Archive for GW150914

The Great Gravitational Wave Source Follow-Up

Posted in The Universe and Stuff with tags , , , on March 1, 2016 by telescoper

I recently noticed on the arXiv  an interesting paper with 1562 authors!

Here is the abstract:

A gravitational-wave transient was identified in data recorded by the Advanced LIGO detectors on 2015 September 14. The event candidate, initially designated G184098 and later given the name GW150914, is described in detail elsewhere. By prior arrangement, preliminary estimates of the time, significance, and sky location of the event were shared with 63 teams of observers covering radio, optical, near-infrared, X-ray, and gamma-ray wavelengths with ground- and space-based facilities. In this Letter we describe the low-latency analysis of the gravitational wave data and present the sky localization of the first observed compact binary merger. We summarize the follow-up observations reported by 25 teams via private Gamma-ray Coordinates Network Circulars, giving an overview of the participating facilities, the gravitational wave sky localization coverage, the timeline and depth of the observations. As this event turned out to be a binary black hole merger, there is little expectation of a detectable electromagnetic signature. Nevertheless, this first broadband campaign to search for a counterpart of an Advanced LIGO source represents a milestone and highlights the broad capabilities of the transient astronomy community and the observing strategies that have been developed to pursue neutron star binary merger events. Detailed investigations of the electromagnetic data and results of the electromagnetic follow-up campaign will be disseminated in the papers of the individual teams.

This is interesting not so much for the result – there wasn’t really any expectation of finding an electromagnetic counterpart of a binary black-hole merger – but that it’s the first example of the kind of mass mobilisation of astronomers that will be needed when gravitational-wave astronomy gets going in earnest. Astronomers working on transient sources such as gamma-ray bursts are already used to this kind of operation, but there’s going to be a lot more of it in the future!



LIGO: Live Reaction Blog

Posted in The Universe and Stuff with tags , , , , on February 11, 2016 by telescoper

So the eagerly awaited press conference happened this afternoon. It started in unequivocal fashion.

“We detected gravitational gravitational waves. We did it!”

As rumoured, the signal corresponds to the coalescence of two black holes, of masses 29 and 36 times the mass of the Sun.

The signal arrived in September 2015, very shortly after Advanced LIGO was switched on. There’s synchronicity for you! The LIGO collaboration have done wondrous things getting their sensitivity down to such a level that they can measure such a tiny effect, but there still has to be an event producing a signal to measure. Collisions of two such massive black holes are probably extremely rare so it’s a bit of good fortune that one happened just at the right time. Actually it was during an engineering test!

Here are the key results:




Excellent signal to noise! I’m convinced! Many congratulations to everyone involved in LIGO! This has been a heroic effort that has taken many years of hard slog. They deserve the highest praise, as do the funding agencies who have been prepared to cover the costs of this experiment over such a long time. Physics of this kind is a slow burner, but it delivers spectacularly in the end!

You can find the paper here, although the server seems to be struggling to cope! One part of the rumour was wrong, however, the result is not in Nature, but in Physical Review Letters. There will no doubt be many more!

And right on cue here is the first batch of science papers!

No prizes for guessing where the 2016 Nobel Prize for Physics is heading, but in a collaboration of over 1000 people across the world which few will receive the award?

So, as usual, I had a day filled with lectures, workshops and other meetings so I was thinking I would miss the press conference entirely, but in the end I couldn’t resist interrupting a meeting with the Head of the Department of Mathematics to watch the live stream…

P.S. A quick shout out the UK teams involved in this work, including many old friends in the Gravitational Physics Group at Cardiff University (see BBC News item here) and Jim Hough and Sheila Rowan from Glasgow. If any of them are reading this, enjoy your trip to Stockholm!