Observations of Twelve Radio Sources at A Wavelength of 0.73 m with A Tracking Interferometer Having A Baseline of 180,000 Wavelengths

Abstract

Angular structure measurements on twelve radio sources have been made at 0.73 m with a long baseline tracking interferometer. Each source was observed continuously while the effective baseline varied in the range 60,000 to 180,000 wavelengths. The normalization of the results is discussed and a new calibration procedure applied. An attempt has been made to fit simple source models to the observations. The fringe visibilities of three sources are close to unity at all hour angles and as a result it is only possible to give upper limits to their dimensions. The other nine sources are partially resolved at some or all hour angles and for four of them the position angles and angular sizes of the major axes are given. Four sources are found to consist of two components. For two of these double sources the component separation and position angle are determined with an order of magnitude greater accuracy than has previously been achieved. The remaining source gives striking evidence of variations in source structure with wavelength.