A&A Supplement series, Vol. 127, January II 1998, 185-200
Received February 28, 1996; accepted May 5, 1997
L.-Å. Nyman
, P.J. Hall
, and H. Olofsson
Send offprint request: L.-Å. Nyman (ESO address)
ESO/La Silla, Casilla
19001, Santiago 19, Chile
Onsala Space Observatory, S-439 92 Onsala,
Sweden
Australia Telescope National Facility, PO Box 76, Epping, NSW
2121, Australia
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
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