KEP is confused...
24 Sep 2006 21:15:27 UTC
Topic 191870
(moderation:
My fellow crunchers
Can anyone tell me, are we looking for new pulsars or are we checking the position of know pulsars, in our effort to find evidence for gravitational waves? And also, can anyone tell me within what search area we are searching, for instance is the search sensitive enough to tell us every position of new / know pulsars within n light years? I remember to have seen something about the sensitivity being 1500 light years, is this true? And then a final question, are we searching certain frequenzys at certain times within the S5 840 hours sensitivity, or are we searching all 840 hours of data at that certain frequenzy?
Feel free to answer any of the questions that I've asked, that you know the answers to and leave the rest to those who knows the answer to the questions you don't know the answer to...
Regards!
Happy crunching!
KEP is confused...
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Have a look at http://einsteinathome.org/about/index.html.
Maybe that helps to reduce your confusion...
Udo
Udo
RE: My fellow
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There are a number of science aims but primary among them is the search for 'binary inspirals'. This is the searching for the gravitational wave signatures of fairly momentous events out there. Consider two large star remnants, both or either can be a black hole ( BH ) or a neutron star ( NS ) - call them pulsars generically - which are in the end phase of their approach to each other before combining into some common final object.
Visualise this: they approach each other from some large distance and orbit each other, but are radiating away energy in the form of gravitational waves ( ripples in spacetime ), thus losing energy from the system, hence they move closer and closer. They will finally collide and merge. The sequence described has a predicted waveform detectable at a distance ( us ) which it is hoped will be detected by the LIGO's.
The better the suppression of extraneous ( non-astronomical ) noise in the laser resonance cavities ( and other elements ) the 'quieter' the signal from such events that can be 'heard' and thus the greater the distance/volume of space from which an event can be detected. The sensitivity varies according to the conditions ( at the LIGO's ) of the moment.
I like to occasionally browse over the electronic logs for the LIGO's - goto here then select either Hanford or Livingstone logs, select the detector logs option ( use the user name = 'reader' and password = 'readonly' ), and view a "Figure of Merit" - one of which will show 'NS/NS Inspiral Range' in the upper right of a screenshot from their control system monitor. This gives the range in Mpc ( Mega-parsecs ), over the recent time period in question, of expected detections of a 'standard' inspiral waveform. It's generally out at about 14 MPc - which is ( at 1 parsec = 3.26 light years ) about 4.3 Million light years. For comparison the Andromeda Galaxy is at a bit over 2 million light years away ( see here ).
Now because of the changing 'tone' of the inspiral as it develops, then a range of frequencies need to be searched for over the whole of the 'good' data periods to hopefully come up with a detection - to some high level of confidence anyway.
Hence the need for bucket-loads of signal analysis - which is the raison d'etre of E@H!
Cheers, Mike.
( edit ) So it's not really 'new' pulsars ( born in supernovae, etc ) that we are detecting, but a rather final phase of some of them.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
The pulsars we know from
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The pulsars we know from radio astronomy which we expect to emit gravitational waves, too, are (mostly) too far away for the current sensitivity of the detectors, if our ideas and models of gravitational waves and their sources are right. So what we currently do is to "blindly" (i.e. untargeted) search the whole sky for closer, pulsar-like sources of gravitational waves, that may not show up as electromagnetic pulsars.
You can indeed express the sensitivity of the detectors in terms of distance we are able to search. I don't remember the numbers (e.g. distances) from the top of my head, but if you want them, you maybe better asking over in the science board.
And I'm not sure I understand your final question. For what it's worth, we are searching all the data for all (reasonable) frequencies. The main idea for splitting the work into the workunits is the frequency, so a single Task only searches a rather small frequency range in all the data (from one detector).
BM
BM
RE: […] It's generally
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14 Mpc is something like 45 million light-years. Did you divide by 3.26 instead of multiplying, or did you switch the figures?
RE: RE: […] It's
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Oops, my bad ... :-)
Yeah I divided :-(
Cheers, Mike.
( edit ) Cool! As square root of 10 is about 3 and a bit ( 3.16 ) then the error ( divide instead of multiply ) leaves you out by a near factor of ten..... sigh
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Thanks for the informative
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Thanks for the informative and friendly replys, Udo, Mike Hewson and Bernd Machenschalk, it all made it all look more clear to me. I guess now, that I've found a project there ultimately can end up leading to knowledge about the "final" shape of our universe, and some of the shapes of our surrounding universes. I'm glad to see that our science may end up bringing in a lot of findings, or at least some day just 1, which will also be enough to prof the "ripple" theory of Einstein. If I can help make this champ of physics and even greater champ, all the effort of my computer want be in vain.
Happy crunching!
Your Friend!