Research Note

High-energy pulse profile of the transient X-ray pulsar SAX J2103.5+4545

¹ CEA Saclay, DSM/DAPNIA/Service d'Astrophysique (CNRS FRE 2591), 91191 Gif-sur-Yvette, France e-mail: mfalanga@cea.fr
² Dipartimento di Scienze Fisiche ed Astronomiche, Università di Palermo, via Archirafi 36, 90123 Palermo, Italy
³ Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone, Italy

Received: 29 September 2004
Accepted: 26 February 2005

Abstract

Two recent INTEGRAL papers report a timing and spectral analysis of the transient Be/X-ray pulsar SAX J2103.5+4545 at high energies (5–200 keV). In this work we present for the first time a study of the pulse profile at energies above 20 keV using INTEGRAL data. The spin-pulse profile shows a prominent (with a duty cycle of 14%) and broad (with a FWHM of ~51 s) peak and a secondary peak which becomes more evident above 20 keV. The pulsed fraction increases with energy from ~45% at 5–40 keV to ~80% at 40–80 keV. The morphology of the pulse profile also changes as a function of energy, consistent with variations in the spectral components that are visible in the pulse phase resolved spectra. A study of the double peaked profile shows that the difference in the two peaks can be modeled by a different scattering fraction between the radiation from the two magnetic poles.