X-Ray and Radio Polarimetry of the Neutron Star Low-mass X-Ray Binary GX 13+1

We report the X-ray and radio polarization study of the neutron star low-mass X-ray binary (LMXB) GX 13+1 using the Imaging X-ray Polarimetry Explorer (IXPE) and Very Large Array. Simultaneous Neutron Star Interior Composition Explorer observations show that the source was in parts of the Z state during our IXPE observations, exhibiting moderate changes in the hardness–intensity diagram. The source exhibits X-ray dips in the light curve along with hints of polarization swings between the dip and nondip states. The X-ray spectropolarimetry results suggest a source geometry comprising an accretion disk component representing the softer disk emission, along with a blackbody representing the harder emission from the boundary layer or a spreading layer. We investigate the geometry of GX 13+1 by considering our X-ray and radio polarization findings.