Astronomers have traced repeating radio pulses to a white dwarf orbiting a Sun-like star more than 5,000 light-years away, using the signal to detect stellar flares and a likely stellar prominence.
Astronomers at the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR) have traced repeating radio pulses to a white dwarf orbiting a Sun-like star more than 5,000 light-years away. The system, GPM J071507-114153, is the first long-period transient with a white dwarf and a Sun-like companion for which the pulses are clear enough to show the white dwarf moving in its orbit.
The binary system consists of a low-mass white dwarf and a G-type star. It belongs to a rare class of objects known as long-period transients (LPTs), which switch their radio emission on and off over minutes to hours. Only about a dozen are known, since the first was found in 2021 by the same team.
Earlier LPTs with white dwarfs were mostly paired with smaller, cooler red dwarfs. Until now, it was unclear which star in these pairs produced the pulses.
"This is the first time the pulses are clear enough to see the white dwarf moving in its orbit around its companion, so we know that the pulsations are coming from a region close to the white dwarf, or possibly even from the white dwarf itself," said Dr. Sam McSweeney, an astronomer at ICRAR and a commissioning scientist with the Square Kilometre Array Observatory.
Dr. McSweeney and colleagues processed more than 100 hours of radio data at the Pawsey Supercomputing Research Centre to confirm the motion. They revealed stellar flares on the Sun-like star, similar to those that cause aurorae on Earth.
They also saw the white dwarf pass behind what is likely a stellar prominence, a huge loop of plasma erupting from the star’s surface.
"The pulses emitted by the white dwarf allowed our team to detect stellar flares on the Sun-like star, similar to those that create aurorae here on Earth," said Dr. Natasha Hurley-Walker, an astronomer at ICRAR.
"As a bonus, we also saw the white dwarf moving behind a region with a strong magnetic field, most likely a ‘stellar prominence,’ which is a large loop of plasma erupting from a star’s surface."
"It’s amazing that by using radio wavelengths we can detect the storms on a star over 5,000 light-years away."
The Murchison Widefield Array detected the source during a survey of the Milky Way, recording 214 pulses between December 2024 and September 2025. MeerKAT, in South Africa, detected another 33 in a follow-up campaign. Optical spectra from the W. M. Keck Observatory showed that the star at that location was a G-type star with an estimated mass close to the Sun’s and a temperature of about 5,500 kelvins.
The findings were published in the journal Nature Astronomy. The research gives astronomers a new way to test ideas about the role of magnetic fields in white dwarf systems and expands the range of binaries available for comparison within the long-period transient class.
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