BHI Colloquium


Tuesday, March 30, 2021, 1:30pm


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Ruth Daly (Astronomy) - Penn State University

Title: Black Hole Spin and Accretion Disk Properties obtained with a New Method for 750+ Sources

Abstract: Four types of black hole system will be discussed including stellar-mass and supermassive black holes. All of the black hole systems are active and have powerful collimated outflows. Empirically determined relationships between the outflow beam power, accretion disk luminosity, and black hole mass indicate that the outflows are spin powered. The general equation that describes a spin powered outflow is rewritten in dimensionless separable form allowing a determination of the black hole spin. Accretion disk properties such as the disk magnetic field strength and mass accretion rate can also be determined for each source. Good agreement is found between spin values obtained with the new method and published values obtained with well-established methods. The spin values obtained range from about (0.4 - 1), and are found to be independent of source type. Accretion disk magnetic field strengths for the three AGN samples have similar distributions and mean values of about 10 kG, while those for stellar-mass GBHs have mean values of about 100 MG. The new method is independent of a specific accretion disk model; thus the results can be applied to study and constrain disk models.

Bio: Ruth Daly received her PhD in Astronomy & Physics at Boston University. She currently serves as a Professor of Physics at Pennsylvania State University Berks campus. Her research interests include black hole physics, extragalactic astrophysics, and cosmology.


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See also: Astronomy