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

¹ INAF-Osservatorio di astrofisica e scienza dello spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
e-mail: francesco.ursini@inaf.it
² INAF-Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere, 00133 Roma, Italy
³ School of Physics and Astronomy, University of Southampton, SO17 1BJ Southampton, UK

Received: 9 July 2019
Accepted: 2 August 2019

Abstract

Aims. We aim to measure the physical properties of the hot X-ray corona of two active galactic nuclei, NGC 4388 and NGC 2110.

Methods. We analysed the hard X-ray (20–300 keV) INTEGRAL spectrum in conjunction with archival XMM–Newton and NuSTAR data.

Results. 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⁺⁴⁰ 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.