On the existence of the intrinsic anisotropies in the angular distributions of gamma-ray bursts

A. Mészáros, Z. Bagoly, R. Vavrek

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This article is concerned primarily with the intrinsic anisotropy in the angular distribution of 2281 gamma-ray bursts (GRBs) collected in Current BATSE Gamma-Ray Burst Catalog until the end of year 1998, and, second, with intrinsic anisotropies of three subclasses ("short", "intermediate", "long") of GRBs. Testing based on spherical harmonics of each class, in equatorial coordinates, is presented. Because the sky exposure function of BATSE instrument is not dependent on the right ascension a, any non-zero spherical harmonic proportional either to Pnm(sin δ) sin mα or to Pnm(sin δ) cos mα with m ≠ 0 (δ is the declination), immediately indicates an intrinsic non-zero term. It is a somewhat surprising result that the "intermediate" subclass shows an intrinsic anisotropy at the 97% significance level caused by the high non-zero P31(sin δ) sin α harmonic. The remaining two subclasses, and the full sample of GRBs, remain isotropic.

Original languageEnglish
Pages (from-to)1-6
Number of pages6
JournalAstronomy and Astrophysics
Issue number1
Publication statusPublished - Dec 1 2000



  • Cosmology: large-scale structure of Universe
  • Gamma rays: bursts

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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