Letter to the Editor

The phase of the radio and X-ray pulses of PSR B1937+21

¹ Istituto di Astrofisica Spaziale e Fisica Cosmica - Sezione di Palermo, CNR, Via Ugo La Malfa 153, 90146 Palermo, Italy
² SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
³ University of Manchester, Jodrell Bank Observatory, Macclesfield, Cheshire SK11 9DL, UK
⁴ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁵ Dipartimento di Fisica, Universitá La Sapienza, Piazzale A. Moro 2, 00185 Roma, Italy; Istituto di Astrofisica Spaziale e Fisica Cosmica - Sezione di Roma, CNR, Via del Fosso del Cavaliere, 00100 Roma, Italy
⁶ ASTRON, Postbus 2, 7990 AA Dwingeloo, The Netherlands; Astronomical Institute “Anton Pannekoek", University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands

Corresponding author: G. Cusumano, giancarlo.cusumano@pa.iasf.cnr.it

Received: 1 July 2003
Accepted: 4 September 2003

Abstract

We present timing and spectral results of PSR B1937+21, the fastest known millisecond pulsar ( ms), observed with RXTE. The pulse profile, detected up to ~20 keV, shows a double peak with the main component much stronger than the other. The peak phase separation is and the pulsed spectrum over the energy range 2–25 keV is well described by a power law with a photon index equal to . We find that the X-ray pulses are closely aligned in phase with the giant pulses observed in the radio band. This results suggest that giant radio pulses and X-ray pulses originate in the same region of the magnetosphere due to a high and fluctuating electron density that occasionally emits coherently in the radio band. The X-ray events, however, do not show any clustering in time indicating that no X-ray flares are produced.