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Paper: Mapping 12CO J =21 and 10 Line Emission in CSEs around AGB and Early Post-AGB Stars
Volume: 378, Why Galaxies Care About AGB Stars: Their Importance as Actors and Probes
Page: 199
Authors: Castro-Carrizo, A.; Neri, R.; Winters, J.M.; Grewing, M.; Lucas, R.; Bujarrabal, V.; Quintana-Lacaci, G.; Alcolea, J.; Schoeier, F. L.; Olofsson, H.; Lindqvist, M.
Abstract: A systematic study of circumstellar envelopes around evolved stars is currently being carried out with the IRAM Plateau de Bure interferometer and the Pico Veleta 30-m telescope. We are mapping the CSEs for a sample of 36 AGB and 9 early post-AGB stars, at angular scales down to 1″, using 12CO J = 21 (230 GHz) and 10 (115 GHz) line emission. The sample stars have been selected to represent a large variety regarding their main stellar parameters such as variability, initial mass and photospheric chemistry. Our first results show an astoundingly large diversity of circumstellar characteristics. The (approximate) circular symmetry and smoothness observed in the brightness distribution of some CSEs (e.g. V Cyg) contrasts with the various axisymmetric distributions observed in other sources (e.g. RX Boo, IRAS 21282+5050, and V Hya) in their innermost CSE regions and/or in their overall envelopes. With the help of radiative transfer models we are determining the main properties of these CSEs: their mass-loss history, geometry, velocity field, degree of clumpiness, photodissociation radius, etc. We find that fluctuations in the AGB mass-loss process may regularly take place on time scales of ~ 102 yr.
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