LIGO Does It Again: A Second Robust Binary Black Hole Coalescence Observed

The two LIGO gravitational wave detectors in Hanford Washington and Livingston Louisiana have caught a second robust signal from two black holes in their final orbits and then their coalescence into a single black hole. This event, dubbed GW151226, was seen on December 26th at 03:38:53 (in Universal Coordinated Time, also known as Greenwich Mean Time), near the end of LIGO's first observing period ("O1"), and was immediately nicknamed "the Boxing Day event".

In GW151226, the two black holes weighed in at 14 and 8 solar masses and merged at a distance of some 1.4 billion light years from Earth. Get all the info from the LIGO science summary.

Thanks for your continuous support in these exciting times!

Oliver, for the whole Einstein@Home team

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HS
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LIGO Does It Again: A Second Robust Binary Black Hole Coalescenc

CongratulationĂ¯Â¼

DanNeely
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The paper itself is available

The paper itself is available too for anyone who wants more details:

http://arxiv.org/abs/1606.04855

Rabinovitch
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Were our computations useful

Were our computations useful for this detection?

tullio
tullio
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The September event was

The September event was followed after 0.4 s by a gamma ray burst coming from the same region of space. I haven't read anything similar for the December event.
Tullio

Rapture
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I did not expect LIGO to find

I did not expect LIGO to find another one soon. That is an amazing achievement. Expecting many more to be discovered.

Christine Olson
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Was this from Einstein@Home?

Was this from Einstein@Home? From reading the official report, I do not think so, but it would be awesome if that were true. Thanks!

Bikeman (Heinz-Bernd Eggenstein)
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RE: Was this from

Quote:
Was this from Einstein@Home? From reading the official report, I do not think so, but it would be awesome if that were true. Thanks!

No, the Gravitational Wave search on Einstein@Home is at the moment looking for a different type of GW. The two GWs that were found so far are from the merger of compact objects (binary black holes in these two cases) and the detectable signals from this kind of event last only a short time, while the waves that E@H is currently hunting for are "continuous": always on, so to speak.

If possible, you want to detect the more short-lived signals with a very low latency (shorter than the typical task deadlines in a BOINC project), so that if you think you found something, you can alert other astronomers who will then point their telescopes at the identified sky-region to look for counterparts in other forms of radiation. There is no such concern for the sources of GW that E@H is currently looking for, because they are not expected to change their emission over short time scales.

That doesn't mean that searches on Einstein@Home for short-lived signals will never happen, but currently we are not doing that.

HB

AgentB
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RE: No, the Gravitational

Quote:
No, the Gravitational Wave search on Einstein@Home is at the moment looking for a different type of GW. The two GWs that were found so far are from the merger of compact objects (binary black holes in these two cases) and the detectable signals from this kind of event last only a short time, while the waves that E@H is currently hunting for are "continuous": always on, so to speak.

Thanks HB, are we searching for a continuous signals from each of the two LIGO detectors (independent of the other)?

I guess the frequency once found, will be very accurate, but will we be able to identify a location more accurately than the two events so far?

Betreger
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RE: I guess the frequency

Quote:

I guess the frequency once found, will be very accurate, but will we be able to identify a location more accurately than the two events so far?


As understand it a third LIGO such as the proposed one in India is needed to better triangulate the source. Anyone please correct if they know better.

tullio
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VIRGO should start in fall

VIRGO should start in fall after upgrading similar to Advanced LIGO.
Tullio

Stefan
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RE: I did not expect LIGO

Quote:
I did not expect LIGO to find another one soon. That is an amazing achievement. Expecting many more to be discovered.


If you have a 1 billion LY sphere to observe i guess black hole collisions happen quite often.

AgentB
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RE: RE: I guess the

Quote:
Quote:

I guess the frequency once found, will be very accurate, but will we be able to identify a location more accurately than the two events so far?

As understand it a third LIGO such as the proposed one in India is needed to better triangulate the source. Anyone please correct if they know better.

I don't know better, but my hopeful thinking (blinded by science?) is, because the source is fixed, and continuous, and the two detectors are spinning around on the good Earth, we'll get a direction.

Mike Hewson
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You'll notice that the sky

You'll notice that the sky areas are in arc segments for each given source when using two interferometers :

where another interferometer will allow ambiguities to be resolved ( with good signal, favourable geometry etc ) and effectively an intersection of several arcs constructed ( per detection ). Basically with more detectors available the more parameters for a given source may be nailed down.

NB With continuous ongoing signals the platform for detection ( Earth ) is moving all the while and it becomes rather more like the triangulation that one would do visually to gauge a visible source. On the face of it one might think that a moving platform is detrimental. However since we know the character in detail of that movement then it becomes a modulation upon a true sky signal not found in other possibilities. Earth's motions are like bobbing and weaving one's head to pick out some visual target against a background ( tiny parallax changes ). The key advantage with having more than one detector available is permitting us to believe there is a detection at all ! :-)

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal