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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 class. 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. We analyze, the maximum likelihood estimation, the bursts duration distribution, published in The First BAT Catalog, whether it contains two, three or more groups. 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%). Similarly, in previous results we found that the fourth component is not needed. The relative frequencies of the distribution of the groups are 7% short 35% intermediate and 58% long. Although the relative frequencies of the groups are different than in the BATSE GRB sample, the difference in the instrument spectral sensitivities can explain this bias on a natural way. This means theoretical models may be needed to explain three different type of gamma-ray bursts.
The Fermi GBM Catalog has been recently published. Previous classification analyses of the BATSE, RHESSI, BeppoSAX, and Swift databases found three types of gamma-ray bursts. Now we analyzed the GBM catalog to classify the GRBs. PCA and Multiclusteri
Recent Swift observations suggest that the traditional long vs. short GRB classification scheme does not always associate GRBs to the two physically motivated model types, i.e. Type II (massive star origin) vs. Type I (compact star origin). We propos
It is now more than 40 years since the discovery of gamma-ray bursts (GRBs) and in the last two decades there has been major progress in the observations of bursts, the afterglows and their host galaxies. This recent progress has been fueled by the a
(Shortened) We show by example how the uncoding of Gamma-Ray Bursts (GRBs) offers unprecedented possibilities to foster new knowledge in fundamental physics and in astrophysics. After recalling some of the classic work on vacuum polarization in unifo
Many theories of dark matter (DM) predict that DM particles can be captured by stars via scattering on ordinary matter. They subsequently condense into a DM core close to the center of the star and eventually annihilate. In this work, we trace DM cap