Optical observations of the fast declining type Ib supernova iPTF13bvn

TL;DR

This study presents detailed optical observations of the fast-declining type Ib supernova iPTF13bvn, revealing its explosion characteristics, progenitor constraints, and low luminosity compared to typical supernovae.

Contribution

It provides the first comprehensive optical photometry and spectroscopy analysis of iPTF13bvn, estimating its nickel mass, ejecta mass, and kinetic energy, and constraining its progenitor type.

Findings

Fast decline rate with Δm15(B)=1.82.

Peak absolute V-band magnitude of -17.23.

Synthesized approximately 0.09 solar masses of 56Ni.

Abstract

We present optical UBVRI photometry and medium resolution spectroscopy of the type Ib supernova iPTF13bvn, spanning a phase of $\sim$ $-13\,$d to $+71\,$d with respect to $B$-band maximum. The post maximum decline rates indicate a fast decline with $\Delta m_{15}(B) = 1.82$. Correcting for a galactic extinction $E(B-V){\rm_{MW}}=0.045$ and host galaxy extinction of $E(B-V){\rm_{host}}=0.17$, the absolute $V$-band magnitude peaks at M$_V=-17.23\, \pm \,0.20$. The bolometric light curve indicates that $\sim 0.09$ M$_{\odot}$ of $^{56}$Ni was synthesized in the explosion. The earliest spectrum ($-13$d) shows the presence of He~{\sc i} 5876 \AA\ feature at a velocity of $\sim$15000 km s$^{-1}$, which falls rapidly by the time the SN approaches the epoch of B-band maximum. The photospheric velocity near maximum light, as indicated by the Fe~{\sc ii} 5169~\AA\ feature, is $\sim 9000$ km s$^{-1}$. The estimate for the $^{56}$Ni mass, together with the estimates for the ejected mass ($M_{\rm{ej}}$) and kinetic energy of the explosion ($E_{\rm{k}}$) indicate that iPTF13bvn is a low luminosity type Ib supernova, with a lower than average ejected mass and kinetic energy. Our results suggest that the progenitor of iPTF13bvn is inconsistent with a single Wolf-Rayet star.