Active Galactic Nuclei:
Image Credit: NASA & M. Weiss
Active galaxies are interesting because their central supermassive black holes are actively accreting material, emitting an immense amount of electromagnetic radiation. While up to several solar masses per year may be falling into the central black hole, recent evidence in some galaxies show that several orders of magnitude more can be flowing outward. The current goal of my research is to characterize the mass outflow rates in a sample of the galaxies to search for scaling relationships and other physical connections. My most recent publication on mass outflows can be found here: https://arxiv.org/abs/1809.09105
Image: Revalski et al. 2014
While active galaxies are accreting mass onto their super massive black holes, the rate of accretion is often not constant. Because of this, the amount of radiation released near the black hole can vary on timescales of minutes to years. Probing the variability time scales of active galaxies helps us learn about the size and geometry of the accretion disk, the possible presence of relativistic jets, and provides one of the most extreme places in the universe to test our models of high energy physics. The above image is from my paper in which our group used Kepler data to search for short time scale variations in four active galaxies. We combined nearly three years of data with thirty minute sampling to produce the longest light curves to date with such rapid cadences.
Below is a recording of my talk on Active Galaxy Mass Outflows at the New Jersey Astronomical Association Public Monthly Meeting, in November 2015.
Image Credit: NASA/ESA
Gravitational waves are ripples in space that convey the changing gravitational potential of a system. When interacting with a system of particles, they will cause oscillations of the particles for the duration of the wave's passage, leaving them with a permanent displacement once the wave has passed. This permanent displacement is known as the "memory effect" and manifests at linear and nonlinear orders in post-newtonian expansions. I am interesting in the physical connection between the interaction of gravitational waves with charged particles, and whether or not the memory effect could lead to attenuation of gravitational waves.
Image Credit: NASA
As binary systems orbit, they lose orbital energy through the emission of gravitational waves. The closer the pair is, the more rapidly they lose energy. This causes the binary to inspiral and eventually merge. Close binary systems have been the best indirect evidence of gravitational waves, and I am interested in the white dwarf binary J0651, which has an extremely short orbital period of only 12.75 minutes. This system is also eclipsing, and the cumulative change in eclipse time agrees with predictions of a changing orbit due to the emission of gravitational waves. I am interested in continued monitoring of this system to probe for cumulative nonlinear effects known as gravitational wave "tails", which are produced when the gravitational waves "bounce" off of the static gravitational potential and can alter the eclipse timing at a smaller level.
Below is a recording of my talk on Gravitational Waves at the New Jersey Astronomical Association Research Meeting, June 2014. My talk begins at 17:20 in the video.