The Solar Neighborhood.III.A Near-Infrared Search for Widely Separated Low-Mass Binaries

Abstract

A near-infrared survey designed to detect widely separated, very low-mass companions to M dwarfs within 8 pc is described. This survey is unique in that it is sensitive to companions with separations of 100-1400 AU from primaries and with masses down to the 0.03 M<SUB>sun</SUB>level, thereby sampling rarely explored parameter space. In Phase I of this program, described here, candidate stellar and brown dwarf companions are identified by creating color-magnitude plots of all detected point sources in the fields surrounding primaries and searching for objects that are bright enough to be stellar (M<SUB>j</SUB>≤11) or that fall close to theoretical brown dwarf isochrones like GD 165B (M<SUB>j</SUB>∼13). Common proper motion and spectroscopic checks are used to screen candidates. To date, all candidates for which we have made follow-up observations have been identified as background sources and no new low mass stellar or brown dwarf candidates have emerged from this survey. Phase II of this program will include a search for common proper motion between primaries and all field objects to M<SUB>j</SUB>∼ 17.5, allowing identification of widely separated substellar components, including objects like GL 229B.