O vi in the local interstellar medium
  We report the results of a search for O VI absorption in the spectra of 80
hot DA white dwarfs observed by the FUSE satellite. We have carried out a
detailed analysis of the radial velocities of interstellar and (where present)
stellar absorption lines for the entire sample of stars. In approximately 35%
of cases (where photospheric material is detected), the velocity differences
between the interstellar and photospheric components were beneath the
resolution of the FUSE spectrographs. Therefore, in 65% of these stars the
interstellar and photospheric contributions could be separated and the nature
of the O VI component unambiguously determined. Furthermore, in other examples,
where the spectra were of a high signal-to-noise, no photospheric material was
found and any O VI detected was assumed to be interstellar. Building on the
earlier work of Oegerle et al. (2005) and Savage & Lehner (2006), we have
increased the number of detections of interstellar O VI and, for the first
time, compared their locations with both the soft X-ray background emission and
new detailed maps of the distribution of neutral gas within the local
interstellar medium. We find no strong evidence to support a spatial
correlation between O VI and SXRB emission. In all but a few cases, the
interstellar O VI was located at or beyond the boundaries of the local cavity.
Hence, any T ~ 300,000K gas responsible for the O VI absorption may reside at
the interface between the cavity and surrounding medium or in that medium
itself. Consequently, it appears that there is much less O VI-bearing gas than
previously stated within the inner rarefied regions of the local interstellar
cavity.
