共查询到20条相似文献，搜索用时 15 毫秒
1.
《New Astronomy》2020
GRB 170817A was confirmed to be associated with GW170817, which was produced by a neutron star - neutron star merger. It indicates that at least some short gamma-ray bursts come from binary neutron star mergers. Theoretically, it is widely accepted that short gamma-ray bursts can be produced by two distinctly different mechanisms, binary neutron star mergers and neutron star - black hole mergers. These two kinds of bursts should be different observationally due to their different trigger mechanisms. Motivated by this idea, we collect a universal data set constituted of 51 short gamma-ray bursts observed by Swift/BAT, among which 14 events have extended emission component. We study the observational features of these 51 events statistically. It is found that our samples consist of two distinct groups. They clearly show a bimodal distribution when their peak photon fluxes at 15–150 keV band are plotted against the corresponding fluences. Most interestingly, all the 14 short bursts with extended emission lie in a particular region of this plot. When the fluences are plotted against the burst durations, short bursts with extended emission again tend to concentrate in the long duration segment. These features strongly indicate that short gamma-ray bursts really may come from two distinct types of progenitors. We argue that those short gamma-ray bursts with extended emission come from the coalescence of neutron stars, while the short gamma-ray bursts without extended emission come from neutron star - black hole mergers. 相似文献
2.
During February, 1981 and June, 1982 the gamma-ray and the hard X-ray spectrometers on the Hinotori satellite observed four gamma-ray bursts on 28 February, 21 July, 1981, 26 February and 13 March, 1982. These gamma-ray bursts were simultaneously observed by other satellites. The time histories and energy spectra are shown for these gamma-ray bursts, and the burst sizes (erg cm–2) are estimated. Two possible source locations for the burst of 21 July, 1981 are roughly determined from arrival time delays between two pairs of satellites, PVO-Hinotori and ISEE-3-Hinotori. The weak gamma-ray line peak structure around 1.8 MeV was observed for the burst of 13 March, 1982. The line could be interpreted in terms of gravitationally redshifted neutron capture line at 2.22 MeV. 相似文献
3.
Coalescing binary neutron stars are the most promising candidates for detection by gravitational-wave detectors and are considered
to be most promising for explaining the phenomenon of short gamma-ray bursts. The magnetic fields of neutron stars during
their coalescence can produce a number of interesting observational manifestations and can affect significantly the shape
of the gravitationalwave signal. In this paper, we model the distribution of magnetic fields in coalescing neutron stars by
the population synthesis method using various assumptions about the initial parameters of the neutron stars and the evolution
laws of their magnetic fields. We discuss possible electromagnetic phenomena preceding the coalescence of magnetized neutron
stars and the effect of magnetic field energy on the shape of the gravitational-wave signal during the coalescence. For a
log-normal (Gaussian in logarithm) distribution of the initialmagnetic fields consistent with the observations of radio pulsars,
the distribution inmagnetic field energy during the coalescence is shown to describe adequately the observed luminosity function
of short gamma-ray bursts under various assumptions about the pattern of field evolution and initial parameters of neutron
stars. 相似文献
4.
A possibility for gamma-ray bursts to arise due to thermonuclear flashes in the surface layers of accreting neutron stars is discussed. The principal difference of the sources of gamma-ray bursts from bursters is supposed to result from the existence of strong magnetic fields (1012–1013G) on the neutron star surface. It is shown that the thermonuclear energy released may be rapidly and effectively transported to the outer layers by MHD waves (in particular, by Alfvén waves). A very short growth time and rapid variations of some gamma-ray bursts may be easily explained in this case. 相似文献
5.
Exact analytic expressions for the vacuum electromagnetic fields produced by an oscillating magnetized sphere are obtained. The solutions are analysed for various modes of pulsation and for low-order multipole magnetic moments. Within the context of neutron star oscillations, the possibility of gamma-ray generation is discussed. It is shown that the radial pulsations provide an efficient mechanism for generation of gamma-radiation and electron-positron pairs in some regions around the neutron star. For this, the non-vanishing quadrupole magnetic moment oblique to the dipole moment is required. The model for gamma-ray bursts that we propose is briefly considered. 相似文献
6.
G. Chanmugam 《Astrophysics and Space Science》1976,42(1):83-87
A number of models have been proposed for the observed cosmic gamma-ray bursts. A class of such models involves the use of magnetic energy as the principal source of energy required for the bursts. In this case, arguments are presented to show that degenerate stars are favored. Mechanisms for magnetohydrodynamic instabilities in white dwarfs and neutron stars are discussed. Preliminary work indicates that magnetic white dwarfs can (but neutron stars probably cannot) account for many of the observed features of the bursts.Paper presented at the COSPAR Symposium on Fast Transients in X- and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975. 相似文献
7.
The gamma-ray burst GR170817 A associated with GW170817 is subluminous and subenergetic compared with other typical short gamma-ray bursts. It may be due to a relativistic jet viewed off-axis, or a structured jet or cocoon emission. Giant flares from magnetars may possibly be ruled out.However, the luminosity and energetics of GRB 170817 A are coincident with those of magnetar giant flares. After the coalescence of a binary neutron star, a hypermassive neutron star may be formed. The hypermassive neutron star may have a magnetar-strength magnetic field. During the collapse of this hypermassive neutron star, magnetic field energy will also be released. This giant-flare-like event may explain the luminosity and energetics of GRB 170817 A. Bursts with similar luminosity and energetics are expected in future neutron star-neutron star or neutron star-black hole mergers. 相似文献
8.
We study the conversion of a neutron star to a strange star as a possible energy source for gamma-ray bursts. We use different recent models for the equation of state of neutron star matter and strange quark matter. We show that the total amount of energy liberated in the conversion is in the range of &parl0;1-4&parr0;x1053 ergs (1 order of magnitude larger than previous estimates) and is in agreement with the energy required to power gamma-ray burst sources at cosmological distances. 相似文献
9.
J. -L. Puget 《Astrophysics and Space Science》1981,75(1):109-116
A review of recent theoretical work on gamma-ray bursts is given. The emphasis is put on the localization of sources. It is concluded that sources of gamma-ray bursts must be either old Population I or Population II objects with a mechanism implying that the sources are not too far from the galactic plane. According to this conclusion the more relevant models are probably flare stars or accretion on old neutron stars, radiation of the gravitational energy of the accretion, or thermonuclear explosions.Paper presented at the Symposium on Cosmic Gamma-Ray Bursts, held at Toulouse, France, 26–29 November, 1979. 相似文献
10.
The energy spectra of gamma-ray bursts differ from those of black-body radiation and are similar to the thermal bremsstrahlung
spectra of optically thin plasma. This could be realized if the source is located in the outer atmosphere of a neutron star.
In this case, almost one half of the emitted photons hit the surface of the star. The surface of the star is heated to a temperature
of the order 107 K, and a dominant flux of X-rays with a black-body spectrum would be expected. The X-rays produced by this mechanism are
detectable in the energy range from a few keV to 10 keV. This model is discussed in relation to the recent observations in
the X-ray region at the time of gamma-ray bursts, and modifications of this model are also presented. The observation in this
energy range will bring us valuable information on the nature of gamma-ray burst sources. 相似文献
11.
介绍了ＣｏｍｐｔｏｎＧＲＯ卫星对Ⅱ暴的最新观测结果。观测表明，γ暴源的空间分布是各向同性但不均匀的。这种分布基本上排除了γ暴起源于银盘内中子星的模型，表明γ暴要么位于展延的银晕里，要么位于宇宙学距离上。 相似文献
12.
Brad M. S. Hansen † Maxim Lyutikov† 《Monthly notices of the Royal Astronomical Society》2001,322(4):695-701
We describe the possible electromagnetic signals expected from the magnetospheric interactions of a neutron star binary prior to merger. We find that both radio and X-ray signals of detectable strength are possible. We discuss possible links with the phenomenon of gamma-ray bursts (GRBs) and describe the prospects for direct detection of these signals in searches for radio and X-ray transients. 相似文献
13.
The conversion from neutron stars with different equation of states (EOSs) for neutron matter into strange stars with different EOSs for strange quark matter has been studied in a general relativistic numerical calculation in this paper. For hot neutron stars, their conversion may lead to great variations in their rotation periods, of which the magnitude would be greatly dependent upon the EOS for neutron matter, and of which the timescale would be greatly determined by the EOS for strange matter. This phenomenon appears as giant glitches, which might provide a probe of EOSs for both neutron matter and strange matter. But for cold neutron stars, their conversion may result in a population of gamma-ray bursts. 相似文献
14.
Charles Meegan 《Astrophysics and Space Science》1998,261(1-4):215-224
There has been significant progress recently in our understanding of gamma-ray bursts. The long-sought counterparts at other
wavelengths have finally been found for a few bursts. This breakthrough is the result of coordinated observations involving
several satellites and ground-based optical and radio observatories. In one case, GRB970508, redshifted absorption lines have
been detected, finally settling the debate about the distance scale. The consensus is that the burst sources lie at cosmological
distances, requiring at least ∼ 1051ergs to be emitted in gamma rays in just a few seconds. The gamma radiation is thought to be produced by shocks in a highly
relativistic fireball. Many mysteries remain. There is no consensus on the nature of the sources, although coalescing neutron
stars are the leading candidate. There is evidence that the sources of the faintest bursts may be at redshifts above 2. If
so, gamma-ray bursts may ultimately tell us something about the early Universe.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
Cosmic gamma-ray burst spectroscopy 总被引：1，自引：0，他引：1
E. P. Mazets S. V. Golenetskii V. N. Ilyinskii Yu. A. Guryan R. L. Aptekar V. N. Panov I. A. Sokolov Z. Ya. Sokolova T. V. Kharitonova 《Astrophysics and Space Science》1982,82(2):261-282
A review is given of the gamma-ray burst energy spectrum measurements on Venera 11 and Venera 12 space probes. The gamma burst continuum approximates in shape thermal brems-strahlung emission of a hot plasma. The radiation temperature varies over a broad range, 50–1000 keV, for different events. Spectra of many bursts contain cyclotron absorption and/or redshifted annihilation lines. Strong variability is typically observed in both continuum and line spectra. These spectral data provide convincing evidence for the gamma-ray bursts being generated by neutron stars with superstrong magnetic fields 1012–1013 G. 相似文献
16.
We discuss a possible generation of radio bursts preceding final stages of binary neutron star mergings which can be accompanied
by short gamma-ray bursts. Detection of such bursts appear to be advantageous in the low-frequency radio band due to a time
delay of ten to several hundred seconds required for radio signal to propagate in the ionized intergalactic medium. This delay
makes it possible to use short gamma-ray burst alerts to promptly monitor specific regions on the sky by low-frequency radio
facilities, especially by LOFAR. To estimate the strength of the radio signal, we assume a power-law dependence of the radio
luminosity on the total energy release in a magnetically dominated outflow, as found in millisecond pulsars. Based on the
planned LOFAR sensitivity at 120 MHz, we estimate that the LOFAR detection rate of such radio transients could be about several
events per month from redshifts up to z∼1.3 in the most optimistic scenario. The LOFAR ability to detect such events would crucially depend on exact efficiency of
low-frequency radio emission mechanism. 相似文献
17.
Liu Tong 《Chinese Astronomy and Astrophysics》2019,43(2):143-177
Black hole hyperaccretion model is one of the potential candidates for the central engine of gamma-ray bursts. Combined with the complicated explosion phenomena including gamma-ray bursts, gravitational waves, and their electromagnetic counterparts, the results of a series of theoretical studies on this model are briefly reviewed in this paper. At the same time, as the research tools for the subsequent studies on gamma-ray bursts, some important conclusions and formulas are presented. 相似文献
18.
Simon F. Portegies Zwart † Tomonori Totani 《Monthly notices of the Royal Astronomical Society》2001,328(3):951-957
We present an internal shock model with external characteristics for explaining the complicated light curves of gamma-ray bursts. Shocks produce gamma-rays in the interaction between a precessing beam of relativistic particles and the interstellar medium. Each time the particle beam passes the same line of sight with the observer the interstellar medium is pushed outward. Subsequent interactions between the medium and the beam are delayed by the extra distance to be travelled for the particles before the shock can form. This results in a natural retardation and leads to an intrinsic asymmetry in the light curves produced for gamma-ray bursts. In addition, we account for the cooling of the electron–proton plasma in the shocked region, which gives rise to an exponential decay in the gamma-ray flux. The combination of these effects and the precessing jet of ultrarelativistic particles produces light curves that can be directly compared with observed gamma-ray burst light curves. We illustrate the model by fitting a number of observed gamma-ray bursts that are difficult to explain with only a precessing jet. We develop a genetic algorithm to fit several observed gamma-ray bursts with remarkable accuracy. We find that for different bursts the observed fluence, assuming isotropic emission, easily varies over four orders of magnitude from the energy generated intrinsically. 相似文献
19.
We analyze short-duration gamma-ray bursts (T
90<2 s) recorded in the SPI-ACS experiment of the INTEGRAL observatory. We found an extended emission in the averaged light
curve of both short-duration gamma-ray bursts and unidentified short-duration events. We show that the fraction of short-duration
gamma-ray bursts among all the gamma-ray bursts recorded in the SPI-ACS experiment may be as high as 30 to 45%. We find the
fraction of short gamma-ray bursts to augment while increasing the lower energy threshold. We report evidence for the absence
of the class of very short gamma-ray bursts. 相似文献
20.
B. J. Teegarden 《Astrophysics and Space Science》1995,231(1-2):137-144
Gamma-ray burst spectroscopy has at times been thought of as the key to understanding these mysterious events, and at others as a source of disappointment and confusion. Early spectral measurements contained evidence for cyclotron-line-like absorption and emission features. These results were the main anchor for the galactic neutron star paradigm for the origin of gamma-ray bursts. Ginga provided striking confirmation with evidence in three bursts for cyclotron absorption with both first and second harmonics present. The absorption line energies were consistent with the teragauss magnetic fields expected for neutron stars. The BATSE experiment on CGRO has dealt a severe blow to this paradigm. BATSE has found no evidence for the expected galactic anisotropy and also no evidence for cyclotron lines. The exact degree of inconsistency between BATSE and earlier GRB line results remains a complicated and unresolved question. In general, burst spectra display a wide variety of both spectral and temporal behavior. In essentially all bursts where spectral measurements are possible, the spectrum evolves during the burst. This spectral complexity and variability has presented researchers with a challenging task. At the present time, only the broadest correlations and characterizations are in hand. This paper will; 1) give a brief historical overview of GRB spectroscopic measurements and 2) provide a summary of the current observational situation with emphasis on the BATSE/Ginga controversy. 相似文献