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Stellar spectra

PROTEUS can use:

  • Observed spectra from MUSCLES / Mega-MUSCLES and NREL (for the Sun)
  • Synthetic PHOENIX spectra

By default, observed spectra are searched in:

  • $FWL_DATA/stellar_spectra/MUSCLES – MUSCLES / Mega-MUSCLES stars
  • $FWL_DATA/stellar_spectra/solar – solar spectra (modern, past, future)

To see which files you have installed, run for example:

ls $FWL_DATA/stellar_spectra/MUSCLES
ls $FWL_DATA/stellar_spectra/solar

For PHOENIX spectra, files are stored under: $FWL_DATA/stellar_spectra/PHOENIX, where each subdirectory corresponds to a metallicity / alpha combination, e.g. FeH-0.5_alpha+0.0/.

Using solar spectra

To use the modern NREL observed spectrum of the Sun, set spectrum_source = "solar" or do not set the parameter at all, and set star_name = "sun".

To use a different solar spectrum, for example a 'young sun' spectrum, there are VPL spectra available by Claire et al. (2012). In this case, set spectrum_source = "solar" and choose one of the following options for star_name:

  • Sun0.6Ga A young sun of 0.6 Gyr ago (age ~ 4.0 Gyr)
  • Sun1.8Ga A young sun of 1.8 Gyr ago (age ~ 2.8 Gyr)
  • Sun2.4Ga A young sun of 2.4 Gyr ago (age ~ 2.2 Gyr)
  • Sun2.7Ga A young sun of 2.7 Gyr ago (age ~ 1.9 Gyr)
  • Sun3.8Ga A young sun of 3.8 Gyr ago (age ~ 800 Myr)
  • Sun4.4Ga A young sun of 4.4 Gyr ago (age ~ 200 Myr)
  • Sun5.6Gyr A future sun of an age of 5.6 Gyr
  • SunModern A modern solar spectrum, can be chosen as an alternative to the NREL spectrum listed above.

The Sun

  • Star name: sun
  • URL: https://en.wikipedia.org/wiki/Sun
  • Spectral type: G2V
  • Teff: 5772 K
  • Age: 4.6 Gyr
  • Luminosity: 1.0 L☉
  • Mass: 1.0 M☉
  • Radius: 1.0 R☉
  • Source: Gueymard 2003, NREL, Claire et al. 2012

Using a (Mega-)MUSCLES observed spectrum

PROTEUS can use observed stellar spectra from the MUSCLES and Mega-MUSCLES surveys. To use one of these observed spectra:

  • Set spectrum_source = "muscles"
  • Set star_name to one of the keys listed below (these names must match the installed spectrum filenames / dataset keys; many targets have multiple common aliases, but PROTEUS expects the specific star_name string shown here).

By default, PROTEUS looks for MUSCLES/Mega-MUSCLES spectra under:

  • $FWL_DATA/stellar_spectra/MUSCLES

Files are saved as <star_name>.txt, e.g. trappist-1.txt.

Epsilon Eridani

  • Star name: v-eps-eri
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/eps%20Eri
  • Spectral type: K2V
  • Teff: 5020 K
  • Age: 400–800 Myr
  • Luminosity: 0.32 L☉
  • Mass: 0.82 M☉
  • Radius: 0.759 R☉
  • Source: MUSCLES

GJ 1132

  • Star name: gj1132
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/GJ%201132
  • Spectral type: M4.5 V
  • Teff: 3229 K
  • Age: ?
  • Luminosity: 0.005 L☉
  • Mass: 0.195 M☉
  • Radius: 0.221 R☉
  • Source: Mega-MUSCLES

GJ 1214

  • Star name: gj1214
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/GJ%201214
  • Spectral type: M4 V
  • Teff: 3100 K
  • Age: 5–10 Gyr
  • Luminosity: 0.00351 L☉
  • Mass: 0.182 M☉
  • Radius: 0.216 R☉
  • Source: MUSCLES

HD 85512

  • Star name: hd85512
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/HD%2085512
  • Spectral type: M0V
  • Teff: ~4400 K
  • Age: ~6 Gyr
  • Luminosity: 0.17 L☉
  • Mass: 0.69 M☉
  • Radius: 0.69 R☉
  • Source: MUSCLES

HD 97658

  • Star name: hd97658
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/HD%2097658%20b#planet_HD-97658-b_collapsible
  • Spectral type: K1V
  • Teff: 5212 K
  • Age: 3.9 Gyr
  • Luminosity: 0.351 L☉
  • Mass: 0.773 M☉
  • Radius: 0.728 R☉
  • Source: MUSCLES

L 98-59

  • Star name: l-98-59
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/L%2098-59
  • Spectral type: M3V
  • Teff: 3415 K
  • Age: ~5 Gyr
  • Luminosity: 0.012 L☉
  • Mass: 0.292 M☉
  • Radius: 0.316 R☉
  • Source: Mega-MUSCLES

TRAPPIST-1

  • Star name: trappist-1
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/TRAPPIST-1
  • Spectral type: M8V
  • Teff: 2566 K
  • Age: ~8 Gyr
  • Luminosity: 0.000553 L☉
  • Mass: 0.0898 M☉
  • Radius: 0.1192 R☉
  • Source: Mega-MUSCLES

GJ 849

  • Star name: gj849
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/GJ%20849
  • Spectral type: M3.5V
  • Teff: 3467 K
  • Age: >3 Gyr
  • Luminosity: 0.02887 L☉
  • Mass: 0.45 M☉
  • Radius: 0.45 R☉
  • Source: Mega-MUSCLES

WASP-43

  • Star name: wasp-43
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/WASP-43
  • Spectral type: K7V
  • Teff: ~4100 K
  • Age: ~7 Gyr
  • Luminosity: ~0.15 L☉
  • Mass: ~0.65 M☉
  • Radius: ~0.76 R☉
  • Source: MUSCLES extension

WASP-77 A

  • Star name: wasp-77a
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/WASP-77%20A
  • Spectral type: G8V
  • Teff: ~5600 K
  • Age: ~6 Gyr
  • Luminosity: ~0.74 L☉
  • Mass: ~0.90 M☉
  • Radius: ~0.91 R☉
  • Source: MUSCLES extension

GJ 15 A

  • Star name: gj15a
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/GJ%2015
  • Spectral type: M1–M2V
  • Teff: ~3700 K
  • Age: ?
  • Luminosity: ~0.021 L☉
  • Mass: ~0.40 M☉
  • Radius: ~0.38 R☉
  • Source: Mega-MUSCLES

GJ 163

  • Star name: gj163
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/gj%20163%20b
  • Spectral type: M3.5V
  • Teff: ~3300–3500 K
  • Age: ~2-10 Gyr
  • Luminosity: ~0.02 L☉
  • Mass: ~0.40 M☉
  • Radius: ~0.41 R☉
  • Source: Mega-MUSCLES

GJ 176 (HD 285968)

  • Star name: gj176
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/HD%20285968
  • Spectral type: M2.5V
  • Teff: ~3700 K
  • Age: ~4 Gyr
  • Luminosity: 0.034 L☉
  • Mass: 0.51 M☉
  • Radius: 0.48 R☉
  • Source: MUSCLES

GJ 436

  • Star name: gj436
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/GJ%20436
  • Spectral type: M2.5-M3V
  • Teff: ~3600 K
  • Age: ~6–15 Gyr
  • Luminosity: 0.023 L☉
  • Mass: 0.44 M☉
  • Radius: 0.42 R☉
  • Source: MUSCLES

GJ 551 (Proxima Centauri)

  • Star name: gj551
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/alpha%20Cen
  • Spectral type: M5.5Ve
  • Teff: ~2900-3000 K
  • Age: ~4.8 Gyr
  • Luminosity: 0.0015 L☉
  • Mass: 0.12 M☉
  • Radius: 0.14 R☉
  • Source: MUSCLES

GJ 581

  • Star name: gj581
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/GJ%20581
  • Spectral type: M3V
  • Teff: ~3500 K
  • Age: ~4 Gyr
  • Luminosity: ~0.012 L☉
  • Mass: ~0.30 M☉
  • Radius: ~0.30 R☉
  • Source: MUSCLES

GJ 649

  • Star name: gj649
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/GJ%20649
  • Spectral type: M1-M2V
  • Teff: ~3700 K
  • Age: ?
  • Luminosity: ~0.044 L☉
  • Mass: 0.51 M☉
  • Radius: 0.50 R☉
  • Source: Mega-MUSCLES

GJ 667 C

  • Star name: gj667c
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/GJ%20667C
  • Spectral type: M1.5V
  • Teff: ~3700 K
  • Age: >2 Gyr
  • Luminosity: ~0.014 L☉
  • Mass: ~0.33 M☉
  • Radius: ~0.32–0.42 R☉
  • Source: MUSCLES

GJ 674

  • Star name: gj674
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/GJ%20674
  • Spectral type: M2.5V
  • Teff: ~3400–3600 K
  • Age: ~0.5–3 Gyr
  • Luminosity: 0.017 L☉
  • Mass: 0.35 M☉
  • Radius: 0.36 R☉
  • Source: Mega-MUSCLES

GJ 676 A

  • Star name: gj676a
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/GJ%20676A
  • Spectral type: M0V
  • Teff: ~3800–4000 K
  • Age: ?
  • Luminosity: 0.083 L☉
  • Mass: 0.63 M☉
  • Radius: 0.65 R☉
  • Source: Mega-MUSCLES

GJ 699 (Barnard’s Star)

  • Star name: gj699
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/barnard's%20star
  • Spectral type: M3.5-4.0V
  • Teff: ~3200-3300 K
  • Age: ~10 Gyr
  • Luminosity: 0.0035 L☉
  • Mass: ~0.16 M☉
  • Radius: ~0.19 R☉
  • Source: Mega-MUSCLES

GJ 729 (Ross 154)

  • Star name: gj729
  • URL: https://simbad.cds.unistra.fr/simbad/sim-id?Ident=GJ+729
  • Spectral type: M3.5V
  • Teff: ~3200–3300 K
  • Age: <1–2 Gyr
  • Luminosity: ~0.004–0.005 L☉
  • Mass: ~0.18 M☉
  • Radius: ~0.20 R☉
  • Source: Mega-MUSCLES

GJ 832

  • Star name: gj832
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/HIP%20106440
  • Spectral type: M1-M3V
  • Teff: ~3500-3500 K
  • Age: ~4–12 Gyr
  • Luminosity: ~0.03 L☉
  • Mass: 0.45 M☉
  • Radius: 0.45 R☉
  • Source: MUSCLES

GJ 876

  • Star name: gj876
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/GJ%20876
  • Spectral type: M2-4V
  • Teff: ~3200–3300 K
  • Age: ~2–15 Gyr
  • Luminosity: ~0.013 L☉
  • Mass: ~0.37 M☉
  • Radius: ~0.37 R☉
  • Source: MUSCLES

HAT-P-12

  • Star name: hat-p-12
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/HAT-P-12
  • Spectral type: K4V
  • Teff: 4500-4800 K
  • Age: 2-14 Gyr
  • Luminosity: ~0.20 L☉
  • Mass: 0.74 M☉
  • Radius: 0.70 R☉
  • Source: MUSCLES extension

HAT-P-26

  • Star name: hat-p-26
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/HAT-P-26
  • Spectral type: K1V
  • Teff: ~5050 K
  • Age: 4-12 Gyr
  • Luminosity: ~0.44 L☉
  • Mass: 0.85 M☉
  • Radius: 0.86 R☉
  • Source: MUSCLES extension

HD 149026

  • Star name: hd-149026
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/HD%20149026%20b#planet_HD-149026
  • Spectral type: G0V
  • Teff: ~6100-6200 K
  • Age: ~2-3 Gyr
  • Luminosity: ~2.6 L☉
  • Mass: ~1.14 M☉
  • Radius: ~1.46 R☉
  • Source: MUSCLES extension

HD 40307

  • Star name: hd40307
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/HD%2040307
  • Spectral type: K2.5V
  • Teff: ~4800-5000 K
  • Age: ~2–5 Gyr
  • Luminosity: ~0.22 L☉
  • Mass: ~0.79 M☉
  • Radius: ~0.71 R☉
  • Source: MUSCLES

L 678-39 (GJ 357)

  • Star name: l-678-39
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/GJ%20357
  • Spectral type: M2.5V
  • Teff: ~3500 K
  • Age: ?
  • Luminosity: 0.0017 L☉
  • Mass: ~0.34 M☉
  • Radius: ~0.34 R☉
  • Source: MUSCLES extension

L 980-5

  • Star name: l-980-5
  • URL: https://simbad.u-strasbg.fr/simbad/sim-id?Ident=l+980-5
  • Spectral type: M4V
  • Teff: ?
  • Age: ?
  • Luminosity: ?
  • Mass: ?
  • Radius: ?
  • Source: Mega-MUSCLES

LHS 2686

  • Star name: lhs-2686
  • URL: https://simbad.cds.unistra.fr/simbad/sim-id?Ident=LHS+2686
  • Spectral type: M5V
  • Teff: ?
  • Age: ?
  • Luminosity: ?
  • Mass: ?
  • Radius: ?
  • Source: Mega-MUSCLES

LP 791-18

  • Star name: lp-791-18
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/LP%20791-18
  • Spectral type: M6V
  • Teff: ~2960 K
  • Age: > 0.5 Gyr
  • Luminosity: ~0.002 L☉
  • Mass: 0.139 M☉
  • Radius: 0.182 R☉
  • Source: MUSCLES extension

TOI-193 (LTT 9779)

  • Star name: toi-193
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/LTT%209779
  • Spectral type: G7V
  • Teff: ~5400-5500 K
  • Age: ~2 Gyr
  • Luminosity: ~ 0.7 L☉
  • Mass: ~1.0 M☉
  • Radius: ~0.95 R☉
  • Source: MUSCLES extension

WASP-127

  • Star name: wasp-127
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/WASP-127
  • Spectral type: G5 (subgiant-like)
  • Teff: ~5600-5800 K
  • Age: ~10–12 Gyr
  • Luminosity: ~1.8 L☉
  • Mass: ~0.95–1.10 M☉
  • Radius: ~1.3 R☉
  • Source: MUSCLES extension

WASP-17

  • Star name: wasp-17
  • URL: https://exoplanetarchive.ipac.caltech.edu/overview/WASP-17
  • Spectral type: F4–F6V
  • Teff: ~6550 K
  • Age: ~3 Gyr
  • Luminosity: ~4 L☉
  • Mass: 1.35 M☉
  • Radius: 1.57 R☉
  • Source: MUSCLES extension

Using a PHOENIX synthetic spectrum

To use a Med-Res PHOENIX synthetic spectrum, set:

  • spectrum_source = "phoenix"

PHOENIX spectra are stored under: - $FWL_DATA/stellar_spectra/PHOENIX/

Each subdirectory corresponds to a metallicity / alpha combination, e.g. FeH-0.5_alpha+0.0/.

Parameters

PHOENIX models are defined on a grid in:

  • Teff (K) — effective temperature
  • log_g (dex) — surface gravity
  • FeH (dex) — metallicity
  • alpha (dex) — alpha enhancement

In addition, PROTEUS needs the stellar radius:

  • radius (R☉)

This is used to scale the model spectrum (surface flux) to the flux at 1 AU.

You can set these under star.mors in your config file.

Defaults / fallbacks

  • If FeH and/or alpha are not set, they default to solar (0.0).
  • If Teff, log_g, and/or radius are not set, they are estimated by the stellar evolution module (mors) from the stellar mass (if provided).

Using a custom stellar spectrum

If you prefer to use your own stellar spectrum, you can input its filepath under the parameter star_path. Make sure you input its absolute path, even if it is in the $FWL_DATA directory. NOTE: this parameter will override all other stellar spectrum config parameters!

There are a few things to take into account when using a custom stellar spectrum:

  • The file should be a two-column ASCII file, with the first column the wavelength in nm, and the second column the flux in erg/s/cm^2/nm. Headers should be indicated with #.
  • The spectrum must be scaled to 1 AU.

Surfaces

Single-scattering albedo data taken from Hammond et al., (2024): Zenodo data. Available options can be found by running the command: 

ls $FWL_DATA/surface_albedos/Hammond24

Exoplanet population data

These are obtained from the DACE PlanetS database (Parc et al., 2024).

Mass-radius relations

These are obtained from Zeng et al., 2019.