Transiting exoplanets and magnetic spots characterized with optical interferometry

Abstract

Stellar activity causes difficulties in the characterization of transiting exoplanets. Studies have been performed to quantify its impact on infrared interferometry, but not in the visible domain, which however allows reaching better angular resolution and is also the one mostly used for spectroscopic and photometric measurements. We use a standard case to completely analyse the impact of an exoplanet and a spot on interferometric observables and relate it to current instrument capabilities, taking into account realistic achievable precisions. We built a numerical code called COMETS using analytical formulae to perform a simple comparison of exoplanet and spot signals. We explore instrumental specificities needed to detect them, like the baseline length required, the accuracy and S/N. We also discuss the impact of exoplanet and spot parameters on squared visibility and phase. We find that the main improvement to bring is the sensitivity of instruments. The accuracy on squared visibilities has to be improved by a factor 10 to detect an exoplanet of 0.1 mas, leading to $<0.5$ precision, along with phase measurements of ~$5^{°}$ accuracy beyond the first null of visibility. For a 0.05 mas exoplanet, accuracies of ~$0.1$ and ~$1^{°}$ from the first null are required on squared visibilities and phases, respectively. Magnetic spots can mimic these signals, leading to false exoplanet characterization. Phases measurements from the 3rd lobe is needed to distinguish between a spot and an exoplanet if they have the same radius. Increasing interferometer sensitivity, more objects will become common between interferometric targets and photometric ones. Furthermore, new missions like PLATO, CHEOPS or TESS will provide bright exoplanet host stars. Measurements will thus overlap and provide a better characterization of stellar activity and exoplanet.

Version 2 after language editing and a few typos corrected. 12 pages, 7 figures

References in corpus (25)

• Validation of the new Hipparcos reduction
• Improved parameters for extrasolar transiting planets
• PIONIER: a 4-telescope visitor instrument at VLTI
• The Stagger-grid: A Grid of 3D Stellar Atmosphere Models - I. Methods and General Properties
• CHEOPS: A Transit Photometry Mission for ESA's Small Mission Programme
• Starspots and spin-orbit alignment in the WASP-4 exoplanetary system
• Kepler-21b: A 1.6REarth Planet Transiting the Bright Oscillating F Subgiant Star HD 179070
• Using Star Spots to Measure the Spin-orbit Alignment of Transiting Planets
• CHARA Array Measurements of the Angular Diameters of Exoplanet Host Stars
• Time evolution and rotation of starspots on CoRoT-2 from the modelling of transit photometry
• Searching for faint companions with VLTI/PIONIER. I. Method and first results
• Toward Direct Detection of Hot Jupiters with Precision Closure Phase: Calibration Studies and First Results from the CHARA Array
• The limb-darkened Arcturus; Imaging with the IOTA/IONIC interferometer
• A new interferometric study of four exoplanet host stars : θ Cygni, 14 Andromedae, {\upsilon} Andromedae and 42 Draconis
• Three-dimensional interferometric, spectrometric, and planetary views of Procyon
• Direct Measurement of the Radius and Density of the Transiting Exoplanet HD 189733B with the CHARA Array
• Validation of the Exoplanet Kepler-21b using PAVO/CHARA Long-Baseline Interferometry
• NPOI Measurements of Ten Stellar Oscillators
• Closure Phase Signatures of Planet Transit Events
• Phase closure nulling of HD 59717 with AMBER/VLTI . Detection of the close faint companion
• Planet transit and stellar granulation detection with interferometry
• Deep near-infrared interferometric search for low-mass companions around beta Pictoris
• Phase closure nulling. Application to the spectroscopy of faint companions
• The operation of VEGA/CHARA : from the scientific idea to the final products
• The 2012 Interferometric Imaging Beauty Contest

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• Spatially resolved spectroscopy across stellar surfaces. V. Observational prospects: Toward Earth-like exoplanet detection
• Asymmetries on red giant branch surfaces from CHARA/MIRC optical interferometry
• Science cases for a visible interferometer
• Minimal Data Fidelity for Detection of Stellar Features or Companions