.
