Monday, August 15, 2005

short and hard - GRB 050813

Here we go again.

Swift detected a short, hard gamma ray burst over the weekend.

GRB 050813

A 32 msec primary burst with an extended weak flux of ~ 0.6 secs. and possibly a second weak peak at 1.3 secs.

Very weak, very tentative x-ray counterpart also detected by Swift.

The optical followups were initially mystifying, until the Magellan group identified a medium redshift cluster at the location.
Redshift of z=0.722.

The tentative x-ray counterpart is at the center of the cluster, consistent with being in or at the outskirts of the cD galaxy anchoring the cluster. Quite reminiscent of GRB 050509B

If all this is confirmed (a radio counterpart would be useful...), then I think we have a definite case for short-hard GRBs being associated with low/medium redshift galaxies, and some (the xray bright ones, tentatively) being associated with old stellar populations.

That is very, very suggestive of the neutron star merger scenario for these bursters. Main issue now, I think, is whether some are neutron star-black hole mergers, possibly as a distinguishable sub-class.

The other interesting thing is that I now think we know what the next GRB mission should look like; a Swift architecture for rapid response; a larger more sensitive x-ray telescope, and a near-IR meter class telescope for the optical followups.

Should be doable as an explorer class mission.


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