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Stellar models

The current compilation includes all grids of Geneva stellar evolution models published between 1992 and march 1999 in papers I-VIII (see footnote of Table [*] for complete references) and a new grid of stellar models for very low metallicity (Z=1/50 Z_ Z$_{\odot}$, see Appendix). Pre-main sequence models are not included (but cf. Bernasconi 1996 and paper VIII). The complete set including the references, a grid number used subsequently throughout the paper, and other main characteristics are listed in Table [*] (see the original papers for a full description).


Table: Summary of stellar grids included in the database. The grid number used throughout the paper (col. 1), database ID (2), initial chemical composition (3-5), indications on the mass loss prescription (6), the covered mass range (7), the reference for the tracks (8), and a brief description of the main characteristics (9) are given.

Grid
database $Z$ $X$ $Y$ $\dot{M}$ mass range paper$^{(*)}$ description
# ID              
(1) (2) (3) (4) (5) (6) (7) (8) (9)

Basic grids:
         
1 e 0.0004 0.7584 0.2412 2$\times$std 0.8 - 150 M_ M$_{\odot}$ this paper basic grid
2 c 0.001 0.756 0.243 standard 0.8 - 120 M_ M$_{\odot}$ I basic grid
3 c 0.004 0.744 0.252 standard 0.8 - 120 M_ M$_{\odot}$ III basic grid
4 c 0.008 0.728 0.264 standard 0.8 - 120 M_ M$_{\odot}$ II basic grid
5 c 0.020 0.680 0.300 standard 0.8 - 120 M_ M$_{\odot}$ I basic grid
6 c 0.040 0.620 0.340 standard 0.8 - 120 M_ M$_{\odot}$ IV basic grid
7 c 0.100 0.420 0.480 standard 0.8 - 60 M_ M$_{\odot}$ VII basic grid
                 
Extended grids:          
8 e 0.001 0.756 0.243 2$\times$std: $M \ge 25 \ifmmode M_{\odot} \else M$_ 0.8 - 120 M_ M$_{\odot}$ V, I high mass loss for massive stars
9 e 0.004 0.744 0.252 2$\times$std: _ 0.8 - 120 M_ M$_{\odot}$ V, III high mass loss for massive stars
10 e 0.008 0.728 0.264 2$\times$std: _ 0.8 - 120 M_ M$_{\odot}$ V, II high mass loss for massive stars
11 e 0.020 0.680 0.300 2$\times$std: _ 0.8 - 120 M_ M$_{\odot}$ V, I high mass loss for massive stars
12 e 0.040 0.620 0.340 2$\times$std: _ 0.8 - 120 M_ M$_{\odot}$ V, IV high mass loss for massive stars
13 p 0.001 0.756 0.243 standard 0.8 - 1.7 M_ M$_{\odot}$ VI including HB and EAGB
14 p 0.020 0.680 0.300 standard 0.8 - 1.7 M_ M$_{\odot}$ VI including HB and EAGB
15 m 0.001 0.756 0.243 standard 0.4 - 1.0 M_ M$_{\odot}$ VIII MHD equation of state
16 m 0.020 0.700 0.280 standard 0.4 - 1.0 M_ M$_{\odot}$ VIII MHD equation of state
17   0.020 0.680 0.300 standard 0.4 - 1.0 M_ M$_{\odot}$ VIII MHD equation of state
                 
Alternate and combined model sets:          
  o 0.0004 0.7584 0.2412 2$\times$std 0.8 - 2.5 M_ M$_{\odot}$ this paper no overshooting: 1.25 M_ M$_{\odot}$
  o 0.001 0.756 0.243 standard 0.8 - 2.5 M_ M$_{\odot}$ I no overshooting: 1.25 M_ M$_{\odot}$
  o 0.004 0.744 0.252 standard 0.8 - 2.5 M_ M$_{\odot}$ III no overshooting: 1.25 M_ M$_{\odot}$
  o 0.008 0.728 0.264 standard 0.8 - 2.5 M_ M$_{\odot}$ II no overshooting: 1.25 M_ M$_{\odot}$
  o 0.020 0.680 0.300 standard 0.8 - 2.5 M_ M$_{\odot}$ I no overshooting: 1.25 M_ M$_{\odot}$
  o 0.040 0.620 0.340 standard 0.8 - 2.5 M_ M$_{\odot}$ IV no overshooting: 1.25 M_ M$_{\odot}$
  l 0.001 0.756 0.243 standard 0.4 - 2.5 M_ M$_{\odot}$   combination: grids 15, 13, 2
  l 0.020 0.680 0.300 standard 0.4 - 2.5 M_ M$_{\odot}$   combination: grids 17, 14, 5

               

 $^{(*)}$ I 		 : Schaller et al. (1992) 		 V 		 : Meynet et al. (1994)   

II : Schaerer et al. (1993) VI : Charbonnel et al. (1996)
III : Charbonnel et al. (1993) VII : Mowlavi et al. (1998a)
IV : Schaerer et al. (1993) VIII : Charbonnel et al. (1999)


Table: Summary of isochrone sets included in the database. The database ID (col. 1), metallicity (2), and a brief description of the main characteristics (5) are indicated. The logarithmic age range (in years) covered by the isochrones is given in columns 3 and 4. Isochrones are provided for time steps of for ages above 1 Myr (). For younger ages isochrones are for 3.0, 5.0, 5.3, 5.6, 5.8, and 5.9 yr.

Database
$Z$ age range () description    
ID   from to      
(1) (2) (3) (4) (5)    

Basic grids:
     
e 0.0004 3.00 10.20 basic grid    
c 0.001 3.00 10.20 basic grid    
c 0.004 3.00 10.20 basic grid    
c 0.008 3.00 10.20 basic grid    
c 0.020 3.00 10.20 basic grid    
c 0.040 3.00 10.20 basic grid    
c 0.100 3.00 10.20 basic grid    
             
Extended grids:      
e 0.001 3.00 7.50 high mass loss for massive stars    
e 0.004 3.00 7.50 high mass loss for massive stars    
e 0.008 3.00 7.50 high mass loss for massive stars    
e 0.020 3.00 7.50 high mass loss for massive stars    
e 0.040 3.00 7.50 high mass loss for massive stars    
p 0.001 9.00 10.20 including HB and EAGB phases for low mass stars    
p 0.020 9.00 10.20 including HB and EAGB phases for low mass stars    
m 0.001 9.00 10.30 MHD equation of state for low mass stars    
m 0.020 9.00 10.30 MHD equation of state for low mass stars    
             
Alternate and combined model sets:      
o 0.0004 9.00 10.20 no overshooting: 1.25 M_ M$_{\odot}$    
o 0.001 9.00 10.20 no overshooting: 1.25 M_ M$_{\odot}$    
o 0.004 9.00 10.20 no overshooting: 1.25 M_ M$_{\odot}$    
o 0.008 9.00 10.20 no overshooting: 1.25 M_ M$_{\odot}$    
o 0.020 9.00 10.20 no overshooting: 1.25 M_ M$_{\odot}$    
o 0.040 9.00 10.20 no overshooting: 1.25 M_ M$_{\odot}$    
l 0.001 9.00 10.30 combination ``best'' low mass star models    
l 0.020 9.00 10.30 combination ``best'' low mass star models    

           


Table: Description of file extensions ext used for the stellar tracks ( mod*.ext) and isochrones ( iso*.ext).

File extension
description  

dat
Complete set of predicted surface stellar properties  
UBVRIJHKLM Main stellar properties and photometric data for (UBV)$_J$(RI)$_C$ JHKLL$^\prime$M system  
WFPC2 Main stellar properties and photometric data for WFPC2 system  
geneva Main stellar properties and photometric data for Geneva system  

   

The physical ingredients have been discussed in papers I-VIII. For completeness sake a brief summary of the basic assumptions common to most model sets is presented here. Variations are discussed below. 1) OPAL and low temperature opacities of Kurucz (1991) or Alexander & Ferguson (1994) are used. 2) The initial composition is derived from a linear chemical enrichment law with , and 3. for 0.02 and 2.5 for respectively. 3) Mass loss rates are taken from de Jager et al. (1998) throughout the HR-diagram except on the red giant branch (RGB) and early asymptotic giant branch (EAGB) for initial masses _, where the following expression is used (cf. Reimers 1975): in units of M_ M$_{\odot}$ yr, with at solar metallicity (see Maeder & Meynet 1989). Mass loss is scaled with metallicity by _, except for Wolf-Rayet (WR) stars. In the WR phases the relation of Langer (1989) for WNE and WC stars, and M_ M$_{\odot}$ yr for WNL stars is used. 4) Moderate core overshooting of is included for stars _. For stars at _ with a small or absent convective core tracks with and without overshooting are provided. 5) In addition to the effects treated by Maeder & Meynet (1989), partial ionisation of heavy elements is included in the equation of state. 6) Optically thick envelopes of WR stars are treated in the framework of the modified Castor, Abbott & Klein (CAK, 1975) theory.

The above ingredients are used in grids 2-7 which cover the metallicity range from to 0.100 (1/20 - 5 Z_ Z$_{\odot}$). Grids 1 and 8-12 were calculated with mass loss rates enhanced by a factor of 2 during the MS, the pre-WR, and WNL phases for massive stars (range indicated in col. 6); for lower masses the models are complemented with the tracks from grids 2-6 or represent new calculations (grid 1; see Appendix). In grids 1-12, depending on the stellar mass range, the evolution is in general followed up to the following phases: to the end of C-burning for massive stars ( _), to the end of the early asymptotic giant branch (EAGB) for intermediate mass stars ( _), and up to before the helium flash for low mass stars ( _). Grids 13 and 14 (paper VI) present new calculations for the latter mass range at metallicities and 0.001 including post-helium flash models, i.e. covering the horizontal branch (HB) and EAGB phases. The post-helium flash tracks do not include overshooting and semi-convection. The MHD (Mihalas, Hummer & Däppen, 1988) equation of state was used for the low mass models of paper VIII (grids 15, 16, 17). The calculations in grids 15-17 are followed up to before the helium flash or ages larger than the Hubble time ( 20 Gyr). Note that the solar metallicity grid 16 uses a different composition than the remaining grids.

The present compilation includes stellar models covering a very large parameter space in terms of mass, metallicity, and evolutionary phases. However, we wish to stress again that e.g. the following evolutionary phases are not covered: 1) pre-main sequence tracks (for Geneva models see Bernasconi 1996 and paper VIII), 2) thermally pulsing AGB stars, and 3) post-AGB stars and white dwarfs. Other phases (e.g. horizontal branch) are given only for a subset of metallicities. These limitations should be recognized by the user of the database. Calculations from other groups partly including such phases are mentioned in Section 4.


next up previous
Next: Atmosphere models Up: Input Previous: Input
Thibault Lejeune
2000-11-23