Abstract

Contributed Talk - Splinter ExoPlanets

Faint companions mimicking interferometric hot exozodiacal dust observations

K. Tsishchankava-1, F. Kirchschlager-2, A. Krieger-1, T. A. Stuber-3, S. Wolf-1
1 -Institut für Theoretische Physik und Astrophysik, Kiel University, Germany, 2-Sterrenkundig Observatorium, Ghent University, Belgium, 3-Department of Astronomy and Steward Observatory, The University of Arizona, USA

Interferometric observations of various nearby main-sequence stars reveal an unexpected infrared excess, raising questions about its origin. The two leading explanations point to either hot exozodiacal dust or faint companions, as both produce similar infrared interferometric signatures. To explore this, a system was modeled consisting of a limb-darkened star and a faint, close-in companion. Visibility and closure phases were calculated for three VLTI instruments (PIONIER, GRAVITY, and MATISSE) across four telescope configurations (small, medium, large, and extended). The interferometric signatures of faint companions in the presence of a limb-darkened star were analyzed, with particular focus on their detectability through visibility and closure phase measurements. A strict upper limit was established for the companion-induced visibility deficit and closure phase. Additionally, significant non-detection probabilities were identified for closure phase observations of faint companions, despite detectable visibility deficits. These findings challenge previously used companion rejection criteria—such as near-zero closure phases and flux estimates based on Gaussian-distributed dust densities, demonstrating that they are not universally reliable. This underscores the need to reevaluate companion rejections in earlier studies on the hot exozodiacal dust phenomenon.