| 1. |
- Brunner, M., et al.
(author)
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ALMA observations of the "fresh" carbon-rich AGB star TX Piscium The discovery of an elliptical detached shell
- 2019
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 621
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Journal article (peer-reviewed)abstract
- 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.
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| 2. |
- Brunner, M., et al.
(author)
-
The discovery of an asymmetric detached shell around the "fresh" carbon AGB star TX Psc
- 2019
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In: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 14, s. 360-361
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Conference paper (peer-reviewed)abstract
- We present ALMA observations of the circumstellar envelope around the AGB carbon star TX Psc in molecular CO(2-1) emission, and detect a previously unknown detached shell with filamentary structure and elliptical shape. Up to now, all observed detached shells are found around carbon AGB stars and are of remarkable spherical symmetry. The elliptical shell around TX Psc is the first clear exception to that rule, with TX Psc being classified as rather "fresh" carbon star, that most likely has only experienced very few thermal pulses yet. We investigate and discuss the 3D structure of the CSE and its most likely formation scenarios, as well as the link of this peculiar detached shell to the AGB evolutionary status of TX Psc.
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