Chandra HRC Localization of the Low Mass X-ray Binaries X1624-490 and X1702-429: The Infrared Counterparts

We report on the precise localization of the low mass X-ray binaries X1624-490 and X1702-429 with the Chandra HRC-I. We determine the best positions to be 16:28:02.825 -49:11:54.61 (J2000) and 17:06:15.314 -43:02:08.69 (J2000) for X1624-490 and X1702-429, respectively, with the nominal Chandra positional uncertainty of 0.6". We also obtained deep IR observations of the fields of these sources in an effort to identify the IR counterparts. A single, faint (Ks=18.3 +/- 0.1) source is visible inside the Chandra error circle of X1624-490, and we propose this source as its IR counterpart. For X1702-429, a Ks=16.5 +/- 0.07 source is visible at the edge of the Chandra error circle. The brightness of both counterpart candidates is comparable to that of other low mass X-ray binary IR counterparts when corrected for extinction and distance.Comment: 5 pages, 2 figures, accepted for publication in Ap

The 1996 Soft State Transitions of Cygnus X-1

We report continuous monitoring of Cygnus X-1 in the 1.3 to 200 keV band using ASM/RXTE and BATSE/CGRO for about 200 days from 1996 February 21 to 1996 early September. During this period Cygnus X-1 experienced a hard-to-soft and then a soft-to-hard state transition. The low-energy X-ray (1.3-12 keV) and high-energy X-ray (20-200 keV) fluxes are strongly anti-correlated during this period. During the state transitions flux variations of about a factor of 5 and 15 were seen in the 1.3-3.0 keV and 100-200 keV bands, respectively, while the average 4.8-12 keV flux remains almost unchanged. The net effect of this pivoting is that the total 1.3-200 keV luminosity remained unchanged to within about 15%. The bolometric luminosity in the soft state may be as high as 50-70% above the hard state luminosity, after color corrections for the luminosity below 1.3 keV. The blackbody component flux and temperature increase in the soft state is probably caused by a combination of the optically thick disk mass accretion rate increase and a decrease of the inner disk radius.Comment: 18 pages, 1 PostScript figure. Accepted for ApJ

A Simulation Model Articulation of the REA Ontology

This paper demonstrates how the REA enterprise ontology can be used to construct simulation models for business processes, value chains and collaboration spaces in supply chains. These models support various high-level and operational management simulation applications, e.g. the analysis of enterprise sustainability and day-to-day planning. First, the basic constructs of the REA ontology and the ExSpect modelling language for simulation are introduced. Second, collaboration space, value chain and business process models and their conceptual dependencies are shown, using the ExSpect language. Third, an exhibit demonstrates the use of value chain models in predicting the financial performance of an enterprise

New XMM-Newton analysis of three bright X-ray sources in M31 globular clusters, including a new black hole candidate

We present detailed analysis of three globular cluster X-ray sources in the XMM-Newton extended survey of M31. The X-ray counterpart to the M31 globular cluster Bo 45 (XBo 45) was observed with XMM-Newton on 2006 December 26. Its combined pn+MOS 0.3--10 keV lightcurve exhibited a r.m.s variability of ~10%, and its 0.3--7.0 keV emission spectrum was well described by an absorbed power law with photon index 1.44$\pm$0.12. Its variability and emission is characteristic of low mass X-ray binaries (LMXBs) in the low-hard state, whether the accretor is a neutron star or black hole. Such behaviour is typically observed at luminosities \la10% Eddington. However, XBo 45 exhibited this behaviour at an unabsorbed, 0.3--10 keV luminosity of 2.5$\pm0.2\times 10^{38}$ erg s$^{-1}$, or{~140%} Eddington for a 1.4 $M_{\odot}$ neutron star accreting hydrogen. Hence, we identify XBo 45 as a new candidate black hole LMXB. XBo 45 appears to have been consistently bright for ~30 years, consistent with theoretical prediction for a globular cluster black hole binary formed via tidal capture. Bo 375 was observed in the 2007, January 2 XMM-Newton observation, and has a two-component spectrum that is typical for a bright neutron star LMXB. Bo 135 was observed in the same field as Bo 45, and could contain either a black hole or neutron star.Comment: Accepted by ApJ, 16 pages, 5 figures. This version includes the final changes made at the request of the refere

Evolution of the E(1/21+)−E(3/21+)E(1/2^+_1)-E(3/2^+_1) energy spacing in odd-mass K, Cl and P isotopes for N=20−28N=20-28

The energy of the first excited state in the neutron-rich N=28 nucleus 45Cl has been established via in-beam gamma-ray spectroscopy following proton removal. This energy value completes the systematics of the E(1/2^+_1)-E(3/2^+_1) level spacing in odd-mass K, Cl and P isotopes for N=20-28. The results are discussed in the framework of shell-model calculations in the sd-fp model space. The contribution of the central, spin-orbit and tensor components is discussed from a calculation based on a proton single-hole spectrum from G-matrix and pi + rho meson exchange potentials. A composite model for the proton 0d_{3/2}-1s_{1/2} single-particle energy shift is presented.Comment: Phys. Rev. C, in pres

Tests of Lorentz violation in muon antineutrino to electron antineutrino oscillations

A recently developed Standard-Model Extension (SME) formalism for neutrino oscillations that includes Lorentz and CPT violation is used to analyze the sidereal time variation of the neutrino event excess measured by the Liquid Scintillator Neutrino Detector (LSND) experiment. The LSND experiment, performed at Los Alamos National Laboratory, observed an excess, consistent with neutrino oscillations, of ${\bar\nu}_e$ in a beam of ${\bar\nu}_\mu$. It is determined that the LSND oscillation signal is consistent with no sidereal variation. However, there are several combinations of SME coefficients that describe the LSND data; both with and without sidereal variations. The scale of Lorentz and CPT violation extracted from the LSND data is of order $10^{-19}$ GeV for the SME coefficients $a_L$ and $E \times c_L$. This solution for Lorentz and CPT violating neutrino oscillations may be tested by other short baseline neutrino oscillation experiments, such as the MiniBooNE experiment.Comment: 10 pages, 10 figures, 2 tables, uses revtex4 replaced with version to be published in Physical Review D, 11 pages, 11 figures, 2 tables, uses revtex

The Electron Energy Distribution in the Hotspots of Cygnus A: Filling the Gap with the Spitzer Space Telescope

Here we present Spitzer Space Telescope imaging of Cyg A with the Infrared Array Camera, resulting in the detection of the high-energy tails or cut-offs in the synchrotron spectra for all four hotspots of this archetype radio galaxy. When combined with the other data collected from the literature, our observations allow for detailed modeling of the broad-band emission for the brightest spots A and D. We confirm that the X-ray flux detected previously from these features is consistent with the synchrotron self-Compton radiation for the magnetic field intensity 170 muG in spot A, and 270 muG in spot D. We also find that the energy density of the emitting electrons is most likely larger by a factor of a few than the energy density of the hotspots' magnetic field. We construct energy spectra of the radiating ultrarelativistic electrons. We find that for both hotspots A and D these spectra are consistent with a broken power-law extending from at least 100 MeV up to 100 GeV, and that the spectral break corresponds almost exactly to the proton rest energy of 1 GeV. We argue that the shape of the electron continuum reflects two different regimes of the electron acceleration process at mildly relativistic shocks, rather than resulting from radiative cooling and/or absorption effects. In this picture the protons' inertia defines the critical energy for the hotspot electrons above which Fermi-type acceleration processes may play a major role, but below which the operating acceleration mechanism has to be of a different type. At energies >100 GeV, the electron spectra cut-off/steepen again, most likely as a result of spectral aging due to radiative loss effects. We discuss several implications of the presented analysis for the physics of extragalactic jets.Comment: 29 pages, 8 figures and 2 tables included. Accepted for publication in Ap

Preliminary design for Arctic atmospheric radiative transfer experiments

If current plans are realized, within the next few years, an extraordinary set of coordinated research efforts focusing on energy flows in the Arctic will be implemented. All are motivated by the prospect of global climate change. SHEBA (Surface Energy Budget of the Arctic Ocean), led by the National Science Foundation (NSF) and the Office of Naval Research (ONR), involves instrumenting an ice camp in the perennial Arctic ice pack, and taking data for 12-18 months. The ARM (Atmospheric Radiation Measurement) North Slope of Alaska and Adjacent Arctic Ocean (NSA/AAO) Cloud and Radiation Testbed (CART) focuses on atmospheric radiative transport, especially in the presence of clouds. The NSA/AAO CART involves instrumenting a sizeable area on the North Slope of Alaska and adjacent waters in the vicinity of Barrow, and acquiring data over a period of about 10 years. FIRE (First ISCCP (International Satellite Cloud Climatology Program) Regional Experiment) Phase 3 is a program led by the National Aeronautics and Space Administration (NASA) which focuses on Arctic clouds, and which is coordinated with SHEBA and ARM. FIRE has historically emphasized data from airborne and satellite platforms. All three program anticipate initiating Arctic data acquisition during spring, 1997. In light of his historic opportunity, the authors discuss a strawman atmospheric radiative transfer experimental plan that identifies which features of the radiative transport models they think should be tested, what experimental data are required for each type of test, the platforms and instrumentation necessary to acquire those data, and in general terms, how the experiments could be conducted. Aspects of the plan are applicable to all three programs

Chandra and RXTE Spectra of the Burster GS 1826-238

Using simultaneous observations from Chandra and RXTE, we investigated the LMXB GS 1826-238 with the goal of studying its spectral and timing properties. The uninterrupted Chandra observation captured 6 bursts (RXTE saw 3 of the 6), yielding a recurrence time of 3.54 +/- 0.03 hr. Using the proportional counter array on board RXTE, we made a probable detection of 611 Hz burst oscillations in the decaying phases of the bursts with an average rms signal amplitude of 4.8%. The integrated persistent emission spectrum can be described as the dual Comptonization of ~ 0.3 keV soft photons by a plasma with kT_e ~ 20 keV and an optical depth of about 2.6 (interpreted as emission from the accretion disk corona), plus the Comptonization of hotter ~ 0.8 keV seed photons by a ~ 6.8 keV plasma (interpreted as emission from or near the boundary layer). We discovered evidence for a neutral Fe K\alpha emission line, and we found interstellar Fe L_II and Fe L_III absorption features. The burst spectrum can be fit by fixing the disk Comptonization parameters to the persistent emission best-fit values, and adding a blackbody. The blackbody/seed photon temperature at the peak of the burst is ~ 1.8 keV and returns to ~ 0.8 keV over 200 s. The blackbody radius is consistent with R_bb = 10.3-11.7 km assuming a distance of 6 kpc; however, by accounting for the fraction of the surface that is obscured by the disk as a function of binary inclination, we determined the source distance must actually be near 5 kpc in order for the stellar radius to lie within the commonly assumed range of 10-12 km.Comment: Accepted for publication in ApJ; 13 pages, 6 figure

Search for π0→νμνˉμ\pi^0 \to \nu_{\mu}\bar\nu_{\mu} Decay in LSND

We observe a net beam-excess of $8.7 \pm 6.3$ (stat) $\pm 2.4$ (syst) events, above 160 MeV, resulting from the charged-current reaction of $\nu_{\mu}$ and/or $\bar\nu_{\mu}$ on C and H in the LSND detector. No beam related muon background is expected in this energy regime. Within an analysis framework of $\pi^0 \to \nu_{\mu}\bar\nu_{\mu}$, we set a direct upper limit for this branching ratio of $\Gamma(\pi^0 \to \nu_\mu \bar\nu_\mu) / \Gamma(\pi^0 \to all) < 1.6 \times 10^{-6}$ at 90% confidence level.Comment: 4 pages, 4 figure