A strong excess in the 20-100 kev emission of ngc 1365

Abstract

We present a new Suzaku observation of the obscured active galacticnucleus in NGC 1365, revealing an unexpected excess of X-rays above 20keV of at least a factor similar to 2 with respect to the extrapolationof the best-fitting 3-10 keV model. Additional Swift-BAT andIntegral-IBIS observations show that the 20-100 keV is concentratedwithin similar to 1.5 arcmin from the center of the galaxy, and is notsignificantly variable on timescales from days to years. A comparisonof this component with the 3-10 keV emission, which is characterized bya rapidly variable absorption, suggests a complex structure of thecircumnuclear medium, consisting of at least two distinct componentswith rather different physical properties, one of which covers >80% ofthe source with a column density N-H similar to 3-4x10(24) cm(-2). Analternative explanation is the presence of a double active nucleus inthe center of NGC 1365.