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Model parameters

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General parameters

Software:

ATLAS 9 / SYNTHE

Software package that was used to produce this model

Effective temperature [K]:

4500.0

Effective surface temperature in Kelvin

Surface gravity [log(CGS)]:

6.0

Base-10 logarithm of surface gravity in CGS

Input data files

Rosseland checksum:

feb6a833e55e5b8f1366dd0a54cf89ae

MD5 checksum of the employed table of Rosseland mass absorption coefficients computed with KAPPAROS

ODF checksum:

2e7a64b47a5979bfa44dbd3dc1169308

MD5 checksum of the employed ODFs (opacity distribution functions) computed with DFSYNTHE

Convection modelling

Convection status:

MLT with overshoot

ATLAS convection treatment. Note that overshooting may be disabled by setting its coefficient to zero (see below) regardless of this parameter

Mixing length [scale height]:

1.25

Convective mixing length in terms of local pressure scale heights

Overshoot coefficient [0..1]:

0.0

Overshooting coefficient between 0 (no overshoot) and 1 (maximum overshoot)

Convective layers:

Number of layers (counting from the bottom) where convection is allowed. This parameter suppresses numerical artifacts when evaluating the Schwarzschild criterion at low optical depths

Opacity settings

NLTE treatment:

Disabled

If disabled, treat all non-LTE (local thermodynamic equilibrium) lines with SYNTHE in LTE. If enabled, the lines may be directed to a different code for a non-LTE treatment

Total lines in spectrum:

105330200

Total number of lines considered in the spectrum calculation by SYNTHE

Molecules status:

Enabled

Include molecules in the ATLAS equilibrium calculation

Elemental composition

Hydrogen mass fraction, X [0..1]:

0.59893

Mass fraction of hydrogen (between 0 and 1)

Helium mass fraction, Y [0..1]:

0.40001

Mass fraction of helium (between 0 and 1)

Metals mass fraction, Z [0..1]:

0.00107

Mass fraction of metals (between 0 and 1)

Metallicity, [M/H] [dex]:

-1.40001

Metallicity in dex compared to solar, [M/H]

Elemental abundances, [A/M] [dex]:

-03.00

-00.00

-00.65

+01.45

-00.00

Elemental abundances of metals in the atmosphere in dex with respect to metallicity-scaled solar values, [A/M]

Stratification

Number of layers:

Number of (plane-parallel) vertical layers in the stratification

Optical depth start:

-6.875

Base-10 logarithm of the shallowest optical depth (tau) in the calculation (upmost layer)

Optical depth step:

0.125

Additive step in optical depth (tau) between adjacent layers in the base-10 logarithmic space

Wavelength sampling

Frequency points:

337

Number of points considered by ATLAS in frequency integrals (e.g. Rosseland opacity)

High frequency point [A]:

90.9

Wavelength of the highest frequency point considered in frequency integrals by ATLAS

Low frequency point [A]:

1599999.9

Wavelength of the lowest frequency point considered in frequency integrals by ATLAS

Wavelength start [A]:

1000.001

Minimum wavelength in the requested spectrum output from SYNTHE in angstroms

Wavelength end [A]:

41999.9961

Maximum wavelength in the requested spectrum output from SYNTHE in angstroms

Resolution:

600000.0

Spectroscopic resolution in the requested spectrum output from SYNTHE

Broadening configuration

ATLAS turbulent velocity [km/s]:

2.0

Turbulent velocity in km/s in the ATLAS calculation. Note that SYNTHE may introduce additional broadening

SYNTHE turbulent velocity [km/s]:

0.0

Turbulent velocity in km/s in the SYNTHE calculation. Applied on top of ATLAS broadening. Velocities add in quadrature

Miscellaneous

Output medium:

Air

Vacuum or air wavelengths in the output spectrum

Feature cut-off:

0.0001

Minimum spectral feature intensity (as a fraction of the continuum) to be considered in the calculation

Synthetic Spectrum

Figure 1. Synthetic spectrum of the atmosphere. Isotropic intensity per unit surface area of the star per unit wavelength per unit solid angle. Shown in light gray is the blackbody spectrum for the same effective temperature as the model (4500.0 K). Selected optical and near-IR photometric bands are highlighted.

Atmosphere Structure

Figure 2. Left: temperature (green) and gas pressure (red) as functions of the optical depth throughout the model atmosphere. Temperature is shown on a linear scale, while both optical depth and pressure are logarithmic. For reference, an alternative horizontal scale is provided with markings in terms of mass column density instead of optical depth. Note that the alternative scale corresponds directly to the optical depth scale and may therefore be irregular (i.e. neither logarithmic nor linear). Right: temperature as a function of pressure. The effective temperature of the model (4500.0 K) is shown in blue in both plots. Strongly convective regions are highlighted.

Solution Convergence

Figure 3. Percent flux error in the model as a function of optical depth. The vertical axis is logarithmic and shows the absolute value of the error, while the sign is provided as a separate plot. Temperature corrections in each iteration are carried out to minimize the error; however, some residuals will remain due to (1) incomplete/inaccurate physics, (2) numerical failures and (3) insufficient number of iterations. For ATLAS models, flux errors below 1% are typically expected throughout the entire atmosphere in a well-converged model. At low temperatures, flux errors up to 10% are sometimes tolerated in localized regions. For PHOENIX models, errors of a few percent are expected in radiative layers. In highly convective regions, the error estimate is not representative of the model convergence and may rise to arbitrarily large values. Well-converged models usually show a smooth transition between the two regimes and are free of oscillations.