摘要:

We consider here the spectra produced from the resonant Compton scattering of blackbody and power‐law photons by a beam of relativistic electrons/positrons. The beam is assumed to be directed radially outward along the magnetic axis of a highly magnetized neutron star. We assume a dipole magnetic field geometry, and include the effects of magnetic Compton scattering energy losses on the particles in the beam during transport. A range of surface intensities for a magnetic field of 2×1012Gauss is studied for a power‐law electron/positron source function of index &Ggr;. The calculated scattered photon spectra are similar to observed gamma‐ray burst spectra with a spectral index &agr; which breaks from &agr;&bartil;1 to &Agr;&bartil;&Ggr;.

ISSN:0094-243X    

DOI:10.1063/1.42840

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We present results from a study of 37 multiple event gamma ray bursts found in the monitoring data of the PVO gamma ray burst detector. We define these bursts as those which have two or more distinct emission events separated by a return to the background intensity. Significant correlation exists between the duration of the first event and the duration of the second event, while some correlation exists between the hardness of the events and only weak correlation exists in the intensity of the events. Although the time profiles of events in a burst may be similar, as measured in the phase portrait, there is no general rule about the degree of similarity of the time profiles. Subdividing the data according to the recurrence time, we find a tendency for the strength of the correlation in the hardness to increase with decreasing separation between the events.

ISSN:0094-243X    

DOI:10.1063/1.42795

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Most cosmic gamma‐ray burst temporal profiles appear to be comprised of several individual pulses, many of which overlap. It is advantageous to deconvolve the temporal structures into their constituent pulses, and thereby investigate the shape, intensity and temporal distributions of the pulses as a function of energy. Such fundamental pulse descriptors would provide constraints for theoretical modeling of the burst emission process, such as indications of source size, optical depth and geometry as a function of time. We have developed a deconvolution algorithm which treats sequences of pulse shapes that change deterministically. The algorithm, a generalization of autoregressive techniques, has been applied to a few bright bursts observed by BATSE. Results indicate that, even within short intervals, constituent pulses are not self‐similarly shaped, nor do pulse shapes evolve in a simple manner throughout a burst. Hence, the direction of our future work on pulse deconvolution will focus on analysis methods which allow pulse shape to vary.

ISSN:0094-243X    

DOI:10.1063/1.42797

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Several gamma‐ray bursts in the BATSE data have sufficiently long durations and complex temporal structures with pulses that appear to be spaced quasi‐periodically. In order to test and quantify these periods we have applied fast Fourier transformations (FFT) to all these events. We have also performed cross spectral analyses of the FFT of the two extreme (high‐low) energy bands in each case to determine the lead/lag of the pulses in different energies.

ISSN:0094-243X    

DOI:10.1063/1.42798

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

During 28 months of operation, the French‐Soviet PHEBUS experiment onboard GRANAT has recorded a total of 66 cosmic &ggr;‐ray bursts (GRBs). We observe that events lasting less than 2 seconds exhibit harder spectra both on average and at the maximum peak. Their peculiar spectral shape and their similarities in time history claim in favor of the existence of a separate class of short cosmic &ggr;‐ray bursts.

ISSN:0094-243X    

DOI:10.1063/1.42799

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A cursory examination of cosmic gamma‐ray burst time profiles indicates an inhomogeneous distribution of structure. In the first approximation, there seem to be two types of profiles; smooth ones with little structure and highly variable ones with lots of structure. To put this observation to the test, we have examined the statistical nature of the profile derivative to choose which parameter might best be called the burst ‘‘spikiness.’’ We have found that a good estimator is given by a count of the number of ‘‘spikes’’ (defined by a specific numerical recipe) and not by the rms deviations from either a pre‐burst background or any type of moving average background. The application of this parameter to 30 burst time histories shows it to be consistent over a wide range of profile types. The analysis also reveals a preferred average time between spikes of approximately 1.5 seconds.

ISSN:0094-243X    

DOI:10.1063/1.42800

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.42801

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The present status of searches for flashing optical counterparts to gamma ray burst sources is given. Programs run at the Ondr˘ejov Observatory are presented and briefly discussed.

ISSN:0094-243X    

DOI:10.1063/1.42802

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

This status report will present some details on the project ‘‘Search for time‐correlated optical counterparts of &ggr;‐ray bursters.’’ The photographic sky patrol of the three observatories Sonneberg (FRG), Ondr˘ejov (SCFR) and Odessa (USSR) is used to look for patrol plates which have been exposed simultaneously with a &ggr;‐ray burst detected by GRO. Our expectation and the very first results are presented.

ISSN:0094-243X    

DOI:10.1063/1.42803

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We are investigating the ROSAT all‐sky survey data for all gamma‐ray burst localizations of size less than 1 deg2. These sources may have been observed by ROSAT either after or before the burst itself. We present here a status report on this work, and its capability to constrain the spatial distribution of GRBs.

ISSN:0094-243X    

DOI:10.1063/1.42805

出版商:AIP    

年代:1991

数据来源: AIP