18973653
Construction of a Penrose diagram for a spatially coherent evaporating black hole
A Penrose diagram is constructed for an example black hole that evaporates at a steady rate as measured by a distant observer, until the mass vanishes, yielding a final state Minkowski spacetime. Coordinate dependences of significant features, such as the horizon and coordinate anomalies, are clearly demonstrated on the diagram. The large-scale causal structure of the spacetime is briefly discussed.
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.
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.
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.
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.
7493892
Probing shell structure and shape changes in neutron-rich sulfur isotopes through transient-field g-factor measurements on fast radioactive beams of 38S and 40S.
The shell structure underlying shape changes in neutron-rich nuclei near N = 28 has been investigated by a novel application of the transient-field technique to measure the first-excited-state g factors in 38S and 40S produced as fast radioactive beams. There is a fine balance between proton and neutron contributions to the magnetic moments in both nuclei. The g factor of deformed 40S does not resemble that of a conventional collective nucleus because spin contributions are more important than usual.
125030066
Thermonuclear reaction rate of Ni-56 (p, gamma) Cu-57 and Cu-57 (p, gamma) Zn-58
35659315
Neutrino-pair emission from hot nuclei during stellar collapse
Author(s): Misch, G Wendell; Brown, B Alex; Fuller, George M | Abstract: We present shell-model calculations showing that residual interaction-induced configuration mixing enhances the rate of neutral current de-excitation of thermally excited nuclei into neutrino-antineutrino pairs. Though our calculations reinforce the conclusions of previous studies that this process is the dominant source of neutrino pairs near the onset of neutrino trapping during stellar collapse, our shell-model result has the effect of increasing the energy of these pairs, possibly altering their role in entropy transport in supernovae. © 2013 American Physical Society.
123028514
Low-lying levels in Cr59: Inadequacy of the fp model space and onset of deformation
The low-lying levels in $^{59}\mathrm{Cr}$ have been studied with the $^{13}\mathrm{C}(^{48}\mathrm{Ca},2p)$ reaction at a beam energy of $130\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$. Data on $^{59}\mathrm{Mn}$, produced via the $pn$-evaporation channel, have set limits on the spin of the ground state in $^{59}\mathrm{Cr}$ and enabled some spin-parity assignments of excited states to be made. The structure obtained in this study is clearly inconsistent with results of shell-model calculations within the full $fp$ shell and requires inclusion of the $\ensuremath{\nu}{g}_{9∕2}$ orbital. The sequence of states is understood within Nilsson model calculations assuming a moderate oblate ground-state deformation.
122404230
Collectivity of Exotic Heavy Fe Isotopes
The properties of exotic neutron-rich nuclei between the proton shell closures Z = 20 and Z = 28 are of particular interest for the understanding of the shell structure for large neutron excess. Effects related to the energy gap between the neutron fp and 1g9/2 shells lead to a strong variation of collectivity for nuclei around N = 40. Whereas 68Ni was found to have doubly magic properties, this was not observed in neighbouring nuclei. Recent shell model calculations for the neutron rich iron isotopes clearly reveal the difficulty to describe nuclei in this mass region and resulted in large deviations of the predicted collectivity depending on the valence space. However, no experimental data on the transition strength existed for the very exotic nucleus 66Fe at N = 40. Here we present the newest results on absolute transition strengths of the lowest excited states in 62,64,66Fe measured model independently using the recoil distance Doppler-shift (RDDS) method. The experiments were performed at NSCL at Michigan State University with the Cologne/NSCL plunger device using Coulomb excitation in inverse kinematics at energies of 80 MeV/u. Our results yield a much higher collectivity for 64,66Fe than expected and allow tests of new calculations.