starfit 0.8.2

A stellar abundance matching code

Python package for matching stellar abundance measurements against a database of model stellar explosions. Based on the old IDL code by Alexander Heger.

StarFit can match combined abundances of multiple models. For single stars and combinations of multiple stars, a complete search can be found. For three or more stars, the problem is extremely expensive, so a Genetic Algorithm has been implemented by Conrad Chan to efficiently find an approximate solution.

An online interface (with a subset of functionality) is available at starfit.org.

Installation

Tested with Python 3.10

Optional: A working LaTeX installation and dvipng is required to create plots with LaTeX labels (ideal for publication). Otherwise, Matplotlib's default MathText is used, which may not render all symbols correctly.

From PyPI (recommended)

pip install starfit

The PyPI package includes the necessary data files.

Developer instructions

The data files are not included into the Git repo, and must first be downloaded from the web-server before installing from the Git repo.

git clone [e-mail]:conradtchan/starfit.git
cd starfit

# Download data files
./download-data.sh

# Set environment variable to allow for editable installs
export SETUPTOOLS_ENABLE_FEATURES="legacy-editable"

# "-e" creates an editable install, "[testing]" installs additional dependencies for testing
pip3 install -e .[testing]

# Run all tests
python -m pytest

Usage

Single star matches

starfit.Single fits an abundance pattern to a single model from the database.

Required arguments:

• filename: filename of star. Can be absolute or relative path. The files will also be searched for in the distribution files and in the search path specified by environment variable STARFIT_DATA in subdirectory stars.
• db: database file or tuple of data base files. String or Path object. Can be absolute or relative path. Files will also be searched in the distribution files and in the search path specified by environment variable STARFIT_DATA in subdirectory db.

Optional arguments:

• combine: a list of lists of element charge numbers to treat as combined abundances (e.g. combine the CNO elements)
• z_max: highest element charge number to fit
• z_exclude: element charge numbers to exclude from fit
• z_lolim: elements that are model lower limits (effectively the same as observational upper limits)
• upper_lim: include observational upper limits in data fitting
• cdf: use the uncertainty of upper limits to calculate a cumulative distribution function when calculating error contribution (otherwise treat the upper limit as a simple one-sided 𝛘² error)

import starfit

s = starfit.Single(
    filename = 'HE1327-2326.dat',
    db = 'znuc2012.S4.star.el.y.stardb.gz',
    combine = [[6, 7, 8]],
    z_max = 30,
    z_exclude = [3, 24, 30],
    z_lolim = [21, 29],
    upper_lim = True,
    cdf = True,
    )

s.print()

the print method allows to specify the number of lines to be printed (n), the offset for the first entry to print (n0, default is 0) and the maximum number of columumns to use as a "wide" table (wide, default 12). A format and be specified as "html" or "unicode", plain text otherwise. Default is unicode.

s.print(n0=3, n=1, wide=8, format=None)

The database indices of the best fitting models (sorted from best to worst) are given by:

s.sorted_stars['index']

The corresponding reduced 𝛘² values are:

s.sorted_fitness

The physical properties of the models corresponding to these indices can be accessed using the database:

i_bestfit = s.sorted_stars['index'][0]
s.db.fielddata[i_bestfit]

The chemical yield of the models (and the respective element names) are:

list(zip(s.list_db, s.full_abudata[:, i_bestfit]))

To make the same plots as the web version:

s.plot()

If you want to plot a solution other than the best one, use the parameter index (default: 0) To plot the 5th best soluttion, skipping the first 4, use

s.plot(index=4)

The legend as well as the star name and copyright string can be moved (dragged).

Full multi-star search

starfit.Multi fits an abundance pattern to a combination of models from the database(s). This can take a long time as there can be many combinations.

Additional arguments:

• fixed: Use dilution factors based on the ejecta mass, rather than solving for the optimal dilution ratio of each explosion independently (decreases solve time)
• threads: Number of threads to use. Default is t use CPU could (including hyprthreading)
• nice: Nice level of background threads. Default is 19 (lowest priority on unix systems).
• partition: by default, all data are merged in one big list and all possible combinations (excluding duplicates) are explored. If partition is specified, only combintions form different databases are considered. This can significantly reduce the cost and often may be more what is intended. In this case, the number of data bases needs to match the number of stars (sol_size) matched.

s = starfit.Multi(
    filename = 'HE1327-2326.dat',
    db = (
        'he2sn.HW02.star.el.y.stardb.gz',
        'rproc.just15.star.el.y.stardb.xz',
	),
    z_max = 999,
    z_exclude = [3, 24, 30],
    z_lolim = [21, 29],
    upper_lim = True,
    cdf = True,
    fixed = False,
    sol_size = 2,
    partition = True,
    )

Genetic algorithm

starfit.Ga fits an abundance pattern to a combination of two or more models from the database. The solution is approximate, but approaches the best solution with increased run time.

Additional arguments:

• time_limit: amount of time (in seconds) to search for solution
• sol_size: number of explosion models to find combinations of
• pop_size: GA parameter - number of solutions in the population
• tour_size: GA parameter - number of solutions per tournament selection
• frac_mating_pool: GA parameter - fraction of solutions in the mating pool
• frac_elite: GA parameter - top fraction of elite solutions
• mut_rate_index: GA parameter - mutation rate of the database index
• mut_rate_offset: GA parameter - mutation rate of the dilution factor
• mut_offset_magnitude: GA parameter - size of the mutation of the dilution factor
• local_search: GA parameter - solve for the best dilution factors rather than relying on the GA
• cover: GA parameter - ensure no database sources are skipped unless there are fewer stars than data bases. This can be useful if there is a large disparity in the number of models between the different data bases and if you have a prior that all data bases should be used. Eventually, the genetic algorithm should find all combinations that match best anyway, however.

The default GA parameters should be used unless you really know what you are doing.

s = starfit.Ga(
    filename = 'HE1327-2326.dat',
    db = (
        'he2sn.HW02.star.el.y.stardb.gz',
	'rproc.just15.star.el.y.stardb.xz',
	'znuc2012.S4.star.el.y.stardb.gz',
	),
    combine = [[6, 7, 8]],
    z_max = 30,
    z_exclude = [3, 24, 30],
    z_lolim = [21, 29],
    upper_lim = True,
    cdf = True,
    time_limit = 20,
    sol_size = 3,
    cover = True,
    )

Matching specific star combinations

starfit.Direct allose to find the best fit to pre-selected group, or groups of stars.

Additional arguments:

• stars: List of lists of models. For each model, specify a list of database and index. The database index is 1-based, the index is 0-based.

The following makes to optiisations: a group of models with model index 0 from the first database (1) and model index 1 from the second database; and second, a group of models with model index 2 from the first database (1) and model index 3 from the second database:

s = starfit.Direct(
        filename = 'HE1327-2326.dat',
	db = (
	    'he2sn.HW02.star.el.y.stardb.gz',
	    'rproc.just15.star.el.y.stardb.xz',
	    ),
        stars=[
	    [[1,0], [2,1]],
	    [[1,2], [2,3]]],
    )

The results are sorted by fitness and stored in the returned object as usual, allowing to print and plot the results.

Multiple databases info

By default, data bases are numbered in the order provided. The database numbers are only listed when there is more than one database provided. Database information can be printed using the print_comments method of the solution object:

s.print_comments()

or if the full parameter is specified to the print method

s.print(full=True)

Custom data directory

Custom stellar data and model database files can always be used by providing a full path in the argument. However, users may optionally specify their own data directory using the environment variable STARFIT_DATA for convenience:

export STARFIT_DATA='/your/custom/data'

Files found in the custom data directory will take precedence over the default data directory. Your custom data directory must have the same structure as src/starfit/data, i.e. it should contain the db, ref, and stars directories:

❯ ls
db
ref
stars

Contributing to StarFit

Contributions to the StarFit code are welcome. The master branch is protected and cannot be committed to directly. Instead, please create a Pull Request with your proposed contributions. To make a new branch and set to track origin

git checkout -b <new_brnach>
git push --set-upstream origin <new_branch>

Two automated checks (on Github Actions) must be passed:

1. Code formatting using pre-commit. To ensure your changes are compliant with this project's linters, we recommend installing pre-commit prior to making any commits locally.

pip install pre-commit
pre-commit install

If you have already made non-compliant commits prior to installing pre-commit, then the pre-commit check on Github will fail. To make the code compliant again, run

pre-commit run --all

and also run tests as a first check

python -m pytest

and include these changes in a follow-up commit.

2. Code tests using pytest. New tests can be added to the tests/ directory.

Development branch

Development branches are generated and uploaded to Test PyPI if the version number ends in .dev* where * can be blank or a optional number. For example, '0.3.11.dev22. They may also be flagged as pre-releases.

To install packages from Test PyPI use

pip install --index-url https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple/ starfit

You may include the -pre flag or specify a specific version.

Adding new database files

Database files specified in the .hashlist files in src/starfit/data/db,ref,stars are downloaded from the web server. To add new data files:

1. Add the new files to the web server hosting the data files at /var/www/html/data
2. Generate the hash using shasum -a 256 (or sha256sum)
3. Add an entry into the hash list

When adding new databases into data/db, add corresponding labels into the file data/db/labels and a description of the data base into the file data/db/databases on the web server.

Creating database files

New database files can be made using the StarDB class in autils/stardb.py. A demonstration may be found at src/starfit/example/lc12_stardb.py. This file serves as a demonstration only and will not work as is.

Publishing to PyPI

Github releases will automatically be published to https://pypi.org/project/starfit/