The Converter Mechanism of Particle Acceleration and Its Applications to the Unidentified Egret Sources     

E. V. Derishev  F. A. Aharonian  V. V. Kocharovsky  Vl. V. Kocharovsky 《Astrophysics and Space Science》2005,297(1-4):21-30

We discuss the properties of gamma-ray radiation accompanying the acceleration of cosmic rays via the converter mechanism. The mechanism exploits multiple photon-induced conversions of high-energy particles from charged into neutral state (namely, protons to neutrons and electrons to photons) and back. Because a particle in the neutral state can freely cross the magnetic field lines, this allows to avoid both particle losses downstream and reduction in the energy gain factor, which normally takes place due to highly collimated distribution of accelerated particles. The converter mechanism efficiently operates in relativistic outflows under the conditions typical for Active Galactic Nuclei, Gamma-Ray Bursts, and microquasars, where it outperforms the standard diffusive shock acceleration. The accompanying radiation has a number of distinctive features, such as an increase of the maximum energy of synchrotron photons and peculiar radiation beam-pattern, whose opening angle is much wider at larger photon energies. This provides an opportunity to observe off-axis relativistic jets in GeV–TeV energy range. One of the implications is the possibility to explain high-latitude unidentified EGRET sources as off-axis but otherwise typical relativistic-jet sources, such as blazars.  相似文献   

Multi-Conjugate Adaptive Optics with laser guide stars: performance in the infrared and visible     

M. Le Louarn 《Monthly notices of the Royal Astronomical Society》2002,334(4):865-874

The assumption of the Gaussianity of primordial perturbations plays an important role in modern cosmology. The most direct test of this hypothesis consists of testing the Gaussianity of cosmic microwave background (CMB) maps. Counting the pixels with the temperatures in given ranges and thus estimating the one-point probability function of the field is the simplest of all the tests. Other usually more complex tests of Gaussianity generally use a great deal of the information already contained in the probability function. However, the most interesting outcome of such a test would be the signal of non-Gaussianity independent of the probability function. It is shown that the independent information has purely morphological character i.e. it depends on the geometry and topology of the level contours only. As an example we discuss in detail the quadratic model   v = u + α ( u ²-1)  ( u is a Gaussian field with   u¯ =0  and  〈 u ²〉=1  , α is a parameter) that may arise in slow-roll or two-field inflation models. We show that in the limit of small amplitude α the full information about the non-Gaussianity is contained in the probability function. If other tests are performed on this model they simply recycle the same information. A simple procedure allowing us to assess the sensitivity of any statistics to the morphological information is suggested. We provide an analytic estimate of the statistical limit for detecting the quadratic non-Gaussianity α _c as a function of the map size in the ideal situation when the scale of the field is resolved. This estimate is in a good agreement with the results of the Monte Carlo simulations of 256² and 1024² maps. The effect of resolution on the detection quadratic non-Gaussianity is also briefly discussed.  相似文献   

实验标定的一种地质温压计及其应用     

杨家喜 《地球科学与环境学报》1991,(4)

本文简略回顾了堇青石-石榴石-矽线石-石英地质温压计的研究历史,并介绍由Aranovich等人完成的最新实验研究。以内蒙古南部贺兰山群的麻粒岩相矽线石榴堇青片麻岩的温压计算为例,用Aranovich等人实验标定的温压计计算结果与石榴石-堇青石Fe-Mg交换反应温度计和石榴石-斜长石-矽线石-石英压力计的计算结果相当吻合;而应用含有假定的热力学参数的哈奇森的温压计与其它温压计计算结果有较大差别,温度明显偏低,与岩石形成于麻粒岩相变质条件这一地质事实不符。  相似文献   

Non-Gaussianity in the Very Small Array cosmic microwave background maps with smooth goodness-of-fit tests     

《Monthly notices of the Royal Astronomical Society》2006,369(2):909-920

  相似文献   

The cosmic microwave background and the ionization history of the Universe     

Antony Lewis  Jochen Weller †  Richard Battye 《Monthly notices of the Royal Astronomical Society》2006,373(2):561-570

  相似文献   

Constraints on Cardassian expansion     

W. J. Frith 《Monthly notices of the Royal Astronomical Society》2004,348(3):916-920

  相似文献   

Error analysis of quadratic power spectrum estimates for cosmic microwave background polarization: sampling covariance     

Anthony Challinor  Gayoung Chon 《Monthly notices of the Royal Astronomical Society》2005,360(2):509-532

  相似文献   

The Mexican hat wavelet family: application to point-source detection in cosmic microwave background maps     

J. González-Nuevo  F. Argüeso  M. López-Caniego  L. Toffolatti  J. L. Sanz  P. Vielva  D. Herranz 《Monthly notices of the Royal Astronomical Society》2006,369(4):1603-1610

  相似文献   

Relativistic Fermi acceleration with shock compressed turbulence     

Martin Lemoine  Benoît Revenu 《Monthly notices of the Royal Astronomical Society》2006,366(2):635-644

  相似文献   

CMB recombination lines of hydrogen: The differential spectrum     

V. K. Dubrovich  S. I. Grachev 《Astronomy Letters》2004,30(10):657-662

We have calculated the distortions of the cosmic microwave background (CMB) spectrum in the wavelength range 2–50 cm due to the superposition of the CMB hydrogen recombination radiation in subordinate lines. The level populations were determined by numerically solving the equation of recombination kinetics together with the statistical equilibrium equations for a 60-level model hydrogen atom. The relative distortions are ≈10^?7–10^?6, with their wavelength dependence having a low-contrast, wavy pattern. However, the contrast increases severalfold and becomes pronounced when passing to the differential distortion spectrum. We study the dependence of the distortions on cosmological parameters.  相似文献