Sparse aperture masking at the VLT II. Detection limits for the eight debris disks stars $\beta$ Pic, AU Mic, 49 Cet, $\eta$ Tel, Fomalhaut, g Lup, HD181327 and HR8799

TL;DR

This study used sparse aperture masking at the VLT to set upper mass detection limits for potential companions around eight debris disk stars, improving understanding of their close environments.

Contribution

It applies SAM technique to debris disk stars to establish new detection limits for low-mass companions near these stars.

Findings

No close companions detected within 0.5 arcseconds.

Derived Jupiter-mass detection limits using theoretical models.

Provided upper mass limits for potential companions.

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 probe 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 ( $\beta$ Pictoris, AU Microscopii, 49 Ceti, $\eta$ Telescopii, Fomalhaut, g Lupi, HD181327 and HR8799) with SAM technique on the NaCo instrument at the 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 few times the diffraction limit of the telescope around each target star.