MARCS is the acronym for Model Atmospheres with a Radiative and Convective Scheme.
This is a grid of one-dimensional, hydrostatic, plane-parallel and spherical LTE model atmospheres. These may be used together with atomic and molecular spectral line data and software for radiative transfer to generate synthetic stellar spectra.
The MARCS site contains about 52,000 stellar atmospheric models of spectral types F, G, K, and M
in 3 different formats and also flux sample files indicating rough surface fluxes.
The data files are downloadable in limited amounts in the form of tar archives after registration.
We ask users to cite the basic reference containing a description of the models:
Gustafsson B., Edvardsson B., Eriksson K., Jørgensen U.G.,
Nordlund Å., Plez B. 2008, Astronomy & Astrophysics 486, 951.
MARCS low-resolution sampled fluxes of F and G type models were compared to six observational
data bases by Edvardsson (2008).
Synthetic Strömgren uvby-Hβ colours of MARCS fluxes were
compared to those observed for field- and globular cluster stars by
Önehag et al. (2009).
News
September 2024: The search functionality has been retired at the Uppsala website and the models and auxiliary data can now be downloaded directly.
2020: The Montpellier site for MARCS can be found at https://marcs.oreme.org/
April 2018: The ".mod" and ".krz" model column mass, "RHOX", scale (that is not used in MARCS or in its spectrum synthesis relatives BSYN or Turbospectrum) were recalculated by taking the sphericity effects into account for spherical models and actually summing up (integrating) the mass above one cm^{2} at each depth. Previously RHOX ws simply calculated as the total pressure divided by the models' nominal g (surface acceleration of gravity). For consistency the plane-parallel models were also recalculated accordingly.
April 2018: 5 models were also replaced, listed here.
April 2012:
The ".mod" models were pruned from some unphysical data and one digit added to
values of pressures and density. The "readmarcs.f" programme was adjusted accordingly.
July 2011:
The ".krz" model number densities (table column 4) were corrected by subtraction
of the electron number densities from the total particle number densities.
This has a negligibly small effect below 5500 K.
February 2011:
A small subgrid of 280 spherical red supergiant (RSG) models was added.
Their masses are 15 M_{Sun}, the effective temperatures range from 3300
to 4500 K, the logarithmic surface gravities from −0.5 to +1.0, the
microturbulence parameter is 5 km/s, and the overall metallicities range from
−1.0 to +0.5.
The relative elemental abundances are all solar which places the metal-poor
RSG models in the "alpha-poor" metallicity class and those with solar and higher
overall metallicity in the "standard" class.
References