South African Telescope Reveals Binary Neutron Star System Spewing Jets

A binary neutron star system known as Circinus X-1 spews energetic matter from its core into the surrounding system in the form of compact jets. Now, astronomers have observed this system for the first time. Using the Karoo Array Telescope (KAT-7), they've revealed unprecedented details about the star system.

Circinus X-1 is actually an X-ray binary system, which means that it consists of two stars. One of the stars is a high-density, compact neutron star, which is an extremely dense remnant of an exploded star. These two stars orbit each other at a rapid pace, spinning around each other in an elliptical orbit once every 16.5 days. When the two stars are at their closest, the gravity of the dense neutron star actually pulls material from the companion star. A powerful jet of material then shoots from the system.

Yet these particular flaring jets are only visible in radio waves. Fortunately, the new instrument could detect them. During the time that the astronomers observed this star system, they saw it flare twice at levels among the highest observed in recent years. In fact, the astronomers observed the full flare cycle in unprecedented detail.

"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," said Richard Armstrong, an SKA SA Fellow at the University of Cape Town, in a new release. "The dramatic radio flares happen when the matter Circinus X-1 has violently ejected slows down as it smashes into the surrounding medium."

These observations have allowed the astronomers to learn a little bit more about the binary star system. In fact, this particular system is a perfect laboratory for relativistic jet astrophysics in the southern hemisphere. It's also an excellent control to the large population of jets associated with accreting black holes.

"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 center of most galaxies," said Armstrong.

The findings are published in Monthly Notices of the Royal Astronomical Society.