We discuss the importance of the direct link between the most accurate radio and optical reference frames that will become possible with the next-generation space as-trometry missions in about a decade. The positions of more than 500 active galactic nuclei that are common in the precise Very Long Baseline Interferometry (VLBI) catalogues and the Sloan Digital Sky Survey (SDSS) Data Release 4 (D...

We present the results of simultaneous X-ray and radio observations of the peculiar Z-type neutron star X-ray binary Cir X-1, observed with the Rossi X-ray timing explorer satellite and the Australia Telescope Compact Array in 2000 October and 2002 December. We identify typical Z source behaviour in the power density spectra as well as characteristic Z patterns drawn in an X-ray hardness-intens...

Our VLA observations of the XMM-Newton/Chandra 13hr deep survey field (see Page et al., this proceedings) result in one of the two deepest 1.4GHz radio maps ever made. Within the 15′ radius field covered by the deep X-ray data (0.19 deg), a total of 556 radio sources are detected, down to a 4σ flux limit of 28μJy. Of the 214 Chandra sources, 55 have radio counterparts. The sub-arcsecond accurac...

We report Australia Telescope Compact Array (ATCA) radio-continuum and ROSAT PSPC X-ray observations of the region surrounding the peculiar galaxy pair ESO 295-IG022, lying at the centre of the poor cluster Abell S0102. We identify a radio galaxy coincident with the galaxy pair, with bipolar, bent radio jets appearing centred on the southern galaxy, and extending both to the south, for about 95...

We summarise all the reported detections of, and upper limits to, the radio emission from persistent (i.e. non-transient) X-ray binaries. A striking result is a common mean observed radio luminosity from the black hole candidates (BHCs) in the Low/Hard X-ray state and the neutron-star Z sources on the horizontal X-ray branch. This implies a common mean intrinsic radio luminosity to within a fac...

We present multiwavelength observations of Cygnus X-3 during an extended outburst in 1994 February-March. Intensive radio monitoring at 13.3, 3.6 & 2.0 cm is complemented by observations at (sub)millimetre and infrared wavelengths, which find Cyg X-3 to be unusually bright and variable, and include the first reported detection of the source at 0.45 mm. We report the first confirmation of quench...

We demonstrate electromagnetic induction imaging with an unshielded, portable radio frequency atomic magnetometer scanning over the target object. This configuration satisfies standard requirements in typical applications, from security screening to medical imaging. The ability scan object relies on miniaturization of sensor head, active compensation ambient magnetic field, and implementation a...

We present new radio observations of 9 members of a sample of 29 nearby (z < 0.2) BL Lac objects. The new data have been obtained with the European VLBI Network and/or the MERLIN at 1.6 and 5 GHz and complement previous observations. For one object, the TeV source Mrk 421, we also present deep multi-epoch VLBA and Global VLBI data, which reveal a resolved diffuse jet, with clear signatures of l...

We present radio observations at three frequencies and contemporaneous optical monitoring of the peculiar BLLac object AO0235+164. During a three-week campaign with the VLA we observed intraday variability in this source and found a distinct peak which can be identified throughout the radio frequencies and tentatively connected to the R-band variations. This event is characterized by unusual pr...