Isabel Caballero Institut für Astronomie und Astrophysik Tübingen (Germany) PhD Student I got a degree in Physics at the Universidad Complutense in Madrid in 2005. Then I did a trainee project at ESAC for 6 months under the supervision of Marcus Kirsch, working on XMM EPIC-pn timing calibration. I am doing now a PhD at the Institut für Astronomie und Astrophysik (Tübingen) in the X-ray and Gamma-Ray Astronomy group. I am working on accreting X-ray pulsars, under the supervision of Andrea Santangelo. At the moment I am studying observations of the Be/X-ray binary A 0535+26 during a recent outburst observed with RXTE and INTEGRAL, with special interest on the cyclotron resonance scattering features (cyclotron lines) observed. Those lines are seen in the spectra of many X-ray pulsars and are up to now the only direct way to measure the magnetic field of a neutron star, and therefore can be used to study the physical conditions of the emitting region. Peter Kretschmar from the INTEGRAL team is deeply involved in my PhD project.