grbcomp: Comptonization for GRB prompt emission

This model has been proposed by Titarchuk et al. (2012) 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 E$_{\rm p}$ 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 function. An example of the application of the model to a sample of GRBs can be found in Frontera et al. (2013).

par1	kTs, temperature of the seed blackbody spectrum (keV)
par2	gamma, 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	tau, radial optical depth of the subrelativistic outflow
par5	beta, 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 $1+2\beta/3\Theta$ is computed, where $\Theta=kT_e/m_ec^2$
par7	log(A), geometrical covering factor which determines the relative weights of the seed and comptonized spectra to the total flux
par8	z, redshift
par9	a_boost, energy index of the Green's function with which the formerly comptonization spectrum is convolved
norm	$R^2_9 /D^2_{\rm Mpc}$, where $R_9$ is the apparent blackbody radius in units of $10^9$ cm and $D_{\rm Mpc}$ is the sorce distance in Mpc