VLT/NACO coronagraphic observations of fine structures in the disk of beta Pictoris

TL;DR

This study uses VLT/NACO coronagraphic imaging to analyze the inner disk structure of beta Pictoris, revealing new asymmetries and assessing image processing limitations.

Contribution

It provides detailed observations of the beta Pictoris disk using different coronagraphs and spectral bands, highlighting asymmetries and the effects of image deconvolution.

Findings

Detected asymmetries in disk structure not previously reported.

Achieved close-in disk imaging down to 0.7" (13.5 AU).

Demonstrated that deconvolution can introduce artificial features.

Abstract

We present ground-based observations of the disk around the A-type star $\beta$ Pictoris to perform a close inspection of the inner disk morphology. Images were collected with NACO, the AO-assisted near-IR instrument on the VLT (ESO) which includes two types of coronagraphs: classical Lyot masks and phase masks. In this program we took advantage of both types of coronagraphs in two spectral bands, H-band for the Lyot mask and Ks-band for the phase mask. In addition, we simulated an extended object to understand the limitations in deconvolution of coronagraphic images. The reduced coronagraphic images allow us to carefully measure the structures of the debris disk and reveal a number of asymmetries of which some were not reported before (position, elevation and thickness of the warp). In this program, the circumstellar material is visible as close as 0.7" ($13.5 $AU) owing to the phase mask while the Lyot mask generates artifacts which hamper the detection of the dust at separations closer than 1.2" ($23.2 $AU). The point source detection limit is compared to recently published observations of a planet candidate. Finally, the simulations show that deconvolution of coronagraphic data may indeed produce artificial patterns within the image of a disk.