Stellar model atmospheres

An Extract Stellar request needs a model atmosphere. The request form offers two grids of solar-metallicity models, or you can upload your own.

Contents

Stellar model atmospheres

The two grids

ATLAS9 (default): 476 models, Teff 3500-50000 K, log g 0.0-5.0, [M/H] = 0.0, microturbulence 2 km/s. These are the Castelli & Kurucz grid with new opacity distribution functions, from kurucz.harvard.edu/grids.html.

Castelli, F. & Kurucz, R. L. 2003, IAU Symp. 210, Modelling of Stellar Atmospheres, poster A20 - ADS

MARCS: 173 plane-parallel models, Teff 2500-8000 K, log g 3.0-5.5, standard composition with [M/H] = 0.0, microturbulence 1 km/s, from marcs.astro.uu.se.

Gustafsson, B., Edvardsson, B., Eriksson, K. et al. 2008, A&A 486, 951 - ADS

Which model you get

VALD does not interpolate. It uses the grid model nearest to the requested Teff and log g, where 100 K in Teff counts the same as 0.1 dex in log g. A request outside the grid, or in one of its gaps, is therefore not rejected but answered with the nearest edge model. The model actually used is shown as Model atmosphere on the request's status page; check it if your parameters are near the edge of the coverage below.

ATLAS9 coverage

● model present, ○ not in the grid. Low gravities are missing for hot models.

Teff ↓ / log g →	0.0	0.5	1.0	1.5	2.0	2.5	3.0	3.5	4.0	4.5	5.0
3500	●	●	●	●	●	●	●	●	●	●	●
3750	●	●	●	●	●	●	●	●	●	●	●
4000	●	●	●	●	●	●	●	●	●	●	●
4250	●	●	●	●	●	●	●	●	●	●	●
4500	●	●	●	●	●	●	●	●	●	●	●
4750	●	●	●	●	●	●	●	●	●	●	●
5000	●	●	●	●	●	●	●	●	●	●	●
5250	●	●	●	●	●	●	●	●	●	●	●
5500	●	●	●	●	●	●	●	●	●	●	●
5750	●	●	●	●	●	●	●	●	●	●	●
6000	●	●	●	●	●	●	●	●	●	●	●
6250	○	●	●	●	●	●	●	●	●	●	●
6500	○	●	●	●	●	●	●	●	●	●	●
6750	○	●	●	●	●	●	●	●	●	●	●
7000	○	●	●	●	●	●	●	●	●	●	●
7250	○	●	●	●	●	●	●	●	●	●	●
7500	○	●	●	●	●	●	●	●	●	●	●
7750	○	○	●	●	●	●	●	●	●	●	●
8000	○	○	●	●	●	●	●	●	●	●	●
8250	○	○	●	●	●	●	●	●	●	●	●
8500	○	○	○	●	●	●	●	●	●	●	●
8750	○	○	○	●	●	●	●	●	●	●	●
9000	○	○	○	●	●	●	●	●	●	●	●
9250	○	○	○	○	●	●	●	●	●	●	●
9500	○	○	○	○	●	●	●	●	●	●	●
9750	○	○	○	○	●	●	●	●	●	●	●
10000	○	○	○	○	●	●	●	●	●	●	●
10250	○	○	○	○	●	●	●	●	●	●	●
10500	○	○	○	○	●	●	●	●	●	●	●
10750	○	○	○	○	●	●	●	●	●	●	●
11000	○	○	○	○	●	●	●	●	●	●	●
11250	○	○	○	○	●	●	●	●	●	●	●
11500	○	○	○	○	●	●	●	●	●	●	●
11750	○	○	○	○	●	●	●	●	●	●	●
12000	○	○	○	○	○	●	●	●	●	●	●
12250	○	○	○	○	○	●	●	●	●	●	●
12500	○	○	○	○	○	●	●	●	●	●	●
12750	○	○	○	○	○	●	●	●	●	●	●
13000	○	○	○	○	○	●	●	●	●	●	●
14000	○	○	○	○	●	●	●	●	●	●	●
15000	○	○	○	○	○	●	●	●	●	●	●
16000	○	○	○	○	○	●	●	●	●	●	●
17000	○	○	○	○	○	●	●	●	●	●	●
18000	○	○	○	○	○	●	●	●	●	●	●
19000	○	○	○	○	○	●	●	●	●	●	●
20000	○	○	○	○	○	○	●	●	●	●	●
21000	○	○	○	○	○	○	●	●	●	●	●
22000	○	○	○	○	○	○	●	●	●	●	●
23000	○	○	○	○	○	○	●	●	●	●	●
24000	○	○	○	○	○	○	●	●	●	●	●
25000	○	○	○	○	○	○	●	●	●	●	●
26000	○	○	○	○	○	○	●	●	●	●	●
27000	○	○	○	○	○	○	○	●	●	●	●
28000	○	○	○	○	○	○	○	●	●	●	●
29000	○	○	○	○	○	○	○	●	●	●	●
30000	○	○	○	○	○	○	○	●	●	●	●
31000	○	○	○	○	○	○	○	●	●	●	●
32000	○	○	○	○	○	○	○	○	●	●	●
33000	○	○	○	○	○	○	○	○	●	●	●
34000	○	○	○	○	○	○	○	○	●	●	●
35000	○	○	○	○	○	○	○	○	●	●	●
36000	○	○	○	○	○	○	○	○	●	●	●
37000	○	○	○	○	○	○	○	○	●	●	●
38000	○	○	○	○	○	○	○	○	●	●	●
39000	○	○	○	○	○	○	○	○	●	●	●
40000	○	○	○	○	○	○	○	○	○	●	●
41000	○	○	○	○	○	○	○	○	○	●	●
42000	○	○	○	○	○	○	○	○	○	●	●
43000	○	○	○	○	○	○	○	○	○	●	●
44000	○	○	○	○	○	○	○	○	○	●	●
45000	○	○	○	○	○	○	○	○	○	●	●
46000	○	○	○	○	○	○	○	○	○	●	●
47000	○	○	○	○	○	○	○	○	○	●	●
48000	○	○	○	○	○	○	○	○	○	●	●
49000	○	○	○	○	○	○	○	○	○	●	●
50000	○	○	○	○	○	○	○	○	○	○	●

MARCS coverage

Teff ↓ / log g →	3.0	3.5	4.0	4.5	5.0	5.5
2500	●	●	●	●	●	●
2600	●	●	●	●	●	●
2700	●	●	●	●	●	●
2800	●	●	●	●	●	●
2900	●	●	●	●	●	●
3000	●	●	●	●	●	●
3100	●	●	●	●	●	●
3200	●	●	●	●	●	●
3300	●	●	●	●	●	●
3400	●	●	●	●	●	●
3500	●	●	●	●	●	●
3600	●	●	●	●	●	●
3700	●	●	●	●	●	●
3800	●	●	●	●	●	●
3900	●	●	●	●	●	●
4000	●	●	●	●	●	○
4250	●	●	●	●	●	○
4500	●	●	●	●	●	○
4750	●	●	●	●	●	○
5000	●	●	●	●	●	○
5250	●	●	●	●	●	○
5500	●	●	●	●	●	○
5750	●	●	●	●	●	○
6000	●	●	●	●	●	○
6250	●	●	●	●	●	○
6500	●	●	●	●	●	○
6750	●	●	●	●	●	○
7000	●	●	●	●	●	○
7250	●	●	●	●	●	○
7500	●	●	●	●	●	○
7750	●	●	●	○	●	○
8000	○	●	●	●	●	○

In short: use ATLAS9 above 8000 K and for giants (log g < 3.0), MARCS below 3500 K. Where both grids apply, MARCS has the more complete molecular opacities, which matters most for cool stars.

Uploading your own model

For any other metallicity, microturbulence or an interpolated model, choose Upload own model atmosphere... on the form. The file must be in krz format, described at marcs.astro.uu.se/docs.html, and must be plane-parallel (MODEL TYPE= 0); spherical models are rejected. Teff and log g are then taken from the file header. The file name appears in the output header, so a descriptive one (e.g. marcs_p5750_g45_m-0.5.krz) helps.