Sunday, June 01, 2008

Budgetary constraints

Way back at the end of 2006 I wrote about a project I'd been working on about searching for gravitational waves from the Crab pulsar (see that post here for more links and details) and how that work had lead to an exciting new result i.e. that we beat pre-existing limits on the amount of energy that could be released via gravitational radiation from the Crab pulsar as it's rotation slows down. Since then we've added more to the search and firmed up the result and I (and others) have presented it at several meetings (e.g. at the AAS) , but we now finally have the paper submitted to the pre-print arXiv (you won't be able to see it until Sunday evening unless you have the secret password.) In my previous post I wasn't able to say what the result was (we'd embargoed the exact numbers until our collaborations internal review process was finished), but now I can reveal them. The main result is that we can say that less than 4% of the energy available from the slowing down of the Crab pulsar is radiated away via gravitational waves. This is a result that it's not currently possible to get via methods other than direct gravitational wave observations, because electromagnetic observations and models of the Crab pulsar and it's surrounding nebula (which is powered by the pulsar's slow-down) are full of too many uncertainties and assumptions that they can't give a good constraint on the energy budget i.e. you can't accurately add up all the possible mechanisms which could contribute to the Crab pulsar slowing down. There should be a press release about this on Monday, so keep your eyes peeled.

[Update: The University of Glasgow's press release can be found here.]

[More updates: The paper has been accepted for publication in The Astrophysical Journal Letters, which is pretty prestigious :)]


  1. I might be being a bit slow here but you haven't actually detected anything? Just that your upper limits tell you that at most 4% of the energy is going into gravy waves, otherwise you would have seen them?

    Is this another one of those papers where the author list is longer than the paper?

  2. Yep, you're right this isn't a detection. It's just an upper limit that's been cast in a way to try and make it astrophysically relevant and interesting. The author list and affiliations only take up about one and a half of the five and a bit pages on the paper, so it's not too bad ;)