The Candidate Progenitor of the Type IIn SN 2010jl is Not an Optically Luminous Star

TL;DR

This study uses late-time HST imaging to show that the pre-explosion blue source near SN 2010jl was not the progenitor star, suggesting it was part of a young cluster and indicating a massive progenitor.

Contribution

It provides new constraints on the progenitor of SN 2010jl by demonstrating the pre-explosion source was not the star itself, refining progenitor models for Type IIn supernovae.

Findings

Pre-explosion blue source is offset from the SN position by 24 pc.

The blue source is not the progenitor star, but possibly a young cluster.

Progenitor likely a massive (>30 solar masses) star.

Abstract

The nature of the progenitor star (or system) for the Type IIn supernova (SN) subclass remains uncertain. While there are direct imaging constraints on the progenitors of at least four Type IIn supernovae, one of them being SN 2010jl, ambiguities remain in the interpretation of the unstable progenitors and the explosive events themselves. A blue source in pre-explosion HST/WFPC2 images falls within the 5 sigma astrometric error circle derived from post-explosion ground-based imaging of SN 2010jl. At the time the ground-based astrometry was published, however, the SN had not faded sufficiently for post-explosion HST follow-up observations to determine a more precise astrometric solution and/or confirm if the pre-explosion source had disappeared, both of which are necessary to ultimately disentangle the possible progenitor scenarios. Here we present HST/WFC3 imaging of the SN 2010jl field obtained in 2014 and 2015, when the SN had faded sufficiently to allow for new constraints on the progenitor. The SN, which is still detected in the new images, is offset by 0."099 +/- 0."008 (24 +/- 2 pc) from the underlying and extended source of emission that contributes at least partially, if not entirely, to the blue source previously suggested as the candidate progenitor in the WFPC2 data. This point alone rules out the possibility that the blue source in the pre-explosion images is the exploding star, but may instead suggest an association with a young (<5-6 Myr) cluster and still argues for a massive (>30 solar masses) progenitor. We obtain new upper limits on the flux from a single star at the SN position in the pre-explosion WFPC2 and Spitzer/IRAC images that may ultimately be used to constrain the progenitor properties.