On the variability of the reflection nebula Van den Bergh 27 surrounding RY Tau

TL;DR

This paper analyzes optical variability in the reflection nebula vdB 27 around RY Tau, revealing light-echo patterns with apparent superluminal propagation due to geometric effects.

Contribution

It provides the first detailed analysis of short- and long-term optical variability and light-echo patterns in vdB 27, linking brightness changes to stellar illumination variations.

Findings

Observed apparent propagation speeds up to 3.6 times the speed of light.

Variations in nebular brightness are consistent with changes in star illumination.

Light-echo patterns suggest geometric projection effects influence observed variability.

Abstract

We present an analysis of the short- and long-term optical variability in Van den Bergh 27 (vdB 27), the reflection nebula surrounding RY Tau. The observed variations form a light-echo pattern, with apparent propagation speeds varying across different regions of the nebula and reaching up to approximately 3.6 c, consistent with geometric projection effects. The observed variations in nebular surface brightness are consistent with changes in illumination from the central star.