Chandra and XMM-Newton observations of the exceptional pulsar PSR B0628-28

PSR B0628-28 is a radio pulsar which was first detected in the X-ray band by ROSAT and then later observed with Chandra and XMM-Newton. The Chandra observation yielded an X-ray luminosity two orders of magnitude higher than what is expected for spin-powered pulsars, also there were no pulsations detected. The XMM-Newton observation, however, reveals pulsations at the expected radio period, P=1.244 s. The simultaneously analyzed spectra also gives a luminosity (in cgs) Log Lx=30.34, which is ~350 times greater than what would be expected from the correlation between Lx-Edot.Comment: 13 pages, 4 figures, to be published in ApJ

The ASCA Spectrum of the Vela Pulsar Jet

ROSAT observations of the Vela pulsar and its surroundings revealed a collimated X-ray feature almost 45' in length (Markwardt & Ogelman 1995), interpreted as the signature ``cocoon'' of a one-sided jet from the Vela pulsar. We report on a new ASCA observation of the Vela pulsar jet at its head, the point where the jet is believed to interact with the supernova remnant. The head is clearly detected, and its X-ray spectrum is remarkably similar to the surrounding supernova remnant spectrum, extending to X-ray energies of at least 7 keV. A ROSAT+ASCA spectrum can be fit by two-component emission models but not standard one-component models. The lower energy component is thermal and has a temperature of 0.29+/-0.03 keV (1 sigma); the higher energy component can be fit by either a thermal component of temperature ~4 keV or a power law with photon index ~2.0. Compared to the ROSAT-only results, the mechanical properties of the jet and its cocoon do not change much. If the observed spectrum is that of a hot jet cocoon, then the speed of the jet is at least 800 km s^-1, depending on the angle of inclination. The mechanical power driving the jet is >10^36 erg s^-1, and the mass flow rate at the head is > 10^-6 M_sun yr^-1. We conclude that the jet must be entraining material all along its length in order to generate such a large mass flow rate. We also explore the possibility that the cocoon emission is synchrotron radiation instead of thermal.Comment: 12 pages, LaTeX in AAS v4.0 preprint style, two PS figures, accepted for publication in the ApJ Letter

Discovery of extended emission around the pulsar B0355+54

PSR B0355+54 is one of the handful of pulsars that have been observed with both Chandra and XMM-Newton. The analysis of the archival data has revealed the pulsar and a similar to 30" compact nebula surrounding it. XMM-Newton also has detected a trail that extends similar to 6' and, similar to the compact nebula, is also counteraligned with the proper motion of the pulsar. The spectra of both the pulsar and the extended emission are well described by an absorbed power-law model. The measured flux corresponds to an efficiency of converting the spin-down luminosity into X-rays in the 2-10 keV band of similar to 0.01% and similar to 1% for the pulsar and the extended emission, respectively. From the XMM-Newton data we have detected pulsations at the expected radio period. The energetics and the extent of the extended emission can be explained by a bow shock formed by the motion of the pulsar through the interstellar medium