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.

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.

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.

 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.

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.

AB Aur is a protostar with a surrounding protoplanetary disk. By taking coronagraphic images of AB Aur using an occulting mask to block out the star in order to get a more detailed look at the young circumstellar disk we are able to analyze the potential formation of any extrasolar planets. Because it is unclear where the exact center of the star is behind the occulting mask, we simulated the effects of mis-centered stars by shifting 24 individual images of the disk 4 times at different pixel shifts. Using 14 areas of interest we were able to compare the intensity changes for each final shifted image. Any significant variations in the intensity graph indicated the region was not an actual structure. We concluded there was a spiral arm forming on the right side of the disk and the gap above the star was real and not strongly affected by any mis-centering of the central star behind the corongraphic mask.

A proto-planetary disk is a disk of gas and dust that surrounds a star that is still in the early stages of evolution. This disk contains the gas that accretes onto the proto-star and also contains the dust and gas from which planets form. Unfortunately the star is a much brighter than the disk and so direct imaging of the disk is difficult and time consuming, but can be accomplished using a coronagraph. To help interpret coronagraphic imagery of the protoplanetary disk system AB Aur, we created 3D models of the system using the Monte Carlo code of Whitney et al. 2002. We compared the observed the spectral energy distribution (SED) of the system, compiled from observed data reported by Robitaille et al. 2006, with predictions from our Monte Carlo model. An SED is a plot of the brightness versus wavelength of a star. We tested other variables like the composition of the disk, and the percentage of the disk that is composed of small grains and large grains, etc. We discuss how changing each of these variables influenced the resultant SED and model image of the AB Aur system; and hence influences our ability to study the process of planet formation around young stars.

Astronomers do not yet completely understand how galaxies evolve. Current leading theories propose that spiral galaxies merge and the result is an ultra-luminous infrared galaxy or ULIRG, which is a galaxy with an active galactic nuclei (AGN) that is obscured by warm dust and gas. After the ULIRG phase, it is thought that the galaxy becomes a quasar after a blowout stage occurs. The blowout stage is when the huge energy output from the accretion process of material falling into the central black hole expels the gas that was previously obscuring the central quasar. The blowout stage would be short-lived, however, and therefore difficult to directly observe, so evidence of this process is scarce. In order to study the blowout stage, we obtained 2-D K-band integral field data with SINFONI (Spectrograph for Integral Field Observations in the Near Infrared) on the Very Large Telescope for a sample of six quasars that are divided into pre- and post–blowout by comparing their ratios of infrared luminosity to the luminosity of the optical 'big blue bump’. We measured the spatial distribution and column density of the warm molecular gas but did not find the correlation of these quantities predicted by blowout models. To further explore the relationship between post- and pre-blowout galaxies, we fit the luminosity profiles of the molecular gas and compare this to the profiles of the stellar population which traces the gravitational potential.

Variable stars are stars that fluctuate in brightness over time, usually with sinusoidal patterns. We can plot the brightness of variables over time to create light curves, which allow us to examine the periodicity of the stars. SX Phe variables are a specific type of star that have not been extensively studied and classified. We examined seven SX Phe candidates in order to more precisely determine their light curves. The periods of the candidates had been roughly estimated with data from the LINEAR survey. The goal of this project was to determine these periods more precisely and to image the stars in multiple filters, which will tell us more about their properties. At the University of Washington Manastash Ridge Observatory (MRO), these seven candidate SX Phe stars were observed in the Sloan g’ and r’ filters over at least 1.5 periods. Photometric images of the candidates were obtained from these observations, and light curves were produced. It was determined that the majority of candidates have periods of variability of about 1.35 hours, almost half as long as previously hypothesized. Further analysis of these more accurate light curves is needed to classify the candidates as SX Phe stars.

Planetary Nebulae (PNe) are the final stages of stellar evolution for the majority of stars including our Sun. They consist of a very hot white dwarf surrounded by a shell of gas that was ejected from the progenitor star as it aged. The white dwarf produces ultra-violet photons that ionize the gas in the shell producing the bright structures that we see in images produced by the Hubble Space Telescope (HST). Classical models that predict the ionization structure of planetary nebulae generally assume constant gas density in the shell. The simple symmetry of the models allows them to adopt a 1-dimensional (1-D) geometry for the calculated ionization structure of the shell. Our HST images allow us to test these models. We obtained HST images using the light from ionized hydrogen (H⁺), doubly ionized oxygen (O⁺⁺) and singly ionized nitrogen (N⁺). We use H⁺ to find the full extent of the ionized nebula, O⁺⁺ to select one of the key ionization volumes within it, and N⁺ to study the region where the ionization state of the gas changes from fully ionized to neutral. From those images we generated ratios of N⁺/H⁺ and O^++/H⁺. These ratios are being used to test the veracity of and identify departures from theoretical models.

Seyfert galaxies are a type of galaxy that is part of a larger class called active galactic nuclei (AGN) in which the central supermassive black hole is accreting surrounding material. On large scales, Seyfert galaxies look identical to quiescent galaxies in which the supermassive black hole is inactive. However, on a smaller scale, around 10 – 10³ parsecs, we are now starting to detect differences in the molecular gas and stellar properties that can help us reach our goal of determining what the key differences are between the Seyfert galaxies and the quiescent galaxies and what results in the generation of an AGN. One of these differences could be star formation at the nucleus of the galaxy. To determine if this is a factor, we can use spatially resolved 2-D spectra to detect any Brackett Gamma (Brγ) emission within the central 10³ pc. For galaxies that have Brγ emission, we can measure the equivalent width of the Brγ line and, through comparison with stellar population evolution models, constrain the age of the stars. A potential complication with using the Brγ line is that there can be an additional broad component of the line generated by high velocity clouds very near the central black hole that is not associated with star formation. We minimize the impact of this broad component by fitting and removing it to isolate the narrow line emission of interest. The age can also be further constrained by estimating the supernova rate and the mass-to-light ratio. We have found that Brγ is significantly more prominent in Seyfert galaxies than in quiescent galaxies, suggesting that there is more active star formation in the nuclear region of Seyfert galaxies. Constraining the age of this stellar population will determine the role of these stars in fueling the central AGN in these galaxies.

A spherical domed ceiling has been a proven artistic space since the era of Antonio da Correggio’s famous dome fresco, The Assumption of the Virgin. Mix that together with the University of Washington’s planetarium and an extremely fertile space for artistic collaboration and exploration is revealed. Today, brand-new digital projection technology at University of Washington’s planetarium provides a unique space for digital artwork in comparison to more classical, non-digital domes. However, because of a planetarium’s contextual history, a significantly greater amount of time has been spent continuing planetarium-like experiences rather than attempting more artistic and experimental explorations. Over the past year, I have worked in collaboration with the Astronomy and DXARTS departments to create a fully immersive and experimental film for fulldome projection. Through research, development, and testing, I have also produced a robust framework for future artists to create their own works in fulldome spaces, especially at the University of Washington. As Correggio has shown, being creative with illusionistic perspective on a dome can lead to impressive results. Even in the 21st century, his techniques can be applied towards scientific and artistic experiences as well as open up other unique avenues of exploration within a fulldome space.

Stellar flares are the explosive release of energy caused by the reconnection of magnetic fields on stars. Flares release large amounts of UV and X-ray radiation, and may affect the possibility of life on exoplanets, planets orbiting stars other than our own Sun. A star's mass and age greatly affect the frequency, duration, and energy of flares. Therefore, it is important to understand these aspects for a variety of masses and ages. The age of a star is related to the rate of its rotation as well as the rate at which it flares; older stars spin much more slowly and also flare less frequently than younger stars. M dwarfs, stars less than half the mass of the Sun, are commonly used in stellar flare research because they make up the majority of stars in the Milky Way galaxy. To conduct our research, we used two months of data from the NASA Kepler spacecraft to study the light curves of one young and three old M dwarfs. We were able to identify flares in these light curves and measured their durations and energies. We found that the vast majority of flares on all four stars have a short rise time and a long decay time. We also found that flares with long durations have larger total energies, and that older stars have fewer large energy flares compared to younger stars. Through using the light curves, larger, more prominent flares were easily detectable in comparison to smaller flares. Further research would concentrate on more accurate ways toward detecting such small flares.

More than 50 percent of stars are found in binary systems. A cataclysmic variable star is a binary system consisting of a white dwarf and a larger, cooler star in an orbit with a period of only a few hours. These stars are so close that the white dwarf distorts the gravitational field of the other star and mass is transferred from the cool star to the white dwarf via an accretion disk. The defining characteristic of the type of cataclysmic variable called dwarf novae is that they irregularly increase and decrease in brightness. The increases (called outbursts) are caused by an instability in the accretion disk that causes an increase in accretion. After an outburst, these stars steadily decline in brightness until they return to their original state. However, the subgroup of dwarf novae called Z Cam systems sometimes become stuck in a state called a standstill, where they stay at a brightness near outburst level, and then decline to their original level. Using data taken at Kitt Peak National Observatory and Apache Point observatory over a series of five months, we were able to analyze spectra of two unusual objects as they go through their outbursts. We can find out what state they are in by comparing their spectra to light curves from the American Association of Variable Star Observers. What is unusual about these objects is that rather than fade to their original state after standstills, they go up to another outburst. Using these spectra, we hope to find the accretion rates of the stars at standstill, and then compare to other stars of the same type to better understand why they have this peculiar behavior.

Measurements of the rotation of galaxies indicate that visible matter cannot account for all of a galaxy's mass. The prevailing theory is that each galaxy is surrounded by a halo of dark matter. Dark matter halo mass can be determined by measuring the velocities of dwarf satellite galaxies orbiting a central galaxy. We used data from the Sloan Digital Sky Survey (SDSS) DR8 and HyperLeda databases to identify massive, isolated galaxies including M94, M101, and NGC 2841 and prioritize their satellites for observation. Next we will make spectrographic observations to determine satellite velocities and use these results to infer the mass of the central galaxy. By comparing this value to the amount of visible mass in the galaxy, we will determine the mass of the dark matter halo.