Time variations of interstellar water masers: strong sources in H II regions.
Abstract
Summary. The strong water-line sources W3OH, Orion A, W49N and W5lS have been monitored over the period 1974 September-1976 October. Variations on a variety of timescales from years to days have been observed. W49 and W5 is exhibit more rapid variations than W3 OH or Orion A. A comparison of the present results with those of Sullivan during 1969-70 suggests that the flux from the main components of W49 has systematically decreased, whereas that from W5 1 has systematically increased in the 5-yr interval between the two sets of observations. This fact is best explained if there are changes in the flux of radiation from a common exciting object, incident on all of the masing components. High-velocity features in W49 have on two occasions been brighter than any of the main components, supporting a Doppler shift rather than scattering explanation for their origin.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- September 1977
- DOI:
- 10.1093/mnras/180.4.639
- Bibcode:
- 1977MNRAS.180..639L
- Keywords:
-
- H Ii Regions;
- Interstellar Masers;
- Water Masers;
- Cloud Physics;
- Hydrogen Ions;
- Interstellar Radiation;
- Radiation Pressure;
- Stellar Winds;
- Water Vapor;
- Astrophysics