The γ-ray deposition histories of calcium-rich supernovae

Abstract

ABSTRACT Calcium-rich supernovae (Ca-rich SNe) are faint, rapidly evolving transients whose progenitor system is yet to be determined. We derive the γ-ray deposition histories of five Ca-rich SNe from the literature in order to place constraints on possible progenitor systems. We find that the γ-ray escape time, t0, of the Ca-rich SNe sample is $\approx 35\!-\!65 \, \rm {d},$ within the unoccupied region between Type Ia SNe and stripped-envelope supernovae (SESNe). The t0−MNi56 distribution of these SNe, where MNi56 is the synthesized 56Ni mass in the explosion, creates a continuum between the Type Ia and SESNe t0−MNi56 distribution, hinting at a possible connection between all the events. By comparing our results to models from the literature, we were able to determine that helium shell detonation models and core-collapse models of ultra-stripped stars are unlikely to explain Ca-rich SNe since the gamma-ray escape time in these models is smaller than the observed values. Models that agree with the observed t0−MNi56 distribution are explosions of low mass, $M\approx 0.75\!-\!0.8\, \mathrm{M}_\odot,$ white dwarfs and core-collapse models of stripped stars with an ejecta mass of $M\approx 1\!-\!3\, {\rm M}_{\odot}.$