Monday, September 25, 2006

Giant Ruddy Bangs

Last week I was down in the big smoke of London attending the grand surroundings of the Royal Society. There was a discussion meeting on γ-Ray bursts - GRBs - (intense flashes of γ-rays seen from space), which I was going to. The discussion there was very topical with a lot of talks being about recent results from the Swift satellite, which was specifically designed to spot these GRBs and then quickly slew onto their location and look at the afterglows from the original burst. Observing these afterglows is the key to working out the underlying process which causes the burst. Now I'd heard that bursts where catagorised into two types, short and long duration, depending on how long the initial flash lasted, with short ones lasting ~< a few seconds, and long ones lasting up to a few hundred seconds. I also thought that current knowledge suggested that the short bursts where from the inspirals/merger of a pair of compact objects e.g. neutron star binaries or black hole - neutron star binaries, and long bursts where collapsars e.g. a supernova in which the ejected material can't escape and falls back onto collapsed core in an accretion disk. Turns out that things are far more complicated than this two category system! There are all sorts of differences seen in and between bursts currently catagorised within one or other of the systems - with differences in the energies of the initial bursts, short bursts looking like long bursts, afterglows being mysteriously absent etc. Obviously there's still a lot more to find out about these events, but at the moment there's just a lot of stamp collecting and building up enough events to start making better catagorisations and working out what's really going on. Are these bursts all from the same kind of underlying event but just seen differently (i.e. a viewing angle effect) or are they completely different kinds of things, like white-dwarf mergers rather than collapsars?! There's enough going on in the field to keep the theorists and observationalists happy (or at least scratching their heads) for a while yet. Hopefully us gravitational wave types can detect something to help those guys out.