Keck Spectra of Brown Dwarf Candidates and a Precise Determi

We have identified twenty-seven candidate very low mass members of the relatively young Alpha Persei open cluster from a six square degree CCD imaging survey. Based on their I magnitudes and the nominal age and distance to the cluster, these objects should

TABLE1

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aSummaryofOpticalImagingforAlphaPerseiTelescopeAreaCoveredLimitingMagnitude(sq.degrees)(R/I)aBouvieretal.(1999)TABLE2PhotometryofAlphaPerseiStarsStarα(J2000)δ(J2000)IcR IcKIc K

aAP275isfromProsser(1994).Weincludeitherebecauseithappened

tofallinoneofour eldsandbecauseitisoneofthreestarswithKeck

spectrafromBM99

1

We have identified twenty-seven candidate very low mass members of the relatively young Alpha Persei open cluster from a six square degree CCD imaging survey. Based on their I magnitudes and the nominal age and distance to the cluster, these objects should

TABLE3

SpectroscopyofAlphaPerseiStarsa

Featurestrengths

AP165

AP284

AP296

AP268

AP322

AP312

AP313

AP314

AP310

AP311

AP275

AP318

AP316

AP323

AP300

AP324

AP317

AP315

AP301

AP325

AP326

AP3061.401.571.591.611.731.791.831.781.871.921.921.941.951.982.052.022.122.162.132.252.432.311.0030.9951.0061.0091.0171.0181.0191.0121.0251.0101.0221.0211.0311.0341.0221.041.0561.051.0571.071.091.15············1.401.49···1.631.641.60···1.701.71···1.761.78···1.861.902.062.272.37bWλ(Hα)1.521.821.871.911.952.002.032.032.062.102.102.112.122.142.182.192.242.262.272.342.442.45M3.3cM4.6cM4.7cM5M5.5M5.5···M5.5M6M6···M6M6···M6:M6.5···M6.5M6.5M7M7.5M83.86.35.83.45.89.65.8<2.3.85.79.38.75.87.77.45.55.35.97.86.57.:10.5FWHM(Hα)3.13.23.13.13.3···3.7···3.1···3.34.4···2.83.33.35.24.1···3.1···2.9r.v.-6.-3.5.-12-19.·········8.···-3.-2.···-1.-2.-14.···-13.···-14.···3.Wλ(LiI)<0.1<0.1<0.1<0.05<0.15···<0.10···<0.10···<0.20<0.10···0.60.51.00.5:0.4···0.9······Wλ(NaI)············7.08.1···7.17.65.8···5.76.1···6.26.8···5.96.26.17.56.2

We have identified twenty-seven candidate very low mass members of the relatively young Alpha Persei open cluster from a six square degree CCD imaging survey. Based on their I magnitudes and the nominal age and distance to the cluster, these objects should

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aKeckSpectraofBrownDwarfCandidatesandaPreciseDeterminationoftheLithiumDepletionBoundaryintheAlphaPerseiOpenCluster1JohnR.Stau er2SmithsonianAstrophysicalObservatory,60GardenSt.,Cambridge,MA02138(stau er@cfa.harvard.edu)DavidBarradoyNavascu´esMax-PlanckInstitutf¨urAstronomie,Heidelberg,D-69117Germany(barrado@mpia-hd.mpg.de)JeromeBouvierLaboratoired’Astrophysique,ObservatoiredeGrenoble,Universit´eJosephFourier,B.P.53,38041GrenobleCedex9,France,bouvier@gag.observ-gr.fr(jerome.bouvier@obs.ujf-grenoble.fr)HeatherL.Morrison3DepartmentofAstronomy,CaseWesternReserveUniversity,Cleveland,OH44106(heather@vegemite.astr.cwru.edu)

We have identified twenty-seven candidate very low mass members of the relatively young Alpha Persei open cluster from a six square degree CCD imaging survey. Based on their I magnitudes and the nominal age and distance to the cluster, these objects should

PaulHarding

StewardObservatory,UniversityofArizona,Tucson,AZ85726(harding@as.arizona.edu)

K.L.Luhman

SmithsonianAstrophysicalObservatory,60GardenSt.,Cambridge,MA02138

(kluhman@cfa.harvard.edu)

ThomasStankeandMarkMcCaughrean

AstrophysikalischesInstitutPotsdam,AnderSternwarte16,D14482PotsdamGermany

(tstanke@aip.de;mjm@aip.de)

DonaldM.Terndrup

AstronomyDept.,OhioStateUniversity,Columbus,OH43210

(terndrup@payne.mps.ohio-state.edu)

LoriAllen2

SmithsonianAstrophysicalObservatory,60GardenSt.,Cambridge,MA02138

(leallen@cfa.harvard.edu)

PatrickAssouad

InternationalSpaceUniversity,Parcd’Innovation,Blvd.Gonthierd’Andernach,67400

Illkirch,France(assouad@mss.isunet.edu)

Received

We have identified twenty-seven candidate very low mass members of the relatively young Alpha Persei open cluster from a six square degree CCD imaging survey. Based on their I magnitudes and the nominal age and distance to the cluster, these objects should

ABSTRACT

Wehaveidenti edtwenty-sevencandidateverylowmassmembersofthe

relativelyyoungAlphaPerseiopenclusterfromasixsquaredegreeCCDimaging

survey.BasedontheirImagnitudesandthenominalageanddistancetothe

cluster,theseobjectsshouldhavemasseslessthan0.1M⊙iftheyarecluster

members.Wehavesubsequentlyobtainedintermediateresolutionspectraof

seventeenoftheseobjectsusingtheKeckIItelescopeandLRISspectrograph.

Wehavealsoobtainednear-IRphotometryformanyofthestars.Ourprimary

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