Einstein X-ray observations of the Monoceros supernova remnant.

The Monoceros nebula is seen in the optical and radio wavelengths as a ring of 3.5° angular diameter and is believed to be an old supernova remnant (SNR). The authors report the first positive detection of X-rays from the Monoceros nebula, confirming its supernova remnant nature. Reprocessed Einstein imaging proportional counter observations of soft X-rays (0.2 - 5 keV) were used to produce a contour map of the surface brightness distribution.