We present infrared (IR) photometry and spectroscopy of the Type II-P SN 2017eaw and its progenitor in the nearby galaxy NGC 6946. Progenitor observations in the Ks band in 4 epochs from 1 year to 1 day before the explosion reveal no significant variability in the progenitor star greater than 6% that last longer than 200 days. SN 2017eaw is a typical SN II-P with near-IR and mid-IR photometric evolution similar to those of SNe 2002hh and 2004et, other normal SNe II-P in the same galaxy. Spectroscopic monitoring between 389 and 480 days post explosion reveals strong CO first overtone emission at 389 d, with a line profile matching that of SN 1987A from the same epoch, indicating ∼10−3M⊙ of CO at 1,800 K. From the 389 d epoch until the most recent observation at 566 d, the first overtone feature fades while the 4.5 μm excess, likely from the CO fundamental band, remains. This behavior indicates that the CO has not been destroyed, but that the gas has cooled enough that the levels responsible for first overtone emissions are no longer populated. Finally, the evolution of Spitzer 3.6 μm photometry shows evidence for dust formation in SN 2017eaw, with a dust mass of 10−6 or 10−4M⊙ assuming carbonaceous or silicate grains respectively.
@article{arxiv.1901.01940,
title = {Supernova 2017eaw: molecule and dust formation from infrared observations},
author = {Samaporn Tinyanont and Mansi M Kasliwal and Kelsie Krafton and Ryan Lau and Jeonghee Rho and Douglas C Leonard and Kishalay De and Jacob Jencson and Dimitri Mawet and Maxwell Millar-Blanchaer and Ricky Nilsson and Lin Yan and Robert D Gehrz and George Helou and Schuyler D Van Dyk and Eugene Serabyn and Ori D Fox and Geoffrey Clayton},
journal= {arXiv preprint arXiv:1901.01940},
year = {2019}
}