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1.
Origination of gamma-ray burst pulses associated with the Doppler effect of spherical fireballs or uniform jet 下载免费PDF全文
Ryde and Petrosian have pointed out that the rise phases of
gamma-ray burst (GRB) pulses originate from the widths of the
intrinsic pulses and their decay phases are determined by the
curvature effect of the expanding fireball surface based on their
simplified formula. In this paper we investigate in detail the issue
based on the formula in Ref.[20], which is derived based on a model
of highly symmetric expanding fireballs, where the Doppler effect is
the key factor to be concerned about, and no terms are omitted in
their derivation. Our analyses show that the decay phases of the
observed pulses originate from the contributions from both the
curvature effect of the expanding fireball and the two timescales of
the local pulses, and the rise phases of the observed pulses only
come from the two timescales of the local pulses. Associated with a
local pulse with both rise and decay portions, the light curve of
GRBs in the rise portion is expected to undergo a concave phase and
then a convex one, whereas that in the decay portion is expected to
evolve by an opposite process. And the ratio of the concave timescale
to the convex one in the rise phase of the observed pulse linearly
increases with the ratio of the rising timescale to the decay one of
the local pulse ($r_{\rm rd}$), whereas the ratio of the convex
timescale to the concave timescale in its decay phase linearly
decreases with $r_{\rm rd}$. The two correlations are independent of
the local pulse forms and the rest-frame radiation forms. But the
different forms of local pulses and the different values of $r_{\rm
rd}$ gives rise to the diversity of the light curve pulse shapes. We
test a sample of 86 GRB pulses detected by the BATSE instrument on
board the Compton Gamma Ray Observatory and find that the
characteristics do exist in the light curve of GRBs. 相似文献
2.
Relationship between width of pulses and Lorentz factor expected from the light curve of fireball sources 下载免费PDF全文
Time profiles of many gamma-ray bursts consist of distinct pulses, which provides a possibility of characterizing the temporal structure of these bursts. We employ a simple model of highly symmetric fireballs to analyse the effect of the expansion speed on the light curve arising from different forms of local pulses. The relationship between the ratio r of the FWHM width of the rising phase of the light curve to that of the decaying phase and the Lorentz factor is investigated. The analysis shows that, when the rest frame radiation form is ignored, temporal profiles of the light curve arising from pulses of fireballs will not be affected by the expansion speed (that is, r is almost a constant) as long as the fireball expands relativistically. When the rest frame radiation form is taken into account, there will be a break in the curves of r - log F. The location of the break depends mainly on the adopted value of the rest frame peak frequency VO,p. One would reach almost the same result when a jet is considered. In addition, we utilize a sample of 48 individual GRB pulses to check the relationship between the ratio r and the expansion speed F. We find no significant correlation between them, and this is consistent with the theoretical analysis. 相似文献
3.
Bing Zhang 《Frontiers of Physics》2019,14(6):64402
The first gravitational wave (GW) – gamma-ray burst (GRB) association, GW170817/GRB 170817A, had an offset in time, with the GRB trigger time delayed by ~1.7 s with respect to the merger time of the GW signal. We generally discuss the astrophysical origin of the delay time, Δt, of GW-GRB associations within the context of compact binary coalescence (CBC) – short GRB (sGRB) associations and GW burst – long GRB (lGRB) associations. In general, the delay time should include three terms, the time to launch a clean (relativistic) jet, Δtjet; the time for the jet to break out from the surrounding medium, Δtbo; and the time for the jet to reach the energy dissipation and GRB emission site, ΔtGRB. For CBC-sGRB associations, Δtjet and Δtbo are correlated, and the final delay can be from 10 ms to a few seconds. For GWB-lGRB associations, Δtjet and Δtbo are independent. The latter is at least ~10 s, so that Δt of these associations is at least this long. For certain jet launching mechanisms of lGRBs, Δt can be minutes or even hours long due to the extended engine waiting time to launch a jet. We discuss the cases of GW170817/GRB 170817A and GW150914/GW150914-GBM within this theoretical framework and suggest that the delay times of future GW/GRB associations will shed light into the jet launching mechanisms of GRBs. 相似文献
4.
We discuss how the annihilation luminosity of a neutrino-cooled accretion disk in a gamma-ray burst, Lν ν, is determined by the disk’s fundamental parameters, namely, the mass of the central black hole M, the mass accretion rate M, and the viscosity parameter α. It is shown that Lν ν depends mainly on M in evidence, and decreases with increasing M, but is almost independent of α. This result argues additionally that the central black hole in a gamma-ray burst must be with a stellar mass. 相似文献
5.
LU RuiJing & LIANG EnWei Physical Science & Technology College Guangxi University Nanning China 《中国科学:物理学 力学 天文学(英文版)》2010,(1)
Using time-resolved spectral data for a sample of 30 pulses in 27 bright GRBs detected with CGRO/BATSE, we investigate the luminosity-peak energy relation (L-E p relation) in the decay phases of these pulses. A tight L-E p relation is found for most of the pulses, but its power law index is various among pulses, which is normally distributed at 1.84±0.60(1σ) for the pulses in our sample, roughly consistent with the L-E p relation within a GRB and the isotropic gamma-ray energy-E p relation among GRBs. The large scatter of the power law index cannot be explained with both the statistical or observational effects and it may be an intrinsic feature, indicating that no universal L-E p relation would be expected among GRBs/pulses. This may strongly weaken the cosmological use of this relation. 相似文献
6.
We obtained analytical expressions for the intensities of γ-quanta fluxes that were emitted by radioactive isotopes distributed
in soil and that experiented n-tuple scattering. We present these expressions in the form of a sum of multiple integrals of
simple form. The results of numerical integration performed for test examples are given.
Scientific-Research Institute of Nuclear Problems at the Belarusian State University, 11, Bobruiskaya St., 220050, Minsk,
Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 405–411, May–June, 1997. 相似文献
7.
The long-standing Galactic center gamma-ray excess could be explained by GeV dark matter(DM) annihilation,but the DM interpretation seems to conflict with recent joint limits from different astronomical scale observations such as dwarf spheroidal galaxies,the Milky Way halo,and galaxy groups/clusters.Motivated by 8 Be and~4 He anomalous transitions with possible new interactions mediated by a vector boson X,we consider a small fraction of DM mainly annihilating into a pair of on-shell vector bosons XX followed by X→ e~+e~-in this paper.The Galactic center gamma-ray excess is explained by this DM cascade annihilation.The gamma rays are mainly from inverse Compton scattering emission,and the DM cascade annihilation could be compatible with joint astrophysical limits and meanwhile be allowed by AMS-02 positron observation.The direct detection of this model is also discussed. 相似文献
8.
Summary We investigate by a statistical analysis possible correlations among the observational parameters of the γ-ray bursts: the
rise time, the decay time and spectral hardness. We discuss the physical constraints implied by the results.
To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee. 相似文献
9.
Jet precession in neutrino-cooled disks for gamma-ray bursts: The effects of the mass and spin of a black hole 下载免费PDF全文
We present a model of jet precession driven by a neutrino-cooled disk around a spinning black hole to explain the quasi-periodic features observed in some gamma-ray burst light curves.The different orientations of the rotational axes between the outer part of a neutrino-cooled disk and a black hole result in precessions of the central black hole and the inner part of the disk.Hence,the jet arising from the neutrino annihilation above the inner disk is driven to precession.We find that the period of precession is positively correlated with the mass as well as the spin of a black hole. 相似文献
10.
基于焦斑光强的空间频谱分析方法,建立了光谱色散匀滑技术(SSD)对焦斑匀滑的影响模型,提出了控制焦斑空间频率调制的响应函数.揭示了SSD参量对空间频率响应函数的影响规律.理论推导和数值模拟结果都表明:SSD对焦斑光强的频率响应具有周期调制性质,调制特性和色散角、光谱形状等相关.一般地,光谱形状控制空间响应函数形状,色散角决定所能匀滑的最低频率,色循环数可改变响应函数特点,调整对空间低频和高频的匀滑效果.空间频率响应函数的特点为多维SSD应用提出了应用准则.
关键词:
光谱色散匀滑
空间频谱
焦斑
响应函数 相似文献
11.
We show that the threshold of stimulated Raman scattering (SRS) from single micro‐droplets increases with the bandwidth of the pulsed excitation laser radiation. SRS thresholds were experimentally investigated for two droplet sizes and two excitation bandwidths. For the narrowband excitation, a frequency doubled Nd:YAG laser with a central wavelength of 532 nm, a full width half maximum (FWHM) bandwidth of 0.05 nm and a repetition rate of 10 Hz was used. For the comparison with the broadband excitation, a dye resonator containing Rhodamine 6G being pumped by the Nd:YAG laser was utilized with a central wavelength of 566 nm and a FWHM bandwidth of 4 nm. Droplets of 89 and 116 µm diameters, respectively, were illuminated by a vertical light sheet. If the broadband excitation is applied instead of the narrowband excitation ‐ for both droplet sizes ‐ the pulsed excitation energies can be increased by a factor of approximately 5 before the SRS threshold is reached. The multiplication register of an emCCD detector was used to detect low signals. The gain factor of the detector was calibrated and adapted to different excitation energies and signal intensities. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
12.
Spectral polarization-encoding of broadband laser pulses by optical rotatory dispersion and its applications in spectral manipulation 下载免费PDF全文
《中国物理 B》2021,30(7):77801-077801
We propose a kind of spectral polarization-encoding(SPE) for broadband light pulses, which is realized by inducing optical rotatory dispersion(ORD), and decoded by compensating ORD. Combining with polarization-sensitive devices, SPE can not only work to control polarization-dependent transmission for central wavelength or bandwidth-tunable filtering, but also can be used for broadband regenerative or multi-pass amplification with a polarization-dependent gain medium to improve output bandwidth. SPE is entirely passive thus very simple to be designed and aligned. By using an ORD crystal with a good transmission beyond 3-μm mid-infrared region, e.g., Ag Ga S_2, SPE promises to be applied for the wavelength tuning lasers in mid-infrared region, where the tunning devices are rather under developed compared with those in visible and near-infrared region. 相似文献
13.
14.
The persistent spectral hole-burning (PSHB) phenomenon observed in molecular doped polymers cooled down to liquid helium temperatures allows the engraving of spectral structures in the inhomogeneous absorption profile of the material. Therefore, a PSHB molecular-doped solid can be programmed in the spectral domain and then converted in an optical processor capable to achieve user-defined optical functions. We demonstrate the high storage capacity of naphthalocyanine-doped polymer materials by engraving and retrieving the phase information stored in femtosecond-chirped pulses, even with nanosecond time delay, which correspond to information registered with sub-GHz spectral resolution. Perspectives for the coherent control of light fields or photochemical processes are also evoked. 相似文献
15.
The effect of a tapered metal-coated optical fiber terminated by a sub-wavelength aperture (SWA) on the spectrum of the transmitted light is investigated experimentally. Under certain conditions a remarkable spectral modulation of the transmitted light can be observed. This effect is of a mesoscopic origin, occurring only for a certain interval of SWA diameters. One can conclude that a noticeable modulation appears when the number of the transmitted fiber modes is small but exceeds unity, thus indicating the presence of a phase shift between different modes. To discern between two possible sources of such phase shift, the fiber length dependence of the output spectrum has been studied. According to the results obtained for the used sample of 200 nm SNOM tip, the observed phase shift is mostly caused rather by the inherent modal dispersion of the multimode fiber than by the mode-dependent light slowdown in the tapered region close to SWA due to the coupling to surface plasmons of the metal coating. The SWA acts here mainly as an effective mode filter. 相似文献
16.
以气相甲烷分子ν1模Q支的拉曼光谱为例,采用拉曼诱导克尔效应谱(RIKES)进行峰形测量,并将其与同时测量的受激拉曼光声光谱(PARS)的峰形进行了比较.结果表明,在pump光和Stokes光均为线偏振的情况下,两者存在着差异;在拉曼共振峰的低频端,RIKES谱强度略高;而高频端则恰好相反.从信号产生机制出发,对此进行了合理解释.
关键词:
拉曼诱导克尔效应谱
受激拉曼光声光谱
峰形 相似文献
17.
超声反射层析成像的Fourier切片理论及对积分线弯曲影响的修正 总被引:2,自引:0,他引:2
本文针对不同接收方式推导了超声反射层析成像模型在远场条件下的Fourier切片理论,在此基础上,进一步给出了旁轴近似条件下的迭代重建公式,通过这种迭代运算,可以逐步消除投影积分线弯曲的影响,从而改善重建像的质量。 相似文献
18.
19.
LAN Congqing CHEN Yanhua Wuhan Institute of Physics Academia Sinica Wuhan )with the Institute of Acoustics Academia Sinica. 《声学学报:英文版》1993,(1)
For ultrasonic reflective tomographic imaging of differenttransmitter-receiver mode,we demonstrate that the Fourier slice theorem canbe used when the distance between the transducer and origin becomes muchlarger than the object to be reconstructed.Iterative reconstruction formulabased on the Fourier slice theorem is proposed for the case in which theparaxial approximation holds.The effect caused by the curvature of integrallines may be eliminated iteratively and better reconstructed images can be ex-pected. 相似文献