Xref: cantaloupe.srv.cs.cmu.edu sci.astro:35217 sci.space:61401 Path: cantaloupe.srv.cs.cmu.edu!das-news.harvard.edu!ogicse!netnews.nwnet.net!news.u.washington.edu!news.u.washington.edu!ethanb From: ethanb@ptolemy.astro.washington.edu (Ethan Bradford) Newsgroups: sci.astro,sci.space Subject: Re: Gamma Ray Bursters. WHere are they. Message-ID: Date: 28 Apr 93 21:51:46 GMT Article-I.D.: ptolemy.ETHANB.93Apr28135146 References: <1radsr$att@access.digex.net> <1rbl0eINNip4@gap.caltech.edu> <1993Apr27.132255.12653@tpl68k0.tplrd.tpl.oz.au> Organization: U. of Washington Lines: 59 NNTP-Posting-Host: kepler.astro.washington.edu To: steinly@topaz.ucsc.edu (Steinn Sigurdsson) In-reply-to: steinly@topaz.ucsc.edu's message of 27 Apr 93 12:14:43 In article steinly@topaz.ucsc.edu (Steinn Sigurdsson) writes: _The_ problem with Oort cloud sources is that absolutely no plausible mechanism has been proposed. It would have to involve new physics as far as I can tell. Closest to "conventional" Oort sources is a model of B-field pinching by comets, it's got too many holes in it to count, but at least it was a good try... So you have a plausible model for GRB's at astronomical distances? Recent observations have just about ruled out the merging neutron star hypothesis, which had a lot of problems, anyhow. We have to look for implausible models and what is fundamentally allowed independent of models. A paper on the possibility of GRB's in the Oort cloud just came through the astrophysics abstract service. To get a copy of this paper, send a message to astro-ph@babbage.sissa.it with the subject line get 9304001 Here is the abstract of that paper. The currently favored explanation for the origin of \GRBs puts them at cosmological distances; but as long as there is no distance indicator to these events all possible sources which are isotropically distributed should remain under consideration. This is why the Oort cloud of comets is kept on the list, although there is no known mechanism for generating \GRBs from cometary nuclei. Unlikely as it may seem, the possibility that \GRBs originate in the solar cometary cloud cannot be excluded until it is disproved. We use the available data on the distribution of \GRBs (the BATSE catalogue up to March, 1992), and the Catalogue of Cometary Orbits by Marsden and Williams (1992) to investigate whether there is any observational indication for correlations between the angular distributions of \GRBs and comets' aphelia, assuming that the distribution of aphelia direction reflect, at least to some extent, true variations in the column density of the Oort cloud. We also apply the $\vov$ test to both distributions. We have performed a variety of statistical tests (a Kolmogorov-Smirnov test for the distributions in galactic latitude, a $\chi^2$ test for the spherical multiple moments, and a 2-D cross-correlation analysis), including testing sub-samples for isolating the effect of possible observational biases. These tests imply that it is unlikely that the two distributions agree, but the statistical significance is not sufficient for ruling out any connection with complete confidence. We performed Monte-Carlo simulations which show that only when the number of bursts exceeds $\sim 800$ it is possible to rule out a correlation between the angular distributions. Currently, it is only the combination of these tests with the large disagreement found for the $\vov$ parameter which makes the Oort cloud of comets unlikely to be related to \GRBs.