ALMA and VLTI: Evolved stars and Shaping to Planetary Nebulae
Thesis Supervisor: Liz Humphreys
The importance of binaries on stellar evolution has been recognized lately, but their effects on the close circumstellar environment is not yet known. The influence of a companion on the region near to the surface of Asymptotic Giant Branch (AGB) stars may play a pivotal role in the formation of aspherical Planetary Nebulae. SiO masers are usually found within the pulsating atmospheres of AGB stars at about 2 stellar radii, and trace the onset of stellar mass loss. Using ALMA long baseline science verification data, we have found for the first time that the SiO emission (both thermal and maser), can also trace binary wind interaction close to the star. In the case of Mira AB, the SiO emission traces a portion of a bubble wall formed by the interacting winds, within 10 stellar radii of Mira A. In this PhD project, have in hand ALMA Long Baseline data for 3 further binary systems containing an AGB star, and which have known SiO emission. The PhD project is to investigate whether SiO emission in other binary systems is linked to wind interaction and traces the shaping processes.
Collaboration with ESO and ALMA researchers, including VLTI researchers, will include: Markus Wittkowski (ESO Germany), Claudia Paladini (ESO Chile), Yoshi Akari (ALMA) and Luciano Cerrigone (ALMA).