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Description
The Low-Frequency Array (LOFAR) Long-Baseline Calibrator Survey (LBCS) was conducted between 2014 and 2019 in order to provide a set of calibrators for the LOFAR array. Here we present the complete survey, for which a preliminary analysis was published in 2016 using 20% of the survey data. The final catalogue consists of 30007 observations of 24713 sources in the northern sky, selected for a combination of bright low-frequency radio flux density and flat spectral index using existing surveys (WENSS, VLSS and MSSS). Approximately 1 calibrator per square degree is identified by the detection of compact flux, for declinations north of 30{deg} and a considerably lower density south of this point. The catalogue contains indicators of degree of correlated flux on baselines between the Dutch core and each of the international stations for all of the observations. Use of the VLBA calibrator list, together with statistical arguments by comparison with flux densities from lower-resolution catalogues, allow us to establish a rough flux density scale for the LBCS observations, so that LBCS statistics can be used to estimate compact fluxes, on scales between 300mas and 2-arcseconds, for sources observed in the survey.
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