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.
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.
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.
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.
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.
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.
2929726
Discerning the neutron density distribution of 208 Pb from nucleon elastic scattering
In this paper we seek a measure of the neutron density of 208Pb from analyses of intermediate-energy nucleon elastic scattering. The pertinent model for such analyses is based on coordinate space nonlocal optical potentials obtained from model nuclear ground-state densities. Those potentials give predictions of integral observables and of angular distributions, which show sensitivity to the neutron density. When compared with experiment, and correlated with analyses of electron scattering data, the results suggest that 208Pb has a neutron skin thickness of ∼0.17 fm.
125701710
Nuclear structure of the closed subshell nucleus Zr-90 studied with the (n, n-prime gamma) reaction
119489377
Indirect Techniques in Nuclear Astrophysics. Asymptotic Normalization Coefficient and Trojan Horse
We address two important indirect techniques, the asymptotic normalization coefficient (ANC) and the Trojan Horse (TH) methods. We discuss the application of the ANC technique to determine the astrophysical factor for the 13 C( α , n ) 16 O reaction which is one of the neutron generators for the s processes in AGB stars. The TH method is a unique indirect technique allowing one to measure astrophysical S factors for rearrangement reactions down to astrophysically relevant energies. We derive equations connecting the cross sections for the binary direct and resonant reactions determined from the indirect TH reactions to direct cross sections measurements.
39647933
Intermediate energy proton knockout to the "island of inversion" isotope Mg-31
The "island of the inversion" isotope 31 Mg was investigated using an intermediate energy proton knockout reaction from 32 Al at 90 MeV/nucleon at the National Superconducting Cyclotron Laboratory. A negligible cross section to the ground state supports an intruder-dominant configuration in 31 Mg. The partial cross sections to excited final states preferentially populate configurations in the 31 Mg residues which have no neutron excitations across the N = 20 shell closure. There is strong evidence that the reaction populates the 3/2+ and 5/2+ states which correspond with the neutron-hole states predicted by the shell model with the model space truncated above the sd-shell.
118350082
High-precision (p, t) reaction measurement to determine Ne-18 (alpha, p) Na-21 reaction rates
x-ray bursts are identified as thermonuclear explosions in the outer atmosphere of accreting neutron stars. The thermonuclear runaway is fueled by the alpha p process that describes a sequence of (alpha,p) reactions triggered by the Ne-18(alpha,p)Na-21 breakout reaction from the hot CNO cycles. We studied the level structure of the compound nucleus Mg-22 by measuring the Mg-24(p,t)Mg-22 reaction at the Grand Raiden spectrometer at Research Center for Nuclear Physics, Osaka. A large number of alpha-unbound states was identified and precise excitation energies were determined. Based on shell model and alpha-cluster model calculations we predict the level parameters for determining the stellar reaction rate of Ne-18(alpha,p)Na-21 for a wide temperature range. x-ray burst simulations have been performed to study the impact of the reaction on the x-ray burst luminosity.