Constrained Reference Star Differential Imaging: Enabling High-Fidelity Imagery of Highly Structured Circumstellar Disks

TL;DR

This paper introduces constrained RDI, a novel high-contrast imaging technique that uses disk models or polarized images to prevent light loss, enabling clearer imaging of circumstellar disks and embedded planets.

Contribution

The paper presents a new constrained RDI method that significantly reduces oversubtraction in high-contrast imaging, improving detection and analysis of circumstellar disks and exoplanets.

Findings

Successful detection of AB Aurigae disk without oversubtraction.

Decisive recovery of spectral signature of AB Aurigae b.

Potential application for JWST coronagraphic imaging.

Abstract

High-contrast imaging presents us with the opportunity to study circumstellar disks and the planets still embedded within them -- providing key insights into the formation and evolution of planetary systems. However, the post-processing techniques that are often needed to suppress stellar halo light typically result in significant and variable loss of circumstellar light, even when using relatively conservative approaches like reference star differential imaging (RDI). We introduce ``constrained reference star differential imaging" (constrained RDI), a new class of RDI point spread function (PSF)-subtraction techniques for systems with circumstellar disks. Constrained RDI utilizes either high-resolution polarized intensity (PI) images or disk models to severely limit or even eliminate the signal loss due to oversubtraction that is common to RDI. We demonstrate the ability of constrained RDI utilizing polarimetric data to yield an oversubtraction-free detection of the AB Aurigae protoplanetary disk in total intensity. PI-constrained RDI allows us to decisively recover the spectral signature of the confirmed, recently-discovered protoplanet, AB Aurigae b (Currie et al. 2022). We further demonstrate that constrained RDI can be a powerful analysis tool for soon-to-be-acquired James Webb Space Telescope coronagraphic imaging of disks. In both cases, constrained RDI provides analysis-ready products that enable more detailed studies of disks and more robust verification of embedded exoplanets.