Studies of Hot Subdwarf Stars in Binary Systems

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Dr. Richard Wade will carry out a program of multi-epoch radial velocity observations of subdwarf B stars in binaries to establish whether their orbits are as predicted by theory. Subdwarf B stars are luminous, hot, evolved stars which are undergoing nuclear fusion of helium in their cores. Stellar evolution theory and recent observations suggest that many subdwarf B stars were formed in interacting binary systems. Those systems for which radial velocity variations are found will be followed to determine full orbits; conversely, if many systems show no detectable acceleration at a low measurement threshold, then this class of binaries cannot have interacted to form the subdwarf B star.The observations will be carried out at the Hobby-Eberly Telescope and at national facilities. This work will provide fundamental data that can be used to put the theory of binary star interactions and the origin of subdwarf B stars on a firmer basis. A better understanding of the ages and mass ranges of stars that can become subdwarf B stars is important in interpreting the ultraviolet light from galaxies at large lookback times. The work will help to validate, challenge, and ultimately improve binary population synthesis models that are used to predict or understand a wide variety of phenomena in modern astrophysics. The project will employ and train students to carry out a large portion of the research tasks. A new series of frequent and regular evening public talks will be initiated. This will provide a pathway for informal science education to help maintain a scientifically literate populace.