Anisotropic X-ray transfer in a strongly magnetized plasma of the X-ray pulsar 4U 1626-67.

The X-ray pulsar 4U 1626-67 was observed with Tenma during the period May 3 through 5, 1983. No appreciable change in the spectrum was observed during X-ray flares. The pulse period of 7.671350 s and the rate of period change are consistent with a stable spin-up at a rate of about 0.0002/yr. The pulse profile changes drastically at about 15 keV and 2 keV, and the energy spectrum depends on the pulse phase accordingly. No emission line feature of iron around 6 keV was found with an upper limit of the equivalent width of 60 eV. The observed energy dependence of the X-ray pulse profile was simulated by a calculation based on the anisotropic radiation transfer in a strongly magnetized plasma with a magnetic field strength of about 8 x 10 to the 12th G at the neutron star surface.