SANTA CRUZ DE TENERIFE, 7 Aug. (EUROPA PRESS) –
An international study conducted recently, using data from the Gran Telescopio Canarias (Grantecan) at the Roque de los Muchachos Observatory in La Palma, has pinpointed a plasma bubble as the origin of the enduring emission detected in certain fast radio bursts (FRB). These bursts are considered some of the most powerful and enigmatic cosmic events in the Universe. The findings have provided insights into the ‘engine’ responsible for these mysterious sources, with the results published in ‘Nature’.
Fast radio bursts (FRBs) were discovered slightly over ten years ago, emitting millisecond-long pulses that release an immense amount of energy in the radio wave spectrum, distinguishing them as one of the most energetic occurrences observed thus far. Despite this, the physical mechanisms that lead to these bursts remain largely unknown, presenting one of the most compelling unresolved questions in contemporary astrophysics.
In certain instances, the brief flash of an FRB is accompanied by a less potent, enduring radio emission. Presently, an international consortium, spearheaded by the Italian National Institute for Astrophysics (INAF) and involving the Institute of Astrophysics of Andalusia (IAA-CSIC), has demonstrated that this lasting radiation originates from a plasma bubble, shedding light on the nature of these enigmatic cosmic incidents.
This recent study, involving an international team from research institutes and universities in Italy, China, the United States, Spain, and Germany, has documented the faintest enduring radio emission ever recorded for an FRB. This pertains to FRB20201124A, a fast radio burst emanating from a galaxy located approximately 1.3 billion light-years away from Earth.
Initial observations were conducted utilizing the Very Large Array (VLA) radio telescope in the United States. These observations enabled the research team to validate the theoretical forecast that a plasma bubble is the source of the lasting radio emission from fast radio bursts.
“Through our observations, we have been able to confirm that the persistent emission identified in certain fast radio bursts behaves as anticipated by the nebular emission model, resembling a ‘bubble’ of ionized gas enveloping the central engine generating the FRB,” elucidated Gabriele Bruni, a researcher at INAF in Rome and the primary author of the recent paper. “Specifically, through radio observations of FRB20201124A, one of the nearest bursts to Earth, we managed to measure the feeble enduring emission emanating from the same location as the FRB,” he further stated.
FRB 20201124A is classified as a rare recurrent event, with only around 10% of the some 800 known fast radio bursts exhibiting reoccurrence. It was initially detected on November 24, 2020, and in March 2021, fast radio bursts were once again registered from the same sector of the sky.
“This circumstance enabled the determination of its position within the host galaxy with a margin of error of a few milliarcseconds,” detailed Angela Gardini, a researcher at the IAA-CSIC and one of the co-authors of the study. “Its precise location and relative proximity, in contrast to other FRBs, rendered it an ideal subject for investigating the physical conditions of its surroundings,” she added.
OBSERVATIONS WITH MEGARA AT THE GTC
In an antecedent investigation, analysts had identified enduring emission in the host galaxy of this FRB, though they were unable to precisely determine the burst’s position to correlate the two phenomena. For this latest study, the team executed an observation campaign across different bands, a critical step in distinguishing the compact source from the faint diffused emission.
Notably, the observations carried out with the NOEMA interferometer, situated on the Plateau de Bure in the French Alps, and the MEGARA instrument on the Gran Telescopio Canarias (GTC or Grantecan), stationed at the Roque de los Muchachos Observatory (ORM) in La Palma, played a decisive role.
“Observations with the MEGARA instrument attained a resolution akin to the radio resolution of the VLA, facilitating the scrutiny of the FRB environment in an unprecedented detail and unveiling the existence of a compact radio source, the FRB plasma bubble, ensconced within a star-forming region,” declared Romano Corradi, the director of Grantecan. “These outcomes serve as a testament to how the fusion of the expansive collecting area of GTC, the leading optical and infrared telescope globally, in conjunction with the prowess of its instruments, is furnishing exceptional results that enhance our comprehension of the Universe,” he appended.
The research has also aided in ascertaining the nature of the mechanism driving these mysterious bursts. According to the recent data, the phenomenon is underpinned by a magnetar (a highly magnetized neutron star) or a high-accretion X-ray binary system, a category of binary wherein a neutron star or black hole syphons matter from a companion star at extremely high rates.
In essence, winds produced by the magnetar or the X-ray binary system have the capacity to “inflate” the plasma bubble, instigating the enduring radio emission, evidencing a direct physical correlation between the FRB engine and the bubble, located proximately.
“Grasping the nature of the enduring emission associated with FRB20201124A aids in filling a portion of the puzzle regarding the essence of these mystifying cosmic sources,” concluded Bruni.
