The International Deep Planet Survey

II. The frequency of directly imaged giant exoplanets with stellar mass^⋆

¹ LESIA, Observatoire de Paris, CNRS, Université Paris Diderot, Université Pierre et Marie Curie, 5 place Jules Janssen, 92190 Meudon, France
e-mail: raphael.galicher@obspm.fr
² Groupement d’Intérêt Scientifique PHASE (Partenariat Haute résolution Angulaire Sol Espace) between ONERA, Observatoire de Paris, CNRS and Université Paris Diderot, 75000 Paris, France
³ National Research Council Canada, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada
⁴ Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550, USA
⁵ Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, CA 94305, USA
⁶ Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA
⁷ Lunar and Planetary Laboratory, University of Arizona, Tucson AZ 85721, USA
⁸ CASS, University of California San Diego, La Jolla, CA 92093-0424, USA
⁹ Department of Physics and Astronomy, University of Georgia, Athens, GA 30602-2451, USA
¹⁰ Arizona State University, Tempe, AZ 85281, USA
¹¹ Département de Physique, Université de Montréal, C.P. 6128 Succ. Centre-Ville, Montréal, QC H3C 3J7, Canada
¹² SETI Institute, Carl Sagan Center, 189 Bernardo Avenue, Mountain View, CA 94043, USA

Received: 25 November 2016
Accepted: 17 July 2016

Abstract

Context. Radial velocity and transit methods are effective for the study of short orbital period exoplanets but they hardly probe objects at large separations for which direct imaging can be used.

Aims. We carried out the international deep planet survey of 292 young nearby stars to search for giant exoplanets and determine their frequency.

Methods. We developed a pipeline for a uniform processing of all the data that we have recorded with NIRC2/Keck II, NIRI/Gemini North, NICI/Gemini South, and NACO/VLT for 14 yr. The pipeline first applies cosmetic corrections and then reduces the speckle intensity to enhance the contrast in the images.

Results. The main result of the international deep planet survey is the discovery of the HR 8799 exoplanets. We also detected 59 visual multiple systems including 16 new binary stars and 2 new triple stellar systems, as well as 2279 point-like sources. We used Monte Carlo simulations and the Bayesian theorem to determine that $\mathrm{1.0}{\mathrm{5}}_{-0.70}^{\mathrm{+}\mathrm{2.80}}\mathrm{\%}$ of stars harbor at least one giant planet between 0.5 and 14 M_J and between 20 and 300 AU. This result is obtained assuming uniform distributions of planet masses and semi-major axes. If we consider power law distributions as measured for close-in planets instead, the derived frequency is $\mathrm{2.3}{\mathrm{0}}_{-1.55}^{\mathrm{+}\mathrm{5.95}}\mathrm{\%}$, recalling the strong impact of assumptions on Monte Carlo output distributions. We also find no evidence that the derived frequency depends on the mass of the hosting star, whereas it does for close-in planets.

Conclusions. The international deep planet survey provides a database of confirmed background sources that may be useful for other exoplanet direct imaging surveys. It also puts new constraints on the number of stars with at least one giant planet reducing by a factor of two the frequencies derived by almost all previous works.