A High-Contrast Imaging Survey of<i>SIM Lite</i>Planet Search Targets

Abstract

With the development of extreme high contrast ground-based adaptive optics\ninstruments and space missions aimed at detecting and characterizing Jupiter-\nand terrestrial-mass planets, it is critical that each target star be\nthoroughly vetted to determine whether it is a viable target given both the\ninstrumental design and scientific goals of the program. With this in mind, we\nhave conducted a high contrast imaging survey of mature AFGKM stars with the\nPALAO/PHARO instrument on the Palomar 200 inch telescope. The survey reached\nsensitivities sufficient to detect brown dwarf companions at separations of &gt;\n50 AU. The results of this survey will be utilized both by future direct\nimaging projects such as GPI, SPHERE and P1640 and indirect detection missions\nsuch as SIM Lite. Out of 84 targets, all but one have no close-in (0.45-1")\ncompanions and 64 (76%) have no stars at all within the 25" field-of-view. The\nsensitivity contrasts in the Ks passband ranged from 4.5 to 10 for this set of\nobservations. These stars were selected as the best nearby targets for\nhabitable planet searches owing to their long-lived habitable zones (&gt; 1\nbillion years). We report two stars, GJ 454 and GJ 1020, with previously\nunpublished proper motion companions. In both cases, the companions are stellar\nin nature and are most likely M dwarfs based on their absolute magnitudes and\ncolors. Based on our mass sensitivities and level of completeness, we can place\nan upper limit of ~17% on the presence of brown dwarf companions with masses\n&gt;40 MJ at separations of 1 arcsecond. We also discuss the importance of\nincluding statistics on those stars with no detected companions in their field\nof view for the sake of future companion searches and an overall understanding\nof the population of low-mass objects around nearby stars.\n