High resolution rapid response observations of compact radio sources with the Ceduna Hobart Interferometer (CHI)

Abstract

Context. Frequent, simultaneous observations across the electromagnetic spectrum are essential to the study of a range of astrophysical phenomena including active galactic nuclei. A key tool of such studies is the ability to observe an object when it flares i.e. exhibits a rapid and significant increase in its flux density. Aims. We describe the specific observational procedures and the calibration techniques that have been developed and tested to create a single baseline radio interferometer that can rapidly observe a flaring object. This is the only facility that is dedicated to rapid high resolution radio observations of an object south of −30 degrees declination. An immediate application is to provide rapid contemporaneous radio coverage of AGN flaring at γ-ray frequencies detected by the Fermi Gamma-ray Space Telescope. Methods. A single baseline interferometer, the Ceduna Hobart Interferometer (CHI), was formed with radio telescopes in Hobart, Tasmania and Ceduna, South Australia. A software correlator was set up at the University of Tasmania to correlate these data. Results. Measurements of the flux densities of flaring objects can be made using our observing strategy within half an hour of a triggering event. These observations can be calibrated with amplitude errors better than 15%. Lower limits to the brightness temperatures of the sources can also be calculated using CHI.

HUNTING FOR TREASURES AMONG THEFERMIUNASSOCIATED SOURCES: A MULTIWAVELENGTH APPROACH

“…In follow-up observations on 26 August 2012 with the two element Ceduna Hobart Interferometer (CHI, Blanchard et al 2012) which has a resolution of 6.6 milliarcsecond at the observed frequency of 6.7 GHz, source A1 in J 0143.6-5844 was detected with a flux density of 25 ± 4 mJy. This compares to a flux density of 26 ± 3 mJy measured by ATCA at the adjacent frequency of 5.5 GHz.…”

Multiwavelength and parsec‐scale properties of extragalactic jets

“…In 2007, the TANAMI 1 program started monitoring the brighest extragalactic jets in the Southern sky (below −30 • declination) using the combination of high-resolution VLBI observations at 8.4 and 22.3 GHz (Ojha et al 2010) and corresponding radio monitoring with the Australian Compact Array (ATCA, Stevens et al 2012) and the Ceduna telescope (Blanchard et al 2012), in the optical/UV with Swift/UVOT and Rapid Eye Mount (Nesci et al 2013), in the X-rays with Swift/XRT and all-sky observations at γrays by Fermi/LAT.…”

The Long Baseline Array

“…The University of Tasmania operates the Hobart and Ceduna telescopes, and has operated these as a singlebaseline array for rapid-response VLBI observations (Blanchard et al, 2012). The University of Tasmania also operates the AuScope geodetic array of three 12 m telescopes (Lovell et al, 2013).…”