X-ray spectro-polarimetric characterization of GX 340+0 in the horizontal branch: a highly inclined source?

Abstract

We report the first detection of X-ray polarization in the horizontal branch for GX 340+0 as obtained by Imaging X-ray Polarimetry Explorer (IXPE). A polarization degree of 4.3%$\pm$0.3% is obtained. This value is in agreement with the previous polarization measurements of Z-sources in the horizontal branch. Spectro-polarimetric analysis, performed using a broad-band spectral model obtained by NICER and NuSTAR quasi-simultaneous observations, allowed us to constrain the polarization for the soft and hard spectral components typical to these sources. The polarization angle for the two components differs by $\sim 40°$. This result could be explained by a misalignment of the NS rotations axis with respect to the accretion disk axis. We provide a comparison of the results with polarization expected in different models. Theoretical expectations for the polarization of the disk and the Comptonization components favor an orbital inclination for GX 340+0 higher than 60°, as expected for Cyg-like sources, in contrast with results we report for the reflection component using broad-band spectrum.

A&A 691, A253 (2024)

References in corpus (23)

• ixpeobssim: a Simulation and Analysis Framework for the Imaging X-ray Polarimetry Explorer
• Analyzing the Data from X-ray Polarimeters with Stokes Parameters
• Relativistic iron emission lines in neutron star low-mass X-ray binaries as probes of neutron star radii
• Design, Construction, and Test of the Gas Pixel Detectors for the IXPE Mission
• Handling Background in IXPE polarimetric data
• A weighted analysis to improve the X-ray polarization sensitivity of IXPE
• Relativistic X-ray Reflection Models for Accreting Neutron Stars
• Polarized X-rays from windy accretion in Cygnus X-1
• Accretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements
• Disk reflection signatures in the spectrum of the bright Z-source GX 340+0
• Discovery of strongly variable X-ray polarization in the neutron star low-mass X-ray binary transient XTE J1701$-$462
• Radius Constraints from Reflection Modeling of Cygnus X-2 with NuSTAR and NICER
• X-ray polarimetry and spectroscopy of the neutron star low-mass X-ray binary GX 9+9: an in-depth study with IXPE and NuSTAR
• Highly Significant Detection of X-Ray Polarization from the Brightest Accreting Neutron Star Sco X-1
• Analytical techniques for polarimetric imaging of accretion flows in Schwarzschild metric
• First detection of X-ray polarization from the accreting neutron star 4U 1820-303
• X-ray polarisation properties of thermal-radiative disc winds in binary systems
• X-Ray Polarized View on the Accretion Geometry in the X-Ray Binary Circinus X-1
• A connection between accretion states and the formation of ultra-relativistic outflows in a neutron star X-ray binary
• Discovery of a strong rotation of the X-ray polarization angle in the galactic burster GX 13+1
• New polarimetric study of the galactic X-ray burster GX 13+1
• On the illumination of neutron star accretion discs
• Evidence of hard power-law spectral cutoff and disc reflection features from the X-ray transient XTE J1739-285

Cited by in corpus (6)

• Polarized radiation from the spreading layer of the weakly magnetized neutron stars
• X-ray Dips and Polarization Angle Swings in GX 13+1
• X-ray polarization of Z-type neutron star low-mass X-ray binaries -- I. Model-independent, time-resolved X-ray polarimetry
• X-ray spectropolarimetric characterization of the Z-source GX 340+0 in the normal branch
• IXPE view of the Sco-like source GX 349+2 in the normal branch
• X-ray polarization of Z-type neutron star low-mass X-ray binaries -- II. Spectropolarimetric analysis