A Polarization Survey of SiO Maser Variability in Evolved Stars

Abstract

We have monitored the SiO (v = 1, J = 2 -> 1) maser polarization in 17 variable stars (Miras, OH-IR stars, and supergiants) to investigate the long-term persistence of masers. The 8 epochs of observations span 2.5 years, thereby sampling multiple cycles for these stars with typical periods of ~1 year. The average polarization was 23% with a typical dispersion of 7%, although the variability differed substantially from star to star. In the Stokes q and u spectra of individual stars, a few strong maser features tended to dominate the polarization, with the maser features persisting for less than one stellar cycle for some stars, and for multiple cycles for a few stars. Because individual masers are not resolved in our beam-averaged total intensity spectra, we correlated the polarization spectra between epochs to measure the characteristic lifetimes of the features rather than attempting to trace the evolution of separate line components. We found that individual maser feature lifetimes ranged from a few months or less to >2 years. These data indicate that for the sample of stars as a whole, the masers are not reset at a particular stellar phase.

arXiv comment35 pages with 24 figures included

References in corpus (2)

• Numerical simulations of stellar SiO maser variability. Investigation of the effect of shocks
• Testing the clump model of SiO maser emission

Cited by in corpus (7)

• Full polarization study of SiO masers at 86 GHz
• The variability of Sagittarius A* at 3 millimeter
• Simultaneous VLBA polarimetric observations of the v=$\{$1,2$\}$ J=1-0 and v=1, J=2-1 SiO maser emission toward VY CMa II: component-level polarization analysis
• Precessing planetary magnetospheres in SiO stars ? First detection of quasi-periodic polarization fluctuations in R Leo and V Cam
• Mapping circumstellar magnetic fields of late-type evolved stars with the Goldreich-Kylafis effect: CARMA observations at $\lambda 1.3$ mm of R Crt and R Leo
• Circular polarization measurement in millimeter-wavelength spectral-line VLBI observations
• The modulation of SiO maser polarization by Jovian planets