First X-Ray and Radio Polarimetry of the Neutron Star Low-mass X-Ray Binary GX 17+2

Abstract We report the first polarimetric results of the neutron star low-mass X-ray binary Z-source GX 17+2 using the Imaging X-ray Polarimetry Explorer (IXPE) and the Very Large Array (VLA). We find that the X-ray source was polarized at PD = 1.9% ± 0.3% (1 σ errors) with a polarization angle of PA = 11° ± 4° (1 σ errors). Simultaneous Nuclear Spectroscopic Telescope Array observations show that the source was in the normal branch during our IXPE observations. The X-ray spectropolarimetry results suggest a source geometry comprising an accretion disk component, a Comptonization component, and a reflection component. The VLA radio polarization study shows a PD = 2.2% ± 0.2% with a Faraday-corrected intrinsic polarization angle of 1° ± 5°, which is an indication of the jet axis. Thus, we find the estimated X-ray PA from the source is consistent with the radio PA. We discuss the accretion geometry of the Z-source in light of our X-ray spectropolarimetry and radio findings.