A list of bright interferometric calibrators measured at the European Southern Observatory Very Large Telescope Interferometer

Abstract

In a previous publication (Richichi & Percheron 2005) we described a program of observations of candidate calibrator stars at the ESO Very Large Telescope Interferometer (VLTI), and presented the main results from a statistical point of view. In the present paper, we concentrate on establishing a new homogeneous group of bright interferometric calibrators, based entirely on publicly available K-band VLTI observations carried out with the VINCI instrument up to July 2004. For this, we have defined a number of selection criteria for the quality and volume of the observations, and we have accordingly selected a list of 17 primary and 47 secondary calibrators. We have developed an approach to a robust global fit for the angular diameters using the whole volume of quality-controlled data, largely independent of a priori assumptions. Our results have been compared with direct measurements, and indirect estimates based on spectrophotometric methods, and general agreement is found within the combined uncertainties. The stars in our list cover the range K=-2.9 to +3.0 mag in brightness, and 1.3 to 20.5 milliarcseconds in uniform-disk diameter. The relative accuracy of the angular diameter values is on average 0.4% and 2% for the primary and secondary calibrators respectively. Our calibrators are well suited for interferometric observations in the near-infrared on baselines between ~20m and ~200m, and their accuracy is superior, at least for the primary calibrators, to other similar catalogues. Therefore, the present list of calibrators has the potential to lead to significantly improved interferometric scientific results.