Active Galactic Nuclei (AGN) are compact regions which exist at the centre of many galaxies and emit radiation across the electromagnetic spectrum. The radiation is believed to result from matter accreting onto a super-massive black-hole at the centre of the galaxy. Blazars are a subset of AGN and are variable sources, which are thought to have an intense, relativistically beamed component of emission directed along, or close to the line of sight to the Earth.
PKS 1510-089 is one such object and on October 19, PhD student Faith Hungwe working with Prof R. Booth in collaboration with Dr R. Ojha of NASA/GSFC, while doing her regular stint as Flare Advocate for the Large Area Telescope (LAT, the main instrument aboard the Fermi Gamma Ray Space Telescope), issued an Astronomer's Telegram together with R. Ojha and M. Dutka, reporting a record gamma-ray flux level for the source.
This is the highest gamma-ray flux ever reported for this source and the second highest flux ever recorded by the Fermi/LAT (ATel #3694). The Astronomer's Telegram alerted the astronomical community to this event, but more directly, Faith also alerted astronomers at HartRAO and in the SA KAT office who, for the first time, had access to a fully operational KAT-7 telescope and were able to bring it into operation with immediate effect.
25 Oct 2011: Peak of PKS 1510-089 radio flare (initial gamma ray flare reported on Oct 20)
The Kat-7 team received notification of the PKS 1510-089 gamma-ray flare via ATEl #3694 on the evening of October 20th. An initial 6-hour observation of the target was done on the morning of October 21st. The observation strategy used 3C 273 as a bandpass calibrator and PKS 1508-055 as a gain calibrator. The bandpass was visited hourly, and the gain calibrator every 5 minutes. An example of the images obtained is shown above.
October 2011: Flux curve of PKS 1510-089 showing delayed radio flaring
A total of 10 observations spaced over two weeks were made. Each of these was imaged separately and an estimate of the flux of PKS 1510-089, together with an uncertainty (10 mJy on average), was obtained.
The resultant data as shown above, appear to capture the radio brightening of the source well, and show good correlation with radio data produced at other observatories, including those taken at HartRAO.