Optical photometry and spectroscopy of the type Ibn supernova SN 2006jc until the onset of dust formation

TL;DR

This study presents optical photometry and spectroscopy of supernova SN 2006jc, revealing details about its helium-rich circumstellar environment and early dust formation, with results comparable to normal Ib/c supernovae.

Contribution

First detailed optical data of SN 2006jc until dust formation, highlighting the properties of its helium-rich circumstellar shell and dust formation onset.

Findings

Helium lines indicate a dense, helium-rich circumstellar shell.

Dust formation evidenced by a sharp decline in brightness around day 50.

Optical light curves resemble those of normal Ib/c supernovae.

Abstract

We present optical UBVRI photometric and spectroscopic data of the type Ibn supernova SN 2006jc, until the onset of the dust forming phase. The optical spectrum shows a blue continuum and is dominated by the presence of moderately narrow (velocity ~2500 km/s) He I emission lines superimposed over a relatively weak supernova spectrum. The helium lines are produced in a pre-existing He rich circumstellar shell. The observed helium line fluxes indicate the circumstellar shell is dense, with a density of ~10^9 - 10^{10} cm^{-3}. The helium mass in this shell is estimated to be <~0.07 Msun. The optical light curves show a clear signature of dust formation, indicated by a sharp decrease in the magnitudes around day 50, accompanied by a reddening of the colours. The evolution of the optical light curves during the early phase and that of the uvoir bolometric light curve at all phases is reasonably similar to normal Ib/c supernovae.