Slow pulsating accreting neutron stars: the enigmatic case of 4U 2206+54

The discovery of pulsations (Pspin5500s) has solved the controversy on thenature of the compact object in the HMXB 4U2206+54 but has prompted newquestions. According to spin evolutionary models such slow pulsations requirethe system to harbor a magnetar (Bvirgul1e14 G). However, the significant detectionof a cyclotron resonant scattering feature at 30 keV implies a magnetic fieldBvirgul3x1e12 G. Another unsolved question is whether the presence of a soft thermalcomponent, representing emission from the polar caps, is present in allaccreting pulsars. This proposal seeks to estimate the magnetic field strengththrough the neutron star spin evolution and investigate with unprecedenteddetail the soft energy spectrum of 4U2206+54 to check whether the polar cap scenario is applicable. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]