Narrow-angle astrometry with PRIMA

TL;DR

This paper discusses the development and testing of the PRIMA facility at the VLT for narrow-angle astrometry aimed at detecting and characterizing extrasolar planets, including initial performance results and project status.

Contribution

It presents the first functional demonstration and performance characterization of PRIMA's astrometric mode for exoplanet detection.

Findings

Achieved initial astrometric precision with bright binary stars

Determined instrument accuracy and plate scale

Reported on progress towards scientific observations

Abstract

The Extrasolar Planet Search with PRIMA project (ESPRI) aims at characterising and detecting extrasolar planets by measuring the host star's reflex motion using the narrow-angle astrometry capability of the PRIMA facility at the Very Large Telescope Interferometer. A first functional demonstration of the astrometric mode was achieved in early 2011. This marked the start of the astrometric commissioning phase with the purpose of characterising the instrument's performance, which ultimately has to be sufficient for exoplanet detection. We show results obtained from the observation of bright visual binary stars, which serve as test objects to determine the instrument's astrometric precision, its accuracy, and the plate scale. Finally, we report on the current status of the ESPRI project, in view of starting its scientific programme.