Two-phase Comptonization model of soft thermal
seed photons for GRB prompt emission.
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 two-phase model: up to the peak energy Ep
of the EF(E) spectrum soft thermal blackbody-like photons are
comptonized by a subrelativistic bulk outflow of thermal electrons,
while the high-energy tail is obtained by a further convolution
of the formerly comptonized spectrum with a Green's
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 = kTs, 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 = kTe, electron temperature of the
subrelativistic outflow (keV)
par4 = τ, radial optical depth of the subrelativistic
par5 = β, bulk outflow velocity of the thermal electrons
par6 = fbflag, if set = 0 only the first-order
bulk Comptonization term is considered, if set =1 also the second-order term 1+β2/3Θ is computed, where Θ=kTe/mec2
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 = R29
/D2Mpc, where R9 is the apparent
blackbody radius in units of 109 cm and DMpc is
the sorce distance in Mpc
To install as an XSPEC local model download the source code and model
Lab. for High Energy Astrophysics, NASA/Goddard Space Flight Center
Xspec Home Page
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