Fast Radio Bursts (FRBs) are one of the most recent open mysteries in modern astrophysics: within milliseconds they release one of the highest amounts of energy observable in cosmic phenomena. Discovered just over a decade ago, these strong radio-band flashes come from mostly extragalactic sources, but their origin is still uncertain and many efforts are being made by the astrophysical community worldwide to try to understand the physical processes at their origin.

In very few cases, the rapid flash that characterises fast radio bursts coincides with a persistent radio emission. New research led by the National Institute of Astrophysics (INAF) has recorded the weakest persistent radio emission ever detected so far for an FRB. It is FRB20201124A, a fast radio burst discovered in 2020, whose source is located about 1.3 billion light years away. In addition to the work of INAF researchers, the study sees the collaboration of UniTS (Roberta Tripodi), the University of Bologna, the University of Calabria, and the international participation of research institutes and universities in China, the United States, Spain and Germany.

The observations, made possible by the world's most sensitive radio telescope, the Very Large Array (VLA) in the US, have verified the theoretical prediction that a plasma bubble is at the origin of the persistent radio emission of fast radio bursts. The results were published today in the journal Nature.

The new work also helps to circumscribe the nature of the driving force behind these mysterious flashes. According to the new data, either a magnetar (strongly magnetised neutron star) or an X-ray binary with a very high accretion regime, i.e. a binary system formed by a neutron star or a black hole that accretes material from a companion star at a very high rate, would be at the basis of the phenomenon. It is in fact the winds produced by the magnetar, or the binary X system, that 'inflate' the plasma bubble that gives rise to the persistent radio emission. There is therefore a direct physical relationship between the FRB 'engine' and the bubble, which is located in its immediate vicinity.

‘A nebular origin for the persistent radio emission of fast radio bursts’, by Gabriele Bruni, Luigi Piro, Yuan-Pei Yang, Salvatore Quai, Bing Zhang, Eliana Palazzi, Luciano Nicastro, Chiara Feruglio, Roberta Tripodi, Brendan O'Connor, Angela Gardini, Sandra Savaglio, Andrea Rossi, A. M. Nicuesa Guelbenzu, Rosita Paladino.