The rate of Supernovae from the combined sample of five searches

TL;DR

This study combines data from five supernova searches to estimate supernova rates across galaxy types, revealing differences in rates among types and challenging previous claims about certain supernova subclasses.

Contribution

It provides new supernova rate estimates based on a combined sample, clarifies the rarity of certain supernova subclasses, and supports the idea of different progenitor ages in galaxy types.

Findings

Most SNe occur in late spiral galaxies with type II dominance.

SN Ib/c are rarer than SN Ia, contradicting previous high-rate claims.

Faint SNe do not constitute the majority of explosions.

Abstract

With the purpose to obtain new estimates of the rate of supernovae we joined the logs of five SN searches, namely the Asiago, Crimea, Cal{\'a}n-Tololo and OCA photographic surveys and the visual search by Evans (the sample counts 110 SNe). We found that the most prolific galaxies are late spirals in which most SNe are of type II (0.88 SNu). SN Ib/c are rarer than SN Ia (0.16 and 0.24 SNu, respectively), ruling out previous claims of a very high rate of SNIb/c. We also found that the rate of SN Ia in ellipticals (0.13 SNu) is smaller than in spirals, supporting the hypothesis of different ages of the progenitor systems in early and late type galaxies. Finally, we estimated that even assuming that separate classes of faint SN Ia and SN II do exist (SNe 1991bg and 1987A could be the respective prototypes) the overall SN rate is raised only by 20-30%, therefore excluding that faint SNe represent the majority of SN explosions. Also, the bright SNIIn are intrinsically very rare (2 to 5% of all SNII in spirals).