A CODE FOR OPTICALLY THICK AND HOT PHOTOIONISED MEDIA —
TITAN
TITAN is a photoionization code written in Fortran77, which calculates the radiative transfer of electromagnetic radiation through the optically thick medium consisting heavy elements.
It includes all atomic processes: absorption, excitation, de-excitation of atoms and ions, ionization, recombination, free-free emission and Compton scattering. The radiative equilibrium is justified by computing heating and cooling of the gas. TITAN solves the energy dependent radiation transfer in continuum and lines. As a result, transmission, reflection and diffusion part of the intensity field is computed in order to obtain the spectra reemitted by the medium in various directions. Numerical method used to solve radiative transfer is Accelerated Lambda Iteration algorithm.
UNIQUE MODEL ATMOSPHERE OF HOT NEUTRON STAR AND ACCRETION DISKS —
ATM 24
ATM24 is a radiative transfer code written in Fortran 77 (partially upgraded to newer version), which calculates the radiative transfer in the plane-parallel geometry, through the hot neutron star or accretion disk atmosphere.
It takes into account the effect of Compton scattering of photons on free electrons, also on those moving with relativistic velocities. The initial photon energy can approach the electron rest mass, and the exact Compton redistribution functions are calculated. The ionization balance is computed with assumption of Local Thermal Equilibrium (LTE), while the gas has to be in hydrostatic and thermal balance with radiation. As a result, an outgoing angle dependent Comptonized intensity spectrum is obtained from fully thermalized gas. The radiative transfer is solved with Feautrier's method.