出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We have observed the OH 1612-MHz maser emission towards the proto-planetary nebula candidate
OH17.72.0 that underwent a very strong and unusual outburst in 2003. Phase-referencing
data were obtained with the EVN in order to localize the outburst and to examine its possible
causes. The majority of the emission comes from an incomplete spherical shell with inner and
outer radii of 220 and 850 mas, respectively. There is a strong evidence for maser components
that arise due to the interaction of a jet-like post-AGB outow with the remnant outer AGB shell.
The most prominent signature of such an interaction is the strongly bursting polarized emission
near 73.3kms1 coming from two unresolved components of brightness temperature up to 1011 K
located at the edge of the biconal region 2500AU from the central star. It is remarkable that this
OH biconal region is well-aligned with the polar outow inferred from the near-infrared image.
