Preprint typeset using LATEX style emulateapj v. 5/2/11 A WOLF IN SHEEPSKIN: EXTRAORDINARY SUPERNOVA 2012AU VEILED BEHIND ORDINARY RADIO EMISSION

Abstract

We present extensive radio and X-ray observations of SN 2012au, the energetic radio luminous supernova of type Ib that may be a link between subsets of hydrogen-poor superluminous and normal core-collapse supernovae. The observations closely follow models of synchrotron emission from shock heated circum-burst medium that has a wind density profile (ρ ∝ r−2). We infer a sub-relativistic velocity for the shock wave v ≈ 0.2 c and a radius of r ≈ 1.4 × 1016 cm at 25 days after the estimated date of explosion. For a constant wind velocity of 1000 km/s we determine the constant mass loss rate of the progenitor to be M ̇ = 3.6 × 10−6 M yr−1, consistent with the estimates from X-ray observations. We estimate the total internal energy of the radio emitting material to be E ≈ 1047 erg, which is intermediate to SN 1998bw and SN 2002ap. Evolution of the radio light curves of SN 2012au is consistent with interaction with a smoothly distributed circum-burst medium and absence of stellar shells ejected from previous outbursts out to r ≈ 1017 cm from the supernova site. Based on this we conclude that the evolution of the SN 2012au progenitor star was relatively quiet during the final years preceding explosion. We find that the bright radio emission from SN2012au was not dissimilar from other core collapse supernovae despite it’s extraordinary optical properties. We speculate that it was the nature of the explosion that led to the unusual demise of the SN2012au progenitor star