Fast Radio Bursts are fleeting but powerful bursts of radio waves, originating billions of lightyears away. Some, like FRB 20121102A, are known to repeat, offering valuable insights into their nature. The recent focus, however, has been on FRB 20190520B, a new repeating source.

The discovery of FRB 20190520B was made possible through the 500-m FAST telescope in China. Unlike its counterparts, this FRB is associated with a persistent radio wave source, hinting at a hypernebula - a dense, highly magnetized plasma cloud, illuminated by an enigmatic source. Such a phenomenon is still largely mysterious to astronomers.

The EVN's collaborative effort, spanning countries including Germany, Poland, Italy, the Netherlands, Sweden, Latvia, and the United Kingdom, has been instrumental in this research. Combining data from across Europe, the network achieved an unprecedented resolution, enabling the creation of ultra-sharp images. These images have been crucial in studying FRB 20190520B and its surroundings.

Dr. Shivani Bhandari, lead author and affiliated with ASTRON, JIVE, the University of Amsterdam, and CSIRO Space and Astronomy, shared, "With our EVN observations of FRB 20190520B we were able to constrain the size of the potential hypernebula to be less than 30 light years in diameter; that's three times the size of the famous Crab nebula in our own Milky Way galaxy." The team estimates the luminosity of this object to be around a hundred thousand times that of the Sun, showcasing its extraordinary energy.

The study, published in The Astrophysical Journal Letters, also explores the potential origins of such FRBs. A leading theory suggests they are produced by magnetars - highly magnetic neutron stars. These stars, remnants of supernovae, could emit a powerful wind of charged particles, forming a nebulous region in their vicinity. This theory aligns with the observed persistent radio light from some FRBs. The age of the potential magnetar associated with FRB 20190520B is estimated to be between 4 and 1,900 years, with the nebula being at least 900 years old. Dr. Bhandari adds, "This observation suggests that there may be a sub-population of young FRB sources embedded in luminous nebulae."

Another intriguing possibility is that the hypernebula is powered not by magnetic decay, but by gravitational potential energy. This would imply FRBs being produced in the powerful outflows from a black hole or a neutron star consuming matter from a nearby companion star at extremely high rates.

Following the discovery of FRB 20121102A, FRB 20190520B becomes the second to be associated with a potential hypernebula. Dr. Benito Marcote, second author of the paper, notes, "These FRBs are 'twins' because they are both active repeaters in low-mass dwarf host galaxies and are embedded in extreme and dynamic environments." This revelation adds a new dimension to the study of FRBs, suggesting that the youngest and most energetic among them might be embedded in such hypernebulae.

Astronomers continue to grapple with the origins and nature of FRBs. These latest findings, while shedding light on some aspects, also raise new questions about the diversity of astronomical objects capable of producing such intense radio bursts. Future observations are expected to delve deeper into whether all FRBs originate from magnetars or if other cosmic phenomena can also play a role.

Research Report:Constraints on the persistent radio source associated with FRB 20190520B using the European VLBI Network

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