Point source

About: Point source is a research topic. Over the lifetime, 5077 publications have been published within this topic receiving 94091 citations.

AKARI Infrared Camera Survey of the Large Magellanic Cloud. I. Point Source Catalog

Abstract: We present a near- to mid-infrared point source catalog of 5 photometric bands at 3.2, 7, 11, 15 and 24 um for a 10 deg2 area of the Large Magellanic Cloud (LMC) obtained with the Infrared Camera (IRC) onboard the AKARI satellite. To cover the survey area the observations were carried out at 3 separate seasons from 2006 May to June, 2006 October to December, and 2007 March to July. The 10-sigma limiting magnitudes of the present survey are 17.9, 13.8, 12.4, 9.9, and 8.6 mag at 3.2, 7, 11, 15 and 24 um, respectively. The photometric accuracy is estimated to be about 0.1 mag at 3.2 um and 0.06--0.07 mag in the other bands. The position accuracy is 0.3" at 3.2, 7 and 11um and 1.0" at 15 and 24 um. The sensitivities at 3.2, 7, and 24 um are roughly comparable to those of the Spitzer SAGE LMC point source catalog, while the AKARI catalog provides the data at 11 and 15 um, covering the mid-infrared spectral range contiguously. Two types of catalog are provided: a Catalog and an Archive. The Archive contains all the detected sources, while the Catalog only includes the sources that have a counterpart in the Spitzer SAGE point source catalog. The Archive contains about 650,000, 140,000, 97,000, 43,000, and 52,000 sources at 3.2, 7, 11, 15, and 24 um, respectively. Based on the catalog, we discuss the luminosity functions at each band, the color-color diagram, and the color-magnitude diagram using the 3.2, 7, and 11 um band data. Stars without circumstellar envelopes, dusty C-rich and O-rich stars, young stellar objects, and background galaxies are located at distinct regions in the diagrams, suggesting that the present catalog is useful for the classification of objects towards the LMC.

Slowing Down Distribution of U235 Fission Neutrons from a Point Source in Light Water

Abstract: The results of a measurement of the slowing down distribution in water of neutrons from a point fission source to indium resonance energy, 1.458 ev, are given. The second, fourth, sixth, and eighth moments of the measured distribution are calculated and have the values, r2=184.7 cm2, r4=1.222×105 cm4, r6=2.27×108 cm6, and r8=8.6×1011 cm8.

Ultrasonic point‐source/point‐receiver measurements in thin specimensa)

Abstract: This paper reports on the application of the ultrasonic point‐source/point‐receiver technique (PS/PR) to thin, anisotropic specimens. By using a scanned source and viewing a large number of signals measured at adjacent source/receiver configurations, one obtains a so‐called scan image which represents the detailed spatial and temporal characteristics of the elastic wave field in a specimen. The measurement system uses either a focused, pulsed laser beam operating as a dipole source or a small aperture, piezoceramic shear transducer serving as a monopolar source. Detection of the signals is with a sensitive piezoceramic sensor that responds to the lateral or shear motions of the specimen surface. Scan images were obtained in a Silicon wafer whose thickness was 625 μm and in one‐ or two‐ply, unidirectional, graphite/epoxy laminates whose thicknesses were approximately 145 and 275 μm, respectively. The experimental data are analyzed using a simple plane‐wave, plane‐stress model that describes the propagation of quasilongitudinal and quasitransverse membrane waves in the plane of the plate. Good agreement is obtained between the experimental and theoretical group velocity curves of the membrane waves in the laminates. It is shown that the measured group velocity data of different wave modes can be inverted to recover the elastic constants of a material with excellent reliability and accuracy. The measurement system was also used to map out the group velocities in branches comprising the cuspidal region of the quasi‐transverse group velocity curve.

An X-ray view of the active nucleus in NGC 4258

Abstract: XMM-Newton observed the Seyfert 1.9 galaxy NGC 4258 in December 2000. At energies above 2 keV a hard nuclear point source is resolved that can be tted by a highly absorbed power-law spectrum (NH= (8:0 0:4) 10 22 cm 2 , photon index 1:64 0:08) with an unabsorbed luminosity of 7.510 40 erg s 1 in the (2{ 10) keV band. No narrow iron K emission line is detected (90% upper limit of equivalent widthEW 40 eV). The nuclear emission flux was observed to remain constant over the observation. A short archival Chandra observation taken in March 2000 further constrains the hard emission to a point source coincident with the radio nucleus. A point source3 00 southwest of the nucleus does not contribute signicantly. Spectral results of the Chandra nuclear source are comparable (within the limited statistics) to the XMM-Newton parameters. The comparison of our iron line upper limit with reported detections indicates variability of the line EW. These results can be explained by the relatively low nuclear absorption of NGC 4258 (which is in the range expected for its intermediate Seyfert type) and some variability of the absorbing material. Reflection components as proposed to explain the large iron line EW of highly absorbed Seyfert 2 galaxies and/or variations in the accretion disk are however imposed by the time variability of the iron line flux.