Marie-Eve Naud (University of Montreal)

Title: Detection and characterization of distant giant exoplanets using
seeing-limited direct imaging.

Abstract: Direct Imaging is a technique that is starting to yield very
interesting results in the field of exoplanet science. The handful of
giant planets discovered through this method revealed intriguing aspects
of the architecture of exoplanetary systems and of the nature of low-mass
companions. New dedicated high-contrast imagers such as GPI or SPHERE are
starting their operation and will allow the detection of giant planets of
masses and on orbits that are more and more similar to that of the giant
planets of our solar system.

Besides, simpler ``standard" imaging techniques can also yield the
discovery of planetary-mass companions, given that these are far enough
from their host. I will present the results of our Gemini-S/GMOS survey of
95 nearby young (<150 Myr) stars with deep seeing-limited i+z-band
imaging, which recently allowed the detection of a T3.5 planetary-mass
companion located 2000AU (42") from its host, the M3 star GU Psc. I’ll
discuss the properties of this system, which is in all likelihood part the
moving group AB Doradus (ABDMG; ~100Myr) and present the detailed
characterization we carried on the companion using Gemini-N/GNIRS NIR
spectroscopy, CFHT/WIRCam near-infrared (NIR) and WISE photometry, as well
as Keck/AO observations. Atmosphere models comparison points toward a Teff
= 1000 - 1100 K and log g = 4.5 - 5.0 for the companion, which gives a
mass of 9 - 13 MJup at the age of ABDMG. I'll also say a few word on a
recent discovery of a ~13Mjup object located 160AU from a M5.5
Tucana-Horologium member, through an extension of our GMOS survey.
These very distant companions, that appear to be quite rare, are quite
challenging to explain via traditional formation scenarios. They could be
the result of planet-planet scattering occurring early in the formation,
or could be formed similarly to a stellar companion via the fragmentation
of a molecular cloud. The existence of these distant planets is of utmost
interest because their large separation not only allows a relatively easy
detection, but also a more thorough characterization. They can thus make a
valuable comparison for other, closer-in planetary-mass companions that
will be uncovered by new planet-finder instruments and for atmosphere and
evolution models.