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 $10-100\mu$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 $R_0$ to the Galactic Center reported previously.

References in corpus (14)

• Trigonometric Parallaxes Of High-Mass Star Forming Regions: Our View Of The Milky Way
• Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole
• An Update on Monitoring Stellar Orbits in the Galactic Center
• An Improved Distance and Mass Estimate for Sgr A* from a Multistar Orbit Analysis
• Radio interferometric gain calibration as a complex optimization problem
• The old nuclear star cluster in the Milky Way: dynamics, mass, statistical parallax, and black hole mass
• Correcting direction-dependent gains in the deconvolution of radio interferometric images
• Twelve years of spectroscopic monitoring in the Galactic Center: the closest look at S-stars near the black hole
• Revisiting the radio interferometer measurement equation. II. Calibration and direction-dependent effects
• On the nature of the fast moving star S2 in the Galactic Center
• Reaching micro-arcsecond astrometry with long baseline optical interferometry; application to the GRAVITY instrument
• The fiber coupler and beam stabilization system of the GRAVITY interferometer
• Single-mode interferometric field of view in partial turbulence correction. Application to the observation of the environment of Sgr A* with GRAVITY
• GRAVITY: the Calibration Unit

Cited by in corpus (10)

• The mass distribution in the Galactic Centre from interferometric astrometry of multiple stellar orbits
• Strong-field Gravity Tests with the Double Pulsar
• The mass of Beta Pictoris c from Beta Pictoris b orbital motion
• The Return of the Templates: Revisiting the Galactic Center Excess with Multi-Messenger Observations
• Constraining particle acceleration in Sgr A* with simultaneous GRAVITY, Spitzer, NuSTAR and Chandra observations
• PSR J2222--0137. I. Improved physical parameters for the system
• Deep Images of the Galactic Center with GRAVITY
• GRAVITY K-band spectroscopy of HD 206893 B: brown dwarf or exoplanet
• The Milky Way, Coming into Focus: Precision Astrometry Probes its Evolution, and its Dark Matter
• Predicted Trends in Milky Way Bulge Proper Motion Rotation Curves: future Prospects for HST and LSST