New Radio Telescope in South Africa Observed Giant Outbursts From Neutron Star

The first scientific results using the new Karoo Array Telescope (KAT-7) in South Africa, the pathfinder radio telescope for the $3 billion global Square Kilometre Array (SKA) project, have been published by an international team of astronomers this week.

They could observe two extremely powerful blasts in a binary neutron star system known as Circinus X-1, while using the seven-dish KAT-7 telescope and another 26 m radio telescope just when the system was firing energetic matter from its core into the surrounding system in extensive, compact `jets' that flare brightly, details of which are visible only in radio waves.

Circinus X-1 is an X-ray binary (or two-star system) where one of the companion stars is a high-density, compact neutron star (a neutron star is an extremely dense and compact remnant of an exploded star and only 20km in diameter.) When the two stars are at their closest the gravity of the dense neutron star pulls material from the companion star resulting in a powerful jet of material blasting out from the system.

During the time astronomers, including a team from the University of Southampton, observed Circinus X-1 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. The results appear in the latest issue of the journal Monthly Notices of the Royal Astronomical Society (MNRAS).

Dr Armstrong, one of the astronomers, said: "These types of observations are crucial for understanding the processes of both accretion of matter onto extremely dense systems, such as neutron stars and black holes of both about the sun's mass, and also the so-called supermassive variety we now know to be at the centre of most galaxies."

KAT-7 is the world's first radio telescope array consisting of composite antenna structures. It is the test array for MeerKAT, a much larger radio array, which is itself in turn a precursor for the dish-based component of the SKA.

The MNRAS study was carried out as part of the development for the ThunderKAT project on MeerKAT, which will find many more of these types of systems in the galaxy and search for new types of radio systems that change rapidly with time.

Professor Fender, who is co-leader of the MeerKAT project, explained that "this project will test the extremes of physics, density, temperature, pressure, velocity, gravitational and magnetic fields, and are beyond anything achievable in any laboratory on Earth. 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, probe relativistic accretion and understand the budget of kinetic feedback by such events in the ambient medium."