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1.
Summary Anad hoc programme aimed at the search for the optical counterparts of the hard-X-ray/soft-γ-ray sources discovered and/or observed
by the SIGMA telescope is described and some of the results, obtained so far, are presented.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
2.
Summary We describe a method of analysis for the reconstruction of the arrival direction of a high-energy photon impacting on the
top of the atmosphere by using the directions of the particles on the shower front as measured by a ground-based array of
tracking chambers uniformly distributed on a square surface; as an example, an array with enclosed surface of (120×120) m2 has been considered. Estimates on the accuracy of reconstruction are given, after application of the method to computer-simulated
shower directions as a function of the number of ?smapling? detectors and of their accuracy in the measurement of the ?local?
shower direction.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
3.
Summary We briefly discuss the use of existing astronomical data, mainly deep optical observations performed in order to obtain galaxy
and star counts, for the identification of gamma-ray burst sources in particular and of newly discovered X- and gamma-ray
sources in general. Use of such data cannot only reduce the amount of required telescope time but also, in comparison with
present-day observations, allow the search for variability and proper motion of candidate optical counterparts over a time
span of several years.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
4.
F. A. Aharonian 《Il Nuovo Cimento C》1996,19(6):981-990
Summary This paper highlights the status of very high-energy (VHE) gamma-ray astronomy with emphasis on the astrophysical significance
of the discovery of TeV γ-radiation from four celestial objects, Crab Nebula, PSR B1706-44, Mrk 421 and Mrk 501, detected
at very high confidence levels using the atmospheric Cherenkov imaging technique.
Paper presented at the Special Session on ground-based gamma-ray astronomy of the XXIV International Cosmic-Ray Conference,
Rome, August 28–September 8, 1995. 相似文献
5.
V. G. Sinitsyna 《Il Nuovo Cimento C》1996,19(6):965-970
Summary A new Cherenkov imaging telescope SHALON equipped with a very high-definition camera (144 pixels, imaging 7.20×7.20) takes data since 1993 at a mountain altitude of 3338 m. We discuss some results of the observations of the indicated gamma-ray
sources and the discrimination methods between gamma-rays and protons. Selection of showers produced by gamma-quanta from
a background of showers produced by protons has been made according to the following criteria: 1) alpha<200; 2) length/width>1.6 for γ; 3) Cherenkov light intensity in pixels with max light to the light in the light pixels near around
is >0.2 for γ and <0.6 for p; 4) Cherenkov light intensity in pixels with max light to all light in imaging excluding in centre
is >0.8 for γ and <0.8 for p; 5) distance for γ is <3.5 pixels.I
Crab=(0.95±0.18)·10−12 cm−2c−1.I
Mark421=(0.98±0.36)·10−12 cm−2c−1.
Paper presented at the Special Session on ground-based gamma-ray astronomy of the XXIV International Cosmic-Ray Conference,
Rome, August 28–September 8, 1995. 相似文献
6.
E. Caroli G. Baldazzi G. Di Cocco A. Donati W. Dusi G. Malaguti J. B. Stephen M. Trifoglio 《Il Nuovo Cimento C》1993,16(6):727-733
Summary Our knowledge of the hard-X- and soft-γ-ray sky obtained in the last few years by satellite missions and in particular by
SIGMA has demonstrated that in this energy range the next generation of instruments must provide both good imaging over a
large field of view and fine spectroscopy over a large energy band. Currently, a possible answer to these requirements may
be offered by instruments based on position-sensitive detectors (PSD) constructed of modular arrays of CdTe microspectrometers.
CdTe is a room temperature compound semiconductor with highZ that can be grown in large pure crystals and then cut so as produce small spectroscopic devices. By packing these elements
into arrays, it is possible to construct highly segmented detectors sensitive from ∼ 10 keV to a few MeV. Due to the intrinsic
characteristics of these CdTe microspectrometers, such a PSD would offer fine spatial resolution (down to a few millimetres)
and good spectroscopic performance (E/ΔE>50 forE=500 keV). We present experimental results obtained from CdTe microdetectors with various geometrical shapes and sizes. Furthermore,
we outline a possible coded-mask telescope design based on a CdTe PDS together with an evaluation of the achievable sensitivity.
Paper presented at the 6th Cosmic Physics National Conference, Palermo, 3–7 November 1992. 相似文献
7.
Summary Several AGNs have been proposed as identifications of gamma-ray sources discovered by CGRO. Using the NED database, we show
that these AGNs are not the only extragalactic objects within the error boxes of the sources. Therefore, an in-depth study
is needed on a case-by-case basis to access the most probable counterparts of the gamma-ray sources. A comparison with the
COS-B database is also presented.
28Paper presented at the 6th Cosmic Physics National Conference, Palermo, 3–7 November 1992. 相似文献
8.
B. Sacco G. Agnetta B. Biondo O. Catalano G. Cusumano R. Di Raffaele M. C. Maccarone A. Mangano T. Mineo L. Scarsi et al. 《Il Nuovo Cimento C》1993,16(6):715-720
Summary We present a new γ-ray telescope based on the Limited Streamer Tube technology, used as tracking chambers to detect photons
above 100 MeV. This technique allows to obtain very large sensitive areas (16 m2 in our experiment), together with a good angular resolution for payloads embarcable in high-altitude balloon flights. The
capability to collect a large signal in a short exposure time makes the telescope particularly suitable and competitive with
respect to satellite-based detectors for studying both periodic and random time variabilities on galactic and extragalactic
γ-ray sources.
Paper presented at the 6th Cosmic Physics National Conference, Palermo, 3–7 November 1992. 相似文献
9.
Summary We investigate by a statistical analysis possible correlations among the observational parameters of the γ-ray bursts: the
rise time, the decay time and spectral hardness. We discuss the physical constraints implied by the results.
To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee. 相似文献
10.
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. 相似文献
11.
D. de Martino L. B. F. M. Waters G. M. H. J. Habets A. R. Taylor 《Il Nuovo Cimento C》1990,13(2):471-479
Summary The X-ray variability of transient X-ray binaries is analyzed in terms of the orbital motion of the neutron star, centrifugal
inhibition of accretion and of the variable moss loss rate due to activity of the optical counterpart. The systems A0535+26
and V0332+53 are studied in this respect.
To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee. 相似文献
12.
M. Pamini L. Natalucci D. Dal Fiume F. Frontera E. Costa M. Salvati 《Il Nuovo Cimento C》1990,13(2):337-344
Summary The anticoincidence lateral shields of the high-energy ((15÷200) keV) detector PDS aboard the SAX satellite will be used to
detect celestial gamma-ray bursts. As a gamma-ray burst monitor (GRBM), the shields have a 5σ sensitivity in the (60÷600)
keV nominal energy band about 10−6 erg/cm2, and a capability of determining the burst location to an accuracy of a few tenths of degree to several degrees, depending
on burst direction and strength. The GRBM will be mainly devoted to study the burst time profile with a time resolution down
to 0.5 ms. Its expected performances are evaluated by means of Monte Carlo simulations.
To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee. 相似文献
13.
J. W. Cronin 《Il Nuovo Cimento C》1996,19(6):847-863
Summary The techniques for γ-ray astronomy at energies ≥10 TeV using air shower detectors are discussed. The results, based on a number
of large arrays, are negative, with no point sources being identified. While the contributions to γ-ray astronomy so far have
been only upper limits, these arrays in the future will make significant progress in the understanding of cosmic rays in the
energy range 1013 eV to 1016 eV. Also, contributions to solar physics are being made by observations of shape and time dependence of the shadow of the
Sun as observed in cosmic rays. For the advancement of γ-ray astronomy a greater sensitivity is required in the energy region
of 10 TeV. A number of promising techniques to accomplish a greater sensitivity are discussed. They include the enlargement
of the Tibet array at 4300 meters altitude, the array of open photomultipliers at La Palma (AIROBICC), which views the shower
by the Cherenkov photons produced in the atmosphere, and the instrumentation of a pond at Los Alamos with photomultipliers
(Milagro).
Invited talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995. 相似文献
14.
Summary The sensitivity limits of hard X-ray (> 10 keV) detectors of the current generation are reviewed and the need for a new generation
of instruments based on photon concentration is justified. A hard X-ray concentrator based on Bragg diffraction technique
is proposed. Such an instrument has been simulated with Monte Carlo methods and the expected performances of a particular
configuration are evaluated. The proposed instrument concept is shown to be very promising in the energy range from 10 keV
up to about 80 keV.
To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee. 相似文献
15.
Summary We reveal the fallacies in recent gamma-ray laser schemes that propose to obtain gain by stimulating transitions from a long-lived
upper to a short-lived lower nuclear state. We point out the errors in recent derivations of the stimulated-emission coefficients,
derive the correct formulae, and submit an alternative explanation for an experiment purported to observe stimulated emission
from a long-lived isomer. 相似文献
16.
A Abdel-Hafiez 《Pramana》2006,67(3):457-466
The basic principles of a new version of Fourier transformation is presented. This new version was applied to solve some main
problems such as smoothing, and denoising in gamma spectroscopy. The mathematical procedures were first tested by simulated
data and then by actual experimental data. 相似文献
17.
The existence of cosmic rays of energies exceeding 1020 eV is one of the mysteries of high-energy astrophysics. The spectrum and the high energy to which it extends rule out almost
all suggested source models. The challenges posed by observations to models for the origin of high-energy cosmic rays are
reviewed, and the implications of recent new experimental results are discussed. Large area high-energy cosmic ray detectors
and large volume high-energy neutrino detectors currently under construction may resolve the high-energy cosmic ray puzzle,
and shed light on the identity and physics of the most powerful accelerators in the Universe. 相似文献
18.
Summary The phonon energy spectra of a polycrystalline α-Fe foil were observed at 150 K and 300 K by using the nuclear resonant scattering
of synchrotron radiation. In each spectrum, inelastic scattering was observed at both sides of the elastic peak. It was found
that the ratio of the elastic-scattering component and the asymmetry of the intensity of the side bands observed at 150 K
are larger than those observed at 300 K, respectively. The observed temperature-dependent spectra are in good agreement with
the spectra calculated from the phonon energy distribution function. One of the advantageous features of this method is that
the excitation of only a specific element is possible. Our results show that this method is applicable to the study of lattice
dynamics and opens a new field of the nuclear resonant scattering spectroscopy.
Paper presented at ICAME-95, Rimini, 10–16 September 1995. 相似文献
19.
Summary Two approximate formulae to calculate the eigenvalues of pure quadrupole interaction in M?ssbauer effect studies have been
proposed and the eigenvalue coefficients in the formulae have been given for various excited states and ground states of the
nucleus with different spin. All the eigenvalues of pure quadrupole interaction between both excited state and ground state
of nucleus with spinI=3/2÷9/2 and the electric-field gradient with different asymmetry parameter (η=0÷1.0) have been calculated by these formulae.
The results show that the accuracies in all the calculations are more satisfactory or same in comparison with those obtained
by the formula of Shenoy and Dunlap, especially when the asymmetry parameter of electric-field gradient is larger than 0.8
for the nucleus with spinI=5/2. 相似文献
20.
Summary The hyperfine coupling between spin of electrons ins states and nuclear spin is generally represented by a contact Hamiltonian in which a δ(r) factor appears. Utilizing relativistic equations and considering pointlike nuclei, we show that the δ(r) factor must be replaced by a steeply decreasing radial function of half-maximum width δr=5.8·10−14Z cm. For hydrogen, the correction with respect to the contact Hamiltonian turns out to be small, but for high-Z nuclei this correction acquires substantial importance. For iron 1s states, it rises up to 9.6%. 相似文献