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1.
T. Kifune 《Il Nuovo Cimento C》1996,19(6):953-957
Summary The ground-based gamma-ray astronomy has its coming of age currently with 4 sources detected at high significance levels,
after experiencing about 30 years history. The energetic gamma rays provide direct means for uncovering higher-energy non-thermal
phenomena at various celestial objects. We need more data with improved sensitivities, and multitudes of such efforts are
now under way.
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
2.
V. Sch?nfelder 《Il Nuovo Cimento C》1996,19(6):805-819
Summary Astronomy is performed nowadays over the entire range of the electromagnetic spectrum from radio to gamma-ray energies. From
the so-called ?New Astronomies? which are performed outside the optical window, we have learnt that each spectral range provides
specific information, which cannot be obtained by other means. This is also true for gamma-ray astronomy. Gamma radiation
represents the most energetic part of the electromagnetic spectrum. Therefore, it provides information about the most energetic
processes and phenomena in the Universe. The energy band of space-borne gamma-ray astronomy extends over more than five orders,
of magnitude—similar to the band from the radio to optical range. It is thus not surprising that a variety of different objects
and phenomena can be studied. Gamma-ray astronomy at present is experiencing a golden age. This is mainly due to the many
exciting results from NASA's Compton Gamma Ray Observatory, which has been in orbit for more than 4.5 years. The broad interest
in this mission is remarkable. Perhaps its most important achievement is that gamma-ray astronomy has now become an integrated
part of astronomy and astrophysics. One has recognized that there are objects in the Universe like radio pulsars and quasars,
which do have their peak luminosities at gamma-ray energies. It is practically impossible to understand these objects without
knowing their gamma-ray properties.
Invited talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995. 相似文献
3.
V. A. Dogiel 《Il Nuovo Cimento C》1996,19(5):671-699
Summary This paper is devoted to problems of gamma-ray astronomy in the energy range <1011 eV. Measurements of spectra and fluxes in this energy range are carried out by means of direct observations from space. Most
of the discussed results have been performed with the four telescopes of the Compton Gamma-Ray Observatory. The main topics
of the paper are: diffuse galactic gamma-ray emission, point-like galactic gamma-ray sources, gamma-ray line emission, gamma-ray
bursts and active galactic nuclei.
Rapporteur talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September, 8, 1995. 相似文献
4.
M. F. Cawley 《Il Nuovo Cimento C》1996,19(6):959-963
Summary Following a brief history of the atmospheric Cherenkov imaging technique and a summary of the current status of the field,
we describe some of the potential developments of the method over the next few years. Due to constraints of space, we shall
confine the discussion to single stand-alone telescopes—stereo imaging will not be discussed.
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.
《Il Nuovo Cimento C》1996,19(6):971-979
Summary This paper describes the development of new ground-based gammaray detectors to explore the energy region between 20 and 200
GeV. This region in energy is interesting because it is currently unexplored by any experiment. The proposed detectors use
the atmospheric Cherenkov technique, in which Cherenkov radiation produced in the gamma-ray air showers is detected using
mirrors and light-sensitive devices. The important feature of the proposed experiments is the use of large mirror collection
areas, which should allow for a significant improvement (i.e. reduction) in energy threshold over existing experiments. Large mirror areas are available for relatively low cost at central
tower solar power plants, and there are two groups developing gamma-ray experiments using solar heliostat arrays. This paper
summarizes the progress in the design of experiments using this novel approach.
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
7.
A. M. Hillas 《Il Nuovo Cimento C》1996,19(5):701-712
Summary This report covers developments in the field of gamma-ray astronomy, essentially in the energy range 300 GeV to 300 TeV, reported
at the XXIV International Cosmic-Ray Conference in Rome in 1995. Highlights which receive the main attention are the failure
of several experiments to detect TeV photons from several supernova remnants at the level predicted on current models of shock
acceleration of cosmic-ray protons, and the detection of a rapidly variable flaring output of TeV photons from two BL Lac
objects (Markarian 421 and Markarian 501). Although techniques are now maturing to the extent that different measurements
of the flux and spectrum from the Crab Nebula are now converging, unresolved differences remain over the existence of TeV
pulses from certain pulsars. However, one well-supported instance of very intense pulsation for an hour from AE Aquarii was
presented. The Vela Pulsar was reported as a steady source.
Rapporteur talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995. 相似文献
8.
G. Navarra 《Il Nuovo Cimento C》1995,18(2):183-193
Summary We discuss some recent results obtained in the fields of VHE-UHE gamma-ray astronomy, search for gamma-ray bursts at high
energies, and UHE neutrino astronomy by means of Extensive Air Showers (EAS) arrays. The technical achievements and future
possibilities are outlined. 相似文献
9.
G. B. Gelmini O. E. Kalashev D. V. Semikoz 《Journal of Experimental and Theoretical Physics》2008,106(6):1061-1082
We calculate the flux of “GZK photons,” namely, the flux of ultra-high-energy cosmic rays (UHECRs) consisting of photons produced
by extragalactic nucleons through the resonant photoproduction of pions, the so-called GZK effect. We show that for primary
nucleons, the GZK-photon fraction of the total UHECR flux is between 10−4 and 10–2 above 1019 eV and up to the order of 0.1 above 1020 eV. The GZK-photon flux depends on the assumed UHECR spectrum, the slope of the nucleon flux at the source, and the distribution
of sources and intervening backgrounds. Detection of this photon flux would open the way for UHECR gamma-ray astronomy. Detection
of a larger photon flux would imply the emission of photons at the source or new physics. We compare the photon fractions
expected for GZK photons and the minimal fractions predicted by top-down models. We find that the photon fraction above 1019 eV is a crucial test for top-down models.
The text was submitted by the authors in English. 相似文献
10.
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
11.
We present a simplified formulae system describing the polarization properties of the quantum cyclotron radiation by a nonrelativistic thermal electron in a very strong magnetic field. In this system, each of the derived quantities, including the Einstein coefficients, the absorption cross sections, and scattering cross sections, as well as the absorption coefficients by plasma, is divided into the perpendicularly and parallelly polarized components. The results, especially the absorption and scattering cross sections of resonant frequency photons, are potentially important in x-ray and γ-ray astronomy, particularly in the study of gamma-ray bursts and pulsars. 相似文献
12.
A high-pressure parallel-grid gas scintillation proportional counter for high-energy X-ray astronomy
F. Celi R. di Raffaele G. Gerardi G. Manzo O. Mistretta S. Re L. Scarsi 《Il Nuovo Cimento C》1984,7(6):559-567
Summary We present preliminary results on a new detector for X-ray astronomy sensitive in the energy range from 3 to 120 keV. The
detector can be implemented either as a narrow-field instrument (∼1 degree field of view) or as wide field camera (30×30 degree
field of view). This detector with its large area, good energy resolution and background rejection represents a valid option
to the present generation of instruments for high-energy X-ray astronomy.
Paper presented at the 2° Convegno Nazionale di Fisica Cosmica, held at L'Aquila, 29 May–2 June 1984. 相似文献
13.
Summary The present observational and instrumental status of hard-X-ray astronomy ((10÷200) keV) is discussed. The relevance of observations
in this energy range is stressed and a few examples of unsolved observational problems in galactic and in extragalactic astronomy
are discussed. In these examples we focus on the possibility to solve the problems with observations using detectors of the
current generation. In this framework, the performances of the most sensitive hard-X-ray detectors are discussed with particular
emphasis on the control of systematic errors. Quite simple but unavoidable considerations on limits of the present generation
of hard-X-ray detectors (supported by results of simple simulations) lead to the conclusion that a decisive breakthrough can
be achieved only using optics with a sufficiently good concentration power. In particular we discuss the feasibility of hard-X-ray
telescopes (with a concentration power ≫1), using either grazing incidence or Bragg diffraction. The use of concentrators
in this energy band can also make feasible polarimetric measures of a substantial sample of X-ray sources, up to now severely
limited by the very low detection efficiency of the devices used in polarimetry.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
14.
We present the first Chandra X-ray observations of the H2O megamaser galaxy Mrk1210 (UGC4203), a Seyfert 2 galaxy at an approximate distance of D ∼ 57.6 Mpc. The Chandra X-ray image, with by far the highest angular resolution (∼1″), displays an unresolved compact core toward the nuclear region
of Mrk1210. Comparisons with the previous X-ray observations in the nuclear emission and the spectral shape indicate a fairly
stable phase between 2001 (BeppoSAX and XMM-Newton) and 2004 (Chandra) after a dramatic variation since 1995 (ASCA). The best-fit model of Chandra X-ray spectrum consists of two components. The soft scattered component can be best fitted by a moderately absorbed power-law
model adding a spectral line at ∼0.9 keV (possibly a Ne-Kα fluorescent line), while the hard nuclear component can be well
reproduced by a heavily absorbed power-law model (N
H ∼ 2×1023 cm−2) with an additional line at ∼6.19 keV (close to the Fe-Kα fluorescent line). The derived absorption-corrected X-ray luminosity
implies that the dramatic variation of spectral properties is caused by significant changes of the absorbing column density
along the line-of-sight, while the intrinsic nuclear X-ray luminosity remains stable. In this case, the absorbers should be
anisotropic and its size can be constrained to be less than 0.0013 pc. In addition, we also estimate the mass of central engine,
the disk radius and the accretion rate of the accretion disk to be 107.12±0.31
M
⊙, ∼1 pc and 0.006, respectively.
Supported by the National Natural Science Foundation of China (Grant No. 10633010) and the Natural Science Foundation of Guangdong
Province, China (Grant No. 8451009101001047)
Recommended by Zhou YouYuan 相似文献
15.
G. Boella A. Della Ventura F. Perotti G. Villa L. Bassani R. C. Butler G. Di Cocco R. E. Baker A. J. Dean D. Ramsden 《Il Nuovo Cimento C》1984,7(6):805-839
Summary The MISO telescope is a gamma-ray detector operating in the (0.1÷20) MeV energy range. This instrument was flown success-fully
from Palestine, Texas (U.S.A.) in May 1977, October 1978, September 1979 and May 1980. During the four flights, the telescope
observed a number of galactic and extragalactic sources. The Crab Nebula was detected in 1980 and its spectrum was measured
up to 2 MeV. Cygnus X-1 was observed in 1979 and 1980 and was found to be in different hard X-ray states on each occasion:
in a superlow state in 1979 and in a low state in 1980. The COS-B high-energy (E>50 MeV) gamma-ray sources CG 135+1 (1978) and CG 195+4 (1978) were also observed by the same instrument. From the region
containing CG 135+1 a 5σ excess was measured in the counting rate of the telescope above 120 keV. No statistically significant
low-energy gamma-ray flux was detected from CG 195+4. The Seyfert galaxies NCG 4151 (1977, 1979, 1980), and MCG 8-11-11 (1979),
the BL LAC object MK 501 (1979) and the ?peculiar? galaxy NGC 1275 (1979) were also searched for gamma-ray emission. The data
on NGC 4151 and MCG 8-11-11 are consistent with power law spectra having photon indices α∼1 in the (0.1÷3) MeV energy range.
Above this energy, the MISO and SAS-2/COS-B measurements require spectral breaks to α≥3. Upper limits were obtained on the
emission from both MK 501 and NGC 1275.
Paper presented at the 2° Convegno Nazionale di Fisica Cosmica, held at L'Aquila, 29 May–2 June 1984. 相似文献
16.
M. Aglietta B. Alessandro F. Arneodo G. Badino L. Bergamasco C. Castagnoli A. Castellina C. Cattadori A. Chiavassa G. Cini et al. 《Il Nuovo Cimento C》1992,15(5):723-733
Summary The EAS-TOP Extensive Air Shower array, on top of the under-ground Gran Sasso Laboratory, is fully operating as a γ-ray astronomy
observatory since the beginning of 1989. After showing the measured angular resolution of the detector, we present the results
obtained from the analysis of 280 days of measurements in 1989–1990, with the purpose of investigating possible emission (d.c.
and sporadic) from the candidate sources in the Northern hemisphere at an energy, >200 TeV.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
17.
Trevor C. Weekes 《Physics in Perspective (PIP)》2010,12(2):146-162
The discovery of the first spiral nebula was a milestone in the history of astronomy, but the initial observations of it are
shrouded in mystery. The discovery came within months of the commissioning of the Third Earl of Rosse’s very large 72-inch
optical telescope at Birr Castle in the center of Ireland. Unfortunately, no observing records have survived, and while there
is no doubt that the observations took place in the spring of 1845, there is some uncertainty as to whom was actually present
when the discovery was made. The construction of the Earl’s telescope (the Leviathan) was a magnificent achievement, since
it was entirely of his design, built with his own funds, and constructed by his own workers who were literally taken “from
the plough” on his estate. The summer of 1845 saw the first appearance of the Irish Potato Famine of 1845–1848, which would
seriously curtail astronomical activity when Lord Rosse’s 72-inch telescope was in prime condition. 相似文献
18.
Oxygen-neon novae form a subset of classical novae events known to freshly synthesize nuclei up to mass number A?40. Because several gamma-ray emitters lie in this mass range, these novae are also interesting candidates for gamma-ray astronomy. The properties of excited states within those nuclei in this mass region play a critical role in determining the resonant (p,γ) reaction rates, themselves, largely unknown for the unstable nuclei. We describe herein a new Doppler shift lifetime facility at the Maier-Leibnitz tandem laboratory, Technische Universität München, with which we will map out important resonant (p,γ) nova reaction rates. 相似文献
19.
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
20.
A. D. Filonenko 《Technical Physics》2008,53(9):1222-1228
Possible reasons for the absence of direct observations of individual events in measuring the super-high-energy particle flux
by the radio astronomy technique are considered. One of these reasons is probably associated with the choice of extremely
high frequencies (∼1.5 GHz) for detecting radio pulses. Calculations show that the radiation intensity attains its peak value
at frequencies ∼500–600 MHz and then sharply decreases so that it becomes three orders of magnitude lower even at a frequency
of ∼1.5 GHz. The effectiveness of particle detection in the range of high (∼600 MHz) and low (∼60 MHz) frequencies is analyzed. 相似文献