Brown Dwarfs and the TW Hydrae Association

摘要

I report the results of a survey for low-mass (0.030 M☉ M 0.013 M☉) brown dwarfs in the direction of the TW Hya association using the Two Micron All Sky Survey (2MASS). Two late M dwarfs show signs of low surface gravity and are strong candidates to be young, very low mass (M ≈ 0.025 M☉) brown dwarfs related to the TW Hya association. The object 2MASSW J1207334-393254 is particularly notable for its strong Hα emission. The number of detected brown dwarfs is consistent with the substellar mass function in richer star formation environments. Newly identified late M and L dwarfs in the field are also discussed. Unusual objects include an L dwarf with strong Hα emission, a possible wide M8-M9 triple system, and a possible L dwarf companion to an LHS star.