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 ~$5^{\deg}$ accuracy beyond the first null of visibility. For a 0.05 mas exoplanet, accuracies of ~$0.1%$ and ~$1^{\deg}$ 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.
Highlights
The discovery of the first exoplanet around a solar-type star by Mayor & Queloz (1995) has opened up a new field of research in both planetary and stellar sciences
Studies have been performed to quantify their impact on infrared interferometry, but no such studies have been performed in the visible domain
We have moved from the era of exoplanet discovery to the era of exoplanet characterization, which is closely related to the characterization of host stars
Summary
The discovery of the first exoplanet around a solar-type star by Mayor & Queloz (1995) has opened up a new field of research in both planetary and stellar sciences. One of the difficulties encountered in achieving an exoplanet characterization is to measure complex visibilities at advantageous spatial frequencies This problem has been discussed by Chelli et al (2009) when they presented the phase-closure nulling method. Since a stellar photosphere is not perfectly symmetrical and we do not necessarily know the position of the transiting exoplanet at the time of the measurement, the information can only be extracted by simultaneously investigating many data This implies measuring many visibilities and phases and using a (u,v) plane that covers many directions. 2, we describe a new numerical code called COMETS that allows modeling interferometric observables of a star hosting a magnetic spot and/or a transiting exoplanet We apply this code to analyze the impacts that exoplanet and spot parameters produce on the shortest baselines length required to measure their signal in Sect.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
