Discovery of five very low mass close binaries, resolved in the visible with lucky imaging

Abstract

We survey a sample of 32 M5-M8 stars with distance 1 were found, even though our survey is sensitive to Am ≤ 5 (well into the brown dwarf regime). The distribution of orbital radii is in broad agreement with previous results, with most systems at 1-5 au, but one detected binary is very wide at 46.8 ± 5.0 au. We also serendipitously imaged for the first time a companion to Ross 530, a metal-poor single-lined spectroscopic binary. We used the new Lucky Imaging system, LuckyCam, on the 2.5-m Nordic Optical Telescope to complete the 32 very low mass star Sloan Digital Sky Survey (SDSS) i' and z' survey in only 5 h of telescope time.