The mass and age of very low mass members of the open cluster alpha Persei

We present spectroscopic optical and photometric infrared observations of 1 2 faint candidate members of the young open cluster alpha Persei found by P resser in 1994. Kecb HIRES echelle spectra provide radial and rotational ve locity measurements for five objects, two of which are clearly nonmembers b ased on the radial velocities. These kinematic nonmembers also do not lit w ell in the (V-I) versus (I-J) cluster sequence. One additional faint object is likely a nonmember based on a low-resolution spectrum. Using HIRES, we have searched for the Li I resonance line. Combining the absence/presence o f lithium and photometry of the faint a Persei targets with confirmed membe rship constrains their ages and masses. The lack of lithium in AP J0323+485 3 implies that its age is greater than about 65 Myr, which is older than th e cluster classical upper main-sequence turnoff age of 50 Myr. A similar ag e discrepancy is found in the Pleiades. We detect lithium in the faintest o f our program stars, AP 270, which implies a mass for it just at the subste llar mass limit, given our adopted age and its luminosity. The membership o f AP 281 is in question because of its high radial velocity compared with t he cluster mean. On the other hand, AP 281 lies on the photometric cluster sequence and has a very high rotation velocity and H alpha emission, indica ting youth. If it is a member, its lack of lithium would push the minimum a ge of the cluster to 75 Myr, in agreement with a very recent upper main-seq uence determination. In that case, AP 270 would not be a brown dwarf.