Energy dependence of Ti/Fe ratio in the Galactic cosmic rays measured by the ATIC-2 experiment

Titanium is a rare, secondary nucleus among Galactic cosmic rays. Using the Silicon matrix in the ATIC experiment, Titanium has been separated. The energy dependence of the Ti to Fe flux ratio in the energy region from 5 GeV per nucleon to about 500 GeV per nucleon is presented. The article was translated by the authors.     

On gamma radiation from the magellanic clouds and galactic supernova remnants — Possible antiproton sources in the galaxy

Radiation from the Magellanic Clouds is discussed from the point of view of near future possibilities in observational γ-ray astronomy. The γ-ray fluxes expected according to the metagalactic and galactic theories of the origin of cosmic rays are compared. It is shown that the strongest test of the metagalactic hypothesis will be provided by a determination of the ratio of γ-ray fluxes from SMC and LMC. The γ-ray luminosity of a typical young supernova remnant that can generate sufficient antiprotons is estimated. It is shown that such remnants must have a short phase during which they are very powerful γ-ray emitters.     

基于暗物质粒子探测卫星的宇宙线直接探测研究

高能宇宙线的起源、加速和传播是重大的前沿科学问题,回答该问题需要对宇宙线的能谱、各向异性以及各类高能天体电磁辐射进行精确观测.通过空间粒子探测器对宇宙线各成分能谱的直接测量是研究宇宙线物理问题的重要手段.中国于2015年底发射并持续运行至今的暗物质粒子探测卫星以其大接受度、高能量分辨率等特点,在宇宙线直接探测方面取得了系列重要成果,揭示出质子、氦核、硼碳和硼氧比例等宇宙线能谱的新结构,为理解宇宙线起源等科学问题提供了新的依据.介绍了暗物质粒子探测卫星的仪器设置、运行状况、科学成果及其物理意义.     

Using the photons from the Crab Nebula seen by GLAST to calibrate MAGIC and the imaging air Cherenkov telescopes

In this article we discuss the possibility of using the observations by GLAST of standard gamma sources, as the Crab Nebula, to calibrate imaging air Cherenkov detectors, MAGIC in particular, and optimise their energy resolution. We show that at around 100 GeV the absolute energy calibration uncertainty of Cherenkov telescopes can be reduced to 10% by means of such cross-calibration procedure.     

Search for short cosmic gamma-ray bursts using data from the APEX and LILAS experiments onboard the Phobos-2 interplanetary spacecraft

A statistical analysis of the spectral and temporal parameters for 546 triggering events on the APEX gamma-ray detector onboard the Phobos-2 spacecraft has revealed a group of 28 events that are probably short cosmic gamma-ray bursts (GRBs). The distribution of the full group of 74 events of the APEX experiment in duration parameter is bimodal in shape, which is in good agreement with the bimodal shape of the BATSE GRB distribution. A search for the detected group of short events using data from the LILAS X-ray and soft gamma-ray detector onboard the same spacecraft has yielded no positive result. A comparison of the APEX and LILAS data has led us to conclude that the short GRBs have a significantly reduced soft gamma-ray flux at energies <100 keV relative to the power law dN/dE=CE^?α with the average index α=2.62.     

Searches for the sources of cosmic rays with energies (1–4)×1017 eV using the Yakutsk EAS array

We analyze the arrival directions of cosmic rays with energies E ₀≈(1–4)×10¹⁷ eV and zenith angles θ≤53≤ detected with the Yakutsk extensive air shower (EAS) array during 1974–2001. We show that ～10% of them form many clusters correlated with the Supergalactic plane. Enhanced particle fluxes arrive from the Supergalactic plane and the regions that are symmetrically adjacent to it at angles ±b _SG ≈ 6°.5. The relatively high concentrations of clusters of galaxies and quasars that bear a relationship to the large-scale structure of the Universe are observed in these regions.     

Cosmic rays at ultra high energies (Neutrinos!)

Resonant photo-pion production with the cosmic microwave background predicts a suppression of extragalactic protons above the famous Greisen–Zatsepin–Kuzmin cutoff at about E_GZK ≈ 5 × 10¹⁰ GeV. Current cosmic ray data measured by the AGASA and HiRes Collaborations do not unambiguously confirm the GZK cutoff and leave a window for speculations about the origin and chemical composition of the highest energy cosmic rays. In this work we analyze the possibility of strongly interacting neutrino primaries and derive model-independent quantitative requirements on the neutrino–nucleon inelastic cross section for a viable explanation of the cosmic ray data. Search results on weakly interacting cosmic particles from the AGASA and RICE experiments are taken into account simultaneously. Using a flexible parameterization of the inelastic neutrino–nucleon cross section we find that a combined fit of the data does not favor the Standard Model neutrino–nucleon inelastic cross section, but requires, at 90% confidence level, a steep increase within one energy decade around E_GZK by four orders of magnitude. We illustrate such an enhancement within some extensions of the Standard Model. The impact of new cosmic ray data or cosmic neutrino search results on this scenario, notably from the Pierre Auger Observatory soon, can be immediately evaluated within our approach.     

Simulations of Galactic Cosmic Ray impacts onto the Herschel/PACS photoconductor arrays with Geant4 code

We present results of simulations performed with the Geant4 software code of the effects of Galactic Cosmic Ray impacts on the photoconductor arrays of the PACS instrument. This instrument is part of the ESA-Herschel payload, which will be launched in 2008 and will operate at the Lagrangian L2 point of the Sun-Earth system. Both the Satellite plus the cryostat (the shield) and the detector act as source of secondary events, affecting the detector performance. Secondary event rates originated within the detector and from the shield are of comparable intensity. The impacts deposit energy on each photoconductor pixel but do not affect the behaviour of nearby pixels. These latter are hit with a probability always lower than 7%. The energy deposited produces a spike which can be hundreds times larger than the noise. We then compare our simulations with proton irradiation tests carried out for one of the detector modules and follow the detector behaviour under ‘real’ conditions.     

Introduction to Volume 323 (6) – Proceedings of the Special Colloquium “European Astronomy in the 20th Century” at the Joint European and National Astronomical Meeting (JENAM) for 2001

This issue of AN contains the proceedings of the Special Colloquium “European Astronomy in the 20th Century”, which formed part of the JENAM (2001) conference in Munich, Germany. Subjects covered are the history of γ‐ray and radio astronomy, extragalactic research and compact objects, new media, southern observatories and ESO, as well as some archaeoastronomical questions. Some biographic sketches of individual European astronomers are also given.     

Small-scale anisotropy of cosmic rays with energies above 3×1018 eV based on data from the Yakutsk EAS facility

We analyze the directions of the arrival of cosmic rays with energies E ₀≥3×10¹⁸ eV and zenith angles θ≤45° recorded by the Yakutsk extensive air shower (EAS) facility during 1974–2000. They are shown to have a small-scale structure with scale sizes of 5°–10°. Enhanced particle fluxes compared to the expected levels for random distributions at (4–5)σ are observed from the Galactic and Supergalactic planes.     

TM65 m射电望远镜低频段系统噪声温度测试和分析

首先介绍了天马65 m射电望远镜(简称TM65 m)接收系统,包括L、S、C、X 4个频段各部分的噪声指标.然后对系统噪声温度的几种测试方法进行了讨论;对影响系统噪声温度测量的若干关键因素进行了分析,包括非线性误差、馈源网络插入损耗和失配误差等.采用Y因子法对试验室的噪声源定标值进行了校核,校核后偏差达到0.2 K左右.最后给出了TM65 m 4个低频段系统噪声温度的实测结果,并进行了分析.     

Phenomenological explanation for the shape of the spectrum of cosmic rays with energies <Emphasis Type="Italic">E</Emphasis> > 10 GeV

Assuming that the energy gain by cosmic-ray (CR) particles is a stochastic process with stationary increments, we derive expressions for the shape of their energy spectrum up to energies E ～ 10¹⁸ eV. In the ultrarelativistic case under study, the energy is proportional to the momentum, whose time derivative is the force. According to the Fermi mechanism, a particle accelerates when it passes through a system of shock waves produced by supernova explosions. Since these random forces act on time scales much shorter than the particle lifetime, we assume them to be delta-correlated in time. In this case, due to the linear energy-momentum relationship, the mean square of the energy (increments) is proportional to the differential scale τ(E) ～ Eτ(≥E), where τ (≥E) is the cumulative time it takes for a particle to gain an energy ≥E. The probability of finding a particle with energy ≥E somewhere in the system is inversely proportional to the time it takes to gain the energy E. To estimate an upper limit for the space number density of CR particles, we use estimates of the CR volume energy density, a quantity known for our Galaxy. It is taken to be constant in the range 10 GeV ≤ E ≤ 3 × 10⁶ GeV, where the index of the energy spectrum was found to be ?8/3 ≈ ?2.67 against its empirical value of ?2.7. In the range 3 × 10⁶ GeV ≤ E < 10⁹ GeV, the upper limit for the volume energy density is estimated by using the results from the previous range to be ?28/9 ≈ ?3.11 against its empirical value of ?3.1. The numerical coefficients in the suggested shapes of the spectrum can be determined by comparison with observational data. Thus, the CR energy spectrumis the result of the random walks of ultrarelativistic particles in energy/momentum space caused by the Fermi mechanism.     

Observations of radio emission from the cosmic gamma-ray burst GRB 030329

We present the radio observations of the afterglow from the intense cosmic gamma-ray burst GRB 030329 performed with the radio telescopes of the Institute of Applied Astronomy, Russian Academy of Sciences, at the Svetloe (λ=3.5 cm) and Zelenchuk (λ=6 cm) Observatories. The difference between the fluxes measured in two different polarization modes suggests the existence of a circular polarization in the radio afterglow from GRB 030329. However, since the measurement errors of the fluxes with different circular polarizations are large, we cannot draw a firm conclusion about its detection; we can only set an upper limit on its value. An analysis of the possible generation mechanisms for the circular polarization of the relativistic jet suggests that there is a helical magnetic field in the jet. The existence of significant flux densities at various wavelengths during a long (≥10 days) period leads us to conclude that the hydrodynamic evolution of the relativistic bow shock takes place in the stellar wind, not in the interstellar medium. We have estimated the total GRB energy (E=10⁵¹ erg) (under the assumption of isotropic radiation) and the plasma density of the stellar wind from the presupernova (n=3 cm^?3). The magnetic-field strength in the relativistic jet can be estimated as B≈100 G.     

Study of dispersion of mass distribution of ultra-high energy cosmic rays using a surface array of muon and electromagnetic detectors

We consider a hypothetical observatory of ultra-high energy cosmic rays consisting of two surface detector arrays that measure independently electromagnetic and muon signals induced by air showers. Using the constant intensity cut method, sets of events ordered according to each of both signal sizes are compared giving the number of matched events. Based on its dependence on the zenith angle, a parameter sensitive to the dispersion of the distribution of the logarithmic mass of cosmic rays is introduced. The results obtained using two post-LHC models of hadronic interactions are very similar and indicate a weak dependence on details of these interactions.     

Recombination dynamics of primordial hydrogen and helium (He I) in the universe

We calculated the ionization fraction for hydrogen and helium (He I) as a function of the redshift z by including the two-photon decays of high hydrogen and parahelium levels and the radiative transfer in the helium 2³P₁ ? 1¹S₀ intercombination line. We show that this yields corrections of no more than a few percent to the ionization fraction for hydrogen and speeds up significantly the recombination for helium compared to the recent works by Seager et al. (1999, 2000), in which these effects were disregarded.     

Acceleration of anomalous cosmic rays at the heliospheric termination shock

Astronomy Letters - The acceleration of anomalous cosmic rays (ACRs) at the heliospheric termination shock and their influence on the shock structure and location are analyzed in terms of a...     

Simulation Study on High Energy Cosmic Electron Detection by Shower Image

Many projects have recently been carried out and proposed for observing high energy electrons since it is realized that cosmic ray electrons are very important when studying the dark matter particles and the acceleration mechanism of cosmic rays. An imaging calorimeter, BETS （Balloon-borne Electron Telescope with Scintillator fiber）, has been developed for this purpose. Using pattern analysis of the shower development, the electrons can be selected from those primary cosmic ray proton events with flux heights one-tenth that of the electrons. The Monte-Carlo simulation is indispensable for the instrument design, the signal trigger and the data analysis. We present different shower simulation codes and compare the simulation results with the beam test and the flight data of BETS. We conclude that the code FLUKA2002 gives the most consistent results with the experimental data.     

Search for signatures of magnetically-induced alignment in the arrival directions measured by the Pierre Auger Observatory

We present the results of an analysis of data recorded at the Pierre Auger Observatory in which we search for groups of directionally-aligned events (or ‘multiplets’) which exhibit a correlation between arrival direction and the inverse of the energy. These signatures are expected from sets of events coming from the same source after having been deflected by intervening coherent magnetic fields. The observation of several events from the same source would open the possibility to accurately reconstruct the position of the source and also measure the integral of the component of the magnetic field orthogonal to the trajectory of the cosmic rays. We describe the largest multiplets found and compute the probability that they appeared by chance from an isotropic distribution. We find no statistically significant evidence for the presence of multiplets arising from magnetic deflections in the present data.     

The MPE X-ray test facility PANTER: Calibration of hard X-ray (15–50 kev) optics

The Max-Planck-Institut für extraterrestrische Physik (MPE) in Garching, Germany, uses its large X-ray beam line facility PANTER for testing X-ray astronomical instrumentation. A number of telescopes, gratings, filters, and detectors, e.g. for astronomical satellite missions like Exosat, ROSAT, Chandra (LETG), BeppoSAX, SOHO (CDS), XMM-Newton, ABRIXAS, Swift (XRT), have been successfully calibrated in the soft X-ray energy range (< 15keV). Moreover, measurements with mirror test samples for new missions like ROSITA and XEUS have been carried out at PANTER. Here we report on an extension of the energy range, enabling calibrations of hard X-ray optics over the energy range 15–50 keV. Several future X-ray astronomy missions (e.g., Simbol-X, Constellation-X, XEUS) have been proposed, which make use of hard X-ray optics based on multilayer coatings. Such optics are currently being developed by the Osservatorio Astronomico di Brera (OAB), Milano, Italy, and the Harvard-Smithsonian Center for Astrophysics (CfA), Cambridge, MA, USA. These optics have been tested at the PANTER facility with a broad energy band beam (up to 50 keV) using the XMM-Newton EPIC-pn flight spare CCD camera with its good intrinsic energy resolution, and also with monochromatic X-rays between C-K (0.277 keV) and Cu-Kα (8.04 keV). PACS: 95.55.Ka, 95.55.Aq, 41 50.+h, 07.85.Fv