Astronomers trace 8-minute radio pulses to white dwarf orbiting a Sun-like star

Astronomers have traced a stream of mysterious radio pulses to an unusual pair of stars more than 5,000 light-years from Earth: a dead star rotating once every eight minutes and a companion closely resembling our own Sun.

The system, designated GPM J071507−114153, contains a white dwarf — the extremely dense remnant left when a star exhausts its nuclear fuel and sheds its outer layers — and a G-type star, the same general category as the Sun. The discovery was made by researchers at the Curtin University branch of the International Centre for Radio Astronomy Research (ICRAR) in Western Australia.

A first for this kind of stellar pair

Until now, astronomers had detected similar radio pulses only in systems pairing white dwarfs with smaller, cooler stars known as red dwarfs. The new finding marks the first time such signals have been identified in a system where a white dwarf orbits a Sun-like star.

The pair belongs to an unusual class of objects called long-period transients (LPTs), which produce radio emissions that switch on and off over periods ranging from minutes to hours. The same ICRAR team identified the first known example in 2021, and only about a dozen have been found since. Their origins remain poorly understood.

"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 lead author Dr Sam McSweeney, who made the discovery while at Curtin University's ICRAR branch and is now a commissioning scientist with the Square Kilometre Array Observatory.

Magnetic storms on the companion star

To confirm the finding and follow the white dwarf's orbital motion, the researchers analysed more than 100 hours of radio observations using computing resources at the Pawsey Supercomputing Research Centre. The signals also revealed massive magnetic storms on the companion star.

Astronomers had long struggled to determine which member of an LPT pair was responsible for the radio emissions. The new observations narrow the likely source to the vicinity of the white dwarf, offering fresh clues to one of the Milky Way's most puzzling signal classes.