Architectures of transiting planetary systems

Thesis Supervisors: Robert de Rosa


Long-period stellar and substellar companions can play a significant role in the formation and dynamical evolution of planetary systems. For example, the truncation of the protoplanetary disk can significantly shorten the lifespan of a disk, as well as limiting the amount of material available to form planets. After the planet formation process has concluded, a long-period companion can significantly alter the architecture of the inner system. Large mutual inclinations can induce Kozai-Lidov oscillations in the orbit of the planet If these oscillations drive the eccentricity high enough, they can induce high- eccentricity migration, further reducing the semi-major axis of the planet. Despite the potentially disruptive influence of an external companion, numerous examples of planetary systems with companions beyond 10 au have been discovered.

We have an ongoing (P111/2) program with SPHERE to detect long-period stellar and substellar companions to transiting planets that exhibit some evidence—either from radial velocities or astrometry—of an external companion. These systems are ideal laboratories to explore the interaction between the inner planetary system and more distant companion as the orbital plane of the inner system is known.

The primary objective of the studentship is the reduction and analysis of the SPHERE datasets, characterization of any detected companions, and calculation of sensitivity limits. The influence of detected companions on the inner system will be studied in conjunction with  local collaborators. For the non-detections, the limits will be combined with the RV/astrometric trends to place constraints on the properties of the companion.

For a longer studentship, the project could be extended to perform a more comprehensive study of the multiplicity of TESS planet-hosting stars. We would combine published detection limits from speckle and AO imaging, with radial velocity measurements and (where available) astrometric measurements from Hipparcos/Gaia to perform the most complete multiplicity census for these hosts to-date.

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