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Fig. 13 shows the extractions of two orders near the middle
of Fig. 11, but taken from a combination of more
exposures than those shown in the figure. The line of sight to
Ori has interstellar absorption lines from two conspicuous
velocity components, one at a heliocentric velocity of about 0 km s-1 and another at 24 km
s-1. The upper panel shows
absorptions by these two components in the 5-0 R(3) line of the Lyman
band system of H2, situated between two telluric absorption lines of
atomic oxygen in excited fine-structure states at 1040.942 and
1041.688Å. The double-humped, broad feature in the middle is
unidentified. In the lower panel, the fully saturated, broad features
are caused by absorption from singly-ionized carbon in the ground
fine-structure level (left) and an excited level (right). Other
features (the conspicuous double ones) are produced by hydrogen
molecules in the J = 0 and 1 rotational states (the 5-0 R(0)and R(1)
lines at 1036.546 and 1037.146Å, respectively).
12/15/1998