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2017 Vera Rubin Early Career Prize Winner - Daniel Fabrycky

The Division on Dynamical Astronomy awards the first Vera Rubin Early Career Award to Daniel Fabrycky of the University of Chicago for elegant applications of dynamical astronomy to fundamental puzzles in the physical and orbital properties of binary stars and extrasolar planets.

Dr. Fabrycky received his PhD from Princeton in 2007 under the direction of Scott Tremaine. His thesis work dealt with three cases of the three-body problem in which the bodies are not point masses. In one of the studies, he investigated why most close binaries are members of triple systems, with the third star in a much larger orbit than the binary. Fabrycky showed that in systems in which the orbits of the inner and outer binary are nearly perpendicular, the distant companion excites the eccentricity of the inner binary through the Kozai mechanism. The eccentricity is then damped by tidal friction. The period distribution of inner binaries produced by Kozai cycles and tidal friction shows a peak near 3 days, consistent with the measured period distribution of inner binaries in hierarchical systems. He also applied this mechanism to form hot Jupiters in wide binaries, predicting the distribution of orbital misalignments with respect to the host star spin. This calculation was influential in motivating and interpreting observations of this fundamental parameter of exoplanetary architectures.

Dr. Fabrycky is probably best known for his work on the Kepler mission. Kepler has discovered more than 500 systems of two or more planets. Because of the gravitational interactions between those planets, the times at which a transit occurs are not exactly periodic. Fabrycky has been a leader in interpreting these transit timing variations. Kepler-11 was the first system for which the masses of the planets could be derived from transit timing. Kepler-11 has six planets transiting a Sun-like star, the inner five of which are sub-Neptunes with orbits smaller than that of the planet Mercury. A more recently discovered planetary system is Kepler-223, which has four planets in three-body resonances like that among Jupiter's Galilean satellites. Fabrycky and his colleagues showed that this configuration probably arose through migration in a gas disk. Fabrycky's unique perspective was invaluable for an Annual Reviews article co-authored with Joshua Winn on the geometry of exoplanetary systems. His generosity with his time and his ideas, especially with regard to mentoring students and junior colleagues, is exemplary. Fabrycky will deliver an invited lecture at the 2018 DDA Annual Meeting to be held in San Jose California.