“That’s the next step: to simultaneously see [gravitational waves] with three, four or five interferometers, localize it quickly, within minutes, and have other observatories catch it instantly, and catch it in the optical or the X-ray bands. That’s going to provide a whole new understanding in these cataclysmic events.” -Dave Reitze, executive director of LIGO
On September 14th, 2015, both LIGO detectors in Hanover, WA and Livingston, LA, detected an unambiguous gravitational wave signal from two merging black holes some 1.3 billion light years distant. About 0.4 seconds later, NASA’s Fermi satellite saw a weak, transient event in the gamma ray portion of the electromagnetic spectrum.
Could this have been a surprising accompaniment to the black hole-black hole merger? It’s possible, but there are three strikes against it: the data has less than 3σ statistical significance; the orientation of the signal to the satellite was out of the optimal range for detection; and the ESA’s Integral satellite saw null results looking for the same effect. In other words, not only is the jury still out on whether these gravitational wave events have electromagnetic counterparts, but you should be very skeptical about Fermi’s reported results!