Imaging protoplanets: observing transition disks with non-redundant masking

TL;DR

This paper explores the use of non-redundant masking imaging to detect forming planets in transition disks, highlighting its potential and limitations in distinguishing between disk features and planetary companions.

Contribution

It demonstrates the application of non-redundant masking to transition disks and discusses methods to differentiate between disk scattering and planetary signals.

Findings

T Cha data likely explained by a static, forward-scattering disk

LkCa 15 data best explained by multiple orbiting companions

Highlights limitations of non-redundant masking for extended sources

Abstract

Transition disks, protoplanetary disks with inner clearings, are promising objects in which to directly image forming planets. The high contrast imaging technique of non-redundant masking is well posed to detect planetary mass companions at several to tens of AU in nearby transition disks. We present non-redundant masking observations of the T Cha and LkCa 15 transition disks, both of which host posited sub-stellar mass companions. However, due to a loss of information intrinsic to the technique, observations of extended sources (e.g. scattered light from disks) can be misinterpreted as moving companions. We discuss tests to distinguish between these two scenarios, with applications to the T Cha and LkCa 15 observations. We argue that a static, forward-scattering disk can explain the T Cha data, while LkCa 15 is best explained by multiple orbiting companions.