The ExoGRAVITY project: using single mode interferometry to characterize exoplanets

TL;DR

The ExoGRAVITY project employs single mode interferometry combined with adaptive optics to precisely characterize known young giant exoplanets, providing high-quality spectra, accurate orbital data, and insights into their composition and formation.

Contribution

This study introduces a novel survey using interferometry to obtain unprecedented astrometric and spectral data of exoplanets, enabling detailed analysis of their physical and chemical properties.

Findings

High-precision astrometric data for exoplanets

First C/O ratio survey of exoplanets

Catalogue of high-quality K-band spectra

Abstract

Combining adaptive optics and interferometric observations results in a considerable contrast gain compared to single-telescope, extreme AO systems. Taking advantage of this, the ExoGRAVITY project is a survey of known young giant exoplanets located in the range of 0.1'' to 2'' from their stars. The observations provide astrometric data of unprecedented accuracy, being crucial for refining the orbital parameters of planets and illuminating their dynamical histories. Furthermore, GRAVITY will measure non-Keplerian perturbations due to planet-planet interactions in multi-planet systems and measure dynamical masses. Over time, repetitive observations of the exoplanets at medium resolution ($R=500$) will provide a catalogue of K-band spectra of unprecedented quality, for a number of exoplanets. The K-band has the unique properties that it contains many molecular signatures (CO, H$_2$O, CH$_4$, CO$_2$). This allows constraining precisely surface gravity, metallicity, and temperature, if used in conjunction with self-consistent models like Exo-REM. Further, we will use the parameter-retrieval algorithm petitRADTRANS to constrain the C/O ratio of the planets. Ultimately, we plan to produce the first C/O survey of exoplanets, kick-starting the difficult process of linking planetary formation with measured atomic abundances.