A spectroscopically normal type Ic supernova from a very massive progenitor

TL;DR

SN 2011bm is a spectroscopically normal Type Ic supernova with an unusually slow evolution, originating from a very massive progenitor star of 30-50 solar masses, with detailed analysis of its light curve and spectra.

Contribution

This study provides detailed observational data and analysis of SN 2011bm, revealing its slow evolution and massive progenitor, which enhances understanding of Type Ic supernovae from very massive stars.

Findings

SN 2011bm had a 40-day rise time to peak brightness.

Ejected mass estimated between 7-17 solar masses.

Progenitor star likely had an initial mass of 30-50 solar masses.

Abstract

We present observations of the Type Ic supernova (SN Ic) 2011bm spanning a period of about one year. The data establish that SN 2011bm is a spectroscopically normal SN Ic with moderately low ejecta velocities and with a very slow spectroscopic and photometric evolution (more than twice as slow as SN 1998bw). The Pan-STARRS1 retrospective detection shows that the rise time from explosion to peak was 40 days in the R band. Through an analysis of the light curve and the spectral sequence, we estimate a kinetic energy of 7-17 foe and a total ejected mass of 7-17 Mo, 5-10 Mo of which is oxygen and 0.6-0.7 Mo is 56Ni. The physical parameters obtained for SN 2011bm suggest that its progenitor was a massive star of initial mass 30-50 Mo. The profile of the forbidden oxygen lines in the nebular spectra show no evidence of a bi-polar geometry in the ejected material.