May 15 – 17, 2026
College of Hakka Studies at NYCU, Zhubei, Hsinchu County 國立陽明交通大學客家學院(竹北六家校區)
Asia/Taipei timezone

Evidence for a Non-Transiting Companion in the TOI-2109 System via Transit Timing Variation

May 16, 2026, 5:30 PM
15m
HK105

HK105

Speaker

Kaviya Parthasarathy (National Tsing Hua University)

Description

Transit Timing Variation (TTV) is a robust method for detecting
non-transiting planets in multi-planetary systems, especially those near
Mean Motion Resonance (MMR). In this study, we focus on TOI-2109 b, one
of the few known exoplanets with an orbital period shorter than 1 day.
To achieve the precision necessary to detect these minute gravitational
perturbations, we integrated high-cadence space-based photometry from
TESS and CHEOPS with long-baseline ground-based observations. Our
dataset comprises nearly 100 transit epochs, providing a comprehensive
baseline for TTV modelling.

With these data, we performed a model comparison across four scenarios:
a constant linear ephemeris, orbital decay, apsidal precession due to
gravitational interactions and general relativistic effects, and
sinusoidal models to identify periodic oscillations. To account for
potential multi-planetary interactions, we also employed a two-planet
dynamical model obtained from N-body simulations. While such planets are
highly susceptible to orbital decay via tidal dissipation, our analysis
reveals evidence of a potential additional planet within the system. Our
results suggest the presence of an additional planetary companion near a
MMR. This study highlights the importance of combining multiple
modelling approaches and long-term dynamical simulations to uncover
hidden planetary companions and a better understanding of the complex
gravitational interactions in ultra-short-period exoplanetary systems.

Participate the oral/poster presentation award competition Yes

Author

Kaviya Parthasarathy (National Tsing Hua University)

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