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1.
本文分析了１９９３年１０月２日０７：３９：４０－０７：４１：００ＵＴ时段太阳产生的一个多脉冲微波暴的观测，认为它是由多个脉冲爆发叠加在一个慢变爆发背景上组成的．根据谱分析和利用我们的日冕磁场诊断公式［１］，第一次获得了一个爆发源区的磁场强度和高能电子的信息，其主要结果是：（１）脉冲爆发分量在光薄部分的射电谱指数的平均值比慢变爆发背景的值小１，即前者的谱比后者的硬．在１９．６ＧＨｚ上的亮度温度前者比后者高６倍．（２）从脉冲爆发分量和慢变爆发背景分量推断的源区磁场平均值分别为１５８和５３１高斯，且发现在爆发期间，慢变暴源区磁场强度随时间圣马鞍形变化，在极大相的值比脉冲相和下降相低约５０％（３）产生脉冲暴分量的高能电子的柱密度ＮＬ和数密度Ｎ（＞Ｅ０）分别为慢变暴分量的４％和８％，但它们所携带的能流和发射系数要比慢变爆发分量的值高１倍和８倍！表明这两种爆发成份可能分别来自能谱不同的两群电子在不同爆发源区的辐射． 相似文献
2.
R. Snijders 《Solar physics》1968,4(4):432-445
In this paper an attempt has been made to investigate theoretically the time-profile of an X-ray burst observed at photon energies well below 0.5 MeV. Following De
Jager (1967) this type of X-bursts is called deka-keV X-ray bursts. The energy distribution of fast electrons which emit the hard X-ray burst has been computed as a function of time. On the basis of these expressions the time-profile of a deka-keV burst has been calculated. In this paper two plausible initial electron distributions were chosen, a mono-energetic distribution and a maxwellian distribution of electron energies. It has been proved that the process of energy loss of an electron is completely governed by losses due to magnetic bremsstrahlung emission. This implies that the decay shape of a deka-keV X-ray burst is determined by the value of the magnetic-field strength existing in the plasma. A typical decay time of an X-ray burst, which is about 3 min, can be expected theoretically from a thermal plasma of temperature 109 °K confined by a magnetic field of about 750 gauss. The theory developed in this paper indicates that the soft X-ray burst accompanying the deka-keV burst lasts much longer than the deka-keV burst itself. 相似文献
3.
Analyzing a fiber burst occurring in the event on 19 August, 1981, plasma parameters of the burst source volume are estimated by means of Kuijpers' (1975) fiber burst model. The derived height dependence of the density in a coronal loop agrees with an isothermal barometric loop atmosphere. 相似文献
4.
Xue-Wen Liu 《Astrophysics and Space Science》2012,342(1):113-116
The late afterglow of gamma-ray burst is believed to be due to progressive deceleration of the forward shock wave driven by the gamma-ray burst ejecta propagating in the interstellar medium. We study the dynamic effect of interstellar turbulence on shock wave propagation. It is shown that the shock wave decelerates more quickly than previously assumed without the turbulence. As an observational consequence, an earlier jet break will appear in the light curve of the forward shock wave. The scatter of the jet-corrected energy release for gamma-ray burst, inferred from the jet-break, may be partly due to the physical uncertainties in the turbulence/shock wave interaction. This uncertainties also exist in two shell collisions in the well-known internal shock model proposed for gamma-ray burst prompt emission. The large scatters of known luminosity relations of gamma-ray burst may be intrinsic and thus gamma-ray burst is not a good standard candle. We also discuss the other implications. 相似文献
5.
Ren-Yang Zhao 《Astrophysics and Space Science》1994,218(2):205-211
Choosing a representative solar radio microwave burst, a typical burst which contains a precursor and an impulsive burst followed by a slowly decaying component, as an example, we have researched its radio emission mechanism and calculated the two important theoretical characteristic parameters, intensity and dimension, of its various sources. 相似文献
6.
Anna L. Watts Tod E. Strohmayer 《Monthly notices of the Royal Astronomical Society》2006,373(2):769-780
The nature of the asymmetry that gives rise to Type I X-ray burst oscillations on accreting neutron stars remains a matter of debate. Of particular interest is whether the burst oscillation mechanism differs between the bursting millisecond pulsars and the non-pulsing systems. One means to diagnose this is to study the energy dependence of the burst oscillations: here we present an analysis of oscillations from 28 bursts observed during the 2003 outburst of the accreting millisecond pulsar XTE J1814−338. We find that the fractional amplitude of the burst oscillations falls with energy, in contrast to the behaviour found by Muno et al. in the burst oscillations from a set of non-pulsing systems. The drop with energy mirrors that seen in the accretion-powered pulsations; in this respect XTE J1814−338 behaves like the other accreting millisecond pulsars. The burst oscillations show no evidence for either hard or soft lags, in contrast to the persistent pulsations, which show soft lags of up to 50 μs. The fall in amplitude with energy is inconsistent with current surface-mode and simple hotspot models of burst oscillations. We discuss improvements to the models and uncertainties in the physics that might resolve these issues. 相似文献
7.
《Chinese Astronomy and Astrophysics》2005,29(2):189-202
On 2001 Oct. 19, a very complex solar radio burst with a host of interesting features was observed with a broadband (0.7–7.6 GHz) solar radio spectrometer. Combining with the data of NoRH (Nobeyama Radio Heliograph) and TRACE (Transition Region and Corona Explorer), the spectral features of the radio burst, the evolution of the microwave radio sources, and relations with the complex EUV coronal loops are analyzed. The burst is the radio manifestation of a large double-ribbon flare; it consisted of two stages. The earlier stage was dominated bya broadband burst in the centimeter-meter waveband from gyro-synchrotron emission of sources at the footpoints of the loop. The later stage was dominated by a narrow-band decimeter wave burst in the decimetermeter waveband, from a combination of plasma emission and gyro-resonance emission from sources in the top of the loop. 相似文献
8.
R. Wijnands E. Rol E. Cackett R. L. C. Starling R. A. Remillard 《Monthly notices of the Royal Astronomical Society》2009,393(1):126-132
We present an analysis of the Swift Burst Alert Telescope (BAT) and X-ray telescope (XRT) data of GRB060602B, which is most likely an accreting neutron star in a binary system and not a gamma-ray burst. Our analysis shows that the BAT burst spectrum is consistent with a thermonuclear flash (type I X-ray burst) from the surface of an accreting neutron star in a binary system. The X-ray binary nature is further confirmed by the report of a detection of a faint point source at the position of the XRT counterpart of the burst in archival XMM–Newton data approximately six year before the burst and in more recent XMM–Newton data obtained at the end of 2006 September (nearly four months after the burst). Since the source is very likely not a gamma-ray burst, we rename the source Swift J1749.4−2807, based on the Swift /BAT discovery coordinates. Using the BAT data of the type I X-ray burst, we determined that the source is at most at a distance of 6.7 ± 1.3 kpc . For a transiently accreting X-ray binary, its soft X-ray behaviour is atypical: its 2–10 keV X-ray luminosity (as measured using the Swift /XRT data) decreased by nearly three orders of magnitude in about 1 day, much faster than what is usually seen for X-ray transients. If the earlier phases of the outburst also evolved this rapidly, then many similar systems might remain undiscovered because the X-rays are difficult to detect and the type I X-ray bursts might be missed by all the sky surveying instruments. This source might be part of a class of very fast transient low-mass X-ray binary systems of which there may be a significant population in our Galaxy. 相似文献
9.
《天文和天体物理学研究(英文版)》2020,(4)
The fast radio burst, FRB 171019, was relatively bright when discovered first by ASKAP but was identified as a repeater with three faint bursts detected later by GBT and CHIME. These observations lead to the discussion of whether the first bright burst shares the same mechanism with the following repeating bursts. A model of binary neutron star merger is proposed for FRB 171019, in which the first bright burst occurred during the merger event, while the subsequent repeating bursts are starquake-induced, and generally fainter, as the energy release rate for the starquakes can hardly exceed that of the catastrophic merger event. This scenario is consistent with the observation that no later burst detected is as bright as the first one. 相似文献
10.
Jin-xing Yao 《Chinese Astronomy and Astrophysics》1986,10(4):330-335
The main burst of the microwave burst of 1981 May 13 has a smooth, symmetric shape, the lifetime of the main burst is about the same in different wavelengths, the total duration is also about the same and its spectrum has a flat portion. This could be a new gradual type of burst. In this paper, a thermal model is proposed for the emission of this type of burst. 相似文献
11.
12.
A type III solar burst was observed at seven frequencies between 3.5 MHz and 80 kHz by the Michigan experiment aboard the IMP-6 satellite. From the data we can determine burst direction-of-arrival as well as time-of-arrival. We predict these quantities using simple models whose parameters we vary to obtain a good fit to the observations. We find that between 3.5 MHz and 230 kHz the observed radiation was emitted at the fundamental of the local plasma frequency while below 230 kHz it was emitted at the second harmonic. The exciter particles that produced the burst onset and burst peak have velocities of 0.27 and 0.12, respectively, in units of the velocity of light. 相似文献
13.
C. Sawyer 《Solar physics》1977,51(1):195-202
The event of 1969 May 19, 1430 UT included a flare, radio burst, and an active dark flocculus (ADF) or moving filament described by Vorpahl (1973) and a microwave negative burst superposed on a gradual rise and fall, described by Covington (1973). He found the interpretation of a second decrease at 2010 UT to be ambiguous in the absence of complete information. The second decrease is found here to be part of a series of events that parallels that of the earlier negative burst. Each decrease is superposed on a long-enduring burst that begins simultaneously with the eruption of a prominence near the equator at east limb and each is preceded by an ADF seen in H in a nearby active region. The similarity of these sequences strengthens the interpretation of the second event as a negative burst. The prominence eruptions, while not directly related to the negative bursts, add to a number of other signs of rapid changes in the large-scale structure of magnetic fields in the complex of active regions where the events took place. 相似文献
14.
E. Fürst 《Solar physics》1973,28(1):159-168
A typical microwave burst on 1968 January 11, 1700 UT is used to demonstrate that the radiation spectrum at maximum phase can be described by gyromagnetic absorption. A model for the source is derived from the observed spectrum. With the aid of this model, we try to explain the decreasing phase of the burst intensity. Satisfactory agreement with observation is obtained, when one assumes that the cooling of the burst plasma is caused by heat conduction parallel to the magnetic field lines. 相似文献
15.
We present the results of a study of the relationship of a complex meter-decameter wavelength radio burst observed with the Clark Lake E-W and N-S interferometers, with a hard X-ray burst observed with the X-ray spectrometer aboard ISEE-3. The radio burst consisted of several type III's, reverse drift type III's, a U burst, and type II and type IV bursts. The X-ray emission was also complex. The radio as well as hard X-ray emissions were observed before the flash phase of the flare; they were not always associated and we conjecture that this may constitute evidence for acceleration of electrons high in the corona. On the other hand, all components of the reverse drift burst were associated with hard X-ray subpeaks, indicating multiple injection of electron beams along field lines with different density gradients. While the type II burst appeared to be related to the hard X-ray burst, a detailed correspondence between individual features of the radio and hard X-ray burst emissions could not be found. The type IV burst started after all hard X-ray emissions ceased. Its source appeared to be a magnetic arch, presumably containing energetic electrons responsible for the gyrosynchrotron radiation of type IV.Presently at INPE/CRAAM, São Paulo, Brazil. 相似文献
16.
Using the Very Large Array, solar burst observations have been carried out simultaneously at 6 and 20 cm. Structural changes and preheating have been observed in the flaring regions on time scales of minutes to tens of minutes before the onset of the burst impulsive phase. The 6 cm burst sources are located close to the neutral line, or near the legs of a flaring loop. The 20 cm burst sources show complex and extended structures spatially separated from both the preburst emission and the gradual decay phase of the burst. We interpret the observations in terms of a two-component flare model (bulk heating as well as acceleration of particles) and derive the physical parameters of the burst sources.On leave of absence from Indian Institute of Astrophysics, Bangalore, India. 相似文献
17.
Observations of type III burst profiles at 18, 22, 26 and 36 MHz, by Barrow and Achong (1975), are used to calculate the form of the exciter function. The burst profile is treated as the convolution of an exciter function and an exponential decay function. The average form of the exciter profile is obtained directly from calculated profiles and further inferred from the first three statistical moments. Normalised average profiles of the burst and the exciter are presented for each frequency.The analysis shows that over the frequency range 18–36 MHz, (1) the exciter function possesses negative skewness, (2) the shapes of burst profiles and exciter profiles are approximately constant and, (3) burst peak time varies linearly with height in the corona. It is suggested that the passage of the exciting electron stream through field-dominated and flow-dominated coronal regions has different effects on the profiles. 相似文献
18.
Guobao Zhang Mariano Méndez Diego Altamirano Tomaso M. Belloni Jeroen Homan 《Monthly notices of the Royal Astronomical Society》2009,398(1):368-374
We have discovered a triple-peaked X-ray burst from the low-mass X-ray binary (LMXB) 4U 1636−53 with the Rossi X-ray Timing Explorer ( RXTE ). This is the first triple-peaked burst reported from any LMXB using RXTE , and it is only the second burst of this kind observed from any source. (The previous one was also from 4U 1636−53, and was observed with EXOSAT .) From fits to time-resolved spectra, we find that this is not a radius-expansion burst, and the same triple-peaked pattern seen in the X-ray light curve is also present in the bolometric light curve of the burst. Similar to what was previously observed in double-peaked bursts from this source, the radius of the emitting area increases steadily during the burst, with short periods in between during which the radius remains more or less constant. The temperature first increases steeply, and then decreases across the burst also showing three peaks. The first and last peak in the temperature profile occur, respectively, significantly before and after the first and last peaks in the X-ray and bolometric light curves. We found no significant oscillations during this burst. This triple-peaked burst, as well as the one observed with EXOSAT and the double-peak bursts in this source, all took place when 4U 1636−53 occupied a relatively narrow region in the colour–colour diagram, corresponding to a relatively high (inferred) mass-accretion rate. No model presently available is able to explain the multiple-peaked bursts. 相似文献
19.
本文简要地介绍了发生于２５４５ＭＨｚ和２６４５ＭＨｚ频率上的一次与白光耀斑共生的微波射电大爆发。该爆发有很高的峰值流量，很高的偏振度和很复杂的偏振状态的变化．同时该爆发的第一主峰期间同时观测到色球层白光耀斑连续辐射。本文还简要地讨论了这次射电爆发与色球白光耀斑的时间演化关系及射电爆发在主峰期间偏振状态急剧变化的原因。 相似文献
20.
V. N. Melnik A. I. Brazhenko A. A. Konovalenko H. O. Rucker A. V. Frantsuzenko V. V. Dorovskyy M. Panchenko A. A. Stanislavskyy 《Solar physics》2014,289(1):263-278
An unusual solar burst was observed simultaneously by two decameter radio telescopes UTR-2 (Kharkov, Ukraine) and URAN-2 (Poltava, Ukraine) on 3 June 2011 in the frequency range of 16?–?28 MHz. The observed radio burst had some unusual properties, which are not typical for the other types of solar radio bursts. Its frequency drift rate was positive (about 500 kHz?s?1) at frequencies higher than 22 MHz and negative (100 kHz?s?1) at lower frequencies. The full duration of this event varied from 50 s up to 80 s, depending on the frequency. The maximum radio flux of the unusual burst reached ≈103 s.f.u. and its polarization did not exceed 10 %. This burst had a fine frequency-time structure of unusual appearance. It consisted of stripes with the frequency bandwidth 300?–?400 kHz. We consider that several accompanied radio and optical events observed by SOHO and STEREO spacecraft were possibly associated with the reported radio burst. A model that may interpret the observed unusual solar radio burst is proposed. 相似文献