**AAS 195th Meeting, January 2000**

*Session 29. Gravitational Lensing, Relativistic Astrophysics and Gamma Ray Bursts*

Oral, Wednesday, January 12, 2000, 2:00-3:30pm, Regency VII
[Previous] |
[Session 29] |
[Next]

## [29.07] Constraining the Luminosity Function of GRBs from Time Dilation, Brightness Distribution and Redshift Data

*M. Deng, B. Schaefer (Yale University)*

We constrain the luminosity function of gamma ray bursts
(GRBs) by testing several cosmological models versus a
combination of (1) observed time dilation in the
peak-to-peak time scales of GRB light curves, (2) the Log N
- Log P number counts relation, and (3) GRB luminosities
directly determined from recent redshift measurements and
apparent GRB brightness. A power law luminosity function
\phi(L) = C \cdot L^{-\beta} (L_{min} < L < L_{max}) is
examined within three cosmological models, with cosmological
parameters (\Omega_{0}, \Omega_{\Lambda}) = (1.0, 0.0),
(0.3, 0.0), or (0.3, 0.7). It is found that GRB models with
constant comoving density rate do not fit the data while
models with GRB density evolution tracing the observed star
formation rate can accomodate all the observed data. The
width K = L_{max} / L_{min} of the luminosity function is
found to be K > 100 at the 1 \sigma level, while the
average luminosity is found to be 4 ±2 \times
10^{51} ergs \cdot s^{-1} at the 3 \sigma level, this
implies that bursts at the BATSE 100 % efficiency threshold
have typical red shifts of 0.42> = 2.7 ±0.5.

[Previous] |
[Session 29] |
[Next]