Imaging the dust sublimation front of a circumbinary disk

TL;DR

This paper presents the first high-resolution near-infrared image of a post-AGB binary with a circumbinary dust disk, revealing the dust sublimation front and a potential accretion disk around the secondary star, advancing understanding of binary and disk evolution.

Contribution

First milliarcsecond-scale IR image of a post-AGB binary showing detailed disk structure and the secondary star's flux, highlighting the presence of a circum-companion accretion disk.

Findings

Resolved the dust sublimation front similar to protoplanetary disks

Detected a 4% flux signal from the secondary star

Indicated a compact accretion disk around the secondary

Abstract

We present the first near-IR milli-arcsecond-scale image of a post-AGB binary that is surrounded by hot circumbinary dust. A very rich interferometric data set in six spectral channels was acquired of IRAS08544-4431 with the new RAPID camera on the PIONIER beam combiner at the Very Large Telescope Interferometer (VLTI). A broadband image in the \textit{H} band was reconstructed by combining the data of all spectral channels using the SPARCO method. We spatially separate all the building blocks of the IRAS08544-4431 system in our milliarcsecond-resolution image. Our dissection reveals a dust sublimation front that is strikingly similar to that expected in early-stage protoplanetary disks, as well as an unexpected flux signal of $\sim$4\% from the secondary star. The energy output from this companion indicates the presence of a compact circum-companion accretion disk, which is likely the origin of the fast outflow detected in H$\alpha$. Our image provides the most detailed view into the heart of a dusty circumstellar disk to date. Our results demonstrate that binary evolution processes and circumstellar disk evolution can be studied in detail in space and over time.