An RXTE Observation of the Vela Pulsar: Filling in the X-ray Gap

Abstract

We have detected pulsed emission from the Vela pulsar at 2 - 30 keV during a 93 ks observation with the Rossi X-Ray Timing Explorer (RXTE). The RXTE pulse profile shows two peaks, that are roughly in phase with the EGRET peaks, but does not show any significant interpeak emission. The phase of Peak 2 is energy dependent, moving to higher phase with increasing energy in the RXTE band, in phase alignment with the second optical pulse in the lowest energy band of 2 - 8 keV and in phase alignment with the second EGRET pulse in the highest energy band of 16-30 keV. The average pulse spectrum joins smoothly to the high energy spectrum of OSSE, COMPTEL and EGRET, although the spectrum of Peak 1 is significantly harder than that of Peak 2. A break or turnover in the spectrum around 50 keV, previously suggested by OSSE data, is now clearly defined. The RXTE spectrum falls several orders of magnitude below the ROSAT emission in the 0.1 - 2 keV band, suggesting a thermal origin for the ROSAT pulse.