XMM-Newton Survey of Local OVII Absorption Lines in the Spectra of
  Galactic X-ray Sources
  The detection of highly ionized metal absorption lines in the X-ray spectra
of the Galactic X-ray binaries (XRBs) implies the distribution of hot gas along
the sightline toward the background sources. However, the origin of this hot
gas is still unclear: it can arise in the hot interstellar medium (ISM), or is
intrinsic to the XRBs. In this paper, we present an XMM-Newton survey of the
OVII absorption lines in the spectra of Galactic XRBs. A total of 33 XRBs were
selected, with 29 low mass XRBs and 4 high mass XRBs. At more than 3$\sigma$
threshold, OVII absorption line was detected in 16 targets, among which 4 were
newly discovered in this work. The average line equivalent width (EW) is
centered around $\sim$ 20 m\AA. Additionally we do not find strong correlations
between the OVII EWs and the Galactic neutral absorption N$_{\rm H}$, the
Galactic coordinates or the distance of background targets. Such
non-correlation may suggest the contamination of the circumstellar material, or
the lack of constrains on the line Doppler-b parameter. We also find regardless
the direction of the XRBs, the OVII absorption lines were always detected when
the flux of the background XRBs reach a certain level, suggesting a uniform
distribution of this hot gas. We estimate a ratio of 0.004 --- 0.4 between hot
and neutral phase of the interstellar medium. This is the second paper in the
series following Fang et al. 2015, in which we focused on the local OVII
absorption lines detected in the background AGN spectra. Detailed modeling of
the hot ISM distribution will be investigated in a future paper.
