Time variations in 18-cm OH emission profiles over the period 1965-1972

Details Time variations in 18-cm OH emission profiles over the period 1965-1972 Time variations in 18-cm OH emission profiles over the period 1965-1972

Sep 1976

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1976a%26a....51..427s&link_type=abstract

Astronomy and Astrophysics, vol. 51, no. 3, Sept. 1976, p. 427-450. Research supported by the University of Maryland and U.S. N

Astronomy and Astrophysics

Astronomy

14

Hydroxyl Emission, Infrared Stars, Line Spectra, Radio Astronomy, Time Dependence, Circular Polarization, Fine Structure, H Ii Regions, Line Shape, Radio Emission, Stellar Luminosity, Ultrahigh Frequencies

Scientific paper

Observations of emission profiles of the four ground-state OH transitions in 11 H II regions and two IR stars, most of which are also 1.35-cm H2O sources, are combined with all other relevant published data in order to study the detailed nature of time variations in the OH profiles of the sources. The results indicate that: (1) about 25% of the 145 velocity features studied are variable in total intensity on a time scale of approximately 5 years, (2) about 50% of the 31 profiles exhibiting emission contain a variable feature, (3) only about 10% of those features variable in total intensity are also variable in their percentage circular polarization, (4) variations in the amount of linear polarization are relatively more frequent, (5) the main-line variations typically have shorter time scales than the satellite-line variations, and (6) a greater percentage of the satellite-line features are variable. It is found that features of highest intrinsic luminosity in the H II regions are least likely to vary but are much more likely to display a small amount of circular polarization. In general, the characteristic scales of the observed time variations are shown not to place any significant constraints on the dimensions of the masing regions.

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