  Future direct imaging missions will primarily observe planets that have been
previously detected, mostly via the radial velocity (RV) technique, to
characterize planetary atmospheres. In the meantime, direct imaging may
discover new planets within existing planetary systems that have bright enough
reflected flux, yet with insufficient signals for other methods to detect.
Here, we investigate the parameter space within which planets are unlikely to
be detected by RV in the near future due to precision limitations, but could be
discovered through reflected light with future direct imaging missions. We use
the HD 134987 system as a working example, combine RV and direct imaging
detection limit curves in the same parameter space through various assumptions,
and insert a fictitious planet into the system while ensuring it lies between
the RV and imaging detection limits. Planet validity tested through dynamical
simulations and retrieval tests revealed that the planet could indeed be
detected by imaging while remaining hidden from RV surveys. Direct imaging
retrieval was carried out using starshade simulations for two mission concepts:
the Starshade Rendezvous Probe that could be coupled with the Nancy Grace Roman
Space Telescope, and the Habitable Exoplanet Observatory. This method is
applicable to any other systems and high contrast direct imaging instruments,
and could help inform future imaging observations and data analysis on the
discovery of new exoplanets.
