共查询到20条相似文献，搜索用时 140 毫秒
1.
定义了一个新的量,曲率宽度,去检查同步模型与伽玛射线暴(GRB)光谱的一致性.此量用于测量GRB中辐射能谱(νFν,ν和Fν分别是频率和随频率变化的能量流量)峰值处的光谱拐折锐度.然后使用它检查了理论同步模型与观测到的GRB光谱之间的一致性.首先计算几种典型的同步模型的曲率宽度,包括单能、单幂律和拐折幂律电子同步模型.其次从Fermi/GBM (Gamma-ray Burst Monitor)长GRB时间分辨光谱目录中选择包含1198个光谱的GRB样本,将光谱与常用的经验模型拟合,并计算最佳拟合模型的光谱曲率宽度.通过比较两个曲率宽度,发现大多数样本与同步模型不一致,因为同步模型的光谱拐折比数据的光谱拐折更加平滑.结果表明同步模型很难适合大多数观测到的GRB光谱.此外,在暴脉冲中发现光子流量和曲率宽度之间存在强的反相关性,这表明流量越高,光谱拐折越尖锐,或者与同步模型的偏差就越大. 相似文献
2.
伴随着引力波事件GW170817的短暴GRB (Gamma-Ray Burst) 170817A首次提供了双中子星并合与短暴相联系的直接证据.但是短暴GRB 170817A具有非常弱的光度,意味着观测的视线方向可能偏离喷流轴方向.根据短暴静止系的峰值能量E_(p,i)和各向同性光度L_(iso)。之间的关系以及洛伦兹因子Γ和L_(iso)。之间的关系估算了短暴GRB 170817A以及长短暴GRB 060614观测角与喷流边缘的夹角θ'_(obs)和洛伦兹因子Γ,结果表明GRB 170817A的Γ=45±27,θ'_(obs)=2.2±0.5°,而GRB 060614的Γ=214±93,θ'_(obs)=0.5±0.1°.这个结果相当于GRB 170817A的正轴各向同性光度L_(iso,on)=(2.1±0.7)×10~(49) erg·s~(-1),比典型的短暴少2-3个数量级.GRB 060614的L_(iso,on)=(5.12±1.91)×10~(51) erg·s~(-1)与典型短暴相当.这意味着GRB 060614可能属于短暴类型,而GRB 170817A可能本质上就是一个弱暴. 相似文献
3.
《天文研究与技术》2021,(4)
研究表明,耀发的能谱延迟与耀发特性参数(峰值时间、宽度、上升时间和衰减时间)有较强的相关性,随着时间的推移,耀发变宽,能谱延迟变大。使用离散相关函数(Discrete Correlation Function, DCF)对一个具有10个耀发的多耀发伽马暴(GRB 051117A)进行能谱延迟研究发现,在GRB 051117A内,能谱延迟与耀发的峰值时间、宽度、上升时间、衰减时间存在较强的相关性,即lag∝t_(peak),w,t_(rise),t_(decay)。在伽马暴内部耀发也随时间演化,即随着时间的推移,耀发的宽度越宽,能谱延迟越大。将伽马暴之间存在的能谱延迟与耀发特性参数的关系拓展到伽马暴内部,可以帮助我们对多耀发伽马暴有更深的理解。GRB 051117A内部的耀发特性参数之间存在的相关关系与多个伽马暴之间甚至是瞬时辐射脉冲高度相似,这也为X射线耀发与瞬时辐射脉冲可能是同一物理起源提供支持。 相似文献
4.
给出了1997年4月15日至17日在北京天文台用2.16 m望远镜卡焦光谱仪观测获得的6颗激变变星 (AB Boo, UX UMa, T CrB, AH Her, Z Cam 和 V426 Oph) 及3颗相关天体(UMa3, EG UMa 和 Leo3)的CCD光谱, 并同时拍摄了5颗晚型星(3 Dra, Vir, Leo, 34 Boo 和36Com) 的CCD 光谱, 作为晚型星参考谱. 测量了观测样本星的和近红外Ca II的三重线(8498, 8542和 8662)的等值宽度(EW),谱线半极大全宽(FWHM)和视向速度(Vr), 并分析了这些星的活动性. 相似文献
5.
利用Union2 557个Ia型超新星数据限制宇宙学参数qo、jo和so,在红移z≤1.4范围内校准5个γ暴(gamma-ray burst,GRB)光度关系.假设γ暴光度关系不随红移演化,得到66个高红移γ暴的距离模数.最后综合利用宇宙微波背景(Cosmic Microwave Background,CMB)辐射观测数据、重子声波震荡(Baryon AcousticOscillations,BAO)观测数据与116个具有红移的γ暴数据限制几个常见的暗能量模型.根据贝叶斯判据(Bayesian Information Criterion,BIC),发现ACDM模型是最好的模型;根据Akaike判据(Akaike Information Criterion,AIC),发现JBP模型是最好的模型. 相似文献
6.
基于BATC巡天组近十年的观测值班记录,统计了兴隆观测站可观测时间随月份的变化,结果表明平均每年大约有195个可观测夜(约1986小时),其中大约有87个观测夜(约918小时)用来巡天,约有18个观测夜用来测光.另外还统计了兴隆观测站施密特望远镜十年来北极天区的观测图像中星像的半高全宽(FWHM)随月份的变化,结果表明一年内平均星像的半高全宽约为2.3像元(老CCD)或2.2像元(新CCD).一般来说,夏季的星像要好于冬季,这与刘颖(Liu)等人2003年[1]的结果基本一致. 相似文献
7.
本文考虑了一个有临边昏暗的球形刚体自转恒星模型,并考虑仪器轮廓是高斯曲线,计算了一系列转致轮廓与仪器轮廓的卷积。由计算结果得到了转致轮廓半强度宽PHW与卷积后轮廓半强度宽CHW的关系图,以及仪器轮廓半强度宽GHW与卷积后轮廓半强度宽CHW的关系图。表明,当RHW/GHW>2时,就半强度宽(FWHM)而言,卷积的结果使其变窄(而不是加宽);但是,这一变化不大于RHW的3％。这一结果使得在某些情况下对不同仪器上进行的恒星自转速度测量的归算变得简单。理论计算还指出,有可能利用实测的V·sin i—FWHM关系得到临边昏暗系数ε;并利用文献中的观测资料初步得到早型恒星O9.5—B9的临边昏暗系数为0.44—0.99。 相似文献
8.
围绕着恒星级黑洞的中微子主导吸积盘可以通过盘上发出的中微子湮灭为伽玛暴提供能量。对于黑洞超吸积系统,吸积可能引起黑洞特征的极大演化,这会进一步引起中微子光度的演化。考虑不一样的平均吸积率和初始黑洞参数,通过吸积系统的演化分析中微子湮灭光度和总的中微子湮灭能量随时间的变化。同时计算了短暴GRB 090510的中微子湮灭能量并与理论预测的结果比对,发现中微子主导吸积盘的中微子湮灭能量的理论预测值远高于观测值,意味着这种模型可能提供GRB 090510爆发所需要的能量。 相似文献
9.
《天文学进展》2021,(1)
I型X射线暴(热核暴)是发生在小质量X射线中子星双星系统中X射线波段流量突然大幅度增加的一种高能现象。在热核闪模型下,此现象被认为主要由中子星表面热核不稳定燃烧主要引起的。典型X射线暴的光变曲线呈现快速上升(1～5 s)、幂指数下降(10～100 s)的单峰结构。随着X射线暴样本的增加,在观测上出现了一类多峰结构的热核暴。在现有的115个暴源中,至少6个暴源有此类多峰结构暴。通过研究多峰暴的观测性质,发现多峰暴只出现在极少数不同类型不同吸积状态的暴源中,其中大部分多峰暴的峰值流量小于爱丁顿极限,除少数多峰暴呈三峰结构以外,大部分多峰暴是双峰结构,并且双峰暴的两峰值相对强弱没有固定规律,暴频振荡在多峰暴当中的出现也无明显规律性。针对这些观测现象,总结了关于多峰暴的多个理论解释。 相似文献
10.
《天文研究与技术》2021,(4)
搜集了3C 279的29个态的光谱能量分布(Spectral Energy Distributions, SEDs)作为样本,使用稳态拐折幂律电子能谱分布(Electron Energy Distribution, EED)情况下的单区均匀轻子模型进行拟合,进而研究该源光变时外在观测与内在物理特性及它们之间的关系。主要结果如下:(1)我们的结果支持光变的激波解释(但需要斜激波)或磁重联解释。(2)外康普顿(External Compton, EC)峰的峰值光度logν■L■和磁场logB之间存在一个显著的反相关关系。多普勒因子logδ和外康普顿峰的峰值光度logν■L■之间存在正相关关系,意味着多普勒因子的增加是外康普顿峰的峰值光度升高的原因之一。(3)同步峰的峰值频率logν■和峰值光度logν■L■之间不存在显著的正相关关系,意味着反耀变体序列不一定对所有耀变体成立。(4)参数U_e/U_B(相对论电子能量密度与磁场能量密度的比值)远离1,说明相对论电子与磁场之间均分趋势不明显,并且参数U_e/U_B中比值大于1的占86%,意味着3C 279中的喷流大多数以粒子为主导;从P_B(磁场功率)P_r(辐射功率)P_e(相对论电子功率)P_p(冷质子功率)的关系中,P_p/P_(jet)(冷质子功率与喷流功率的比值) 0.5表明3C 279喷流中的能量大概率也是由冷质子携带的。同时,我们发现3C 279中γ射线耗散区位于距离黑洞中心0.1～1.8 pc处,暗示着它们位于宽线区(Broad-Line Region, BLR)之外,尘埃环(Dusty Torus, DT)之内。 相似文献
11.
M. N. Pavlinsky S. A. Grebenev P. A. Mazov I. A. Dekhanov D. B. Ryvkin R. A. Sunyaev V. I. Surtaev N. V. Mokrousov A. G. Glushenko S. I. Yampol’skii A. D. Novikov 《Astronomy Letters》2000,26(12):779-787
The Spin-X wide-field X-ray monitor of the Spectrum-X-Gamma astrophysical observatory, which is based on the principle of a coded-aperture telescope, is designed to detect and localize cosmic gammaray-burst (GRB) sources; to survey large areas of the sky in search of new transients; and to carry out long-term observations of bright Galactic sources, including X-ray bursters. The monitor consists of two noncoaxial identical modules, Spin-X1 and Spin-X2, which together cover 6.8% of the sky. The high-apogee, four-day orbit of the Spectrum-XG satellite allows the instrument to be in observing mode more than 50% of the time. Having simulated the rate of GRB detection by Spin-X, we show that extrapolating BATSE 50–300-keV average data on the number of GRBs, their duration, and their mean energy spectrum to the X-ray energy band leads to disagreement with the observed detection rate of GRBs in the X-ray band. The number of GRBs that can be detected and localized with an accuracy r≤3′ (3σ) (the error-circle radius) by Spin-X is estimated to be ten bursts per year. We present data on the Spin-X sensitivity achievable during long-term observations of persistent and transient sources and on its sensitivity to X-ray bursts from Galactic sources in the 2–30-keV energy band. 相似文献
12.
13.
R. A. Burenin O. V. Terekhov R. A. Sunyaev A. V. D’yachkov G. Khavenson B. S. Novikov I. D. Tserenin K. M. Sukhanov P. Goldoni A. Claret A. Goldwurm J. Paul F. Pelaez E. Jourdain J. -P. Roques G. Vedrenne 《Astronomy Letters》2000,26(7):413-422
We present the observations of cosmic gamma-ray bursts (GRBs) with the main detector of the SIGMA telescope onboard the Granat Observatory from January 1990 through September 1994. The observations were carried out in the energy range 35–1300 keV. We detected 36 GRBs and 31 high-energy solar flares during this period. No GRB fell within the main field of view; they were all recorded by the “secondary optics” of the telescope. The SIGMA telescope recorded relatively bright bursts with peak fluxes of 10?6–10?4 erg s?1 cm?2 in the 100–500-keV energy band. Stable detector background allows the long-term variability of GRB sources on a time scale of ～1000 s to be studied. The results of our search for early afterglows of GRBs are presented. The flux averaged over all bursts in the interval 100–800 s after the main event is 0.36±0.14 counts s?(35–300 keV), suggesting that there is soft gamma-ray emission on this time scale after a considerable number of GRBs. 相似文献
14.
In this paper, we have performed a temporal analysis of single pulses from short (46) and long (51) gamma-ray bursts (GRBs)
to investigate possible differences in their properties. In particular we pay detailed attention to the asymmetry of pulses.
We find that the asymmetry ratio of short GRB pulses clusters around 0.81 and that these pulses are on average more symmetric
than those from long GRBs, which have an average value of 0.47. In addition we note that the pulses in short GRBs display
exponential rises and fast decays (ERFD) in comparison the fast rise exponential decays (FRED) pulses of long GRBs. The asymmetry
ratio does not depend on the full width at half maximum (FWHM) and does not vary with energy channel. Moreover, there is a
general trend for slower pulses to be more asymmetric. Finally, we deduce that the asymmetry could be used to probe the emission
mechanisms of GRBs. 相似文献
15.
J. I. Cabrera C. Firmani V. Avila-Reese G. Ghirlanda G. Ghisellini L. Nava 《Monthly notices of the Royal Astronomical Society》2007,382(1):342-355
We study the spectral and energetics properties of 47 long-duration gamma-ray bursts (GRBs) with known redshift, all of them detected by the Swift satellite. Due to the narrow energy range (15–150 keV) of the Swift -BAT detector, the spectral fitting is reliable only for fitting models with two or three parameters. As high uncertainty and correlation among the errors is expected, a careful analysis of the errors is necessary. We fit both the power law (PL, two parameters) and cut-off power law (CPL, three parameters) models to the time-integrated spectra of the 47 bursts, and we present the corresponding parameters, their uncertainties and the correlations among the uncertainties. The CPL model is reliable only for 29 bursts for which we estimate the ν f ν peak energy E pk . For these GRBs, we calculate the energy fluence and the rest-frame isotropic-equivalent radiated energy, E γ,iso , as well as the propagated uncertainties and correlations among them. We explore the distribution of our homogeneous sample of GRBs on the rest-frame diagram E 'pk versus E γ,iso . We confirm a significant correlation between these two quantities (the 'Amati' relation) and we verify that, within the uncertainty limits, no outliers are present. We also fit the spectra to a Band model with the high-energy PL index frozen to −2.3, obtaining a rather good agreement with the 'Amati' relation of non- Swift GRBs. 相似文献
16.
We discuss the prompt emission of gamma-ray bursts (GRBs), allowing for γγ pair production and synchrotron self-absorption.
The observed hard spectra suggest heavy pair-loading in GRBs. The re-emission of the generated pairs results in the energy
transmission from high-energy gamma-rays to long-wavelength radiation. Due to strong self-absorption, the synchrotron radiation
by pairs is in optically thick regime. Thus, the re-emission would appear as a thermal-like spectral bump in the extreme-ultraviolet/soft
X-ray band, other than the peak from the main burst. The confirmation of the thermal-like feature and the double-peak structure
by future satellites, such as Swift, would indicate that the dominant radiation mechanism in GRBs is synchrotron rather than inverse-Compton radiation. 相似文献
17.
The intensity distribution of solar radio bursts observed in the frequency band 0.245–17 GHz has heen derived statistically. The distribution law has been found to be quite different from that of a power law as reported by earlier workers. This distribution leads to the error function, when the total number of bursts in any intensity range is found out. The generalized distribution law can be approximated to the power law only in the frequency band 0.65–2.8 GHz. 相似文献
18.
Maurice H. P. M. van Putten Alok C. Gupta 《Monthly notices of the Royal Astronomical Society》2009,394(4):2238-2246
Rotating black holes can power the most extreme non-thermal transient sources. They have a long-duration viscous time-scale of spin-down, and produce non-thermal emissions along their spin-axis, powered by a relativistic capillary effect. We report on the discovery of exponential decay in Burst and Triensient Source Experiment (BATSE) light curves of long gamma-ray bursts (GRBs) by matched filtering, consistent with a viscous time-scale, and identify ultra-high energy cosmic rays (UHECRs) about the Greisen–Zatsepin–Kuzmin (GZK) threshold with linear acceleration of ion contaminants along the black hole spin-axis, consistent with black hole masses and lifetimes of Fanaroff–Riley type II (FR II) active galactic nuclei (AGN). We explain the absence of UHECRs from BL Lac objects due to UHECR emissions preferably at appreciable angles away from the black hole spin-axis. Black hole spin may be the key to unification of GRBs and their host environments, and to AGN and their host galaxies. Our model points to long-duration bursts in radio from long GRBs without supernovae and gravitational waves from all long GRBs. 相似文献
19.
I. V. Arkhangelskaja 《Astronomy Letters》2002,28(8):509-521
The TTE/BATSE time profiles for short gamma-ray bursts (GRBs) are analyzed. A sample of 287 short GRBs and a sample of 143 background regions are studied. Bursts similar to BRBs with precursors and bursts with time profiles that are not encountered among the bursts whose time profiles were investigated by using a combination of DISCSC and PREB data. In addition, there are fewer events with single-peak time profiles among short GRBs than among long GRBs (many double and triple bursts). A fractal analysis of the TTE time profiles for short GRBs is performed. According to the TTE data, the range of fractal dimensions for short bursts is 0.80≤D≤2.25. The derived fractal-dimension distribution exhibits two peaks that correspond to a similar distribution obtained previously by reducing the DISCSC data for short GRBs (D=1.44±0.02 and D=1.90±0.03) and a third peak (D=1.05±0.03). The bursts with 〈D〉=1.90±0.03 correspond to events in whose sources the processes with long-term variations and (or) quasi-periodicity take place, while the event time profiles with a fractal dimension 〈D〉=1.05±0.03 correspond to events in whose sources many extremely short random processes take place. A more detailed analysis of a subgroup of bursts with D=1.44±0.02 shows that its fractal dimension distribution is broader than that for a group with the same (within the limits of the measurement errors) D. At least two more GRB subgroups can be distinguished in this subgroup: (1) bursts with 〈D〉=1.51±0.04; according to the TTE data, their fractal dimensions correspond to those of the background; i.e., these are events with smooth time profiles without any variability in the sources on the time scales on which the fractal dimension is analyzed; and (2) bursts with 〈D〉=1.31±0.05, whose time profiles can correspond to those of the events obtained from the fireball model with internal shock waves. We present time profiles for the events obtained by using this model. The range of fractal dimensions for the modeled time profiles is 1.213≤D≤1.400, with the fractal dimensions for such an event and for the real GRB 990208 being equal, within the error limits, for some model parameters. A study of the TTE and DISCSC fractal-dimension distributions for the background indicates that the fractal dimension distributions obtained by analyzing these two types of data can be processed simultaneously. 相似文献
20.
Arikkala Raghurama Rao Rupal Basak Jishnu Bhattacharya Sarthak Chandra Nikunj Maheshwari Manojendu Choudhury Ranjeev Misra 《天文和天体物理学研究(英文版)》2014,(1):35-46
We performed detailed time-resolved spectroscopy of bright long gammaray bursts(GRBs)which show significant GeV emissions(GRB 080916C,GRB090902B and GRB 090926A).In addition to the standard Band model,we also use a model consisting of a black body and a power law to fit the spectra.We find that for the latter model there are indications of an additional soft component in the spectra.While previous studies have shown that such models are required for GRB 090902B,here we find that a composite spectral model consisting of two blackbodies and a power law adequately fits the data of all the three bright GRBs.We investigate the evolution of the spectral parameters and find several interesting features that appear in all three GRBs,like(a)temperatures of the blackbodies are strongly correlated with each other,(b)fluxes in the black body components are strongly correlated with each other,(c)the temperatures of the black body trace the profile of the individual pulses of the GRBs,and(d)the characteristics of power law components like the spectral index and the delayed onset bear a close similarity to the emission characteristics in the GeV regions.We discuss the implications of these results and the possibility of identifying the radiation mechanisms during the prompt emission of GRBs. 相似文献