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Titolo: Convection in the atmospheres and envelopes of turnoff and giant branch stars of globular clusters
Autore: Montalban, J; Kupka, F; DAntona, F; Schmidt, W;
 Indirizzi:
 Osservatorio Astron Roma, I00040 Monteporzio, Italy Osservatorio Astron Roma Monteporzio Italy I00040 40 Monteporzio, Italy Inst Astrofis Canarias, Tenerife 38200, Spain Inst Astrofis Canarias Tenerife Spain 38200 arias, Tenerife 38200, Spain Univ Vienna, Inst Astron, A1180 Vienna, Austria Univ Vienna Vienna Austria A1180 a, Inst Astron, A1180 Vienna, Austria Univ Wales, Dept Phys & Astron, Cardiff CF2 3YB, S Glam, Wales Univ WalesCardiff S Glam Wales CF2 3YB n, Cardiff CF2 3YB, S Glam, Wales
 Titolo Testata:
 ASTRONOMY & ASTROPHYSICS
fascicolo: 3,
volume: 370,
anno: 2001,
pagine: 982  990
 SICI:
 14320746(200105)370:3<982:CITAAE>2.0.ZU;2E
 Fonte:
 ISI
 Lingua:
 ENG
 Soggetto:
 STELLAR TURBULENT CONVECTION; BALMERLINEPROFILES; LOWMASS STARS; MODEL ATMOSPHERES; LOCAL SUBDWARFS; ASTAR; FSTAR; AGES; TEMPERATURE; EVOLUTION;
 Keywords:
 stars : evolution; stars : atmospheres; convection; Galaxy : globular clusters : individual : M 92;
 Tipo documento:
 Article
 Natura:
 Periodico
 Settore Disciplinare:
 Physical, Chemical & Earth Sciences
 Citazioni:
 46
 Recensione:
 Indirizzi per estratti:
 Indirizzo: Montalban, J Osservatorio Astron Roma, I00040 Monteporzio, Italy Osservatorio Astron Roma Monteporzio Italy I00040 o, Italy



 Citazione:
 J. Montalban et al., "Convection in the atmospheres and envelopes of turnoff and giant branch stars of globular clusters", ASTRON ASTR, 370(3), 2001, pp. 982990
Abstract
We explore the dependence of Teff's and colors of stellar models on the treatment of overadiabatic convection, both in the atmosphere and in the interior. We compute main sequence, turnoff, and subgiant models for low metallicity stars (Z = 2 10(4)) using as boundary conditions two new sets of model atmospheres by the Wien group (Kupka 1996; Smalley & Kupka 1997; Heiter et al. 2001). In these models convection is treated either in the Mixing Length Theory (MLT) or in the Full Spectrum of Turbulence (FST) formulation. We check the dependence of the Teff location of the HR diagram both on the optical depth tau at which the atmospheric boundary conditions are fixed, and on the convective model adopted in the atmosphere and interior. Obviously, full selfconsistency of the result is obtained only if the treatment of convection is the same in the outer layers and in the interior. We show that it is not appropriate to use MLT convection in the atmosphere and FST in the interior: if we wish to test the effect of changing the l/Hp in theMLT, the atmospheric integration must be limited to tau = 1. We construct isochrones for ages of 10 Gyr and greater, and transform the theoretical Teff and gravity values to the Johnson B and V magnitudes. The two sets of model atmospheres give small differences (up to similar to0.03 mag) for the BV color, a result of the different temperature stratification in the model atmosphere with FST convection treatment compared to that one based on MLT. The FST boundary conditions provide relative locations of turnoff and giant branch which differ from the MLT solutions, and are in better agreementwith the HR diagram morphology of the Globular Cluster M 92.
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Documento generato il 05/12/20 alle ore 08:08:41