X-ray polarization observations of IC 4329A with IXPE: Constraining the geometry of X-ray corona
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Cited by 3 publications
References 53 publications
Spectro-polarimetric study to constrain accretion-ejection properties of MCG-5-23-16 using IXPE and NuSTAR observations
We conducted a study on the X-ray polarisation properties of MCG-5-23-16 by analysing long-term monitoring data from NuSTAR jointly with IXPE observations made in May and November 2022. The re-analysis of IXPE data gives model-dependent polarisation degree, PD (%) = $1.08\pm0.66$ in the energy band 2–8 keV, which agrees with previous studies within error bars. The model-independent analysis of PD poses an upper limit of $\leq3.8$ ( $1\sigma$ level) for the same energy band. The observed upper limit of PD, along with broadband spectral analysis (2–79 keV) using an accretion-ejection based model, allowed us to derive the corona geometry (i.e. radius and height) and the accretion disc inclination ( $\sim33^\circ$ ). Additional NuSTAR observations were also analysed to gain insights into the accretion flow properties of the source and to estimate the expected polarisation during those epochs with PD $\sim 4.3\%$ . The radius and height of the corona varies between $28.2\pm3.1 - 39.8\pm4.6$ r $_s$ and $14.3\pm1.7-21.4\pm1.9$ r $_s$ respectively, with a mass outflow rate from the corona measuring $0.14\pm0.03-0.2\pm0.03$ Eddington rate ( $\dot m_{\mathrm{Edd}}$ ). The estimated PD values were nearly constant up to a certain radial distance and height of the corona and then decreased for increasing corona geometry. The spectral analysis further provided an estimate for the mass of the central black hole $\sim2\times 10^7$ M $_\odot$ and the velocity of the outflowing gas $\sim0.16-0.19c$ . A comparative broadband spectral study using reflection-based models estimates the disc inclination between $\sim 31^\circ\pm8^\circ-45^\circ\pm7^\circ$ , and yields an expected PD of 3.4–6.0%. We also found a weak reflection fraction and a less ionised distant reflecting medium. The expected PD measured using accretion-ejection and reflection models is less compared to the expected PD measured for a given disc inclination of $45^\circ$ . Our modelling of the disc-corona-outflows and polarisation connection can be extended and validated with data from the recently launched XPoSat, India’s first X-ray Polarimeter Satellite, offering potential applications to other sources.
Spectro-polarimetric study to constrain accretion-ejection properties of MCG-5-23-16 using IXPE and NuSTAR observations
We conducted a study on the X-ray polarisation properties of MCG-5-23-16 by analysing long-term monitoring data from NuSTAR jointly with IXPE observations made in May and November 2022. The re-analysis of IXPE data gives model-dependent polarisation degree, PD (%) = $1.08\pm0.66$ in the energy band 2–8 keV, which agrees with previous studies within error bars. The model-independent analysis of PD poses an upper limit of $\leq3.8$ ( $1\sigma$ level) for the same energy band. The observed upper limit of PD, along with broadband spectral analysis (2–79 keV) using an accretion-ejection based model, allowed us to derive the corona geometry (i.e. radius and height) and the accretion disc inclination ( $\sim33^\circ$ ). Additional NuSTAR observations were also analysed to gain insights into the accretion flow properties of the source and to estimate the expected polarisation during those epochs with PD $\sim 4.3\%$ . The radius and height of the corona varies between $28.2\pm3.1 - 39.8\pm4.6$ r $_s$ and $14.3\pm1.7-21.4\pm1.9$ r $_s$ respectively, with a mass outflow rate from the corona measuring $0.14\pm0.03-0.2\pm0.03$ Eddington rate ( $\dot m_{\mathrm{Edd}}$ ). The estimated PD values were nearly constant up to a certain radial distance and height of the corona and then decreased for increasing corona geometry. The spectral analysis further provided an estimate for the mass of the central black hole $\sim2\times 10^7$ M $_\odot$ and the velocity of the outflowing gas $\sim0.16-0.19c$ . A comparative broadband spectral study using reflection-based models estimates the disc inclination between $\sim 31^\circ\pm8^\circ-45^\circ\pm7^\circ$ , and yields an expected PD of 3.4–6.0%. We also found a weak reflection fraction and a less ionised distant reflecting medium. The expected PD measured using accretion-ejection and reflection models is less compared to the expected PD measured for a given disc inclination of $45^\circ$ . Our modelling of the disc-corona-outflows and polarisation connection can be extended and validated with data from the recently launched XPoSat, India’s first X-ray Polarimeter Satellite, offering potential applications to other sources.
XMM-Newton – NuSTAR monitoring campaign of the Seyfert 1 galaxy IC 4329A
We present the results of a joint and campaign on the active galactic nucleus (AGN) IC 4329A, consisting of 9 times 20\,ks observations, and 5 times 20\,ks observations within nine days, performed in August 2021. Within each observation, the AGN is not very variable, and the fractional variability never exceeds 5<!PCT!>. Flux variations are observed between the different observations on timescales of days, with a ratio of 30<!PCT!> of the minimum and maximum 2--10\,keV flux. These variations follow the softer-when-brighter behavior typically observed in AGN. In all observations, a soft excess is clearly present. Consistently with previous observations, the X-ray spectra of the source exhibit a cutoff energy between 140 and 250\,keV that is constant within the error in the different observations. We detected a prominent component of the $6.4$\,keV Fe Kalpha line consistent with being constant during the monitoring, consisting of an unresolved narrow core and a broader component likely originating in the inner accredion disk. We find that the reflection component is weak max and most likely originates in distant neutral medium. We also found a warm absorber component together with an ultrafast outflow. Their energetics show that these outflows have enough mechanical power for significant feedback on the environment of the AGN.
X-ray view of dissipative warm corona in active galactic nuclei
Detections of the X-ray spectra of active galactic nuclei (AGNs) typically reveal a noticeable excess of soft X-rays beyond the extrapolation of the power-law trend observed between 2 and 10 keV. However, the cause of this surplus remains unclear. In the scenario of soft Comptonization, observations suggest a warm corona temperature, ranging from 0.1 to 1 keV, and an optical depth of approximately 10 to 30. Furthermore, according to radiative constraints derived from spectral analyses employing Comptonization models, it has been suggested that most of the accretion power is released within the warm corona. At the same time, the disk beneath it is largely non-dissipative, mainly emitting the reprocessed radiation from the corona. We tested the dissipative warm corona model using the radiative transfer code TITAN-NOAR on a sample of 82 XMM-Newton EPIC-pn observations of 21 AGNs. Based on a spectral modeling of the X-ray data, we aim to estimate the total amount of internal heating inside the warm corona on top of the accretion disk. By modeling the 0.3--10 keV EPIC-pn spectra with the TITAN-NOAR model component, we estimated the internal heating and optical depth of the warm corona and checked their correlations with such global parameters as the hot corona spectral index, black hole mass, and accretion rate. From the model normalization, we computed the radial extent of the warm corona on top of the cold accretion disk. Our model infers the presence of dissipative warm corona, with optical depths distributed across the range of sim 6--30 and a total internal heating in the range of sim 1--29 times 10$^ $\,cm3. We do not detect any variation between these properties and global properties, such as the black hole mass and accretion rate. The extent of the warm corona is spread across a broad range, from 7--408 gravitational radii, and we find that the warm corona is more extended for higher accretion rates. Soft excess emission is ubiquitous across a wide mass range and accretion rate in AGNs. We confirm that the warm corona responsible for producing the soft X-ray excess is highly dissipative with greater optical depths being associated with lower internal heating and vice versa. The cold standard accretion disk regulates the extent of the warm corona.
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