Magnetically Supported Accretion Disks Around Black Holes: Observational Diagnostics from Numerical Simulations

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Greg Salvesen is awarded an NSF Astronomy and Astrophysics Postdoctoral Fellowship to carry out a program of research and education at the University of California, Santa Barbara. Salvesen will perform advanced numerical simulations to understand how strong magnetic fields influence black hole X-ray Binaries (BH XRBs), which consist of a black hole feeding on a disk of X-ray emitting gas from a companion star. Understanding BH XRBs is key to learning about other types of black holes as well. The center of nearly every galaxy (including our own) hosts a supermassive black hole surrounded by a disk of gas, but supermassive black holes are very difficult to understand because they change very little over our lifetimes. Because BH XRBs are thought to be scaled down versions of supermassive black holes, and exhibit changes on timescales accessible to astronomers, they are ideal laboratories for studying how material accretes around a black hole. Alongside this work, Salvesen will create a website featuring real astronomical data that have been converted into sound samples, and he will develop workshops to convey classroom astronomy concepts through sound to K-12 students with visual impairments or limited English proficiency.Salvesen will undertake numerical simulations of strongly magnetized accretion disks to calculate two direct observable quantities of BH XRBs: (1) the spectrum of light emitted by an accretion disk subjected to magnetic fields of various strengths and geometries, as well as quasi-periodic oscillations produced by accretion disk variability; and (2) the spectrum of light absorbed by magnetically driven disk winds, and manifested in diagnostic probes (e.g., spectral lines of highly ionized atoms). Salvesen will then compare the simulations with the observed properties of BH-XRBs to determine if the emission and absorption spectra of these objects can be used to understand the influence of strong magnetic fields on black hole accretion disks. Salvesen will also create the Astronomy Sound of the Month (ASOM) website and develop "sonification" workshops to convey basic astronomy concepts to visually impaired or English-language learning K-12 students.