The most fundamental piece of information about a star is its mass. Most commonly, stellar mass determinations are carried out for orbiting double stars. In this research project, the Principle Investigator is continuing the development of a general binary star model computer code that has, over recent decades, changed the way eclipsing binaries are analyzed. The Wilson-Devinny model code originated the now standard practice of finding close binary parameters impersonally, introduced simultaneous solutions of several kinds, allowed for direct determination of photometric mass ratios for the binary components, and was designed from the beginning to be very general, applying to a wide variety of binaries. The model can be made to synthesize fluorescent stellar winds and atmospheres, polarizing stellar surfaces, polarizing circumstellar structures, X-ray pulse arrival times, full spectral energy distributions, and other phenomena, while continuing to reproduce all binary star features that have been found useful by several hundred users in many countries. The code now is being used by many groups to establish distances to nearby galaxies, and continues to be used to investigate stellar evolution via binaries, including discovery and study of compact objects (white dwarfs, neutron stars, black holes).
Broader impact: The binary star computer model of this project has been shared with the community for over 20 years and thus has a long history of broad impact and a record of a very large number of literature citations. Many collaborations were formed in the U.S. and abroad to exploit the model during that time. The large number of publications by the various groups have had a major impact on the binary star field and related fields such as stellar structure, stellar evolution and recently the cosmic distance scale. Work with the code has influenced associates and students to enter stellar astrophysics, including the binary star field. The Principle Investigator works with public school students, and finds them appreciative of the image-making features in the code and the way that the documentation encourages personal interaction in dealing with real data.
