  With the development of extreme high contrast ground-based adaptive optics
instruments and space missions aimed at detecting and characterizing Jupiter-
and terrestrial-mass planets, it is critical that each target star be
thoroughly vetted to determine whether it is a viable target given both the
instrumental design and scientific goals of the program. With this in mind, we
have conducted a high contrast imaging survey of mature AFGKM stars with the
PALAO/PHARO instrument on the Palomar 200 inch telescope. The survey reached
sensitivities sufficient to detect brown dwarf companions at separations of >
50 AU. The results of this survey will be utilized both by future direct
imaging projects such as GPI, SPHERE and P1640 and indirect detection missions
such as SIM Lite. Out of 84 targets, all but one have no close-in (0.45-1")
companions and 64 (76%) have no stars at all within the 25" field-of-view. The
sensitivity contrasts in the Ks passband ranged from 4.5 to 10 for this set of
observations. These stars were selected as the best nearby targets for
habitable planet searches owing to their long-lived habitable zones (> 1
billion years). We report two stars, GJ 454 and GJ 1020, with previously
unpublished proper motion companions. In both cases, the companions are stellar
in nature and are most likely M dwarfs based on their absolute magnitudes and
colors. Based on our mass sensitivities and level of completeness, we can place
an upper limit of ~17% on the presence of brown dwarf companions with masses
>40 MJ at separations of 1 arcsecond. We also discuss the importance of
including statistics on those stars with no detected companions in their field
of view for the sake of future companion searches and an overall understanding
of the population of low-mass objects around nearby stars.
