File types

The ASCII data files are individually gzipped and the file types are identified by their file name extensions:

".mod" contain the most detailed lists of the model structure, thermodynamical quantities, and many partial gas pressures. Their sizes gzipped/unzipped are typically 10/25 kB. Here is a FORTRAN program to read these models.
".opa" contain the basic model structures and continuous opacities as a function of wavelength and optical depth useful for synthetic spectrum calculations. Their sizes gzipped/unzipped are typically 0.4/1.4 MB. Here is a FORTRAN program to read the opacity data files.
".krz" contain model files in a format explained below. Their sizes gzipped/unzipped are typically 2/6 kB.
".flx" contain statistical samples of the model surface fluxes derived in the model calculations. They give rough estimates of the surface fluxes and are NOT synthetic spectra why they should not be used for synthetic photometry. See below and Plez (2008) for a discussion of the effects on the model fluxes of the opacity sampling frequency. The flux units are erg/cm²/s/Å. The wavelengths range from 1300 to 200,000 Å in vacuum and come in a separate file "flx_wavelengths.vac.gz". The wavelength step is NOT equidistant but has rather a constant resolving power R=λ/Δλ=20,000. The file sizes are typically 0.4/1.4 MB.

Model parameters

The stellar atmospheric model parameters range in effective temperature from 2500 to 8000 K in steps of 100 K from 2500 to 4000 K and 250 K between 4000 and 8000 K. The logarithmic surface gravities (cgs units) between −1.0 and 5.5 in steps of 0.5. Overall logarithmic metallicities relative to the Sun are between −5.0 and +1.0 in variable steps. The reference solar abundance mixture is that of Grevesse, Asplund & Sauval (2007). The atmospheres of more luminous stars with low surface gravities (−1.0 to +3.5) are calculated in spherical geometry and with different stellar masses: the standard mass is 1.0 solar mass with sparse grids at 0.5, 2.0, and 5.0 Msun. The spectral differences of using spherical rather than plane-parallell models and/or radiative transfer for luminous stars were explored by Heiter & Eriksson (2006). Plane parallel models are computed for gravities between 3.0 and 5.0 or 5.5 for the cooler models. Models with different choices of "microturbulence parameters" are also available.

Since the mixture of metals vary among stars there are presently seven different "metallicity classes": "standard", "alpha poor", "alpha enhanced", "alpha negative", "mildly CN cycled", "heavily CN cycled", and for solar [Fe/H] there is also a subgrid with abundances according to "Grevesse & Sauval (1998)". The "standard" mixture reflects the typical elemental abundance ratios in stars as a function of metallicity [Fe/H] in the solar neighbourhood. The model grids lack many models due to convergence problems, particularly for low-gravity models, and specifically the warm low-gravity corners of the sperical-geometry subgrids are all empty.

The tables below display the abundance mixtures for the different metallicity classes. The "pp" and "sph" columns display the available microturbulence parameter values (km/s) for plane parallell and spherical model geometries, respectively. The complete elemental composition of a model is given in the ".mod" files and in a different format in the ".krz" files.

Standard, 30% of all models

[Fe/H]	[α/Fe]	[O/Fe]			sph
+1.00	0.00	0.00	1	2		2	5
+0.75	0.00	0.00	1	2		2	5
+0.50	0.00	0.00	1	2		2	5
+0.25	0.00	0.00	1	2		2	5
0.00	0.00	0.00	1	2	1	2	5
−0.25	+0.10	+0.10	1	2		2	5
−0.50	+0.20	+0.20	1	2		2	5
−0.75	+0.30	+0.30	1	2		2	5
−1.00	+0.40	+0.40	1	2		2	5
−1.50	+0.40	+0.40	1	2		2	5
−2.00	+0.40	+0.40	1	2		2	5
−2.50	+0.40	+0.40	1	2		2	5
−3.00	+0.40	+0.40	1	2		2	5
−4.00	+0.40	+0.40	1	2		2	5
−5.00	+0.40	+0.40	1	2		2	5

Alpha enhanced, 15% of all models

[Fe/H]	[α/Fe]	[O/Fe]			sph
+1.00	+0.40	+0.40	1	2	2	5
+0.75	+0.40	+0.40	1	2	2	5
+0.50	+0.40	+0.40	1	2	2	5
+0.25	+0.40	+0.40	1	2	2	5
0.00	+0.40	+0.40	1	2	2	5
−0.25	+0.40	+0.40	1	2	2	5
−0.50	+0.40	+0.40	1	2	2	5
−0.75	+0.40	+0.40	1	2	2	5

Alpha poor, 14% of all models

[Fe/H]			sph
−0.25	1	2	2	5
−0.50	1	2	2	5
−0.75	1	2	2	5
−1.00	1	2	2	5
−1.50	1	2	2	5
−2.00	1	2	2	5
−2.50	1	2	2	5

Alpha negative, 23% of all models

[Fe/H]	[α/Fe]	[O/Fe]			sph
+1.00	−0.40	−0.40	1	2	2	5
+0.75	−0.40	−0.40	1	2	2	5
+0.50	−0.40	−0.40	1	2	2	5
+0.25	−0.40	−0.40	1	2	2	5
0.00	−0.40	−0.40	1	2	2	5
-0.25	−0.40	−0.40	1	2	2	5
-0.50	−0.40	−0.40	1	2	2	5
-0.75	−0.40	−0.40	1	2	2	5
-1.00	−0.40	−0.40	1	2	2	5
-1.50	−0.40	−0.40	1	2	2	5
-2.00	−0.40	−0.40	1	2	2	5

Mildly CN cycled, ¹²C/¹³C=20, 8% of all models

[Fe/H]	[α/Fe]	[C/Fe]	[N/Fe]	[O/Fe]	sph
+0.25	0.00	−0.13	+0.31	0.00	2	5
0.00	0.00	−0.13	+0.31	0.00	2	5
−0.50	+0.20	−0.13	+0.31	+0.20	2	5
−1.00	+0.40	−0.13	+0.31	+0.40	2	5
−1.50	+0.40	−0.13	+0.31	+0.40	2	5
−2.00	+0.40	−0.13	+0.31	+0.40	2	5

Heavily CN cycled, ¹²C/¹³C=4, 8% of all models

[Fe/H]	[α/Fe]	[C/Fe]	[N/Fe]	[O/Fe]	sph
+0.25	0.00	−0.38	+0.53	0.00	2	5
0.00	0.00	−0.38	+0.53	0.00	2	5
−0.50	+0.20	−0.38	+0.53	+0.20	2	5
−1.00	+0.40	−0.38	+0.53	+0.40	2	5
−1.50	+0.40	−0.38	+0.53	+0.40	2	5
−2.00	+0.40	−0.38	+0.53	+0.40	2	5

Grevesse & Sauval (1998), 2% of all models

[Fe/H]	[α/Fe]	[C/Fe]	[N/Fe]	[O/Fe]	pp			sph
+0.05	+0.11	+0.08	+0.09	+0.12	0	1	2	2	5

The MARCS model flux files

The flux data files are not proper spectra, merely one-dimensional files of sampled photospheric surface fluxes (in ergs/cm²/s/Å) from 1300 Å to 20 μm sampled with a constant λ/Δλ = 20,000. This means that spectral lines are not resolved and that much information is missing. The convolution of a flux file will not help and still gives seriously erroneous line strengths. The average flux in a limited wavelength region may also give a poor representation of the integrated flux in that region.

The wavelength scale of the flux sample data is in vacuum, and the wavelengths (about 100,000 points) are supplied in a separate one-dimensional file, which is the same one for all models.

Auxiliary Data

1. Astrophysical gf values for 2224 metal lines

In Gustafsson et al. (2008) almost all metal line opacity data used in the construction of the MARCS model atmospheres was obtained from VALD 1 (Piskunov et al. 1995) and VALD 2 (Stempels et al. 2001). For for 948 atomic lines in VALD 1, and 1276 lines of the 10 most important revised species (Si I, Ca I, Ca II, Ti II, Cr I, Cr II, Mn II, Fe I, Fe II, and Ni II) in VALD 2, however, we obtained and used astrophysical gf values to improve the detailed line spectrum fit to the solar spectrum.

The modified lines fall in the wavelength range 3783 to 8968 Å, and are based on ocular inspection of fits of synthetic solar intensity spectra calculated with the Holweger & Müller (1974) model to the observed solar disk-center FTS spectrum of Brault & Neckel (1987). About 40% of the modified lines are Fe I lines. The most common modifications to the log gf values are negative, since a too strong synthetic line is probably wrong, while a too weak line may be correct and explained by unidentified line blends. A log gf value was only increased when some alternative line identification supported that of the wavelength coincidence. A log gf value of -9.99 signals that the line was not found in the solar spectrum.

This Readme text can be downloaded as astroph_gfVALD.txt.

The plain text data tables astroph_gfVALD1.dat and astroph_gfVALD2.dat give for each line :

Element number in the periodic table
Ion (1 for neutral, 2 for singly ionized)
VALD air wavelength (A) (VALD 1 or VALD 2, respectively)
Lower level excitation energy (eV) (VALD 1 or VALD 2, respectively)
Lower level j quantum number (VALD 1 or VALD 2, respectively)
Astrophysical value of log gf (elaborated to within 0.1 dex)
Species label
Lower level designation (VALD 1 or VALD 2, respectively)
Upper level designation (VALD 1 or VALD 2, respectively)
Original VALD log gf (VALD 1 or VALD 2, respectively)

Example: The beginning of file astroph_gfVALD1.dat :

28 1 3783.5240  0.4230  2.0  -1.70 'Ni I ' 'a 1D       ' 'z 5F*      ' -1.310
60 2 3784.2450  0.3800  5.5  -0.05 'Nd II' '6s  4I     ' '6p *       '  0.098
22 1 3789.2940  1.4600  4.0  -0.75 'Ti I ' '(4F)4s b3F ' '(3P)sp u3D ' -0.451
12 1 3789.5690  4.3460  1.0  -9.99 'Mg I ' 's3p  1P    ' '22d  1D    ' -2.000
12 1 3793.1630  4.3460  1.0  -9.99 'Mg I ' 's3p  1P    ' '21d  1D    ' -2.000
22 1 3795.8940  1.4430  3.0  -0.15 'Ti I ' '(4F)4s b3F ' '(3P)sp u3D ' -0.295
40 2 3796.4930  1.0110  4.5  -0.90 'Zr II' '4d3 a2G    ' 'd25p z2G   ' -0.830
12 1 3797.1690  4.3460  1.0  -9.99 'Mg I ' 's3p  1P    ' '20d  1D    ' -2.000
40 2 3800.7430  0.5270  1.5  -2.05 'Zr II' 'd25s a2D   ' 'd25p z4F   ' -1.300
58 2 3801.5260  0.8970  5.5  -0.05 'Ce II' 'fd6s *4G   ' 'fd6p  4H   '  0.870

The reference for the astrophysical gf values is Gustafsson et al. (2008).

The VALD line data base may be found e.g. at https://vald.astro.uu.se/

2. Scaled FeH line data

The FeH line list (here generated 15-Jun-2015) was originally calculated by B. Plez for the work on M dwarf stars by Önehag et al. (2012).

F4Δ - X4Δ transitions
v'=0,1,2 v"=0,1,2
Jmax=40.5

where ' and " designate the upper and lower level, respectively. Energy levels were computed from identified levels in Phillips et al. (1987) in the following way: For each vibrational level, and each of the 8 lambda-doubled substates, a fit of energy as a function of rotational quantum numbers (J) was made through the measured rotational levels. In most cases this fit is of order 3, but for a few levels a better quadratic fit was adopted. The calculated levels were only used when no observation was available. Line intensities were computed from Hönl-London and Franck-Condon factors (see Plez (1998) for additional details), and then scaled to agree with the Av'v" of Langhoff & Bauschlicher (1990). The line list is given in the Turbospectrum format. (Turbospectrum can be found at http://ascl.net/1205.004):

lambda      E"   log(gf)      2*J'+1                            v' v" branch J" species band
  (A)      (eV)
7626.509  0.086 -4.789  0.00   20.0 0.00E+00 'X' 'X'  0.0  1.0 ' 2  0 SR32  8.5 FeH     FX'

Branch designation has its usual meaning, the first and second letter denoting respectively DeltaN and DeltaJ, with Delta=-2,-1,0,1,2 denoted by O,P,Q,R,S. The two numbers are for the four substates. The non-designated columns contain specific but unknown parameters that may be used in Turbospectrum.

The plain text FeH Readme file is FeH_Readme.txt

The plain text data table containing 19830 FeH lines is FeH_Plez_Langhoff-Bauschlicher_strength.dat

References:

Brault & Neckel 1987, unpublished
Gustafsson B., Edvardsson B., Eriksson K., Jørgensen U.G., Nordlund Å., Plez B. 2008, A&A 486, 951
Holweger H., Müller E.A., 1974, Solar Physics 39, 19
Langhoff S.R., & Bauschlicher C.W. 1990, J. Mol. Spectrosc. 141, 243
Önehag A., Heiter U., Gustafsson B., Piskunov N., Plez B., Reiners A. 2012, A&A 542, 330
Phillips J.G., Davis S.P., Lindgren B., & Balfour W.J. 1987, ApJS 65, 721
Piskunov et al. 1995, A&AS 112, 525 (VALD 1)
Plez B. 1998, A&A 337, 495
Stempels et al. 2001, ASP Conf. Ser. 223, 878, eds. R.J. Garcia Lopez, R. Rebolo, M.R. Zapaterio Osorio (VALD 2)

The ".opa" files with continuous opacities

The "opa" format files are model files constructed for the calculation of synthetic spectra from MARCS models with line-data files compiled by the user. Here is a FORTRAN subroutine to read a continuous-opacity file and store it into arrays.

The format of the files is as follows, explanations in italics:

MRXF   56   5000.00
1) label. 2) no of depth points in the model. 3) wavelength (Å) for the standard opacity

  1071
the number of wavelengths for which continuous scattering and absorption is given 

      912.82     924.44     943.69     967.98     994.02    1018.31    1037.56    1049.18    1055.17    1063.83
listing of these wavelengths (Å), these are selected to take care of opacity edges so that linear interpolation
should work fine.
(104 lines skipped)

  1604691.00 1623076.50 1650000.00 1676923.50 1695309.00 1704691.00 1723076.50 1750000.00 1776923.50 1795309.00
  1804691.00 1823076.50 1850000.00 1876923.50 1895309.00 1904713.50 1923187.25 1950240.00 1977292.75 1995766.50
  2000482.0
  1.0000E+00 7.6855E-04 2.7584E+03 2.5009E-06 2.6666E+02 1.5165E-09 2.0000E+00 4.4348E-04
the last line is the start of the listing of the first (outermost) depth point: 1) geometry factor, 1.0 for plane-parallel
models and ≤ 1.0 for spherical models. 2) optical depth at the standard wavelength (5000 Å). 3) temperature (K).
4) electron pressure (cgs). 5) gas pressure (cgs). 6) density (cgs). 7) microturbulence parameter (km/s).
8) total opacity (absorption+scattering at the standard wavelength 5000 Å)

  5.7495E+02 3.7985E+03 5.4600E+02 3.7985E+03 5.0825E+02 3.7985E+03
1071 pairs of numbers for the wavelengths listed at the top.
1) true absorption (at 912.82 Å) divided by the total opacity, col 8 in the line above.
2) scattering (at 912.82 Å) divided by the total opacity, col 8 in the line above.
3) true absorption (at 924.44 Å) divided by the total opacity, col 8 in the line above.
4) scattering (at 924.44 Å) divided by the total opacity, col 8 in the line above.
5) true absorption (at 943.69 Å) divided by the total opacity, col 8 in the line above.
6) scattering (at 943.69 Å) divided by the total opacity, col 8 in the line above.

  4.7818E+02 3.7985E+03 4.6610E+02 3.7985E+03 4.6835E+02 3.7985E+03
  4.7388E+02 3.5182E+03 4.7697E+02 3.2611E+03 4.7831E+02 3.1372E+03
  4.7975E+02 2.9680E+03 4.8022E+02 2.9010E+03 4.8038E+02 2.8798E+03
  4.8066E+02 2.8420E+03 4.8154E+02 2.7324E+03 3.8570E+02 2.5968E+03
(350 lines skipped)
then the end for depth point 1 and the beginning of number 2:

  9.6057E-01 6.4986E-06 9.6343E-01 6.4985E-06 9.7031E-01 6.4985E-06
  9.8016E-01 6.4985E-06 9.8847E-01 6.4985E-06 9.9079E-01 6.4985E-06
  9.9953E-01 1.1989E-03 2.7970E+03 3.5641E-06 3.6230E+02 2.0343E-09 2.0000E+00 4.4354E-04
  6.8965E+02 3.7922E+03 6.4985E+02 3.7922E+03 5.9623E+02 3.7922E+03
  5.4946E+02 3.7922E+03 5.2293E+02 3.7922E+03 5.1429E+02 3.7922E+03
  5.1252E+02 3.5124E+03 5.1166E+02 3.2557E+03 5.1108E+02 3.1321E+03
(19683 lines skipped)

  6.0292E+03 7.9467E-05 5.9957E+03 7.9467E-05 5.9868E+03 7.9467E-05
  5.9865E+03 7.9467E-05 5.9941E+03 7.9467E-05 6.0240E+03 7.9467E-05
  6.0746E+03 7.9467E-05 6.1202E+03 7.9467E-05 6.1331E+03 7.9467E-05
  12.000  10.930  -2.900  -2.600  -1.210   4.410   3.800   5.060   0.480   4.480
   2.330   3.980   2.470   3.950   1.450   3.730   1.280   2.800   1.120   2.760
  -0.830   1.420   0.000   1.670   1.390   3.500   0.920   2.250   0.210   0.600
  -1.120  -0.590  -1.630  -0.590  -1.370  -0.690  -1.400  -1.030  -1.760  -1.400
  -2.580  -2.080 -99.000  -2.160  -2.880  -2.310  -2.760  -2.230  -3.180  -2.000
  -3.000  -1.760  -2.490  -1.830  -2.870  -1.870  -2.830  -2.420  -3.290  -2.500
 -99.000  -2.990  -3.490  -2.880  -3.650  -2.860  -3.490  -3.070  -3.850  -2.920
  -3.940  -3.120  -4.130  -3.310  -3.720  -2.550  -2.650  -2.200  -3.150  -2.870
  -2.050  -3.290 -99.000 -99.000 -99.000 -99.000 -99.000 -99.000  -3.910
 -99.000  -4.500
the final 10 lines specify the chemical composition of the model, the total number abundances
of the 92 first elements in the periodic table on a logarithmic scale where hydrogen=12.0

The ".krz" format

The "krz" format was developed as part of a project aimed at self-consistent determinations of abundances in pulsating early-type stars (B to F). This project was carried out at the Institute for Astronomy in Vienna and more details can be found in http://ams.astro.univie.ac.at/ .
An explanation of the .krz format is given below.
Among other things the following issues have been addressed within this project:

Creation of a complete database of atomic line data (VALD, https://vald.astro.uu.se/ , Kupka et al.: 1999, A&AS 138, 119) used for opacity calculations and spectral synthesis;
Calculation of model atmospheres consistent with the derived abundances (Piskunov & Kupka: 2001, ApJ 547, 1040);
Fast and accurate spectral synthesis codes with and without the effects of magnetic fields like SME (Valenti & Piskunov: 1996, A&AS 118, 595) and SYNTHMAG (Piskunov: 1999, in Proc. of Solar polarization workshop, Bangalore, 1998, Nagendra & Stenflo (eds.), Kluwer Astrophysics and space science library, v. 243, p. 515);
Doppler Imaging of chemical composition and magnetic fields (Piskunov & Kochukhov: 2002, A&A 381, 736).

All of the above requires a subset of data from a model atmosphere in a compact format like the KRZ. Since several of the programmes mentioned above are actively used in stellar astrophysics we offer an option to retrieve the MARCS models also in the KRZ format.

When you download models with SPHERICAL geometry in the .krz format, then

the MODEL TYPE will be 3 ( for the plane-parallel models it is 0 (zero) )
in the listing of the model there will be a sixth column containing the the radial distance from a reference layer (in cm), counted positive outwards of this layer and negative inwards. This reference layer is where the Rosseland optical depth equals 1 in the model (log tau_Ross = 0.0). The stellar radius (at log tau_Ross = 0.0) is given in the corresponding ".mod" format file.

Explanation of the "krz" model format. By Nikolai Piskunov 2010-06-10

TITLE SDSC GRID [+0.0] VTURB 2.0 KM/S L/H 1.25 UNSCALED T EFF= 7500. GRAV= 4.5 MODEL TYPE= 0 WLSTD= 5000. 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 0 0 0 0 0 - OPACITY SWITCHES 0.911 0.089 -10.88 -10.89 -9.44 -3.48 -3.99 -3.11 -7.48 -3.95 -5.71 -4.46 -5.57 -4.49 -6.59 -4.83 -6.54 -5.48 -6.82 -5.68 -8.94 -7.05 -8.04 -6.37 -6.65 -4.37 -7.12 -5.79 -7.83 -7.44 -9.16 -8.63 -9.67 -8.69 -9.41 -8.81 -9.44 -9.14 -9.80 -9.54 -10.62 -10.12 -20.00 -10.20 -10.92 -10.35 -11.10 -10.18 -10.58 -10.04 -11.04 -9.80 -10.53 -9.81 -10.92 -9.91 -10.82 -10.49 -11.33 -10.54 -20.00 -11.04 -11.53 -10.92 -11.94 -10.94 -11.78 -11.11 -12.04 -10.96 -11.28 -11.16 -11.91 -10.93 -11.77 -10.59 -10.69 -10.24 -11.03 -10.95 -11.14 -10.19 -11.33 -20.00 -20.00 -20.00 -20.00 -20.00 -20.00 -11.92 -20.00 -12.51 -20.00 -20.00 -20.00 -20.00 -20.00 -20.00 -20.00 72 1.494770850E-04, 4892.5, 7.94600E+09, 6.99057E+12, 1.50828E-11, 1.983653960E-04, 4912.0, 9.81300E+09, 9.24075E+12, 1.99378E-11, 2.605118600E-04, 4933.4, 1.21100E+10, 1.20835E+13, 2.60713E-11, 3.383485310E-04, 4954.9, 1.48600E+10, 1.56274E+13, 3.37177E-11, 4.346934090E-04, 4976.9, 1.81400E+10, 1.99941E+13, 4.31392E-11, 5.527391110E-04, 4998.8, 2.20200E+10, 2.53075E+13, 5.46034E-11, 6.962465410E-04, 5020.9, 2.65800E+10, 3.17412E+13, 6.84848E-11, 8.694794060E-04, 5043.1, 3.19500E+10, 3.94671E+13, 8.51541E-11, 1.077280610E-03, 5065.9, 3.82800E+10, 4.86771E+13, 1.05026E-10, 1.325020170E-03, 5089.5, 4.57400E+10, 5.95877E+13, 1.28566E-10, 1.618741570E-03, 5114.0, 5.45800E+10, 7.24517E+13, 1.56322E-10, 1.965294820E-03, 5139.7, 6.50600E+10, 8.75249E+13, 1.88844E-10, ... or

TITLE MARCS 35 model for MLT convection testing. Vturb 2.0 km/s T EFF= 6500. GRAV= 2.0 MODEL TYPE= 3 WLSTD= 5000 SPHERICAL, RADIUS= 1.155E+12 cm 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 0 0 0 0 0 - OPACITY SWITCHES 0.922 0.078 -10.88 -10.89 -9.44 -5.65 -6.26 -4.98 -7.48 -5.80 -7.87 -6.11 -7.67 -6.13 -6.59 -6.50 -6.54 -5.48 -8.96 -7.33 -10.87 -8.74 -10.04 -8.40 -8.65 -6.59 -9.12 -7.81 -7.83 -7.44 -9.16 -8.63 -9.67 -8.69 -9.41 -8.81 -9.44 -9.14 -9.80 -9.54 -10.62 -10.12 -20.00 -10.20 -10.92 -10.35 -11.10 -10.18 -10.58 -10.04 -11.04 -9.80 -10.53 -9.81 -10.92 -9.91 -10.82 -10.49 -11.33 -10.54 -20.00 -11.04 -11.53 -10.92 -11.94 -10.94 -11.78 -11.11 -12.04 -10.96 -11.28 -11.16 -11.91 -10.93 -11.77 -10.59 -10.69 -10.24 -11.03 -10.95 -11.14 -10.19 -11.33 -20.00 -20.00 -20.00 -20.00 -20.00 -20.00 -11.92 -20.00 -12.51 -20.00 -20.00 -20.00 -20.00 -20.00 -20.00 -20.00 56 4.754334316E-02, 4571.6, 1.64024E+09, 3.81952E+12, 7.94416E-12, 2.44799E+10, 6.466705352E-02, 4613.0, 2.50945E+09, 6.46942E+12, 1.34563E-11, 2.27099E+10, 8.941244334E-02, 4662.0, 3.81018E+09, 1.02419E+13, 2.13033E-11, 2.11329E+10, 1.236606389E-01, 4714.4, 5.68486E+09, 1.53860E+13, 3.20032E-11, 1.97191E+10, 1.695764661E-01, 4768.2, 8.31312E+09, 2.21840E+13, 4.61428E-11, 1.84345E+10, 2.299538255E-01, 4821.7, 1.19096E+10, 3.10038E+13, 6.44878E-11, 1.72482E+10, 3.084119260E-01, 4874.9, 1.67679E+10, 4.23195E+13, 8.80230E-11, 1.61355E+10, ...

1st line - header
2nd line
- T_eff (K)
- logg (cgs)
- model type: 0 - plane-parallel, depth scale - column mass in g/cm²
- model type: 1 - plane-parallel, depth scale - tau at std wavelength
- model type: 2 - not used
- model type: 3 - spherical, depth scale - column mass in g/cm²
- model type: 4 - spherical, depth scale - tau at std wavelength
- WLSTD - standard wavelength in Å (relevant for model type 1 and 4)
- SPHERICAL - the same as model type 3 and 4
- RADIUS - reference radius in cm
3rd line - continuous opacities used in calculations following Bob Kurucz convention
1. - absorption by H
2. - absorption by H₂⁺
3. - absorption by H^-
4. - Rayleigh scattering by H
5. - absorption by He
6. - absorption by He⁺
7. - absorption by He^-
8. - Rayleigh scattering by He
9. - absorption by metals for cool stars (Si, Mg, Al, C, Fe)
10. - absorption by metals for intermediate stars (N, O, Si⁺, Mg⁺, Ca⁺)
11. - absorption by metals for hot stars (C, N, O, Ne, Mg, Si, S, Fe 1st to 4th ions)
12. - Thomson scattering by electrons
13. - Rayleigh scattering by H₂
14. - 20. not used
Lines 4-13 - normalized abundances for the first 99 elements in the periodic table: N_atom/N_all where N are number densities. The sum of all abundances is 1. Positive numbers are fractions while negative numbers are log₁₀ of fractions. The last number in line 13 is the number of depth layers in the model.
Lines 14 and down are the model data. Plane-parallel models have 5 columns while spherical have 6.
1. column: depth in column mass or optical depth at standard wavelength
2. column: temperature in K
3. column: number density of free electrons in cm^-3
4. column: number density of all other particles (except electrons) in cm^-3
5. column: density in g/cm³
6. column: (spherical model only): height in cm relative to the reference radius given in the header

Help

Email: marcs (at) astro.uu.se

Frequently Asked Questions (or at least Questions we Expect to Receive):

How do I unpack the tar file?
If you are on a UNIX system you type "tar -xvf file_name". This recreates the individually gzipped files with their complete names. These are unpacked to plain ascii text files by the command "gunzip *.gz"
If you are on a WINDOWS/Mac system you may have to get software for this, e.g. the "Stuffit expander". In order to read and store the plain ascii text files in a useful format the "Emacs" editor is useful. Links to these programmes are given in "Software". (On a Windows XP system, the Notepad editor should display the files with line breaks.)
Why are not the models I would like available?
In many cases the MARCS code does not converge to the desired accuracy, or it crashes during the execution. We do not have the time to check all such cases. The hot, low-gravity stars do not converge because they are not stable; the surface fluxes are too high, "super-Eddington" luminosities.
We have a limited time for maintaining this data base, but we plan to add models as they are documented and computed.