Study of the cyclotron feature in MXB 0656-072

¹ School of Physics & Astronomy, University of Southampton, Highfield, SO17 1BJ, UK e-mail: vanessa@astro.soton.ac.uk
² Department of Physics, University of Warwick, Coventry CV4 7AL, UK
³ Institut für Astronomie und Astrophysik – Astronomie, Sand 1, 72076 Tübingen, Germany
⁴ INTEGRAL Science Data Centre, 16 Ch. d'Écogia, 1290 Versoix, Switzerland
⁵ Center for Astrophysics and Space Sciences, University of California at San Diego, La Jolla, CA 92093-0424, USA
⁶ Space Sciences Laboratory, University of California at Berkeley, Berkeley, CA 94702-7450, USA

⁷ European Space Astronomy Centre (ESAC), European Space Agency, PO Box 50727, 28080, Madrid, Spain

Received: 22 September 2005
Accepted: 26 January 2006

Abstract

We have monitored a type II outburst of the Be/X-ray binary MXB 0656-072 in a series of pointed RXTE observations during October through December 2003. The source spectrum shows a cyclotron resonance scattering feature at keV, corresponding to a magnetic field strength of G and is stable through the outburst and over the pulsar spin phase. The pulsar, with an average pulse period of s, shows a spin-up of 0.45 s over the duration of the outburst. From optical data, the source distance is estimated to be kpc and this is used to estimate the X-ray luminosity and a theoretical prediction of the pulsar spin-up during the outburst.