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This signal was reported on months ago. Can anyone explain what they did to move the GW151226 signal from 2-sigma to >5-sigma?

"The data is in fact completely open and you could analyse it yourself! In addition to the GW150914 event there are also two others that rise somewhat above the background ("GW151012" and "GW151226"). You can see them by eye in the above plot. They are clearly not statistically significant enough to announce a discovery alone, but still they are tantalising... with room for improvement to design sensitivity (by a factor of ~2 which increases the spatial reach by 2^3) and the construction of a third detector in India to triangulate the signal, the future of gravitational wave astronomy is exciting." http://syymmetries.blogspot.com/2016_03_01_archive.html




Their background analysis is data-driven; the more data they take the better they know their background noise. They are now at the point where they can definitely say that what looked like an unusual fluctuation above the background noise months ago was in fact very unusual. Enough for discovery significance.


Citation, as it says in the article:

"Two matched-filter searches used coincident observations between the two LIGO detectors from September 12, 2015 to January 19, 2016 to estimate the significance of GW151226. One of these searches was the off-line version of the online search discussed previously. The off-line searches benefit from improved calibration and refined data quality information not available to online searches."

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116...


The use of p-values with a research design like you are describing worries me:

'The garden of forking paths: Why multiple comparisons can be a problem, even when there is no \ shing expedition" or "p-hacking" and the research hypothesis was posited ahead of time' http://www.stat.columbia.edu/~gelman/research/unpublished/p_...


I think you might be confusing LVT151012 which was including in the announcement back in February and all the subsequent papers. That is a low significance trigger that may be another binary black hole merger. GW151226 is only being reported on now as it was still in the vetting process back in February.


Gosh, wake me up in 50 years, I can't wait to learn what is the nature of dark energy and what lays beyond standard model.


Wow 50 years, by then it might be that we find we were asking the wrong questions at this point. And even with the right questions, the answers were... unexpected.




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