The coronal temperature of NGC 4388 and NGC 2110 measured with INTEGRAL

Abstract

We aim to measure the physical properties of the hot X-ray corona of two active galactic nuclei, NGC 4388 and NGC 2110. We analysed the hard X-ray (20-300 keV) INTEGRAL spectrum in conjunction with archival XMM-Newton and NuSTAR data. The X-ray spectrum of both sources is phenomenologically well described by an absorbed cut-off power law. In agreement with previous results, we find no evidence of a Compton reflection component in these sources. We obtain a high-energy cut-off of $200_{-40}^{+75}$ keV for NGC 4388 and $320_{-60}^{+100}$ keV for NGC 2110. A fit with a thermal Comptonisation model yields a coronal temperature of $80_{-20}^{+45}$ keV and $75_{-15}^{+20}$ keV, respectively, and an optical depth of approximately two, assuming a spherical geometry. The coronal temperature and luminosity of both sources are consistent with pair production that acts as a thermostat for the thermal plasma. These results emphasise the importance of good signal-to-noise X-ray data above 100 keV to probe the high-energy emission of AGNs.

10 pages, 9 figures, accepted for publication in A&A; added missing references