A deep Chandra image of M101 allowed the detection of SN 1970G 35yrs after its explosion, making it the oldest supernova detected in X-rays [73]. The deep observation allowed detection of the object with a relatively low luminosity, LX = (1.1 ± 0.2) x 1037 erg s-1. This luminosity is consistent with a mass loss rate of (2.6 ± 0.4) x 10-5(vw/10kms-1)[email protected] yrs-1. Its long term X-ray light curve, reconstructed from archival observations, is steep compared with those of most X-ray SNe, with a profile Lx < t(2 7±0 9). The soft Chandra spectrum (kT < 2 keV) is interpreted as arising in the reverse shock region. As the oldest supernova detected in X-rays, the SN 1970G detection is important, because it begins to bridge the observational gap between supernovae and supernova remnants (the youngest of which, Cas A, is 340-years-old), and offers hope that other old SNe can be detected.

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