A long life of excess: The interacting transient SN 2017hcc

In this study we present the results of a five-year follow-up campaign of the long-lived type IIn supernova SN 2017hcc, found in a spiral dwarf host of near-solar metallicity. The long rise time (57 +/- 2 days, ATLAS o band) and high luminosity (peaking at -20.78 +/- 0.01 mag in the ATLAS o band) point towards an interaction of massive ejecta with massive and dense circumstellar material (CSM). The evolution of SN 2017hcc is slow, both spectroscopically and photometrically, reminiscent of the long-lived type IIn, SN 2010jl. An infrared (IR) excess was apparent soon after the peak, and blueshifts were noticeable in the Balmer lines starting from a few hundred days, but appeared to be fading by around +1200 d. We posit that an IR light echo from pre-existing dust dominates at early times, with some possible condensation of new dust grains occurring at epochs greater than or similar to+800 d.

Automated summary

We present the five-year follow-up campaign of the long-lived type IIn supernova SN 2017hcc, which was found in a spiral dwarf host of near-solar metallicity. The supernova shows a slow evolution both spectroscopically and photometrically, similar to SN 2010jl. The infrared excess and blueshifts in the Balmer lines suggest the presence of an IR light echo and the condensation of new dust grains at later epochs.