Showing papers on "Point source published in 2004"

TeV Gamma-Ray Observations of the Galactic Center

Abstract: We report a possible detection of TeV gamma-rays from the Galactic Center by the Whipple 10m gamma-ray telescope. Twenty-six hours of data were taken over an extended period from 1995 through 2003 resulting in a total significance of 3.7 standard deviations. The measured excess corresponds to an integral flux of \Flux above an energy of $2.8 \mathrm{TeV}$, roughly 40% of the flux from the Crab Nebula at this energy. The 95% confidence region has an angular extent of about 15 arcmin and includes the position of Sgr A*. The detection is consistent with a point source and shows no evidence for variability.

Interaction of a scanning laser-generated ultrasonic line source with a surface-breaking flaw

Abstract: The scanning laser source (SLS) technique has been proposed recently as an effective way to investigate small surface-breaking cracks. By monitoring the amplitude and frequency changes of the ultrasound generated as the SLS scans over a defect, the SLS technique has provided enhanced signal-to-noise performance compared to the traditional pitch-catch or pulse-echo ultrasonic methods. In previous work, either a point source or a short line source was used for generation of ultrasound. The resulting Rayleigh wave was typically bipolar in nature. In this paper, a scanning laser line source (SLLS) technique using a true thermoelastic line source (which leads to generation of monopolar surface waves) is demonstrated experimentally and through numerical simulation. Experiments are performed using a line-focused Nd:YAG laser and interferometric detection. For the numerical simulation, a hybrid model combining a mass-spring lattice method (MSLM) and a finite difference method (FDM) is used. As the SLLS is scanned over a surface-breaking flaw, it is shown both experimentally and numerically that the monopolar Rayleigh wave becomes bipolar, dramatically indicating the presence of the flaw.

Radio Astronomical Polarimetry and Point-Source Calibration

Abstract: A mathematical framework is presented for use in the experimental determination of the polarimetric response of observatory instrumentation. Elementary principles of linear algebra are applied to model the full matrix description of the polarization measurement equation by least-squares estimation of nonlinear, scalar parameters. The formalism is applied to calibrate the center element of the Parkes Multibeam receiver using observations of the millisecond pulsar PSR J0437-4715 and the radio galaxy 3C 218 (Hydra A).

The 21-cm emission from the reionization epoch: extended and point source foregrounds

Abstract: Fluctuations in the redshifted 21-cm emission from neutral hydrogen probe the epoch of reionization. We examine the observability of this signal and the impact of extragalactic foreground radio sources (both extended and point-like). We use cosmological simulations to predict the angular correlation functions of intensity fluctuations due to unresolved radio galaxies, cluster radio haloes and relics and free‐free emission from the interstellar and intergalactic medium at the frequencies and angular scales relevant for the proposed 21-cm tomography. In accord with previous findings, the brightness temperature fluctuations due to foreground sources are much larger than those from the primary 21-cm signal at all scales. In particular, diffuse cluster radio emission, which has been previously neglected, provides the most significant foreground contamination. However, we show that the contribution to the angular fluctuations at scales θ 1 arcmin is dominated by the spatial clustering of bright foreground sources. This excess can be removed if sources above flux levels S 0.1 mJy (out to redshifts of z ∼ 1 and z ∼ 2 for diffuse and point sources, respectively) are detected and removed. Hence, efficient source removal may be sufficient to allow the detection of angular fluctuations in the 21-cm emission free of extragalactic foregrounds at θ 1 arcmin. In addition, the removal of sources above S = 0.1 mJy also reduces the foreground fluctuations to roughly the same level as the 21-cm signal at scales θ 1 arcmin. This should allow the substraction of the foreground components in frequency space, making it possible to observe in detail the topology and history of reionization. Ke yw ords: galaxies: active ‐ intergalactic medium ‐ cosmology: theory ‐ diffuse radiation ‐ radio continuum: general.

The 21 centimeter emission from the reionization epoch: extended and point source foregrounds

Abstract: Fluctuations in the redshifted 21 centimeter emission from neutral hydrogen probe the epoch of reionization. We examine the observability of this signal and the impact of extragalactic foreground radio sources. We use cosmological simulations to predict the angular correlation functions of intensity fluctuations due to unresolved radio galaxies, cluster radio halos and relics and free-free emission from the interstellar and intergalactic medium at the frequencies and angular scales relevant for the proposed 21cm tomography. In accord with previous findings, the brightness temperature fluctuations due to foreground sources are much larger than those from the primary 21cm signal at all scales. In particular, diffuse cluster radio emission, which has been previously neglected, provides the most significant foreground contamination. However, we show that the contribution to the angular fluctuations at scales \theta > 1' is dominated by the spatial clustering of bright foreground sources. This excess can be removed if sources above flux levels S > 0.1 mJy are detected and removed. Hence, efficient source removal may be sufficient to allow the detection of angular fluctuations in the 21cm emission free of extragalactic foregrounds at \theta > 1 arcmin. In addition, the removal of sources above S=0.1 mJy also reduces the foreground fluctuations to roughly the same level as the 21cm signal at scales \theta < 1 arcmin. This should allow the substraction of the foreground components in frequency space, making it possible to observe in detail the topology and history of reionization.

X-Ray, Radio, and Optical Observations of the Putative Pulsar in the Supernova Remnant CTA 1

Abstract: A Chandra image of the central X-ray source RX J0007.0+7303 in the supernova remnant CTA 1 reveals a point source, a compact nebula, and a bent jet, all of which are characteristic of energetic, rotation-powered pulsars. Using the MDM 2.4 m telescope we obtain upper limits in the optical at the position of the point source, (J2000.0) 00 h 07 m 01: 56, þ73 � 03 0 08B1, determined to an accuracy of 0B1, of B > 25:4, V > 24:8, R > 25:1, and I > 23:7; these correspond to an X-ray–to–optical flux ratiok100. Neither a Very Large Array image at 1425 MHz nor a deep pulsar search at 820 MHz using the NRAO Green Bank Telescope reveal a radio pulsar counterpart to an equivalent luminosity limit at 1400 MHz of 0.02 mJy kpc 2 , which is equal to the lowest luminosity known for any radio pulsar. The Chandra point source accounts for � 30% of the fl ux of RX J0007.0+7303, while its compact nebula plus jet comprise � 70%. The X-ray spectrum of the point source is fitted with a power law–plus–blackbody model with � ¼ 1:6 � 0:6, kT1 ¼ 0:13 � 0:05 keV, and R1 ¼ 0:37 km, values typical of a young pulsar. An upper limit of T 1 e < 6:6 ;10 5 K to the effective temperature of the entire neutron star surface is derived, which is one of the most constraining data points on cooling models. The 0.5– 10 keV10 keV luminosity of RX J0007.0+7303 is � 4 ;10 31 (d=1:4 kpc) 2 ergs s � 1 , but the larger (� 18 0 diameter) synchrotron nebula in which it is embedded is 2 orders of magnitude more luminous. These properties allow us to estimate, albeit crudely, that the spin-down luminosity of the underlying pulsar is in the range 10 36 –10 37 ergs s � 1 , and support the identification of the high-energy � -ray source 3EG J0010+7309 as a pulsar even though its spin parameters have not yet been determined. Subject headingg ISM: individual (CTA 1) — stars: individual (3EG J0010+7309, RX J0007.0+7303) — stars: neutron — supernova remnants

The structure of the NGC 1333-IRAS2 protostellar system on 500 AU scales - An infalling envelope, a circumstellar disk, multiple outflows, and chemistry

Abstract: This paper investigates small-scale (500 AU) structures of dense gas and dust around the low-mass protostellar binary NGC 1333-IRAS2 using millimeter-wavelength aperture-synthesis observations from the Owens Valley and Berkeley-Illinois-Maryland-Association interferometers. The detected λ=3 mm continuum emission from cold dust is consistent with models of the envelope around IRAS2A , based on previously reported submillimeter-continuum images, down to the 3", or 500 AU, resolution of the interferometer data. Our data constrain the contribution of an unresolved point source to 22 mJy. The importance of different parameters, such as the size of an inner cavity and impact of the interstellar radiation field, is tested. Within the accuracy of the parameters describing the envelope model, the point source flux has an uncertainty by up to 25%. We interpret this point source as a cold disk of mass ≳0.3 M_⊙. The same envelope model also reproduces aperture-synthesis line observations of the optically thin isotopic species C^(34)S and H^(13)CO^+. The more optically thick main isotope lines show a variety of components in the protostellar environment: N_(2)H^+ is closely correlated with dust concentrations as seen at submillimeter wavelengths and is particularly strong toward the starless core IRAS2C . We hypothesize that N_(2)H^+ is destroyed through reactions with CO that is released from icy grains near the protostellar sources IRAS2A and B. CS, HCO^+, and HCN have complex line shapes apparently affected by both outflow and infall. In addition to the east-west jet seen in SiO and CO originating from IRAS2A, a north-south velocity gradient near this source indicates a second, perpendicular outflow. This suggests the presence of a binary companion within 0."3 (65 AU) from IRAS2A as driving source of this outflow. Alternative explanations of the velocity gradient, such as rotation in a circumstellar envelope or a single, wide-angle ( $90^\circ$) outflow are less likely.

Continuum limit of amorphous elastic bodies II: Linear response to a point source force

Abstract: The linear response of two-dimensional amorphous elastic bodies to an external delta force is determined in analogy with recent experiments on granular aggregates. For the generated forces, stress, and displacement fields, we find strong relative fluctuations of order 1 close to the source, which, however, average out readily to the classical predictions of isotropic continuum elasticity. The stress fluctuations decay (essentially) exponentially with distance from the source. Only beyond a surprisingly large distance, $b\ensuremath{\approx}30$ interatomic distances, self-averaging dominates, and the quenched disorder becomes irrelevant for the response of an individual configuration. We argue that this self-averaging length $b$ also sets the lower wavelength bound for the applicability of classical eigenfrequency calculations. Particular attention is paid to the displacements of the source, allowing a direct measurement of the local rigidity. The algebraic correlations of these displacements demonstrate the existence of domains of slightly different rigidity without, however, revealing a characteristic length scale, at least not for the system sizes we are able to probe.

Track Reconstruction and Point Source Searches with Antares

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The 1997–1998 Umbria‐Marche sequence (central Italy): Source, path, and site effects estimated from strong motion data recorded in the epicentral area

Abstract: [1] We apply a nonparametric spectral inversion scheme to calculate source spectra, S wave attenuation, and site transfer functions from strong motion records in the epicentral region of the 1997–1998 Umbria-Marche seismic sequence (central Italy). We use records from moderate size earthquakes (4.6 ≤ Ml ≤ 5.9) to parameterize the spectral amplitude decay in the distance range from 5 to 40 km. We find that the average quality factor Q can be approximated by Q(f) = 49 f0.9, between 0.5 and 8 Hz, and the geometrical spreading by r−0.9. At high frequencies (f > 8 Hz) the dependence of Q on frequency weakens, and it takes an approximate constant value of 318. We fit the source spectra to the ω-square model and calculate an average stress drop of (2 ± 1) MPa. The average value is consistent with the previous estimates from the weak events (1.4 < Ml < 4.5) of the Umbria-Marche seismic sequence. The most remarkable site effects are found in correspondence of large sedimentary basins, filled by alternation of sandy-clayey deposits. The estimated spectral parameters are used to simulate acceleration spectra recorded during several earthquakes of the Umbria-Marche sequence. Both point source and finite fault effects are considered. Furthermore, attenuation relationships for peak ground velocity and ground acceleration are estimated using synthetic data, and compared to existing relationships.

Entry dynamics and acoustics/infrasonic/seismic analysis for the Neuschwanstein meteorite fall

Abstract: We have analyzed several types of data associated with the well-documented fall of the Neuschwanstein meteorites on April 6, 2002 (a total of three meteorites have been recovered). This includes ground-based photographic and radiometer data as well as infrasound and seismic data from this very significant bolide event (Spurný et al. 2002, 2003). We have also used these data to model the entry of Neuschwanstein, including the expected dynamics, energetics, panchromatic luminosity, and associated fragmentation effects. In addition, we have calculated the differential efficiency of acoustical waves for Neuschwanstein and used these values to compare against the efficiency calculated using available ground-based infrasound data. This new numerical technique has allowed the source height to be determined independent of ray tracing solutions. We have also carried out theoretical ray tracing for a moving point source (not strictly a cylindrical line emission) and for an infinite speed line source. In addition, we have determined the ray turning heights as a function of the source height for both initially upward and downward propagating rays, independent of the explicit ray tracing (detailed propagation path) programs. These results all agree on the origins of the acoustic emission and explicit source heights for Neuschwanstein for the strongest infrasonic signals. Calculated source energies using more than four different independent approaches agree that Neuschwanstein was certainly <500 kg in initial mass, given the initial velocity of 20.95 km/s, resulting in an initial source energy ≤0.015-0.0276 kt TNT equivalent (4.185 x 10^12 J). Local source energies at the calculated infrasonic/seismic source altitudes are up to two orders of magnitude smaller than this initial source energy.

Limits on supersymmetric dark matter from EGRET observations of the galactic center region

Abstract: In most supersymmetic models, neutralino dark matter particles are predicted to accumulate in the Galactic center and annihilate generating, among other products, gamma rays. The Energetic Gamma Ray Experiment Telescope has made observations in this region, and is sensitive to gamma rays from 30 MeV to {approx}30 GeV. We have used an improved point source analysis including an energy dependent point spread function and an unbinned maximum likelihood technique, which has allowed us to lower the limits on gamma ray flux from the Galactic center by more than 1 order of magnitude. We find that the present Energetic Gamma Ray Experiment Telescope data can limit many supersymmetric models if the density of the Galactic dark matter halo is cuspy or spiked toward the Galactic center. We also discuss the ability of the Gamma ray Large Area Space Telescope to test these models.

Wideband RELAX and wideband CLEAN for aeroacoustic imaging.

Abstract: Microphone arrays can be used for acoustic source localization and characterization in wind tunnel testing. In this paper, the wideband RELAX (WB-RELAX) and the wideband CLEAN (WB-CLEAN) algorithms are presented for aeroacoustic imaging using an acoustic array. WB-RELAX is a parametric approach that can be used efficiently for point source imaging without the sidelobe problems suffered by the delay-and-sum beamforming approaches. WB-CLEAN does not have sidelobe problems either, but it behaves more like a nonparametric approach and can be used for both point source and distributed source imaging. Moreover, neither of the algorithms suffers from the severe performance degradations encountered by the adaptive beamforming methods when the number of snapshots is small and/or the sources are highly correlated or coherent with each other. A two-step optimization procedure is used to implement the WB-RELAX and WB-CLEAN algorithms efficiently. The performance of WB-RELAX and WB-CLEAN is demonstrated by applying them to measured data obtained at the NASA Langley Quiet Flow Facility using a small aperture directional array (SADA). Somewhat surprisingly, using these approaches, not only were the parameters of the dominant source accurately determined, but a highly correlated multipath of the dominant source was also discovered.

The Interpretation of Gravity Changes and Crustal Deformation in Active Volcanic Areas

Abstract: Simple models, like the well-known point source of dilation (Mogi's source) in an elastic, homogeneous and isotropic half-space, are widely used to interpret geodetic and gravity data in active volcanic areas. This approach appears at odds with the real geology of volcanic regions, since the crust is not a homogeneous medium and magma chambers are not spheres. In this paper, we evaluate several more realistic source models that take into account the influence of self-gravitation effects, vertical discontinuities in the Earth's density and elastic parameters, and non-spherical source geometries. Our results indicate that self-gravitation effects are second order over the distance and time scales normally associated with volcano monitoring. For an elastic model appropriate to Long Valley caldera, we find only minor differences between modeling the 1982-1999 caldera unrest using a point source in elastic, homogeneous half-spaces, or in elasto-gravitational, layered half-spaces. A simple experiment of matching deformation and gravity data from an ellipsoidal source using a spherical source shows that the standard approach of fitting a center of dilation to gravity and uplift data only, excluding the horizontal displacements, may yield estimates of the source parameters that are not reliable. The spherical source successfully fits the uplift and gravity changes, overestimating the depth and density of the intrusion, but is not able to fit the radial displacements.

Qualitative Aspects of Quasar Microlensing with Two Mass Components: Magnification Patterns and Probability Distributions

Abstract: It has been conjectured that the distribution of magnifications of a point source microlensed by a randomly distributed population of intervening point masses is independent of its mass spectrum. We present gedanken experiments that cast doubt on this conjecture and numerical simulations that show it to be false.

A thorough study of the intriguing X-ray emission from the Cartwheel ring

Abstract: We present the results from the high resolution Chandra observation of the Cartwheel galaxy. Many individual sources are resolved in the image, mostly associated with the outer ring. All detected sources have a very high X-ray luminosity (${\geq} 10^{39}$ erg s -1 ) that classifies them as Ultra Luminous X-ray sources (ULX). The brightest of them is possibly the most luminous individual non-nuclear source observed so far, with $L_{\rm X} \sim 10^{41}$ erg s -1 (at $D=122$ Mpc). The spatial extent of this source is consistent with a point source at the Chandra resolution. The luminosity function of individual X-ray sources extends about an order of magnitude higher than previously reported in other galaxies. We discuss this in the context of the “universal” luminosity function for High Mass X-ray Binaries and we derive a Star Formation Rate higher than in other starburst galaxies studied so far. A diffuse component, associated with hot gas, is present. However, deeper observations that we will obtain with XMM-Newton are needed to constrain its properties.

Chandra & XMM-Newton Observations of NGC5253. Analysis of the X-ray Emission from a Dwarf Starburst Galaxy

Abstract: We present Chandra and XMM-Newton X-ray data of NGC5253, a local starbursting dwarf elliptical galaxy, in the early stages of a starburst episode. Contributions to the X-ray emission come from discrete point sources and extended diffuse emission, in the form of what appear to be multiple superbubbles, and smaller bubbles probably associated with individual star clusters. Chandra detects 17 sources within the optical extent of NGC5253 down to a completeness level corresponding to a luminosity of 1.5E37 erg/s.The slope of the point source X-ray luminosity function is -0.54, similar to that of other nearby dwarf starburst galaxies. Several different types of source are detected within the galaxy, including X-ray binaries and the emission associated with star-clusters. Comparison of the diffuse X-ray emission with the observed Halpha emission shows similarities in their extent. The best spectral fit to the diffuse emission is obtained with an absorbed, two temperature model giving temperatures for the two gas components of ~0.24keV and ~0.75keV.The derived parameters of the diffuse X-ray emitting gas are as follows: a total mass of \~1.4E6 f^{1/2} Msun, where f is the volume filling factor of the X-ray emitting gas, and a total thermal energy content for the hot X-ray emitting gas of \~3.4E54 f^{1/2} erg. The pressure in the diffuse gas is P/k ~ 1E6f^{-1/2}K/cm3. We find that these values are broadly commensurate with the mass and energy injection from the starburst population. Analysis of the kinematics of the starburst region suggest that the stellar ejecta contained within it can escape the gravitational potential well of the galaxy, and pollute the surrounding IGM.

X-Ray Observations of the Compact Source in CTA 1

Abstract: We have studied the point source RX J0007.0+7302, at the center of supernova remnant CTA 1, using the X-Ray Multi-mirror Mission (XMM-Newton). The X-ray spectrum of the source is consistent with that of a neutron star and is well described by a power law with the addition of a soft thermal component that may correspond to emission from hot polar cap regions or to cooling emission from a light-element atmosphere over the entire star. There is evidence of extended emission on small spatial scales, which may correspond to structure in the underlying synchrotron nebula. No pulsations are observed. Extrapolation of the nonthermal spectrum of RX J0007.0+7302 to gamma-ray energies yields a flux consistent with that of EGRET source 3EG J0010+7309, supporting the proposition that there is a gamma-ray-emitting pulsar at the center of CTA 1. Observations of the outer regions of CTA 1 with ASCA confirm earlier detections of thermal emission from the supernova remnant and show that the synchrotron nebula extends to the outermost reaches of the remnant.

Thermal Analysis of Welds

Abstract: Chapter 1: Introduction to welding processes and heat sources Introduction Introduction to the welding processes Introduction to welding arc Introduction to heat sources Summary Chapter 2: Methods of analysis Introduction Background for solving heat conduction equations Superposition of point source solution Summary Chapter 3: Analytical solutions for basic heat sources Introduction Point heat source in infinite body Line heat source in infinite body Plane heat source in infinite body Area heat source Circular disc heat source on semi-infinite body Cylindrical surface source in infinite body Spherical surface source in infinite body Cylindrical solid heat source in infinite body Summary Chapter 4: Analytical solutions for 2D Gaussian-distributed heat sources Introduction Surface heat source in semi-infinite body Gaussian-distributed surface heat source in thick plate Summary Chapter 5: Analytical solutions for spherical heat sources Introduction Spherical heat source in a semi-infinite body Spherical heat source in thick plate Spherical heat source in cylindrical body Summary Chapter 6: Analytical solutions for single-ellipsoidal density heat source Introduction Single ellipsoidal heat sources in semi-infinite body Single ellipsoidal heat sources in finite thick plate Hybrid ellipsoid heat source in fillet joint Analytical solution for single-ellipsoidal heat sources in cylinder Single ellipsoidal heat sources in solid sphere Single ellipsoidal heat sources in solid cone Summary Chapter 7: Analytical solutions for double-ellipsoidal density heat source Introduction Double-ellipsoidal heat sources in semi-infinite body Double-ellipsoidal heat sources in finite plate Hybrid double-ellipsoidal heat sources in fillet joint Analytical solution for double-ellipsoidal heat source in a cylinder Analytical solution for double-ellipsoidal heat source in a sphere Double-ellipsoidal heat sources in solid cone Hybrid double-ellipsoidal heat source in a semi-infinite body Summary Chapter 8: Application in weld-pool shape simulation Introduction Specimen and materials Transient temperature distribution Weld-pool shape simulation A simple weld bead prediction model Summary Chapter 9: Thermal stresses and distortions Introduction General equations for thermal stress Thermal stresses of infinite body Thermal stresses in thin plate Thermal stresses in thick plate Thermal stress in beams Thermal stress in solid sphere Distortions of welds Summary Chapter 10: Modelling of residual stresses in welded joints Introduction Residual stresses in bead-on-plate weld Residual stresses in multipass gusset joint Summary Chapter 11: Microstructure modelling of fusion welds Introduction Peak temperature Cooling rate Cooling time HAZ-width Austenitising time Grain growth modelling Microstructure volume fraction diagram Hardness and material strength in HAZ Summary

On the spectroastrometric separation of binary point-source fluxes

Abstract: Spectroastrometry is a technique which has the potential to resolve flux distributions on scales of milliarcseconds. In this study, we examine the application of spectroastrometry to binary point sources which are spatially unresolved due to the observational point spread function convolution. The technique uses measurements with sub-pixel accuracy of the position centroid of high signal-to-noise long-slit spectrum observations. With the objects in the binary contributing fractionally more or less at different wavelengths (particularly across spectral lines), the variation of the position centroid with wavelength provides some information on the spatial distribution of the flux. We examine the width of the flux distribution in the spatial direction, and present its relation to the ratio of the fluxes of the two components of the binary. Measurement of three observables (total flux, position centroid and flux distribution width) at each wavelength allows a unique separation of the total flux into its component parts even though the angular separation of the binary is smaller than the observations' point-spread function. This is because we have three relevant observables for three unknowns (the two fluxes, and the angular separation of the binary), which therefore generates a closed problem. This is a wholly different technique than conventional deconvolution methods, which produce information on angular sizes of the sampling scale. Spectroastrometry can produce information on smaller scales than conventional deconvolution, and is successful in separating fluxes in a binary object with a separation of less than one pixel. We present an analysis of the errors involved in making binary object spectroastrometric measurements and the separation method, and highlight necessary observing methodology.

Source modelling of road vehicles

Abstract: The state-of-the-art of acoustic source modelling of road vehicles has been reviewed. Extensive measurements and simulations have been carried out. The aim has been to identify and quantify all relevant parameters influencing the noise emission of road vehicles. The collected information has been used to construct a source model suitable to combine with point-to-point sound propagation theory to calculate day-evening-night weighted yearly average sound pressure levels of road traffic noise. Each vehicle category is represented by two point sources, each having a specified sound power having contributions from tyre/road (rolling) noise and propulsion noise. As a minimum 3 vehicle categories are used: Passenger cars, medium heavy and heavy vehicles. Additional categories are defined. The medium heavy vehicle has two axles and the heavy vehicle has 3 or more axles but corrections are made for the number of axles. All default data refer to a reference condition: constant speed, 20 °C and the average of DAC 0/11 and SMA 0/11 road surfaces. Deviations from these conditions are corrected for. Default data, one constant and one speed coefficient, for rolling noise are given for each frequency band, 25-10000 Hz, using a logarithmic speed dependence. 80% of the rolling noise sound power is assigned a point source at 0,01 m and 20% is assigned a point source at 0,3 m (passenger cars) or 0,75 m (heavy vehicles). Default data, one constant and one speed coefficient, for propulsion noise are given for each frequency band, 25-10000 Hz, using a linear speed dependence. 20% of the propulsion noise sound power is assigned a point source at 0,01 m and 80% is assigned a point source at 0,3 m (passenger cars) or 0,75 m (heavy vehicles). Rolling noise is corrected for different road surfaces and different air temperatures. It is also possible to correct for wetness, studded tyres and number of axles of heavy vehicles. Propulsion noise is corrected for acceleration/deceleration. All point sources are assigned a specific frequency dependent vertical directivity with the main purpose to take the screening of the car body into account. The lowest point source is assigned a specific frequency dependent horizontal directivity with the main purpose to take the horn effect of the tyre/road source into account. The highest point source for propulsion noise and heavy vehicles is assigned a frequency independent horizontal directivity. Propagation effects are taken into account by giving different acoustic impedances of some different road surfaces.

X-ray emission from the double pulsar system J0737-3039

Abstract: We report on a 10 ks observation of the double pulsar system J0737-3039 obtained with the Chandra X-Ray Observatory's Advanced CCD Imaging Spectrometer. We detect the system as a point source with coordinates (J2000.0) R.A. = 07h37m5123, decl. = -30°39'409, making this the first double neutron star system to be detected at X-ray energies. Only 77 source counts are detected. The data are represented satisfactorily by a power-law spectrum with photon index Γ = 2.9 ± 0.4. The inferred 0.2-10 keV luminosity is ≈2 × 1030 ergs s-1 for a distance of 0.5 kpc. We do not detect any significant variability with orbital phase in these data, which span one full orbit. These results are consistent with the X-ray emission originating solely from the magnetosphere of the energetic A pulsar, with an efficiency for conversion of rotational energy to X-rays in this band of ~0.04%, although we cannot exclude other possibilities.

Performance summary on a high power dense plasma focus x-ray lithography point source producing 70 nm line features in AlGaAs microcircuits

Abstract: A high average power dense plasma focus (DPF), x-ray point source has been used to produce ∼70 nm line features in AlGaAs-based monolithic millimeter-wave integrated circuits (MMICs). The DPF source has produced up to 12 J per pulse of x-ray energy into 4π steradians at ∼1 keV effective wavelength in ∼2 Torr neon at pulse repetition rates up to 60 Hz, with an effective x-ray yield efficiency of ∼0.8%. Plasma temperature and electron concentration are estimated from the x-ray spectrum to be ∼170 eV and ∼5·1019 cm−3, respectively. The x-ray point source utilizes solid-state pulse power technology to extend the operating lifetime of electrodes and insulators in the DPF discharge. By eliminating current reversals in the DPF head, an anode electrode has demonstrated a lifetime of more than 5 million shots. The x-ray point source has also been operated continuously for 8 h run times at 27 Hz average pulse recurrent frequency. Measurements of shock waves produced by the plasma discharge indicate that overpressur...

Search for Cosmic-Ray Point Sources with KASCADE

Abstract: A survey of the northern hemisphere for astrophysical point sources with continuous emission of high-energy cosmic rays is presented Around 47 × 107 extensive air showers with primary energies above ≈300 TeV measured by the KASCADE detector field are selected for this analysis Besides the sky survey, a search for signal excess in the regions of the Galactic plane and of selected point-source candidates has been performed There is no evidence for any significant excess This is valid for an analysis of all recorded showers, as well as for a data set enhanced by γ-ray-induced showers An upper flux limit of around 3 × 10-10 m-2 s-1 for a steady point source that transits the zenith is obtained Additionally, the distribution of the arrival directions of extensive air showers with energies above 80 PeV was studied by an autocorrelation analysis

Search for Point Sources of Ultra-High Energy Cosmic Rays Above 40 EeV Using a Maximum Likelihood Ratio Test

Abstract: We present the results of a search for cosmic ray point sources at energies above 40 EeV in the combined data sets recorded by the AGASA and HiRes stereo experiments. The analysis is based on a maximum likelihood ratio test using the probability density function for each event rather than requiring an a priori choice of a fixed angular bin size. No statistically significant clustering of events consistent with a point source is found.