Scattering fits of time domain radio signals (Fast Radio Bursts or pulsars).
Project description
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): https://ascl.net/code/v/3366
Installation
The easiest and recommended way to install the software is through pip
from the central PyPI index by running:
pip3 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:
pip3 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 --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.
Usage
$ scatfit-fitfrb -h
usage: scatfit-fitfrb [-h] [--compare] [--binburst bin] [--fscrunch factor] [--tscrunch factor] [--fast] [--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)
--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])
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.
FAQ
What scattering model should I use?
The answer depends on the data set at hand. However, the following advice is generally accurate. For frequency (sub-)bands of small fractional bandwidth or at high frequencies, i.e. where the narrow bandwidth approximation roughly holds, it is OK to use the default scattered_isotropic_analytic
model. At low frequencies (< 1 GHz) or for wide (sub-)bands, use the much more complex and, therefore, slower scattered_isotropic_bandintegrated
model.
Why do I get the following warning: Could not import Cython pulse model implementations. Falling back to the Python versions.
?
This could happen if you run scatfit
from its software repository git checkout, where the current working directory takes import preference. Install the software as above and run it as $ scatfit-fitfrb
in a different path.
What data formats are supported?
scatfit
supports loading data from SIGPROC
filterbank files. Alternative loaders can be implemented relatively easily.
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