On November 30, 2024, a team from Curtin University, part of the International Center for Radio Astronomy Research (ICRAR), announced the discovery of a record-breaking energy burst from deep space, traced back to a binary system of a small red dwarf star and a white dwarf remnant.
The bright energy pulse, designated GLEAM-X J0704-37, was detected in archival low-frequency data from the Murchison Widefield Array (MWA). This radio wave signal appears every three hours, with bursts lasting between 30 to 60 seconds, marking it as an example of the longest period of a rare and extreme phenomenon known as 'long-period radio transients.'
First identified in 2006, long-period radio transients have puzzled astronomers for nearly two decades due to the difficulty in understanding how these phenomena generate radio waves. This research may help solve the mystery by identifying the potential source of these energy bursts.
Previous long-period radio transients were located in densely populated regions of the Milky Way, complicating the determination of the actual source of the radio wave bursts. Natasha Hurley-Walker, a team member and researcher at Curtin University, noted, 'To understand long-period transients, we need optical images, but when you look in their direction, there are so many stars around, like in 2001: A Space Odyssey.'
However, the team had luck with GLEAM-X J0704-37, which originates from 5,000 light-years away at the edge of the Milky Way, an area with fewer stars. 'Our new discovery is far from the galactic plane, so there are only a few stars nearby, and we are now confident that a specific binary star system produces the radio waves,' added Hurley-Walker.
The team utilized the MeerKAT telescope in South Africa to pinpoint the origin of GLEAM-X J0704-37 to a specific star. The next step is to uncover the characteristics of the star system emitting GLEAM-X J0704-37.
Using the Southern Astrophysical Research Telescope (SOAR) in Chile, scientists confirmed that one of the stars in the GLEAM-X J0704-37 source is a low-mass red dwarf star, also known as an 'M-dwarf.'
This presents a dilemma for the team. 'Red dwarfs are low-mass stars with only a fraction of the mass and luminosity of the Sun. They make up 70% of stars in the Milky Way, but none are visible to the naked eye,' explained Hurley-Walker. 'A red dwarf alone cannot produce as much energy as we observe.'
Through their data, the team found evidence that the red dwarf is part of a binary system with another object. They determined that this companion is likely a white dwarf, the remnant of a star similar to the Sun that has exhausted its nuclear fuel.
'Together, they produce radio emissions,' stated Hurley-Walker.
Hurley-Walker and colleagues suggest that a strong magnetic field in the system may cause the periodic energy burst emissions, similar to those seen in rapidly rotating neutron stars, or 'pulsars.' Since the source of GLEAM-X J0704-37 is located well above the Milky Way disk, researchers could rule out high-magnetic neutron stars, or 'magnetars,' as the source of this long-period radio transient.
The team is now working diligently to confirm the characteristics of this binary system and explain how GLEAM-X J0704-37 is generated.
Overall, the fact that GLEAM-X J0704-37 has been active for the past ten years and had gone undetected until now suggests that there may be more hidden long-period radio transients in archival data from various telescopes worldwide, including MWA.
'This long-period radio transient is a new scientific discovery, and MWA has fundamentally enabled these findings,' stated MWA Director Steven Tingay.
'MWA has an observational archive of 55 petabytes, providing a decade-long record of our universe. This is akin to having data equivalent to 55,000 high-end home computers—one of the largest scientific data collections in the world.'
'This is a goldmine for discovering more phenomena in our universe, and this data is a playground for astronomers.'