Scatfit: Scattering fits of time domain radio signals (Fast Radio Bursts or pulsars)

This repository contains code to fit Fast Radio Burst or pulsar profiles to measure scattering and other parameters. The code is mainly developed for Python 3, but Python 2 from version 2.7 onwards should work fine.

Author

The software is primarily developed and maintained by Fabian Jankowski. For more information feel free to contact me via: fabian.jankowski at cnrs-orleans.fr.

Paper

The corresponding paper (Jankowski et al. 2023, MNRAS) is available via this NASA ADS link.

Citation

If you make use of the software, please add a link to this repository and cite our corresponding paper. See above and the CITATION and CITATION.bib files.

The code is also listed in the Astrophysics Source Code Library (ASCL).

Installation

The easiest and recommended way to install the software is through pip from the central PyPI index by running:

pip install scatfit

This will install the latest release and all its dependencies. If you need a more recent version of the software, install it directly from its GitHub software repository. For instance, to install the master branch of the code, use the following command:

pip install git+https://github.com/fjankowsk/scatfit.git@master

This will also automatically install all dependencies.

Please verify that your installation works as expected by downloading a pre-generated SIGPROC filterbank file with synthetic data that comes bundled with the GitHub repository:

wget https://github.com/fjankowsk/scatfit/raw/master/extra/fake_burst_500_DM.fil

Then run the main analysis on the filterbank data file like this:

scatfit-fitfrb fake_burst_500_DM.fil 500.0 --fitscatindex --fscrunch 128 --fast

You should see several diagnostic windows open. The terminal output should show an updated DM close to 500 pc cm$^{-3}$, a scattering index near -4.0, and a scattering time at 1 GHz of about 20 ms.

Documentation

Further documentation of the software is available on our dedicated Read the docs website.

Usage

$ scatfit-fitfrb -h
usage: scatfit-fitfrb [-h] [--compare] [--binburst bin] [--fscrunch factor] [--tscrunch factor] [--fast] [--fitrange start end]
                      [--fitscatindex]
                      [--smodel {unscattered,scattered_isotropic_analytic,scattered_isotropic_convolving,scattered_isotropic_bandintegrated,scattered_isotropic_afb_instrumental,scattered_isotropic_dfb_instrumental}]
                      [--showmodels] [--snr snr] [--publish] [-z start end]
                      filename dm

Fit a scattering model to FRB data.

positional arguments:
  filename              The name of the input filterbank file.
  dm                    The dispersion measure of the FRB.

options:
  -h, --help            show this help message and exit
  --compare             Fit an unscattered Gaussian model for comparison. (default: False)
  --binburst bin        Specify the burst location bin manually. (default: None)
  --fscrunch factor     Integrate this many frequency channels. (default: 256)
  --tscrunch factor     Integrate this many time samples. (default: 1)
  --fast                Enable fast processing. This reduces the number of MCMC steps drastically. (default: False)
  --fitrange start end  Consider only this time range of data in the fit. Increase the region for wide or highly-scattered bursts.
                        Ensure that most of the scattering tail is included in the fit. (default: [-200.0, 200.0])
  --fitscatindex        Fit the scattering times and determine the scattering index. (default: False)
  --smodel {unscattered,scattered_isotropic_analytic,scattered_isotropic_convolving,scattered_isotropic_bandintegrated,scattered_isotropic_afb_instrumental,scattered_isotropic_dfb_instrumental}
                        Use the specified scattering model. (default: scattered_isotropic_analytic)
  --showmodels          Show comparison plot of scattering models. (default: False)
  --snr snr             Only consider sub-bands above this S/N threshold. (default: 3.8)
  --publish             Output plots suitable for publication. (default: False)
  -z start end, --zoom start end
                        Zoom into this time region. (default: [-50.0, 50.0])

$ scatfit-simpulse -h
usage: scatfit-simpulse [-h]

Simulate scattered pulses.

options:
  -h, --help  show this help message and exit

Profile scattering models

Several profile scattering models, i.e. pulse broadening functions and instrumental contributions, are implemented and others can easily be added. The image below shows a selection of them.

Example output

The images below show some example output from the program obtained when fitting simulated filterbank data.