# On the origin of the spiral morphology in the Elias 2-27 circumstellar disc

## TL;DR

This study investigates the origin of spiral structures in Elias 2-27's circumstellar disc, suggesting they may result from gravitational instabilities or an external massive planetary companion, based on simulations and observations.

## Contribution

It provides the first detailed simulation-based analysis of spiral formation mechanisms in Elias 2-27's disc, considering both gravitational instability and external companions.

## Key findings

- Disc may be gravitationally unstable or have an external companion.
- External companion could be a massive planet (~10-13 Jupiter masses).
- Companion likely located at 300-700 au from the star.

## Abstract

The young star Elias 2-27 has recently been observed to posses a massive circumstellar disc with two prominent large-scale spiral arms. In this Letter we perform three-dimensional Smoothed Particle Hydrodynamics simulations, radiative transfer modelling, synthetic ALMA imaging and an unsharped masking technique to explore three possibilities for the origin of the observed structures -- an undetected companion either internal or external to the spirals, and a self-gravitating disc. We find that a gravitationally unstable disc and a disc with an external companion can produce morphology that is consistent with the observations. In addition, for the latter, we find that the companion could be a relatively massive planetary mass companion (less than approximately 10 - 13 MJup) and located at large radial distances (between approximately 300 - 700 au). We therefore suggest that Elias 2-27 may be one of the first detections of a disc undergoing gravitational instabilities, or a disc that has recently undergone fragmentation to produce a massive companion.