Use of the highly sensitive Hokupa ’ a/Gemini curvature wavefront sensor has allowed for the first time direct adaptive optics ( AO ) guiding on M8-M9 very low mass ( VLM ) stars .
An initial survey of 20 such objects ( SpT=M8-M9 ) discovered 4 binaries .
Three of the systems have separations of less than 4.2 AU and similar mass ratios ( \Delta K < 0.8 mag ; 0.85 < q < 1.0 ) .
One system , however , did have the largest \Delta K = 2.38 mag and sep = 14.4 AU yet observed for a VLM star with a brown dwarf companion .
Based on our initial flux limited ( Ks < 12 mag ) survey of 20 M8-M9 stars over 14 : 26 < RA < 4 : 30 hours from the sample of ( 11 ) we find a binary fraction in the range 14 - 24 \% for M8-M9 binaries with sep > 3 AU .
This is likely consistent with the 23 \pm 5 \% measured for more massive ( M0-M6 ) stars over the same separation range .
It appears M8-M9 binaries have a much smaller semi-major axis distribution peak ( \sim 4 AU ; with no systems wider than 15 AU ) compared to M and G stars which have a broad peak at larger \sim 30 AU separations .