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X-ray polarimetry is a powerful tool to probe the geometry of the hot X-ray corona in active galactic nuclei (AGN). Here, we present our results on the characterization of the X-ray polarization of the radio-quiet Seyfert-type AGN IC 4329A at a redshift of z = 0.016 . This is based on observations carried out by the Imaging X-ray Polarimeter (IXPE). IXPE observed IC 4329A during 5–15 January 2023, for a total observing time of 458 ks. From the model-independent analysis, we found a polarization degree ( Π X ) of 3.7 ± 1.5 % and a polarization position angle ( Ψ X ) of 61 ∘ ± 12 ∘ in the 2–8 keV energy range (at 68% confidence). This is also in agreement with the values of Π X and Ψ X of 4.7 ± 2.2 % and 71 ∘ ± 14 ∘ , respectively, obtained from spectro-polarimetric analysis of the I, Q and U Stokes spectra in the 2–8 keV energy band (at 90% confidence). The value of Π X in the 2–8 keV band obtained from the model-independent analysis is lower than the minimum detectable polarization (MDP) value of 4.5%. However, Π X obtained from spectro-polarimetric analysis in the 2–8 keV band is larger than the MDP value. In the 3–5 keV band, we found Π X of 6.5 ± 1.8 , which is larger than the MDP value of 5.5%. The observed moderate value of Π X obtained from the analysis of the IXPE data in the 3–5 keV band argues against a spherical lamp-post geometry for the X-ray corona in IC 4329A; however, considering simulations, the observed polarization measurements tend to favor a conical shape geometry for the corona. This is the first time measurement of X-ray polarization in IC 4329A. Measurements of the X-ray polarization in many such radio-quiet AGN will help in constraining the geometry of the X-ray corona in AGN. [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]

We present an in-depth analysis and results of eleven XMM–Newton data sets, spanning 2000–2016, of the anomalous X-ray Pulsar CXOU J010043.1−721134 that has been classified as a magnetar. We find a spin period of 8.0275(1) s as of December 2016 and calculate the period derivative to be (1.76 ± 0.02) × 10−11 s s−1, which translate to a dipolar magnetic field strength of 3.8 × 1014 G and characteristic age of ∼7200 yr for the magnetar. It has a double-peaked pulse profile, with one broad and one narrow peak, in both soft (0.3–1.3 keV) and hard (1.3–8 keV) energy bands. The pulse fractions in the two energy bands are found to be consistent with constant values. These results are in agreement with previously published results for this source. Although two-component models produce acceptable fits to its energy spectra, single component models are much simpler and are able to explain the similarity of the pulse profiles in the low- and high-energy bands. We attempt fitting with four different single-component models and find that the best fit to the spectra is obtained by fitting a thermal Comptonization model with the photon index (Γ) between 2.0 and 2.7, and the electron temperature (kT e) between 0.5 and 0.9 keV, for a seed blackbody photon distribution of 0.2 keV. Finally, we conclude by discussing our results briefly. [ABSTRACT FROM AUTHOR]