1999/05/25 by J. T. Bonnell, J. P. Norris, Bonnell, J. T. +1
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9905319
13 pages, 4 figures, submitted to ApJ
arxiv created 1999/05/25 · openalex publication_date 1999/05/25 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The inhomogeneous brightness distribution of BATSE detected gamma-ray bursts has been considered strong evidence for their cosmological origin. However, subclasses of gamma-ray bursts have been shown to have significantly more homogeneous brightness distributions. Pendleton et al. (1997) have found such a result for gamma-ray bursts with no detectable emission at energies >300 keV. Accordingly, it has been suggested that these no high energy (NHE) emission bursts represent an underluminous population of nearby sources. A distinct homogeneous NHE brightness distribution has also been considered as evidence for beaming of different spectral components of the prompt burst emission. We synthesize observed distributions of gamma-ray bursts based on a sample of typical bright BATSE bursts with intrinsic high energy emission and adopt a single cosmological distance scale for all sources. We find that the resulting synthetic NHE bursts do indeed have a more nearly homogeneous intensity distribution when an appropriate decrease in signal to noise and redshifted spectrum is incorporated. We argue that the definition of NHE bursts, and soft-spectrum bursts in general, naturally produces a steep distribution. The NHE class of gamma-ray bursts is therefore likely due to brightness bias.