Fundamental Stellar Parameters from the CHARA Array

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).In this project, Dr. Harold McAlister will continue research in stellar properties using the technique of interferometry. Georgia State University's Center for High Angular Resolution Astronomy (CHARA) operates an optical/near infrared interferometric array on Mount Wilson, California. The CHARA Array has six 1-m aperture telescopes in a Y configuration providing 15 baselines from 33 to 331 meters. In terms of the number and size of its telescopes, the length of its baselines, the broad range of wavelength regimes and spectral resolutions covered by its beam combiners, its imaging capabilities, and broad group of collaborators and users, the CHARA Array is among the most powerful facilities of its type and is unique in the world.Previous publications from CHARA data include: measuring the oblateness and other physical parameters (including gravity darkening) for the rapidly rotating stars Regulus, Alderamin and Vega; detecting the inner-most regions of Vega's circumstellar disk; discovering that cool, low-mass stars of solar composition are larger in diameter for a given mass than lower metal abundance stars of the same mass, suggesting the presence of additional opacity sources not accounted for by current models; measuring the angular separation between the components of the binary star 12 Persei to an accuracy 0.05% of the separation, which significantly improves the accuracy of the masses for the component stars; K band measurements of the angular dimensions of circumstellar disks; a measurement of the diameter of the transiting exoplanet HD 189733b; imaging the surface of the rapidly rotating star Altair, the first time this has been done for a dwarf apart from the Sun.Two newly commissioned beam combiners will leverage the Array's limiting resolution by extending the operating regime from the near IR to the visible region of the spectrum while providing high spectral resolution and improved sensitivity. Broader impact beyond the scientific and intellectual goals exists in three areas. First, CHARA is actively training the next generation of scientific and technical experts in the field of interferometry. A significant fraction of astronomy graduate students at Georgia State University are pursuing their PhD research with the Array. CHARA staff members have participated in many of the NASA/JPL Michelson Summer Schools, and CHARA has published on its website ninety-four Technical Reports available to the international community. Second, CHARA is enhancing science awareness in the large and diverse undergraduate community by incorporating results from the Array in undergraduate astronomy courses, which enroll approximately 700 students per semester. Third, CHARA actively participates in informal science education through such efforts as the collaboration with the American Museum of Natural History as well as through CHARA's own Exhibit Hall located in the CHARA Operations Center on Mount Wilson.