Improved GRAVITY astrometric accuracy from modeling of optical aberrations
Abstract
The GRAVITY instrument on the ESO VLTI pioneers the field of high-precision near-infrared interferometry by providing astrometry at the as level. Measurements at such high precision crucially depend on the control of systematic effects. Here, 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 impact of such 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 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 of less 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 to the Galactic Center reported previously.
Cite
@article{arxiv.2101.12098,
title = {Improved GRAVITY astrometric accuracy from modeling of optical aberrations},
author = {GRAVITY Collaboration and R. Abuter and A. Amorim and M. Bauböck and J. P. Berger and H. Bonnet and W. Brandner and Y. Clénet and R. Davies and P. T. de Zeeuw and J. Dexter and Y. Dallilar and A. Drescher and A. Eckart and F. Eisenhauer and N. M. Förster Schreiber and P. Garcia and F. Gao and E. Gendron and R. Genzel and S. Gillessen and M. Habibi and X. Haubois and G. Heißel and T. Henning and S. Hippler and M. Horrobin and A. Jiménez-Rosales and L. Jochum and L. Jocou and A. Kaufer and P. Kervella and S. Lacour and V. Lapeyrère and J. -B. Le Bouquin and P. Léna and D. Lutz and M. Nowak and T. Ott and T. Paumard and K. Perraut and G. Perrin and O. Pfuhl and S. Rabien and G. Rodríguez-Coira and J. Shangguan and T. Shimizu and S. Scheithauer and J. Stadler and O. Straub and C. Straubmeier and E. Sturm and L. J. Tacconi and F. Vincent and S. von Fellenberg and I. Waisberg and F. Widmann and E. Wieprecht and E. Wiezorrek and J. Woillez and S. Yazici and A. Young and G. Zinsınst{9}},
journal= {arXiv preprint arXiv:2101.12098},
year = {2021}
}