Program: GN-2017A-FT-6

WISE 0855 is the coldest known brown dwarf with an effective temperature of ~250 K. We have successfully obtained an M band spectrum using GNIRS on Gemini North, and here we propose to measure an L band spectrum, which will provide important and complementary information to M band. While M band probes water vapor absorption, water ice clouds, and phosphine, L band probes the other two most important absorbers in a cold atmosphere: methane and ammonia. Combined, a spectrum across L and M bands will motivate theoretical studies and improvements to models of frigid atmospheres, a critical step before the launch of JWST.