New Fast-Radio-Burst Phenomenon Baffles Astronomers –“Reveals a Previously Unknown Hole in the Milky Galaxy”




Scientists detected the newest Fast radio burst, 5-millisecond intergalactic blips of radio waves, FRB 150215, on February 15, 2015 with the Parkes Telescope in Australia, but still don’t know the cause of it, or the 22 similar FRBs spotted on different occasions since 2007 that leave no trace, be they x-rays or visible light, or neutrinos. It's predicted that around 2,000 of these mysterious phenomena are lighting up the Universe every single day.

“We spent a lot of time with a lot of telescopes to find anything associated with it,” the study’s first author, Emily Petroff from the Netherlands Institute for Radio Astronomy, told tech news site, Gizmodo. “We got new wavelength windows we’ve never gotten before. We looked for high-energy gamma rays and neutrinos…we ruled out some source classes but no detection is a little unhelpful. We’re still trying to figure out where this one came from.”

Even more intriguing and baffling, after analyzing data from the follow-up telescopes, Petroff's team found that the FRB had taken an interesting path through the Milky Way to make its way to us—a hole of sorts that, prior to the detection of the FRB, was unknown. Thus, despite learning nothing new about the source of FRBs in general, the team has learned something new about our galaxy.

The scientists had to peer through the Milky Way to spot 150215, and the galaxy’s magnetic field should have altered the way the radio burst’s light traveled—but it didn’t. “It probably traveled through some kind of hole in the Milky Way that makes it easy to find compared to normal searches in the galaxy,” said Petroff. In other words, this probably says more about the Milky Way than about FRB 150215.

“I have to say this is a fantastic paper but it is a bummer of a paper,” Shami Chatterjee, senior research associate at the Cornell Center for Astrophysics and Planetary Science told Gizmodo. “They threw every resource that we have at this FRB. They followed up with TNT, ANTARES, The Australian Telescope, Swift, Chandra, Magellan, the Dark Energy Camera, GMRT, Lovell, the VLA, and they see nothing. It is incredibly important in the sense that even with relatively prompt follow-up there isn’t an afterglow or counterpart that is obvious.” These FRBs leave no trace, be they x-rays or visible light, neutrinos or anything else.

“It’s not very often in science that you get to work on something that’s so brand new and so unknown that you get to answer the fundamental questions.”

Petroff and her team posted their observation below on the arXiv preprint server yesterday:

We report on the discovery of a new fast radio burst, FRB 150215, with the Parkes radio telescope on 2015 February 15. The burst was detected in real time with a dispersion measure (DM) of 1105.6±0.8 pc cm^{-3}, a pulse duration of 2.8^{+1.2}_{-0.5} ms, and a measured peak flux density assuming the burst was at beam center of 0.7^{+0.2}_{-0.1} Jy.

The FRB originated at a Galactic longitude and latitude of 24.66^{\circ}, 5.28^{\circ}, 25 degrees away from the Galactic Center. The burst was found to be 43±5% linearly polarized with a rotation measure (RM) in the range -9 < RM < 12 rad m^{-2} (95% confidence level), consistent with zero. The burst was followed-up with 11 telescopes to search for radio, optical, X-ray, gamma-ray and neutrino emission.

Neither transient nor variable emission was found to be associated with the burst and no repeat pulses have been observed in 17.25 hours of observing. The sightline to the burst is close to the Galactic plane and the observed physical properties of FRB 150215 demonstrate the existence of sight lines of anomalously low RM for a given electron column density.

The Galactic RM foreground may approach a null value due to magnetic field reversals along the line of sight, a decreased total electron column density from the Milky Way, or some combination of these effects. A lower Galactic DM contribution might explain why this burst was detectable whereas previous searches at low latitude have had lower detection rates than those out of the plane.

The FRB shown at top of the page was detected from very-long-baseline radio interferometric observations using the European VLBI Network and the 305-m Arecibo telescope.

The Daily Galaxy via arXiv and Gizmodo


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