ABSTRACT. We present X-ray observations of two young energetic radio pulsars, PSRs B1046-58 and B1610-50, and their surroundings, using archival data from the Advanced Satellite for Cosmology and Astrophysics (ASCA). The energetic pulsar PSR B1610-50 is detected in X-rays with a significance of 4.5 σ. The unabsorbed flux, estimated assuming a power-law spectrum and a neutral hydrogen column density N_H of 5 × 10²¹ cm^-2, is (2.5 ± 0.3) × 10^-13 ergs cm^-2 s^-1 in the 2-10 keV band. Pulsed emission is not detected; the pulsed fraction is less than 31% at the 90% confidence level for a 50% duty cycle. We argue that the emission is best explained as originating from a pulsar-powered synchrotron nebula. The X-ray counterpart of the pulsar is the only hard source within the 95% error region of the previously unidentified γ-ray source 3EG J1048-5840. This evidence supports the results of Kaspi et al., who suggest, in a companion paper, that PSR B1046-58 is the counterpart to 3EG J1048-5840. X-ray emission from PSR B1610-50 is not detected. Using assumptions similar to those above, the derived 3 σ upper limit for the unabsorbed 2-10 keV X-ray flux is 1.5 × 10^-13 ergs cm^-2 s^-1. We use the flux limit to estimate the pulsar's velocity to be less than ~170 km s^-1, casting doubt on a previously reported association between PSR B1610-50 and supernova remnant Kes 32. Kes 32 is detected, as is evident from the correlation between X-ray and radio emission. The ASCA images of PSR B1610-50 are dominated by mirror-scattered emission from the X-ray-bright supernova remnant RCW 103, located 33' away. We find no evidence for extended emission around either pulsar, in contrast to previous reports of large nebulae surrounding both pulsars.

Subject headings: gamma rays: observations; pulsars: individual (PSR B1046–58, PSR B1610–50); stars: neutron; supernova remnants; X-rays: stars

Print publication: Issue 1 (2000 January 1)
Received 1998 November 23, accepted for publication 1999 August 16