118305517
Causal Structures of Dynamic Black Holes
Dynamic space‐times, especially those manifesting horizons, provide useful laboratories for examining how macroscopic quantum behaviors consistently co‐generate gravitational phenomena. For this reason, the behaviors and large‐scale causal structures of spatially coherent dynamic black holes will be explored in this presentation. Geodesic motions on an evaporating black hole will also be presented. Research recently completed with Beth Brown, including her final Penrose diagram for an accreting black hole, will be presented.
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.
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.
17737699
Construction of a Penrose diagram for an accreting black hole
A Penrose diagram is constructed for a spatially coherent black hole that accretes at stepwise steady rates as measured by a distant observer from an initial state described by a metric of Minkowski form. Coordinate lines are computationally derived, and radial lightlike trajectories verify the viability of the diagram. Coordinate dependences of significant features, such as the horizon and radial mass scale, are clearly demonstrated on the diagram. The onset of a singularity at the origin is shown to open a new region in space time that contains the interior of the black hole.
17355301
The Effect of Environment on the X-Ray Emission from Early-Type Galaxies
In order to further our understanding of the phenomena of X-ray emission from early-type galaxies, we obtained an optically flux-limited sample of 34 elliptical and S0 galaxies, observed with high and low angular resolution detectors on ROSAT. Our previous analysis of this sample suggested that the most X-ray-luminous galaxies were in rich environments. Here we investigate environmental influences quantitatively and find a positive correlation between LX/LB and the local galaxy density. Since the local galaxy density is usually related to the density of hot intergalactic gas, we suggest that this correlation occurs because the X-ray luminosity is enhanced, either through accretion of the intergalactic gas or because the ambient medium stifles galactic winds. When the ambient medium is unimportant, partial or global galactic winds can occur, reducing LX/LB. These effects lead to the large observed dispersion in LX at fixed LB. We discuss details of the data processing not previously presented, and examine the dependence of LX on the choice of outer source radius and background location. We also compare the temperature deduced for these galaxies from different analyses of ROSAT and ASCA data. The ASCA and ROSAT temperatures are found to be similar, provided that the same metallicities and Galactic absorption columns are used.
121557193
Shape coexistence on the boundary of the “island of inversion”: Exotic beam spectroscopy of 34Al
ower The ‘‘island of inversion,’’ a group of deformed neutron rich nuclei at and near the neutron magic number N520, poses an important test of our understanding of the phen enon of shape coexistence in atomic nuclei. While sh coexistence occurs throughout the table of isotopes @1#, the island of inversion seems to be unique in that the ‘‘intrude configuration that is formed by promoting two neutro across theN520 shell gap becomes the ground state. build an understanding of this phenomenon, we must only measure nuclear structure properties of nuclei wit the island~for example, see@2–4#! but also at and near th boundary of the island of inversion @3,6#. In the boundary nuclei, we expect that the intruder configurations occur low excitation energies with normal configurations domin ing the ground states. In this Brief Report, we report the result of a measu ment of the boundary nucleus Al using the technique of intermediate-energy Coulomb excitation @7#. With Z513 andN521, this aluminum isotope is located between Si, in which the ground state appears to be dominated by nor configurations@5#, and the island of inversion isotope Mg. We observe ag ray in Al at 65769 keV. A comparison of this result with calculations in the literature @8,9# suggests that this g ray connects an intruder state with the norm deformed ground state. The experiment was performed at the National Superc ducting Cyclotron Laboratory. The primary beam of 8 MeV/nucleon Ca was produced with the laboratory K1200 cyclotron. The secondary beam of 68.1 MeV/nucle Al was made via fragmentation of the primary beam in Be production target of thickness 376 mg/cm 2 located at the midacceptance target position of the A1200 fragm separator@10#. A 702 mg/cm Au foil was used as the secondary ta get. The secondary beam slowed significantly in this tar
30680751
Nuclear-Structure Effects on Parity Nonconservation in Light Nuclei
The nucleon-nucleon parity-nonconserving potentials given by Desplangues, Donoghue, and Holstein (DDH) are used to calculate matrix elements between states of opposite parity in /sup 10/B, /sup 16/O, /sup 18/F, /sup 19/F, /sup 20/Ne, and /sup 21/Ne. The sensitivity of the parity-nonconserving matrix elements to various approximations in the microscopic shell-model wave functions is investigated. The final results using the DDH estimates for the weak meson-nucleon coupling constants based on the Weinberg-Salam theory are several times larger than experiment.