Low-energy gamma-rays from pulsar GX 1+4-balloon results

We present the results from a search of pulsed emission in low-energy gamma-rays from GX 1+4 source observed during zenith transit in a balloon experiment in April, 1982. The observed pulsar period is 120.6±0.2 s with pulsed emission flux of (1.3±0.4)×10^–5 photons cm^–2 s^–1 keV^–1 at an average energy 342 keV. These pulsations, observed at gamma-ray energies perhaps for the first time from any X-ray pulsar, in conjunction with the period determined in X-rays, indicate a spin-down in contrast with the spin-up behaviour observed by others at earlier epochs.