Since their discovery in 2007, no one had ever managed to observe one “live,” that is, at the moment it manifests. This is because the so-called Fast Radio Bursts (FRBs) are extremely brief—their duration is just a few milliseconds—and they can appear without any warning practically anywhere in the sky.
However, an international team of astronomers, including Andrea Possenti, director of the INAF-Osservatorio Astronomico di Cagliari, observed one of these radio bursts as it arrived on Earth, omega replica watches capturing it with the 64-meter diameter Parkes radio telescope in Australia, part of the Commonwealth Scientific and Industrial Research Organization (CSIRO).
“These events were usually discovered weeks or months after their appearance. We are the first to have observed one in real-time,” says Emily Petroff, the lead author of the article describing the discovery published in the Monthly Notices of the Royal Astronomical Society. Emily Petroff is a PhD student at CSIRO and Swinburne University of Technology in Melbourne, Australia, and a member of the ARC Centre for All-sky Astrophysics (CAASTRO).
Thanks to this observation, just a few seconds after the event, which occurred on May 14, 2014, and thus named FRB140514, the team immediately activated a series of observations with other instruments—from radio waves to X-rays—aimed as quickly as possible at the region of the sky where the radio burst occurred. Twelve telescopes, in Australia, California, the Canary Islands, Germany, Hawaii, and in space, all united to try to investigate the origin of these enigmatic and unpredictable signals. However, the analysis of the collected data did not reveal any counterpart in the visible light band nor in the near-infrared, near-ultraviolet, and X-rays.
“The lack of observation of a signal in other electromagnetic bands does not allow us to determine the nature of FRBs,” explains Andrea Possenti, “but it allows us to start excluding some hypotheses, such as that they are associated with normal Supernova events occurring in the Universe near us.”
Equally difficult to calculate is the distance traveled by these signals. The analysis of the properties of the one observed ‘live,’ based on the recording of slightly different arrival times as the observation wavelength varies, indicates that the source must have been up to 5.5 billion light-years away from us. “From the calculations,” explains Daniele Malesani, an Italian astronomer at the University of Copenhagen, who participated in the observational campaign following the discovery of the FRB, “it can be estimated that in just a few milliseconds that source released as much energy as our sun radiates in an entire day.”
The team then managed to measure for the first time another characteristic of the FRB: the polarization of the radio signal of the burst. Polarization can be thought of as the direction in which electromagnetic waves ‘vibrate’ as they propagate through space and is either linear or circular. The radio emission associated with the burst observed in real-time indicates a circular polarization greater than 20 percent, while no significant linear polarization was recorded. “Cosmic sources known to have radio emissions with significant circular polarization and low or no linear polarization are rare,” specifies Possenti. “This would suggest an emission process occurring near magnetic fields and electrically charged gas. On one hand, magnetic fields would favor the generation of circular polarization, while their combination with charged gas could make the observation of linear polarization impossible. It’s interesting to note that similar conditions are found near the centers of galaxies. However, we will truly understand the nature of FRBs,” concludes Possenti, “when we capture one in another band of the electromagnetic spectrum.”
In addition to Possenti, the most promising experiment hunting for sources of this type, called SUPERB (SUrvey for Pulsars & Extragalactic Radio Bursts), involves Marta Burgay, also from INAF-Osservatorio di Cagliari, and Caterina Tiburzi (INAF associate and PhD student at the University of Cagliari), who explain: “We expect to capture 5 to 10 more FRBs red-handed in 2015.” SUPERB is based in Parkes but involves numerous instruments, including the Sardinia Radio Telescope, the large INAF radio telescope located in Sardinia.
In the image: artistic representation of a Fast Radio Burst (FRB) whose polarized signal is captured by the Parkes radio telescope in Australia. Credits: Swinburne Astronomy Productions
For more information:
the article A real-time fast radio burst: polarization detection and multiwavelength follow-up by E. Petroff et al. published online on the website of the Monthly Notices of the Royal Astronomical Society
Article taken from Media Inaf