Program: GN-2017B-FT-5

The latest untargeted optical time-domain surveys have led to the discovery of rare and extreme transients such as superluminous supernovae (SLSNe). The mechanism that powers the hydrogen-poor Type I SLSNe remains elusive, though models such as a magnetar central engine and interaction with a hydrogen-poor medium are both major contenders. One of the most promising observational methods available to test these models is to track the SN evolution into the nebular phase, when the ejecta are optically thin. We propose to use Gemini to obtain a deep optical spectrum during the nebular phase of PS16fgt, a Type I SLSN that shows unusual spectroscopic features and was discovered as part of our search for low redshift SLSNe with Pan-STARRS. Obtaining a nebular phase spectrum of this SLSN will allow us to understand its composition and measure critical physical parameters such as temperature, density, and mass, which will help distinguish between the proposed power sources. This observation will contribute a new event to our effort to build a sample of diverse SLSNe with nebular phase spectra.