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Algorithms for Stellar Perturbation Computations on Oort Cloud Comets
Authors:Hans Rickman  Marc Fouchard  Giovanni B Valsecchi  Christiane Froeschlé
Institution:1. Uppsala Astronomical Observatory, Box 515, SE-75120, Uppsala, Sweden
2. INAF–IASF, via Fosso del Cavaliere 100, IT-00133, Roma, Italy
3. IMCCE/SYRTE, Observatoire de Paris, 77 av. Denfert-Rochereau, 75014, Paris, France
4. Observatoire de la C?te d’Azur, BP 4229, FR–06304, Nice, France
Abstract:We investigate different approximate methods of computing the perturbations on the orbits of Oort cloud comets caused by passing stars, by checking them against an accurate numerical integration using Everhart’s RA15 code. The scenario under study is the one relevant for long-term simulations of the cloud’s response to a predefined set of stellar passages. Our sample of stellar encounters simulates those experienced by the Solar System currently, but extrapolated over a time of 1010 years. We measure the errors of perihelion distance perturbations for high-eccentricity orbits introduced by several estimators – including the classical impulse approximation and Dybczyński’s (1994, Celest. Mech. Dynam. Astron. 58, 1330–1338) method – and we study how they depend on the encounter parameters (approach distance and relative velocity). We introduce a sequential variant of Dybczyński’s approach, cutting the encounter into several steps whereby the heliocentric motion of the comet is taken into account. For the scenario at hand this is found to offer an efficient means to obtain accurate results for practically any domain of the parameter space.
Keywords:comets  impulse approximation  Oort cloud  stellar encounters
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