Coronal properties of low-accreting AGNs using Swift, XMM–Newton, and NuSTAR observations

Abstract

ABSTRACT We studied the broad-band X-ray spectra of Swift/Burst Alert Telescope selected low-accreting active galactic nuclei (AGNs) using the observations from XMM–Newton, Swift, and NuSTAR in the energy range of 0.5–150 keV. Our sample consists of 30 AGNs with Eddington ratio, λEdd < 10−3. We extracted several coronal parameters from the spectral modelling, such as the photon index, hot electron plasma temperature, cutoff energy, and optical depth. We tested whether there exist any correlation/anticorrelation among different spectral parameters. We observe that the relation of hot electron temperature with the cutoff energy in the low accretion domain is similar to what is observed in the high accretion domain. We did not observe any correlation between the Eddington ratio and the photon index. We studied the compactness–temperature diagram and found that the cooling process for extremely low-accreting AGNs is complex. The jet luminosity is calculated from the radio flux, and observed to be related to the bolometric luminosity as $L_{\rm jet} \propto L_{\rm bol}^{0.7}$, which is consistent with the standard radio-X-ray correlation.