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Search Results: 1 - 10 of 360113 matches for " L. G. Balazs "
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Anisotropy of the sky distribution of gamma-ray bursts
L. G. Balazs,A. Meszaros,I. Horvath
Physics , 1998,
Abstract: The isotropy of gamma-ray bursts collected in Current BATSE catalog is studied. It is shown that the quadrupole term being proportional to $\sim \sin 2b \sin l$ is non-zero with a probability 99.9%. The occurrence of this anisotropy term is then confirmed by the binomial test even with the probability 99.97 %. Hence, the sky distribution of all known gamma-ray bursts is anisotropic. It is also argued that this anisotropy cannot be caused exclusively by instrumental effects due to the nonuniform sky exposure of BATSE instrument. Separating the GRBs into short and long subclasses, it is shown that the short ones are distributed anisotropically, but the long ones seem to be distributed still isotropically. The character of anisotropy suggests that the cosmological origin of short GRBs further holds, and there is no evidence for their Galactical origin.
Survival analysis of the Swift optical transient data
L. G. Balazs,I. Horvath,Zs. Bagoly,A. Meszaros
Physics , 2009, DOI: 10.1393/ncb/i2007-10282-1
Abstract: In a systematic search of the OTs at GRBs the Swift satellite determined only an upper limit of the apparent brightness in a significant fraction of cases. Combining these upper limits with the really measured OT brightness we obtained a sample well suited to survival analysis. Performing a Kaplan-Meier product limit estimation we obtained an unbiased cumulative distribution of the V visual brightness. The lg(N(V)) logarithmic cumulative distribution can be well fitted with a linear function of V in the form of lg(N(V))= 0.234 V + const. We studied the dependence of V on the gamma ray properties of the bursts. We tested the dependence on the fluence, T90 duration and peak flux. We found a dependence on the peak flux on the 99.7% significance level.
An intrinsic anisotropy in the angular distribution of gamma-ray bursts
L. G. Balazs,A. Meszaros,I. Horvath,R. Vavrek
Physics , 1999, DOI: 10.1051/aas:1999290
Abstract: The anisotropy of the sky distribution of 2025 gamma-ray bursts (GRBs) collected in Current BATSE catalog is confirmed. It is shown that the quadrupole term being proportional to $\sim \sin 2b \sin l$ is non-zero with a probability 99.9%. The occurrence of this anisotropy term is then supported by the binomial test even with the probability 99.97%. It is also argued that this anisotropy cannot be caused exclusively by instrumental effects due to the non-uniform sky exposure of BATSE instrument; there should exist also some intrinsic anisotropy in the angular distribution of GRBs. Separating GRBs into short and long subclasses, it is shown that the 251 short ones are distributed anisotropically, but the 681 long ones seem to be distributed still isotropically. The 2-sample Kolmogorov-Smirnov test shows that they are distributed differently with a 98.7% probability. The character of anisotropy suggests that the cosmological origin of short GRBs further holds, and there is no evidence for their Galactical origin. The work in essence contains the key ideas and results of a recently published paper (\cite{balazs}), to which the new result following from the 2-sample Kolmogorov-Smirnov test is added, too.
Comparing the observed properties of the GRBs detected by the Fermi and Swift satellites
L. G. Balazs,I. Horvath,Z. Bagoly,J. Kobori
Physics , 2013,
Abstract: We studied the distribution of the GRBs, observed by the Fermi satellite, in the multidimensional parameter space consisting of the duration, Fluence, Peak flux and Peak energy (if it was available). About 10% of the Fermi bursts was observed also by the Swift satellite. We did not find significant differences between the Peak flux and Peak energy of GRBs observed and not observed also by the Swift satellite. In contrast, those GRBs detected also by the Swift satellite had significantly greater Fluence and duration. We did a similar study for the GRBs detected by the Swift satellite. About 30% percent of these bursts was also measured by the Fermi satellite. We found a significant difference in the Fluence, Peak flux and Photon index but none in duration. These differences may be accounted for the different construction and observing strategy of the Fermi and Swift satellites.
SWIFT and BATSE bursts' classification
I. Horvath,Z. Bagoly,L. G. Balazs,G. Tusnady,P. Veres
Physics , 2009,
Abstract: Two classes of gamma-ray bursts were identified in the BATSE catalogs characterized by their durations. There were also some indications for the existence of a third type of gamma-ray bursts. Swift satellite detectors have different spectral sensitivity than pre-Swift ones for GRBs. Therefore in this paper we analyze the bursts' duration distribution and also the duration-hardness bivariate distribution, published in The First BAT Catalog. Similarly to the BATSE data, to explain the BAT GRBs' duration distribution three components are needed. Although, the relative frequencies of the groups are different than they were in the BATSE GRB sample, the difference in the instrument spectral sensitivities can explain this bias in a natural way. This means theoretical models may have to explain three different type of gamma-ray bursts.
Different satellites - different GRB redshift distributions?
Z. Bagoly,L. G. Balazs,I. Horvath,J. Kelemen,A. Meszaros,P. Veres,G. Tusnady
Physics , 2008, DOI: 10.1063/1.3027895
Abstract: The measured redshifts of gamma-ray bursts (GRBs), which were first detected by the Swift satellite, seem to be bigger on average than the redshifts of GRBs detected by other satellites. We analyzed the redshift distribution of GRBs triggered and observed by different satellites (Swift[1], HETE2[2], BeppoSax, Ulyssses). After considering the possible biases significant difference was found at the p = 95.70% level in the redshift distributions of GRBs measured by HETE and the Swift.
Analysis of the Swift Gamma-Ray Bursts duration
I. Horvath,L. G. Balazs,Z. Bagoly,J. Kelemen,P. Veres,G. Tusnady
Physics , 2009, DOI: 10.1063/1.3027961
Abstract: Two classes of gamma-ray bursts have been identified in the BATSE catalogs characterized by durations shorter and longer than about 2 seconds. There are, however, some indications for the existence of a third type of burst. Swift satellite detectors have different spectral sensitivity than pre-Swift ones for gamma-ray bursts. Therefore it is worth to reanalyze the durations and their distribution and also the classification of GRBs. Using The First BAT Catalog the maximum likelihood estimation was used to analyzed the duration distribution of GRBs. The three log-normal fit is significantly (99.54 % probability) better than the two for the duration distribution. Monte-Carlo simulations also confirm this probability (99.2 %).
Model Independent Methods of Describing GRB Spectra Using BATSE MER Data
P. Veres,I. Horvath,Z. Bagoly,L. G. Balazs,A. Meszaros,G. Tusnady,F. Ryde
Physics , 2010, DOI: 10.1393/ncb/i2007-10331-9
Abstract: The Gamma Ray Inverse Problem is discussed. Four methods of spectral deconvolution are presented here and applied to the BATSE's MER data type. We compare these to the Band spectra.
Combined Swift BAT-XRT Lightcurves
P. Veres,Z. Bagoly,J. Kelemen,I. Horvath,L. G. Balazs,A. Meszaros,G. Tusnady
Physics , 2009, DOI: 10.1063/1.3155948
Abstract: In this paper we make an attempt to combine the two kinds of data from the Swift-XRT instrument (windowed timing and photon counting modes) and the from BAT. A thorough desription of the applied procedure will be given. We apply various binning techniques to the different data: Bayes blocks, exponential binning and signal-to-noise type of binning. We present a handful of lightcurves and some possible applications.
Factor analysis of the spectral and time behavior of long GRBs
Z. Bagoly,L. Borgonovo,I. Horvath,A. Meszaros,L. G. Balazs
Physics , 2009, DOI: 10.1063/1.2943515
Abstract: A sample of 197 long BATSE GRBs is studied statistically. In the sample 11 variables, describing for any burst the time behavior of the spectra and other quantities, are collected. The application of the factor analysis on this sample shows that five factors describe the sample satisfactorily. Both the pseudo-redshifts coming from the variability and the Amati-relation in its original form are disfavored.
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