[Impact de la variabilité stellaire sur la détectabilité et la caractérisation des exoplanètes]
La variabilité stellaire est devenue un problème majeur pour détecter les planètes de faible masse en utilisant la méthode des vitesses radiales. Je présente les approches suivies pour caractériser l’amplitude et les propriétés de la variabilité stellaire en vitesse radiale. Plus précisément, l’approche consistant à utiliser notre connaissance du Soleil pour mieux comprendre les différents processus qui se produisent à différentes échelles s’est avérée très utile. Cela a été fait de différentes manières, sur la base d’observations et de modèles. Ceci est crucial car il est alors possible de comparer les vitesses radiales intégrées au disque avec les structures réelles de la surface solaire, telles que les taches et les plages, et avec les flux photosphériques à différentes échelles spatiales. De nombreux processus physiques affectent en effet les mesures de vitesse radiale : ils sont principalement dus aux caractéristiques magnétiques (taches et plages), aux écoulements (oscillations, granulation, supergranulation, circulation méridienne), et aux interactions entre les champs magnétiques et les écoulements (inhibition du blueshift convectif dans les plages). Je présente plus en détail une sélection d’études visant à caractériser l’impact de la variabilité stellaire, en particulier la relation entre les indicateurs d’activité et les vitesses radiales, puis je me concentre sur la caractérisation des masses et les performances de détection. Enfin, je passe brièvement en revue l’impact de la variabilité stellaire sur les transits photométriques et l’astrométrie, qui sont également affectés, mais dans une moindre mesure.
Stellar variability has become a major issue to detect low mass planets using the radial velocity technique. I present the approaches followed to characterise the amplitude and the properties of stellar variability in radial velocity. More specifically, the approach consisting in using our knowledge of the Sun to understand better the different processes which are occuring at different scales proved to be very useful. This has been done in different ways, based on observations and models. This is crucial because it is then possible to compare disk-integrated radial velocities with actual structures on the solar surface, such as spots and plages, and with photospheric flows at different spatial scales. Many physical processes indeed affect the radial velocity measurements: they are mostly due to magnetic features (spots and plages), flows (oscillations, granulation, supergranulation, meridional flows), and to the interactions between magnetic fields and flows (inhibition of the convective blueshift in plages). I present in more detail a selection of studies aiming at characterising the impact of stellar variability, in particular the relationship between activity indicators and radial velocities, and then focusing on mass characterisation and detection performance. Finally, I briefly review the impact of stellar variability on photometric transits and astrometry, which are also affected, but to a lesser extent.
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Mot clés : Exoplanètes, Variabilité stellaire, Vitesses radiales, Transits photométriques, Astrométrie
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@article{CRPHYS_2023__24_S2_A4_0,
author = {Nad\`ege Meunier},
title = {Impact of stellar variability on exoplanet detectability and characterisation},
journal = {Comptes Rendus. Physique},
publisher = {Acad\'emie des sciences, Paris},
year = {2023},
doi = {10.5802/crphys.140},
language = {en},
note = {Online first},
}
Nadège Meunier. Impact of stellar variability on exoplanet detectability and characterisation. Comptes Rendus. Physique, Online first (2023), pp. 1-15. doi : 10.5802/crphys.140.
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