Sparse aperture masking at the VLT

II. Detection limits for the eight debris disks stars β Pic, AU Mic, 49 Cet, η Tel, Fomalhaut, g Lup, HD 181327 and HR 8799^⋆,⋆⋆

¹ LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, Univ. Paris Diderot, UPMC Univ. Paris 06, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
e-mail: lucien.gauchet@obspm.fr
² Univ. Grenoble Alpes, IPAG, 38000 Grenoble, France
³ CNRS, IPAG, 38000 Grenoble, France
⁴ Observatoire de l’Université de Genève, 51 chemin des Maillettes, 1290 Sauverny, Switzerland
⁵ European Southern Observatory, Casilla 19001, Santiago 19, Chile

Received: 24 April 2015
Accepted: 2 June 2016

Abstract

Context. The formation of planetary systems is a common, yet complex mechanism. Numerous stars have been identified to possess a debris disk, a proto-planetary disk or a planetary system. The understanding of such formation process requires the study of debris disks. These targets are substantial and particularly suitable for optical and infrared observations. Sparse aperture masking (SAM) is a high angular resolution technique strongly contributing to probing the region from 30 to 200 mas around the stars. This area is usually unreachable with classical imaging, and the technique also remains highly competitive compared to vortex coronagraphy.

Aims. We aim to study debris disks with aperture masking to probe the close environment of the stars. Our goal is either to find low-mass companions, or to set detection limits.

Methods. We observed eight stars presenting debris disks (β Pictoris, AU Microscopii, 49 Ceti, η Telescopii, Fomalhaut, g Lupi, HD 181327, and HR 8799) with SAM technique on the NaCo instrument at the Very Large Telescope (VLT).

Results. No close companions were detected using closure phase information under 0.5′′ of separation from the parent stars. We obtained magnitude detection limits that we converted to Jupiter masses detection limits using theoretical isochrones from evolutionary models.

Conclusions. We derived upper mass limits on the presence of companions in the area of a few times the telescope’s diffraction limits around each target star.