Near absence of hard X-ray pulsation from GS 1843+00 in the middle of burst phase

Abstract

Hard X-ray transient pulsar GS 1843+00 was observed in the 20-200keV region using a high sensitivity large area scintillation counter instrument during its 1997 flare on March 30. The data indicates a near absence of 29.5s pulsation in the hard X-ray energy band of 30-70 keV, even though our observations correspond near to intensity maximum in the burst phase. Along with the RXTE and Compton observatory data taken during this burst, we discuss the present results in terms of geometrical constraints and the X-ray emission mechanism.