The X-ray bright z=0.116 quasar PKS 2155-304 is frequently observed as a
Chandra calibration source, with a total of 483 ksec of Low Energy Transmission
Grating (LETG) exposure time accumulated through May 2006. Highly-ionized metal
absorption lines, including numerous lines at z=0 and a putative OVIII K-alpha
line at z=0.055, have been reported in past Chandra studies of this source.
Using all available Chandra LETG spectra and analysis techniques developed for
such z=0 X-ray absorption along other sightlines, we revisit these previous
detections. We detect 4 absorption lines at >3\sigma significance (OVII
K-alpha/beta, OVIII K-alpha, and NeIX K-alpha), with OVII K-alpha being a
7.3\sigma detection. The 1\sigma ranges of z=0 OVII column density and Doppler
parameter are consistent with those derived for Mrk 421 and within 2\sigma of
the Mrk 279 absorption. Temperatures and densities inferred from the relative
OVII and other ionic column densities are found to be consistent with either
the local warm-hot intergalactic medium or a Galactic corona. Unlike the local
X-ray absorbers seen in other sightlines, a link with the low- or high-velocity
far-ultraviolet OVI absorption lines cannot be ruled out. The z=0.055 OVIII
absorption reported by Fang et al. is seen with 3.5\sigma confidence in the
ACIS/LETG spectrum, but no other absorption lines are found at the same
redshift.Comment: 11 pages, 9 figures; minor changes, accepted to Ap
