Talk detail

Participant	Aksenov, Alexey
Institution	Institute for Computer-Aided Design RAS - Vtoraya Brestskaya 19/18 - Moscow - 123056 Moscow - Russia

Session	GRB1	Accepted	Yes	Order	14	Time	18:00 - 18:15
Talk	Oral abstract	Title	Radiative transfer near the photosphere of mildly and ultrarelativistic outflows. Numerical approaches and nonthermar GRBs radiation.
Co-authors	R. Ruffini, G.V. Vereshchagin
Abstract	We study radiation transport in the pair plasma of GRB sources. We develop finite difference schemes to carry out kinetic Boltzmann equations for photons and pairs with taking into account all relevant process in a spherical symmetric case with dependences of distribution functions from radius, angles, energy and time. As an example we considered 2 cases. Mildly relativistic plasma with a final gamma factor <10 with an initial optical depth 10^7 reaches a thermal equilibrium at the expansion, photons spectra is thermal a commoving coordinates. Another case it is more interesting for GRB applications an ultra relativistic plasma, but more difficult for simulations. For such plasma we assume thermal spectra for pairs in the commoving coordinates and an adiabatic cooling, and take into account only Compton scattering in kinetic equations for photons. Using diffusion type equations acceptable near the equilibrium (Kompaneets equation without the angle coordinate) we demonstrate relativistic effect --- distribution function for photons becomes anisotropic and non-thermal in the commoving coordinates. We confirm recent results by Beloborodov obtained by Monte-Carlo simulations.

Session	SN1	Accepted	Yes	Order	10	Time		20'
Talk	Oral abstract	Title	Computations of the gravitational collapse of a stellar core with electron neutrinos and anti-neutrinos transport and the problem of SN.
Co-authors	Chechetkin V.M.
Abstract	The collapse of the iron core of a star with mass 1.4 M sun is computed. The main goal of this study is to develop a numerical method for the joint solution of the gas-dynamical equations for matter and the Boltzmann kinetic equations for the distribution functions of various types of neutrinos. The spherically symmetrical case is considered, but the dependences of the distribution functions on all the phase-space variables. When computing reaction rates, the exact quantum-mechanical expressions for the probabilities of processes are used, with integration over the entire momentum phase space. The solution yields neutrino light curves with narrow maximum with characteristic widths 10 ms. Part of the neutrino energy is absorbed in the envelope of the stellar core. This is associated with the higher mean neutrino energies in our model, which is more exact than models with neutrino thermal conductivity. This approach is of interest for the application of multi-dimensional models taking into account large-scale convection.