Imaging the inner astronomical unit of Herbig Be star HD 190073

TL;DR

This study uses infrared interferometry to image the inner astronomical unit of the Herbig Be star HD 190073, revealing a ring-like dust structure, potential binarity, and complex emission features.

Contribution

First direct imaging of the inner disk region of HD 190073 using CHARA and VLTI arrays, providing new insights into its structure and possible binarity.

Findings

Detected a sub-AU cavity with a ring radius of 1.14 AU.

Observed that about 48% of flux originates from the disk, with 15% inside the inner rim.

Identified potential binarity and inconsistent movement of the inner structure.

Abstract

Inner regions of protoplanetary disks host many complex physical processes such as star-disk interactions, magnetic fields, planet formation, and the migration of new planets. To directly study this region requires milli-arcsecond angular resolution, beyond the diffraction limit of the world's largest optical telescopes and even too small for the mm-wave interferometer ALMA. However, we can use infrared interferometers to image the inner astronomical unit. Here, we present new results from the CHARA and VLTI arrays for the young and luminous Herbig Be star HD 190073. We detect a sub-AU cavity surrounded by a ring-like structure that we interpret as the dust destruction front. We model the shape with 6 radial profiles, 3 symmetric and 3 asymmetric, and present a model-free image reconstruction. All the models are consistent with a near face-on disk with inclination $\lesssim 20^\circ$, and we measure an average ring radius of 1.4 $\pm 0.2$ mas (1.14 AU). Around $48\%$ of the total flux comes from the disk with ~$15\%$ of that emission appearing to emerge from inside the inner rim. The cause of emission is still unclear, perhaps due to different dust grain compositions or gas emission. The skewed models and the imaging point to an off-center star, possibly due to binarity. Our image shows a sub-AU structure, which seems to move between the two epochs inconsistently with Keplerian motion and we discuss possible explanations for this apparent change.