Type IIn Supernova SN 2010jl: Optical Observations for Over 500 Days After Explosion

TL;DR

This paper presents detailed optical observations of supernova SN 2010jl over 1.5 years, revealing strong ejecta-CSM interaction, spectral asymmetries, and insights into the progenitor's massive pre-explosion mass loss.

Contribution

It provides the first extensive optical dataset for SN 2010jl and proposes a new interpretation of spectral asymmetries, challenging dust extinction explanations and suggesting a massive progenitor with significant pre-supernova mass loss.

Findings

SN 2010jl has one of the highest H_alpha luminosities among SNe IIn.

Spectral lines show increasing blueshift and asymmetry over time.

Progenitor likely experienced a massive, rapid mass loss before explosion.

Abstract

We present extensive optical observations of a Type IIn supernova (SN) 2010jl for the first 1.5 years after the discovery. The UBVRI light curves demonstrated an interesting two-stage evolution during the nebular phase, which almost flatten out after about 90 days from the optical maximum. SN 2010jl has one of the highest intrinsic H_alpha luminosity ever recorded for a SN IIn, especially at late phase, suggesting a strong interaction of SN ejecta with the dense circumstellar material (CSM) ejected by the progenitor. This is also indicated by the remarkably strong Balmer lines persisting in the optical spectra. One interesting spectral evolution about SN 2010jl is the appearance of asymmetry of the Balmer lines. These lines can be well decomposed into a narrow component and an intermediate-width component. The intermediate-width component showed a steady increase in both strength and blueshift with time until t ~ 400 days after maximum, but it became less blueshifted at t ~ 500 days when the line profile appeared relatively symmetric again. Owing to that a pure reddening effect will lead to a sudden decline of the light curves and a progressive blueshift of the spectral lines, we therefore propose that the asymmetric profiles of H lines seen in SN 2010jl is unlikely due to the extinction by newly formed dust inside the ejecta, contrary to the explanation by some early studies. Based on a simple CSM-interaction model, we speculate that the progenitor of SN 2010jl may suffer a gigantic mass loss (~ 30-50 M_sun) in a few decades before explosion. Considering a slow moving stellar wind (e.g., ~ 28 km/s) inferred for the preexisting, dense CSM shell and the extremely high mass-loss rate (1-2 M_sun per yr), we suggest that the progenitor of SN 2010jl might have experienced a red supergiant stage and explode finally as a post-red supergiant star with an initial mass above 30-40 M_sun.