VLT/SPHERE survey for exoplanets around young early-type stars, including systems with multi-belt architectures

¹ Unidad Mixta Internacional Franco-Chilena de Astronomía, CNRS/INSU UMI 3386 and Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
² Univ. Lyon, Univ. Lyon1, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, 69230 Saint-Genis-Laval, France
e-mail: maxime.lombart@ens-lyon.fr
³ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
⁴ Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile
⁵ Université Cote d’Azur, OCA, CNRS, Lagrange, France
⁶ LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
⁷ INAF – Osservatorio Astronomico di Padova, Vicolo dell’ Osservatorio 5, 35122 Padova, Italy
⁸ SUPA, Institute for Astronomy, The University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK
⁹ CRAL, UMR 5574, CNRS, Université de Lyon, Ecole Normale Suprieure de Lyon, 46 allée d’Italie, 69364 Lyon Cedex 07, France
¹⁰ Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 1111, Valparaíso, Chile
¹¹ Núcleo Milenio Formación Planetaria – NPF, Universidad de Valparaíso, Valparaíso, Chile
¹² Space Telescope Science Institute, 3700 San Martin Dr. Baltimore, MD 21218, USA
¹³ Institut für Astronomie und Astrophysik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
¹⁴ Physikalisches Institut, Universität Bern, Gesellschaftsstr. 6, 3012 Bern, Switzerland
¹⁵ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
¹⁶ Departamento de Ciencias Fisicas, Facultad de Ciencias Exactas, Universidad Andres Bello, Av. Fernandez Concha 700, Las Condes, Santiago, Chile

Received: 13 March 2020
Accepted: 13 May 2020

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 M_J and can exceed 1 M_J. Direct imaging data is typically sensitive to planets down to ~3.6 M_J at 1′′, and 1.7 M_J 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.