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Name:Isabel Caballero


Institution:CEA Saclay


Country:France




Title:A 0535+26: cyclotron line evolution during its recent 2011 giant   outburst




Abstract:The Be/X-ray binary A0535+26 has shown three giant outbursts since 2005, after a long period of quiescence. The giant outbursts in 2005 (~5.2 Crab, 15-50 keV range) and 2009 (~5.6 Crab) could not be observed by most X-ray observatories due to Sun observing constraints. Finally, a giant outburst in February 2011,  that reached a flux of ~3.8 Crab, was monitored with INTEGRAL and Swift TOO observations.

A0535+26 is a highly magnetized accreting neutron star, with a magnetic field of ~4x10^12 G, derived from the cyclotron lines present  in the X-ray spectrum of the source at ~45 and ~100 keV. Cyclotron lines are very powerful tools: not only they provide the only direct way to determine a neutron star's magnetic field, but their dependence on the X-ray luminosity can also be used as a test to probe the accretion theory. For A0535+26 no significant variation of the cyclotron line with the X-ray luminosity has been observed.

We will present first results of the INTEGRAL and Swift observations
of the recent February 2011 outburst, with a special focus on the  cyclotron lines present in the X-ray spectrum of the source. The evolution of the cyclotron line with the luminosity will be studied in detail for the first time during a giant outburst of the source.








            

            
            

              

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