Improved GRAVITY astrometric accuracy from modeling 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 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.

The Milky Way, Coming into Focus: Precision Astrometry Probes its Evolution, and its Dark Matter

“…This information, in concert with Gaia DR2 data, as well as with other optical and infrared surveys, has refined the rotation curve over the distance range 5 < R < 25 kpc, yields V c = 229.0 ± 0.2 km s −1 , with a systematic uncertainty of 3% [199], at the distance of the Sun to the Galactic Center of R 0 = 8.122 ± 0.0.031 kpc [201]. Recent improvement in the treatment of optical aberrations have improved the agreement between their earlier results [201,202] to yield R 0 = 8.275 ± 0.034 kpc [203], where we have combined statistical and systematic errors in quadrature throughout. For reference, various other recent measurements and fits at R 0 give [97], and V c = 243 ± 8 km s −1 [200].…”

First Direct Detection Constraints on Planck-Scale Mass Dark Matter with Multiple-Scatter Signatures Using the DEAP-3600 Detector

“…DM is simulated via Monte Carlo with the RAT software [36], built upon Geant4 [37], in two steps: 1) it is attenuated in the overburden, 2) it is propagated in the detector, simulating optical and data acquisition (DAQ) responses. DM is generated 80 km above the Earth's surface with the Standard Halo Model velocity distribution [38][39][40][41][42][43][44] and propagated through the Earth to a 1.5 m shell surrounding the AV. DM is boosted into the detector's reference frame for a randomized date, following Refs.…”

Gravitational lensing by a quantum deformed Schwarzschild black hole

“…Its deviation from the one of the Schwarzschild black hole δ P ranges from −3.4 to 0 µas, below the astrometric accuracy of GRAVITY. However, with further improvement [130], the upgraded GRAVITY+ might have sufficient ability to detect the small changes of δ P tot and δ P in the near future. The normalized fluxes difference between the lensed images F/F src is very close to 1 for a large β and decrease to about 0.993 for a small β.…”