共查询到20条相似文献，搜索用时 31 毫秒
1.
A. V. Bogomolov A. P. Ignat’ev K. Kudela S. N. Kuznetsov Yu. I. Logachev O. V. Morozov I. N. Myagkova S. N. Oparin A. A. Pertsov S. I. Svertilov B. Yu. Yushkov 《Astronomy Letters》2003,29(3):199-204
We consider temporal, spectral, and polarization parameters of the hard X-ray and gamma-ray radiation observed during the solar flare of May 20, 2002, in the course of experiments with the SONG and SPR-N instruments onboard the Coronas-F spacecraft. This flare is one of the most intense gamma-ray events among all of the bursts of solar hard electromagnetic radiation detected since the beginning of the Coronas-F operation (since July 31, 2001) and one of the few gamma-ray events observed during solar cycle 23. A simultaneous analysis of the Coronas-F and GOES data on solar thermal X-ray radiation suggests that, apart from heating due to currents of matter in the the flare region, impulsive heating due to the injection of energetic electrons took place during the near-limb flare S21E65 of May 20, 2002. These electrons produced intense hard X-ray and gamma-ray radiation. The spectrum of this radiation extends up to energies ≥7 MeV. Intense gamma-ray lines are virtually unobservable against the background of the nonthermal continuum. The polarization of the hard X-ray (20–100 keV) radiation was estimated to be ≤15–20%. No significant increase in the flux of energetic protons from the flare under consideration was found. At the same time, according to ACE data, the fluxes of energetic electrons in interplanetary space increased shortly (～25 min) after the flare. 相似文献
2.
N. Barrière P. von Ballmoos H. Halloin N. Abrosimov J. M. Alvarez K. Andersen P. Bastie S. Boggs P. Courtois T. Courvoisier M. Harris M. Hernanz J. Isern P. Jean J. Knödlseder G. Skinner B. Smither P. Ubertini G. Vedrenne G. Weidenspointner C. Wunderer 《Experimental Astronomy》2005,20(1-3):269-278
The next generation of instrumentation for nuclear astrophysics will have to achieve a factor of 10–100 improvement in sensitivity over present technologies. With the focusing gamma-ray telescope MAX we take up this challenge: combining unprecedented sensitivity with high spectral and angular resolution, and the capability of measuring the polarization of the incident photons. The feasibility of such a crystal diffraction gamma-ray lens has recently been demonstrated with the prototype lens CLAIRE. MAX is a proposed mission which will make use of satellite formation flight to achieve 86 m focal length, with the Laue lens being carried by one satellite and the detector by the other. In the current design, the Laue diffraction lens of MAX will consist of 13740 copper and germanium (Ge1−x
Si
x
, x ∼ 0.02) crystal tiles arranged on 36 concentric rings. It simultaneously focuses in two energy bands, each centred on one of the main scientific objectives of the mission: the 800–900 keV band is dedicated to the study of nuclear gamma-ray lines from type Ia supernovae (e.g. 56 Co decay line at 847 keV) while the 450–530 keV band focuses on electron-positron annihilation (511 keV emission) from the Galactic centre region with the aim of resolving potential point sources. MAX promises a breakthrough in the study of point sources at gamma-ray energies by combining high narrow-line sensitivity (better than 10−6 cm−2 s−1) and high energy resolution (E/dE ∼ 500). The mission has successfully undergone a pre-phase A study with the French Space Agency CNES, and continues to evolve: new diffracting materials such as bent or composite crystals seem very promising.
PACS: 95.55.Ka, 29.30.Kv, 61.10.-i 相似文献
3.
Polarization evolution accompanying the very early sharp decline of gamma-ray burst X-ray afterglows
Yi-Zhong Fan Dong Xu Da-Ming Wei 《Monthly notices of the Royal Astronomical Society》2008,387(1):92-96
In the synchrotron radiation model, the polarization property depends on both the configuration of the magnetic field and the geometry of the visible emitting region. Some peculiar behaviours in the X-ray afterglows of gamma-ray bursts (GRBs) observed with Swift , such as energetic flares and a plateau followed by a sharp drop, might be highly linearly polarized because the outflows powering these behaviours may be dominated by Poynting flux. The breakdown of the symmetry of the visible emitting region may also be well hidden in the peculiar X-ray data and may give rise to interesting polarization signatures. In this paper, we focus on the polarization accompanying the very early sharp decline of GRB X-ray afterglows. We show that strong polarization evolution is possible in both the high latitude emission model and the dying central engine model, which are used to interpret this sharp X-ray decline. It is thus not easy to efficiently probe the physical origin of the very early X-ray sharp decline with future polarimetry. Strong polarization evolution is also possible in the decline phase of X-ray flares and in the shallow decline phase of X-ray light curves characterized by chromatic X-ray versus optical breaks. A detector such as the X-ray Telescope (XRT), but with polarization capability, on board a satellite like Swift would be suitable for testing our predictions. 相似文献
4.
A. Smith R. W. Atkins S. Bradbury O. Celik Y. C. K. Chow P. Cogan C. Dowdall S. J. Fegan P. Fortin D. Gall G. H. Gillanders J. Grube K. J. Gutierrez T. A. Hall D. Hanna J. Holder D. Horan S. B. Hughes T. B. Humensky I. Jung P. Kaaret G. Kenny M. Kertzman D. B. Kieda A. Konopelko H. Krawczynski F. Krennrich M. J. Lang S. Le Bohec G. Maier J. Millis P. Moriarty R. A. Ong J. S. Perkins K. Ragan G. H. Sembroski J. A. Toner L. Valcarcel V. V. Vassiliev R. G. Wagner S. P. Wakely T. C. Weekes R. J. White D. A. Williams 《Astrophysics and Space Science》2007,309(1-4):299-303
In this paper we present the results of the past two years observations on the galactic microquasar LS I +61 303 with the
Whipple 10 m gamma-ray telescope. The recent MAGIC detection of the source between 200 GeV and 4 TeV suggests that the source
is periodic with very high energy (VHE) gamma-ray emission linked to its orbital cycle. The entire 50-hour data set obtained
with Whipple from 2004 to 2006 was analyzed with no reliable detection resulting. The upper limits obtained in the 2005–2006
season covered several of the same epochs as the MAGIC Telescope detections, albeit with lower sensitivity. Upper limits are
placed on emission during the orbital phases of 0→0.1 and 0.8→1, phases which are not included in the MAGIC data set.
相似文献
5.
Niels Lund 《Experimental Astronomy》1992,2(5):259-273
A study is presented on the feasibility of using Bragg diffraction from crystals to focus soft gamma-rays in the energy range up to 2 MeV. For astrophysics this band contains several very interesting gamma-ray lines from novae, supernovae and X- and gamma-ray transients.The study concludes that, in the energy range between 300 and 1300 keV, a Bragg-telescope with a focal length of about 50 meters could achieve a sensitivity for point sources which is between 5 and 10 times better than that currently expected for the ESA/NASA INTEGRAL-mission/1/. In addition, the angular resolution of the Bragg telescope would also be an order of magnitude better. Despite the large physical dimensions of the telescope, its feasibility does not seem out of reach. The requirements do not go appreciably beyond those of other scientific projects which have been studied and found technically feasible by ESA and NASA /2, 3/. The Bragg-telescope therefore may become the logical next step in soft gamma-ray astronomy following a sensitive survey project like INTEGRAL. 相似文献
6.
伽马射线作为宇宙中极端事件的独特探针,探测伽马射线是人们了解宇宙构成、星体演化和宇宙线起源等的重要途经.伽马天文涉及了宇宙中的各种前沿科学问题并且观测所需能谱跨度极宽(102 keV–102 TeV),针对不同的科学目标和细分谱段,必须利用不同的伽马望远镜探测技术.总结了空间和地面的共5大类伽马射线观测技术,分别是编码孔径望远镜、康普顿望远镜、电子对望远镜、成像大气切伦科夫望远镜和广延大气簇射阵列;回顾了70 yr来在观测设备和技术进步的推动下伽马射线天文学领域的巨大进展,其中包含高能和甚高能谱段取得的大量成就,中低能段由于已有观测任务有限以及灵敏度低,超高能和极高能段由于观测难度大、起步时间晚,数据和成果相对其他谱段产出较少;展望了未来已经规划的伽马望远镜任务、能力及预期科学产出,其中,中低能段空间望远镜增强型ASTROGAM望远镜(e-ASTROGAM)、全天区中能伽马射线观测站(AMEGO)和甚高能段地面望远镜阵列高海拔宇宙线观测站(LHAASO)、切伦科夫望远镜阵列(CTA),由于灵敏度较同谱段已有任务灵敏度有大幅提升,极有可能在20 yr内从不同角度再度扩展人类对伽马宇宙的认知. 相似文献
7.
J. Knödlseder 《Experimental Astronomy》2005,20(1-3):3-13
Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe. While at lower wavebands the observed emission is generally dominated by thermal processes, the gamma-ray sky provides us with a view on the non-thermal Universe. Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood, and nuclear reactions are synthesizing the basic constituents of our world. Cosmic accelerators and cosmic explosions are the major science themes that are addressed in the gamma-ray regime.With the INTEGRAL observatory, ESA has provided a unique tool to the astronomical community revealing hundreds of sources, new classes of objects, extraordinary views of antimatter annihilation in our Galaxy, and fingerprints of recent nucleosynthesis processes. While INTEGRAL provides the global overview over the soft gamma-ray sky, there is a growing need to perform deeper, more focused investigations of gamma-ray sources. In soft X-rays a comparable step was taken going from the Einstein and the EXOSAT satellites to the Chandra and XMM/Newton observatories. Technological advances in the past years in the domain of gamma-ray focusing using Laue diffraction and multilayer-coated mirror techniques have paved the way towards a gamma-ray mission, providing major improvements compared to past missions regarding sensitivity and angular resolution. Such a future Gamma-Ray Imager will allow to study particle acceleration processes and explosion physics in unprecedented detail, providing essential clues on the innermost nature of the most violent and most energetic processes in the Universe. 相似文献
8.
Lupin Chun-Che Lin Hsiang-Kuang Chang 《Monthly notices of the Royal Astronomical Society》2008,387(2):729-734
A periodicity search of gamma-ray data is usually difficult because of the small number of detected photons. A periodicity in the timing signal at other energy bands from the counterpart to the gamma-ray source may help to establish the periodicity in the gamma-ray emission and strengthen the identification of the source in different energy bands. However, it may still be difficult to find the period directly from X-ray data because of limited exposure. We have developed a procedure, by cross-checking two X-ray data sets, to find candidate periods for X-ray sources that are possible counterparts to gamma-ray pulsar candidates. Here, we report on the results of this method obtained with all the currently available X-ray data of eight X-ray sources. Some attractive periodicity features were found. These candidate periods can serve as the target periods for a future search when new data become available, so that a blind search with a huge number of trials can be avoided. 相似文献
9.
Peter von Ballmoos Hubert Halloin Jean Evrard Gerry Skinner Nikolai Abrosimov Jose Alvarez Pierre Bastie Bernard Hamelin Margarida Hernanz Pierre Jean Jürgen Knödlseder Bob Smither 《Experimental Astronomy》2005,20(1-3):253-267
The objective of the R&D project CLAIRE was to prove the principle of a gamma-ray lens for nuclear astrophysics. CLAIRE's Laue diffraction lens has a diameter of 45 cm and a focal length of 277 cm; 556 germanium-silicon crystals are tuned to focus 170 keV photons onto a 1.5 cm diameter focal spot. Laboratory measurements of the individual crystals and the entire lens have been used to validate a numerical model that we use to estimate the lens performance for a source at infinity. During a stratospheric balloon flight on 2001 June 14, CLAIRE was directed at the Crab nebula by a pointing system able to stabilize the lens to within a few arcseconds of the target. In 72 min of valid pointing time, 33 photons from the Crab were detected in the 3 keV bandpass of the lens: CLAIRE's first light! The performance of CLAIRE's gamma-ray lens, namely the peak reflectivity for a polychromatic source (9±1%), has been confirmed by ground data obtained on a 205 meter long test range. CLAIRE's measured performance validates the principle of a Laue lens for nuclear astrophysics, opening the way for a space-borne gamma-ray lens telescope that will achieve one to two orders of magnitude improvement in sensitivity over present technologies. 相似文献
10.
O. Terekhov D. Denissenko R. Sunyaev S. Sazonov C. Barat J. -P. Dezalay G. Vedrenne N. Lund A. J. Castro-Tirado S. Brandt 《Astrophysics and Space Science》1995,231(1-2):31-34
The GRANAT observatory was launched into a high apogee orbit on 1 December, 1989. Three instruments onboard GRANAT - PHEBUS, WATCH and SIGMA are able to detect gamma-ray bursts in a very broad energy range from 6 keV up to 100 MeV. Over 250 gamma-ray bursts were detected. We discuss the results of the observations of the time histories and spectral evolution of the detected events provided by the different instruments in different energy ranges. Short Gamma-Ray Bursts (< 2 s) have 10 ms structure in their time histories. They have harder energy spectra than the long (> 2 s) events. Evidence of the existence of four differently behaving componenents in gamma-ray burst spectra is discussed. Statistical properties of the gamma-ray burst sources based on the 5 years of observations with ( 10–6 erg/cm2) sensitivity as well as the results of high sensitivity ( 10–8 erg/cm2) search for Gamma-Ray Bursts within the SIGMA telescope field of view are reviewed. 相似文献
11.
Swift卫星的X射线望远镜观测揭示部分伽玛暴的早期余辉光变曲线有一个缓慢衰减的成分,而相当一部分却没有这样的成分.研究比较这两种暴的观测性质发现两类暴的持续时间、伽玛辐射总流量、谱指数、谱硬度比峰值能量等物理量均没有显著差异.然而有该成分的那些伽玛暴谱比较软、早期X射线余辉比较弱、伽玛射线辐射效率显著高于没有这个成分的那些暴.结果表明两类暴的前身星和中心机制一致,是否呈现这个缓慢衰减成分可能取决于外部介质. 相似文献
12.
O. Reimer † K.T.S. Brazier A. Carramiñana G. Kanbach P.L. Nolan D.J. Thompson 《Monthly notices of the Royal Astronomical Society》2001,324(3):772-780
The EGRET telescope aboard the NASA Compton Gamma-Ray Observatory ( CGRO ) has repeatedly detected 3EG J1835+5918, a bright and steady source of high-energy gamma-ray emission which has not yet been identified. The absence of any likely counterpart for a bright gamma-ray source located 25° off the Galactic plane initiated several attempts of deep observations at other wavelengths. We report on counterparts in X-rays on a basis of a 60-ks ROSAT HRI image. In order to conclude on the plausibility of the X-ray counterparts, we reanalysed data from EGRET at energies above 100 MeV and above 1 GeV, including data up to CGRO observation cycle 7. The gamma-ray source location represents the latest and probably the final positional assessment based on EGRET data. We especially address the question of flux and spectral variability, here discussed using the largest and most homogeneous data set available at high-energy gamma-rays for many years. The results from X-ray and gamma-ray observations were used in a follow-up optical identification campaign at the 2.2-m Guillermo Haro Telescope at Cananea, Mexico. VRI imaging has been performed at the positions of all of the X-ray counterpart candidates, and spectra were taken where applicable. The results of the multifrequency identification campaign toward this enigmatic unidentified gamma-ray source are given, especially on the one object which might be associated with the gamma-ray source 3EG J1835+5918. This object has the characteristics of an isolated neutron star and possibly of a radio-quiet pulsar. 相似文献
13.
Yi-Zhong Fan 《Monthly notices of the Royal Astronomical Society》2009,397(3):1539-1548
Since the launch of the Fermi Gamma-ray Space Telescope on 2008 June 11, significant detections of high-energy emission have been reported only in six gamma-ray bursts (GRBs) until now. In this work we show that the lack of detection of a GeV spectrum excess in almost all GRBs, though somewhat surprising, can be well understood within the standard internal shock model and several alternatives like the photosphere internal shock (gradual magnetic dissipation) model and the magnetized internal shock model. The delay of the arrival of the >100 MeV photons from some Fermi bursts can be interpreted too. We then show that with the polarimetry of prompt emission these models may be distinguishable. In the magnetized internal shock model, a high linear polarization level should be typical. In the standard internal shock model, a high linear polarization level is still possible but much less frequent. In the photosphere internal shock model, the linear polarization degree is expected to be roughly anticorrelated with the weight of the photosphere/thermal component, which may be a unique signature of this kind of model. We also briefly discuss the implications of the current Fermi GRB data on the detection prospects of the prompt PeV neutrinos. The influences of the intrinsic proton spectrum and the enhancement of the neutrino number at some specific energies, due to the cooling of pions (muons), are outlined. 相似文献
14.
M. D. Leising 《Experimental Astronomy》2005,20(1-3):49-55
Despite their great intrinsic interest and extensive use as tools in other areas of astronomy, fundamental questions remain as to the nature of supernovae of all types. The radioactivity produced by nuclear fusion reactions in the explosions provides several excellent diagnostics, observable through gamma-ray emission. This great potential is largely unrealized because the fluxes from events at common distances are very small. Instrument sensitivity is paramount, and gamma-ray optics offer an excellent possibility for greatly increasing collecting area, without a large increase in background rates, and reaching the required sensitivities. Here we outline some of the major open questions about supernovae and discuss how gamma-ray spectroscopy can address them, including instrument requirements for a future focusing gamma-ray telescope.Supported by NASA and CESR. 相似文献
15.
Gabriele Ghisellini Davide Lazzati 《Monthly notices of the Royal Astronomical Society》1999,309(1):L7-L11
The recently detected linear polarization in the optical light curve of GRB 990510 renewed interest in how polarization can be produced in gamma-ray burst fireballs. Here we present a model based on the assumption that we are seeing a collimated fireball, observed slightly off-axis. This introduces some degree of anisotropy, and makes it possible to observe a linearly polarized flux even if the magnetic field is completely tangled in the plane orthogonal to the line of sight. We construct the light curve of the polarization flux, showing that it is always characterized by two maxima, with the polarization position angle changing by 90° between the first and the second maximum. The very same geometry as assumed here implies that the total flux initially decays in time as a power law, but gradually steepens as the bulk Lorentz factor of the fireball decreases. 相似文献
16.
J. D. Kurfess 《Solar physics》1988,118(1-2):347-363
Several instruments on approved space missions will provide coverage of energetic solar flare activity during the next solar maximum. However, only Japan's SOLAR-A is dedicated to observations of solar activity. These planned experiments will provide significant improvements in detection sensitivity for gamma rays and neutrons, generally using similar detection techniques to those employed previously. Improvements in the temporal resolution of energetic flare phenomena will also be realized, but with generally sporadic solar coverage. Important capabilities critically required for advancing our understanding of the solar flare phenomenon, such as dedicated high-resolution gamma-ray spectroscopy, imaging hard X-ray and low-energy gamma-ray detectors, polarimeters, and dedicated high-efficiency neutron detectors, are not included on any of the approved missions. 相似文献
17.
An analysis of our observations of the Geminga object with the GT-48 ground-based gamma-ray telescope has shown that its very-high-energy gamma-ray flux is modulated with a 59-s period. The 59-s period and its time derivative previously inferred from satellite data have been confirmed. According to our data, the period was 61.94 s in 1997 at MSD=50573. The statistical significance of this result is (1?4.5)×10?4. 相似文献
18.
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. 相似文献
19.
M. T. Murphy J. K. Webb I. S. Heng 《Monthly notices of the Royal Astronomical Society》2000,316(3):657-664
The mechanism for gamma-ray bursters and the detection of gravitational waves (GWs) are two outstanding problems facing modern physics. Many models of gamma-ray bursters predict copious GW emission, so the assumption of an association between GWs and gamma-ray bursts (GRBs) may be testable with existing bar GW detector data. We consider Weber bar data streams in the vicinity of known GRB times and present calculations of the expected signal after co-addition of 1000 GW/GRBs that have been shifted to a common zero time. Our calculations are based on assumptions concerning the GW spectrum and the redshift distribution of GW/GRB sources that are consistent with current GW/GRB models. We discuss further possibilities of GW detection associated with GRBs in light of future bar detector improvements and suggest that co-addition of data from several improved bar detectors may result in detection of GWs (if the GW/GRB assumption is correct) on a time-scale comparable to the LIGO projects. 相似文献
20.
D. D. Frederiks S. V. Golenetskii V. D. Palshin R. L. Aptekar V. N. Ilyinskii F. P. Oleinik E. P. Mazets T. L. Cline 《Astronomy Letters》2007,33(1):1-18
We analyze the data obtained when the Konus-Wind gamma-ray spectrometer detected a giant flare in SGR 1806-20 on December 27, 2004. The flare is similar in appearance to the two known flares in SGR 0526-66 and SGR 1900+14 while exceeding them significantly in intensity. The enormous X-ray and gamma-ray flux in the narrow initial pulse of the flare leads to almost instantaneous deep saturation of the gamma-ray detectors, ruling out the possibility of directly measuring the intensity, time profile, and energy spectrum of the initial pulse. In this situation, the detection of an attenuated signal of inverse Compton scattering of the initial pulse emission by the Moon with the Helicon gamma-ray spectrometer onboard the Coronas-F satellite was an extremely favorable circumstance. Analysis of this signal has yielded the most reliable temporal, energy, and spectral characteristics of the pulse. The temporal and spectral characteristics of the pulsating flare tail have been determined from Konus-Wind data. Its soft spectra have been found to contain also a hard power-law component extending to 10 MeV. A weak afterglow of SGR 1806-20 decaying over several hours is traceable up to 1 MeV. We also consider the overall picture of activity of SGR 1806-20 in the emission of recurrent bursts before and after the giant flare. 相似文献