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   PR # 42059
   The massive X-ray binary pulsar 4U1907+09 appears to have a
   supergiant companion and an orbital light curve characterized by two
   flares separated by about half the orbit, similar to GX301-2. The
   most natural explanation for these systems is that the neutron star's
   orbit is inclined to that of a matter envelope in the companion's
   equatorial plane. We will test this hypothesis by obtaining four 20
   ksec observations of 4U1907+09 distributed around the 8.38 day orbit
   to map out the hydrogen column density and iron line emission of the
   matter envelope. We will also examine how the spectra changes with
   the phase of the 437.5 sec pulse period in order to test theories of
   pulse profile production, as well as updating the orbital parameters
   of the system and measurements of the pulsar spin-down.
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