[Previous] | [Session 41] | [Next]
M. Pivovaroff, V. M. Kaspi (MIT), E. V. Gotthelf (Columbia)
We present a study of ASCA observations of the energetic Galactic pulsars PSR~B1046-58 and PSR~B1610-50. The wide PSF (~arc-minutes) of ASCA and multiple point sources situated near the pulsar make characterization of the X-ray detection of PSR~B1046-58 difficult. Focusing on the superior spatial resolution of the SIS detectors, we have determined a detection significance of 4.6-8.3\sigma, the variation resulting from different methods to account for contamination from neighboring sources. Timing analysis of GIS data found no evidence for pulsation, with the pulsed fraction less than 31% at the 90% confidence level. We argue the emission is from a spatially unresolved synchrotron nebula powered by the pulsar. Assuming a canonical powerlaw spectrum and column density, we estimate the unabsorbed 2-10 keV flux to be ~3\times10-13 ergs s-1 cm-2. The implied efficiency for conversion of spin-down luminosity to ASCA-band emission is ~2\times10-4, below values predicted by empirical Lx-\dot{E} relationships derived from Einstein and ROSAT. We have also examined the 95% position error circle of the previously unidentified \gamma-ray source 3EG~J1048-5840, which lies entirely within the GIS FOV. The only hard source within the circle is coincident the pulsar. This evidence, coupled with the \gamma-ray pulsations from 3EG~J1048-5840 reported in a companion presentation by Kaspi et al. strongly suggests PSR~B1046-58 as the eighth known pulsar that exhibits \gamma-rays. X-ray emission from PSR~B1610-50 is not detected. Using similar assumptions as above, the derived 3\sigma upper limit for the X-ray flux is 1.4\times10-13 ergs s-1 cm-2, implying a conversion efficiency of spin-down luminosity to ASCA-band emission no greater than ~5\times10-4. The analysis of these observations contradict previous reports of detections of large (tens of arc-minutes) synchrotron nebulae or plerions associated with both pulsars.