118606402
Radial Photon Trajectories Near an Evaporating Black Hole
The radial motion of photons emitted near the horizon of a black hole that evaporates at a steady rate is examined. The space-time of the black hole is generated using non-orthogonal coordinates. It is shown that some photons that are initially drawn towards the singularity can escape falling into the horizon. The behaviors of various outgoing and ingoing photons are clearly demonstrated through the use of a Penrose diagram.
119084367
Emission mechanisms in X-ray-faint galaxies
Hot gas dominates the emission in X-ray-luminous early-type galaxies, but in relatively X-ray-faint systems, integrated X-ray emission from discrete stellar-like sources is thought to be considerable, although the amount of the contribution is controversial. To help resolve this issue, we examine the radial X-ray surface brightness distribution of 17 X-ray-faint galaxies observed with the ROSAT HRI and PSPC. We assume that the stellar contribution follows a de Vaucouleurs law while the hot gas component follows a King β model. For some galaxies, both models fit equally well, but for a number of systems, a dual component model yields the best fit, from which upper bounds are placed on the stellar contribution. Best-fit values for the stellar contribution are inconsistent with (lower than) that suggested by Fabbiano, Gioia, & Trinchieri and estimated from the bulge of M31 but are consistent with the Forman, Jones, & Tucker estimate of the stellar fraction in X-ray-faint elliptical and S0 galaxies. Our results indicate an upper limit to discrete sources of LX/LB = 1.6 × 1029 ergs s-1 L.
11457012
X-Ray Emission from Early-Type Galaxies: A Complete Sample Observed by ROSAT
To test the cooling flow model of early-type galaxies, we obtained a complete magnitude-limited sample of 34 early-type galaxies, observed with the PSPC and the HRI on ROSAT. The X-ray-to-optical distribution of galaxies implies a lower envelope, which is consistent with the stellar emission inferred from Cen A. When this stellar component is removed, the gaseous emission is related to the optical luminosity by LX ∝ LBm, where m = 3.0-3.5, which is significantly steeper than the standard theory (m = 1.7). The dispersion about the correlation is large, with a full range of 30-100 in LX for fixed LB. The X-ray temperature is related to the velocity dispersion temperature as TX ∝ Tσn, where n=1.43±0.21, although for several galaxies, TX is about twice Tσ. The excessively hot galaxies are generally the most luminous and are associated with the richest environments. We suggest a model whereby the environment influences the X-ray behavior of these galaxies: early-type galaxies attempt to drive partial or total galactic winds, which can be stifled by the pressure of their environment. Stifled winds should lead to hotter and higher luminosity systems, which would occur most commonly in the richest environments, as observed.
43538683
Nuclear charge densities with the Skyrme Hartree-Fock method
Charge-density distributions and the associated nuclear radii are calculated with the Hartree-Fock method for comparison with available data from electron scattering. Two forms of Skyrme interactions are used for the calculations. As a further refinement the single-particle occupancies are constrained to values obtained from shell-model calculations. A significant improvement in the agreement is obtained if shell-model occupancies are used.
125030066
Thermonuclear reaction rate of Ni-56 (p, gamma) Cu-57 and Cu-57 (p, gamma) Zn-58