LBA observations for project V253 semester 2019OCTS

We propose LBA observations of supernova 1996cr in the Circinus Galaxy, the strongest optically-identified radio supernova ever discovered and only ~4 Mpc away. MeerKAT found a total flux density of 107 mJy at 1.3 GHz in 2018. Although SN1996cr is now fading quickly, it remains bright enough for LBA observations. SN1996cr is one of the very few supernova observable with VLBI more than 20 yr after the explosion. Similarly to SN1987A, as well as many other SNe, SN1996cr exploded in a low density bubble surrounded by a high density shell of material swept up from a previous mass-loss phase, although it is ~1000x more radio luminous than SN1987A. Due to its radio brightness and nearness, SN1996cr presents an ideal case to study the mass-loss of a massive star through the SN-CSM interaction, for which a key constraint is knowing the shock radius and velocity, and the morphology of the interaction region. Our earlier LBA observations showed a complex morphology, although due to a resolved calibrator and poor uv-coverage, the VLBI images remain somewhat ambiguous. We will switch to a new, unresolved calibrator and combine observations at 2.3 and 4.8 GHz to increase our uv-coverage, The proposed observations will allow us to determine whether SN1996cr is shell-like, axi-symmetric, or perhaps centre-filled with some emission due to the stellar remnant of the explosion, and to determine a reliable and representative estimate of the forward-shock radius velocity.