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Investigating stellar activity through eight years of Sun-as-a-star observations by Klein, Baptiste; Aigrain, Suzanne; Cretignier, Michael; Moulla, Khaled Al; Dumusque, Xavier; Barragán, Oscar; Yu, Haochuan; Mortier, Annelies; Rescigno, Federica; Cameron, Andrew Collier; López-Morales, Mercedes; Meunier, Nadège; Sozzetti, Alessandro; O'Sullivan, Niamh K. is a scholarly article available to read on EtoBox.

What is Investigating stellar activity through eight years of Sun-as-a-star observations about?

Stellar magnetic activity induces both distortions and Doppler-shifts in the absorption line profiles of Sun-like stars. Those effects produce apparent radial velocity (RV) signals which greatly hamper the search for potentially habitable, Earth-like planets. In this work, we investigate these distortions in the Sun using cross-correlation functions (CCFs), derived from intensive monitoring with the high-precision spectrograph HARPS-N. We show that the RV signal arising from line-shape variations on time-scales associated with the solar rotation and activity cycle can be robustly extracted from the data, reducing the RV dispersion by half. Once these have been corrected, activity-induced Doppler-shifts remain, that are modulated at the solar rotation period, and that are most effectively modelled in the time domain, using Gaussian Processes (GPs). Planet signatures are still best retrieved with multi-dimensonal GPs, when activity is jointly modelled from the raw RVs and indicators of the line width or of the Ca II H and K emission. After GP modelling, the residual RVs exhibit a dispersion of 0.6-0.8 m/s, likely to be dominated by signals induced by super-granulation. Finally, we fi

Author

Klein, Baptiste; Aigrain, Suzanne; Cretignier, Michael; Moulla, Khaled Al; Dumusque, Xavier; Barragán, Oscar; Yu, Haochuan; Mortier, Annelies; Rescigno, Federica; Cameron, Andrew Collier; López-Morales, Mercedes; Meunier, Nadège; Sozzetti, Alessandro; O'Sullivan, Niamh K.

Published

2024

Language

EN