Program: GS-2018B-FT-107

Supernova (SN) 2016gkg is one of the most interesting and best-observed transient events of the recent years. Our previous study of this object, based on unprecedentedly early discovery data and detection of a candidate progenitor star, suggested that it originated from an interacting binary system with the possible presence of circumstellar matter. Through subsequent HST imaging we found evidence that the SN ejecta may have entered a phase of strong interaction with a surrounding medium. Here we propose to obtain a spectrum in order to verify this suggestion and to study the properties of such a medium. The observations are essential to complete our thorough analysis of the SN, which aims at improving our knowledge of mass-loss processes in massive stars and their evolutionary paths toward a SN explosion.