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In this paper, we performed a spectro-polarimetric analysis of the transient NS-LMXB XTE J1701−462 using IXPE, NICER , and NuSTAR data during its 2022 outburst. We report significant detection of energy-dependent polarization in the X-ray signal from the source on 2022 September 29 in the 2–4, 4–8, and 2–8 keV energy bands with a polarization degree of 3.9 ± 0.3, 5.5 ± 0.6, and 4.5 ± 0.4 per cent, respectively. The polarization angle in the overall 2–8 keV band was ∼143° ± 2°. The spectra were modelled using a combination of thermal emission from an accretion disc, Comptonized emission from a hot electron plasma (or corona) and a Gaussian line. From spectro-polarimetric analysis, the polarization degree due to the disc emission had an upper limit of ∼11.5 per cent, and that of the Comptonized emission was constrained at 7.7 ± 2.5 per cent (at the 3σ level). The results suggest that the Comptonized component probably originates from a spreading-layer/boundary-layer above the neutron star surface. IXPE observation of the source on 2022 October 8 does not show significant polarization which can be attributed to a weakening of the coronal Comptonized emission. The implication of these results are discussed. [ABSTRACT FROM AUTHOR]

We present a detailed spectro-polarimetric study of black hole X-ray binary 4U 1630−47 during its 2022 outburst with IXPE and NICER observations. The source is observed in disc dominated thermal state (kT in ≈ 1.4 keV) with clear detection of absorption features at 6.69 ± 0.01 keV and 6.97 ± 0.01 keV from both NICER as well as IXPE spectra, likely indicating a coupling of disc-wind. A significant degree of polarization (PD) |$= 8.33\pm 0.17~{{\ \rm per\ cent}}$| and polarization angle (PA) =17.78° ± 0.60° in the energy range of 2 − 8 keV are measured with IXPE. PD is found to be an increasing function of energy whereas PA remains roughly same within the energy range. Simultaneous energy spectra from NICER in the range of 0.5 − 12 keV are modelled to study the spectral properties. Furthermore, the spin parameter of the black hole is estimated with spectro-polarimetric data as a |$_{\ast }=0.920\pm 0.001\, (1\sigma)$| which is corroborated by NICER observations. Finally, we discuss the implications of our findings. [ABSTRACT FROM AUTHOR]

We have carried out the first spectro-polarimetric study of the bright NS-LMXB GX 9+9 using IXPE and AstroSat observations. We report a significant detection of polarization of |$1.7\pm 0.4~{{\ \rm per\ cent}}$| over the 2–8 keV energy band, with a polarization angle of 63° ± 7°. The polarization is found to be energy-dependent, with a 3σ polarization degree consistent with null polarization in 2–4 keV, and 3.2 per cent in 4–8 keV. Typical of the spectra seen in NS-LMXBs, we find that a combination of soft thermal emission from the accretion disc and Comptonized component from the optically thick corona produces a good fit to the spectra. We also attempt to infer the individual polarization of these components, and obtain a 3σ upper limit of |$\sim 11~{{\ \rm per\ cent}}$| on the polarization degree of the thermal component, and constrain that of the Comptonized component to |$\sim 3~{{\ \rm per\ cent}}$|⁠. We comment on the possible corona geometry of the system based on our results. [ABSTRACT FROM AUTHOR]