Marshall Johnson (Postdoc, Astronomy Dept)
Despite more than two decades of progress since the discovery of the first exoplanets, key questions prompted by the first discoveries remain unanswered. Perhaps the best-studied class of planets are the hot Jupiters, but it is still unclear how these planets migrate from where they form beyond the snow line to the short-period orbits where we see them today (or even if some hot Jupiters might form in situ). One key parameter for answering this question is the alignment (or lack thereof) between the planetary orbit and the stellar rotation, which is a tracer of planets’ dynamical and migration histories. Many hot Jupiters are observed to have severely misaligned orbits, and many mechanisms (including but not limited to migration) have been proposed to generate misaligned orbits. Previous observational constraints have been unable to definitively distinguish among these mechanisms. I will present initial results from an extensive program to address this problem using statistical analyses of the spin-orbit misalignments of hot Jupiters around A and early F stars, and correlations with other parameters of the systems. These include new high-resolution imaging observations, which, when combined with Gaia DR2 astrometry, allow me perform a comprehensive survey for stellar companions to these stars from a few to tens of thousands of AU. I will also demonstrate that, through the combination of transit observations and Gaia DR2 parallaxes, we are able to measure the stellar ages to a precision of typically 500 Myr, much better than is possible for most field stars and providing further constraints on misalignment mechanisms.