On the burst activity of the Crab Nebula, as observed by air shower arrays

Recent experiments with the Fermi-LAT and AGILE satellite gamma-ray telescopes, in which bursts of gamma-rays from the Crab Nebula were detected in the energy range of ～100 MeV, have aroused keen interest, if not a sensation. However, data on a possible burst in the Crab Nebula at much higher energies of ～100 TeV were published more than 20 years ago. Characteristics of transient and stationary fluxes of gamma rays from the Crab Nebula in various energy ranges are discussed in this work, and it is shown that the old data obtained at ultra-high energies is reasonably consistent with the latest pattern of the source’s burst activity.     

An updated search of steady TeV γ-ray point sources in northern hemisphere using the Tibet air shower array

Using the data taken from Tibet Ⅱ High Density (HD) Array (1997 February--1999 September) and Tibet-Ⅲ array (1999 November--2005 November), our previous northern sky survey for TeV γ-ray point sources has now been updated by a factor of 2.8 improved statistics. From 0.0° to 60.0° in declination (Dec) range, no new TeV γ-ray point sources with sufficiently high significance were identified while the well-known Crab Nebula and Mrk421 remain to be the brightest TeV T-ray sources within the field of view of the Tibet air shower array. Based on the currently available data and at the 90% confidence level (C.L.), the flux upper limits for different power law index assumption are re-derived, which are approximately improved by 1.7 times as compared with our previous reported limits.     

Search for muons from the direction of cygnus X-3

Muons and multimuons detected in the Fréjus underground nucleon decay detector between February 1984 and January 1986 have been analyzed. No excess events are observed in the direction of Cygnus X-3, which yields a 90% confidence level upper flux limit of 0.8 × 10⁻¹² cm⁻² s⁻¹, for an average rock overburden of 5000 hg cm⁻² corresponding to energies ⪆ 3 TeV. Using the 4.79 h periodicity of Cygnus X-3, no signal is found in any phase interval.     

Cygnus X-3: Six years of observations atE0≥50 TeV from the Plateau Rosa array

Summary Cygnus X-3 has been observed from 1982 to 1987 at primary energyE ₀≃10¹⁴ eV from the Plateau Rosa array. The absolute excess in the counting rate from the source region amounts to 0.15%, mostly concentrated in 1982 and 1986. The effect is observed in two classes of events although with small significance (2 and 1.4 s.d.). The 1986 data are consistent with observations of other arrays. The study of the 4.8 h time periodicity over a long observation time does not show any significant structure (2.5 s.d. excess at phase 0.2÷0.5). In 1982 and 1986 the light curves show respectively a wide excess between phases 0.60 and 0.85 and a 2.7 s.d. excess at phase 0.2÷0.25. The analysis of daily excesses from the source shows a good agreement with the expectations from pure statistical fluctuations, and no significant evidence of burst activity. To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee.     

One model for magnetic solar neutrino interactions,cosmological neutrino decays,and new particle resonant production by interactions of neutrinos from Cygnus X-3

Standard model extensions which include a charged, weak-singlet scalar particle can induce an electron-neutrino magnetic moment large enough to implement the Voloshin-Vysotski-Okun solution to the solar neutrino problem and observed anticorrelation of sunspots and neutrino flux. The resonant production and decay of such a charged scalar particle by neutrinos from ultra-high energy point sources of cosmic rays such as Cygnus X-3 has been discussed in the literature as a possible source of an anomalous muon signal in deep underground detectors. We argue here that there are versions of the charged scalar model which simultaneously can accommodate the above phenomena and in addition predict a radiative neutrino decay whose lifetime is about 10²⁴ s. This value is consistent with that needed for a dark-matter neutrino of about 30 eV mass to yield a flux of UV photons which could explain several puzzling observations of H_α emission from the galactic disk and from the intergalactic HI cloud in Leo.     

Reevaluation of the 22Na(p,gamma) reaction rate: implications for the detection of 22Na gamma rays from novae

Understanding the processes which create and destroy 22Na is important for diagnosing classical nova outbursts. Conventional 22Na(p,gamma) studies are complicated by the need to employ radioactive targets. In contrast, we have formed the particle-unbound states of interest through the heavy-ion fusion reaction, 12C(12C,n)23Mg and used the Gammasphere array to investigate their radiative decay branches. Detailed spectroscopy was possible and the 22Na(p,gamma) reaction rate has been reevaluated. New hydrodynamical calculations incorporating the upper and lower limits on the new rate suggest a reduction in the yield of 22Na with respect to previous estimates, implying a reduction in the maximum detectability distance for 22Na gamma rays from novae.     

Search for periodicities in galactic cosmic rays,sunspots and coronal index before arrival of relativistic protons from the sun

Using different approaches and techniques of wavelet analysis we analyze variations (oscillations) of galactic cosmic rays, solar spot number, and coronal index of solar activity before ground level enhancements of solar cosmic rays. Obtained results are discussed in frames of recent ideas about periodicity phenomena in the photosphere, and corona of the Sun, interplanetary medium, and cosmic rays.     

Nuclear composition of 1-to 20-PeV primary cosmic rays according to lateral features of the electron-photon component of all extensive air showers and of extensive air showers accompanying high-energy gamma rays and hadrons in x-ray emulsion chambers at the Tien Shan level

Data from the Tien Shan array Adron on the dependence of the lateral distributions of the electron-photon component (age parameter S) in extensive air showers of cosmic rays on the number of electrons, N _e , which is a quantity that characterizes the primary-nucleus energy E₀, are subjected to a comparative analysis. The distributions in question are given both for all showers and for showers accompanying high-energy gamma rays and hadrons in x-ray emulsion chambers. According to calculations, events associated with the latter are generated predominantly by primary protons, and this makes it possible to assess their role at various values of E₀. The distributions with respect to S suggest a significant fraction of light nuclei, predominantly protons, in the region after the knee in the spectrum for N _e >10⁶, at least up to N _e =5.6×10⁶ (E₀ ～ 10 PeV).     

High-resolution studies of the gamma rays from isomeric states with half-lives of 10 μs - 30ms in nuclei with Z = 63−83

Eight new isomeric states with half-lives in the range 10 μs-30 ms have been identified following bombardment with 17.5 MeV protons of the natural elements and separated isotopes of the elements Eu to Pb. Improved data on 14, previously reported, isomeric states have also been obtained. The energies, half-lives and multipolarities of the gamma rays from these states have been measured using an 8 cm³ Ge(Li) detector. In most cases, level schemes have been constructed, and the spin and parity of the isomeric level and intermediate levels populated in the decay have been determined. A group of hindered E2 transitions have been observed, all of which are retarded by approximately the same degree e.g. 3 × 10⁻³ Weisskopf units. The results are discussed in terms of the Nilsson model and in terms of the selection rules for transitions between Nilsson states.     

一种相控阵天线REV幅相校正方法的仿真与实践

介绍了基于傅里叶分析的旋转矢量算法(REV),并将该算法应用于相控阵天线各单元的初始幅相误差校正,给出了它的仿真分析和工程实现方法。所使用的校正方法区别于以往采用的REV校正方法,利于减少校正天线对相控阵收发信号的影响。仿真结果显示,校正后各通道的相位和幅度与人为设置的相位、幅度只差一个常数,表明方法是有效的;通过实际测试,校正后的天线方向图与近场校正结果逼近,EIRP比校正前提高1.4dB以上,验证了校正方法的功能和性能。