INTEGRAL observes the 2007 outburst of the Be transient SAX J2103.5+4545

TL;DR

This study analyzes the spectral and temporal evolution of the 2007 outburst of the Be/X-ray transient SAX J2103.5+4545 using INTEGRAL data, revealing variable pulse profiles, significant spin-down, and estimating the neutron star's magnetic field.

Contribution

It provides the first detailed spectral and timing analysis of the 2007 outburst, including measurements of pulse period derivatives and magnetic field estimation.

Findings

Pulse profiles vary with time and energy.

Largest spin-down observed for SAX J2103.5+4545 since discovery.

Estimated neutron star magnetic field between 1.6 and 3 x 10^{13} G.

Abstract

We performed a detailed study of the 2007 outburst of the 352s pulsar SAXJ2103.5+4545, a Be/X-ray transient observed by INTEGRAL, to study its spectral and temporal properties during the evolution of the outburst. SAXJ2103.5+4545 was observed with IBIS/ISGRI from 25 to 27 April 2007 and from 6 to 8 May 2007. The 20-100keV spectrum is well described by a bremsstrahlung model with a temperature kT = 24keV. The pulse profiles are variable with time and energy. A pulse period derivative of pdot = -3.4E-7 s/s has been observed during the outburst. Instead, a spin-down of pdot = 5.5E-9 s/s is observed between the 2007 outburst reported here and the previous one occurred in December 2004. This is the largest spin-down measured for SAXJ2103.5+4545 since its discovery. We estimate a neutron star magnetic field in the range (1.6-3)E13 G using the Ghosh & Lamb torque model.