Anisotropy of the sky distribution of gamma-ray bursts

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 of 99.9%. The occurrence of this anisotropy term is then confirmed by the binomial test even with the probability of 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

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

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 similar to sin 2b sin I 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 (Balazs et al. 1998), to which the new result following from the 2-sample Kolmogorov-Smirnov test is added, too

A Remarkable Angular Distribution of the Intermediate Subclass of Gamma‐Ray Bursts

We develop a method of testing the null hypothesis of intrinsic randomness in the angular distribution of gamma-ray bursts collected in the Current BATSE Catalog. The method is a modified version of the well-known counts-in-cells test and fully eliminates the nonuniform sky-exposure function of the BATSE instrument. Applying this method to the case of all gamma-ray bursts, we found no intrinsic nonrandomness. The test also did not find intrinsic nonrandomness for the short and long gamma-ray bursts. However, using the method on the new, intermediate subclass of gamma-ray bursts, the null hypothesis of intrinsic randomness for 181 intermediate gamma-ray bursts is rejected on the 96.4% confidence level. Taking 92 dimmer bursts from this subclass, we obtain a surprising result: this "dim" subclass of the intermediate subclass has an intrinsic nonrandomness on the 99.3% confidence level. On the other hand, the 89 "bright" gamma-ray bursts show no intrinsic nonrandomness

An Observational Evidence for the Difference Between the Short and Long Gamma-Ray Bursts

The intrinsic fluence and duration distributions of gamma-ray bursts are well represented by log-normal distributions. This allows a bivariate log-normal distribution fit to be made to the BATSE short and long bursts separately. A statistically significant difference between the long and short groups is found. We argue that the effect is probably real. Applying the Cramér’s theorem these results lead to some predictions for models of long and short bursts

Fejezetek a magyarországi csillagászat történetéből = Selected topics on the history of astronomy in Hungary

Az 1572. évi szupernóva: Kimutattuk, hogy az új csillag komoly politikai mondandót hordozott a kortársak számára. Jacob Schnitzler nagyszebeni csillagász tevékenysége: Megvizsgáltuk a vele kapcsolatos nyomtatványok szerzőségét: tizenhatot maga írt, hetet az adott elnök, egy pedig a barátai és professzorai által hozzá írt üdvözlő verseket tartalmazza. A nagyszombati jezsuiták csillagokról való ismereteinek vizsgálata: Megmutattuk, hogy Mária Terézia 1753-as rendelete után a megjelent könyvek és tézisek színvonala nagyot nőtt, a csillagokat most már a kornak megfelelően definiálták. John Herschel, a Hold és Magyarország: Foglalkoztunk John Herschel 1835-ben tett délafrikai útja kapcsán felröppent hírlapi kacsa magyarországi hatásával. Szathmári Ákos életének és munkásságának tanulmányozása: az első volt, aki Magyar-országon könyvet adott ki a spektroszkópiáról Kövesligethy Radó elméleti asztrofizikai munkássága: Levéltári kutatásokkal gyűjtött újabb adatok felhasználásával elkészítettük Kövesligethy Radó életrajzát. Megmutattuk, hogy Kövesligethy Radó levezetett egy spektrál-egyenletet, amelyben a sugárzás spektrális eloszlása csak a hőmérséklettől függ, a teljes hullámhossz tartományban a kisugárzott energia véges (ezzel 15 évvel megelőzte Max Planckot). Wilhelm Wien előtt 8 évvel felfedezte az eltolódási törvényt. Elsőként adott elméleti magyarázatot a hidrogén színképét leíró Balmer formulára. | The Supernova of 1572: we showed that the new star made an important political message for the contemporaries. Activity of Jacob Schitzler, astronomer of Nagyszeben: we studied the authorship of the printed documents related to him: we found that 16 was written by him 7 by the actual presidents and one contains the poems written to him by his friends and professors. Study the knowledge of the Jesuits of Nagyszombat on the stars: we showed that after the decree of Maria Theresia the standard of the books and theses increased significantly, the definition of the stars was already in accordance with the era. John Herschel, the Moon and Hungary: we studied the effect of the well-known 'Great Moon Hoax' in Hungary published in connection with the trip of John Herschel in South Africa in 1835. Study of Ákos Szathmári's life and work: he was the first in Hungary who published a book on spectroscopy. Radó Kövesligethy's work on theoretical astrophysics: based on new data collected by researches in archives we completed Kövesigethy's biography. We showed that Radó Kövesligethy derived a spectral equation where the spectral distribution depends only on the temperature and the irradiated energy is finite in the whole wavelength range (he preceded Max Planck with 15 years). He discovered the displacement law 8 years before Wilhelm Wien. He was the first who gave a theoretical explanation for Balmers' law of the Hydrogen spectrum

Sky Distribution of Gamma-Ray Bursts: an Observational Test of the Friedmannian Universe Models

If the Universe is described by the Friedmannian model, then the objects located at redshifts larger than z similar or equal to 0.1 should be distributed isotropically on the sky. In order to fulfil the Cosmological Principle for these redshifts, the objects should be distributed homogeneously and isotropically. Various statistical isotropy tests are surveyed. Spherical tesselation, graph theoretical and multiscale methods are used to test the intrinsic isotropy of GRBs. The long gamma-ray bursts being at these redshifts - show the isotropy; however, the conclusion is not decisive yet. Contrary to this, the short and intermediate bursts are not distributed isotropically; however, the redshifts are not known for these objects yet