We consider the long term fate and evolution of cold degenerate stars under the action of gravity alone. Although such stars cannot emit radiation through the Hawking mechanism, the wave function of the star will contain a small admixture of black hole states. These black hole states will emit radiation and hence the star can lose its mass energy in the long term. We discuss the allowed range o...

Massive stars in their final stages of collapse radiate most of their binding energy in the form of MeV neutrinos. The recoil atoms that they produce in elastic scattering off nuclei in organic tissue create radiation damage which is highly effective in the production of irreparable DNA harm, leading to cellular mutation, neoplasia, and oncogenesis. Using a conventional model of the galaxy and...

Protons accelerated in the internal shocks of a long duration gamma ray burst can escape the fireball as cosmic rays by converting to neutrons. Hadronic interactions of these neutrons inside a stellar wind bubble created by the progenitor star will produce TeV gamma rays via neutral meson decay and synchrotron radiation by charged pion-decay electrons in the wind magnetic field. Such gamma rays...

We discuss the space-and-time-dependent Monte Carlo code we have developed to simulate the relativistic radiation output from compact astrophysical objects, coupled to a Fokker-Planck code to determine the self-consistent lepton populations. We highlight some major recent results obtained with this code,. They are relevant to the emission from a magnetized neutron star accretion shell near the ...

A torus around a stellar mass Kerr black hole can emit about 10% of the spin-energy of the black hole in gravitational radiation, potentially associated with a gamma-ray burst. Wide tori may develop buckling modes by the Papaloizou-Pringle instability and gravitational radiation-reaction forces in the Burke-Thorne approximation. Gravitational wave experiments may discover these emissions in a f...

The stellar winds of massive stars show large changes in mass-loss rates and terminal velocities during their evolution from O-star through the Luminous Blue Variable phase to the Wolf-Rayet phase. The luminosity remains approximately unchanged during these phases. These large changes in wind properties are explained in the context of the radiation driven wind theory, of which we consider four ...

the rotation curves of a sample of 46 low- and high-surface brightness galaxies are considered in the context of milgrom's modi_ed dynamics (mond) to test a new interpolating function proposed by zhao et al. (2010) [1] and compare with the results of simple interpolating function. the predicted rotation curves are calculated from the total baryonic matter based on the b-band surface photometry,...

Medium-resolution spectra from 3650 Å to 10,000 Å are presented for 96 giant H II regions distributed in 20 spiral galaxies. In order to interpret the data, we have calculated two separate grids of photoionization models, adopting single-star atmospheres (Kurucz) and star clusters synthesized with different Initial Mass Functions (IMFs) as ionizing sources. Additional models were computed with ...

Recent High Energy Stereoscopic System (HESS) observations show that microquasars in highmass systems are sources of very high energy γ-rays. A leptonic jet model for microquasar γ-ray emission is developed. Using the head-on approximation for the Compton cross section and taking into account angular effects from the star’s orbital motion, we derive expressions to calculate the spectrum of γ ra...

we have studied the effect of hypothetical cosmions on the core stability of main sequence stars (of populations i and ii). cosmions, with a mass of 4-10 gev/c2 and a scattering cross section with nucleons of approximately 10-36 cm2 could prevail in transporting heat in the stellar cores. raby [17] showed the existence of a local thermal instability caused by the presence of cosmions in the sol...