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DEATHSTAR: Nearby AGB stars with the Atacama Compact Array II. CO envelope sizes and asymmetries: The S-type stars by Andriantsaralaza, M.; Ramstedt, S.; Vlemmings, W. H. T.; Danilovich, T.; De Beck, E.; Groenewegen, M. A. T.; Höfner, S.; Kerschbaum, F.; Khouri, T.; Lindqvist, M.; Maercker, M.; Olofsson, H.; Quintana-Lacaci, G.; Saberi, M.; Sahai, R.; Zijlstra, A. is a scholarly article available to read on EtoBox.

What is DEATHSTAR: Nearby AGB stars with the Atacama Compact Array II. CO envelope sizes and asymmetries: The S-type stars about?

We aim to constrain the sizes of the CO circumstellar envelopes (CSEs) of 16 S-type stars, along with an additional 7 and 4 CSEs of C-type and M-type AGB stars, respectively. We map the emission from the CO J=2-1 and 3-2 lines observed with the Atacama Compact Array (ACA) and its total power (TP) antennas, and fit with a Gaussian distribution in the uv- and image planes for ACA-only and TP observations, respectively. The major axis of the fitted Gaussian for the CO(2-1) line data gives a first estimate of the size of the CO-line-emitting CSE. We investigate possible signs of deviation from spherical symmetry by analysing the line profiles, the results from visibility fitting, and by investigating the deconvolved images. The sizes of the CO-line-emitting CSEs of low-mass-loss-rate (low-MLR) S-stars fall between the sizes of the CSEs of C-stars, which are larger, and those of M-stars, which are smaller, as expected because of the differences in their respective CO abundances. The sizes of the low-MLR S-type stars show no dependence on circumstellar density, while a steeper density dependence is observed at high MLR. Furthermore, our results show that the CO CSEs of most of the S-star

Author

Andriantsaralaza, M.; Ramstedt, S.; Vlemmings, W. H. T.; Danilovich, T.; De Beck, E.; Groenewegen, M. A. T.; Höfner, S.; Kerschbaum, F.; Khouri, T.; Lindqvist, M.; Maercker, M.; Olofsson, H.; Quintana-Lacaci, G.; Saberi, M.; Sahai, R.; Zijlstra, A.

Published

2021

Language

EN