共查询到20条相似文献,搜索用时 15 毫秒
1.
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, Δ t, 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, Δt jet; the time for the jet to break out from the surrounding medium, Δ tbo; and the time for the jet to reach the energy dissipation and GRB emission site, Δ tGRB. For CBC-sGRB associations, Δtjet and Δ tbo are correlated, and the final delay can be from 10 ms to a few seconds. For GWB-lGRB associations, Δ tjet and Δ tbo are independent. The latter is at least ~10 s, so that Δ t of these associations is at least this long. For certain jet launching mechanisms of lGRBs, Δ t 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
2.
γ射线暴(称简γ暴)的研究在最近几年里有了巨大的突破。观测上,人们发现了γ暴的低能余辉以及与γ射线发同时的光学爆发,还发现了它位于宇学距离的寄主星系。越来越多的观测证据还表明长时标γ暴与恒星形成区、甚至可能与超新星成协。在γ暴的相对论火球模型框架下,人们对γ暴以及余辉的产生机制的认识也有了进展。进而人们对γ暴的前身星以及环境效应等有了新的认识。本文旨在对这些进展和认识给一个扼要的评述。 相似文献
3.
GRB 070610, which is also named Swift J195509.6+261406, is a peculiar Galactic transient with significant variability on short timescales in both X-ray and optical light curves. One possible explanation is that GRB 070610/Swift J195509.6 + 261406 is a soft gamma-ray repeater (SGR) in our Galaxy. Here, we use the fireball model, which is usually recognized as the standard model of gamma-ray burst (GRB) afterglows, and the energy injection hypothesis to interpret the X-ray and optical afterglow light curves of GRB 070610/Swift J195509.6 + 261406. It is found that the model is generally consistent with observations. 相似文献
4.
Extensive multi-band afterglow data are available for GRB 980703. Especially, its radio afterglow was very bright and was
monitored until more than 1000 days after the trigger time. Additionally, there is no obvious special feature, i.e., no rebrightenings,
no plateau, and no special steep decay or slow decay in the multi-band afterglow light curves. All these conditions make GRB
980703 a precious sample in gamma-ray burst research. Here we use the observational data of GRB 980703 to test the standard
fireball model in depth. It is found that the model can give a satisfactory explanation to the multi-band and overall afterglow
light curves. The beaming angle of GRB 980703 is derived as ∼ 0.23 radian, and the circum-burst medium density is ∼ 27 cm −3. The total isotropic equivalent kinetic energy of the ejecta is ∼ 3.8 × 10 52 ergs. A rest-frame extinction of A
V
∼ 2.5 mag in the host galaxy is also derived. 相似文献
5.
In some quantum gravity theories, a foamy structure of space-time may lead to Lorentz invariance violation(LIV). As the most energetic explosions in the Universe, gamma-ray bursts(GRBs) provide an effect way to probe quantum gravity effects. In this paper, we use the continuous spectra of 20 short GRBs detected by the Swift satellite to give a conservative lower limit of quantum gravity energy scale MQG. Due to the LIV effect, photons with different energy have different velocities. This will lead to the delayed arrival of high energy photons relative to low energy ones. Based on the fact that the LIV-induced time delay cannot be longer than the duration of a GRB,we present the most conservative estimate of the quantum gravity energy scales from 20 short GRBs. The strictest constraint, M_(QG) 5.05 × 10~(14) GeV in the linearly corrected case, is from GRB 140622 A. Our constraint on MQG,although not as tight as previous results, is the safest and most reliable so far. 相似文献
6.
探讨了具有单峰结构的伽玛射线暴(GRB)光变曲线的半峰全宽(FWHM)与伽玛暴持续时标 T之间的关系.用目前公认的半经验公式——Kocevski, Ryde & Liang (2003)模型对108个单峰光变曲线数据样本进行拟合,选取59个 χ2<2的有效拟合样本计算FWHM,然后对FWHM与 T进行相关分析.两者能较好地用幂率关系进行拟合为 T≈ BWa,其中 W为光变曲线的
关键词:
伽玛射线暴(GRB)
光变曲线
相关分析 相似文献
7.
Finding the electromagnetic(EM) counterpart of binary compact star merger, especially the binary neutron star(BNS) merger,is critically important for gravitational wave(GW) astronomy, cosmology and fundamental physics. On Aug. 17, 2017,Advanced LIGO and Fermi/GBM independently triggered the first BNS merger, GW170817, and its high energy EM counterpart,GRB 170817 A, respectively, resulting in a global observation campaign covering gamma-ray, X-ray, UV, optical, IR, radio as well as neutrinos. The High Energy X-ray telescope(HE) onboard Insight-HXMT(Hard X-ray Modulation Telescope) is the unique high-energy gamma-ray telescope that monitored the entire GW localization area and especially the optical counterpart(SSS17 a/AT2017 gfo) with very large collection area(~1000 cm~2) and microsecond time resolution in 0.2-5 MeV. In addition,Insight-HXMT quickly implemented a Target of Opportunity(ToO) observation to scan the GW localization area for potential X-ray emission from the GW source. Although Insight-HXMT did not detect any significant high energy(0.2-5 MeV) radiation from GW170817, its observation helped to confirm the unexpected weak and soft nature of GRB 170817 A. Meanwhile,Insight-HXMT/HE provides one of the most stringent constraints(~10~(-7) to 10~(-6) erg/cm~2/s) for both GRB170817 A and any other possible precursor or extended emissions in 0.2-5 MeV, which help us to better understand the properties of EM radiation from this BNS merger. Therefore the observation of Insight-HXMT constitutes an important chapter in the full context of multi-wavelength and multi-messenger observation of this historical GW event. 相似文献
8.
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
9.
In this paper, we critically assess GRB080503, a short gamma-ray burst with very bright extended emission (about 30 times the gamma-ray fluence of the initial spike). The light curve of the prompt γ-ray emission of GRB080503 resembles that of GRB 060614 which has been suggested to be due to an event from an intermediate mass black hole (IMBH) preying on a star. We therefore propose that GRB080503 is also due to a similar event; the mass of the IMBH is estimated to be about 4.6×104 solar masses, and the engulfed star had about the same mass and size as the Sun. We also estimate that the total burst energy is about 7.67 × 1050 ergs. 相似文献
10.
We investigate the gravitational collapse of a spherically symmetric, inhomogeneous star, which is described by a perfect fluid with heat flow and satisfies the equation of state p=ρ/3 at its center. In the process of the gravitational collapse, the energy
of the whole star is emitted into space. And the remaining spacetime
is a Minkowski one without a remnant at the end of the process. For a star with a solar mass and solar radius, the total energy emitted is at the
order of 10 54 erg, and the time-scale of the process is
about 8 s. These are in the typical values for a gamma-ray burst.
Thus, we suggest the gravitational collapse of a spherical star with
heat flow as a possible energy mechanism of gamma-ray bursts. 相似文献
11.
Gamma-ray bursts (GRBs) have puzzled astronomers since their accidental discovery in the sixties. The BATSE detector on the COMPTON-GRO satellite has been detecting one burst per day for the last six years. Its findings have revolutionized our ideas about the nature of these objects. They have shown that GRBs are at cosmological distances. This idea was accepted with difficulties at first. However, the recent discovery of an X-ray afterglow by the Italian/Dutch satellite BeppoSAX led to a detection of high red-shift absorption lines in the optical afterglow of GRB970508 and to a confirmation of its cosmological origin. The simplest and practically inevitable interpretation of these observations is that GRBs result from the conversion of the kinetic energy of ultra-relativistic particles flux to radiation in an optically thin region. The “inner engine” that accelerates the particles is hidden from direct observations. Recent studies suggest the “internal-external” model: internal shocks that take place within the relativistic flow produce the GRB while the subsequent interaction of the flow with the external medium produce the afterglow. The “inner engine” that produces the flow is, however, hidden from direct observations. We review this model with a specific emphasis on its implications to underground physics. 相似文献
12.
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
13.
Gamma-ray bursts (GRBs) have puzzled astronomers since their accidental discovery in the late 1960s. The BATSE detector on the COMPTON-GRO satellite has been detecting one burst per day for the last six years. Its findings have revolutionized our ideas about the nature of these objects. They have shown that GRBs are at cosmological distances. This idea was accepted with difficulties at first. The recent discovery of an X-ray afterglow by the Italian/Dutch satellite BeppoSAX has led to a detection of high red-shift absorption lines in the optical afterglow of GRB970508 and in several other bursts and to the identification of host galaxies to others. This has confirmed the cosmological origin. Cosmological GRBs release ∼10 51–10 53 erg in a few seconds making them the most (electromagnetically) luminous objects in the Universe. The simplest, most conventional, and practically inevitable, interpretation of these observations is that GRBs result from the conversion of the kinetic energy of ultra-relativistic particles or possibly the electromagnetic energy of a Poynting flux to radiation in an optically thin region. This generic “fireball” model has also been confirmed by the afterglow observations. The “inner engine” that accelerates the relativistic flow is hidden from direct observations. Consequently, it is difficult to infer its structure directly from current observations. Recent studies show, however, that this “inner engine” is responsible for the complicated temporal structure observed in GRBs. This temporal structure and energy considerations indicates that the “inner engine” is associated with the formation of a compact object – most likely a black hole. 相似文献
14.
We present a brief overview of follow-up observations of GRB afterglows made by the 0.8-m TNT and other telescopes at the Xinglong observatory during the last three years. Our system, dedicated to the measurement of early-time optical afterglow emission, responded to 50 GRBs from Jan. 2006 to Apr. 2009. Among them, about 50% have been successfully detected. The fastest response time is 76 sec (GRB 061110A and GRB 090426) after the space-borne GRB detector was triggered. The redshift distribution spans the range from z = 0.033 (GRB 060218) to z = 5.6 (GRB 060927). We also report the optical photometric follow-up of GRB 080330, which is an X-ray flash, as an example of our observations. 相似文献
15.
We calculate the high energy afterglow emission from short Gamma-Ray Bursts (SGRBs) in the external shock model. There are two possible components contributing to the high energy afterglow: electron synchrotron emission and synchrotron self-Compton (SSC) emission. We find that for typical parameter values of SGRBs, the early high-energy afterglow emission in 10 MeV-10 GeV is dominated by synchrotron emission. For a burst occurring at redshift z = 0.1, the high-energy emission can be detectable by Fermi LAT if the blast wave has energy E ⩾ 1051 ergs and the fraction of electron energy ɛ
e
⩾ 0.1. This provides a possible explanation for the high energy tail of SGRB 081024B. 相似文献
16.
We point out that the baryon loading problem in gamma-ray burst (GRB) models can be ameliorated if a significant fraction of the baryons which inertially confine the fireball is converted to neutrons. A high neutron fraction can result in a reduced transfer of energy from relativistic light particles in the fireball to baryons. The energy needed to produce the required relativistic flow in the GRB is consequently reduced, in some cases by orders of magnitude. A high neutron-to-proton ratio has been calculated in neutron star-merger fireball environments. Significant neutron excess also could occur near compact objects with high neutrino fluxes. 相似文献
17.
The γ-ray burst GRB 080319B light curve, observed in the energy range from 15 to 350 keV with a 64-ms time resolution by the Swift/BAT mission, has been investigated using a modified method of spectral analysis. The light curve revealed quasi-periodic oscillations with periods from 0.7 to 6 s, in particular, oscillations with constant periods of 0.89 and 1.28 s, independent of the γ-ray energy. 相似文献
18.
Gamma-ray bursts (GRBs) are short and intense emission of soft γ-rays, which have fascinated astronomers and astrophysicists
since their unexpected discovery in 1960s. The X-ray/optical/radio afterglow observations confirm the cosmological origin
of GRBs, support the fireball model, and imply a long-activity of the central engine. The high-energy γ-ray emission (> 20
MeV) from GRBs is particularly important because they shed some lights on the radiation mechanisms and can help us to constrain
the physical processes giving rise to the early afterglows. In this work, we review observational and theoretical studies
of the high-energy emission from GRBs. Special attention is given to the expected high-energy emission signatures accompanying
the canonical early-time X-ray afterglow that was observed by the Swift X-ray Telescope. We also discuss the detection prospect
of the upcoming GLAST satellite and the current ground-based Cerenkov detectors.
相似文献
19.
Compact binary mergers involving neutron stars can eject a fraction of their mass to space. Being extremely neutron rich, this material undergoes rapid neutron capture nucleosynthesis, and the resulting radioactivity powers fast, short-lived electromagnetic transients known as kilonova or macronova. Such transients are exciting probes of the most extreme physical conditions and their observation signals the enrichment of the Universe with heavy elements. Here the current understanding of the mass ejection mechanisms, the properties of the ejecta, and the resulting radioactive transients are reviewed. The first well-observed event in the aftermath of GW170817 delivered a wealth of insights, but much of today's picture of such events is still based on a patchwork of theoretical studies. Apart from summarizing the current understanding, questions where no consensus has been reached yet are also pointed out, and possible directions for the future research are sketched. In an appendix, a publicly available heating rate library based on the WinNet nuclear reaction network is described, and a simple fit formula to alleviate the implementation in hydrodynamic simulations is provided. 相似文献
20.
We calculate the red damping wing of Gunn-Peterson trough taking the evolution of the neutral fraction into consideration
and take a clear look at the ionized region around the ionizing sources. We get the result that the damping wing flux feature
is mainly determined by the neutral hydrogen outside the ionized bubble and the cut off in the damping wing would be useful
to get the size of the ionized bubble. We also fit the red damping wing of the recently discovered high redshift GRB080913
and find that the ionized bubble is too small to create apparent cut off in the spectrum of this burst.
Supported by the National Natural Science Foundation of China (Grant Nos. 10673034 and 10621303) and the National Basic Research
Program of China (Grant No. 2007CB815404) 相似文献
|