We introduce the classical stellar atmosphere problem and describe in detail its numerical solution. The problem consists of the solution of the radiation transfer equations under the constraints of hydrostatic, radiative and statistical equilibrium (non-LTE). We outline the basic idea of the Accelerated Lambda Iteration (ALI) technique and statistical methods which finally allow the constructi...

Gravity is nearly a universal constant in the cusp of an NFW galaxy halo. Inside this external field an isothermal gas sphere will collapse and trigger a starburst if above a critical central pressure. Thus formed spheroidal stellar systems have Sersic-profile and satisfy the Faber-Jackson relation. The process is consistent with observed starbursts. We also recover the MBH −σ∗ relation, if the...

Internal dynamical evolution can drive stellar systems into states of high central density. For many star clusters and galactic nuclei, the time scale on which this occurs is significantly less than the age of the universe. As a result, such systems are expected to be sites of frequent interactions among stars, binary systems, and stellar remnants, making them efficient factories for the produc...

We find a new mechanism of neutron star radiation wherein thermally excited helical waves of vortices in the superfluid core of a rotating neutron star produce its radiation spectrum. We find that neutron stars with a superfluid core of bosons (bosonic stars) are powerful sources of radio waves, their radiation spectrum is not Planck’s and similar to the spectrum observed from a class of quasi-...

We study a cosmological scenario for gamma ray bursts (GRBs) where relativistic ows interact with dense radiation elds. It is shown that this scenario is plausible in very dense stellar regions which are known to exist in collapsed cores of globular clusters or dense nuclei of galaxies. It yields a correct quantitative description of the temporal behavior of GRBs. Several other properties of GR...

We use equations similar to the heat conduction equation to calulate heat transfer, radiation transfer and hydrostatical equilibrium in our stellar evolution programs. We tried various numerical schemes and found that the most convenient scheme for complicated calculations (nonlinear, multidimensional calculations) is a symmetrical semi-implicit (SSI) scheme. The (SSI) scheme is easy to code, v...

We discuss the physics of the ΩΓ– Limit, i.e. when the star is unbound as a result of both rotation and radiation pressure. We suggest that the ΩΓ– Limit is what makes the Humphreys–Davidson Limit. Stellar filiations are discussed, with an emphasis on the final stages, in particular on the final masses, their angular momentum and the chemical yields with account of rotation. A possible relation...

The characteristic mass Mc in the stellar initial mass function (IMF) is about constant for most star-forming regions. Numerical simulations consistently show a proportionality between Mc and the thermal Jeans mass MJ at the time of cloud fragmentation, but no models have explained how it can be the same in diverse conditions. Here we show that MJ depends weakly on density, temperature, metalli...

The initial conditions and relevant physics for the formation of the earliest galaxies are well specified in the concordance cosmology. Using ab initio cosmological Eulerian adaptive mesh refinement radiation hydrodynamical calculations, we discuss how very massive stars start the process of cosmological reionization. The models include non-equilibrium primordial gas chemistry and cooling proce...