Astronomers have discovered rapid gas flares emanating from a white dwarf, a phenomenon never seen before.
The exceptionally gassy star is part of a binary system known as a dwarf nova. The cataclysmic variable star system consists of a Sun-like donor star closely orbiting a white dwarf.
Dwarf novae are known for their fiery outbursts. As they accrete material stolen from their companion, white dwarfs expel excess gas in the form of a single, narrow jet. Neutron stars and black holes exhibit similar behaviors.
The outburst witnessed by researchers at Oxford University was different. What first appeared as a constant jet turned out to be a rapid succession of flares.
The unusual flares were seen emanating from SS Cygni, an oft-studied star considered by astronomers to be the prototype dwarf nova. The variable star system is located in the northern constellation Cygnus.
Scientists were able to image the series of flares in unprecedented detail using radio telescopes. As the data revealed, the series of rapid flares ended with a crescendo — a massive, high-energy flare lasting just 15 minutes.
“Many of astrophysics’ most compelling studies have been based on studying SS Cyg,” lead researcher Kunal Mooley, an astrophysics research fellow at Oxford, said in a news release. “The latest, a detection of a rapid, radio flare — especially a fast, bright flare towards the end of the outburst, is highly unusual and demonstrates that there may even be some new physics at play.”
“We expected to see slow variation flares, but found fast, rapid, cone-like spikes of activity and observed an enormous amount of energy being released in a time-span as short as ten minutes,” Mooley said. “Nothing like this has ever been seen before in a dwarf nova system.”
Researchers say their discovery, described in the Monthly Notices of the Royal Astronomical Society, will force astronomers to reconsider their stellar models for white dwarfs and other variable systems.
“Moving forward, theorists should work with observers to find the answer to why these rapid flares occurred in SS Cyg,” Mooley concluded. “To really understand the process of gas accretion and gas expulsion in white dwarf systems — especially dwarf novae, similar studies should be carried out on other astrophysical systems.”
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