Stokes polarimetry of main-line OH emission from stellar masers

Journal Article · Wed Dec 01 04:00:00 EST 1982 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/160490· OSTI ID:5577738

Claussen, M J; Fix, J D

Main-line OH emission has been measured in all four Stokes parameters from seven late-type variable stars and the F8 supergiant IRC+10420. Linearly polarized features were detected in UX Cyg, U Ori, and IRC+10420 at 1665 MHz. The linearly polarized features in UX Cyg and IRC +10420, when combined with adjacent circularly polarized features suggest Zeeman patterns. A polarization pattern in IRC+10420 is probably the best example of a complete Zeeman pattern yet observed in stellar masers, although it appears to lack the shifted linear (sigma) components. This study, combined with other recent work, shows that linearly polarized features in stellar sources are uncommon. Only about 10% of the stellar OH sources show linearly polarized features. As an aid in accounting for the observed polarization properties of stellar OH masers, model mass flows were calculated using magnetic field structures similar to that of the solar wind. Conclusions drawn from this model were: (1) unpolarized or weakly circularly polarized emission from sources can arise from the entire circumstellar shell; (2) circular polarization without linear polarization can be produced either by emission from the entire shell or by enhanced OH densities in small regions of the shell provided there are sufficient free electrons present to depolarize the linear components; and (3) Zeeman patterns which include both circular and linear polarizations can be produced in OH density enhancements if electron densities are low. The electron densities required for effective Faraday depolarization yield emission measures of the order of 10/sup 9/ pc cm/sup -6/. Given the large distances of stellar OH masers, the thermal continuum emission from such depolarizing electrons would probably be undetectable.

• Research Organization: Department of Physics and Astronomy, The University of Iowa
• OSTI ID: 5577738
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 263:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AMPLIFIERS
ATMOSPHERES
ELECTRON DENSITY
ELECTRONIC EQUIPMENT
EQUIPMENT
GIANT STARS
HYDROGEN COMPOUNDS
HYDROXIDES
MAGNETIC FIELDS
MASERS
MATHEMATICAL MODELS
MICROWAVE AMPLIFIERS
MICROWAVE EQUIPMENT
OXYGEN COMPOUNDS
POLARIZATION
SPECTRA
STAR MODELS
STARS
STELLAR ATMOSPHERES
STOKES PARAMETERS
SUPERGIANT STARS
VARIABLE STARS
ZEEMAN EFFECT