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Planetesimal Belts in Misaligned Wide Stellar Binaries https://doi.org/10.17863/CAM.114373 https://doi.org/10.17863/CAM.114373 Young, Steven Wyatt, Mark Some main sequence and post-main sequence stars show signatures of close-in hot dust which cannot have formed there or been produced in-situ as the collisional timescales at these locations are much smaller than the ages of the systems. Hence, there must exist some dynamical mechanism to deliver rocky bodies to small distances on timescales of 10 − 10⁴ Myrs. This thesis examines the feasibility and detectability of one of these potential mechanisms: the eccentric Kozai-Lidov effect whereby a stellar companion on a misaligned wide orbit perturbs planetesimals to high eccentricities. First, in order to explain the mys- terious light-curve of KIC 8462852, one component of a wide binary star system in the Kepler field with deep, irregular and aperiodic dips in its light-curve, a Monte Carlo model of planetesimal belts in wide stellar binaries was created. It found that the occurrence rate of KIC 8462852-like observations in the Kepler field is 10⁻⁸ and hence that the probability of the Kepler telescope observing such phenomena to be 10⁻³. It also found that the systems most likely to be observed have planetesimal belts at 10² − 10³ au, stellar companions at 10² − 10⁴ au, stellar masses of ≥ 1M⊙ and ages of 10² − 10³ Myrs. Therefore, despite being in the right age range and with a companion at the right distance, it is unlikely that the EKM caused by the companion star is the cause of these observations. This thesis then followed the surface density evolution of three narrow debris discs, as well as one wide disc, with a stellar companion at acomp = 878 au and an inclination of 88◦. It found that the EKM imprinted a petal shaped structure on the narrow discs due to the disc particles librating between a fixed set of values for the longitude of pericentre which depend only on the initial inclination. As the evolution of the wide disc is the superposition of the evolution of the three narrow discs, these petal structures combined to produce an X-shaped structure. ‘Thermal emission’ images were then produced for the wide disc to see if the X-shaped structure would be observable. It was found that, as the tips of the structure corresponding to the apocentres of eccentric orbits were more dense, they dominate the thermal emission and the structure appears as four ‘clumps’. The time evolution of the fractional luminosity and flux at 5 and 12 μm for these discs was then calculated. The fractional luminosity did not vary by more than an order of magnitude as it was dominated by distant cold dust and hence this mechanism cannot explain the high values of fractional luminosity associated with extreme debris discs. Likewise, whilst the infrared flux at 5 and 12 μm does increase by orders of magnitude to ∼ 10⁻⁴, it is not high enough to explain the brightest exozodi like η Corvi or β Leo, though it could explain fainter exozodi. University of Cambridge 2024-05-31 Thesis Doctoral Doctor of Philosophy (PhD) eng https://www.repository.cam.ac.uk/handle/1810/377601 https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/832ae8a0-1304-495b-9176-cec5302d8d08/download 9ddf75cdf47fdd2a5087f5a6c8e5c725 https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/db626b50-91b0-438e-9b64-f8c0231bf67c/download 87eda9de84448d1f82354d60eee3eb5f http://purl.org/NET/rdflicense/allrightsreserved Astronomy Debris Discs Exocomets Exoplanets Exozodiacal Dust Extreme Debris Discs Kozai-Lidov Mechanism