نتایج جستجو برای: compton pectrometry
تعداد نتایج: 6452 فیلتر نتایج به سال:
The fraction of Compton thick sources is one of the main uncertainties left in understanding the AGN population. The Swift Burst Alert Telescope (BAT) all-sky survey, for the first time gives us an unbiased sample of AGN for all but the most heavily absorbed sourcesNH> 10 25 cm−2). Still, the BAT spectra (14 – 195 keV) are time-averaged over months of observations and therefore hard to compare ...
Since the discovery of nuclear gamma-rays, its imaging has been limited to pseudo imaging, such as Compton Camera (CC) and coded mask. Pseudo imaging does not keep physical information (intensity, or brightness in Optics) along a ray, and thus is capable of no more than qualitative imaging of bright objects. To attain quantitative imaging, cameras that realize geometrical optics is essential, w...
The modeling of 3D Compton scatter in SPECT is complicated by the use of a variety of collimator geometry. To date, effective and efficient modeling of 3D Compton scatter in parallel-beam SPECT has been made possible by Frey and Tsui [1], Zeng et al [2], and Bai et al [3]. For fan-beam and cone-beam SPECT, the model in [3] can effectively model first order 3D Compton scatter. But for varying-fo...
We investigate the effects of inverse Compton scattering by electrons and positrons in the unshocked winds of rotationally-powered binary pulsars. This process can scatter low energy target photons to produce gamma rays with energies from MeV to TeV. The binary radio pulsars PSR B1259−63 and PSR J0045−73 are both in close eccentric orbits around bright main sequence stars which provide a huge d...
We have investigated the role of the cyclotron emission associated to cosmic magnetic fields on the evolution of CMB spectral distortions by considering the contributions by spontaneous and stimulated emission and by absorption in the computation of the photon and energy injection rates. These cyclotron emission rates have been numerically compared with those of the relevant radiative processes...
The handbag contribution to Compton scattering factorises in parton-photon subpro-cess amplitudes and new form factors representing 1/x-moments of skewed parton distributions. A detailed phenomenological study for polarised and unpolarised real and virtual Compton scattering is presented. 1. The interest in the interplay between hard inclusive and exclusive reactions has recently been revived b...
Seed black holes formed in the collapse of population III stars have been invoked to explain the presence of supermassive black holes at high redshift. It has been suggested that a seed black hole can grow up to 10M⊙ through highly super-Eddington accretion for a period of ∼ 106∼7 yr between redshift z = 20∼ 24. We studied the feedback of radiation pressure, Compton heating and outflow during t...
Aims. We investigate whether the high energy tail detected by the Fermi/LAT for the short GRB 081024B can be caused by synchrotron and self-Compton emission in the context of either the internal or external shock models. Methods. For the internal shock scenario, we explore the possibility of generating the high energy photons directly by means of the synchrotron process, or inverse Compton emis...
A high resolution Compton telescope has been identified by the Gamma Ray Astronomy Program Working Group (GRAPWG) as the highest priority major mission in gamma ray astrophysics following GLAST. This mission should provide 25-100 times improved sensitivity, relative to CGRO and INTEGRAL, for MeV gamma ray lines. It must have good performance for narrow and broad lines and for discrete and diffu...
A synthesis model for the cosmic X–ray Background (XRB) is presented, which includes a proper treatment of Compton scattering in the absorbing matter for type 2 AGN. Evidence for a decrease of the relative importance of type 2 AGN at high redshift is found, which may be due either to a decrease of the relative number of obscured sources, or (more plausibly) to an increase of the fraction of Com...
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