The last decade, the CoRoT and Kepler/K2 missions have showed the power of asteroseismology in order to determine the fundamental stellar parameters with a better precision than the classical methods. In 2018, NASA successfully launched the TESS (Transiting Exoplanet Survey Satellite) mission that will continue the search of exoplanets and allow us to do asteroseismic analyses. We propose to analyze the data collected by TESS in order to charactacterize solar-type stars, subgiants and red giants, and in particular planet-host stars and solar-analogs. During the first year of the TESS mission, we have already detected solar-like oscillations in a handful of main-sequence and subgiants and many red giants in particularly for stars observed in several sectors. On the one hand, we already have tools to determine the global seismic parameters to extract the frequencies of the individual modes, and to model the stars. However, these techniques need to be improved and optimized for the special characteristics of the TESS observations and their calibration will require the development of additional procedures that do not exist yet. Furthermore, the vast number of incoming data expected over the lifetime of TESS require advanced processing techniques. The rapid progress on the field of machine learning makes this a very promising tool to allow the detection of the oscillations and extract seismic observables. Therefore, this will be one of the main tasks for one of the postdocs we would like to hire for this project.

Most of the TESS targets are observed in 27 days segments allowing to study the rotation and surface magnetism of the fast rotators in the sample (up to 8-10 days rotation period). Depending on the position of the stars in the sky, hundreds to thousands of stars are continuously observed for more than 3 months, which will be the case for the regions closer to the ecliptic poles, allowing to extract rotation period and magnetism up to one-month rotation periods, i.e., like the Sun, opening the study of stellar ages through gyrochronology and obtain possible answer the open question if the Sun is going through changes in terms of its magnetic properties.

Finally, we plan to observe some of the TESS targets with the SONG network, which will allow us to have observations in photometry and spectroscopy to obtain contemporaneous radial velocity time series of some targets, allowing us to better understand the characteristics of the variability of those stars. The most interesting targets (once performed the simultaneous photometry-velocity comparison) spectroscopic observations with SONG can be continued for as far (month, years) as required for better characterization of the oscillation spectrum and therefore a much precise modeling of the target (Age).

The IAC has already extracted more than 17 millions of lightcurves from the Full-Frame Images for the Northern Hemisphere. More lightcurves should be provided during the next 3 years given the 2-year extension of the TESS mission. With this amount of data, we will have enough work for the next 3 years and this is the reason why we are requesting 3 years of funding.