MUSCLES

The MUSCLES family of surveys provide complete spectra, from X-ray to IR wavelengths, for use in exoplanet atmosphere modeling. Data sources for the various regions of the spectra are:

• X-rays: Chandra/XMM-Newton/Swift and APEC models (Smith et al. 2001)
• EUV: Empirical scaling relation based on Lya flux (Linsky et al. 2014) and/or Differential Emission Measure models (Duvvuri et al. 2021)
• Lya: Reconstructed from the model fit to the line wings (Youngblood et al., 2016
• FUV - blue visible: HST COS and STIS observations
• Visible - IR: Synthetic photospheric spectra from PHOENIX atmosphere models (Husser et al. 2013 and Allard 2016)

Data Releases

Release of Mega-MUSCLES Extension, Version 2.5 (v25, Jun. 27 2025)

This data release supersedes the v23 release. A full description of the Mega-MUSCLES SEDs is presented in Mega-MUSCLES paper 3 (Wilson et al. 2025). Refer to the README file to see major differences between MUSCLES and this release of Mega-MUSCLES. The target list of v25 includes GJ1132, GJ15A, GJ163, GJ674, GJ676A, GJ699, GJ729, GJ849, GJ649, L 980-5, LHS-2686, and Trappist-1.

Release of MUSCLES Extension, Version 2.4 (v24, Sep. 06 2023)

The MUSCLES Extension SEDs are similar to the MUSCLES SEDs and follow the same file naming conventions. Refer to the README file to see major differences between MUSCLES and this release of Mega-MUSCLES.  The target list of v24 includes WASP-127, WASP-77A, WASP-43, WASP-17, TOI-193, LP 791-18, L 678-39, L 98-59, HD 149026, Hat-P-26, and HAT-P-12.

Release of Mega-MUSCLES, Version 2.3 (v23, Mar.17 2022)

The initial release of the Mega-MUSCLES SED is similar to the MUSCLES SEDs, and follows the same file name conventions. Refer to the README file to see major differences between MUSCLES and this release of Mega-MUSCLES.  A full description of the production of the TRAPPIST-1 SED is presented in Wilson et al. 2021, with the other Mega-MUSCLES SEDs following mostly the same techniques. The target list of v25 includes GJ1132, GJ15A, GJ163, GJ674, GJ676A, GJ699, GJ729, GJ849, GJ649, L 980-5, LHS-2686, and Trappist-1.

Release of Proxima Centauri (GJ 551, v22)

In response to popular demand after the announcement of the discovery of a habitable-zone planet orbiting Prox Cen, the team added Prox Cen to the MUSCLES sample and created an SED from archival data using a methodology consistent with the other MUSCLES SEDs. They highly encourage users of the Prox Cen spectra to read the  notes on the reduction of the Prox Cen spectra, as they address an important issue regarding the stellar effective temperature and bolometric flux.

Release of Semi-Empirical Models 

Also available for download is a synthetic spectrum of the MUSCLES M2 dwarf GJ 832 from Fontenla et al. 2016. The synthetic spectrum was created from a one-dimensional model of the stellar atmosphere that incorporates non-LTE radiative transfer techniques and many molecular lines. The synthetic spectrum covers 1 Å - 1 mm at a resolving power R = 100,000 (denoted by "r1e5" in the file names). A single resolution element equals two wavelength samples. For consistency with the MUSCLES data products, the synthetic spectrum's wavelength is in Angstroms and the flux is reported as would be observed from Earth (erg/cm2/s/Å) under the assumption that the stellar radius = 0.499 R_solar (Houdebine 2010) and distance = 4.95 pc (van Leeuwen 2007). Note that Houdebine et al. 2016 determine GJ 832's stellar radius to be 0.458 ± 0.039 R_solar. The atomic and molecular transitions appear at their laboratory rest wavelengths (vacuum). Semi-empirical models of the other 10 MUSCLES stars as well as Proxima Centauri and TRAPPIST-1 are coming soon. If you utilize the GJ 832 synthetic spectrum, please cite Fontenla et al. 2016.

Release of MUSCLES, Version 2.2 (v22)

The target list of v22 includes GJ1214, GJ832, GJ176, GJ436, GJ581, GJ667C, GJ876, HD 40307, HD 85512, HD 97658, and Eps Eri.

MAST Portal and Astroquery

The MUSCLES data are available in the MAST Search Portal (web-based, cross-mission search interface) and Astroquery (Python package to search for and download files from Python scripts you write) except the semi-empirical models, which are available to directly download using the Semi-Empirical Synthetic Spectra table below.

• In the MAST Search Portal, set the Provenance Name filter to MUSCLES in an Advanced Search to find these data. A direct Portal link to MUSCLES data is provided here as well.
• The user guide for how to search and download products using the MAST Portal is available here.
• For Astroquery, the following example code demonstrates how to search for and download these products. This code assumes that you want to download all products from this HLSP, so you may want to consider narrowing down your search for large HLSPs (> 10 GB) or those with many individual files (> 10k). You can find more astroquery.mast tutorials here.

from astroquery.mast import Observations
all_obs = Observations.query_criteria(provenance_name="muscles")
data_products = Observations.get_product_list(all_obs)
Observations.download_products(data_products)

• MAST Portal

  

  A web-based interface for cross-mission searches of data at MAST or the Virtual Observatory

  Portal

• MAST Astroquery

  

  Search for and retrieve MUSCLES data products programmatically.

  MAST Astroquery

Semi-Empirical Synthetic Spectra

Save the curl script below in the directory where you want the data files to be stored, then open a shell terminal and execute the script using the following command.

bash hlsp_muscles_model_multi_gj832_na_v1_synth-spec.sh