We have carried out high contrast imaging of 70 young , nearby B and A stars to search for brown dwarf and planetary companions as part of the Gemini NICI Planet-Finding Campaign .
Our survey represents the largest , deepest survey for planets around high-mass stars ( \approx 1.5–2.5 M _ { \sun } ) conducted to date and includes the planet hosts \beta Pic and Fomalhaut .
We obtained follow-up astrometry of all candidate companions within 400 AU projected separation for stars in uncrowded fields and identified new low-mass companions to HD 1160 and HIP 79797 .
We have found that the previously known young brown dwarf companion to HIP 79797 is itself a tight ( 3 AU ) binary , composed of brown dwarfs with masses 58 ^ { +21 } _ { -20 } M _ { Jup } and 55 ^ { +20 } _ { -19 } M _ { Jup } , making this system one of the rare substellar binaries in orbit around a star .
Considering the contrast limits of our NICI data and the fact that we did not detect any planets , we use high-fidelity Monte Carlo simulations to show that fewer than 20 % of 2 M _ { \sun } stars can have giant planets greater than 4 M _ { Jup } between 59 and 460 AU at 95 % confidence , and fewer than 10 % of these stars can have a planet more massive than 10 M _ { Jup } between 38 and 650 AU .
Overall , we find that large-separation giant planets are not common around B and A stars : fewer than 10 % of B and A stars can have an analog to the HR 8799 b ( 7 M _ { Jup } , 68 AU ) planet at 95 % confidence .
We also describe a new Bayesian technique for determining the ages of field B and A stars from photometry and theoretical isochrones .
Our method produces more plausible ages for high-mass stars than previous age-dating techniques , which tend to underestimate stellar ages and their uncertainties .