Astronomers pinpoint radio flashes originating long-long ago in a galaxy far-far away
Columbia, Maryland, January 4, 2017 - Astronomers have for the first time pinpointed the location of a so-called "fast radio burst" (FRB) -- a type of short-duration radio flash of enigmatic origin -- and have used this to identify its home galaxy. Prior to this discovery, astronomers have lacked the definitive proof that FRBs come from far outside our Milky Way galaxy. This is because poor localization has prevented unique identification of their galaxies of origin. The new finding is critical because it has allowed astronomers to precisely measure the distance to the source, and hence to determine how much energy it is producing.FRBs are visible for only a fraction of a second and have puzzled astronomers for over a decade since they were first discovered. Precise localization of an FRB requires the use of radio telescopes separated by large distances, which allows high-resolution images to be made when the data from these telescopes are combined with each other. The FRB 121102 was originally detected at the Arecibo Observatory in Puerto Rico in November 2012. In 2014, Arecibo recorded another burst from FRB 121102, making it the only known repeating FRB. On Aug 23, 2016, the Karl G. Jansky Very Large Array (VLA) in New Mexico was used to detect yet another burst from Arecibo's FRB and use it to determine the sky position to a fraction of an arcsecond. "This is an angle similar to that subtended by a human hair held at a distance of 200 meters," said Shami Chatterjee of Cornell University. At the same celestial position, astronomers found both steady radio and optical sources, which pointed the way to the galaxy hosting the FRB. To zoom in even further, scientists used the European VLBI Network (EVN), which links telescopes spread across the world, to obtain a position ten times more precise than that of the VLA alone. Arecibo was a vital partner in this campaign. "With this level of precision, we could determine that the origin of the bursts lies right on top of the steady radio source seen by the VLA," noted Benito Marcote from the Joint Institute for VLBI in Europe (JIVE)."It is the combined sensitivity of the telescopes, their large separations, and the unique capabilities of the JIVE central data processor that allow the pinpointing of events that are as short as a thousandth of a second," added Zsolt Paragi of JIVE. "That gives a positional accuracy on the sky of about 10 milliarcseconds.""Arecibo's participation with the EVN supplies the longest baselines and the highest possible angular resolution," noted Universities Space Research Association's (USRA) Dr. Tapasi Ghosh, a VLBI astronomer at Arecibo Observatory. "We also provide unparalleled sensitivity for imaging the faint bursts."Dr. Andrew Seymour, a USRA postdoctoral scientist at Arecibo, worked with Ghosh to set up parallel observing modes, whereby Arecibo not only acquired VLBI data, but also recorded wideband, high-time-resolution, single-dish data. "These data were used to find the exact times of the bursts," Seymour explained. "Then the VLBI imaging process could zero in on those specific times and make images of the bursts themselves."