Astronomers trace repeating cosmic signals to white dwarf binary system
8 reported
An international research team led by the University of Sydney has identified the source of a mysterious class of repeating cosmic signals known as long-period radio transients. Using CSIRO’s ASKAP radio telescope in Australia, the scientists traced the signals to a rare stellar system called ASKAP J1745−5051, consisting of a white dwarf and a red dwarf locked in an extremely close orbit. The white dwarf, a dense remnant of a dead star roughly the size of Earth, is siphoning material from its red dwarf companion, which has about one-tenth the Sun’s mass. As the stolen matter spirals inward, the system emits radio waves and X-rays every 1.4 hours. The findings, published in Nature Astronomy, provide the first clear evidence linking these signals to a cataclysmic variable, or accreting white dwarf star. Lead author Kovi Rose, a PhD student at the University of Sydney and CSIRO, said the team confirmed the source for one of these transients comes from a white dwarf actively pulling material from a companion star. The system is only the second known long-period radio transient found to produce regular X-rays and the first where scientists have confirmed exactly what causes the periodic behavior.
What’s reported
The discovery was made by an international team led by the University of Sydney using CSIRO’s ASKAP radio telescope.
The source is ASKAP J1745−5051, a binary system with a white dwarf and a red dwarf in an extremely close orbit.
The white dwarf is roughly the size of Earth with a mass comparable to the Sun; the red dwarf has about one-tenth the Sun’s mass.
The two stars circle one another in just over an hour, and emissions repeat every 1.4 hours.
Radio and X-ray signals do not peak at the same time, indicating they are produced in different regions of the system.
The radio waves are likely produced where the stars’ magnetic fields collide with charged material flowing toward the white dwarf.
This is the first long-period radio transient where scientists have confirmed exactly what causes the periodic behavior.
The results were published in Nature Astronomy.
Key figures
Kovi Rose, PhD student, University of Sydney School of Physics and CSIRO, lead author
Professor Tara Murphy, Head of School, University of Sydney School of Physics, Chief Investigator at OzGrav
Sources: ScienceDaily
