Anatomy of the AGN in NGC 5548. III. The high-energy view with NuSTAR and INTEGRAL
Harrison, F.; Kriss, G. A.; Bianchi, S.; Cappi, M.; Costantini, E.; Mehdipour, M.; Paltani, S.; Ponti, G.; Petrucci, P. -O.; Steenbrugge, K. C.; Peterson, B. M.; De Marco, B.; Matt, G.; Ursini, F.; Walton, D. J.; Kaastra, J.; Boissay, R.; di Gesu, L.
France, Italy, Switzerland, Netherlands, United States, Germany, United Kingdom, Chile
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.