GW Detection Confirmation: Time, Rate, & GRB?

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Discussion Overview

The discussion revolves around the detection of gravitational waves (GW) by the LIGO experiment, specifically focusing on the confirmation of a binary black hole merger event and the implications of its detection rate. Participants explore the time required to validate the initial findings and the potential for independent confirmation through coincident gamma-ray bursts (GRBs).

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants express concern about the possibility of the detected signal being spurious, questioning how much time should pass before confirming the result with a second event.
  • There is acknowledgment that the rate of expected discoveries similar to the December 11 event is currently unknown, with weak bounds provided by the LIGO event itself.
  • One participant reflects on the excitement surrounding the initial announcement, later expressing skepticism after reviewing the associated paper, likening it to a "WOW! signal."
  • Another participant raises a question about how the bounds on the detection rate were estimated from a single event, indicating this was a topic of discussion in their institute.
  • A proposed method for estimating the bounds includes considering the signal plus background rate, suggesting that a low rate would imply a lower bound on the signal rate, while a high rate would imply an upper bound due to the lack of additional observed events.
  • One participant notes the large range of allowed rates (2-400 Gpc^-3 yr^-1) as quoted in the LIGO paper, emphasizing the statistical limitations of having only one event.

Areas of Agreement / Disagreement

Participants generally agree that the rate of events is unknown and that the bounds are weak. However, there is no consensus on the implications of the single event or the methods used to estimate the detection rate.

Contextual Notes

The discussion highlights limitations in statistical inference from a single event and the dependence on definitions of signal and background rates, which remain unresolved.

Gravitoastronomy
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I understand that the LIGO experiment was very lucky to find a very strong signal of a very energetic event (binary black hole merger). Having into account the non-negligible possibility that the signal may be spurious or some problem in the data adquisition, how much time must pass before we can confirm (with a second event) that the result was likely genuine, or that could be spurious (for example, if months pass without other detection). In other words, what is the average rate of expected discoveries similar to the event on 11th December?

I have also heard that there has been independent confirmation of Gamma-ray burst coincident in time with the event (0.4 seconds shift). How trusty are those news?
 
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The rate is unknown. The best bounds on the rate (which are rather weak) comes from the LIGO event.
 
Orodruin said:
The rate is unknown. The best bounds on the rate (which are rather weak) comes from the LIGO event.
So we must wait. After the first announcement and all the excitement, I read the paper and I changed mood, it was too good to be true, like a kind of WOW! signal. I hope that new events will confirm the data, they had detected a few candidates but with much lower sigma.
 
Orodruin said:
The rate is unknown. The best bounds on the rate (which are rather weak) comes from the LIGO event.
That was one of my questions, left open in a discussion in our institute. How were the bounds on the rate estimated from just a single event?
 
vanhees71 said:
That was one of my questions, left open in a discussion in our institute. How were the bounds on the rate estimated from just a single event?

I would assume that this was inferred in the standard way. If the signal+background rate was too low, it would be very unlikely to already have an event, which would put a lower bound on signal+background rate (translating to a lower bound on the signal rate given that the background rate is minuscule). If the signal+background rate was too high, it would be very unlikely to not have observed more events, which would put an upper bound on the rate.

Of course, one event is not much statistics and therefore the resulting allowed range is going to be large (2-400 Gpc^-3 yr^-1 as quoted in the LIGO paper).
 
I see, thanks for the quick response!
 

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