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Pulsed X‐Ray Emission from the Fastest Millisecond Pulsar: PSR B1937+21 with ASCA

2001; IOP Publishing; Volume: 554; Issue: 1 Linguagem: Inglês

10.1086/321330

1538-4357

M. Takahashi, Shinpei Shibata, K. Torii, Y. Saito, Nobuyuki Kawai, M. Hirayama, Tadayasu Dotani, Shuichi Gunji, Hirohisa Sakurai, I. H. Stairs, R. N. Manchester,

Astrophysics and Cosmic Phenomena

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.