共查询到20条相似文献，搜索用时 171 毫秒
1.
Comptonγ射线望远镜的直接解调成像 总被引：2，自引：0，他引：2
Ｃｏｍｐｔｏｎγ射线望远镜ＣＯＭＰＴＥＬ／ＣＧＲＯ工作于０．７５－３０ＭｅＶ能区，本应用直接解调方法分析了ＣＧＲＯ＃１观测的ＣＯＭＰＴＥＬ数据，准确定出Ｃａｒａｂγ射线源的位置，在１０－３０ＭｅＶ能区，分辨开最大似然法所不能完全分辨的Ｃｒａｂγ射线源和类星体ＰＫＳ０５２８＋１３４，得出优于传统成像方法所得的成像结果。 相似文献
2.
脉冲星Geminga MeV脉冲辐射证据 总被引：1，自引：0，他引：1
利用直接解调方法分析ＣＯＭＰＴＥＬ ＶＰ１数据,得到了脉冲星Ｇｅｍｉｎｇａ １０－３０ＭｅＶ脉冲辐射存在的证据;全位相及分位相成像均得到了Ｇｅｍｉｎｇａ。分位相成像结果显示,江变曲线的峰值位于ｐｕｌｓｅ１附近,而闰相区域只能给出上限。由于成 像分析不存在的选择效应,该成像结果表明,Ｇｅｍｉｎｇａ在ＭｅＶ能区仍存在脉冲辐射,虽然Ｇｅｍｉｎｇａ的弱ＭｅＶ辐射使得很难就ＶＰ１数据作时间分析,但仍得到了一 相似文献
3.
利用直接解调方法分析了ＣＯＭＰＴＥＬ对γ暴ＧＲＢ９１０６０１的观测数据,发现该γ暴的直接解调成像定位较ＣＯＭＰＴＥＬ用最大似然法分析得到的结果更接近于Ｕｌｙｓｓｅｓ－ＢＡＴＳＥ系统联合定位的圆环．结果表明,采用直接解调方法对γ暴这类信噪比高、统计性差的瞬变源进行成像分析是完全可行的,而且,γ暴的成像定位精度可由此而获得提高． 相似文献
4.
张澍 《中国天文和天体物理学报》1998,(2)
利用直接解调方法分析了ＣＯＭＰＴＥＬ对γ暴ＧＲＢ９１０６０１的观测数据,发现该γ暴的直接解调成像定位较ＣＯＭＰＴＥＬ用最大似然法分析得到的结果更接近于ＵｌｙｓｅｓＢＡＴＳＥ系统联合定位的圆环．结果表明,采用直接解调方法对γ暴这类信噪比高、统计性差的瞬变源进行成像分析是完全可行的,而且,γ暴的成像定位精度可由此而获得提高． 相似文献
5.
6.
在１９９１—１９９３年期间,Ｃｏｍｐｔｏｎγ射线天文台（ＣＧＲＯ）在射电源ＰＫＳ０５２８＋１３４中观测到两次很强的射线爆发,都伴随有毫米波射电大爆发．本文详细分析了高能γ－Ｘ射线波段和红外－光学波段的辐射能量分布（ＳＥＤ）．结果表明,高能γ射线辐射可能主要是由喷流相对论电子对周围ＵＶ－软Ｘ射线光子的逆康普顿散射所产生的．同时,通过毫米波射电大爆发的频谱演化特性与γ射线源的同步辐射频谱特性的比较,对γ辐射等离子团和射电等离子团之间可能的演化联系作了讨论． 相似文献
7.
用ASM／RXTE数据对Crab天区的直接解调成像 总被引：1，自引：0，他引：1
利用对象重建的直接解调技术,对ＡＳＭ／ＲＸＴＥ的模拟数据和Ｃｒａｂ天区观测数据进行了成像分析。结果表明,借助于对象重建的直接解调技术,可以利用正在运行的Ｘ射线天卫星ＲＸＴＥ上的全天监测器ＡＳＭ实现硬Ｘ射线天空的成像。 相似文献
8.
9.
本文详细讨论了Ｘ射线双星ＣｙｇＸ－３的Ｘ光子场对γ射线的吸收效应，计算结果表明：当ＣｙｇＸ－３的Ｘ光子发射场处于高态时，从致密中子星附近发射的能量为１０＾２－１０＾４ＭｅＶ的γ射线约有６０％被其吸收，吸收过程产生的正负电子的逆Ｃｏｍｐｔｏｎ散射会使出射能量１０－７０ＭｅＶ的 γ射线强度平均增加约５０％，计算的γ射线能谱与实验观测结果基本相符。 相似文献
10.
利用γ射线脉冲星Ｇｅｍｉｎｇａ自旋及频率变化的稳定性，采用位相相关的方法分析了ＥＧＲＥＴ对脉冲星Ｇｅｍｉｎｇａ四次观测间隔较长的数据，得到较为准确的守时参数ｆ．位相相关的结果与更长数据段折叠搜索的结果较为接近，表明对于自旋和频率变化都较为稳定的γ射线脉冲星，位相相关分析方法可以作为提高脉冲星参数精度的有效方法． 相似文献
11.
利用直接解调方法分析COMPTELVPI数据,得到了脉冲星Geminga10-30MeV脉冲辐射存在的证据：全位相及分位相成像均得到了Geminga．分位相成像结果显示,光变曲线的峰值位于pulse1附近,而其它位相区域只能给出上限．由于成像分析不存在选择效应,该成像结果表明,Geminga在MeV能区仍存在脉冲辐射．虽然Geminga的弱MeV辐射使得很难就VP1数据作时间分析,但仍得到了一些周期信号的迹象,并且与成像结果不相矛盾．进一步考察EGRET观测Geminga在30MeV以上的强度比Pulse2／Pulse1,发现在VP1观测的较低能区,Pulse1有渐强于Pulse2的趋势,这和我们在MeV能区的成像及时间分析结果相一致．成像得到的流强表明,Geminga的能谱至少在10MeV以上不应出现偏折． 相似文献
12.
Klaus Pinkau 《Experimental Astronomy》2009,25(1-3):157-171
Gamma-ray astronomy is devoted to study nuclear and elementary particle astrophysics and astronomical objects under extreme conditions of gravitational and electromagnetic forces, and temperature. Because signals from gamma rays below 1 TeV cannot be recorded on ground, observations from space are required. The photoelectric effect is dominant <100 keV, Compton scattering between 100 keV and 10 MeV, and electron–positron pair production at energies above 10 MeV. The sun and some gamma ray burst sources are the strongest gamma ray sources in the sky. For other sources, directionality is obtained by shielding / masks at low energies, by using the directional properties of the Compton effect, or of pair production at high energies. The power of angular resolution is low (fractions of a degree, depending on energy), but the gamma sky is not crowded and sometimes identification of sources is possible by time variation. The gamma ray astronomy time line lists Explorer XI in 1961, and the first discovery of gamma rays from the galactic plane with its successor OSO-3 in 1968. The first solar flare gamma ray lines were seen with OSO-7 in 1972. In the 1980’s, the Solar Maximum Mission observed a multitude of solar gamma ray phenomena for 9 years. Quite unexpectedly, gamma ray bursts were detected by the Vela-satellites in 1967. It was 30 years later, that the extragalactic nature of the gamma ray burst phenomenon was finally established by the Beppo–Sax satellite. Better telescopes were becoming available, by using spark chambers to record pair production at photon energies >30 MeV, and later by Compton telescopes for the 1–10 MeV range. In 1972, SAS-2 began to observe the Milky Way in high energy gamma rays, but, unfortunately, for a very brief observation time only due to a failure of tape recorders. COS-B from 1975 until 1982 with its wire spark chamber, and energy measurement by a total absorption counter, produced the first sky map, recording galactic continuum emission, mainly from interactions of cosmic rays with interstellar matter, and point sources (pulsars and unidentified objects). An integrated attempt at observing the gamma ray sky was launched with the Compton Observatory in 1991 which stayed in orbit for 9 years. This large shuttle-launched satellite carried a wire spark chamber “Energetic Gamma Ray Experiment Telescope” EGRET for energies >30 MeV which included a large Cesium Iodide crystal spectrometer, a “Compton Telescope” COMPTEL for the energy range 1–30 MeV, the gamma ray “Burst and Transient Source Experiment” BATSE, and the “Oriented Scintillation-Spectrometer Experiment” OSSE. The results from the “Compton Observatory” were further enlarged by the SIGMA mission, launched in 1989 with the aim to closely observe the galactic center in gamma rays, and INTEGRAL, launched in 2002. From these missions and their results, the major features of gamma ray astronomy are: Diffuse emission, i.e. interactions of cosmic rays with matter, and matter–antimatter annihilation; it is found, “...that a matter–antimatter symmetric universe is empirically excluded....” Nuclear lines, i.e. solar gamma rays, or lines from radioactive decay (nucleosynthesis), like the 1.809 MeV line of radioactive 26Al; Localized sources, i.e. pulsars, active galactic nuclei, gamma ray burst sources (compact relativistic sources), and unidentified sources. 相似文献
13.
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
14.
We report first evidence for a new unidentified and variable MeV source, located near the galactic plane at (l,b)∼(284.5°,
2.5°). The source, GRO J1036-55, is found at a significance level of ∼5.6σ by COMPTEL in its 3–10 MeV band. The energy spectrum indicates a spectral maximum at 3–4.3 MeV with a steep slope at higher
energies. Since the COMPTEL 3–4.3 MeV data contain contamination by an instrumental background line, we performed several
consistency checks, which all are consistent with an astrophysical nature of this emission feature. 相似文献
15.
A major legacy of the EGRET experiment aboard the Compton Gamma-Ray Observatory (CGRO) is the detection of a large number
of unidentified Gamma-ray sources. Out of the 271 EGRET sources are 170 not identified yet [Hartman et al. ApJS (123) (1999) 79]. To provide additional information on these unidentified EGRET sources, we derived simultaneous MeV fluxes
or flux limits for each source by analyzing the contemporaneous COMPTEL data. Then we compare these MeV fluxes to the extrapolations
of the published EGRET spectra. Our results can be grouped into 4 categories [Zhang et al. A&A (421) (2004) 983]: (1) non-constraining upper limits (∼120 sources), (2) hints (> 2 sigma) or detections with consistent
MeV fluxes (∼16 sources), (3) enhanced MeV emission (2 sources), and (4) constraining MeV flux limits, requiring a spectral
break (∼22 sources). In summary, for about 40 of the unidentified EGRET sources we can provide supplementary spectral information
in the neighboring gamma-ray band, which – together with other source parameters – might provide clues to the underlying source
nature. 相似文献
16.
R. M. Kippen J. Ryan A. Connors M. McConnell C. Winkler L. O. Hanlon V. Schönfelder J. Greiner M. Varendorff W. Collmar W. Hermsen L. Kuiper 《Astrophysics and Space Science》1995,231(1-2):231-234
In its first three years of operation, the COMPTEL instrument on theCompton Gamma-Ray Observatory has measured the locations (mean accuracy 1°) and spectra (0.75-30 MeV) of 18 gamma-ray bursts and continues to observe new events at a rate of 1/month. With good angular resolution and sensitivity at MeV energies, the growing COMPTEL burst catalog is an important new piece of evidence in the on-going GRB mystery. The COMPTEL burst locations are consistent with an isotropic distribution of sources, yet the spatial coincidence of two of the bursts indicates the possibility of repetition. The COMPTEL burst spectra are in most cases consistent with a single power law model with spectral index in the range 2–3. However, two bursts show evidence of a spectral break in the MeV range. Measurement of rapid variability at MeV energies in the stronger bursts provides evidence that either the sources are nearby (within the Galaxy) or the gamma-ray emission is relativistically beamed. We present an overview of analysis results obtained from the COMPTEL burst catalog concentrating on the search for burst repetition and the implications of highly variable MeV emission. 相似文献
17.
H.-D. Radecke 《Astrophysics and Space Science》1997,249(2):303-339
High energy gammay–ray emission from an extended region between the squasars 3C273 and 3C279 in Virgo has been detected by
the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory(CGRO). This emission shows a remarkably
constant flux over an observation time of
years between June 1991 and December 1993. The data analysis shows, that the structure is not the result of an instrumental
effect. The object has a perfect power law photon spectrum with index α=-2.06 ± 0.05 which is different from the spectra of
the neighboring quasars 3C273 and 3C279. Integration of the spectrum leads to a flux estimation of (7.0± 0.3) × 10-7 γ cm-2s-1 above 100 MeV. No galactic or extragalactic counterpart is found at other wavelengths. Indications point, however, at an
extragalactic origin of the gamma radiation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
Roland Diehl 《Experimental Astronomy》1995,6(4):103-108
The imaging telescope COMPTEL aboard the NASA Compton Observatory satellite has been demonstrated to be capable of imaging diffuse emission along the Galactic plane. Here we describe details of the imaging data spaces and methods to model the background. Different methods of imaging analysis are compared. Verification of consistency among these methods is a key factor in overall assessment of diffuse emission results. Source simulations and statistical analysis through the bootstrap method are applied to verify the significances of image structures. 相似文献
19.
R. K. Kaul 《Astrophysics and Space Science》1996,239(1):15-23
The implications of the recently reported 237 ms pulsed TeV gamma-ray signal from Geminga with respect to system energetics and gamma-ray emission mechanisms are discussed. Using the reported flux values in the MeV-GeV range from the EGRET and COMPTEL experiments and the published results on TeV emission, the derived emission spectrum of Geminga in the MeV-TeV energy range is shown to suggest a spectral break at 2 GeV, with the differential exponent changing from a value of –1.50 upto 2 GeV to a value of –2.7 in the TeV range. 相似文献
20.
Steven Boggs Mark Bandstra Jason Bowen Wayne Coburn Robert Lin Cornelia Wunderer Andreas Zoglauer Mark Amman Paul Luke Pierre Jean Peter von Ballmoos 《Experimental Astronomy》2005,20(1-3):387-394
On 1 June 2005, the prototype Nuclear Compton Telescope (NCT) flew on a high altitude balloon from Fort Sumner, New Mexico. NCT is a balloon-borne soft γ-ray (0.2–10 MeV) telescope for studying astrophysical sources of nuclear line emission and γ-ray polarization. Our program is designed to develop and test technologies and analysis techniques crucial for the Advanced Compton Telescope; however, our detector design and configuration is also well matched to the focal plane requirements for focusing Laue lenses. The NCT prototype utilizes two, 3D imaging germanium detectors (GeDs) in a novel, ultra-compact design optimized for nuclear line emission in the 0.5–2 MeV range. Our prototype flight provides a critical test of the novel detector technologies, analysis techniques, and background rejection procedures developed for high resolution Compton telescopes. 相似文献