Research Division Seminar
Commission G5 Stellar and Planetary Atmospheres, IAU: A Gaia view of magnetic activity and rotation of low-mass stars
Gaia all-sky scanning and multi-epoch photometric and spectroscopic observations offer unprecedented opportunities to detect and characterise magnetic activity and rotation of low-mass stars. In the second Gaia data release, rotation period and rotational modulation amplitude for ≈150,000 low-mass stars were provided from the analysis of the first 22-month of data collection. The third Gaia data release, based on the analysis of the first 34 months of data collection, contains rotational modulation data for ≈500,00 low-mass stars and an activity index for ≈2 million low-mass stars, this latter derived from the analysis of the CaII infrared triplet (IRT) observed by the RVS instrument. These constitute the largest catalogues of magnetic activity and rotational period to date. Such a large number of all-sky measurements represents a gold mine for studies related to stellar rotation, magnetic activity, and mass accretion. The analysis of the period-amplitude diagram of the rotational modulation has already provided evidence of distinct magneto-rotational regimes in the early phase of stellar evolution and of rapid transitions between them. Such evidence challenges a dependence on rotation only and suggests an important role of the rotational history in the early phase of the magneto-rotational evolution. The activity index derived from the CaII IRT clearly show three regimes, confirming suggestions made by previous authors on much smaller datasets. For the first time, a dramatic change in the activity distribution is found for Teff < 3500 K, with a dominance of low activity stars close to the transition between partially- and fully-convective stars and a rise in activity down into the fully-convective regime.