A focal plane detector design for a wide-band Laue-lens telescope     

Ezio Caroli  Natalia Auricchio  Lorenzo Amati  Yuriy Bezsmolnyy  Carl Budtz-JøRgensen  Rui M. Curado da Silva  Filippo Frontera  Alessandro Pisa  Stefano Del Sordo  John B. Stephen  Giulio Ventura 《Experimental Astronomy》2005,20(1-3):341-351

The energy range above 60 keV is important for the study of many open problems in high energy astrophysics such as the role of Inverse Compton with respect to synchrotron or thermal processes in GRBs, non thermal mechanisms in SNR, the study of the high energy cut-offs in AGN spectra, and the detection of nuclear and annihilation lines. Recently the development of high energy Laue lenses with broad energy bandpasses from 60 to 600keV have been proposed for a Hard X ray focusing Telescope (HAXTEL) in order to study the X-ray continuum of celestial sources. The required focal plane detector should have high detection efficiency over the entire operative range, a spatial resolution of about 1mm, an energy resolution of a few keV at 500keV and a sensitivity to linear polarization. We describe a possible configuration of the focal plane detector based on several CdTe/CZT pixelated layers stacked together to achieve the required detection efficiency at high energy. Each layer can operate both as a separate position sensitive detector and polarimeter or work with other layers to increase the overall photopeak efficiency. Each layer has a hexagonal shape in order to minimize the detector surface required to cover the lens field of view. The pixels would have the same geometry so as to provide the best coupling with the lens point spread function and to increase the symmetry for polarimetric studies.  相似文献   

What type was SN 1987A?     

L. A. L. Da Silva 《Astrophysics and Space Science》1990,165(2):255-260

A comparison is made of the light and colour curves of the SN 1987A in the first 280 days with the mean properties of type II supernovae. The conclusion is that even though it has H lines, and was not a typical type II supernova, but a peculiar object from a photometric point of view. The implications for inclusion of SN 1987A in the context of the usual Minkowski-Zwicky classification are explicitly discussed.  相似文献   

Notes on Hori Method for Canonical Systems     

Sandro Da Silva Fernandes 《Celestial Mechanics and Dynamical Astronomy》2003,85(1):67-78

In this paper a slightly different approach is proposed for the process of determining the functions S _m and H _m ^* of the algorithm of the canonical version of Hori method. This process will be referred to as integration theory of the mth order equation of the method. It will be shown that the ordinary differential equation with an auxiliary parameter t ^* as independent variable, introduced through Hori auxiliary system, can be replaced by a partial differential equation in the time t. In this way, the mth order equation of the algorithm assumes a form very similar to the one of other perturbation methods. In virtue of this new approach of the integration theory for Hori method, Lagrange's variational equations introduced by Sessin are revised. As an example, the Duffing equation is solved through this new approach.  相似文献   

Initial phase of chromospheric evaporation in a solar flare     

E. Antonucci  B. R. Dennis  A. H. Gabriel  G. M. Simnett 《Solar physics》1985,96(1):129-142

In this paper we discuss the initial phase of chromospheric evaporation during a solar flare observed with instruments on the Solar Maximum Mission on May 21, 1980 at 20:53 UT. Images of the flaring region taken with the Hard X-Ray Imaging Spectrometer in the energy bands from 3.5 to 8 keV and from 16 to 30 keV show that early in the event both the soft and hard X-ray emissions are localized near the footpoints, while they are weaker from the rest of the flaring loop system. This implies that there is no evidence for heating taking place at the top of the loops, but energy is deposited mainly at their base. The spectral analysis of the soft X-ray emission detected with the Bent Crystal Spectrometer evidences an initial phase of the flare, before the impulsive increase in hard X-ray emission, during which most of the thermal plasma at 10⁷ K was moving toward the observer with a mean velocity of about 80 km s^-1. At this time the plasma was highly turbulent. In a second phase, in coincidence with the impulsive rise in hard X-ray emission during the major burst, high-velocity (370 km s^-1) upward motions were observed. At this time, soft X-rays were still predominantly emitted near the loop footpoints. The energy deposition in the chromosphere by electrons accelerated in the flare region to energies above 25 keV, at the onset of the high-velocity upflows, was of the order of 4 × 10¹⁰ erg s^-1 cm^-2. These observations provide further support for interpreting the plasma upflows as the mechanism responsible for the formation of the soft X-ray flare, identified with chromospheric evaporation. Early in the flare soft X-rays are mainly from evaporating material close to the footpoints, while the magnetically confined coronal region is at lower density. The site where upflows originate is identified with the base of the loop system. Moreover, we can conclude that evaporation occurred in two regimes: an initial slow evaporation, observed as a motion of most of the thermal plasma, followed by a high-speed evaporation lasting as long as the soft X-ray emission of the flare was increasing, that is as long as plasma accumulation was observed in corona.  相似文献   

Baryon loading and the Weibel instability in gamma-ray bursts     

M. Fiore  L. O. Silva  C. Ren  M. A. Tzoufras  W. B. Mori 《Monthly notices of the Royal Astronomical Society》2006,372(4):1851-1855

The dynamics of two counter-streaming electron–positron–ion unmagnetized plasma shells with zero net charge is analysed in the context of magnetic field generation in gamma-ray burst internal shocks due to the Weibel instability. The effects of large thermal motion of plasma particles, arbitrary mixture of plasma species and space charge effects are taken into account. We show that, although thermal effects slow down the instability, baryon loading leads to a non-negligible growth rate even for large temperatures and different shell velocities, thus guaranteeing the robustness and the occurrence of the Weibel instability for a wide range of scenarios.  相似文献   

Observation of, and temporal variations in, solar p-mode multiplet frequency asymmetries at  ℓ= 2      

W. J. Chaplin  Y. Elsworth  G. R. Isaak  B. A. Miller  R. New  S. Thiery  P. Boumier  A. H. Gabriel 《Monthly notices of the Royal Astronomical Society》2003,343(1):343-352

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The Common Origin of the High Inclination TNO's     

Gomes  Rodney 《Earth, Moon, and Planets》2003,92(1-4):29-42

Numerical integrations of the four major planets orbits inside a primordialplanetesimals disk show that a fraction of Neptune primordial scatteredobjects are deposited into the classical Kuiper Belt at Solar System age. Theseobjects exhibit inclinations as high as 40° and can account forpresent high inclinations population in the classical Kuiper Belt. The samemechanism can also originate high perihelion scattered objects like 2000 CR₁₀₅. The process that in the end produced such objects can be divided into two phases, a migration phase where nonconservative dynamics acted to producesome stable objects already at 10⁸ years and a nonmigrating phase that helped to establish some other objects as stable TNO's. Low inclination CKBO's have inprinciple an origin through the resonance sweeping process, although someresults from numerical integrations at least suggest a possible origin also fromthe primordial Neptune scattered population.  相似文献   

Integrated resource management     

Martin Florin  Erhard Gabriel 《GeoJournal》1991,25(1):109-113

Food, energy and mineral resources appeared to be available in limitless quantities. The accelerated growth in global population during recent centuries brought about a new situation. We reached the resource limits of Spaceship Earth. This, along with the dawning awareness of the extent of environmental damage to date, have made it necessary to turn to new attitudes as to the use of renewable and non-renewable resources.IRM (Integrated Resource Management) is proposed as a way to rationally balance the use and conservation of natural resources. A databank based on the Geographic Information System (GIS) concept, bringing together all relevant resources of a nation, is the centerpiece of IRM and will make it possible to establish strategies to optimize the long term use of resources, including all relevant environmental factors.  相似文献   

Geochemistry of S-type granitic rocks from the reversely zoned Castelo Branco pluton (central Portugal)     

I.M.H.R. Antunes  A.M.R. Neiva  M.M.V.G. Silva  F. Corfu 《Lithos》2008,103(3-4):445-465

The zoned pluton from Castelo Branco consists of Variscan peraluminous S-type granitic rocks. A muscovite>biotite granite in the pluton's core is surrounded successively by biotite>muscovite granodiorite, porphyritic biotite>muscovite granodiorite grading to biotite=muscovite granite, and finally by muscovite>biotite granite. ID-TIMS U–Pb ages for zircon and monazite indicate that all phases of the pluton formed at 310 ± 1 Ma. Whole-rock analyses show slight variation in ⁸⁷Sr/⁸⁶Sr_310 Ma between 0.708 and 0.712, Nd_310 Ma values between − 1 and − 4 and δ¹⁸O values between 12.2 and 13.6. These geological, mineralogical, geochemical and isotopic data indicate a crustal origin of the suite, probably from partial melting of heterogeneous Early Paleozoic pelitic country rock. In detail there is evidence for derivation from different sources, but also fractional crystallization linking some of internal plutonic phases. Least-squares analysis of major elements and modelling of trace elements indicate that the porphyritic granodiorite and biotite=muscovite granite were derived from the granodiorite magma by fractional crystallization of plagioclase, quartz, biotite and ilmenite. By contrast variation diagrams of major and trace elements in biotite and muscovite, the behaviours of Ba in microcline and whole-rock δ¹⁸O, the REE patterns of rocks and isotopic data indicate that both muscovite-dominant granites were probably originated by two distinct pulses of granite magma.  相似文献   

Impact of lightning on organic matter-rich soils: influence of soil grain size and organic matter content on underground fires     

Vittorio Zanon  Fátima Viveiros  Catarina Silva  Ana Rita Hipólito  Teresa Ferreira 《Natural Hazards》2008,45(1):19-31

A detailed study was carried out on a piece of land that had been struck by lightning during the violent rainstorm that raged over the Island of S?o Miguel (Azores Archipelago) in late October 2006. Temperature and gas measurements (CO₂, CO, H₂S and CH₄) were performed in four study trenches, dug in an area of ∼3 m², where an underground fire had been initiated by the impact with a lightning stroke, followed by the emission of a column of gases and smoke. The soil under study was originally a well-pedogenized about 80 cm thick bed, made of volcanic clayey to silty tephra fallouts and contained 5.5–9.7% of organic matter. The underground fire was monitored for one week and revealed a peak release of 404 ppm CO and 3.4% CO₂ originating from a horizon located about 45 cm under the soil surface. Measurements of temperature, performed one week after the impact, indicated a maximum value of 326°C inside the soil, while 516.5°C were measured on the surface of a lava block interred about 20 cm under the surface. Subsequently, a stratigraphic and sedimentologic study proved the role of the grain-size of the soil and of the organic matter content of the different horizons of the impact area, in determining the ratio between anoxic/oxidised combustion conditions and in the progress of the process itself. It was also noticed that combustion was not total all over in the soil bed and that the process had slightly migrated toward SW during the observation period. The combustion process went on for about ten days, in spite of several other violent rainstorms, until it was artificially extinguished through the excavations made to obtain study trenches. This particular circumstance evidenced the potential natural hazard represented by this kind of atmospheric event, especially in a land where the volcanic nature of the soil may easily mislead inexperienced observers and, consequently, delay proper action.  相似文献