1. Most stars occur in systems containing two or more objects. Some pairs include a very dense star called a ?white dwarf? ? a star with the mass of our Sun crammed into a volume about the size of the Earth ? plus a red giant star hundreds of times larger than the Sun. In some cases, called ?symbiotic binaries,? the red giant can transfer matter onto the white dwarf. Such systems provide clues about the way the evolution of one star affects the other. They also provide clues about the types of stars that can explode as supernovae, completely disrupting the entire star. This project will use a robotic telescope called ?SkyMapper? in Australia to search the southern skies for large numbers of symbiotic binaries that previous surveys may have missed. It will also involve large numbers of amateur astronomers around the world who are members of the American Association of Variable Star Observers. Their observations will help professional astronomers to determine the true numbers of these systems in the Milky Way Galaxy.
2. Symbiotic stars are binary systems in which a white dwarf accretes matter from a red-giant companion. Understanding these systems may have far-reaching implications for binary stellar evolution and may help to constrain the fraction of SNIa that originate as symbiotics. Arguing that an important, and possibly dominant, sub-population of such systems may have been missed in previous surveys, the Principal Investigator will mine the data provided by the SkyMapper Southern Sky Survey based at the Siding Spring Observatory in Australia to determine the true population of symbiotic binaries in the Galaxy. The Intellectual Merit of the proposed research stems from the potential for discovering large numbers of previously unknown symbiotics, from determining the true population of such systems in the Galaxy, and from the potential impact of these discoveries on our understanding of binary evolution and the origins of Type Ia supernovae. The project will also help to prepare the astronomical community to deal with the flood of data expected from the Large Synoptic Survey Telescope (LSST) when it comes into operation early in the next decade. The project also has unique Broader Impacts: It will foster a close collaboration between the large number of amateur astronomers around the world who are members of the American Association of Variable Star Observers (AAVSO) and professional astronomers to support current and future wide-field time-domain surveys, including those involving the LSST.