Hard X-rays and Fluorescent Iron Emission from the Embedded Infrared Cluster in NGC 2071

Abstract

We present first results of XMM-Newton X-ray observations of the infrared cluster lying near the NGC 2071 reflection nebula in the Orion B region. This cluster is of interest because it is one of the closest regions known to harbor embedded high-mass stars. We report the discovery of hard X-ray emission from the dense central NGC 2071-IR subgroup which contains at least three high-mass young stellar objects (NGC 2071 IRS-1, IRS-2, and IRS-3). A prominent X-ray source is detected within 1 arcsecond of the infrared source IRS-1, which is thought to drive a powerful bipolar molecular outflow. The X-ray spectrum of this source is quite unusual compared to the optically thin plasma spectra normally observed in young stellar objects (YSOs). The spectrum is characterized by a hard broad-band continuum plus an exceptionally broad emission line at approximately 6.4 keV from neutral or near-neutral iron. The fluorescent Fe line likely originates in cold material near the embedded star (i.e. a disk or envelope) that is irradiated by the hard heavily-absorbed X-ray source.