Observation of light echoes around very young stars

TL;DR

This study reports the detection of multiple light echoes around young stars, revealing their environments and distances, and suggesting possible links to the star formation process and the Solar System's Oort cloud.

Contribution

It provides the first detection of multiple light echoes around young stellar objects and estimates their distances and surrounding dust structures.

Findings

Detected light echoes around two young stars.

Estimated the distance to S CrA as 138 +/- 16 pc.

Suggested the dust environment may be related to star formation or the Oort cloud.

Abstract

The goal of the paper is to present new results on light echoes from young stellar objects. Broad band CCD images were obtained over three months at one-to-two week intervals for the field of NGC 6726, using the large field-of-view remotely-operated telescope on top of Cerro Burek. We detected scattered light echoes around two young, low-amplitude, irregular variable stars. Observations revealed not just one, but multiple light echoes from brightness pulses of the T Tauri star S CrA and the Herbig Ae/Be star R CrA. Analysis of S CrA's recurring echoes suggests that the star is located 138 +/- 16 pc from Earth, making these the closest echoes ever detected. The environment that scatters the stellar light from S CrA is compatible with an incomplete dust shell or an inclined torus some 10,000 AU in radius and containing $\sim$ $2 \times 10^{-3}$ $M_{\sun}$ of dust. The cause of such concentration at $\sim$ 10,000AU from the star is unknown. It could be the remnant of the envelope from which the star formed, but the distance of the cloud is remarkably similar to the nominal distance of the Oort cloud to the Sun, leading us to also speculate that the dust (or ice) seen around S CrA might have the same origin as the Solar System Oort cloud.