Point source

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

Perturbation theory for scattering of sound from a point source by a moving rough surface in the presence of refraction

Abstract: A general perturbation theory is presented which is valid for small surface waveheights and for acoustic wavelengths of the order of the ocean‐surface correlation length. Formal solutions for the perturbed field are given and are specialized, to the second order of approximation, for the case of a random ocean surface. The scattering reduces the intensity of the carrier (source) signal and creates signal sidebands that are not in general symmetric in amplitude about the carrier. A pair of system functions for the signal sidebands is defined.Subject Classification: 30.40, 30.30, 30.25; 20.15.

Discovery of an Energetic 38.5 ms Pulsar Powering the Gamma-ray Source IGR J18490-0000/HESS J1849-000

Abstract: We report the discovery of a 38.5 ms X-ray pulsar in observations of the soft γ-ray source IGR J18490–0000 with the Rossi X-ray Timing Explorer (RXTE). PSR J1849–0001 is spinning down rapidly with period derivative 1.42 × 10–14 s s–1, yielding a spin-down luminosity 9.8 × 1036 erg s–1, characteristic age 42.9 kyr, and surface dipole magnetic field strength Bs = 7.5 × 1011 G. Within the INTEGRAL/IBIS error circle lies a point-like XMM-Newton and Chandra X-ray source that shows evidence of faint extended emission consistent with a pulsar wind nebula (PWN). The XMM-Newton spectrum of the point source is well fitted by an absorbed power-law model with photon index ΓPSR = 1.1 ± 0.2, N H = (4.3 ± 0.6) × 1022 cm–2, and F PSR(2-10 keV) = (3.8 ± 0.3) × 10–12 erg cm–2 s–1, while the spectral parameters of the extended emission are roughly ΓPWN ≈ 2.1 and F PWN(2-10 keV) ≈ 9 × 10–13 erg cm–2 s–1. IGR J18490–0000 is also coincident with the compact TeV source HESS J1849–000. For an assumed distance of 7 kpc in the Scutum arm tangent region, the 0.35-10 TeV luminosity of HESS J1849–000 is 0.13% of the pulsar's spin-down energy, while the ratio F(0.35-10 TeV)/F PWN(2-10 keV) ≈ 2. These properties are consistent with leptonic models of TeV emission from PWNe, with PSR J1849–0001 in a stage of transition from a synchrotron X-ray source to an inverse Compton γ-ray source.

Radio Point Sources and the Thermal SZ Power Spectrum

Abstract: Radio point sources are strongly correlated with clusters of galaxies, so a significant fraction of the thermal Sunyaev-Zel'dovich (SZ) effect signal could be affected by point source contamination. Based on empirical estimates of the radio galaxy population, it is shown that the rms temperature fluctuations of the thermal SZ effect could be underestimated by as much as 30% at an observing frequency of 30 GHz at l>1000. The effect is larger at higher multipoles. If the recent report of excess power at small angular scales is to be explained by the thermal SZ effect, then radio point sources at an observing frequency of 30 GHz must be a surprisingly weak contaminant of the SZ effect for low-mass clusters.