Optical studies of the regions of the gamma-ray bursts of 19 November, 1978 and 5 March, 1979

Optical studies were made of two well-located gamma-ray burst regions in the Southern Hemisphere using the 1.5 m telescope at the Cerro Tololo Inter-American Observatory in Chile. Multi-filter image tube plates and UBV photometry surveys were made of both regions. The field of the 19 November, 1978 gamma-ray burst shows no early star or star with unusual colors out to several diameters of the nominal error box. The region of the 5 March, 1979 gamma-ray burst, which includes N49, contains several blue giants in the LMC, two of which deserve further study.Paper presented at the International Gamma-Ray Burst Symposium, Toulouse, France 26–28 November, 1979.Cerro Tololo Inter-American Observatory, which is supported by the National Science Foundation under contract No. AST 74-04128.     

Gamma-ray bursts observed from the Hinotori satellite

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.     

The NASA/Marshall Space Flight Center program in gamma-ray burst astronomy

The research program in gamma-ray burst astronomy at the NASA/Marshall Space Flight Center is described. Large-area scintillation detector arrays have been flown on high-altitude balloons, and an array is being developed for the Gamma-Ray Observatory. The design of these detectors is described along with results obtained from previous balloon flights.Paper presented at the International Gamma-Ray Burst Symposium, Toulouse, France, 26–28 November, 1979.     

Advances in gamma-ray burst astronomy

Work at Goddard is preséntly being carried out in three major areas of gamma-ray burst research: (1) A pair of simultaneously operating 0.8-m² burst detectors were successfully balloon-borne at locations 800 miles apart on 9 May, 1975, each to atmospheric depths of 3 to 4 g cm^–2, for a 20-h period of coincident data coverage. This experiment investigates the size spectrum of bursts in the 10^–7 to 10^–6 erg cm^–2 size region where dozens of events per day are expected on a –1.5 index integral power-law extrapolation. Considerable separation in latitude was used to avoid possible atmospheric and auroral secondary effects. Its results are not yet available. This experiment is the sequel to a single balloon flight in May 1974, in which candidate events were found to fit the –1.5 spectral extrapolation, indicating the need for positive event identification. (2) A deep-space burst detector, the first spacecraft instrument built specifically for gamma-ray burst studies, was recently successfully integrated into the Helios-B space probe. Its use at distances of up to 2 AU will make possible the first high-resolution directional study of gamma-ray burst source locations. Similar modifications to several other space vehicles are also being prepared. (3) Our gamma-ray instrument on the IMP-7 satellite is presently the most sensitive burst detector still operating in orbit. Its results have shown that all measured event-average energy spectra are consistent with being alike. Using this characteristic spectrum to select IMP-7 candidate events of smaller size than those detected using other spacecraft in coincidence, a size spectrum is constructed which fits the –1.5 index power law down to 2.5×10^–5 erg cm^–2 per event, at an occurrence rate of about once per month.Paper presented at the COSPAR Symposium on Fast Transients in X-and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975.     

γ射线暴的研究进展（Ⅲ）：GRO的最新观测结果及理论模型

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。     

The high altitude observatory of the national center for atmospheric research Boulder,Colorado

Summary The High Altitude Observatory attempts to carry out a balanced program of theoretical and experimental research in solar, solar-terrestrial, and stellar-related physics. The scientific efforts are carried out within a sectional structure including the major areas of Solar Atmosphere and Magnetic Fields, Coronal/Interplanetary Physics, and Solar Variability. As one division of a National Center, the Observatory attempts to provide leadership through operation and sponsorship of seminars on specialized topics and organization of workshops to exploit data collections. In addition to the examples given, the Observatory, under NASA sponsorship, has organized a workshop series on solar flares, a central theme of which was the interpretation of Skylab results. This effort has resulted in the publication of a volume Solar Flares, edited by P. Sturrock, Colorado Associated University Press, 1979. Through these efforts, and the participation of individual staff members on advisory committees and working groups within the national and international framework, the Observatory continues to play a role in the guidance of research in solar and related physics.     

Searching for the host galaxy of GRB 920925C

GRB 920925C is probably the first cosmic gamma-ray burst with an optical afterglow detected from archival data. We present the results of our observations with the Shajn mirror telescope of the Crimean Astrophysical Observatory aimed at searching for the host galaxy at the afterglow location; we have determined the boundaries of distances to the possible host galaxy.     

Gamma-burst observations from the Pioneer Venus Orbiter

The LASL Pioneer Venus Orbiter Gamma Burst Detector (OGBD) is a vital element in the long base-line array of similar instruments intended to precisely locate sources of gamma-ray bursts. Results of early observations are described. The source of the gamma-ray burst of 5 March, 1979 (the first to be located with precision) has been determined to be consistent with the direction of supernova remnant N49 within the LMC. Approximate locations defined for a small number of events suggest no departure from an isotropic distribution.Paper presented at the Symposium on Cosmic Gamma-Ray Bursts held at Toulouse, France, 26–29 November 1979.     

A type IV burst associated with a coronal streamer disruption event

A type IV burst was observed on February 17, 1985 with the Clark Lake Radio Observatory multifrequency radioheliograph operating in the frequency range 20–125 MHz. This burst was associated with a coronal streamer disruption event. From two-dimensional images produced at 50 MHz, we show evidence of a type II burst and a slow moving type IV burst. The observations of the moving type IV burst suggests that a plasmoid containing energetic electrons can result from the disruption of a coronal streamer.Proceedings of the Second CESRA Workshop on Particle Acceleration and Trapping in Solar Flares, held at Aubigny-sur-Nère (France), 23–26 June, 1986.     

Studies on post-flare loop prominence of 1981 April 27

By use of the H observations of the Astrophysical Observatory in Catania, Italy and the Purple Mountain Observatory in Nanking, China as well as hard X-ray and gamma-ray burst data from the Solar Maximum Mission (SMM) Gamma-Ray Spectrometer (GRS), a major eruptive loop prominence was studied during the limb solar flare event of 1981 April 27.Our preliminary analysis shows that there seems to exist a second abrupt energy release for this event, almost 20 min after the end of the impulsive phase of the flare. This energy release is probably associated with the rapidity in upward motion or activation of the loop prominence.A possible candidate for such a process could be the reconnection of the old magnetic field with a newly emerging magnetic field.A theoretical gross estimate for the energy release and particle acceleration has also been made in this work. It appears that the proposed model for charged particle acceleration is very efficient.     

On the complex spatial structure of a gradual microwave burst

We present a discussion of the gradual burst event on May 13,1985 which is based on observations of the RATAN-600 telescope at ten fixed frequencies in the range between 37.5 and 0.95 GHz (0.8 and 31.6 cm wavelength) and on time profiles of patrol observations of the Observatory for Solar Radio Astronomy at Tremsdorf near Potsdam. This up to now most complete data set allows new conclusions on the extended spectral/spatial structure of the source region.There is strong evidence that only less than 24% of the microwave flux from this event is emitted by an excessive small-scale burst source while the bulk of the burst emission comes from a larger region consisting of two major components covered by the source area of the S-component radiation. The different components of the burst and S-component radiation are analyzed.     

Analysis of COMPTEL gamma-ray burst locations and spectra

In its first three years of operation, the COMPTEL instrument on theCompton Gamma-Ray Observatory has measured the locations (mean accuracy 1°) and spectra (0.75-30 MeV) of 18 gamma-ray bursts and continues to observe new events at a rate of 1/month. With good angular resolution and sensitivity at MeV energies, the growing COMPTEL burst catalog is an important new piece of evidence in the on-going GRB mystery. The COMPTEL burst locations are consistent with an isotropic distribution of sources, yet the spatial coincidence of two of the bursts indicates the possibility of repetition. The COMPTEL burst spectra are in most cases consistent with a single power law model with spectral index in the range 2–3. However, two bursts show evidence of a spectral break in the MeV range. Measurement of rapid variability at MeV energies in the stronger bursts provides evidence that either the sources are nearby (within the Galaxy) or the gamma-ray emission is relativistically beamed. We present an overview of analysis results obtained from the COMPTEL burst catalog concentrating on the search for burst repetition and the implications of highly variable MeV emission.     

Spectral characterisation of gamma-ray bursts with COMPTEL and BATSE

Although the earliest observed gamma-ray burst spectra were well described by thermal bremsstrahlung models, subsequent observations above 1 MeV showed the existence of high energy power law tails in 60% of events. In order to accurately characterise burst spectra, both the low energy turnover and the high energy tail must be accounted for. We have addressed this issue by jointly deconvolving spectra obtained by BATSE and COMPTEL onboard theCompton Observatory. We present preliminary results obtained by application of this method to the gamma-ray burst of February 17, 1994.     

The LASL gamma-ray burst astronomy program

Gamma-ray burst observations performed by LASL began with the identification and initial report of the phenomenon from data acquired by the Vela satellites. The Vela instruments have recorded responses to 73 gamma-ray bursts over a ten-year interval, and are continuing to contribute toward these observations. Similar instrumentation was included aboard the NRL SOLRAD 11 spacecraft. These performed well but suffered an early demise. Recently, the LASL gamma-ray burst astronomy program has been enhanced through the implementation of experiments aboard the Pioneer Venus Orbiter and ISEE-C spacecraft. Both of these experiments are continuing to contribute data vital to trigonometric directional analyses.Paper presented at the Symposium on Cosmic Gamma-Ray Bursts, held at Toulouse, France, 26–29 November, 1979.     

A large proton event associated with solar filament activity

We report observations made from several interplanetary spacecraft, of the large low-energy particle event of 23–27 April, 1979 associated with solar filament activity. We discuss the intensity, spectral and directional evolution of the event as observed in the energy range 35–1600 keV on ISEE-3, located ～ 0.99 AU from the Sun upstream of the Earth. We demonstrate that the shock disturbance propagating through the interplanetary medium and observed at ISEE-3 on 24/25 April strongly controls the particle event. From a comparison of the ISEE-3 observations with those on other spacecraft, in particular on Helios-2, located at 0.41 AU heliocentric distance near the Sun-Earth line, we identify the solar filament erupting on late 22 April near central meridian as the trigger for the propagating shock disturbance. This disturbance which comprises a forward shock and a reverse shock at the orbit of ISEE-3 is found to be the main source of the energetic proton population observed.     

Observations and comments for the solar event of 24 October, 1969

Observations of the flare of October 24, 1969 by Zirin et al. (1971) Solar Phys. 19, 463, are given with accompanying graphs of XUV emissions from satellites and four microwave radio emissions from Sagamore Hill Observatory. This event provides an excellent example of the development of two types of radio spectra within the same center and similar profiles for the hard X-ray burst and the 8800 MHz radio profile. The examination of the 2700 MHz burst from the Dominion Radio Astrophysical Observatory provides a clarification of the radio profile and shows the existence of a long enduring burst not previously considered. This event parallels a similar variation of intensity in the soft X-ray burst.     

Solar radio pulsating structures during September 9, 2001 at meter wavelength

Pulsating structures recorded at 237 MHz that are associated to decimetric continuum enhancement during the September 9, 2001 solar radio burst are described. We analyzed the radiopolarimetric data recorded at the Trieste Solar Radio System (INAF—Trieste Astronomical Observatory—Basovizza Observing Station) with very high time resolution (1 ms) at metric frequencies. Two different types of pulsations that occur in about 4 minutes at the same frequency are described. The possible mechanisms are analyzed and some parameters of the associated magnetic structure are estimated.     

Periodicities in gamma-ray bursts

One of the most recent discoveries on gamma-ray bursts was the fact that one, or possibly two, of them had a pulsed emission with a periodicity of 8 and 4 s. The intensity of successive peaks decreased exponentially with time. We can speculate that the energy range and/or the lack of sensitivity are probably the reasons why periodicities were not discoverded in some other bursts. In fact, many time-histories show a double or multiple peak structure. If they were periodic, the distance between successive peaks would be equal to the period. Based on this extremely simplified assumption, a search on all available gamma-ray burst time-histories shows that most the periodicities above 1 s should be contained within an interval between 1 and 9 s, with a maximum at approximately 3 s.Paper presented at the Symposium on Cosmic Gamma-Ray Bursts held at Toulouse, France, 26–29 November, 1979.     

Electron groups traced from the sun to 1 AU

We trace electrons from the Sun by a variety of proxy methods - solar flare positions, and metric and kilometric type III radio bursts from the Sun until they can be observed in situ as electrons at the ISEE-3 spacecraft. Our study extends over the period of operation of the electron experiment on ISEE-3 from August 1978 to November 1979. By carefully restricting timing within the data sets involved, we find a peak in the number of flares associated with in situ electrons near 60° west solar longitude. This peak shows that type III bursts can be fairly limited in spatial extent, and that the best connection with the solar surface to the flare is along the Archimedean magnetic field spiral. We use this spatial determination to define an average beam shape for an event. We assume this average beam shape to be representative of the distribution in space of each electron group. The electron numbers at 2 and 29–45 keV energies combined with this average beam shape are used to approximate the total numbers of electrons and energy per burst for individual events. We find that the total number of electrons and total energy for events varies significantly with flare type; that on the average brighter flares are associated with more electrons.     

Searching for very-high-energy gamma-ray bursts from evaporating primordial black holes

Temporal and energy characteristics of the very-high-energy gamma-ray bursts from evaporating primordial black holes have been calculated by assuming that the photospheric and chromospheric effects are negligible. The technique of searching for such bursts on shower arrays is described. We show that the burst time profile and the array dead time should be taken into account to interpret experimental data. Based on data from the Andyrchy array of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences), we have obtained an upper limit on the number density of evaporating primordial black holes in a local region of space with a scale size of ～10^?3 pc. Comparison with the results of previous experiments is made.