Anomalous water masers in OH/IR stars.
Abstract
The authors present OH (1612 MHz) and H2O (22.2 GHz) maser observations made with the VLA at an angular resolution of ≡1″toward three OH/IR stars: OH 12.8-0.9, OH 37.1-0.8 and OH 42.3-0.1. These stars exhibit the H2O maser components in a velocity range that exceeds the OH velocity range, a situation in disagreement with the standard model for maser emission in late-type stars. The authors find that the OH and H2O maser positions agree within ≡0″5 and that most likely both masers arise from the same source, ruling out the possibility of a fortuitous superposition of two different sources. The authors discuss some of the possible mechanisms that could explain the anomalous H2O maser emission. The most likely explanation is that these stars have axisymmetric winds and that the H2O emission originates in the polar regions with larger velocities than the regions closer to the equator where the OH emission arises. Very long baseline observations are required to test this explanation.
- Publication:
-
Revista Mexicana de Astronomia y Astrofisica
- Pub Date:
- April 1994
- Bibcode:
- 1994RMxAA..28...97G
- Keywords:
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- OH-IR Stars: Water Masers;
- OH-IR Stars: Stellar Winds