Adaptive optics imaging of the MBM 12 association Seven binaries and an edge - on disk in a quadruple system ⋆

We report adaptive optics (AO) observations of the young and nearby association MBM 12 obtained with the Canada-France-Hawaii Telescope. Our main observational result is the discovery of six new binary and the confirmation of HD 17332, already known as a binary. We also detected a possible quadruple system. It is composed of the close binary LkHα 263 AB (separation of ∼ 0.41 ′′), of LkHα 262 located ∼ 15.25 ′′ from LkHα 263 A, and of LkHα 263 C, located ∼ 4.1 ′′ from LkHα 263 A. A preliminary study of the binary fraction suggests a binary excess in the MBM 12 association as compared to the field and IC 348. Because of the high binarity rate, previous estimations of spectral types and measurements of IR excesses for several candidate members of MBM 12 have to be revised. LkHα 263 C is a nebulous object that we interpret as a disk oriented almost perfectly edge-on and seen in scattered light. This object has already been reported by Jayawardhana et al. (2002). Scattered light models allow us to estimate some of the structural parameters (i.e. inclination, diameter and to a lesser extent dust mass) of the circumstellar disk. We find an inclination of 89 o and a outer radius for the disk, ∼ 165 AU if the distance to MBM 12 is 275 pc. With the present data set, we do not attempt to reassess the distance to MBM 12. We estimate however that the distance to the candidate member RX J0255.3+1915 is d > 175 pc.