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Star and orbit

The [star] section configures the host star model and spectral properties. The [orbit] section configures the planetary orbit, tidal evolution, and any satellite.

Submodule documentation: MORS | Obliqua. See also Model description.

Stellar model [star]

Parameter Type Default Description
module str or none "mors" Select star module to use. Choices: none, "mors", "dummy".
mass float 1.0 Stellar mass [M_sun]. Note that for Mors, it should be between 0.1 and 1.25 solar masses. Values outside of the valid range will be clipped. Must be > 0.
age_ini float 0.1 Stellar age at model initialisation, relative to stellar birthline [Gyr]. Must be > 0.
bol_scale float 1.0 Scale factor applied to bolometrically modulate the stellar fluxes. Must be >= 0.0.
bol_scale_duration float 0.0 Duration for which bol_scale is applied [Gyr]. Must be >= 0.0.
bol_scale_start float or none none Stellar age from which bol_scale is applied [Gyr]. 'None' to disable. Must be >= 0.0.

bol_scale only takes effect while the model's stellar age lies within the start-plus-duration interval. So, all three options should be set together. The scaling factor is applied uniformly to all stellar flux terms.

MORS stellar tracks [star.mors]

The MORS module interpolates stellar radius, effective temperature, luminosity, and XUV flux from pre-computed evolutionary tracks as a function of stellar age. Two track families are available: Spada 1 (solar-type) and Baraffe 2 (low-mass M-dwarfs). The phoenix_* parameters are used when spectrum_source = "phoenix": PHOENIX provides synthetic spectra on a grid of metallicity, alpha enhancement, and (optionally) effective temperature.

Parameter Type Default Description
age_now float 4.567 Observed estimated age of the star [Gyr].
star_name str or none none Name of the star, to find appropriate stellar spectrum. See documentation.
star_path str or none none Path to custom stellar spectra. If 'none', star_name will be used to find spectra in default locations.
rot_pcntle float or none 50.0 Rotation, as percentile of stellar population.
rot_period float or none none Rotation rate [days].
tracks str "spada" Stellar evolution track to be used. Choices: "spada", "baraffe".
spectrum_source str or none "phoenix" Source of stellar spectra. Choices: "solar", "muscles", "phoenix", none.
phoenix_FeH float 0.0 Stellar metallicity [Fe/H] to be used for PHOENIX synthetic spectra, if spectrum_source is 'phoenix'.
phoenix_alpha float 0.0 Alpha-element enhancement [alpha/Fe] to be used for PHOENIX synthetic spectra, if spectrum_source is 'phoenix'.
phoenix_radius float or none none Stellar radius [R_sun]. If 'none', radius will be calculated using mors' stellar tracks, if spectrum_source is 'phoenix'. Must be > 0.
phoenix_log_g float or none none Surface gravity [cgs]. If 'none', log g will be calculated will be calculated using mors' stellar tracks, if spectrum_source is 'phoenix'. Must be > 0.
phoenix_Teff float or none none Effective temperature [K]. If 'none', Teff will be calculated will be calculated using mors' stellar tracks, if spectrum_source is 'phoenix'. Must be > 0.

Dummy star [star.dummy]

A fixed-luminosity star with no temporal evolution. Useful for testing and parameter studies where stellar evolution is not relevant.

Parameter Type Default Description
Teff float 5772.0 Observed effective temperature [K].
radius float or none none Observed radius [R_sun].
calculate_radius bool false Calculate the radius using empirical mass-luminosity and mass-radius relation.

Orbital configuration [orbit]

Parameter Type Default Description
module str or none none Select orbit module to use. Choices: none, "dummy", "lovepy".
semimajoraxis float 1.0 Initial semi-major axis of the planet's orbit [AU]. Must be > 0.
eccentricity float 0.0 Initial Eccentricity of the planet's orbit. Must be >= 0 and < 1.
zenith_angle float 48.19 Characteristic angle of incoming stellar radiation, relative to the zenith [deg]. Must be >= 0 and < 90.
s0_factor float 0.375 Scale factor applies to incoming stellar radiation to represent planetary rotation. Must be > 0.
evolve bool false Allow the planet's orbit to evolve based on eccentricity tides?.
axial_period float or none none Planet initial day length [hours], will use orbital period if value is None.
satellite bool false Model a satellite (moon) orbiting the planet and solve for its orbit?.
mass_sat float 7.347e+22 Satellite mass [kg]; the default is the lunar mass. Must be > 0.
semimajoraxis_sat float 300000000.0 Satellite initial semi-major axis [m]. Must be > 0.
instellation_method str "distance" Whether to use the semi-major axis ('distance') or instellation flux ('inst') to define the planet's initial orbit. Choices: "distance", "inst".
instellationflux float 1.0 Instellation flux initially received by the planet in Earth units. Must be > 0.

Dummy tides [orbit.dummy]

Fixed tidal heating rates, useful for parameter studies.

Parameter Type Default Description
H_tide float 0.0 Fixed global heating rate from tides [W kg-1]. Must be >= 0.0.
Phi_tide str "<0.3" Inequality which, if locally true, determines in which regions tides are applied.
Imk2 float 0.0 Imaginary part of k2 Love number, which is usually negative. Must be <= 0.0.

LovePy tides [orbit.lovepy]

Self-consistent tidal heating using viscoelastic Love numbers computed from the interior rheological profile.

Parameter Type Default Description
visc_thresh float 1000000000.0 Minimum viscosity required for heating [Pa s]. Must be > 0.
ncalc int 1000 Number of interpoltaed interior levels to use for solving tidal heating rates. Must be > 100.

Constraints

Cross-field constraints enforced when the config file loads:

  • Instellation method 'inst' is only available with the dummy star module.
  • Orbital evolution cannot be combined with instellation method 'inst'.
  • Planetary orbital evolution and the satellite model are mutually exclusive.
  • A bolometric scaling other than 1 requires bol_scale_start and a positive duration.
  • Validate MORS settings: positive age, spectrum-source requirements, and rotation set by exactly one of percentile or period.
  • Dummy star requires a consistent radius specification and a valid Teff.

See also: Stellar module | Orbit module

  1. Spada, F., Demarque, P., Kim, Y.C. & Sills, A., The radius discrepancy in low-mass stars: single versus binaries, The Astrophysical Journal, 776, 87, 2013. SciX. ↩

  2. Baraffe, I., Homeier, D., Allard, F. & Chabrier, G., New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit, Astronomy & Astrophysics, 577, A42, 2015. SciX. ↩