A. Mészáros

DETAILED CLASSIFICATION OF SWIFT 'S GAMMA-RAY BURSTS

Earlier classification analyses found three types of gamma-ray bursts (short, long, and intermediate in duration) in the BATSE sample. Recent works have shown that these three groups are also present in the RHESSI and BeppoSAX databases. The duration distribution analysis of the bursts observed by the Swift satellite also favors the three-component model. In this paper, we extend the analysis of the Swift data with spectral information. We show, using the spectral hardness and duration simultaneously, that the maximum likelihood method favors the three-component against the two-component model. The likelihood also shows that a fourth component is not needed.

Search for gamma-ray burst classes with the RHESSI satellite

A sample of 427 gamma-ray bursts (GRBs), measured by the RHESSI satellite, is studied statistically with respect to duration and hardness ratio. Standard statistical tests are used, such as

On the difference between the short and long gamma-ray bursts

\chi^2

A comparison of the gamma-ray bursts detected by BATSE and Swift

, F-test and the maximum likelihood ratio test, in order to compare the number of GRB groups in the RHESSI database with that of the BATSE database. Previous studies based on the BATSE Catalog claim the existence of an intermediate GRB group, besides the long and short groups. Using only the GRB duration

A DISTINCT PEAK-FLUX DISTRIBUTION OF THE THIRD CLASS OF GAMMA-RAY BURSTS: A POSSIBLE SIGNATURE OF X-RAY FLASHES?

T_{90}

Testing the randomness in the sky-distribution of gamma-ray bursts

as information and

The Swift satellite and redshifts of long gamma-ray bursts

\chi^2

A Principal Component Analysis of the 3B Gamma-Ray Burst Data

or F-test, we have not found any statistically significant intermediate group in the RHESSI data. However, maximum likelihood ratio test reveals a significant intermediate group. Also using the 2-dimensional hardness /

An intrinsic anisotropy in the angular distribution of gamma-ray bursts

T_{90}

Cosmological Evolution and Luminosity Function Effects on Number Counts, Redshift, and Time Dilation of Bursting Sources

plane, the maximum likelihood analysis reveals a significant intermediate group. Contrary to the BATSE database, the intermediate group in the RHESSI data-set is harder than the long one. The existence of an intermediate group follows not only from the BATSE data-set, but also from the RHESSI one.