OH maser proper motions in Cepheus A.
Abstract
MERLIN measurements made between 1982 and 1989 reveal proper motions of OH masers in the source Cepheus A. The proper motions are typically a few milliarcsec per year, and are mainly directed away from the central H II regions. Statistical analysis of the data suggests an expansion time-scale of some 300 yr. The distance of the source implied by the proper motions is 320+140/-80 pc, assuming that the expansion is isotropic. The proper motions can be reconciled with the larger distance of 730 pc which is generally accepted, provided that the masers are moving at large angles to the line of sight. The expansion time-scale agrees with that of the magnetic field decay recently reported by Cohen, et al. (1990).
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 1992
- DOI:
- 10.1093/mnras/254.3.501
- Bibcode:
- 1992MNRAS.254..501M
- Keywords:
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- H Ii Regions;
- Hydroxyl Emission;
- Interstellar Masers;
- Cepheus Constellation;
- Emission Spectra;
- Interstellar Magnetic Fields;
- Molecular Clouds;
- Rangefinding;
- Very Long Base Interferometry;
- Astrophysics