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Angular Distribution of Gamma-Ray Bursts: An
Observational Probe of Cosmological Principle
Attila Meszaros et al.
Dept. of Astronomy, Charles University, Prague, Czech Republic
The test of the isotropy in the angular distribution of the gamma-
ray bursts collected in BATSE Catalog (Meegan C. A. et al.,
http://www.batse.msfc.nasa.gov/data, 2000) is a test of cosmo-
logical principle itself, because the gamma-ray bursts are at cos-
mological distances. Several articles of the authors study this
question (Balazs L. G., Meszaros A., & Horvath I., Astron. As-
trophys., 339, 1, 1998; Balazs L. G., Meszaros A., Horvath I., &
Vavrek R., Astron. Astrophys. Suppl., 138, 417, 1999; Meszaros
A., Bagoly Z., & Vavrek R. Astron. Astrophys., in press, 2000).
The nal conclusion concerning the validity of isotropy is compli-
cated both by instrumental eects and by the fact that there are
three subgroups of gamma-ray bursts ("short", "intermediate",
"long"; separation is done with respect to the duration of bursts).
The long bursts are surely up to z ' 4 (z is the redshift); for the
remaining two subclasses the redshifts are unknown. The done
tests of isotropy suggest (after the elimination of instrumental ef-
fects) the existence of anisotropy for the intermediate subclass on
the condence level > 95%. On the other hand, for the remaining
two subclasses the situation is unclear; there is no unambiguous
rejection of isotropy for them yet on the higher than 95% con-
dence level. If the bursts of intermediate subclass are at high
z-s (say, at, z > 0:1), then the validity of cosmological principle
would be at a serious doubt.
Co-authors: L.G. Balazs, R. Vavrek, I. Horvath, and Z. Bagoly
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