* Astronomy

Title: The progenitor and early evolution of the Type IIb SN 2016gkg
Author: L. Tartaglia, M. Fraser, D.J. Sand, S. Valenti, S. J. Smartt, C. McCully, J. P. Anderson, I. Arcavi, N. Elias-Rosa, L. Galbany, A. Gal-Yam, J.B. Haislip, G. Hosseinzadeh, D. A. Howell, C. Inserra, S. W. Jha, E. Kankare, P. Lundqvist, K. Maguire, S. Mattila, D. Reichart, K. W. Smith, M. Smith, M. Stritzinger, M. Sullivan, F. Taddia, L. Tomasella

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 spectroscopic and photometric follow-up campaign. SN 2016gkg shows strong similarities with other Type IIb SNe, in particular with respect to the \he emission features observed ~9days after explosion 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. 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. Modelling the temperature evolution within 5days of explosion, we obtain a progenitor radius of ~60-120 solar radii, consistent with the spectral type obtained from the pre-explosion images.

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ATel 9573: Further Classification of SN 2016gkg as a Probable Type IIb Supernova

ATel 9556: Radio Non-Detection of SN 2016gkg 

ATel 9536: Progenitor Candidate for SN 2016gkg in NGC 613