Science & Technology (Commonwealth Union) – The phenomena of strange cosmic signals has always intrigued space enthusiasts and astronomers alike.
A global team of astronomers, led by researchers at the University of Sydney in Australia, has revealed the most definitive evidence yet about the source of a rare type of cosmic signal. In the process, they uncovered an unusual stellar system that offers scientists a natural setting to explore extreme physics.
Using CSIRO’s ASKAP radio telescope, the researchers observed a compact, dense star known as a white dwarf pulling material from its larger, less dense companion.
As this material spirals onto the white dwarf, it generates intense bursts of radio waves and X-rays, repeating in a cycle roughly every 1.4 hours.
The study appears in Nature Astronomy.
Lead author and PhD student Kovi Rose, from the University of Sydney’s School of Physics and CSIRO, explained that this marks the first confirmed identification of what astronomers call “long-period radio transients”—rare cosmic pulses detected from only a few distant areas of the Milky Way.
Rose indicated that for the first time, they have traced the origin of these signals, confirming they come from a ‘cataclysmic variable,’ an accreting white dwarf star.
Mr Rose pointed out that Long-period radio transients have been a source of confusion for astronomers for a long period of time.
He further indicated that they have only found roughly a dozen, and their origins have not been clear. Rose further pited out that at present, they have had the ability to demonstrate that the source for one of these transients arrives from a white dwarf actively drawing material from a companion star.
The newly discovered system, known as ASKAP J1745−5051, is made up of a white dwarf—a highly dense stellar remnant about the size of Earth but nearly as massive as the Sun—paired with a larger, low-mass red dwarf star that has roughly one-tenth of the Sun’s mass. The two stars are locked in a tight orbital dance, circling each other in just over an hour.
As the red dwarf loses material to the white dwarf, the infalling gas is heated to extreme temperatures and produces X-rays. Meanwhile, the interaction between stars and their magnetic fields triggers repeated bursts of radio waves, causing the signal to appear in regular, predictable intervals.
“These emissions are all tied to the orbital motion of the system,” explained Mr Rose. “But interestingly, the radio and X-ray signals don’t peak at the same time, which tells us they’re being produced in different regions of the system.”
The researchers determined that the radio signals likely arise where the magnetic fields of the two stars converge and interact with the charged material being stripped from the companion star, creating sharply focused bursts of radiation.
For the researchers of the study this was like unraveling a cosmic puzzle.Long-period radio transients were once believed to originate from slow-spinning neutron stars, or pulsars. Yet, current theoretical models indicate that neutron stars rotating this slowly should be incapable of generating such emissions.
This new finding lends support to an alternative theory: that at least some of these enigmatic bursts are produced by binary star systems involving white dwarfs.
“While a few similar objects had previously been associated with binary systems, this is the first case where we can directly observe both stars and witness the accretion process in progress,” said Professor Murphy, Head of School at the University of Sydney School of Physics and Chief Investigator at the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav).
