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Originally Posted by Jerry
The thesis you cite, dated 2003, is an exposition on why Allegro failed. If you look at the papers while Allegro was being designed, and even during testing, you read:
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Originally Posted by Mauceli 1995
The current state of gravitational wave experimentation will allow detectors to record any predicted event that occurs within our galaxy and the technology is at hand to allow experimentalists to record events from remote galaxies.
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I would think that an "event" is surely not a continous wave source like an orbiting binary or a single rotating asymmetric neutron star, but is rather a core-collapse supernova. I'm saying that ALLEGRO stood no chance of detecting the likely continuous wave sources, not that ALLEGRO would fail to detect a core-collapse supernova in this galaxy. There has been no supernova in this galaxy or the clouds since 1987, which was well before the detector was built.
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Verry specifically, they expected to be able to see gravity waves from Relativistic binary Pulsar B1913+16 within our own galaxy. It would be interesting to compare Taylor’s initial calculations, predicting Allegro would be sensitive enough to detect galactic events, with Santostasis’s post mortem that explains why we did not, and see how and why parameteric assumptions were tweaked. More, later.
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I cannot find any claims about 1913+16 in the ALLEGRO papers available from LSU. I cannot find any calculations made by Taylor connected with ALLEGRO. Whilst searching for these I did find some
stuff that you might find interesting concerning sources and sensitivity of GW detectors.
None of the Mauceli et al. papers themselves quote any GR calculations (being mainly concerned with characterising the detector rather than quantifying possible sources). They mention that they assume an ellipticity of 10^-5 for possible continuous sources but provide no other details on their calculation. Santostasi assumes the same ellipticity when predicting LIGO-II's required integration time to detect the 1987A remnant (3 years). As Mauceli et al. themselves point out the ALLEGRO detector was built to detect core-collapse events, not radiations from relatively asymmetric neutron stars.
The paper by Zeng et al. on ALLEGRO's prospects when working with other detectors concludes,
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Originally Posted by Zeng et al. 1994
Thus this may be the first year that a third detector makes it technologically possible to unambigiously discover gravitational waves. While such a discovery is unlikely at the current levels of sensitivity, the actual result awaits final analysis.
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But some of this is cheap talk. I might expect that you don't put much trust in the hype for, say, WMAP, so why would you put any more in hype concerning GW detectors, especially when it appears in a conference speech? The fullest numerical analysis of ALLEGRO concerning detectability of continous wave sources that's available on the web would seem to be that of Santostasi.
As I see it, the main points are these:
* At its best, ALLEGRO was comparable to LIGO in sensitivity. LIGO itself is not expected to pick up continuous wave sources until after the upgrade to LIGO-II.
* ALLEGRO is maximally sensitive at two relatively narrow frequency windows that were selected to be valuable in the case of another "nearby" explosion like 1987A but are quite limiting when it comes to rotating neutron stars (and don't help at all for orbiting neutron stars). Interferometers like LIGO are, by comparison, broadband detectors. So ALLEGRO could only pick up GWs from a small number of the total local neutron star population (those that happened to be rotating at the right frequency), and if they were as elliptical as 10^-5 and if the detector was sensitive enough at the "windows".
* ALLEGRO stood a very decent chance of detecting core-collapse supernovae in our galaxy (the "decent chance" is because you need other, comparable detectors operating to claim a convincing detection). There were no such events between 1991-1995, when the detector was operating (we are certainly overdue for one in this galaxy). Although the detector would probably have responded to the burst of GWs produced by SN 1987A, detecting the rotating neutron star left behind after the blast would require implausible integration times as Santostasi demonstrated.
I will definitely worry if:
* LIGO-II fails to detect any continuous sources, mainly relativistic binaries. The detection of individual neutron stars depends on the ellipticity of the source, but the detection of neutron star binaries should not (or not to the same extent).
* The successors to ALLEGRO (and LIGO or LIGO II) fail to detect a core-collapse supernova in our galaxy, if and when one goes off.
Those non-detections would say something interesting. At the moment the harshest tests of GR are coming not from presently insufficiently sensitive gravitational wave experiments but from examination of the recently discovered binary pulsar J0737–3039. But as I said last time, the most revealing and interesting tests of GR are most likely to be in the regime of low accelerations, as with Pioneer and MOND, and at small distances.
If you are looking for sources of worry in GR, dark matter and Pioneer are currently much better bets than gravitational waves. Almost all alternative theories of gravity predict gravitational waves of some form in any case, even if some of them are ruled out by pulsar observations.