A Python 3 module to calculate GRB afterglow light curves and spectra. Details of the methods can be found in Ryan et al 2019. Builds on van Eerten & MacFadyen 2010 and van Eerten 2018. This code is under active development.
Documentation available at https://afterglowpy.readthedocs.io/
If you use this code in a publication, please refer to the package by name and cite "Ryan, G., van Eerten, H., Piro, L. and Troja, E., 2019, arXiv:1910.11691" arXiv link.
afterglowpy computes synchrotron emission from the forward shock of a relativistic blast wave. It includes:
- Fully trans-relativistic shock evolution through a constant density medium.
- On-the-fly integration over the equal-observer-time slices of the shock surface.
- Approximate prescription for jet spreading.
- Arbitrary viewing angles.
- Angularly structured jets, ie. E(θ)
- Spherical velocity-stratified outflows, ie. E(u)
- Counter-jet emission.
It has limited support (these should be considered experimental) for:
- Initial energy injection
- Inverse comption spectra
- Spatially-resolved intensity maps
- Early coasting phase
It does not include (yet):
- External wind medium, ie. n ∝ r-2
- Synchrotron self-absorbtion
- Reverse shock emission
afterglowpy has been calibrated to the BoxFit code (van Eerten, van der Horst, & Macfadyen 2011, available at the Afterglow Library) and produces similar light curves for top hat jets (within 50% when same parameters are used) both on- and off-axis. Its jet models by default do not include an initial coasting phase, which may effect predictions for early observations.
afterglowpy is available via pip
:
$ pip install afterglowpy
If you are working on a local copy of this repo and would like to install from source, you can the run the following from the top level directory of the project.
$ pip install -e .
This interface will be updated to be more sensible in the VERY near future
In your python code, import the library with import afterglowpy as grb
.
The main function of interest isgrb.fluxDensity(t, nu, jetType, specType, *pars, **kwargs)
. See tests/plotLC.py
for a simple example.
jetType
can be -1 (top hat), 0 (Gaussian), 1 (Power Law w/ core), 2 (Gaussian w/ core), 3 (Cocoon), or 4 (Smooth Power Law).
specType
can be 0 (global cooling time, no inverse compton) or 1 (global cooling time, inverse compton).
For jet-like afterglows (jetTypes
-2, -1, 0, 1, 2, and 4) pars
has 14 positional arguments:
0 thetaV
viewing angle in radians1 E0
on-axis isotropic equivalent energy in erg2 thetaC
half-width of the jet core in radians (jetType specific)3 thetaW
"wing" truncation angle of the jet, in radians4 b
power for power-law structure, θ-b5 L0
Fiducial luminosity for energy injection, in erg/s, typically 0.6 q
Temporal power-law index for energy injection, typically 0.7 ts
Fiducial time-scale for energy injection, in seconds, typically 0.8 n0
Number density of ISM, in cm-39 p
Electron distribution power-law index (p>2)10 epsilon_e
Thermal energy fraction in electrons11 epsilon_B
Thermal energy fraction in magnetic field12 xi_N
Fraction of electrons that get accelerated13 d_L
Luminosity distance in cm
For cocoon-like afterglows (jetType
3) pars
has 14 positional arguments:
0 umax
Initial maximum outflow 4-velocity1 umin
Minium outflow 4-velocity2 Ei
Fiducial energy in velocity distribution, E(>u) = Ei u-k.3 k
Power-law index of energy velocity distribution4 Mej
Mass of material at `umax' in solar masses5 L0
Fiducial luminosity for energy injection, in erg/s, typically 0.6 q
Temporal power-law index for energy injection, typically 0.7 ts
Fiducial time-scale for energy injection, in seconds, typically 0.8 n0
Number density of ISM, in cm-39 p
Electron distribution power-law index (p>2)10 epsilon_e
Thermal energy fraction in electrons11 epsilon_B
Thermal energy fraction in magnetic field12 xi_N
Fraction of electrons that get accelerated13 d_L
Luminosity distance in cm
Keyword arguments are:
z
redshift (defaults to 0)tRes
time resolution of shock-evolution scheme, number of sample points per decade in timelatRes
latitudinal resolution for structured jets, number of shells perthetaC
rtol
target relative tolerance of flux integrationspread
boolean (defaults to True), whether to allow the jet to spread.