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Binary Star System

South Africa's New Radio Telescope Reveals Giant Outbursts from Binary Star System

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A new study published in Monthly Notices of the Royal Astronomical Society has revealed the first significant finding from the new Karoo Array Telescope (KAT-7) in South Africa, the pathfinder radio telescope for the $3 billion global Square Kilometre Array (SKA) project – a giant outburst detected from a binary star system.

Astronomers used the KAT-7 telescope and a 26 metre radio telescope to observe a neutron star system called Circinus X-1.  This is a two star system, in which both stars orbit each other in an elliptical formation and one of the stars is a high-density, compact neutron star.

While observing Circinus X-1, astronomers detected an immense jet of energetic matter blasting out at the point in which the two stars were at their closest.  This energetic stream is only visible in radio waves. The system flared twice at levels among the highest observed in recent years. KAT-7 was able to catch both of these flares and follow them as they progressed.

"One way of explaining what is happening is that the compact neutron star gobbles up parts of its companion star and then fires much of this matter back out again," explains Dr Richard Armstrong, an SKA SA Fellow at the University of Cape Town and lead author of the paper. "The dramatic radio flares happen when the matter Circinus X-1 has violently ejected slows down as it smashes into the surrounding medium."

KAT-7 is the world's first radio telescope array consisting of composite antenna structures.  According to Professor Fender, who is co-leader of the project: "It provides a unique glimpse of the laws of physics operating in extraordinary regimes. Nearly all such events are associated with transient radio emission. By studying radio bursts from these phenomena, we can pinpoint the sources of explosive events”.

By April Holloway

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