Detecting Secular Perturbations in Kepler Planetary Systems Using Simultaneous Impact Parameter Variation Analysis (SIPVA)

Abstract

Secular impact-parameter variations encode dynamical perturbations and can help reveal unseen companions or constrain planetary masses when combined with dynamical interpretation. Existing methods either fit transits independently or jointly model the light curves and orbital dynamics. We introduce Simultaneous Impact Parameter Variation Analysis (SIPVA), which avoids the N-body integrations used in many dynamical or photodynamical fitting approaches. SIPVA directly incorporates a linear time-dependent model for impact parameters into the Markov Chain Monte Carlo (MCMC) framework by fitting all transits simultaneously. We evaluate SIPVA and the transit-by-transit implementation on artificial systems, grouped by the fixed-model injection strength label L = sqrt(LLR_theory). In these controlled injections, SIPVA outperforms the particular transit-by-transit implementation examined here in both detection and recovery performance. Applied to 16 Kepler planets previously identified as exhibiting significant transit-duration variations, SIPVA detects impact-parameter trends in 9 planets, compared with 5 using independent transit fits.SIPVA provides a joint light-curve framework for measuring secular impact-parameter trends without specifying a dynamical architecture or performing N-body integrations.

16 pages, 5 figures