X-ray supernova remnants in the starburst region of M82
  We searched for X-ray supernova remnants (SNRs) in the starburst region of
M82, using archival data from the Chandra X-ray Observatory with a total
effective exposure time of 620 ks with an X-ray spectroscopic selection. Strong
line-emission from Fe xxv at 6.7 keV is a characteristic spectral feature of
hot, shocked gas of young SNRs and distinctive among the discrete sources in
the region populated by X-ray binaries. We selected candidates using
narrow-band imaging aimed at the line excess and identified six (and possibly a
seventh) X-ray SNRs. Two previously known examples were recovered by our
selection. Five of them have radio counterparts, including the radio supernova
SN2008iz, which was discovered as a radio transient in 2008. It shows a hard
X-ray spectrum with a blueshifted Fe K feature with v ~ -2700 km/s, both of
which suggest its youth. The 4-8 keV luminosities of the selected SNRs are in
the range of (0.3-3)e38 erg/s. We made a crude estimate of the supernova rate,
assuming that more luminous SNRs are younger, and found 0.06 (0.03-0.13) /yr,
in agreement with the supernova rates estimated by radio observations and the
generally believed star formation rate of M82, although the validity of the
assumption is questionable. A sum of the Fe xxv luminosity originating from the
selected X-ray SNRs consists of half of the total Fe xxv luminosity observed in
the central region of M82. We briefly discuss its implications for starburst
winds and the Fe xxv emission in more luminous starburst galaxies.
