Abstract
Context. Dusty debris disks around pre- and main-sequence stars are potential signposts for the existence of planetesimals and exoplanets. Giant planet formation is therefore expected to play a key role in the evolution of the disk. This is indirectly confirmed by extant submillimeter near-infrared images of young protoplanetary and cool dusty debris disks around main-sequence stars that usually show substantial spatial structures. With two decades of direct imaging of exoplanets already studied, it is striking to note that a majority of recent discoveries of imaged giant planets have been obtained around young early-type stars hosting a circumstellar disk. Aims. Our aim was to create a direct imaging program designed to maximize our chances of giant planet discovery and target 22 young early-type stars. About half of them show indications of multi-belt architectures. Methods. Using the IRDIS dual-band imager and the IFS integral field spectrograph of SPHERE to acquire high-constrast coronagraphic differential near-infrared images, we conducted a systematic search in the close environment of these young, dusty, and early-type stars. We used a combination of angular and spectral differential imaging to reach the best detection performances down to the planetary mass regime. Results. We confirm that companions detected around HIP 34276, HIP 101800, and HIP 117452 are stationary background sources and binary companions. The companion candidates around HIP 8832, HIP 16095, and HIP 95619 are determined as background contaminations. Regarding the stars for which we infer the presence of debris belts, a theoretical minimum mass for planets required to clear the debris gaps can be calculated. The dynamical mass limit is at least 0.1 MJ and can exceed 1 MJ. Direct imaging data is typically sensitive to planets down to ~3.6 MJ at 1′′, and 1.7 MJ in the best case. These two limits tightly constrain the possible planetary systems present around each target. These systems will be probably detectable with the next generation of planet imagers.
Highlights
How giant planets form and evolve is one of the biggest challenges of modern astronomy and remains a subject of heated debate. This major goal is directly connected to the ultimate search for life over the horizon 2030 to 2040, several astrophysical, biological, and technical steps must be carried out in that perspective
Each individual discovery of a giant planet and young planetary system using direct imaging is rich in terms of scientific exploitation and characterization, as these systems offer the possibility of (i) directly probing the presence of planets in their birth environments, (ii) enabling the orbital, physical, and spectral characterization of young massive Jupiters, (iii) characterizing the population of giant planets at all separations in synergy with complementary techniques such as astrometry (Gaia) and radial velocity adapted to filter stellar activity
Using the IRDIS and integral field spectrograph (IFS) signal-to-noise ratio (S/N) maps provided by SpeCal, we identified a total of eight companion candidates by eye at relatively large separation (≥3.0 ) in the IRDIS fields of view of six targets (HIP 16095, HIP 95619, HIP 101800, HIP 34276, HIP 117452, and HIP 8832) of the complete survey
Summary
How giant planets form and evolve is one of the biggest challenges of modern astronomy and remains a subject of heated debate. Alternative mechanisms are proposed, such as pebbles accretion to enable core accretion to operate at wide orbits (Lambrechts & Johansen 2012), inward/outward migration or planet–planet (Crida et al 2009; Bromley & Kenyon 2014) or the possibility to have several mechanisms forming giant planets (Boley 2009) In this context, each individual discovery of a giant planet and young planetary system using direct imaging is rich in terms of scientific exploitation and characterization, as these systems offer the possibility of (i) directly probing the presence of planets in their birth environments, (ii) enabling the orbital, physical, and spectral characterization of young massive Jupiters, (iii) characterizing the population of giant planets at all separations in synergy with complementary techniques such as astrometry (Gaia) and radial velocity adapted to filter stellar activity
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