First-light LBT nulling interferometric observations: warm exozodiacal dust resolved within a few AU of eta Corvi

TL;DR

This paper presents the first nulling interferometric observations of eta Corvi with the LBTI, resolving warm exozodiacal dust within a few AU, revealing a closer and possibly asymmetric dust distribution than previously modeled.

Contribution

First nulling interferometric observations with LBTI of eta Corvi's warm dust, providing new insights into its spatial distribution and properties.

Findings

Warm dust located at 0.5-1.0 AU, closer than previous models predicted.

Inner disk likely coplanar with the outer disk, but not a scaled version of the Solar zodiacal cloud.

Dust may be produced by recent collision, with small grains or asymmetry affecting observations.

Abstract

We report on the first nulling interferometric observations with the Large Binocular Telescope Interferometer (LBTI), resolving the N' band (9.81 - 12.41 um) emission around the nearby main-sequence star eta Crv (F2V, 1-2 Gyr). The measured source null depth amounts to 4.40% +/- 0.35% over a field-of-view of 140 mas in radius (~2.6\,AU at the distance of eta Corvi) and shows no significant variation over 35{\deg} of sky rotation. This relatively low null is unexpected given the total disk to star flux ratio measured by Spitzer/IRS (~23% across the N' band), suggesting that a significant fraction of the dust lies within the central nulled response of the LBTI (79 mas or 1.4 AU). Modeling of the warm disk shows that it cannot resemble a scaled version of the Solar zodiacal cloud, unless it is almost perpendicular to the outer disk imaged by Herschel. It is more likely that the inner and outer disks are coplanar and the warm dust is located at a distance of 0.5-1.0 AU, significantly closer than previously predicted by models of the IRS spectrum (~3 AU). The predicted disk sizes can be reconciled if the warm disk is not centrosymmetric, or if the dust particles are dominated by very small grains. Both possibilities hint that a recent collision has produced much of the dust. Finally, we discuss the implications for the presence of dust at the distance where the insolation is the same as Earth's (2.3 AU).