Pulsed X-Ray Emission from the Fastest Millisecond Pulsar: PSR B1937+21 with ASCA
Abstract
We have detected pulsed X-ray emission from the fastest millisecond pulsar known, PSR B1937+21 (P=1.558 ms), with ASCA. The pulsar is detected as a point source above ~1.7 keV, with no indication of nebulosity. The source flux in the 2-10 keV band is found to be f=(3.7+/-0.6)×10-13 ergs s-1 cm-2, which implies an isotropic luminosity of LX=4πD2f~(5.7+/- 1.0)×1032(D/3.6 kpc)2 ergs s-1, where D is the distance, and an X-ray efficiency of ~5×10-4, relative to the spin-down power of the pulsar. The pulsation is found at the period predicted by the radio ephemeris with a very narrow primary peak, the width of which is about 1/16 phase (~100 μs), near the time resolution limit (61 μs) of the observation. The instantaneous flux in the primary peak (1/16 phase interval) is found to be (4.0+/-0.8)×10-12 ergs s-1 cm-2. Although there is an indication for the secondary peak, we consider its statistical significance too low to claim a definite detection. The narrow pulse profile and the detection in the 2-10 keV band imply that the X-ray emission is caused by the magnetospheric particle acceleration. Comparison of X-ray and radio arrival times of pulses indicates, within the timing errors, that the X-ray pulse is coincident with the radio interpulse.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2001
- DOI:
- 10.1086/321330
- arXiv:
- arXiv:astro-ph/0104476
- Bibcode:
- 2001ApJ...554..316T
- Keywords:
-
- Stars: Pulsars: General;
- Stars: Pulsars: Individual: Alphanumeric: PSR B1937+21;
- Astrophysics
- E-Print:
- 14 pages with 5 figures. Ap. J. in press