CONSTRAINTS ON GALACTIC DISTRIBUTIONS OF GAMMA-RAY BURST SOURCES FROMBATSE OBSERVATIONS

The paradigm that gamma-ray bursts originate from Galactic sources is studied in detail using the angular and intensity distributions observ ed by the Burst and Transient Source Experiment (BATSE) on NASA's Comp ton Gamma Ray Observatory (CGRO). Monte Carlo models of gamma-ray burs t spatial distributions and luminosity functions are used to simulate bursts, which are then folded through mathematical models of BATSE sel ection effects. The observed and computed angular intensity distributi ons are analyzed using modifications of standard statistical homogenei ty and isotropy studies. Analysis of the BATSE angular and intensity d istributions greatly constrains the origins and luminosities of burst sources. In particular, it appears that no single population of source s confined to a Galactic disk, halo, or localized spiral arm satisfact orily explains BATSE observations and that effects of the burst lumino sity function are secondary when considering such models. One family o f models that still satisfies BATSE observations comprises sources loc ated in an extended spherical Galactic corona. Coronal models are limi ted to small ranges of burst luminosity and core radius, and the allow ed parameter space for such models shrinks with each new burst BATSE o bserves. Multiple-population models of bursts are found to work only i f (1) the primary population accounts for the general isotropy and inh omogeneity seen in the BATSE observations and (2) secondary population s either have characteristics similar to the primary population or con tain numbers -that are small relative to the primary population.