17 Dec 2011: 14 hour observation of Circinus X-1 in quiescent state (7 antennas)
23 Dec 2011: 11 hour observation of Circinus X-1 shortly after flaring (6 antennas)
The bright region in the middle of the above two KAT-7 radio images, observed at 1822 MHz (with 256 MHz bandwidth), shows an object known as Circinus X-1 which has been under observation by astronomers for many years and continues to be of great scientific interest. Also shown are several supernova remnants (large loop mid bottom and smaller loop mid left) as well as serval other radio sources. Circinus X-1 is now thought to be a binary star system known as an X-ray binary (or microquasar) where one of the companions is believed to be a (very high density and compact) neutron star. The other star's type is not known. These objects are in an elliptical orbit around each other and, every 16 and a half days, draw close and material is pulled by the strong gravity of the neutron star from the other star. Scientist believe that the process of accretion of the material from the second object onto the neutron star is what results in the major flares in emission detected across a broad range of wavelengths. KAT-7 is being used to monitor Circinus X-1 over several flare cycles in order to provide scientists with useful information with which to further study this object.
For comparison, a the SUMSS catalog image of the same region (at 843 MHz and higher resolution) is shown below (click to enlarge):
(SUMMS image credit: D. Bock, M.I. Large and E.M. Sadler (1999) AJ 117, 1578-1593)