We numerically analyze the evolution of a long-duration gamma-ray burst jet as it leaves the progenitor star and propagates to the photospheric radius, where radiation can be released. We find that the interaction of the relativistic material with the progenitor star has influences well beyond the stellar surface. Tangential collimation shocks are observed throughout the jet evolution, out to a...

Local-box hydrodynamical model atmospheres provide statistical information about the spatial dependence, as well as temporal evolution, of a star’s emergent radiation field. Here, we consider late-type stellar atmospheres for which temporal changes of the radiative output are primarily related to convective (granular) surface flows. We derived relations for evaluating the granulation-induced, d...

We propose a model of starburst–driven galactic outflows whose dynamics depends on both radiation and thermal pressure. Standard models of thermal pressure–driven winds fail to explain some key observations of outflows at low and high redshift galaxies. We discuss a scenario in which radiation pressure from massive stars in a stellar population drive a shell of gas and dust. Subsequent supernov...

We derive an analytic expression for the intensity of resonance-line radiation “trapped” in a semi-infinite medium. Given a source function and destruction probability per scattering, the radiation pressure due to trapped photons can be calculated by numerically integrating over analytic functions. We apply this formalism to a plane-parallel model stellar atmosphere to calculate the radiation p...

We study the hydrodynamic evolution of protostellar disks under the influence of a central source of ionizing radiation and its stellar wind. Here we examine the effects of an important contribution to the diffuse radiation field – the scattering of hydrogen-ionizing photons on dust grains (dust scattering). We present and discuss the resulting changes in the evolution of the system under a var...

Continuous wave gravitational radiation from isolated rotating neutron stars is discussed. The general waveform and orders of magnitude for the amplitude are presented for various known pulsars. The specific case of gravitational radiation resulting from the distortion induced by the stellar magnetic field is presented. Finally some preliminary results about the signal from the whole population...

The dynamics and thermal structure of the surface layers of stars with outer convection zones can be studied in some detail by means of numerical simulations of time-dependent compressible convection. In an effort to investigate the properties of “stellar granulation” as a function of spectral type, we have carried out elaborate 2-dimensional radiation hydrodynamics calculations of surface conv...

This paper outlines astrophysical issues related to the long-term fate of the universe. The authors consider the evolution of planets, stars, stellar populations, galaxies, and the universe itself over time scales that greatly exceed the current age of the universe. Their discussion starts with new stellar evolution calculations which follow the future evolution of the low-mass (M-type) stars t...