DISCOVERY OF A BINARY BROWN DWARF AT 2 pc FROM THE SUN

I am using multi-epoch astrometry from the Wide-field Infrared Survey Explorer (WISE) to search for new members of the solar neighborhood via their high proper motions. Through this work, I have identified WISE J104915.57–531906.1 as a high proper motion object and have found additional detections in images from the Digitized Sky Survey, the Two Micron All-Sky Survey, and the Deep Near-Infrared Survey of the Southern Sky. I have measured a parallax of 0496 ± 0037 (2.0 ± 0.15 pc) from the astrometry in these surveys, making WISE J104915.57–531906.1 the third closest system to the Sun. During spectroscopic observations with the Gemini Multi-Object Spectrograph at Gemini Observatory, an i-band acquisition image resolved it as a 15 (3 AU) binary. A spectrum was collected for the primary, which I classify as L8 ± 1. The secondary is probably near the L/T transition as well given that it is only modestly fainter than the primary (Δi = 0.45 mag).

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