Astronomers in Australia detect radio pulses repeating every eight minutes

The New York Post reported that astronomers in Australia detected radio pulses repeating every eight minutes from the star system GPM J071507−114153, located about 5,000 light-years from Earth, according to a study in Nature Astronomy.\n\nThe system pairs a white dwarf, the dense core remaining after a star dies, with a G-type star comparable to the sun in a mutual orbit. Researchers at ICRAR in Perth, Western Australia, said such pulses are usually tied to smaller, cooler red dwarf stars, so a sun-like companion is unusual. The result widens the known range of companion stars that can host this kind of radio emitter beyond red dwarfs. The object emerged during a broad radio scan of the Milky Way visible from Australia before its position was refined with a second telescope.\n\nOne member of the pair is a dead star spinning once every eight minutes, matching the observed radio pulse cadence, while the other is a sun-like star.

The study reports the first detection of radio pulses from a white dwarf in orbit around a sun-like star. Earlier long-period transients containing a white dwarf and another star left astronomers unsure which star produced the emissions.\n\nStudy lead author Dr Sam McSweeney, an ICRAR researcher, said the pulse clarity reveals the white dwarf moving around its companion, pointing to an origin close to or on the white dwarf. He made the detection while working at ICRAR, and the team used the signal to trace the white dwarf’s orbital motion.\n\nMcSweeney classifies these stellar pairs as long-period transients, objects whose radio emissions turn on and off over periods from minutes to hours. About a dozen long-period transients have been detected since the first was found by the same ICRAR team in 2021, and scientists are still trying to understand them.\n\nIn several previously found long-period transient systems containing a white dwarf and another star, researchers could not determine which star generated the radio pulses.

The new observation helps resolve that ambiguity by linking the pulsations to orbital motion near the white dwarf. Researchers at the Pawsey Supercomputing Research Centre worked through over 100 hours of radio data to confirm the white dwarf’s motion. The processing supported the conclusion that the emission comes from a region close to the white dwarf or from the white dwarf itself. Associate Professor Natasha Hurley-Walker said the white dwarf’s pulses enabled detection of stellar flares on the sun-like star like those producing aurorae on Earth, and revealed a likely stellar prominence. She said the team found the system in a large Murchison Widefield Array survey of the Milky Way visible from Australia and then used MeerKAT in South Africa to pinpoint its position. The survey instrument scanned the galaxy visible from Australia, while the South African telescope provided the precise sky position. After radio telescopes located the long-period transient, the W.M. Keck Observatory in Hawaiʻi confirmed its link to a G-type star using optical observations.

Optical follow-up in Hawaii verified that the companion matches a G-type classification similar to the sun.\n\nMcSweeney said precursor telescopes are already producing these discoveries, and once the SKAO telescopes are fully built, astronomers should find many more star systems and obtain detailed views of their signals. The researcher suggested completed SKAO facilities would increase the discovery rate and improve signal detail beyond current precursors.