Light curve and spectral evolution of the Type IIb SN 2011fu

TL;DR

This study presents detailed photometric and spectroscopic analysis of the Type IIb supernova 2011fu, revealing its light curve evolution, spectral features, and progenitor characteristics, with implications for understanding supernova explosion mechanisms.

Contribution

It provides the first comprehensive modeling of SN 2011fu's light curve and spectra, estimating progenitor properties and explosion parameters, which were not previously characterized in detail.

Findings

Progenitor had an extended low-mass hydrogen envelope and a dense helium core.

Nickel mass synthesized was approximately 0.21 solar masses.

Early spectral line velocities declined and stabilized after day 40.

Abstract

We present the low-resolution spectroscopic and UBVRI broad-band photometric investigations of the Type IIb supernova 2011fu, discovered in UGC 01626. The photometric follow-up of this event has been initiated a few days after the explosion and covers a period of about 175 days. The early-phase light curve shows a rise followed by steep decay in all bands and shares properties very similar to that seen in case of SN 1993J, with a possible detection of the adiabatic cooling phase. Modelling of the quasi-bolometric light curve suggests that the progenitor had an extended ($\sim 1 \times 10^{13}$ cm), low-mass ($\sim 0.1$ $M_\odot$) H-rich envelope on top of a dense, compact ($\sim 2 \times 10^{11}$ cm), more massive ($\sim$ 1.1 $M_\odot$) He-rich core. The nickel mass synthesized during the explosion was found to be $\sim$ 0.21 $M_\odot$, slightly larger than seen in case of other Type IIb SNe. The spectral modelling performed with SYNOW suggests that the early-phase line velocities for H and Fe\,{\sc ii} features were $\sim 16000$ km s$^{-1}$ and $\sim 14000$ km s$^{-1}$, respectively. Then the velocities declined up to day +40 and became nearly constant at later epochs.