On the triple peaks of SNHunt248 in NGC 5806
Sollerman, J.; Jerkstrand, A.; Smartt, S. J.; Chambers, K. C.; Kankare, E.; Smith, K. W.; Flewelling, H.; Kotak, R.; Fremling, C.; Kuncarayakti, H.; Fraser, M.; Elias-Rosa, N.; Mattila, S.; Tomasella, L.; Magnier, E.; Bruce, A.; Pastorello, A.; Kangas, T.; Huber, M.; Harmanen, J.; Magee, M.; Polshaw, J.
United Kingdom, Italy, Finland, United States, Sweden, Spain, Chile
Abstract
We present our findings on a supernova (SN) impostor, SNHunt248, based on optical and near-IR data spanning ~15 yr before discovery, to ~1 yr post-discovery. The light curve displays three distinct peaks, the brightest of which is at MR ~ -15.0 mag. The post-discovery evolution is consistent with the ejecta from the outburst interacting with two distinct regions of circumstellar material. The 0.5-2.2 μm spectral energy distribution at -740 d is well-matched by a single 6700 K blackbody with log (L/L⊙) ~ 6.1. This temperature and luminosity support previous suggestions of a yellow hypergiant progenitor; however, we find it to be brighter than the brightest and most massive Galactic late-F to early-G spectral type hypergiants. Overall the historical light curve displays variability of up to ~ ± 1 mag. At current epochs (~1 yr post-outburst), the absolute magnitude (MR ~ - 9 mag) is just below the faintest observed historical absolute magnitude ~10 yr before discovery.
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