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Articles 91 - 93 of 93

Full-Text Articles in Cosmology, Relativity, and Gravity

Shock Study In Fully Relativistic Isothermal Flows. Ii, Ruixin Yang, Menas Kafatos Jan 1995

Shock Study In Fully Relativistic Isothermal Flows. Ii, Ruixin Yang, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

The isothermal shocks and their stabilities in fully relativistic accretion wedge flows onto black holes are studied. The jump condition across the shock is modified by the relativistic effects when the sound speed is comparable to the speed of light. With a new kind of instability analysis, it is found that only one of the two possible shocks is stable. The results are applied to the QPO behavior in galactic black hole candidates such as Cygnus X-1.


Implications Of Gamma-Ray Transparency Constraints In Blazars: Minimum Distances And Gamma-Ray Collimation, P. A. Becker, Menas Kafatos Jan 1995

Implications Of Gamma-Ray Transparency Constraints In Blazars: Minimum Distances And Gamma-Ray Collimation, P. A. Becker, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

We develop a general expression for the γ-γ absorption coefficient, αγγ, for γ-rays propagating in an arbitrary direction at an arbitrary point in space above an X-ray-emitting accretion disk. The X-ray intensity is assumed to vary as a power law in energy and radius between the outer disk radius, R0 , and the inner radius, Rm., which is the radius of marginal stability for a Schwarzschild black hole. We use our result for αγγ to calculate the γ-γ optical depth, Tγγ, for γ-rays created at height z and propagating at angle Φ relative to the disk axis, and we show …


Monte Carlo Simulation Of The Scintillating Optical Fiber Calorimeter (Sofcal), Zibin Yang, Russell Gillum, Donald C. Wold Jan 1994

Monte Carlo Simulation Of The Scintillating Optical Fiber Calorimeter (Sofcal), Zibin Yang, Russell Gillum, Donald C. Wold

Journal of the Arkansas Academy of Science

A scintillating optical fiber calorimeter (SOFCAL) is being developed by NASA/Marshall Space Flight Center for use in balloon-borne emulsion chambers to study the spectrum of high-energy cosmic rays and gamma rays. SOFCAL will not saturate for long exposures, and the detector will be helpful for the study of primary cosmic-ray nuclei energies from 100 GeV to 1,000 TeV. For a given incident particle and energy, computer simulations of electromagnetic cascades allow computation of energy deposited in different regions of the calorimeter. For these initial simulations, a 5-cm x 5-cm x 7-cm calorimeter was used. Each subsection contained a 0.4-cm thick …