Hard X-Ray Spectroscopy and Pulsar Phase Analysis of the Bursting X-Ray Pulsar GRO J1744-28 with OSSE
NAVAL RESEARCH LAB WASHINGTON DC
Pagination or Media Count:
We report OSSE observations of the bursting X-ray pulsar GRO J174428 made in December 1995 and January 1996 at hard X-ray energies 35 keV. The pulse profile of the persistent i.e. non-bursting pulsar emission is fit with a sinusoid in the energy range 3590 keV. Residuals reveal a second harmonic amplitude of 30 - 05 of the fundamental. The distribution of time intervals between bursts measured in January is characterized by a broad at-topped function with width 35 min and mean 33 min. The burst profile averaged over an ensemble of 104 bursts in the 3560 keV energy range has FWHM width of 36 - 03 s and displays a factor of 2 faster rise time than decay and a pronounced dip in persistent emission after the burst. The phase of the sinusoidal pulse profile during bursts lags the phase prior to bursts by 90 ms 12 radians, and a 29 - 6 ms 039 - 008 radians lag persists following the burst. There are no statistically significant spectral differences between the hard X-ray spectra of the bursting and persistent emission in the OSSE energy range, nor is there any evidence of annihilation or neutron capture line emission or cyclotron absorption.
- Nuclear Physics and Elementary Particle Physics