Eclipse Timing of the Eccentric Planet HD 80606 b with JWST: Constraints on a Second Planet and Other Dynamical Effects

October 2026 • 2026AJ....172..225B

Authors • Beichman, Charles • Quarles, Billy • Fulton, B. J. • Lewis, Nikole • Challener, Ryan • de Wit, Julien • Rice, Malena • Inglis, Julie • Kataria, Tiffany

Abstract • A variety of effects can perturb the orbital properties of single planets in close orbits around their host stars. HD80606 b is a highly eccentric (ϵ = 0.93) exoplanet orbiting its host G5V star, HD 80606. HD 80606 b became a compelling target for exoplanet research after G. Laughlin et al. discovered that the 4.16 M_Jup planet transits and is eclipsed by HD 80606, thereby enabling photometric and spectroscopic observations to yield a wealth of information about the object. The exquisite precision of recent JWST eclipse timing offers an opportunity to investigate whether the orbit of HD 80606 b is modified due to a variety of mechanisms, including General Relativity, tidal torques, or the presence of a second perturbing planet. We have used over 25 yr of radial velocity data plus eclipse and transit observations to place limits on the precession of HD 80606 b's orbit and to assess which of these effects, if any, are observable. The new models are consistent with constant values of period, eccentricity and the argument of periastron, ω, with a limit on ω̇ at the level of the predicted general relativistic drift. The precision radial velocity and timing data limit the mass and location of a second planet external to HD 80606 b. Timing offsets between JWST eclipses relative to the K. A. Pearson et al. predictions are attributed to the poor constraints on ϵ(cosω,sinω) with only the single eclipse measurement available in that analysis and to an over-weighting of the eclipse timing in that earlier analysis.

Links

• ELECTR https://doi.org/10.3847/1538-3881/ae9a8c