Program: GN-2018B-FT-111

The latest unbiased 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 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, allowing us to understand its composition and measure critical physical parameters such as temperature, density, and mass. We propose to use Gemini to obtain deep nebular spectra of three Type I SLSNe classified as part of our effort to identify low redshift SLSNe in ongoing time-domain surveys. This will represent a ~25% increase in the sample of SLSNe observed >100 days after maximum light.