Near-IR imaging of T Cha: evidence for scattered-light disk structures at solar system scales

TL;DR

This study uses near-infrared imaging and aperture masking to analyze the disk around T Chamaeleontis, concluding that observed signals are due to disk scattering structures rather than a planetary companion.

Contribution

It demonstrates that the closure phase signals previously attributed to a companion are better explained by scattered light from the disk, clarifying the nature of the observed features.

Findings

Closure phase signals are consistent across multiple observations.

No relative motion detected over 3 years rules out a companion.

Disk scattering explains the observed signals.

Abstract

T Chamaeleontis is a young star surrounded by a transitional disk, and a plausible candidate for ongoing planet formation. Recently, a substellar companion candidate was reported within the disk gap of this star. However, its existence remains controversial, with the counter-hypothesis that light from a high inclination disk may also be consistent with the observed data. The aim of this work is to investigate the origin of the observed closure phase signal to determine if it is best explained by a compact companion. We observed T Cha in the L and K s filters with sparse aperture masking, with 7 datasets covering a period of 3 years. A consistent closure phase signal is recovered in all L and K s datasets. Data were fit with a companion model and an inclined circumstellar disk model based on known disk parameters: both were shown to provide an adequate fit. However, the absence of expected relative motion for an orbiting body over the 3-year time baseline spanned by the observations rules out the companion model. Applying image reconstruction techniques to each dataset reveals a stationary structure consistent with forward scattering from the near edge of an inclined disk.