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Astron. Astrophys. 336, L1-L4 (1998)

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Letter to the Editor

Evidence for X-ray emission from the type Ic supernova 1994I

S. Immler, W. Pietsch, and B. Aschenbach

Max-Planck-Institut für Extraterrestrische Physik, Postfach 1603, D-85740 Garching, Germany

Received 19 May 1998 / Accepted 3 June 1998


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 (0.1-2.4 keV) luminosity of [FORMULA] erg s-1 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 [FORMULA] and a total mass of X-ray luminous gas of [FORMULA] inside a sphere of radius [FORMULA] cm. 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 [FORMULA], similar to mass-loss rates of other type I SNe, inferred from radio observations.

Key words: supernovae: general – supernovae: individual: SN 1994I – galaxies: individual: NGC 5194 (M 51) – X-rays: galaxies – X-rays: general

Send offprint requests to: S. Immler (e-mail: simmler@mpe.mpg.de)

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© European Southern Observatory (ESO) 1998

Online publication: July 7, 1998