The nearby evolved stars survey - I. JCMT/SCUBA-2 submillimetre detection of the detached shell of U Antliae

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 and 850 μm with SCUBA-2 instrument on the James ClerkMaxwell Telescope as part of the Nearby Evolved Stars Survey. The emission at 850 μm peaks at 40 arcsec with hints of a second peak seen at ∼20 arcsec. The emission can be traced out to a radius of 56 arcsec at a 3σ level. The outer peak observed at 850 μm 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 ± 0.3) × 10-5 M and established that the thermal pulse that gave rise to the detached shell occurred 3500 ± 500 yr ago.