# The Nearby Evolved Stars Survey: I. JCMT/SCUBA-2 Sub-millimetre detection of the detached shell of U Antliae

## TL;DR

This paper presents high-resolution sub-millimetre observations of the detached shell around U Antliae, revealing detailed shell structure, grain size variation, and estimating the shell's dust mass and age of the thermal pulse event.

## Contribution

It provides the first high-resolution sub-millimetre imaging of U Antliae's detached shell, combined with modeling to analyze shell structure and dust properties.

## Key findings

- Shell detected out to 56 arcseconds at 3σ level.
- Shell dust mass estimated at approximately 2.0 x 10^{-5} solar masses.
- Thermal pulse responsible for shell occurred about 3500 years ago.

## Abstract

We present the highest resolution single-dish submillimetre observations of the detached shell source U Antliae to date. The observations were obtained at $450~\micron$ and $850~\micron$ with SCUBA-2 instrument on the James Clerk Maxwell Telescope as part of the Nearby Evolved Stars Survey. The emission at $850~\micron$ peaks at $40\arcsec$ with hints of a second peak seen at $\sim 20\arcsec$. The emission can be traced out to a radius of $56\arcsec$ at a $3\sigma$ level. The outer peak observed at $850~\micron$ aligns well with the peak observed at Herschel/PACS wavelengths. With the help of spectral energy distribution fitting and radiative transfer calculations of multiple-shell models for the circumstellar envelope, we explore the various shell structures and the variation of grain sizes along the in the circumstellar envelope. We determine a total shell dust mass of $(2.0 \pm 0.3) \times 10^{-5}$ M$_{\odot}$ and established that the thermal pulse which gave rise to the detached shell occurred 3500 $\pm$ 500 years ago.