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Research Interests

My research is focused on active galactic nuclei (AGN), which are the bright centers of galaxies that host actively accreting supermassive black holes (SMBHs). My research is generally focused on connecting their accretion disks to the relativistic jets they can produce. 

One of my research focuses is blazars, which are a type of AGN that emits a high energy jet almost directly at Earth, with Dr. Alan Marscher and the Blazar Research Group at Boston University.  Blazar's radiation, which is prominent across the entire electromagnetic spectrum, exhibits violent variability in brightness. Bright 'knots' appear to move at superluminal speeds down blazar jets, an illusion caused by the jet orientation combined with near-light flow speeds. Supermassive black holes are thought to be the 'central engines' that produce the jets. Using the Very Long Baseline Array (VLBA), a technique that combines radio antennas to create an effective USA-sized telescope, I make high resolution images of blazar jets to probe them on size scales as small as one light-year. I am currently analyzing VLBA data of ten blazars to probe the jet shape and magnetic field in these sources.

Working with Dr. Laura Brenneman and Dr. Jonathan McDowell at the Smithsonian Astrophysical Observatory, I am developing a model of X-ray eclipses of AGN accretion disks. Eclipsing events of the central X-ray source in AGN has been found to be relatively common in several AGN. By developing this model, we can characterize the details of black hole accretion disks as a function of position in the disk.

I studied the AGN NGC 4151 using X-ray spectroscopy with NuSTAR and Suzaku working with Dr. Laura Brenneman.  The primary goal of this work was characterizing the properties of AGN accretion disk corona, absorbers, and the spin of the supermassive black hole. Supermassive black hole spin can be deduced if highly-broadened reflection features from the inner accretion disk are present in the AGN X-ray spectrum. Through disentangling the emission from the inner accretion disk from the X-ray emission from the AGN, we measured a near-maximal spin for the SMBH as allowed by general relativity.


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First Author Papers

"NuSTAR and Suzaku X-ray Spectroscopy of NGC 4151: Evidence for Reflection from the Inner Accretion Disk," M.L. Keck, L.W. Brenneman, et al., ApJ, (2015), http://adsabs.harvard.edu/abs/2015ApJ...806..149K

Co-Author Papers

"On Estimating the High-energy Cutoff in the X-Ray Spectra of Black Holes via Reflection Spectroscopy," J.A. García, T. Dauser, J.F. Steiner, J.E. McClintock, M.L. Keck, J. Wilms, ApJL, (2015), http://adsabs.harvard.edu/abs/2015ApJ...808L..37G    
"Gamma-Ray Energies in the Decay of 38Cl," K.S. Krane, M.L. Keck, E.B. Norman, and A.P. Shivprasad, Applied Radiation and Isotopes, (2011),  doi:10.1016/j.apradiso.2011.12.033