ucdmcmc 1.1

MCMC fitting code for low temperature atmosphere spectra

UCDMCMC

Markov Chain Monte Carlo (MCMC) fitting code for low-temperature stars, brown dwarfs ande extrasolar planet spectra, tuned particularly to the near-infrared.

INSTALLATION NOTES

ucdmcmc can be installed from pip:

pip install ucdmcmc

or from git:

git clone
cd ucdmcmc
python -m setup.py install

It is recommended that you install in a conda environment to ensure the dependencies do not conflict with your own installation

conda create -n ucdmcmc python=3.13
conda activate ucdmcmc
pip install ucdmcmc

A check that this worked is that you can import ucdmcmc into python/jupyter noteobook, and that the ucdmcmc.MODEL_FOLDER points to the models folder that was downloaded

ucdmcmc uses the following extenal packages:

• astropy
• astroquery
• corner
• emcee
• matplotlib
• numpy<2.0
• pandas
• tables
• requests
• scipy
• statsmodels
• tqdm

Optionally install SPLAT

To generate new model sets using the built-in generateModels() function, you will need to install SPLAT (note: this is not necessary for the other functionality in this code). SPLAT is not automatically installed on setup. The instructions are essentially the same:

git clone https://github.com/aburgasser/splat.git
cd splat
python -m pip install .

See https://github.com/aburgasser/splat for additional instructions

Models

ucdmcmc comes with a starter set of models that play nicely with the code. An extended set can be downloaded from https://spexarchive.coolstarlab.ucsd.edu/ucdmcmc/

Spectra

ucdmcmc comes with a starter set of spectra for the following instruments:

• EUCLID: TBD
• NIR: TRAPPIST1 spectrum from Davoudi et al. (2024) https://ui.adsabs.harvard.edu/abs/2024ApJ...970L...4D/abstract
• SPEX-PRISM: 2MASS J0559-1404 from Burgasser et al. (2006) https://ui.adsabs.harvard.edu/abs/2006ApJ...637.1067B/abstract
• JWST-NIRSPEC-PRISM: UNCOVER 33436 from Burgasser et al. (2024) https://ui.adsabs.harvard.edu/abs/2024ApJ...962..177B/abstract
• JWST-NIRSPEC-G395H: TBD
• JWST-MIRI-LRS: TBD
• JWST-NIRSPEC-MIRI: Combined NIRSpec/PRISM and MIRI/LRS of SDSS J1624+0029 from Beiler et al. (2024) https://ui.adsabs.harvard.edu/abs/2024arXiv240708518B/abstract

Usage

[TBD examples]

Citing the code

[TBD]

ucdmcmc and its antecedents has been used in the following publications:

• Burgasser et al. (2024): https://ui.adsabs.harvard.edu/abs/2024ApJ...962..177B/abstract
• Lueber & Burgasser (2025): https://ui.adsabs.harvard.edu/abs/2025ApJ...988...31L/abstract