March 08, 2016

"Two astronomers have looked at the data and are not convinced an FRB afterglow was actually seen."

Slate: In a paper that is online and will be submitted to The Astrophysical Journal Letters (and not yet peer reviewed), they suggest the astronomers looking for the afterglow were instead fooled by the elliptical galaxy itself. by Phil Plait

'All big galaxies have a supermassive black hole in their cores. If enough material is pouring into that black hole, it can form a disk outside the hole. This disk gets very hot, and glows. Galaxies like this are said to be active galaxies.

'They’re notoriously variable, too, changing in brightness over relatively short periods of time. In the new report, the astronomers argue convincingly that this matches the data better than a fading FRB afterglow. The galaxy does appear to be active and variable, for one thing, which could easily explain the fading source seen. They also show that the way the light dimmed in the galaxy doesn’t match what is known about the way huge explosive events like this fade, again throwing some cold water on the claim.

'If the afterglow was not from the FRB, then the distance was not necessarily accurately determined. The FRB may have been in another galaxy entirely, or even in our own! And the distance was the key ingredient for the next bit of news: Half the “missing mass” of the Universe had been found. Using the way the radio signal from the FRB was shifted in wavelength/frequency, the original astronomers were able to estimate how much matter was between us and the FRB. If the distance isn’t known, then that measurement can’t be made. So until we know for sure where that FRB was in the Universe, we can’t say anything about the amount of material the signal passed through on its way to Earth.'

"Cosmological Origin for FRB 150418? Not So Fast" by P. K. G. Williams and E. Berger here

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