ALMA observations of the "fresh" carbon-rich AGB star TX Piscium The discovery of an elliptical detached shell
Journal article, 2019

Aims. The carbon-rich asymptotic giant branch (AGB) star TX Piscium (TX Psc) has been observed multiple times during multiple epochs and at different wavelengths and resolutions, showing a complex molecular CO line profile and a ring-like structure in thermal dust emission. We investigate the molecular counterpart in high resolution, aiming to resolve the ring-like structure and identify its origin. Methods. Atacama Large Millimeter/submillimeter Array (ALMA) observations have been carried out to map the circumstellar envelope (CSE) of TX Psc in CO(2-1) emission and investigate the counterpart to the ring-like dust structure. Results. We report the detection of a thin, irregular, and elliptical detached molecular shell around TX Psc, which coincides with the dust emission. This is the first discovery of a non-spherically symmetric detached shell, raising questions about the shaping of detached shells. Conclusions. We investigate possible shaping mechanisms for elliptical detached shells and find that in the case of TX Psc, stellar rotation of 2 km s(-1) can lead to a non-uniform mass-loss rate and velocity distribution from stellar pole to equator, recreating the elliptical CSE. We discuss the possible scenarios for increased stellar momentum, enabling the rotation rates needed to reproduce the ellipticity of our observations, and come to the conclusion that momentum transfer of an orbiting object with the mass of a brown dwarf would be sufficient.

stars: mass-loss

stars: AGB and post-AGB

stars: late-type

stars: carbon

stars: evolution


M. Brunner

University of Vienna

M. Mecina

University of Vienna

Matthias Maercker

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

E. A. Dorfi

University of Vienna

F. Kerschbaum

University of Vienna

Hans Olofsson

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

G. Rau

Catholic University of America

NASA Goddard Space Flight Center

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 621 A50

Subject Categories

Astronomy, Astrophysics and Cosmology

Atom and Molecular Physics and Optics

Fusion, Plasma and Space Physics



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