Light-curve Modeling of Fast-evolving Supernova KSN 2015K: Explosion in Circumstellar Matter of a Super-AGB Progenitor

Recent supernova searches revealed a number of fast-evolving luminous transients. We perform radiation-hydrodynamic simulations of light curves of several models of supernova from super-asymptotic giant branch (super-AGB, SAGB) stars with low-mass envelopes (M _env ∼ 0.05-1.25 M _⊙). The differences in the light curves found among the models are used to link the observed events to the most appropriate models. In particular, we propose that KSN 2015K is an electron-capture supernova. We assume an “optically” thick circumstellar medium (CSM) around SAGB and the circumstellar interaction powers the peak luminosity of the light curve with a short rise time. The faint tail might be influenced by the spin-down luminosity of a newborn Crab-like pulsar. Our fits indicate an ejecta mass of 0.02-0.05 M _⊙, a CSM mass of 0.10-0.12 M _⊙, a radius of the CSM photosphere ∼10¹⁴ cm, a kinetic energy of ∼3 × 10⁵⁰ erg, a photospheric velocity v _ph ≳ 10,000 km s^-1, and a pulsar total spin energy (2.5-4) × 10⁴⁹ erg.