نتایج جستجو برای: γ ray
تعداد نتایج: 371341 فیلتر نتایج به سال:
Context. Ground based Cherenkov telescope systems measure astrophysical γ-ray emission against a background of cosmic-ray induced air showers. The subtraction of this background is a major challenge for the extraction of spectra and morphology of γ-ray sources. Aims. The unprecedented sensitivity of the new generation of ground based very-high-energy γ-ray experiments such as H.E.S.S. has lead ...
Diffuse γ-ray radiation in galaxies is produced by cosmic ray interactions with the interstellar medium. With the completion of EGRET observations, the only extragalactic object from which there has been a positive detection of diffuse γ-ray emission is the Large Magellanic Cloud. We systematically estimate the expected diffuse γ-ray flux from Local Group galaxies, and determine their detectabi...
Observational γ-ray astronomy was born some forty years ago, when small detectors were flown in satellites, following a decade of theoretical predictions of its potential to discover the origin of cosmic rays via the π-decay mechanism. The seventies were a golden era for γ-ray and cosmic-ray astrophysics, with the (re)discovery of the “diffuse shock acceleration” theory for cosmic rays, and the...
Our knowledge of the high-energy universe will change dramatically over the next several years as new astronomical detectors of high-energy radiation reach their design sensitivities. Besides Swift and HESS, which are already making important discoveries, these include the ground-based imaging air-Cherenkov telescopes VERITAS and MAGIC, the γ-ray space telescopes GLAST and AGILE, and the partic...
Ionizing radiations such as X-ray and γ-ray can directly or indirectly produce clustered or multiple damages in DNA. Previous studies have reported that overexpression of DNA glycosylases in Escherichia coli (E. coli) and human lymphoblast cells caused increased sensitivity to γ-ray and X-ray irradiation. However, the effects and the mechanisms of other radiation, such as low dose rate radiatio...
Long duration γ-ray bursts are thought to be a rare subclass of stripped-envelope core-collapse supernovae that launch collimated relativistic outflows (jets). All γ-ray-burst-associated supernovae are spectroscopically of Type Ic with broad lines, but the fraction of broad-lined Type Ic supernovae harboring low-luminosity γ-ray-bursts remains largely unconstrained. Some supernovae should be ac...
LXeGRIT is the first prototype of a novel Compton telescope for MeV γ-ray astrophysics based on a Liquid Xenon Time Projection Chamber (LXeTPC), sensitive in the energy band of 0.15 – 10 MeV. In this homogeneous, 3D position sensitive detector, γ-rays with at least two interactions in the sensitive volume of 2800 cm 3 , are imaged as in a standard Compton telescope. γ-rays with a single interac...
This meeting covered the range of cosmic explosions from solar flares to γ-ray bursts. A common theme is the role of rotation and magnetic fields. New information from the Sun shows that a “magnetic carpet” contains most of the surface field that feeds the corona. Disk instabilities in protostellar disks may provide most of the growth of a protostar. Type Ia supernovae continue to give evidence...
Pulsars discovered since the end of the EGRET mission coincident with unidentified highenergy γ-ray sources are prime targets for AGILE. Both general surveys and targeted observations have been successful in finding energetic young pulsars in the plane of the Galaxy. For the latter, hard X-ray imaging followed by deep radio searches of X-ray sources is a proven route. High-resolution Chandra X-...
We use one-and-a-half dimensional particle-in-cell plasma simulations to study the interaction of a relativistic, strongly magnetized wind with an ambient medium. Such an interaction is a plausible mechanism which leads to generation of cosmological γ-ray bursts. We confirm the idea of Mészáros and Rees (1992) that an essential part (about 20%) of the energy that is lost by the wind in the proc...
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