Strange radio burst raises new questions

(ORDO NEWS) — Astronomers have discovered only the second example of a highly active, repetitive fast radio burst (FRB) with a compact source of weaker but constant radio emission between bursts.

First discovered in 2019, scientists used the National Science Foundation’s Carl G. Jansky Very Large Array (VLA) and other telescopes to study the object.

The object, named BRV 190520, was discovered by the 500m Aperture Spherical Radio Telescope (FAST) in China.

The outburst from the object occurred on May 20, 2019 and was detected in the data of this telescope in November of the same year. Follow-up observations at FAST showed that, unlike many other FRBs, this object emits frequent, repetitive bursts of radio waves.

MBM observations in 2020 pinpointed the object’s location, while visible-light observations with the Subaru telescope in Hawaii showed it to be on the outskirts of a dwarf galaxy nearly 3 billion light-years from Earth. The MBM observations also showed that the object constantly emits weaker radio waves between bursts.

The combination of repetitive bursts and constant radio emission between them, emanating from a compact region, distinguished the 2016 object, named FRB 121102, from all other FRBs known so far.

Astronomers suggest that there may be either two different mechanisms that generate FRBs, or objects that contribute to their formation reproduce dissimilar processes at different stages of their evolution.

Leading candidates for the role of FRB sources are superdense neutron stars left after the explosion of a massive star in the form of a supernova, or neutron stars with superstrong magnetic fields, called magnetars.

An independent distance measurement based on the Doppler shift of the galaxy’s light caused by the expansion of the universe determined that the galaxy was nearly 3 billion light-years from Earth. However, the flare signal shows such a scatter that usually indicates a distance of about 8 to 9.5 billion light years.

“This means that there is a lot of material near the FRB that could confuse any attempt to use it to measure gas between galaxies,” said Kshitij Aggarwal, a graduate student at West Virginia University (WVU). “If this is the case with others, then we cannot count on the use of the BRV as space measurements,” he added.

Astronomers have speculated that FRB 190520 may be a “newborn” still surrounded by dense material ejected by a supernova explosion that left behind a neutron star.

When this material eventually scatters, the dispersion of the burst signals will also decrease. According to them, under the “newborn” scenario, recurring bursts can also be characteristic of younger DFS and decrease with age.

“The field of FRM is now developing very rapidly, and new discoveries appear every month. However, big questions still remain, and this object gives us complex clues to these questions,” said WVU’s Sarah Burke-Spolaor.

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