ASCA observations of the starburst galaxy M82

The ASCA spectrum of M82 is fit by three components: a soft component (0.32 keV), a medium one (0.95 keV), and a hard one (13.8 keV). The presence of fine emission indicates that the soft and the medium components are due to gas heated by the starburst activity. The abundances of O, Ne, Mg, Si and S are lower than the solar values and the abundance ratios cannot be reproduced by a combination of SN Ia and II. Imaging analysis shows the hard component is point-like, but the soft and medium components are extended. Long term variability from Uhuru to ASCA by a factor of 2 similar to 4 is detected in the hard component. Additionally, the temperature of the hard component obtained with ASCA is 13.8 keV, significantly higher than the Ginga value of 5.75 keV. These results suggest that M82 may contain a nuclear activity similar to that seen in AGN.