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A&A Supplement series, Vol. 127, January II 1998, 185-200

Received February 28, 1996; accepted May 5, 1997

SiO masers in OH/IR stars, proto-planetary and planetary nebulaegif

L.-Å. Nymantex2html_wrap1858, P.J. Halltex2html_wrap1860, and H. Olofssontex2html_wrap1862

Send offprint request: L.-Å. Nyman (ESO address)

tex2html_wrap1864  ESO/La Silla, Casilla 19001, Santiago 19, Chile
tex2html_wrap1866  Onsala Space Observatory, S-439 92 Onsala, Sweden
tex2html_wrap1868  Australia Telescope National Facility, PO Box 76, Epping, NSW 2121, Australia
tex2html_wrap1870  Stockholm Observatory, S-133 36 Saltsjöbaden, Sweden


We present a search for SiO masers towards a sample of 126 objects including OH/IR stars, proto-planetary and planetary nebulae. All objects are classified as oxygen-rich, and most of them are associated with OH or tex2html_wrap_inline1844 masers. SiO masers were found only in variable objects like the OH/IR stars and a few objects classified as proto-planetary nebulae, but with variable central stars that may be part of binary systems. In one object, OH 15.7+0.8, which appears to be varying irregularly and most likely recently left the AGB, an SiO maser was tentatively detected. Thus, we conclude that variability and SiO maser emission are closely linked, and that SiO masers disappear very soon after a star has reached the end of the AGB, when pulsation and mass loss cease.

keywords: stars: AGB and post-AGB -- masers -- radio lines: stars

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