The X-Ray Polarimetry View of the Accreting Pulsar Cen X-3

Abstract The first X-ray pulsar, Cen X-3, was discovered 50 yr ago. Radiation from such objects is expected to be highly polarized due birefringence of plasma and vacuum associated with propagation photons in the presence strong magnetic field. Here we present results observations X-3 performed Imaging Polarimetry Explorer. source exhibited significant flux variability observed two states different by a factor ∼20 flux. In low-luminosity state, no polarization found either pulse phase-averaged (with 3 σ upper limit 12%) or phase-resolved (the limits are 20%–30%) data. bright degree 5.8% ± 0.3% angle 49.°6 1.°5 significance about 20 were measured spectropolarimetric analysis showed anticorrelation between degree, as well variations angle. fit rotating vector model indicates position pulsar spin axis 49° obliquity 17°. detected relatively low can explained if layers neutron star surface overheated accreted matter conversion modes occurs within transition region hot layer cooler underlying atmosphere. A fraction signal also produced reflection radiation accretion curtain.