We report initial observations and analysis on the Type IIb SN~2016gkg in the nearby galaxy NGC~613. SN~2016gkg exhibited a clear double-peaked light curve during its early evolution, as evidenced by our intensive photometric follow-up campaign. SN~2016gkg shows strong similarities with other Type IIb SNe, in particular with respect to the \he~emission features observed in both the optical and near infrared. SN~2016gkg evolved faster than the prototypical Type~IIb SN~1993J, with a decline similar to that of SN~2011dh after the first peak. The analysis of archival {\it Hubble Space Telescope} images indicate a pre-explosion source at SN~2016gkg's position, suggesting a progenitor star with a ∼mid F spectral type and initial mass 15−20\msun, depending on the distance modulus adopted for NGC~613. Modeling the temperature evolution within 5days of explosion, we obtain a progenitor radius of ∼48−124\rsun, smaller than that obtained from the analysis of the pre-explosion images (240−320\rsun).
@article{arxiv.1611.00419,
title = {The progenitor and early evolution of the Type IIb SN 2016gkg},
author = {L. Tartaglia and M. Fraser and D. J. Sand and S. Valenti and S. J. Smartt and C. McCully and J. P. Anderson and I. Arcavi and N. Elias-Rosa and L. Galbany and A. Gal-Yam and J. B. Haislip and G. Hosseinzadeh and D. A. Howell and C. Inserra and S. W. Jha and E. Kankare and P. Lundqvist and K. Maguire and S. Mattila and D. Reichart and K. W. Smith and M. Smith and M. Stritzinger and M. Sullivan and F. Taddia and L. Tomasella},
journal= {arXiv preprint arXiv:1611.00419},
year = {2017}
}