X-ray variability of the pulsar Vela X-1 as observed with ART-P/Granat

Observations of the X-ray pulsar Vela X-1 with the ART-P telescope onboard the Granat Observatory are presented. Variability on a time scale of severa l thousand seconds was detected, intensity variations are shown to be accom panied by changes in the source's spectrum. The hardness was also found to be highly variable on a scale of one pulsation period. The source's spectru m exhibits an absorption feature at energy similar to 27 keV, which is appa rently attributable to cyclotron scattering/absorption in the neutron-star magnetic field. Weak persistent emission was detected during an X-ray eclip se, which probably resulted from the scattering of pulsar emission in the s tellar wind from an optical star. (C) 2000 MAIK "Nauka/Interperiodica".