THE GEMINI/NICI PLANET-FINDING CAMPAIGN: THE FREQUENCY OF PLANETS AROUND YOUNG MOVING GROUP STARS

Abstract

We report results of a direct imaging survey for giant planets around 80\nmembers of the Beta Pic, TW Hya, Tucana-Horologium, AB Dor, and Hercules-Lyra\nmoving groups, observed as part of the Gemini NICI Planet-Finding Campaign. For\nthis sample, we obtained median contrasts of \\Delta H=13.9 mag at 1" in\ncombined CH4 narrowband ADI+SDI mode and median contrasts of \\Delta H=15.1 mag\nat 2" in H-band ADI mode. We found numerous (>70) candidate companions in our\nsurvey images. Some of these candidates were rejected as common-proper motion\ncompanions using archival data; we reobserved with NICI all other candidates\nthat lay within 400 AU of the star and were not in dense stellar fields. The\nvast majority of candidate companions were confirmed as background objects from\narchival observations and/or dedicated NICI campaign followup. Four co-moving\ncompanions of brown dwarf or stellar mass were discovered in this moving group\nsample: PZ Tel B (36+-6 MJup, 16.4+-1.0 AU, Biller et al. 2010), CD -35 2722B\n(31+-8 MJup, 67+-4 AU, Wahhaj et al. 2011), HD 12894B (0.46+-0.08 MSun,\n15.7+-1.0 AU), and BD+07 1919C (0.20+-0.03 MSun, 12.5+-1.4 AU). From a Bayesian\nanalysis of the achieved H band ADI and ASDI contrasts, using power-law models\nof planet distributions and hot-start evolutionary models, we restrict the\nfrequency of 1--20 MJup companions at semi-major axes from 10--150 AU to <18%\nat a 95.4% confidence level using DUSTY models and to <6% at a 95.4% using COND\nmodels.\n