S3 Analysis Summary Questions, Answers, Comment and Discussion
11 Sep 2005 17:07:07 UTC
Topic 13121
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I have just posted the long-promised first report on the Einstein@Home S3 analysis. Please use this thread for questions, answers, comments and discussion.
Bruce
S3 Analysis Summary Questions, Answers, Comment and Discussion
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5.1 is a flat line, because a detector in space far from our solar system would not be spinning or orbiting the sun and so there would be no frequency modulation due to its motion.
13.3a is not quite flat. Look at the vertical scale, and the zoom below.
13.3a/b is the frequency of a pulsar located directly over the Earth's orbital plane. There is no annual variation of the Earth's distance from this pulsar, so no annual frequency modulation. Just the (smaller) frequency modulation due to the Earth's rotation, shown in 13.3b.
Bruce
RE: Outstanding
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Improvements in sensitivity get harder and harder as you get closer to the design goal. We've made two key upgrades at Hanford this summer, to the 4km instrument, to make it more sensitive and get very near our design goal for our one-year run, starting Nov 5, 05. The first was to swap out a suspended test mass, one of the core optics of the long arm of the machine. This optic was too reflective, scattering some excess light out of the arm and spoiling the heating (thermal lensing property) of the cavity. We installed a better, less reflective optic. This is described (with some nice photos) at: http://www.ligo-wa.caltech.edu/ligo_science/vent_0605.html
Furthermore, we've been boosting the laser power incident on the 4km machine (and the others, as well), in order to reduce the noise at high frequency (so-called shot noise)
RE: Brian Al known pulsars
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While it is true that many of the known pulsars are farther away than we'd like, LIGO and GEO do target them for analysis. This is typically done with different code and search algorithms than Einstein@home, for example http://xxx.lanl.gov/PS_cache/gr-qc/pdf/0410/0410007.pdf (this preprint is a technical paper that was published in Phys Rev Letters).