Anatomy of the AGN in NGC 5548

III. The high-energy view with NuSTAR and INTEGRAL

¹ Univ. Grenoble Alpes, IPAG, 38000 Grenoble, France
e-mail: francesco.ursini@obs.ujf-grenoble.fr
² CNRS, IPAG, 38000 Grenoble, France
³ Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
⁴ Department of Astronomy, University of Geneva, 16 Ch. d’Ecogia, 1290 Versoix, Switzerland
⁵ INAF-IASF Bologna, via Gobetti 101, 40129 Bologna, Italy
⁶ SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
⁷ Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
⁸ Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109, USA
⁹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
¹⁰ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹¹ Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218, USA
¹² Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK
¹³ Department of Astronomy, The Ohio State University, 140 W 18th Avenue, Columbus, OH 43210, USA
¹⁴ Center for Cosmology & AstroParticle Physics, The Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210, USA
¹⁵ Instituto de Astronomia, Universidad Católica del Norte, Avenida Angamos 0610, Casilla 1280, Antofagasta, Chile
¹⁶ Department of Physics, University of Oxford, Keble Road, Oxford, OX1 3RH, UK

Received: 25 November 2014
Accepted: 12 January 2015

Abstract

We describe the analysis of the seven broad-band X-ray continuum observations of the archetypal Seyfert 1 galaxy NGC 5548 that were obtained with XMM-Newton or Chandra, simultaneously with high-energy (>10 keV) observations with NuSTAR and INTEGRAL. These data were obtained as part of a multiwavelength campaign undertaken from the summer of 2013 till early 2014. We find evidence of a high-energy cut-off in at least one observation, which we attribute to thermal Comptonization, and a constant reflected component that is likely due to neutral material at least a few light months away from the continuum source. We confirm the presence of strong, partial covering X-ray absorption as the explanation for the sharp decrease in flux through the soft X-ray band. The obscurers appear to be variable in column density and covering fraction on time scales as short as weeks. A fit of the average spectrum over the range 0.3–400 keV with a realistic Comptonization model indicates the presence of a hot corona with a temperature of 40⁺⁴⁰_-10 keV and an optical depth of 2.7^+0.7_-1.2 if a spherical geometry is assumed.