Twophase Comptonization model of soft thermal
seed photons for GRB prompt emission.
NOTE: This model is now in the Xspec release and this page is superceded by the Xspec manual
This GRBCOMP model has been proposed by Titarchuk et al. (2012, ApJ, 752, 116) as a possible scenario for the
spectral emission of the prompt phase of Gamma Ray Bursts.
It is essentially a twophase model: up to the peak energy E_{p}
of the EF(E) spectrum soft thermal blackbodylike photons are
comptonized by a subrelativistic bulk outflow of thermal electrons,
while the highenergy tail is obtained by a further convolution
of the formerly comptonized spectrum with a Green's
function.
An example of the application of the model to a sample of GRBs can be found in Frontera et al. (2013, ApJ, 779, 175).
The model parameters are the following:
par1 = kT_{s}, temperature of the seed
blackbody spectrum (keV)
par2 = γ, when it is set = 3 the seed soft spectrum is a blackbody, otherwise it approximates a modified blackbody
par3 = kT_{e}, electron temperature of the
subrelativistic outflow (keV)
par4 = τ, radial optical depth of the subrelativistic
outflow
par5 = β, bulk outflow velocity of the thermal electrons
par6 = fbflag, if set = 0 only the firstorder
bulk Comptonization term is considered, if set =1 also the secondorder term 1+β^{2}/3Θ is computed, where Θ=kT_{e}/m_{e}c^{2}
par7 = log(A), geometrical covering factor which determines the relative weigths of the seed and comptonized spectra to the total flux
par8 = z, redshift
par9 = αboost, energy index of the Green's function with which the formerly comptonization spectrum is convolved
norm = R^{2}_{9}
/D^{2}_{Mpc}, where R_{9} is the apparent
blackbody radius in units of 10^{9} cm and D_{Mpc }is
the sorce distance in Mpc
To install as an XSPEC local model download the source code and model
description file.
Keith Arnaud,
Lab. for High Energy Astrophysics, NASA/Goddard Space Flight Center
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Last modified: Tuesday, 14Feb2023 16:41:50 EST
