Disentangling Secular Trends in Exoplanet Orbits

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• Simone Hagey (University of British Columbia)
• Wednesday 17 September 2025, 12:30-13:30
• Institute of Astronomy .

If you have a question about this talk, please contact Mika Kontiainen.

Gradual changes in exoplanet orbits, known as secular variations, can be detected through observations of transits, eclipses, and radial velocities that span multiple decades in time. Their detection and characterization enable the study of a wide range of dynamical phenomena, such as orbital decay and apsidal precession, which operate on timescales of millions of years. Under certain conditions, measurements of secular variations can even probe the interior structure of exoplanets, providing a unique tool for understanding exoplanet formation and evolution. A well-known example is the orbital decay of the hot Jupiter WASP -12 b, revealed through transit timing variations (TTVs), for which engulfment by the host star is the likely outcome.

While orbital decay provides a compelling explanation for WASP -12 b, attempts to interpret similar trends in other systems often conflict with current theories of tidal energy dissipation and orbital precession. The situation is further complicated by additional effects, including systemic proper motion, that can cause apparent secular trends that may mask or mimic real orbital evolution.

In this talk, I will present my work on secular trends in exoplanet orbits from both theoretical and observational perspectives. I will begin with an overview of detection techniques, followed by a case study of the hot Jupiter TrES-1 b that highlights the challenges of disentangling the origins of observed variations. I will conclude with an overview of an ongoing project that conducts the first population-level analysis of transit variations driven by systemic proper motion, based on a sample of more than 4,000 transiting exoplanets.

This talk is part of the IoA Dynamics Lunch series.

This talk is included in these lists:

• Institute of Astronomy
• IoA Dynamics Lunch

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