The ASCA results of the starburst galaxy M82 are presented. The X-rays in the
0.5--10 keV band exhibit a thin thermal spectrum with emission lines from
highly ionized magnesium, silicon, and sulfur, as well as a hard tail extending
to higher than 10keV energy. The soft X-rays are spatially extended, while the
hard X-rays show an unresolved point-like structure with possible a long-term
flux variability. The flux ratio of the emission lines and the spatially
extended structure in the low-energy band indicate that at least
two-temperature thin thermal plasmas are present. The abundances of the oxygen,
neon, magnesium, silicon, sulfur, and iron in the thin thermal plasmas are
found to be significantly lower than the cosmic value. Neither type-Ia nor
type-II supernova explosions can reproduce the observed abundance ratio. The
origin of the unresolved hard X-rays is uncertain, but is probably an obscured
low-luminosity AGN.Comment: 25 pages, 8 figure
