DIX Planetary Science Seminar

Despite being born with a wide range of spins, after approximately 1 Gyr of life, sun-like stars below 6250K all have spins that are correlated with their age rather than initial spin. Therefore, for old, main-sequence sun-like stars, constraining or approximating how fast they were spinning in their youths is almost impossible. This is somewhat unfortunate because the stellar spin in this era has significant effect on its planetary system, and knowing it would be useful. Higher spin interacts with the stellar dynamo to increase the levels of UV and X-ray emission, more quickly evaporating the transition disk and potentially evaporating Hydrogen and Helium from the atmospheres of close-orbiting planets. Moreover, the spin deforms the star around its equator, making it oblate, and affecting its gravitational potential. This change in potential induces a precession in the orbits of any planets, potentially bringing them into "secular resonance" (commensurabilities of precession rates that occur on much longer timescales than the orbital period) with one another, exchanging significant amounts of eccentricity and inclination. I show that these resonances are much more common than one might think, with ~20% of 3-planet transiting systems existing in configurations susceptible to these resonances. I then show that these secular resonances mediated by stellar oblateness can affect transit probabilities, surprisingly increasing the chance that a 3-planet system transits by up to 200% in the most extreme case. This allows me to then estimate updated probabilities that stars hosting transiting systems were born spinning fast.