SN 1978K: An evolved supernova outside our Local Group detected at millimetre wavelengths

Abstract

Supernova 1978K is one of the oldest-known examples of the class of Type IIn supernovae that show evidence for strong interaction between the blast wave and a dense, pre-existing circumstellar medium. Here we report detections of SN 1978K at both 34 GHz and 94 GHz, making it only the third extragalactic supernova (after SN 1987A and SN 1996cr) to be detected at late-times at these frequencies. We find SN 1978K to be >400 times more luminous than SN 1987A at millimetre wavelengths in spite of the roughly nine year difference in ages, highlighting the risk in adopting SN 1987A as a template for the evolution of core-collapse supernovae in general. Additionally, from new VLBI observations at 8.4 GHz, we measure a deconvolved diameter for SN 1978K of ~5 milli-arcsec, and a corresponding average expansion velocity of <1500 km/s. These observations provide independent evidence of an extremely dense circumstellar medium surrounding the progenitor star.

4 pages, 4 figures, accepted for publication in Astronomy & Astrophysics Letters. Title and text updated to acknowledge prior detection of SN 1996cr at millimetre wavelengths

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Cited by in corpus (4)

• The landscape of binary core-collapse supernova progenitors and the late emergence of Wolf-Rayet winds
• First Detection of X-Ray Line Emission from Type IIn Supernova 1978K with XMM-Newton's RGS
• The X-ray Decay of the ultraluminous supernova SN 1978K in NGC 1313
• ALMA, ATCA, and Spitzer Observations of the Luminous Extragalactic Supernova SN 1978K