Dynamical aspects of jovian irregular satellites

Thesis submitted for the degree of PhD, Queens University Belfast, UKComment: PhD thesis, 5 pages, 0 figures, Abstract & contact inf

An Orbital Stability Study of the Proposed Companions of SW Lyncis

We have investigated the dynamical stability of the proposed companions orbiting the Algol type short-period eclipsing binary SW Lyncis (Kim et al. 2010). The two candidate companions are of stellar to sub-stellar nature, and were inferred from timing measurements of the system's primary and secondary eclipses. We applied well-tested numerical techniques to accurately integrate the orbits of the two companions and to test for chaotic dynamical behaviour. We carried out the stability analysis within a systematic parameter survey varying both the geometries and orientation of the orbits of the companions, as well as their masses. In all our numerical integrations we found that the proposed SW Lyn multi-body system is highly unstable on time-scales on the order of 1000 years. Our results cast doubt on the interpretation that the timing variations are caused by two companions. This work demonstrates that a straightforward dynamical analysis can help to test whether a best-fit companion-based model is a physically viable explanation for measured eclipse timing variations. We conclude that dynamical considerations reveal that the propsed SW Lyncis multi-body system most likely does not exist or the companions have significantly different orbital properties as conjectured in Kim et al. (2010).Comment: 9 pages, 6 figures, 2 tables. Submitted to and accepted by JASS -- Journal for Astronomy and Space Sciences (using JKAS LaTeX style file

Chaotic dynamics of the planet in HD 196885 AB

Depending on the planetary orbit around the host star(s), a planet could orbit either one or both stars in a binary system as S-type or P-type, respectively. We have analysed the dynamics of the S-type planetary system in HD 196885 AB with an emphasis on a planet with a higher orbital inclination relative to the binary plane. The mean exponential growth factor of nearby orbits (MEGNO) maps are used as an indicator to determine regions of periodicity and chaos for the various choices of the planet's semimajor axis, eccentricity and inclination with respect to the previously determined observational uncertainties. We have quantitatively mapped out the chaotic and quasi-periodic regions of the system's phase space which indicate a likely regime of the planet's inclination. In addition, we inspect the resonant angle to determine whether alternation between libration and circulation occurs as a consequence of Kozai oscillations, a probable mechanism that can drive the planetary orbit to a very large inclination. Also, we demonstrate the possible higher mass limit of the planet and improve upon the current dynamical model based on our analysis.Comment: 10 pages, 9 figures (Accepted for publication at MNRAS

The Dynamical History of Chariklo and its Rings

Chariklo is the only small Solar system body confirmed to have rings. Given the instability of its orbit, the presence of rings is surprising, and their origin remains poorly understood. In this work, we study the dynamical history of the Chariklo system by integrating almost 36,000 Chariklo clones backwards in time for one Gyr under the influence of the Sun and the four giant planets. By recording all close encounters between the clones and planets, we investigate the likelihood that Chariklo's rings could have survived since its capture to the Centaur population. Our results reveal that Chariklo's orbit occupies a region of stable chaos, resulting in its orbit being marginally more stable than those of the other Centaurs. Despite this, we find that it was most likely captured to the Centaur population within the last 20 Myr, and that its orbital evolution has been continually punctuated by regular close encounters with the giant planets. The great majority (> 99%) of those encounters within one Hill radius of the planet have only a small effect on the rings. We conclude that close encounters with giant planets have not had a significant effect on the ring structure. Encounters within the Roche limit of the giant planets are rare, making ring creation through tidal disruption unlikely