What is the Astrophysical Meaning of the Intermediate Subgroup of GRBs?

Published articles concerning the intermediate (third) subgroup of GRBs are surveyed. From a statistical perspective this subgroup may exist, however its significance depends on which data set is used. Its astrophysical meaning is unclear because the occurrence of this subgroup can also be an artificial selection effect. Hence, GRBs from this subgroup need not be given by a physically different phenomenon. The aim of this contribution is to search for the answer to the question in the title.Comment: journal: Proceedings of Science, Swift: 10 Years of Discovery; conference date: 2-5 December 2014; location: La Sapienza University, Rome, Italy; 6 pages, 4 figures, 1 table; accepted for publication in July 9 201

A curious relation between the flat cosmological model and the elliptic integral of the first kind

The dependence of the luminosity distance on the redshift has a key importance in the cosmology. This dependence can well be given by standard functions for the zero cosmological constant. The purpose of this article is to present such a relation also for the non-zero cosmological constant, if the universe is spatially flat. A definite integral is used. The integration ends in the elliptic integral of the first kind. The result shows that no numerical integration is needed for the non-zero cosmological constant, if the universe is spatially flat.Comment: Accepted for publication in Astronomy & Astrophysics. 2 page

On the properties of the RHESSI intermediate-duration gamma-ray bursts

The intermediate-duration gamma-ray bursts (GRBs) identified in the data of the RHESSI satellite are investigated with respect to their spectral lags, peak count rates, redshifts, supernova observations, and star formation rates of their host galaxies. Standard statistical tests like Kolmogorov-Smirnov and Student t-test are used. It is discussed whether these bursts belong to the group of so-called short or long GRBs, or if they significantly differ from both groups.Comment: 4 pages, 4 figures, 2 table

On the relation between the non-flat cosmological models and the elliptic integral of first kind

Recently we have found an analytic integration formula that describes the dependence of the luminosity distance on the redshift for the flat cosmological model with a non-zero cosmological constant. The purpose of this article is to search for a similar relation for the non-flat models. A Taylor series was used. The elliptic integral of the first kind can indeed be applied. The result shows that a combination of the numerical integration with the previous analytic formula can also be useful for the nearly flat cosmological models.Comment: two pages, published in Astronomy & Astrophysics, Volume 573, A5