DISCOVERY OF A PECULIAR X-RAY PULSAR GS-1843+00

A transient X-ray pulsar with a period of about 29.5 s was discovered with the Ginga satellite at a position of α (1950) = 18h43m±1m, δ (1950) = 0°52′±7′ (GS 1843+00). The X-ray intensity was in the range of 30-60 mCrab. The peak-to-peak pulse amplitude was unusually small, about only 4% of the average flux in the 2-37 keV band. This amplitude is smaller at lower energies. The pulse profile is a simple sinusoid at low energies, whereas it exhibits two peaks at higher energies. GS 1843+00 also exhibits a large-amplitude aperiodic intensity variation on a wide range of time scales, which is superposed on this small amplitude of the coherent pulsation. The amplitude of the aperiodic variation is larger at low energies than at high energies, in contrast to the coherent pulsation.