504 citations · 2.7k across the 41 of their papers we have counts for
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Apparent motion of a spherical shell collapsing onto a black hole
Robert F. Penna
We model the collapse of a spherically symmetric, constant density, pressureless shell onto a preexisting black hole. Contrary to a recent claim of Liu and Zhang (2009), we show th…
Thin Disk Theory with a Non-Zero Torque Boundary Condition and Comparisons with Simulations
Robert F. Penna, Aleksander Sadowski, Jonathan C. McKinney
We present an analytical solution for thin disk accretion onto a Kerr black hole that extends the standard Novikov-Thorne alpha-disk in three ways: (i) it incorporates nonzero stre…
Measuring Black Hole Spin by the Continuum-Fitting Method: Effect of Deviations from the Novikov-Thorne Disc Model
Akshay K. Kulkarni, Robert F. Penna, Roman V. Shcherbakov +7
The X-ray spectra of accretion discs of eight stellar-mass black holes have been analyzed to date using the thermal continuum fitting method, and the spectral fits have been used t…
Measuring the Spins of Accreting Black Holes
Jeffrey E. McClintock, Ramesh Narayan, Shane W. Davis +6
A typical galaxy is thought to contain tens of millions of stellar-mass black holes, the collapsed remnants of once massive stars, and a single nuclear supermassive black hole. Bot…