Astronomers have detected a rare, repeating radio signal from a binary star system located 5,000 light-years away, according to a study published in Nature Astronomy.
The system, designated GPM J071507−114153, emits pulses every eight minutes, a cycle that distinguishes it as a long-period radio transient (LPT). The white dwarf within this system completes a rotation every eight minutes.
Researchers have identified such pulses in a system containing a white dwarf—the dense remains of a dead star—orbiting a G-type star similar to our Sun for the first time. Previous sightings of LPTs involved smaller, cooler companions like red dwarfs. The system is described in the study titled “A long-period transient phenomenon with a Sun-like companion.”
The research team, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR), used a suite of global instruments to characterize the system. The Murchison Widefield Array in Western Australia first detected the pulses, while the MeerKAT telescope in South Africa pinpointed the object’s exact location. Both the Murchison Widefield Array and the MeerKAT telescope act as precursors to the SKA-Low and SKA-Mid projects.
To confirm the movement of the white dwarf within the system, researchers processed more than 100 hours of radio data at the Pawsey Supercomputing Research Centre in Australia.
“This is the first time that the pulses are clear enough to see the white dwarf moving in its orbit around its companion, so we know the pulsations come from a region close to the white dwarf, or possibly even from the white dwarf itself,” said Sam McSweeney, the study’s lead author, in a statement.
Observations also revealed evidence of magnetic interactions between the two stars. Researchers identified signs of stellar flares and a potential prominence—a large loop of plasma—on the G-type star. These events are analogous to solar storms that trigger auroras on Earth.
Natasha Hurley-Walker, a co-author of the study and associate professor, said that the emissions allowed researchers to register eruptions on the Sun-like star and observe the white dwarf passing behind a stellar prominence with a strong magnetic field.
The team used the W.M. Keck Observatory in Hawaii to analyze the visible light of the companion star, which allowed them to confirm its classification as a G-type star. Since the ICRAR team recorded the first LPT in 2021, researchers have identified approximately twelve such systems, but they are still investigating the specific mechanism generating the radio pulses.
What exactly is an LPT? A long-period radio transient (LPT) is a celestial object that emits radio transmissions that cycle on and off in intervals ranging from minutes to hours. These systems are rare, with only about a dozen identified since 2021.
Earlier identified LPT systems featured white dwarfs paired with small, cool red dwarfs. GPM J071507−114153 is the first instance where the white dwarf is paired with a G-type star, which is significantly more similar to our own Sun.
According to ICRAR, the radio pulses from GPM J071507−114153 remain active for approximately six hours before disappearing for 26 hours, repeating in a consistent cycle.
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