Observations of X-ray binaries using the Australia Telescope Compact Array - compact array broadband backend

Abstract

The exploration of radio emission from the relativistic jets of X-ray binaries has become key to understanding accretion onto compact objects. Upgrades to existing radio telescope arrays have improved the ability of these instruments to detect faint sources and their unique behaviours. In this thesis I address the use of one such instrument in observing several X-ray binary systems: the Australia Telescope Compact Array - Compact Array Broadband Backend (ATCA-CABB). Firstly, a study of the adverse effects that may arise when imaging spectrally variable sources using broad bandwidths, with emphasis on ATCA-CABB. Images are produced from model data and examined to find any false structures. I then discuss complications that such features may cause when attempting to interpret real structure in images.

Secondly, the results of attempts to observe the black hole X-ray binaries, GRO J1655-40 and XTE J1550-564, in quiescence with ATCA-CABB are presented. Upper limits from the non-detection of these sources are used in exploring the lower luminosity region of the radio/X-ray correlation for hard state black hole X-ray binaries and the implications of “universal” scatter is discussed.

Thirdly, a 16 day campaign observing the radio emission of the neutron star Xray binary Circinus X-1 over a complete orbit during an historically faint state is presented. Variability in the source is examined and corrected images are compared with archival maps in order to find any differences. I discuss my findings in terms of secular changes in jet geometry and behaviour.

Finally, the first successful millimetre detections of neutron star X-ray binaries Circinus X-1 and Scorpius X-1 are presented. Sub-arcsecond jet structure in Circinus
X-1 is compared to the existing centimetre maps, providing additional support for theories proposed earlier in the thesis. The radio to mm spectrum of both sources is estimated and discussed.

This thesis concludes with a description of the broader impacts of the above projects, as well as possibilities for future research in each field.

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