The inner environment of Z~CMa: High-Contrast Imaging Polarimetry with NaCo

TL;DR

This study uses high-contrast imaging polarimetry to reveal detailed structures and dynamics in the complex inner environment of the Z CMa binary system, including a dust envelope, extended features, and a new outburst.

Contribution

It provides the first high-contrast polarized images of Z CMa's inner 400 au environment, revealing complex structures and orbital motion, and reports a new outburst event.

Findings

Resolved the binary in polarized light at H and Ks bands.

Detected a new outburst driven by the Herbig star.

Identified complex dust structures and a bright clump.

Abstract

Context. Z\,CMa is a binary composed of an embedded Herbig Be and an FU Ori class star separated by $\sim100$ au. Observational evidence indicate a complex environment in which each star has a circumstellar disk and drives a jet, and the whole system is embedded in a large dusty envelope. Aims. We aim to probe the circumbinary environment of Z\,CMa in the inner 400 au in scattered light. Methods. We use high contrast imaging polarimetry with VLT/NaCo at $H$ and $K_s$ bands. Results. The central binary is resolved in both bands. The polarized images show three bright and complex structures: a common dust envelope, a sharp extended feature previously reported in direct light, and an intriguing bright clump located $0\farcs3$ south of the binary, which appears spatially connected to the sharp extended feature. Conclusions.We detect orbital motion when compared to previous observations, and report a new outburst driven by the Herbig star. Our observations reveal the complex inner environment of Z\,CMa with unprecedented detail and contrast.