A NEW PLEIADES MEMBER AT THE LITHIUM SUBSTELLAR BOUNDARY

We present the discovery of an object in the Pleiades open cluster, na med Teide 2, with optical and infrared photometry that places it on th e cluster sequence slightly below the expected substellar mass limit. We have obtained low-and high-resolution spectra that allow us to dete rmine its spectral type (M6), radial velocity, and rotational broadeni ng and to detect H alpha in emission and Li I in absorption. All the o bserved properties strongly support the membership of Teide 2 in the P leiades. This object has an important role in defining the reappearanc e of lithium below the substellar limit in the Pleiades. The age of th e Pleiades' very low mass members, based on their luminosities and the absence or presence of lithium, is constrained to be in the range 100 -120 Myr.