Scientists spy winds gusting from odd binary systems at very high speeds

CAMBRIDGE, England, April 28 (UPI) -- Researchers at Cambridge have identified strong winds gusting outward from a pair of unique binary systems. The winds were clocked at approximately a quarter of the speed of light -- roughly 46,500 miles per second.

The winds are being expelled from a pair of binary systems known as "ultra-luminous X-ray sources."

Until the 1980s, researchers thought the only two sources of large quantities of X-rays were supermassive black holes and binary star systems, where one larger star or black hole is feeding on a companion star.

But researchers discovered a third group, binary systems boasting a dominant star with a more ferocious appetite. The friction of the heightened rate of consumption inspired more intense X-rays -- 10 to 100 times more than traditional binary systems, but not quite as much as supermassive black holes.

Recently, astronomers at Cambridge University identified a pair of ultra-luminous X-ray sources that were not like the others. They identified winds blowing both towards the dominant stellar object and away.

"This is the first time we've seen winds streaming away from ultra-luminous x-ray sources," Ciro Pinto a researcher at Cambridge's Institute of Astronomy, said in a news release. "And the very high speed of these outflows is telling us something about the nature of the compact objects in these sources, which are frantically devouring matter."

Pinto is the lead author of a new paper on the discovery, published this week in the journal Nature.

Researchers believe the intense pressure created by gas being sucked in from the less massive to the more massive companion is responsible for winds that blow some accumulating gas back outward, away from the dominant stellar object.

Scientists say the newly identified objects exceed the Eddington limit -- a ratio established by astronomer Arthur Eddington that puts limits on the amount of material an object of a certain mass can consume. Energy and mass coming in and being expelled as radiation must be balanced.

Accretion disks around these novel stars exceed the limit, creating intense pressure that pushes the disk farther from the star's gravitational hold, allowing even more dramatic external winds.

"By observing x-ray sources that are radiating beyond the Eddington limit, it is possible to study their accretion process in great detail, investigating by how much the limit can be exceeded and what exactly triggers the outflow of such powerful winds," added Norbert Schartel, a scientist with the European Space Agency.

Schartel and his colleagues are continuing to search the data archives of XMM-Newton, an X-ray space observatory, for evidence of similar binary systems.

"With a broader sample of sources and multi-wavelength observations, we hope to finally uncover the physical nature of these powerful, peculiar objects," Pinto said.