  Exoplanetary science is increasingly prioritizing efforts toward direct
imaging of planetary systems, with emphasis on those that may enable the
detection and characterization of potentially habitable exoplanets. The recent
2020 Astronomy and Astrophysics decadal survey recommended the development of a
space-based direct imaging mission that has subsequently been referred to as
the Habitable Worlds Observatory (HWO). A fundamental challenge in the
preparatory work for the HWO search for exo-Earths is the selection of suitable
stellar targets. Much of the prior efforts regarding the HWO targets has
occurred within the context of exoplanet surveys that have characterized the
stellar properties for the nearest stars. The preliminary input catalog for HWO
consists of 164 stars, of which 30 are known exoplanet hosts to 70 planets.
Here, we provide a dynamical analysis for these 30 systems, injecting a
terrestrial planet mass into the Habitable Zone (HZ) and determining the
constraints on stable orbit locations due to the influence of the known
planets. For each system, we calculate the percentage of the HZ that is
dynamically viable for the potential presence of a terrestrial planet,
providing an additional metric for inclusion of the stars within the HWO target
list. Our analysis shows that, for 11 of the systems, less than 50% of the HZ
is dynamically viable, primarily due to the presence of giant planets whose
orbits pass near or through the HZ. These results demonstrate the impact that
known system architectures can have on direct imaging target selection and
overall system habitability.
