fwl-mors 26.7.23

Stellar rotation and activity evolution model

MORS

MORS (Model for Rotation of Stars) is the stellar-evolution module of the PROTEUS coupled atmosphere-interior evolution framework. It models the rotational spin-down and high-energy (X-ray, EUV, Lyman-α) emission of low-mass stars over their lifetimes, following the rotation-activity model of Johnstone, Bartel & Güdel (2021).

Given a stellar mass and an initial rotation rate, or an observed rotation percentile, MORS returns the time evolution of the rotation period, the X-ray, EUV and Lyman-α luminosities, and the bolometric luminosity, radius and effective temperature interpolated from stellar-structure tracks. Within PROTEUS it supplies the stellar XUV history that drives atmospheric escape and photochemistry.

Model

MORS evolves the surface rotation of a low-mass star (0.1-1.25 Msun) with a wind-braking spin-down law calibrated to the rotation distributions of open clusters, then maps rotation to activity through the Rossby-number rotation-activity relation: X-ray luminosity first, then EUV and Lyman-α from empirical band scalings. Structural quantities (bolometric luminosity, radius, effective temperature) are interpolated from Spada et al. (2013) evolutionary tracks by default; Baraffe et al. (2015) tracks (0.01-1.40 Msun, no rotation model) are available as an alternative.

Documentation

Full documentation is at proteus-framework.org/MORS, including:

• Getting started: installation and a quick path to a first run.
• Tutorial: a first stellar-evolution run and how to read its output.
• How-to guides: install, evolve a star, read tracks and activity quantities, compute habitable-zone boundaries, run the tests.
• Explanations: rotation model, X-ray and EUV activity, stellar structure, spectral synthesis, and coupling to PROTEUS.
• API reference and validation anchors: every public function with NumPy-style docstrings, plus the per-source reference-pinned test inventory.

Installation

pip install fwl-mors

Or, for development:

git clone https://github.com/FormingWorlds/MORS.git
cd MORS
pip install -e .[develop,docs]

The docs extra pulls in Zensical so you can build this documentation locally with zensical serve.

Stellar evolution data

MORS ships without the stellar-evolution tracks, which live in the OSF repository. Set the FWL_DATA environment variable to the directory where the data should live, then download the tracks:

export FWL_DATA=/your/local/path/FWL_DATA   # add to ~/.bashrc to persist
mors download all

Quick start

import mors

star = mors.Star(Mstar=1.0, Prot=2.7)  # 1 Msun, initial rotation period at 1 Myr
print(star.Lx(150.0))                  # X-ray luminosity at 150 Myr [erg s-1]

See the first-run tutorial for the full walkthrough.

Citation

If you use MORS in published work, please cite:

• Johnstone, Bartel & Güdel (2021), A&A, 649, A96 (rotation and XUV evolution model)
• Spada et al. (2013), ApJ, 776, 87 (stellar evolution tracks)

If you use the model cluster distribution or percentiles, also cite the rotation-measurement sources in Table 1 of Johnstone et al. (2021).

License

MIT License. MORS is part of the PROTEUS framework.