It's not a fast radio burst, a pulsar, or a low-mass star that flares up every now and then. It is the radiating body in the radio field only for a few weeks, disappears at once, and returns again after a while. The researchers seek to understand what it is
Astronomers have discovered a strange, repeating radio signal near the center of the Milky Way, whose energy signature is unlike that of any other body ever studied, yet scientists are convinced it is of natural origin.
According to a new article accepted for publication in the Astrophysical Journal and posted on the server, the pre-publisher
arXiv , the energy source exhibits strange behavior. It appears bright in the radio spectrum for weeks at a time and then disappears completely within a day. This behavior does not fit the profile of any known type of celestial body, the researchers wrote in their study, and therefore may represent "a new class of objects discovered through radio imaging."
The radio source - known as ASKAP J173608.2−321635 - was detected by the Australian Square Kilometer Telescope, ASKAP, an array that includes 36 antennas with a diameter of 12 meters, which function as one and make the observatory one of the most sensitive radio observatories in the world. It is designed to analyze cosmic magnetism, detect black holes and investigate the origin of galaxies.
. In the ASKAP survey conducted between April 2019 and August 2020, the strange signal appeared 13 times, and never lasted more than a few weeks, the researchers wrote. This radio source is highly variable, appearing and disappearing without a predictable schedule, and does not appear to appear in other radio telescope data prior to the ASKAP survey.
When the researchers tried to match the energy source to observations from other telescopes – including the X-ray Chandra Space Telescope and the Swift Space Telescope, as well as the Infrared and Visible Light Survey Telescope in Chile, which can pick up near-infrared wavelengths, the signal disappeared completely. . With no visible emission anywhere else in the electromagnetic spectrum, ASKAP J173608.2−321635 is an enigma that defies known explanations.
Previous surveys have found low-mass stars that periodically flare up and emit radio energy, but these hot stars typically have corresponding X-ray radiation as well, the researchers wrote. Therefore they rule out this type of source.
Dead stars, such as pulsars and magnetars (two types of collapsed stars), are also unlikely explanations, the researchers wrote.. While pulsars can shine in the radio range, they have a regular cycle. They usually go through this process over hours rather than weeks. Magnetars bursting parallel to the radio field also in the X-ray field include a powerful X-ray counterpart with each of their bursts – again, unlike ASKAP J173608.2−
The most similar discovery is an event recorded in 2000, also in the center of the Milky Way galaxy and called GCRT - galactic center radio transient
To find out what the mysterious object is that radiates only in the radio range, the researchers need time to observe additional radio signals, and perhaps discover certain patterns that have not been seen so far. "We will be able to understand how unique ASKAP J173608.2-321635 really is and if it is related to the galactic plane, which should ultimately help us infer its nature." The researchers conclude.
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