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Astron. Astrophys. Suppl. Ser. 138, 515-516

Time dilation and the star formation scenario

M. Deng - B.E. Schaefer

Department of Physics, Yale University, New Haven, CT 06520-8120, U.S.A.

Received December 8, 1998; accepted June 16, 1999


We investigate the dependence of the redshift vs. brightness relation of GRBs upon the width of GRB luminosity function and the cosmological models. The relation is then fit to our observed time dilation data of GRBs. It is found that the best fit average luminosity ranges from $L_{0}
= 1.1 \pm 0.3 \ 10^{57}\ {\rm photons} \ {\rm s}^{-1}$ in a standard candle luminosity model to $<L\gt\, = 8.7 \pm 3.6 \ 10^{57}\ {\rm photons}
{\rm s}^{-1}$ in a cosmological model with a broad luminosity function $\phi(L)
= C \cdot L^{-\beta}$. Our fits suggest that it is only possible to accomodate the large distance scale suggested by the Star Formation Rate model when the luminosity function has a large width $K \sim 1000$ in a cosmological model with low matter density $\Omega_{0}$.

Key words: gamma-rays: bursts

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