摘要:

Gamma-ray burst light curves contain a great deal of information that may help to solve the mystery concerning the origin of these bursts. We employ multifractal analysis techniques to quantify the variability of these light curves. We studied the correlation of variability with other burst parameters for long bursts (longer than 2 s). We present evidence that the correlation of variability and intensity provides evidence that our data are consistent with bursts at cosmological distances. No correlations with duration or location were found for the long bursts. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55322

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Linear State Space Modeling determines the hidden autoregressive (AR) process in a noisy time series; for an AR process the time series’ current value is the sum of current stochastic “noise” and a linear combination of previous values. We present preliminary results from modeling a sample of 4 channel BATSE LAD lightcurves. We determine the order of the AR process necessary to model the bursts. The comparison of decay constants for different energy bands shows that structure decays more rapidly at high energy. The resulting models can be interpreted physically; for example, they may reveal the response of the burst emission region to the injection of energy. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55324

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We present the results of searches for periodic pulsations in gamma-ray bursts detected by the Burst And Transient Source Experiment (BATSE) aboard the Compton Gamma Ray Observatory. A total of 20 bright bursts are examined. The durations of the TTE data used range from 0.065 s to 1.048 s. These data either cover the onset of a very bright burst or the whole short burst. The photon arrival data are time-tagged with a time resolution of 2 &mgr;s. We examined various energy channels and time segments in the data for pulsations with Fast Fourier Transforms. The periods searched cover the range from 0.016 to 33.3 ms. We find no significant evidence for periodic pulsations in the above range, and the upper limits for the pulsations are presented in terms of statistical probabilities and pulsed fractional amplitudes. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55325

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have carried out a detailed study of gamma-ray bursts (GRBs) with time duration less than 100 ms including: (1) a fast-Fourier spectrum analysis, (2) a comparison with the Stern analysis of longer bursts, and (3) a comparison of the properties of the short bursts. We have used the TTE data available to the public. We show that these bursts are very different from the rest of the GRB events. We also compare the bursts with a model of primordial black hole (PBH) evaporation at the quark-gluon phase (QGP) transition temperature. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55326

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Several statistical measures of small scale clustering have been proposed as measures of gamma-ray burst repetition. We compare the relative sensitivity of three of these statistics, including the effect of sky exposure on the burst repetition signal. We find that the best of the three statistics places an upper limit of 10&percent; on the number of observed repeater bursts in the BATSE 3B catalog for a model in which each repeating source produces 2 bursts. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55327

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have correlated the positions of 57 GRBs observed by WATCH-GRANAT and WATCH-EURECA with 1905 bursts detected by BATSE. Comparing the so called “added correlation” between the WATCH and BATSE bursts with that obtained with simulated WATCH catalogues, we conclude that there is no indication of recurrent activity of WATCH bursts in the BATSE sample. We derive a 94&percent; confidence level upper limit of 15.8&percent; for the number of WATCH GRBs that could represent a population of repeaters in the BATSE sample. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55428

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Revised upper limits on gamma-ray burst repetition rates are found using the BATSE 3B and 4B catalogs. A statistical repetition model is assumed in which sources burst at ameanrate but in which BATSE observes bursts randomly from each source. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55328

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We present preliminary results of an investigation of the temporal variability of gamma-ray bursts using Fourier analysis. Power density spectra were generated in the frequency range0<&ngr;⩽7.8125 Hzfor bursts recorded with the BATSE Large Area Detectors in the 50–300 keV range. Typical burst power spectra were found to consist of a low-frequency noise component and a white noise component consistent with Poisson statistics. The low-frequency noise was modeled by a power law, with index &agr;. We show that the distribution of power-law indices is asymmetric with the majority of events (∼65&percent;) having|&agr;|>2.The limitations of applying the Fourier transform to nonstationary GRB time series will be discussed in the context of the distribution of power-law indices. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55329

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Systematic time variations of duration, hardness and their correlation of gamma-ray bursts (GRBs) are revealed, which may indicate the existence of GRBs originating in the heliosphere. ©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55330

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We present evidence of time stretching in the peak-to-peak time scales in the light curves of BATSE gamma-ray bursts (GRBs). Extensive tests are performed on simulated samples of artificially dilated bursts to verify that the procedure for extracting the peak-to-peak intervals correctly recovers the input stretching of bursts. The resulting robust algorithm is then applied to the 4B GRB database. We derive a factor of1.92±0.13stretching between the bright burst group(P>7.7 photons cm−2 s−1)and the dimmest burst group(P=1.0−1.4 photons cm−2 s−1),which is a 7 &sgr; effect. This measurement strongly supports the interpretation of the observed time stretching as time dilation caused by the universal cosmological expansion. In the standard candle scenario, this result implies that the burst luminosity is7.0−2.0+2.0×1056 photons s−1,which suggests that the brightest bursts are at redshift ofzbright<0.2.©1998 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.55331

出版商:AIP    

年代:1998

数据来源: AIP