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Titolo:
Infrared colors at the stellar/substellar boundary
Autore:
Leggett, SK; Allard, F; Hauschildt, PH;
Indirizzi:
Joint Astron Ctr, Hilo, HI 96720 USA Joint Astron Ctr Hilo HI USA 96720Joint Astron Ctr, Hilo, HI 96720 USA Ecole Normale Super, CRAL, F-69364 Lyon, France Ecole Normale Super LyonFrance F-69364 uper, CRAL, F-69364 Lyon, France Univ Georgia, Dept Phys & Astron, Athens, GA 30602 USA Univ Georgia Athens GA USA 30602 Dept Phys & Astron, Athens, GA 30602 USA Univ Georgia, Ctr Simulat Phys, Athens, GA 30602 USA Univ Georgia Athens GA USA 30602 , Ctr Simulat Phys, Athens, GA 30602 USA
Titolo Testata:
ASTROPHYSICAL JOURNAL
fascicolo: 2, volume: 509, anno: 1998,
parte:, 1
pagine: 836 - 847
SICI:
0004-637X(199812)509:2<836:ICATSB>2.0.ZU;2-9
Fonte:
ISI
Lingua:
ENG
Soggetto:
LOW-MASS STARS; PROPER-MOTION STARS; COOL BROWN DWARF; MODEL ATMOSPHERES; MAIN-SEQUENCE; LUMINOSITY; PARALLAXES; TEMPERATURE; METALLICITY; EVOLUTION;
Keywords:
infrared : stars; stars : atmospheres; stars : evolution; stars : fundamental parameters; stars : Population II;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
70
Recensione:
Indirizzi per estratti:
Indirizzo: Leggett, SK Joint Astron Ctr, Univ Pk, Hilo, HI 96720 USA Joint Astron CtrUniv Pk Hilo HI USA 96720 Hilo, HI 96720 USA
Citazione:
S.K. Leggett et al., "Infrared colors at the stellar/substellar boundary", ASTROPHYS J, 509(2), 1998, pp. 836-847

Abstract

We present new infrared JHK photometry for 61 halo and disk stars around the stellar/substellar boundary. We also present new L' photometry for 21 ofthese stars and for 40 low-mass stars taken from the Leggett photometry compilation. These data are combined with available optical photometry and astrometric data to produce color-color and absolute magnitude-color diagrams; the current sample extends the similar work presented in the 1992 paper into more metal-poor and lower mass regimes. The disk and halo sequences arecompared to the predictions of the latest model atmospheres and structuralmodels. We find good agreement between observation and theory except for known problems in the V and H passbands, probably due to incomplete molecular data for TiO, metal hydrides, and H2O. The metal-poor M subdwarfs are well matched by the models since oxide opacity sources are less important in this case. The known extreme M subdwarfs have metallicities about one-hundredth solar, and the coolest subdwarfs have T-eff similar to 3000 K with masses similar to 00.09 M/M.. The grainless models are not able to reproduce the flux distributions of disk objects with T-eff < 2500 K; however, a preliminary version of the NextGen-Dusty models that includes homogeneous formation and extinction by dust grains is able to match the colors of these very cool objects. The least luminous objects in this sample are GD 165B, three DENIS objects-DBD 0205, DBD 1058, and DBD 1228-and Kelu-1. These have T-effsimilar to 2000 K and are at or below the stellar limit with masses less than or equal to 0.075 M/M.. Photometry alone cannot constrain these parameters further since the age is unknown, but published lithium detections for two of these objects (Kelu-1 and DBD 1228) imply that they are young (aged about 1 Gyr) and substellar (mass less than or equal to 10.06 M/M.).

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Documento generato il 18/08/18 alle ore 08:31:59