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
. 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
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
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.
First Author Papers
and Suzaku X-ray Spectroscopy of NGC 4151: Evidence for Reflection from the
Inner Accretion Disk
, L.W. Brenneman, et al., ApJ, (2015), http://adsabs.harvard.edu/abs/2015ApJ...806..149K
"On Estimating the High-energy Cutoff in the X-Ray Spectra of Black Holes via Reflection Spectroscopy," J.A.
, T. Dauser, J.F. Steiner, J.E. McClintock, M.L.
, 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.
, E.B. Norman, and A.P. Shivprasad, Applied Radiation and
Isotopes, (2011), doi:10.1016/j.apradiso.2011.12.033