Measuring stellar surface rotation and activity with the PLATO mission

I. Strategy and application to simulated light curves

¹ INAF – Osservatorio Astrofisico di Catania, Via S. Sofia, 78, 95123 Catania, Italy
² Institute of Science and Technology Austria (IST Austria), Am Campus 1, Klosterneuburg, Austria
³ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
⁴ Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain
⁵ Departamento de Astrofísica, Universidad de La Laguna, La Laguna Tenerife Spain
⁶ Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, PT4150-762 Porto, Portugal
⁷ Department of Physics, University of Oxford, Oxford, UK
⁸ Université Paris-Sud, CNRS, Institut d’ Astrophysique Spatiale, UMR 8617, F-91405 Orsay Cedex, France
⁹ Rosseland Centre for Solar Physics, University of Oslo, P.O. Box 1029 Blindern, Oslo NO-0315, Norway
¹⁰ Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, Oslo NO-0315, Norway
¹¹ Université Paris Cité, Université Paris-Saclay, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
¹² LESIA, Observatoire de Paris, CNRS, Université PSL, Sorbonne Université, Université Paris Cité, 5 place Jules Janssen, 92195 Meudon, France

Received: 7 March 2024
Accepted: 27 June 2024

Abstract

The Planetary Transits and Oscillations of stars mission (PLATO) will allow us to measure surface rotation and monitor photometric activity of tens of thousands of main sequence solar-type and subgiant stars. This paper is the first of a series dedicated to the preparation of the analysis of stellar surface rotation and photospheric activity with the near-future PLATO data. We describe in this work the strategy that will be implemented in the PLATO pipeline to measure stellar surface rotation, photometric activity, and long-term modulations. The algorithms are applied on both noise-free and noisy simulations of solar-type stars, which include activity cycles, latitudinal differential rotation, and spot evolution. PLATO simulated systematics are included in the noisy light curves. We show that surface rotation periods can be recovered with confidence for most of the stars with only six months of observations and that the recovery rate of the analysis significantly improves as additional observations are collected. This means that the first PLATO data release will already provide a substantial set of measurements for this quantity, with a significant refinement on their quality as the instrument obtains longer light curves. Measuring the Schwabe-like magnetic activity cycle during the mission will require that the same field be observed over a significant timescale (more than four years). Nevertheless, PLATO will provide a vast and robust sample of solar-type stars with constraints on the activity-cycle length. Such a sample is lacking from previous missions dedicated to space photometry.