S5 Qpipeline High-Frequency Review Telecon 24th of July 2008 11:00 Eastern
Agenda and minutes of the S5 Qpipeline High-Frequency Review Telecon for Thursday the 24th of July at 11:00 Eastern time.
Agenda and Contact Info
- update on astro waveforms
- Table of review items
InterCall telecon service: USA (toll-free): 1-866-616-1738 UK (toll-free): 0800 073 8914 Italy (toll-free): 800-906-494 Germany (toll-free): 0800-1014-907 participant code: 251 288 9495#
Minutes by Jonah July 24, 2008 Michele walks us through his matlab script for processing astrophysical waveforms. http://emvogil-3.mit.edu/%7Ezanolin/high_freq_search/astro_wf_treatment.m Issues include: Converting sampling rate Working out right amplitude scale Conversion specifications are comments at top of this m file Waveforms have "inspiral phase" and "burst" phase NS has some angular velocity - when it collapses, a different radius leads to a different angular velocity - this is the "burst". This part of the signal should be isolated, since that is what our search is sensitive to. script: * loads the data * resamples the data from 203 kHz to 16kHz * apply a low-pass filter with a 6000 Hz cut-off The 6000 Hz filter is used to keep energy in the search space The second and third blocks are to study features of the filter - phase shift, numerical errors, etc. They show consistent results. * Remove the mean value of the waveform to get rid of step function at ends * Apply hanning window, which gives minimal distortion of injection spectrum Siong: Why window now? Doesn't the pipeline window the signal at some point? Michele: If waveform does not go smoothly to zero, then there is non-physiscal high frequency content at ends Siong: So, the Hanning window is just to remove this discontinuity Michele: Yes. Jonah: Maybe we should see the waveforms before and after processing side-by-side Michele: Sure, we can do this. * Apply zero-padding to be immune to edge effects of filter Block at "Plot the hrss at 10 K-parsec" * "norm" function computes hrss of waveform * "nor_phy" is the physical hrss at 10 kpc * "nor" is the hrss that went into mdc The code then zero pads the waveform to match the mdc length standard * Finally, the vector is written to a file Code includes a check to make sure the hrss is not adjusted by the application of the hanning window Early mistake was made by directly computing hrss of waveforms without applying windowing and then to use THAT hrss to make conversions. This was a problem because hrss we are sensitive to is part of burst that is high frequency. Jonah: Where is the low-freq. content that you are getting rid of? Michele: We are only looking at a piece of the waveform in the TIME domain - the "burst" piece. Our hanning window is centered around this burst piece. Michele: It would be good for you guys to run this script, and plot results block by block Siong: What is the mass of the proenitor? Where is the cut? Michele: It is a cut in the time domain. There is wobbling in the progenitor, and then it collapses. Siong: I think it is worth knowing what the nature of the initial wiggles is. Michele: The initial conditions are described in the paper. The masses are 1.8 solar masses. They have a model that is, by itself, dynamically unstable. Siong: Are the wiggles you throw away physically motivated? Michele: What I throw out are 6 or 7 periodic cycles. I suspect that is what they call "close to stationary solution". In the paper, I did not find the timescale for this. Siong: If what we are getting rid of is not physical, I think we don't need more discussion. If it IS physically motivated, it is not clear to me that we should just chop it away because it is not in our band. Michele: I will ask them this question. What they pass to me is a few milliseconds. If they tell me the pre-cursor can be in place for a few seconds, what should we do? Ask them to re-run the numerical simulation? Siong: At 10 kpc, the inspiral part could be detected. If there is a big sigal in our band, we want to know about it. Michele: Ok, I'll ask it. Siong: I think it is worth getting your hands on the earlier part of the waveform. Michele: I need to go at this time 11:55 am Michele leaves Brennan: The hyper-massive neutron star wave forms have some issues. Siong: So, these get made into MDC frames Brennan: Yes, we've done that. Brennan: Let's look at my page: http://emvogil-3.mit.edu/~bhughey/high_freq_search/astro/astro.html Brennan walks us through this page. Preliminary results show D1 and D4 waveforms with 50% detection around 100 kpc Siong: It would be great to see some text in the paper about these results. Siong: Let's look at the table of review items. http://www.lsc-group.phys.uwm.edu/bursts/review/projects/s5-qpipe-highf/summaryTable.html Siong: I think these are the items that should be there. Perhaps we should add issues related to using corr power in high freq to this list. Please have a look at the table, and let me know if there is anything missing.