This research focuses on the SiO maser emissions from long period/Mira variable stars. The maser radiation originates within several stellar radii of the surface and can be used as a probe of the physical characteristics of these outer regions and of the dynamics of the star. The maser pumping mechanism itself is still the subject of debate with both collisions and radiation being suggested. Moreover, the variability seen among maser emissions from Miras may be the result of shocks passing through the extended atmospheres of these stars. The goal of this project is to allow the continuation of an ongoing observational program using the remote observing capabilities of the Haystack Radio Astronomical Observatory in Massachusetts to follow the maser emissions of Miras. The result will be an SiO maser data set of approximately six years duration with high phase coverage and velocity resolution for the stars Mira and R Cas. The data will provide the basis for an improved understanding of the SiO maser pumping mechanism and the dynamics of the circumstellar region in which the masers originate. The extended duration of the observations is important to reduce the effects of random variations that occur during individual phase cycles in maser locations and velocities. A second goal is to complete a re-survey of stars previously observed in 1983. Comparisons between these and new measurements will be made to statistically describe the variations in the velocity centroid over time. Large shifts in the velocity centroid may indicate the presence of a binary partner. Stars discovered to have large shifts will be monitored in a search for the orbital parameters of the system. Finally, the orbital parameters of at least two SiO maser sources, R Aql and Mira, will be determined using published and archive data along with new observations of the maser emission as a velocity probe. Undergraduates will be trained through direct involvement in the data acquisition, analysis, and interpretation. Students will further be expected to co-author and present their results in publications and conferences. The work will also be included in a variety of undergraduate courses as an example of astronomical concepts, data analysis, the quantum mechanics of maser emission, the physical parameters of the circumstellar environments that generate SiO masers, and binary stars. Moreover, the research proposed here is expected to considerably enhance the research climate at the University of Minnesota Morris and in a physics department recognized for a traditionally high fraction of women graduates.
