X-Ray Observations of the Starburst Galaxy M82

Abstract

We report here on long (~ 10^5^ s) X-ray observations of the starburst galaxy M82 with the European X-ray satellite EXOSAT. The observations with the low-energy imaging instrument confirm that there is extended X-ray emission from above and below the disk, with an overall extent perpendicular to the disk of almost 6' corresponding to 6 kpc. We present one of the best defined X-ray spectra yet of a starburst galaxy. The medium energy instrument measurements can be fitted with a power-law spectrum, consistent with inverse Compton emission, or with thermal emission from optically thin hot gas of a temperature of 9^+9^_-4_ keV. Using, in addition, the earlier Einstein HRI and MPC observations, we discuss the possible origin of the X-ray emission.