2019ApJ...875...17K

We perform hydrodynamical simulations of the interaction between supernova (SN) ejecta and circumstellar medium (CSM) for SN 1993J and SN 2011dh, and calculate the radio and X-ray emissions expected from the shocked gas at late epochs (t). Considering the ejecta structure from multi-group radiation hydrodynamics simulation, we find that the observed rapid drop in radio and X-ray light curves of SN 1993J at t > 3000 days may be due to a change in the mass-loss rate ({dot}M) ∼6500 yr prior to the explosion of the SN. The exact epoch scales inversely with the assumed wind velocity of v_w = 10 kms^–1. The progenitor of this SN very likely belonged to a binary system, where, during its evolution, the primary had transferred material to the secondary. It is argued in this paper that the change in {dot}M can happen because of a change in the mass accretion efficiency (η) of the companion star. It is possible that before ∼6500 (v_w/10 kms^–1)^–1 yr prior to the explosion, η was high, and thus the CSM was tenuous, which causes the late-time downturn in fluxes. In the case of SN 2011dh, the late-time evolution is found to be consistent with a wind medium with {dot}M/v_w = 4 x 10^–6 M_☉yr^–1/10 kms^–1. It is difficult from our analysis to predict whether the progenitor of this SN had a binary companion; however, if future observations show a similar decrease in radio and X-ray fluxes, then this would give strong support to a scenario where both SNe had undergone a similar kind of binary evolution before explosion.