Compatibility of the BATSE Gamma-Ray Burst Data with General Friedmann Cosmological Models
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**Session 15 -- Gamma Ray Bursts**
*Oral presentation, Monday, 30, 1994, 10:00-11:30*

## [15.07] Compatibility of the BATSE Gamma-Ray Burst Data with General Friedmann Cosmological Models

*A. G. Emslie (UAH), and J. M. Horack (NASA/MSFC)*

We have used a technique based on analysis of normalized integral moments
to test the compatibility of various Friedmann cosmological models (including
those which admit a cosmological constant $\Lambda$) with the intensity
distribution of gamma--ray bursts observed by BATSE. We find that models
with a zero $\Lambda$ and a (typical) spectral index $\alpha$ = 2 are
consistent with the data only if the maximum redshift observed by BATSE is
less than 1.25. Higher limiting redshifts are possible only if the bursts
have a spectrum much flatter than typically observed, or if they are embedded
in a Universe with a positive $\Lambda$. Furthermore, the closer the actual
value of the maximum redshift to the limiting values derived, the narrower
must be the width of the luminosity distribution function for the bursts.
Coupled with a similar result for Euclidean geometries (see the paper by
Horack and Emslie elsewhere at this meeting), this result requires that if
gamma--ray bursts truly span a wide range of burst luminosities, then they
must not only be cosmological in origin, but also must be embedded in a
Universe with a positive cosmological constant.

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