Volume 647, March 2021
|Number of page(s)||17|
|Published online||09 March 2021|
Improved GRAVITY astrometric accuracy from modeling optical aberrations⋆
Max Planck Institute for Extraterrestrial Physics, Giessenbachstraße 1, 85748 Garching, Germany
2 LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, 92195 Meudon, France
3 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
4 1st Institute of Physics, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany
5 Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
6 Universidade de Lisboa – Faculdade de Ciências, Campo Grande, 1749-016 Lisboa, Portugal
7 Faculdade de Engenharia, Universidade do Porto, rua Dr. Roberto Frias, 4200-465 Porto, Portugal
8 European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany
9 European Southern Observatory, Casilla 19001, Santiago 19, Chile
10 Sterrewacht Leiden, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands
11 Departments of Physics and Astronomy, Le Conte Hall, University of California, Berkeley, CA 94720, USA
12 CENTRA – Centro de Astrofísica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal
13 Department of Astrophysical & Planetary Sciences, JILA, Duane Physics Bldg., 2000 Colorado Ave, University of Colorado, Boulder, CO 80309, USA
14 Department of Particle Physics & Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel
15 Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
16 Department of Physics, Technical University Munich, James-Franck-Straße 1, 85748 Garching, Germany
17 Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, 53121 Bonn, Germany
Accepted: 27 January 2021
The GRAVITY instrument on the ESO VLTI pioneers the field of high-precision near-infrared interferometry by providing astrometry at the 10−100 μas level. Measurements at this high precision crucially depend on the control of systematic effects. We investigate how aberrations introduced by small optical imperfections along the path from the telescope to the detector affect the astrometry. We develop an analytical model that describes the effect of these aberrations on the measurement of complex visibilities. Our formalism accounts for pupil-plane and focal-plane aberrations, as well as for the interplay between static and turbulent aberrations, and it successfully reproduces calibration measurements of a binary star. The Galactic Center observations with GRAVITY in 2017 and 2018, when both Sgr A* and the star S2 were targeted in a single fiber pointing, are affected by these aberrations at a level lower than 0.5 mas. Removal of these effects brings the measurement in harmony with the dual-beam observations of 2019 and 2020, which are not affected by these aberrations. This also resolves the small systematic discrepancies between the derived distance R0 to the Galactic Center that were reported previously.
Key words: Galaxy: center / Galaxy: fundamental parameters / instrumentation: interferometers / instrumentation: high angular resolution / methods: data analysis
GRAVITY is developed in a collaboration by the Max Planck Institute for extraterrestrial Physics, LESIA of Observatoire de Paris/Université PSL/CNRS/Sorbonne Université/Université de Paris and IPAG of Université Grenoble Alpes/CNRS, the Max Planck Institute for Astronomy, the University of Cologne, the CENTRA – Centro de Astrofisica e Gravitação, and the European Southern Observatory.
© GRAVITY Collaboration 2021
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Open Access funding provided by Max Planck Society.
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