G19B003

VLBI observations of two AGB binary systems: R Aqr and Mira

Abstract

Binary/multiple stellar systems are as abundant as single stars. They are very interesting
cosmic laboratories as they are related to many astrophysical phenomena. In the case of
AGB (and post-AGB) stars, binaries are the most likely explanation for the shaping of non
spherical PNe, a long standing problem in stellar evolution. While many binaries are known in
the PNe phase, there are few examples in the previous AGB phase. Hydrodynamical models
of the binary interaction are available, but well known parameters for orbits are non-existent.
We propose to observe two binaries with an AGB primary, Mira and R Aqr, at 7mm using the
Global VLBI array in wide-band continuum and SiO masers. The strong SiO masers will be
used to self-calibrate the observations and pinpoint the location of the AGB component. The
continuum will be used to directly detect the WD companion (or companions in the case of
Mira; very probably a triple system) or its close environments (non-thermal emission from
accretion disks/jets). If successful, this proposal will open a new way to determine orbits in
binaries at the AGB phase and better study their role in late stellar evolution and PNe
shaping.

Investigators

Name	Institution
Francisco Colomer	Instituto Geográfico Nacional
Pere Planesas	Instituto Geográfico Nacional
Miguel Gomez-Garrido	Instituto Geográfico Nacional; Yebes, Centro Astronómico de
Valentin Bujarrabal	Instituto Geográfico Nacional
Jean-Francois Desmurs	Instituto Geográfico Nacional
Javier Alcolea *	Instituto Geográfico Nacional
GBT Operator	Green Bank Observatory

* indicates the PI