The X-ray binary Her X-1 was observed using the Chandra
low energy transmission grating spectrometer (LETGS)
during its anomalous low state and 10 months later during the
X-ray bright phase. These observations allow us for the first
time to detect emission, in the form of the intercombination
lines of density sensitive He-like OVII and NVI triplets as well
as the Lya-like OVIII and NVII lines, from the corona above
the accretion disc in Her X-1. The He-like emission lines
seem to be present at all times. Both data sets cover nearly
the same range in orbital phase which allows for good
comparison of properties in the different states. Additionally
the second data set shows clearly a series of pre-eclipse
dips. The spin period was not detected in the anomalous low
state but clearly in the X-ray 35-day period bright data where
the period we obtain indicates that the spin-period is
continuing to increase. A detailed analysis of these
fascinating observations of Her X-1 will be presented here.
CATEGORY:
BLACK HOLE AND NEUTRON STAR BINARIES