Beyond Planets: Simulating Exocomet Transits in High-Precision Photometry

The detection of exocomets provides a unique window into the small-body populations and dynamical evolution of extrasolar planetary systems. While spectroscopic signatures of exocomets have been identified in several debris-disk systems (e.g. Ferlet et al. 1987; Kiefer et al. 2014), photometric detections remain relatively rare and challenging due to their transient, asymmetric, and often aperiodic nature. However, previous studies have shown that exocomet transits can produce characteristic light-curve signatures that are, in principle, detectable in high-precision photometric data (Lecavelier des Etangs et al. 1999; Rappaport et al. 2018).

We explore simplified models of dusty exocomet transits, focusing on how different cometary structures may influence the observed shape of stellar light curves. The study relies on numerical simulations to examine the combined effects of absorption and scattering by circumstellar dust across a range of wavelengths. By considering various plausible dust properties and observing configurations, we aim to assess which photometric features could serve as reliable indicators of exocometary activity in transit observations (Kálmán et al. 2024).

The resulting synthetic light curves reproduce the characteristic asymmetric “shark-fin” transit profiles associated with exocomets, while revealing a strong wavelength dependence driven by dust properties. We show that multi-band photometry significantly enhances the ability to distinguish exocomet transits from other aperiodic dimming events, such as stellar activity or circumstellar disk structures. In particular, color-dependent transit depths and timing shifts provide constraints on grain size evolution and material composition within the cometary tail.

This work highlights the potential of exocomet transit simulations as a useful tool for interpreting photometric observations and for guiding future searches for exocomets. In particular, upcoming missions such as ARIEL, with its multi-wavelength observing capabilities, may offer new opportunities to identify and characterise dusty cometary transits in extrasolar systems (Tinetti et al. 2021).