FRB & Gravitational Wave Link: Scientists Baffled

[jedishrfu]

TL;DR Summary

Scientists notice a FRB occurred shortly after a Gravitational Wave event

https://www.sciencealert.com/uncann...burst-detected-after-gravitational-wave-event

Every so often, a strange signal from outer space hits our detectors here on Earth.

Known as fast radio bursts (FRBs_, these signals are extremely short, just milliseconds in duration, and are detected only in radio wavelengths.Yet in those milliseconds, and in those wavelengths, they can discharge as much energy as 500 million Suns – and most of them have never been detected again.

What they are, and how they are generated, is something of a baffling mystery. But a new discovery could point to a previously unknown mechanism producing these powerful bursts of radiation.

On the 25th of April in 2019, the Canadian Hydrogen Intensity Mapping Experiment (CHIME) recorded a bright, non-repeating fast radio burst ( FRB).

Just 2.5 hours earlier, the Laser Interferometer Gravitational-Wave Observatory (LIGO) recorded a gravitational wave event, the collision as a binary neutron star reached the inevitable conclusion of its decaying orbit.

The FRB's location in the sky fell within the credible region of the gravitational wave event, and from a similar distance. The chance that the two events were unrelated, a team of astronomers led by Alexandra Moroianu of the University of Western Australia has determined, is extremely small.

 

[Vanadium 50]

I'm not impressed.

LIGO localizes well in time, but poorly in space.

CHIME alone sees hundreds of FRBs per year. World-wide, perhaps one every 12 hours. LIGO sees maybe 5 events/year, so we expect one or so to be within 2.4 hours. We see one within 2.5 hours.

This is just a ballpark estimate, but it shows that we need a more detailed analysis than "Golly, look at that." And that ignores the problems with a posteriori probabilities.

 

[jedishrfu]

I can't comment on that although they claimed to have somewhat localized the signal to the same area in space. So perhaps after several more sightings, they will have a better grasp on whether its true or not. Perhaps right now they'd like it to be true.

For the theorists, it gives them something to add to their models to explain how a gravitational event can also spit out an FRB event.

 

[Vanadium 50]

LIGO's localization is quite poor, especially LIGO alone (i.e. w/o VIRGO). It can be a good chunk of the sky.

But my concerm is more general - if you look for correlations among N variables, the odds of finding one that is significant go way up. This is true even if the "you" consists of different teams.

 

[ohwilleke]

I'm not impressed.

LIGO localizes well in time, but poorly in space.

CHIME alone sees hundreds of FRBs per year. World-wide, perhaps one every 12 hours. LIGO sees maybe 5 events/year, so we expect one or so to be within 2.4 hours. We see one within 2.5 hours.

This is just a ballpark estimate, but it shows that we need a more detailed analysis than "Golly, look at that." And that ignores the problems with a posteriori probabilities.

I agree.

The well confirmed dual signal example we have involved an electromagnetic signal and a gravitational wave signal separated by just two seconds, establishing that gravitational waves travel at a speed imperceptibly different from the speed of light as predicted by GR. It is entirely possible (and indeed, it is very likely) that the process that generated the gravitational wave and the one that generated the electromagnetic signal actually happened two seconds apart, with both signals traveling at the speed of light.

There is no credible event type proposed to produce an FRB that would be separated from a gravitational wave event by 2.5 hours or so. If the events were three order of magnitude (0.0025 hours = 9 seconds or less) closer in time it would start to seem credible. If it were four orders of magnitude closer in time (0.9 seconds), it would be very powerful evidence indeed.

But both the electromagnetic signal and the gravitational wave signal are very precise time indicators, and an FRB and a gravitational wave event within 2.5 hours of each other in the same very general part of the sky (particularly given that the density of stars/black holes that could generate FRBs or gravitational wave events is not equal in all directions of the celestial sphere because we are in a disk-like galaxy, see, e.g., here) is actually not an unlikely coincidence (if the likelihood is evaluated properly), and the directional precision of gravitational wave events is indeed not very great.