Program: GN-2020B-FT-107

We performed a detailed model atmosphere analysis of more than 50,000 white dwarfs in the Montreal White Dwarf Database with Gaia DR2 parallaxes. We identify 3 objects with masses near the Chandrasekhar mass limit. We obtained follow-up spectroscopy of two of these targets as part of a Gemini DDT program in July 2020. However, one of these targets does not show hydrogen absorption features, indicating that it has a helium-dominated atmosphere. Here we propose to obtain follow-up spectroscopy of this target to constrain its atmospheric composition, including C/He ratio, to confirm its nature, and precisely constrain its temperature and mass. If confirmed, this object would be the most massive white dwarf ever found, it would provide an observational constraint on the Chandrasekhar limit, and experimentally constrain the upper limit for stellar cores that escape collapse into neutron stars.