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TheMassandAgeofVeryLowMassMembersoftheOpen
ClusterαPersei
arXiv:astro-ph/9807145v1 14 Jul 1998GiborBasriandEduardoL.Mart´ nAstronomyDepartment,UniversityofCalifornia,Berkeley,CA94720e-mailaddresses:basri@soleil.berkeley.edu,ege@popsicle.berkeley.eduABSTRACTWepresentspectroscopicopticalandphotometricinfraredobservationsof12faintcandidatemembersoftheyoungopenclusterαPerseifoundbyProsserKeckHIRESechellespectraprovideradialandrotationalvelocitymeasurementsfor veobjects,twoofwhichareclearlynonmembersbasedontheradialvelocities.Thesekinematicnonmembersalsodonot twellinthe(V I)vs(I J)clustersequence.Oneadditionalfaintobjectislikelyanonmemberbasedonalow-resolutionspectrum.UsingHIRES,wehavesearchedfortheLiiresonanceline.Combiningtheabsence/presenceoflithiumandphotometryofthefaintαPerseitargetswithcon rmedmembershipconstrainstheiragesandmasses.ThelackoflithiuminAPJ0323+4853impliesitsageisgreaterthanabout65Myr,whichisolderthantheclusterclassicaluppermain-sequenceturno ageof50Myr.AsimilaragediscrepancyisfoundinthePleiades.Wedetectlithiuminthefaintestofourprogramstars,AP270,whichimpliesamassforitjustatthesubstellarmass
limit,givenouradoptedageanditsluminosity.ThemembershipofAP281isinquestionbecauseofitshighradialvelocitycomparedwiththeclustermean.OntheotherhandAP281liesonthephotometricclustersequence,andhasavery
highrotationvelocityandHαemission,indicatingyouth.Ifamember,itslack
oflithiumwouldpushtheminimumageoftheclusterto75Myr,inagreement
withaveryrecentuppermain-sequencedetermination.Inthatcase,AP270
wouldnotbeabrowndwarf.
Subjectheadings:openclustersandassociations:individual(αPersei)—stars:
low-mass,browndwarfs—stars:evolution—stars:fundamentalparameters
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