JetFit

Gamma-ray Burst Afterglow Light Curve Fitting Tool.

The JetFit package fits GRB afterglow light curves for arbitrary viewing angle using the "boosted fireball" structured jet model Duffell & MacFadyen (2013) for the jet dynamics (for details see Wu & MacFadyen (2018). The light curve computation is based on the ScaleFit package (Ryan, van Eerten, MacFadyen & Zhang (2015)). JetFit is currently in some state between alpha and beta.

Table.h5 contains the characteristic spectral functions, which are used to generate synthetic light curves. The table is almost the same as the table used in Wu & MacFadyen (2018). We are improving the table by increasing resolution, adding synchrotron absorption and wind circumburst medium. Hopefully, it will come out pretty soon.

Setup

• Clone the repo and enter it.

  git clone https://github.com/astrodyl/JetFit.git
  cd JetFit
  

• Install Python 3.8 and create a virtual environment.

  python -m venv /path/to/new/virtual/environment
  

• Activate the venv and install the dependencies.

  # Windows Users
  /path/to/new/virtual/environment/Scripts/activate
  pip install --upgrade setuptools
  pip install -r requirements.txt
  
  # Linux Users
  source /path/to/new/virtual/environment/bin/activate
  pip install -r requirements.txt

Usage

To run JetFit, simply activate your virtual environment and run python __main__.py.

Module Description

JetFit package consists of three classes: Interpolator, FluxGenerator and Fitter. FluxGenerator can be used separately.

Interpolator:

• _load_table: load characteristic spectral function table.
• _set_scale: set scales for the table. By default, f_peak and tau are in log scale.
• _get_interpolator: use scipy.interpolate.RegularGridInterpolator as interpolator.
• get_value: get values for characteristic spectral function at specific position (tau, Eta0, GammaB, theta_obs).

FluxGenerator:

• get_taus: rescale the observational time in second.
• get_transformed_value: get the transformed values f_peak, nu_c and nu_m (Ryan et al. 2015).
• get_spectral: calculate synthetic light curves f_nu (Sari et al. 1998).
• get_integrated_flux: calculate synthetic integrated light curves.

ScaleFitClass:

• _set_fit_parameter: set up ScaleFit, e.g. parameter scales and parameter bounds.
• load_data: load observational data.
• set_sampler: initialize sampler from emcee package.
• run: run sampling procedure and save results to local drive.