Astronomers identify rare star system behind eight-minute radio pulses

Researchers at Curtin University’s International Centre for Radio Astronomy Research have tied repeating radio bursts to a white dwarf and Sun-like star orbiting each other in a system called GPM J071507−114153. The finding is the first clear case of radio pulses from a white dwarf paired with a Sun-like star and could help explain a little-understood class of stellar transients.

Why it matters: - The discovery is the first time astronomers have detected radio pulses from a white dwarf orbiting a Sun-like star. - The finding expands understanding of long-period transients, a class of objects that produce radio signals that turn on and off over minutes to hours. - Around a dozen long-period transients have been identified since the first one was found by the same ICRAR team in 2021. - The result could help scientists figure out which star in similar binary systems is actually generating the radio bursts.

What happened: - Scientists at the Curtin University node of the International Centre for Radio Astronomy Research linked mysterious eight-minute radio pulses to the binary system GPM J071507−114153. - The system contains a white dwarf and a G-type star similar to the Sun. - Dr Sam McSweeney, a commissioning scientist with the Square Kilometre Array Observatory, made the discovery while working as a researcher at ICRAR. - The study, titled “A long-period transient with a Sun-like companion,” was published overnight in Nature Astronomy.

The details: - A white dwarf is the dense core left behind when a star dies. - The team says the pulses were clear enough to show the white dwarf moving in orbit around its companion. - That motion indicates the radio pulses are coming from a region close to the white dwarf, or possibly from the white dwarf itself. - The team processed more than 100 hours of radio data at the Pawsey Supercomputing Research Centre to validate the white dwarf’s motion. - Associate Professor Natasha Hurley-Walker said the pulses from the white dwarf also let the team detect stellar flares on the Sun-like star. - Hurley-Walker said the team also saw the white dwarf moving behind a region with a strong magnetic field, most likely a stellar prominence, a large loop of plasma erupting from a star’s surface. - Hurley-Walker said radio wavelengths can detect storms on a star more than 5,000 light-years away. - The system was first found in a large survey using the MWA, or Murchison Widefield Array, which scanned the Milky Way visible from Australia. - The team then used the MeerKAT radio telescope in South Africa to pinpoint the system’s location. - The W.M. Keck Observatory on Maunakea, Hawaiʻi Island, confirmed the association with a G-type star through optical observations.

Between the lines: - The discovery suggests precursor telescopes are already powerful enough to find rare binaries that previously may have been missed. - McSweeney said the SKAO telescopes, once completed, should reveal many more such systems and much more detailed signal data. - The finding also reinforces ICRAR’s role in the early discovery of long-period transients. - The work connects radio astronomy with stellar activity on the Sun-like companion, which could help researchers study magnetic activity in distant stars.

What’s next: - Astronomers will keep building a larger sample of long-period transients to learn how they form and what drives their radio pulses. - Future observations with SKA-Low in Australia and SKA-Mid in South Africa are expected to uncover more systems like GPM J071507−114153. - The paper’s authors say the completed SKAO telescopes should provide a much more detailed view of these signals.