Presentation #246.04 in the session Imaging X-ray Polarimetry Explorer: Initial results.
Soft gamma repeaters and anomalous X-ray pulsars are believed to host a magnetar, an ultra-magnetized neutron star with surface magnetic field B ~ 1014-1015 G. We report on the first detection of linearly polarized X-ray emission from a magnetar with the Imaging X-ray Polarimetry Explorer (IXPE). The IXPE observation of the anomalous X-ray pulsar 4U 0142+61 reveals a linear polarization degree of (12±1) % throughout the instrumental working energy band 2-8 keV at 15σ confidence level. The IXPE measurement demonstrates the power of X-ray polarimetry, giving us completely new information about the properties of the neutron star surface and magnetosphere and lending further support for the presence of the quantum mechanical effect of vacuum birefringence. On behalf of the IXPE Science Team: