Astrometric Accelerations as Dynamical Beacons: Efficiently Imaging Planets Around Young Accelerating Stars

Directly imaged planets and brown dwarfs are key tools for studying the formation, evolution, and atmospheric physics of substellar objects. Dynamical masses are especially valuable, as they enable robust tests of cooling models. However, imaging campaigns over the past twenty years have been limited by the low occurrence rate of long-period giant planets and brown dwarfs. One approach to overcome these challenges is to use astrometric accelerations to create a dynamically informed target sample by identifying stars with small proper motion changes between Hipparcos and Gaia that point to the presence of unseen substellar companions. We are using this strategy to carry out a high-contrast imaging survey of the accelerating stars most likely to harbor long-period giant planets and brown dwarfs. Here, I will present an overview of our program and exciting discoveries including the lowest-mass directly imaged planet with a dynamical mass measurement, AF Lep b. I will also share new results from follow-up observations to characterize the atmosphere of AF Lep b with JWST/NIRCam imaging.