H-poor type IIb SN 2020bio LCs & spectra

SN2020bio displays a rapid and long-lasting initial decline throughout the first week of its light curve, similarly to other well-studied Type IIb SNe. This early-time emission is thought to originate from the cooling of the extended outer hydrogen-rich (H-rich) envelope of the progenitor star that is shock heated by the SN explosion.

We compare SN 2020bio to a sample of other double-peaked Type IIb SNe in order to investigate its progenitor properties. Analytical model fits to the early-time emission give progenitor radius (~100-1500R_{sun}_) and H-rich envelope mass (~0.01-0.5M_{sun}_) estimates that are consistent with other Type IIb SNe. However, SN 2020bio displays several peculiarities, including (1) weak H spectral features indicating a greater amount of mass loss than other Type IIb progenitors; (2) an underluminous secondary light-curve peak that implies a small amount of synthesized ^56^Ni (M_Ni_~0.02M_{sun}_); and (3) low-luminosity nebular [OI] and interaction-powered nebular features.