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Titolo:
Keck spectra of brown dwarf candidates and a precise determination of the lithium depletion boundary in the alpha Persei open cluster

Autore:

Stauffer, JR; Navascues, DBY; Bouvier, J; Morrison, HL; Harding, P; Luhman, KL; Stanke, T; McCaughrean, M; Terndrup, DM; Allen, L; Assoaud, P;

Indirizzi:: Smithsonian Astrophys Observ, Cambridge, MA 02138 USA Smithsonian Astrophys Observ Cambridge MA USA 02138 mbridge, MA 02138 USA Max Planck Inst Astron, D-69117 Heidelberg, Germany Max Planck Inst Astron Heidelberg Germany D-69117 17 Heidelberg, Germany Univ Grenoble 1, Astrophys Lab, Observ Grenoble, F-38041 Grenoble, France Univ Grenoble 1 Grenoble France F-38041 enoble, F-38041 Grenoble, France Case Western Reserve Univ, Dept Astron, Cleveland, OH 44106 USA Case Western Reserve Univ Cleveland OH USA 44106 Cleveland, OH 44106 USA Univ Arizona, Steward Observ, Tucson, AZ 85726 USA Univ Arizona Tucson AZUSA 85726 na, Steward Observ, Tucson, AZ 85726 USA Inst Astrophys, D-14482 Potsdam, Germany Inst Astrophys Potsdam Germany D-14482 trophys, D-14482 Potsdam, Germany Ohio State Univ, Dept Astron, Columbus, OH 43210 USA Ohio State Univ Columbus OH USA 43210 Dept Astron, Columbus, OH 43210 USA Int Space Univ, F-67400 Illkirch, France Int Space Univ Illkirch France F-67400 ce Univ, F-67400 Illkirch, France
Titolo Testata:: ASTROPHYSICAL JOURNAL
fascicolo: 1, volume: 527, anno: 1999,
parte:, 1
pagine: 219 - 229
SICI:: 0004-637X(199912)527:1<219:KSOBDC>2.0.ZU;2-G
Fonte:: ISI
Lingua:: ENG
Soggetto:: LOW-MASS STARS; ROTATIONAL VELOCITIES; EVOLUTIONARY MODELS; FAINTEST PLEIADES; STANDARD STARS; MAIN-SEQUENCE; AGE; SPECTROSCOPY; MEMBERS; SYSTEM;
Keywords:: Hertzsprung-Russell diagram; open clusters and associations : individual (alpha Persei); stars : abundances; stars : low-mass, rown dwarfs;
Tipo documento:: Article
Natura:: Periodico
Settore Disciplinare:: Physical, Chemical & Earth Sciences
Citazioni:: 41
Recensione:
Indirizzi per estratti:: Indirizzo: Stauffer, JR Smithsonian Astrophys Observ, 60 Garden St, Cambridge, MA 02138 USA Smithsonian Astrophys Observ 60 Garden St Cambridge MA USA 02138



Citazione:: J.R. Stauffer et al., "Keck spectra of brown dwarf candidates and a precise determination of the lithium depletion boundary in the alpha Persei open cluster", ASTROPHYS J, 527(1), 1999, pp. 219-229

Abstract

We have identified 27 candidate very low mass members of the relatively young alpha Persei open cluster from a 6 deg(2) CCD imaging survey. Based on their I magnitudes and the nominal age and distance to the cluster, these objects should have masses less than 0.1 M. if they are cluster members. We subsequently obtained intermediate-resolution spectra of 17 of these objects using the Keck II telescope and Low-Resolution Imaging Spectrograph (LRIS). We also obtained near-IR photometry for many of the stars. Our primary goal was to determine the location of the "lithium depletion boundary" and, hence, to derive a precise age for the cluster. Most of our program objectshave radial velocities consistent with cluster membership, moderately strong Ha emission, and spectral types of M5.5 to M8, as expected from their (R-I)(C) colors. We detected lithium with equivalent widths greater than or equal to 0.4 Angstrom in five of the program objects. We have constructed a color-magnitude diagram for the faint end of the alpha Persei main sequence, including stars for which high signal-to-noise spectra in the region of the lithium lambda 6708 absorption line have been obtained. These data allowus to accurately determine the alpha Persei single-star lithium depletion boundary at M(I-C) = 11.47, M-bol = 11.42, (R-I)(C0) = 2.12, spectral type M6.0. By reference to theoretical evolutionary models, this converts fairlydirectly into an age for the alpha Persei cluster of 90 +/- 10 Myr. That age is considerably older than most previously quoted ages for the cluster but consistent with ages estimated from the upper main-sequence turnoff using recent models that include a moderate amount of convective core overshoot. At this age, the two faintest of our spectroscopically confirmed members should be substellar (i.e., brown dwarfs) according to theoretical models.

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Documento generato il 20/06/13 alle ore 11:22:48