Mysterious Gamma-Ray Burst May Be Linked To Gravitational Wave Find (latimes.com)

mdsolar quotes a report from Los Angeles Times: After a decades-long search, scientists announced early this year that they had detected gravitational waves probably coming from the merger of two black holes back in September. Now, a team of scientists using NASA's Fermi Gamma-ray Space Telescope say they spotted a brief flash of gamma rays that occurred less than half a second after that long-sought gravitational wave signal. The gamma-ray outburst, described at the American Physical Society's April meeting in Salt Lake City, has not been definitively linked to that first gravitational wave signal, and scientists weren't able to pinpoint its exact origin -- just that they came from the same general area. But if other astronomers begin to find a similar pattern, the results do raise the intriguing possibility that such high-energy events might not be quite as 'invisible' as we thought. The first gravitational wave signal rolled through the Laser Interferometer Gravitational-wave Observatory on Sept. 14, hitting the Louisiana detector first and then the one in Washington state seven milliseconds later, telling researchers that the signal must have come from the southern hemisphere.

Comments

Re:"Half a second" is a lifetime...

[MichaelSmith]

Yeah but photons are delayed when propagating through gas or plasma because they get absorbed and re-emitted. Photons from SN1987A arrived (IIRC) 14 seconds after the associated neutrinos.

Most Likely Explanation

[Tenebrousedge]

The most likely explanation was that it was just a spurious signal (as your source notes). Quoting Wikipedia:

However, observations using the INTEGRAL telescope, through the all-sky SPI-ACS instrument, indicate that the amount of energy in gamma-ray and hard X-ray emission from the event was less than one part in a million of the energy emitted in the form of gravitational waves, concluding that "this limit excludes the possibility that the event is associated with substantial gamma-ray radiation, directed towards the observer." If the signal observed by the Fermi GBM was genuinely astrophysical, SPI-ACS would have detected it with a significance of 15 sigma above the background.[50] The AGILE space telescope also did not detect a gamma-ray counterpart of the event.[51]

It's also worth noting that while Fermi can tell the origin of a signal to some degree, it's not what you would call pinpoint accurate. "The region not occulted by the Earth contains 75% of the probability of the localization map," which means that the other 25% was pointing towards a terrestrial gamma ray burst but that's not what we're here to science, darn it! Later they say, "The best-fit location is towards the Earth but the large uncertainty on the location allows an arrival direction from the sky."

This event has consumed ink wildly out of proportion to its merit.