High Energy X-Ray Observations of GX:1+4 with HEXE

Two observations with the High Energy X ray Experiment (HEXE) on board the Soviet Kvant module and performed on the X ray pulsar GX 1+4(4U1728-24) are reported. During the first observation on Oct. 31, 1987 the luminosity in the energy range 20 to 60 keV was 2 x 10 ³⁷ erg/sec. For the second observation, lasting from 23 to 27 Sep. 1988 there is no reliable aspect information available. The phase averaged spectra of both observations are well fitted by a thermal bremsstrahlung. A comparison to spectra, gained during the high state of GX 1+4, shows that the spectrum is now significantly harder. The timing analysis using an epoch folding method allowed obtaining of pulsational periods. The pulse periods fit well together with periods determined by Ginga, defining a long term spin down of GX 1+4.