J/A+A/328/349 Role of Convection in A, F, and G stars (Smalley+ 1997)
The role of convection on the uvby colours of A, F, and G stars
Smalley B., Kupka F.
<Astron. Astrophys. 328, 349 (1997)>
=1997A&A...328..349S 1997A&A...328..349S (SIMBAD/NED BibCode)
ADC_Keywords: Models, atmosphere ; Abundances ; Photometry, uvby
Keywords: convection - stars: atmospheres - stars: general -
stars: fundamental parameters - stars: late-type
Description:
We discuss the effects of convection on the theoretical uvby colours
of A, F, and G stars. The standard mixing-length theory atlas9 models
of Kurucz (1993, ATLAS9, SAO, Cambridge, USA), with and without
approximate overshooting, are compared to models using the turbulent
convection theory proposed by Canuto & Mazzitelli
(1991ApJ...370..295C 1991ApJ...370..295C, 1992ApJ...389..724C 1992ApJ...389..724C) and implemented by Kupka
(1996, ASPConf. Proc. 108, 73).
Comparison with fundamental Teff and log g stars reveals that the
Canuto & Mazzitelli models give results that are generally superior to
standard mixing-length theory (MLT) without convective overshooting.
MLT models with overshooting are found to be clearly discrepant. This
is supported by comparisons of non-fundamental stars, with Teff
obtained from the Infrared Flux Method and log g from stellar
evolutionary models for open cluster stars. The Canuto & Mazzitelli
theory gives values of (b-y)0 and c0 that are in best overall
agreement with observations.
Investigations of the m0 index reveal that all of the treatments of
convection presented here give values that are significantly
discrepant for models with Teff<6000K. It is unclear as to whether
this is due to problems with the treatment of convection, missing
opacity, or some other reason. None of the models give totally
satisfactory m0 indices for hotter stars, but the Canuto & Mazzitelli
models are in closest overall agreement above 7000K.
Grids of uvby colours, based on the CM treatment of convection, are
presented. These grids represent an improvement over the colours
obtained from models using the mixing-length theory. The agreement
with fundamental stars enables the colours to be used directly without
the need for semi-empirical adjustments that were necessary with the
earlier colour grids.
For a description of the uvby photometric system, see e.g. GCPD/04
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
cm_p10.dat 57 169 *Canuto & Mazzitelli (CM) grid for [M/H] = +1.0
cm_p05.dat 57 169 CM grid for [M/H] = +0.5
cm_p00.dat 57 169 CM grid for [M/H] = +0.0
cm_m05.dat 57 169 CM grid for [M/H] = -0.5
cm_m10.dat 57 169 CM grid for [M/H] = -1.0
table5 79 86 Comparison between evolutionary and grid log g
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Note to cm_p10.dat: Canuto & Mazzitelli models, 1991ApJ...370..295C 1991ApJ...370..295C and
1992ApJ...389..724C 1992ApJ...389..724C.
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Byte-by-byte Description of file: cm*.dat
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Bytes Format Units Label Explanations
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1- 5 I5 K Teff Teff
8- 11 F4.2 [cm/s2] log(g) log g
13- 17 F5.2 [Sun] [M/H] Metallicity [M/H]
20- 23 F4.2 km/s Vturb microturbulence
29- 33 F5.3 mag u-b u-b colour index
37- 41 F5.3 mag b-y b-y colour index
45- 49 F5.3 mag m1 m1 colour index
53- 57 F5.3 mag c1 c1 colour index
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Byte-by-byte Description of file: table5
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Bytes Format Units Label Explanations
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1- 5 I5 --- HD HD (Cat. III/135) number
7- 10 I4 K Teff Teff from Kunzli et al.
(1997, Cat. J/A+AS/122/51)
12- 15 F4.2 [cm/s2] logg logg from evolutionary models
(Kunzli et al., 1997, Cat. J/A+AS/122/51)
18- 22 F5.3 mag b-y b-y colour index
24- 28 F5.3 mag c0 c0 colour index
31- 34 I4 K Teff(CM) Teff from CM (Canuto & Mazzitelli) grid (1)
36- 39 F4.2 [cm/s2] logg(CM) logg from CM grid
41- 45 F5.2 [cm/s2] Dlogg(CM) Delta logg for CM grid
48- 51 I4 K Teff(noOV) Teff from MLT (mixing-length theory) noOV grid
53- 56 F4.2 [cm/s2] logg(noOV) logg from MLT noOV grid
58- 62 F5.2 [cm/s2] Dlogg(noOV) Delta logg for MLTnoOV grid
65- 68 I4 K Teff(OV) Teff from MLT OV grid
70- 73 F4.2 [cm/s2] logg(OV) logg from MLT OV grid
75- 79 F5.2 [cm/s2] Dlogg(OV) Delta logg for MLT OV grid
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Note (1): Canuto & Mazzitelli models, 1991ApJ...370..295C 1991ApJ...370..295C and
1992ApJ...389..724C 1992ApJ...389..724C.
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Acknowledgements: Barry Smalley
(End) Patricia Bauer [CDS] 30-Jul-1997