A team of researchers believes the flurry of radio waves emanating from deep space came from a bubble of plasma surrounding a compact object, one of the universe’s densest entities.
The waves were a fast radio burst, or FRB, an enigmatic class of radio waves characterized by their brilliance and their unpredictable lengths. Many are fleeting, but some are very reliable; one source described by a different team last year blinked every 22 minutes for 30 years.
Astronomers discovered the burst, called FRB20201124A, in 2020, spewing from a source about 1.3 billion light-years away. Last year, a different team of researchers found the most distant FRB yet, coming from a source about 10 billion light-years away. Thus, the more recently analyzed burst practically seems local. A paper published this week in Nature described the nature of its origin
“We were able to demonstrate through observations that the persistent emission observed along with some fast radio bursts behaves as expected from the nebular emission model, i.e. a ‘bubble’ of ionized gas that surrounds the central engine,” said Gabriele Bruni, a researcher at the National Institute for Astrophysics and lead author of the new paper, in an INAF release.
Fast radio bursts are flurries of radio waves that generate “as much energy in a thousandth of a second as the Sun does in a year,” according to NASA. They are brilliant in the truest sense, making them exciting sources of data for radio astronomers. FRB20201124A was scrutinized with the most sensitive radio telescope on Earth, the Very Large Array. The team determined that the FRB came from a bubble of plasma surrounding a dense object.
What kind of dense object could lie at the bubble’s center, you ask? There are a couple of possibilities, but both are very dense. The new data suggests that a magnetar—a strongly magnetized neutron star—may lie at its core. Another possibility is a binary system of a neutron star or a black hole taking voluminous amounts material from a smaller companion star. Winds produced by either source could effectively “blow” the plasma bubble surrounding it, according to a National Institute for Astrophysics release.
“Optical observations were an important element to study the FRB region at a spatial resolution similar to that of radio observations,” said study co-author Eliana Palazzi, also a researcher at INAF. “Mapping hydrogen emission at such a great level of detail allowed us to derive the local star formation rate, which we found to be too low to justify continuous radio emission.”
Like other reliable FRBs, FRB20201124A’s radio emissions are persistent. In fact, they are the weakest persistent radio emissions yet detected for an FRB. More observations of similar FRBs and their sources may clarify the conditions that generate the bursts in general, as well as the various types of bursts, of different strengths and persistences.
