X-ray observations of the binary pulsar 4U:1907+09

We have studied the x-ray binary pulsar 4U 1907+09 in the energy band 20-100 keV. The observations were carried out using a xenon filled multilayer proportional counter telescope flown from Hyderabad in 1985 March. The source and a background region 8 away from the source were tracked alternately for a total time of 3 h. The source was detected above 20 keV at a significance level of 16. A pulse period of 432.5±1.5s was obtained for the source. Using the pulse period of 437.5s obtained earlier by the Tenma satellite in 1983, a period derivative of -1±.3*10-7 ss-1 is derived. this large period derivative is also confirmed by the analysis of the MPC data obtained from the Einstein observatory under the guest investigator program. The spectra of the source are well fitted with a power law of index-1.2 and shows a large H-column of 1.6*1022 cm-2