PATHFINDERS
LOFAR CONTRIBUTES TO NEW SOLAR ERUPTION WARNING SYSTEM
Above: Artist’s impression of a DISTURB antenna station.
BY MISCHA BRENDEL (ASTRON) The design of a new solar radio telescope that works in conjunction with LOFAR to provide alerts on solar eruptions is now complete. Appropriately named DISTURB, (Disturbance detection by Intelligent Solar radio Telescope of (Un)perturbed Radiofrequency Bands), its aim is to quickly alert other facilities to current and past solar radio interference on Earth. The design of DISTURB came from the Netherlands Institute for Radio Astronomy (ASTRON), S[&]T (Science [&] Technology Corporation) and KNMI (the Royal Netherlands Meteorological Institute). Solar eruptions produce radio waves and sometimes also large amounts of UV and X-ray radiation that reach Earth, as well as large pockets of gas that typically arrive at Earth three days later. These gas clouds give us beautiful auroras but can also disturb
or damage electrical systems and disrupt GPS navigation. DISTURB detects the radio waves of solar eruptions in ‘real-time’; when the sun becomes over 4,000 times brighter than usual – and thus emits far more radio waves – DISTURB immediately alerts KNMI, the Dutch Ministry of Defence (both of which ordered the design of this solar radio telescope) and the LOFAR radio telescope, an SKA pathfinder. LOFAR can then immediately ‘turn its eye’ on the Sun as well and start more detailed observations. DISTURB will track all radio waves with a wavelength between 10cm and 100m. For this, the solar radio telescope uses five different kinds of antennas, with which we can measure the amount of radio noise coming from the sun on over 600,000 different wavelengths. The antennas
for the longest wavelengths are nearly identical to the ones LOFAR uses (LOFAR observes radio waves above 1.25m in wavelength); all others are either new antennas or re-used from parts of a design which LOFAR made for SKA during the design phase. Although DISTURB will initially consist of a single antenna station, the DISTURB consortium aims to later have several DISTURB stations, distributed globally – just as LOFAR has. And also just as with LOFAR, DISTURB will send all its data to a central point. There is however one big difference: whereas LOFAR needs measurements to be synchronized up to a billionth of one second, for DISTURB this accuracy only needs to be around one tenth of a second, making it far easier to combine than LOFAR. The next step is to find funding to turn the design into an actual prototype.
CHIME DETECTION MAY RESOLVE MYSTERIOUS ORIGIN OF FRBS SOURCE: MCGILL UNIVERSITY, CANADA The close proximity of a high energy pulse detected by CHIME, an SKA pathfinder facility located in Canada, suggests magnetars may be the source of some fast radio bursts. New data from a Canadian-led team of astronomers strongly suggest that magnetars - a type of neutron star believed to have an extremely powerful magnetic field - could be the source of some fast radio bursts (FRBs). Though much research has been done to explain the mysterious phenomenon, their source has thus far remained elusive and the subject of some debate within the astrophysics community. On 28 April 2020, a team of approximately 50 students, postdocs and professors from the Canadian Hydrogen Intensity Mapping Experiment (CHIME) Fast Radio Burst Collaboration detected an unusually intense radio burst emanating from a 24
nearby magnetar located in the Milky Way. In a study published recently in Nature, they show that the intensity of the radio burst was three thousand times greater than that of any magnetar measured thus far, lending weight to the theory that magnetars are at the origin of at least some FRBs. “We calculated that such an intense burst coming from another galaxy would be indistinguishable from some fast radio bursts, so this really gives weight to the theory suggesting that magnetars could be behind at least some FRBs,” said Pragya Chawla, one of the co-authors on the study and a senior PhD student in the Physics Department at McGill University. One theory hypothesized FRBs to be extragalactic magnetars - young extremely magnetic neutron stars that occasionally flare to release enormous amounts of energy.
“So far, all of the FRBs that telescopes like CHIME have picked up were in other galaxies, which makes them quite hard to study in great detail,” said Ziggy Pleunis, also senior PhD student in McGill’s Physics Department and one of the co-authors of the new study. “Moreover, the magnetar theory was not supported by observations of magnetars in our own galaxy as they were found to be far less intense than the energy released by extragalactic FRBs until now.” Smoking-gun proof of a magnetar origin for some FRBs would come from the simultaneous detection of an extragalactic radio burst and an X-ray burst. However, this will likely only be possible for nearby FRBs. Fortunately, CHIME/FRB is discovering these in good numbers which should help identify the source eventually.
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