2025/04/06 by Raj Kumar, Subhasish Das, Kumar, Raj +1
Physics and Astronomy · #Astrophysical Phenomena and Observations #Stellar, planetary, and galactic studies #Astronomy and Astrophysical Research
paper · pdf · doi:10.48550/arxiv.2504.04601
We report the first spectro-polarimetric investigation of the bright Z-type source GX 349+2 using simultaneous observations of IXPE, NuSTAR and Swift/XRT. The source exhibited significant polarization in the 2-8 keV energy range during the flaring branch (FB) and normal branch (NB). The estimated polarization degree (PD) and polarization angle (PA) for FB are 1.74 ± 0.52% (3.3σ) and 19.4 ± 8.9^∘, respectively; while for NB, PD and PA are 0.8 ± 0.22% (3.6σ) and 35.4 ± 7.9^∘, respectively. The energy-resolved polarization for NB revealed an increase in PD from 0.78±0.2% (3.6σ) to 1.32±0.40% (3.3σ) and a change in PA from 17.9±8.1^∘, and 53.2±8.6^∘, in the energy range of 2-4 and 4-8 keV, respectively. Using the simultaneous observations of Swift/XRT and NuSTAR, we investigated the spectral properties of the source during NB, and the Western model well explained it. The spectra also depicted a strong and broad Fe Kα line. However, spectro-polarimetric analyses carried out by IXPE align closely with model-independent polarimetric results. We discuss results obtained from the polarimetric studies in the context of various coronal geometries, and we confirm the slab-like geometry in the NB for GX 349+2.