Hide and Seek with Spots and Planets

Improvements in the precision of available instruments have led to advancements in exoplanet detection and characterization over the past two decades. However, this progress has also resulted in the increased contaminating impact of stellar activity. Among the various stellar activity processes, magnetically active regions, and starspots in particular, stand out as they can be effectively studied through grid-based simulations thanks to their localized nature. Taking advantage of this concept, we enhance the ANTARESS framework by incorporating spots in its implementation of the Rossiter-McLaughlin Revolutions technique, a novel method for analyzing Rossiter-McLaughlin signatures. This technique, which follows a simulation-based approach to modeling observations, can be used to generate 'mock' data. Leveraging this capability, we generate simulated datasets deliberately contaminated by spots. By fitting these data, we can control the inputs and thereby assess the quality of our retrievals, study the degeneracies associated with each parameter, and devise strategies to mitigate them. Additionally, we apply the ANTARESS framework to highly contaminated transit spectroscopy observations of AU Mic b. Although we were unable to perform a full retrieval of the system's bulk properties, our analysis revealed that a two-spot model is necessary to replicate these observations.