In Search of Black Hole Spin

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AST-0607428ReynoldsDramatic advances in both accretion disk theory and X-ray observations have rekindled interest in the near-environment of black holes and the astrophysical effects of black hole spin. Simulations are beginning to address complex magnetized plasma interactions and relativistic frame-dragging effects, while observationally, there is increasing agreement that some X-ray emission occurs very close to the accreting black hole, precisely where spin effects are prominent. However, there are problems with all three of the principal ways to measure black hole spin from X-ray data, which are spectral modeling of the iron emission line or of the thermal accretion disk emission, and modeling of high-frequency quasi-periodic oscillations (QPOs). This project will lay the theoretical foundations for extracting black hole spin from X-ray observations, by studying the dynamics, thermodynamics and observable signatures of the inner accretion flow, by directly connecting QPOs with the theory of turbulent accretion disks, and by studying the magnetic heating of accretion disk coronae and its effect on X-ray spectra. Processes associated with black hole spin can have dramatic astrophysical consequences, such as the formation, acceleration and collimation of powerful relativistic jets. This work is an important step towards reliably and accurately measuring that spin, in at least a subset of systems.Since black holes grip the imagination like no other astronomical object, this study is well suited for engaging a wide spectrum of the community and of the public. Regional and national outreach efforts will expand, through public talks and through enhancement of an already popular web site. In addition to including results in the investigators' formal teaching, graduate and undergraduate students will directly participate in the research.