1998A&A...336L...1I

X-ray observations of the galaxy NGC 5194 (M 51) with the High Resolution Imager (HRI) onboard ROSAT were analysed to search for X-ray emission from the type Ic supernova 1994I. An X-ray source with a (0.1-2.4keV) luminosity of 1.6x10³⁸erg/s is found at the position of SN 1994I, 79-85 days after the explosion. We believe this to be the first detection of X-ray emission from a type I SN. Assuming the emission arises from shocked circumstellar gas, deposited by the progenitor through non-conservative mass-transfer to a companion, we estimate a constant gas density of ρ=2x10⁵cm^–3v₁₆₅₀₀^2/3 and a total mass of X-ray luminous gas of M=1x10^–3M_☉ inside a sphere of radius 1.2x10¹⁶cm. If the emission arises from the shocked stellar wind of the progenitor, heated by the outgoing wave, we derive a mass-loss rate prior to the outburst of {dot}(M) =3.6x10^–6M_☉/yr, similar to mass-loss rates of other type I SNe, inferred from radio observations.