The NuSTAR View of the Seyfert 2 Galaxy NGC 4388

Abstract

We present an analysis of NuSTAR X-ray observations in the 3–79 keV energy band of the Seyfert 2 galaxy NGC 4388, taken in 2013. The broadband sensitivity of NuSTAR , covering the Fe K α line and Compton reflection hump, enables tight constraints to be placed on reflection features in AGN X-ray spectra, thereby providing insight into the geometry of the circumnuclear material. In this observation, we found the X-ray spectrum of NGC 4388 to be well described by a moderately absorbed power law with non-relativistic reflection. We fit the spectrum with phenomenological reflection models and a physical torus model and find the source to be absorbed by Compton-thin material ( N H  = (6.5 ± 0.8) × 10 23 cm −2 ) with a very weak Compton reflection hump ( R  < 0.09) and an exceptionally large Fe K α line eV) for a source with weak or no reflection. Calculations using a thin-shell approximation for the expected Fe K α EW indicate that an Fe K α line originating from Compton-thin material presents a possible explanation.