X‐Ray/Gamma‐Ray Observations of the PSR B1259−63/SS 2883 System near Apastron

Abstract

We report the results from X-ray and hardX-ray observations of the PSR B1259-63-SS 2883 system with ASCA andthe Compton Gamma-Ray Observatory (CGRO), performed between 1995February and 1996 January when the pulsar was near apastron. Thesystem was clearly detected in each of the two ASCA observations withluminosity in the 1-10 keV band of L_X=(9+/-3)x10^32 (d/2 kpc)^2ergs s^-1, while CGRO-OSSE did not detect significant hard X-raysfrom the system. X-ray spectra obtained with ASCA are well fitted bya single power-law spectrum with a photon index of 1.6+/-0.3. Nopulsations were detected in either the ASCA or the OSSE data. Wecombine all existing X-ray and hard X-ray observations and presentthe orbital modulation in the luminosity and photon index for theentire orbit. The results are in agreement with predictions based on asynchrotron emission model from relativistic particles in a shockedpulsar wind interacting with the gaseous outflow from the Be star.