Abstract

Contributed Talk - Splinter ExoPlanets

Hot exozodiacal dust (HEZD): Exoplanet polarimetry and Fomalhaut MATISSE observations

Kevin Ollmann, Sebastian Wolf, Moritz Lietzow, Thomas Stuber, Florian Kirchschlager, Katsiaryna Tsishchankava, Alexis Matter, Steve Ertel, Tim Pearce, Alexander Krivov
Christian-Albrechts-Universität zu Kiel, The University of Arizona, Ghent University, Université Côte d’Azur, University of Warwick, Friedrich-Schiller-Universität Jena

Interferometric near- and mid-infrared observations have revealed that approximately one-fifth of nearby stars are potentially surrounded by hot exozodiacal dust (HEZD) of yet unknown origin. Since HEZD is located at orbital radii comparable to those of close-in exoplanets, its presence potentially influences the polarimetric characterization of such planets and vice versa. We analyze the impact of HEZD around main-sequence stars on the polarimetric characterization of close-in exoplanets and vice versa by identifying characteristic polarimetric signatures of both components for selected model parameters. We find that the presence of HEZD needs to be considered in any effort to characterize close-in exoplanets via polarimetric observations. Most importantly, tighter constraints on properties of the HEZD, particularly its size distribution, are required. Reference: Ollmann et al. (2023) In an observational study of the HEZD phenomenon we investigated the nearby A3 V star Fomalhaut, performing the first interferometric observations with the MATISSE instrument at the VLTI in the photometric bands L and M for this system. We find that the MATISSE L band data provide a marginal detection of circumstellar radiation, potentially caused by the presence of HEZD, which is only the second detection of HEZD emission in the L band. An analysis of the data with different approaches shows that the best-fit values for the HEZD parameters are consistent with those of previous Fomalhaut observations but result in different dust-to-star flux ratios. Reference: Ollmann et al. (2025, accepted)