Associate Professor Natasha Hurley-Walker, alongside then-undergraduate Csanad Horvath, identified a unique energy pulse while analyzing archival data from the Murchison Widefield Array (MWA), a precursor to the Square Kilometre Array Observatory (SKAO). The pulse, observed every three hours and lasting 30-60 seconds, represents the longest-period radio transient detected to date.
Long-period radio transients, a relatively recent discovery in astrophysics, have puzzled scientists with their unknown origins. The Curtin researchers now believe they have pinpointed the source of this mysterious signal, offering valuable insights into the phenomenon.
Previous detections have been challenging due to the dense stellar environments within our galaxy, where numerous stars obscure the origins of the emissions. Hurley-Walker likened the situation to the overwhelming visual of stars in 2001: A Space Odyssey, remarking, "The long-period transients are very exciting, and for astronomers to understand what they are, we need an optical image. However, when you look toward them, there are so many stars lying in the way that it's like 2001: A Space Odyssey. 'My god, it's full of stars!'."
The newly identified transient, named GLEAM-X J0704-37, stands out by its location on the outskirts of the Milky Way, in a sparse region of space within the Puppis constellation, about 5,000 light-years away.
"This new discovery lies far off the Galactic Plane, so there are only a handful of stars nearby, and we're now certain one star system, in particular, is generating the radio waves," said Hurley-Walker.
The precise location was determined using the MeerKAT telescope in South Africa. Follow-up observations with Chile's SOAR observatory identified the system's central star as a low-mass M dwarf, a stellar type constituting 70% of the Milky Way's stars but invisible to the naked eye.
However, the energy output raised questions. "An M dwarf alone couldn't generate the amount of energy we're seeing," explained Hurley-Walker. "Our data suggests that it is in a binary with another object, which is likely to be a white dwarf, the stellar core of a dying star. Together, they power radio emission."
The team continues to study the system to solidify the explanation for this extraordinary cosmic event. Interestingly, they found archival evidence indicating GLEAM-X J0704-37 has been active for at least a decade, and possibly longer, suggesting that additional long-period transients may await discovery in similar archives.
MWA Director, Professor Steven Tingay, highlighted the critical role of the facility in this discovery. "These long-period radio transients are new scientific discoveries and the MWA has fundamentally enabled the discoveries," he said.
"The MWA has a 55-petabyte archive of observations that provide a decade-long record of our Universe. It is like having the data storage equivalent of 55,000 high-end home computers - one of the biggest single collections of science data in the world. It is an absolute gold mine for discovering more phenomena in our Universe, and the data are a playground for astronomers," Tingay added.
The findings were published in The Astrophysical Journal Letters.
Research Report:A 2.9-hour periodic radio transient with an optical counterpart
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