Abstract: Despite the substantial knowledge that has been acquired over the past years, there are still many open questions in the field of exoplanets, particularly for planetary systems orbiting around M dwarfs and massive stars, which are the targets of this project: What are the planetary architecture properties of stars of different masses and evolutionary stages? Are giant planets common around low mass M dwarfs? Can we detect planets around the most active M dwarfs? What is the greatest mass that a star can have to be able to form planets? Do those massive stars tend to form more massive planets? Does metallicity play a role in the formation of planets around such massive stars? Can we detect them?

In order to solve these questions a comprehensive analysis of stellar variability has to be carried out. The use of near-infrared (NIR) spectra will help identify genuine planetary radial velocity (RV) variations (that have similar amplitudes at all wavelengths) from the RV signals of stellar origin (that are wavelength-dependent). Furthermore, with the advent of new high resolution spectrographs in the NIR we now have a unique opportunity to better understand and characterise the RV signals induced by stellar activity or pulsations.

In this project we propose to take advantage of our privileged access to the Guaranteed Time Observations (GTO) data from NIRPS spectrograph to examine the stellar variability of two populations of interesting stars, M dwarfs and cool massive giants. These stars are excellent targets for NIR spectroscopy due to their 7/19higher emitted flux at longer wavelengths. Spectra and RV obtained in the NIR will be compared to their optical counterparts obtained simultaneously with HARPS and will help establish what are the best stellar activity indicators in the NIR and for which type of star. This, in turn, will allow us to differentiate the origin of the RV variations we observe in these stars. With the results of this project we will be in a much better position to corroborate the planetary signals we have found and to address some of the unanswered questions mentioned above.

Our team has a large experience in the search and characterization of planets and has developed different tools that will be used and improved for the purposes of the project. The goal of this exploratory project is thus to test novel techniques and explore the viability of different methods using spectra from stars observed by the NIRPS GTO survey. In particular, we are going to search for new activity indicators in the NIR and explore new ways to model stellar activity in these wavelengths to improve planet detection and characterisation of cool low-mass and massive evolved stars. The analysis carried out and the results from this project, in particular a tool to automatically calculate activity indices in the NIR, will be highly beneficial not only for NIRPS users, but also for other existing and
future NIR planet hunting surveys.