First detection of methanol towards a post-AGB object, HD 101584

¹ Dept. of Space, Earth and Environment, Chalmers Univ. of Technology, Onsala Space Observatory, 43992 Onsala, Sweden
e-mail: hans.olofsson@chalmers.se
² ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
³ Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago de Chile, Chile
⁴ ESO, Alonso de Cordova 3107, Vitacura, Santiago, Chile
⁵ Dept. of Physics and Astronomy, Uppsala University, PO Box 516, 75120 Uppsala, Sweden

Received: 14 May 2017
Accepted: 19 June 2017

Abstract

The circumstellar environments of objects on the asymptotic giant branch and beyond are rich in molecular species. Nevertheless, methanol has never been detected in such an object, and is therefore often taken as a clear signpost for a young stellar object. However, we report the first detection of CH₃OH in a post-AGB object, HD 101584, using ALMA. Its emission, together with emissions from CO, SiO, SO, CS, and H₂CO, comes from two extreme velocity spots on either side of the object where a high-velocity outflow appears to interact with the surrounding medium. We have derived molecular abundances, and propose that the detected molecular species are the effect of a post-shock chemistry where circumstellar grains play a role. We further provide evidence that HD 101584 was a low-mass, M-type AGB star.