Dust to Dust: 3 years in the Evolution of the Unusual SN 2008S

TL;DR

This study presents a three-year observational analysis of SN 2008S, revealing its fading optical brightness, persistent mid-IR emission from dust, and environmental clues suggesting a massive AGB star progenitor.

Contribution

It provides the first long-term multi-wavelength follow-up of SN 2008S, highlighting dust emission evolution and environmental context that inform its progenitor nature.

Findings

Optical emission is undetectable after 3 years.

Mid-IR emission remains brighter than progenitor, declining slowly.

Environment lacks massive stars, supporting AGB progenitor hypothesis.

Abstract

We obtained late-time optical and near-IR imaging of SN 2008S with the Large Binocular Telescope (LBT), near-IR data with the Hubble Space Telescope (HST), and mid-IR data with the Spitzer Space Telescope (SST). We find that (1) it is again invisible at optical (UBVR) wavelengths to magnitude limits of approximately 25 mag, (2) while detected in the near-IR (H) at approximately 24.8 mag, it is fading rapidly, and (3) it is still brighter than the progenitor at 3.6 and 4.5 microns in the mid-IR with a slow, steady decline. The IR detections in December 2010 are consistent with dust emission at a blackbody temperature of T ~ 640 K and a total luminosity of L ~ 200000 Lsun, much higher than the L ~ 40000 Lsun luminosity of the obscured progenitor star. The local environment also shows no evidence for massive (M >= 10 Msun) stars in the vicinity of the transient, consistent with the progenitor being a massive AGB star.