Ruling out Stellar Companions and Resolving the Innermost Regions of Transitional Disks with the Keck Interferometer

TL;DR

This study used Keck Interferometer observations at 2 microns to investigate the innermost regions of transitional disks, aiming to rule out stellar companions as the cause of dust depletion and to explore disk structures related to planet formation.

Contribution

The paper provides high-resolution interferometric data that exclude stellar companions as the primary cause of inner disk clearing in several transitional disks, supporting the planet formation hypothesis.

Findings

Stellar companions with flux ratios ≥0.05 and separations 2.5-30 mas are excluded in most targets.

Most targets show near-infrared excess and signs of accretion, indicating active inner disk regions.

Observations reveal spatially resolved inner disk structures consistent with gaps possibly caused by planet formation.

Abstract

With the Keck Interferometer, we have studied at 2 um the innermost regions of several nearby, young, dust depleted "transitional" disks. Our observations target five of the six clearest cases of transitional disks in the Taurus/Auriga star-forming region (DM Tau, GM Aur, LkCa 15, UX Tau A, and RY Tau) to explore the possibility that the depletion of optically thick dust from the inner disks is caused by stellar companions rather than the more typical planet-formation hypothesis. At the 99.7% confidence level, the observed visibilities exclude binaries with flux ratios of at least 0.05 and separations ranging from 2.5 to 30 mas (0.35 - 4 AU) over >= 94% of the area covered by our measurements. All targets but DM Tau show near-infrared excess in their SED higher than our companion flux ratio detection limits. While a companion has previously been detected in the candidate transitional disk system CoKu Tau/4, we can exclude similar mass companions as the typical origin for the clearing of inner dust in transitional disks and of the near-infrared excess emission. Unlike CoKu Tau/4, all our targets show some evidence of accretion. We find that all but one of the targets are clearly spatially resolved, and UX Tau A is marginally resolved. Our data is consistent with hot material on small scales (0.1 AU) inside of and separated from the cooler outer disk, consistent with the recent SED modeling. These observations support the notion that some transitional disks have radial gaps in their optically thick material, which could be an indication for planet formation in the habitable zone (~ a few AU) of a protoplanetary disk.