Blue Collar Scientist

The LIGO team recently reported that LIGO, the Laser Interferometer Gravitational-Wave Observatory, has failed to detect gravitational waves from a gamma ray burst. Gamma-ray bursts are the most luminous phenomenon in the universe since the big bang. The favored hypothesis for the cause of most GRBs is the collapse and merger of two compact, massive objects; but there are many other possible explanations.

On February 1, 2007, the Konus-Wind, Integral, Messenger, and Swift satellites, each carrying gamma ray burst detection instruments, reported a short-duration burst in the direction of one of M31’s spiral arms. The high energy and brief duration of the burst suggested that the GRB was caused by a merger of neutron stars or black holes, and the direction suggested it had occurred in a nearby galaxy. If these hypotheses were true, the event should have led to gravitational waves that LIGO should have easily detected.

But LIGO, the Laser Interferometer Gravitational-Wave Observatory, failed to detect gravitational waves at the time of this event. This means that either:

1. the burst actually occurred in a distant galaxy in the same direction as M31;
2. the burst did occur in M31 but was not the result of a compact massive object merger.

Some scientists seem to favor the second explanation. Neil Gehrels, the lead scientist of the SWIFT mission, says “We are still baffled by short GRBs. The LIGO observation gives a tantalizing hint that some short GRBs are caused by soft gamma repeaters. It is an important step forward.”

Some reports seem to suggest that LIGO’s result means that short-duration, high-energy GRBs are never caused by massive compact object mergers. That’s overstating the significance of these results. This represents an important incremental step forward, but it will take many such observations before it becomes clear whether any hypotheses have to be abandoned or upgraded.

Still, this is the first science from a brand new frontier - gravitational waves. We can expect in the coming years that this new discipline will have a big impact on the science of GRBs.

This entry was posted on Thursday, January 24th, 2008 at 3:37 am and is filed under astronomy, press release translation. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.