M dwarf stars, which are smaller, dimmer, and redder than our Sun, are the most common type of star in our galaxy. Like our Sun, these stars exhibit activity due to inherently strong magnetic fields at their surfaces. In M dwarfs, this activity is often classified by the emission line strength of the first transition of the hydrogen Balmer series (H alpha). We examine a sample of five equal-mass M dwarf wide binaries; these “twin” stars should have nearly identical stellar properties and therefore have very similar spectral features. We hypothesize that these stars should exhibit nearly identical properties in H alpha. If our hypothesis proves false, it means there are unexpected dynamics present in the binary system. In initial observations to classify these objects, we found that the M dwarfs in each binary, which were twins in every other way, showed very different levels of H alpha emission. To examine the range of H alpha line strengths we obtained a time series of optical spectra using the Astrophysical Research Consortium’s 3.5-meter telescope at Apache Point Observatory in New Mexico. In each binary, the slightly less massive star exhibits stronger mean H alpha, consistent with large survey results. Using data from 70 hours over 14 nights, we determined our stars have a characteristic variability timescale of around 2 hours; indicating our sample is active on shorter timescales than the typical rotational period.

When massive stars reach the end of their lives, they erupt in enormous explosions known as supernovae, leaving behind clouds of shocked gas and dust known as supernova remnants (SNR). The primary technique to measure the mass of the progenitor star requires waiting for the star to explode and examining pre-explosion Hubble Space Telescope archival images of the site, which may or may not exist. This technique is constrained by rarity of supernovae, and as such only ~25 progenitors have any mass constraint whatsoever in the literature. We employ an alternative technique in which we examine color-magnitude diagrams of the regions surrounding known supernovae to measure their star formation history. We then use this star formation history to assign an age to the progenitor star.  By employing stellar evolution models, we convert this age to a mass. Because we do not rely on identification of the specific progenitor star in the images, we are free to apply our technique to cataloged SNR, drastically increasing the number of available targets. We apply our method to ~135 cataloged remnants in the nearby spiral galaxies M31 and M33, representing a dramatic increase in the number of currently known masses. We examine the distribution of these derived masses and comment on implications for supernova physics.

Exoplanets are planets outside our solar system. As they do not emit light of their own, these objects have historically been much harder to find and study than stars. One detection method exploits the slight dimming of a star caused by a planet passing across its face. In astronomy, these events are termed transits, and they cause distinct u-shaped dips in the lightcurve—a plot of observed brightness versus time—of their host star. In recent years, the Kepler Space Telescope has provided lightcurve data on a fixed group of stars that is unprecedented in precision. Our research is primarily concerned with searching released Kepler data for previously undiscovered exoplanets. Due to the vast quantity of information, we have developed a pipeline of computer code to expedite the search process. The code, written in python, detrends variations in quiescent star brightness to normalize each lightcurve around a fixed, flat value. This readies the data for input to a Quasi-Periodic Automated Transit Search algorithm (QATS). Thus far, we have identified a handful of planet candidates as well as a number of undocumented binary star systems. Current and future tasks involve automating QATS output classification to further improve the efficiency of the planet finding process.

In the search for habitable planets, density is crucial in allowing us to determine whether a planet is terrestrial or gaseous. We developed a method of measuring the flux from a star during a planetary transit to constrain the density and the mass of the planet. This method depends on our ability to detect a moon in the transit and chart minor fluctuations in moon velocity and moon position with respect to the planet. To determine the precision with which we can measure the density of a planet, we have created a model which produces a synthetic light curve from which we can attempt to extrapolate planet parameters. However, we have found that the accuracy of planet density calculations is highly dependent on the signal to noise ratio of the sample due to the fact that moons have very small signals. We explore methods with which to detect moon signals to improve upon our ability to determine the density. It may still be necessary to combine our efforts with other methods, such as spectra analysis of Doppler shifts, to confidently differentiate potential life-bearing planets from those which are not habitable.

The initial mass distribution for exoplanet systems, prior to the onset of planet-planet scattering, has yet to be adequately constrained. Scattering has previously explained a broad range of observed properties, such as large eccentricities, packing, and mean-motion resonances, and hence is a promising theory. We present the results of numerical simulations of scattering-produced multiple planet systems arising from different initial power law mass distributions. We explore which of these power law distributions most accurately reproduces the observed mass distribution, thereby constraining the initial mass function.

 Galaxy formation theories call for all galaxies to be embedded in massive extended dark matter halos. Ideally, we would use thousands to millions of tracer particles to map the dynamical environment around galaxies to constrain the properties of dark matter. Reality limits us to using only the dynamical tracers that are luminous enough to actually be observed. The spiral galaxy NGC 4258 has numerous small galaxies surrounding it that appear to be satellite galaxies, and can therefore be used as dynamical tracers. To determine if these smaller galaxies are indeed satellites, we examine their redshifts by combining spectroscopic observations from the APO 3.5-meter telescope with SDSS spectra. Of the 33 observed objects, 22 appear to be members of the system. Using the projected line-of-sight velocities of the satellite galaxies and a Jeans equation approximation, we estimate the mass of NGC 4258 out to a radius of 260kpc to be 6x10¹² solar masses with an error of 50%. When utilizing a more rigorous set of criteria to determine which candidate galaxies are actually satellites, we are left with only 8 true satellites and derive a new mass to be 1.3x10¹² solar masses out to a radius of 230kpc. Further observations are expected to yield around 20 to 40 more satellite velocity measurements, which will improve our mass estimate and significantly reduce our error. By searching the SDSS database, we believe we can find other galaxy systems that host enough satellites to repeat this technique.