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Masers: Probing the mass loss process in PPN

Published online by Cambridge University Press:  25 May 2016

Dieter Engels
Dieter Engels*
Affiliation:
Hamburger Sternwarte, Gojenbergsweg 112, D–21029 Hamburg

Extract

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With the advent of the IRAS All-Sky Survey a sizeable number of transition objects between the AGB and the PN-phase were found - the Proto Planetary Nebulae (PPN). Oxygen-rich AGB stars often show prominent masers of SiO, H2O, and OH, which are lost during the transition process. The heavy mass loss on the AGB however does not stop abruptly and a new axisymmetric wind develops during the PPN phase. These winds both may host new masers and they can be used to study the changes of the mass loss process after that the stars have stopped their large-amplitude variations on the AGB. Several PPN are known to have OH masers, and at least in one case, HD 101584, the presence of a bipolar outflow could be proven (te Lintel Hekkert et al. 1992). Lewis (1989) found that main-line OH masers become prominent again. I will discuss here conclusions, which can be drawn from observations of H2O masers in PPN.

Type
V. From AGB to Planetary Nebulae
Information
Symposium - International Astronomical Union , Volume 180: Planetary Nebulae , 1997 , pp. 348 - 349
Copyright
Copyright © Kluwer 1997 

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