Evolution of the Dark Matter Distribution at the Galactic Center

Annihilation radiation from neutralino dark matter at the Galactic center (GC) would be greatly enhanced if the dark matter were strongly clustered around the supermassive black hole (SBH). The existence of a dark-matter "spike" is made plausible by the observed, steeply-rising stellar density near the GC SBH. Here the time-dependent equations describing gravitational interaction of the dark matter particles with the stars are solved. Scattering of dark matter particles by stars would substantially lower the dark matter density near the GC SBH over 10^10 yr, due both to kinetic heating, and to capture of dark matter particles by the SBH. This result suggests that enhancements in the dark matter density around a SBH would be modest whether or not the host galaxy had experienced the scouring effects of a binary SBH.Comment: 5 pages, 3 figures. Submitted to Physical Review Letter

An integrated study of earth resources in the State of California based on ERTS-1 and supporting aircraft data

There are no author-identified significant results in this report

A multispectral photographic experiment based on a statistical analysis of spectrometric data Final report

Multispectral photographic experiment based on statistical analysis of spectrometric data - spectral reflectance for terrain, optimum film- filter combinations, and terrain tone signature

A Coordinated X-ray and Optical Campaign of the Nearby Massive Binary δ\delta Orionis Aa: II. X-ray Variability

We present time-resolved and phase-resolved variability studies of an extensive X-ray high-resolution spectral dataset of the $\delta$ Orionis Aa binary system. The four observations, obtained with Chandra ACIS HETGS, have a total exposure time of ~479 ks and provide nearly complete binary phase coverage. Variability of the total X-ray flux in the range 5-25 $\AA$ is confirmed, with maximum amplitude of about +/-15% within a single ~125 ks observation. Periods of 4.76d and 2.04d are found in the total X-ray flux, as well as an apparent overall increase in flux level throughout the 9-day observational campaign. Using 40 ks contiguous spectra derived from the original observations, we investigate variability of emission line parameters and ratios. Several emission lines are shown to be variable, including S XV, Si XIII, and Ne IX. For the first time, variations of the X-ray emission line widths as a function of the binary phase are found in a binary system, with the smallest widths at phase=0.0 when the secondary $\delta$ Orionis Aa2 is at inferior conjunction. Using 3D hydrodynamic modeling of the interacting winds, we relate the emission line width variability to the presence of a wind cavity created by a wind-wind collision, which is effectively void of embedded wind shocks and is carved out of the X-ray-producing primary wind, thus producing phase-locked X-ray variability.Comment: 36 pages, 14 Tables, 19 Figures, accepted by ApJ, one of 4 related papers to be published togethe

Freshness and Reactivity Analysis in Globally Asynchronous Locally Time-Triggered Systems

International audienceCritical embedded systems are often designed as a set of real-time tasks, running on shared computing modules, and communicating through networks. Because of their critical nature, such systems have to meet timing properties. To help the designers to prove the correctness of their system, the real-time systems community has developed numerous approaches for analyzing the worst case times either on the processors (e.g. worst case execution time of a task) or on the networks (e.g. worst case traversal time of a message). However, there is a growing need to consider the complete system and to be able to determine end-to-end properties. Such properties apply to a functional chain which describes the behavior of a sequence of functions, not necessarily hosted on a shared module, from an input until the production of an output. This paper explores two end-to-end properties: freshness and reactivity, and presents an analysis method based on Mixed Integer Linear Programming (MILP). This work is supported by the French National Research Agency within the Satrimmap project

A Coordinated X-ray and Optical Campaign on the Nearest Massive Eclipsing Binary, Delta Ori Aa: I. Overview of the X-ray Spectrum

We present an overview of four phase-constrained Chandra HETGS X-ray observations of Delta Ori A. Delta Ori A is actually a triple system which includes the nearest massive eclipsing spectroscopic binary, Delta Ori Aa, the only such object which can be observed with little phase-smearing with the Chandra gratings. Since the fainter star, Delta Ori Aa2, has a much lower X-ray luminosity than the brighter primary, Delta Ori A provides a unique system with which to test the spatial distribution of the X-ray emitting gas around Delta Ori Aa1 via occultation by the photosphere of and wind cavity around the X-ray dark secondary. Here we discuss the X-ray spectrum and X-ray line profiles for the combined observation, having an exposure time of nearly 500 ksec and covering nearly the entire binary orbit. Companion papers discuss the X-ray variability seen in the Chandra spectra, present new space-based photometry and ground-based radial velocities simultaneous with the X-ray data to better constrain the system parameters, and model the effects of X-rays on the optical and UV spectrum. We find that the X-ray emission is dominated by embedded wind shock emission from star Aa1, with little contribution from the tertiary star Ab or the shocked gas produced by the collision of the wind of Aa1 against the surface of Aa2. We find a similar temperature distribution to previous X-ray spectrum analyses. We also show that the line half-widths are about $0.3-0.5\times$ the terminal velocity of the wind of star Aa1. We find a strong anti-correlation between line widths and the line excitation energy, which suggests that longer-wavelength, lower-temperature lines form farther out in the wind. Our analysis also indicates that the ratio of the intensities of the strong and weak lines of \ion{Fe}{17} and \ion{Ne}{10} are inconsistent with model predictions, which may be an effect of resonance scatteringComment: accepted by ApJ; revised according to ApJ proo

The Isophotal Structure of Early-Type Galaxies in the SDSS: Dependence on AGN Activity and Environment

We study the dependence of the isophotal shape of early-type galaxies on their absolute B-band magnitude, their dynamical mass, and their nuclear activity and environment, using an unprecedented large sample of 847 early-type galaxies identified in the SDSS by Hao et al (2006). We find that the fraction of disky galaxies smoothly decreases with increasing luminosity. The large sample allows us to describe these trends accurately with tight linear relations that are statistically robust against the uncertainty in the isophotal shape measurements. There is also a host of significant correlations between the disky fraction and indicators of nuclear activity (both in the optical and in the radio) and environment (soft X-rays, group mass, group hierarchy). Our analysis shows however that these correlations can be accurately matched by assuming that the disky fraction depends only on galaxy luminosity or mass. We therefore conclude that neither the level of activity, nor group mass or group hierarchy help in better predicting the isophotal shape of early-type galaxies.Comment: 31 pages, 10 figures, accepted for publication in Ap

Sign of inverse spin Hall voltages generated by ferromagnetic resonance and temperature gradients in yttrium iron garnet|platinum bilayers

We carried out a concerted effort to determine the absolute sign of the inverse spin Hall effect voltage generated by spin currents injected into a normal metal. We focus on yttrium iron garnet (YIG)|platinum bilayers at room temperature, generating spin currents by microwaves and temperature gradients. We find consistent results for different samples and measurement setups that agree with theory. We suggest a right-hand-rule to define a positive spin Hall angle corresponding to with the voltage expected for the simple case of scattering of free electrons from repulsive Coulomb charges.Comment: incorporated additions from the published versio