Atmosphere

For the spectral synthesis PySME needs a model atmosphere to perform the radiative transfer in. PySME does not come with a set of atmospheres in each distribution but instead uses the LFS (See lfs) to fetch only the required model atmosphere when run.

If you want to provide your own model atmosphere file, it should be present in ~/.sme/atmospheres/.

Each atmosphere model file describes a grid of models, on which we then linearly interpolate to the desired stellar parameters. Sometimes we dare extrapolate from this grid as well, but in that case, we always show a warnning.

Note that the atmosphere also contains a seperate set of stellar parameters, which is usually the same as that of the sme structure, but can be different, if for example the atmosphere is embedded, i.e. fixed, or has not been calculated yet.

The atmopshere object has the following fields:

Field name	Description	Allowed values or [Unit]
teff	Effective Temperature	[K]
logg	Surface Gravity	[log(cgs)]
monh	Metallicity
abund	The individual abundances (see abund)
vsini	Projected Rotational velocity	[km/s]
vmic	Microturbulence velocity	[km/s]
vmac	Macroturbulence velocity	[km/s]
source	Filename of the atmosphere grid	see lfs
depth	The depth scale to use for calculations.	RHOX or TAU
interp	The depth scale to use for interpolation.	RHOX or TAU
geom	The geometry of the atmosphere.	Plane Parallel 'PP' or Spherical 'SPH'
method	The method to use for interpolation	'grid' for a model grid or 'embedded' if only a single atmosphere is given
rhox	Mass column at each tabulated depth in the atmosphere	[\(\mathrm{g~cm^{-2}}\)]
tau	Continuum optical depth at each tabulated depth in the atmosphere
temp	Temperature at each tabulated depth in the atmosphere	[K]
xna	Atomic number density (including atomic components of molecules) at each tabulated depth in the atmosphere.	[\(\mathrm{cm^{-3}}\)]
xne	Electron number density at each tabulated depth in the atmosphere	[\(\mathrm{cm^{-3}}\)]
rho	Mass density at each tabulated depth in the atmosphere.	[\(\mathrm{g~cm^{-3}}\)]
height	Height above or below radius at each tabulated depth in a spherical atmosphere.	[cm]
radius	Stellar radius corresponding to height of zero in a spherical atmosphere	[cm]
vturb	Turbulent velocity used to generate the atmosphere	[km/s]
lonh	Ratio of mixing length to pressure scale height (`/H) used to generate the atmosphere.
wlstd	Wavelength for continuum optical depth scale.	Å, Default value: 5000Å
opflag	Flags that indicate whether to enable various opacity packages during the radiative transfer calculation

Atmosphere grids:

• recommended:

  • marcs2012.sav (Gustafsson et al. 2008)

  • marcs2012p_t0.0.sav

  • marcs2012p_t1.0.sav

  • marcs2012p_t2.0.sav

  • marcs2012s_t1.0.sav

  • marcs2012s_t2.0.sav

  • marcs2012s_t5.0.sav

  • marcs2012t00cooldwarfs.sav

  • marcs2012t01cooldwarfs.sav

  • marcs2012t02cooldwarfs.sav

• deprecated:

  • atlas12.sav

  • atlas9_vmic0.0.sav

  • atlas9_vmic2.0.sav

  • ll_vmic2.0.sav

Grid plots