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Department Library

2020

Ian Clark (Senior Thesis, April 2020, Advisor: Denise Stephens )

Abstract

In this paper, we present observations of ZZ Psc secured with the 0.4-meter OPO and 0.9-meter WMO telescopes at BYU and augmented with data from the AAVSO to search for previously unknown periods for ZZ Psc and verify those that have already been determined. We found what could possibly be a previously undiscovered period at 901 seconds. We found that many pulsation modes change in amplitude over the timescales of about a year. To find stabilities in these periods, we used O-C techniques. We found that nearly all these periods remained constant in observations with Johnson B, V, and clear filters.

John-Michael Eberhard (Senior Thesis, April 2020, Advisor: Denise Stephens )

Abstract

Brown dwarf binary systems provide key insights into the formation and evolution of brown dwarfs. To discover more binary systems, brown dwarf atmospheric models were fitted to the observed spectra of several brown dwarf systems. Spectral data for the systems was retrieved from the SpeX Spectral Library, the InfraRed Telescope Facility Library and the InfraRed Spectral Archive. The collected models predicted the spectrum a singular brown dwarf would have based on its temperature, surface gravity, cloud density, and amount of convection in the atmosphere. Binary models were created from the singular models and all of the models were compared to the observed spectra. Using a chi-squared analysis, the goodness of fit was calculated for each model. The best binary and singular fits were compared, and statistical analysis was performed to determine at what level of confidence each system could be claimed as binary. Twenty-six systems were studied and seven were found to be binary at a 99% confidence level: 2MASS 05591914-1404488, SDSS J042348.57-041403.5, 2MASSW J0320284-044636, 2MASS 14313097+1436539, DENIS-P J225210.73-173013.4, 2MASS 20282035+0052265, and SDSS J141624.08+134826.7. The method proved to be effective and can be used to more efficiently discover brown dwarf systems.

2019

Elisabeth Frischknecht (Senior Thesis, April 2019, Advisor: Denise Stephens )

Abstract

Herbig Ae/Be (HAeBe) stars are classified as 2-10 solar mass pre-main sequence stars with protoplanetary disks. As a result, they are excellent candidates for observing exoplanets in the formative stages of their evolution. By constructing and then subtracting a model Point Spread Function from object frames, an image of the protoplanetary disk and any planets located within it is obtained. This technique was used to analyze archival Hubble Space Telescope images of HAeBe object HD100546, which is known to host at least one planet (HD100546b) that has been detected at near-infrared wavelengths by other telescopes. The supposed detection of HD100546b is likely a false positive, but it is possible that the planet is still located within the data and may be detectable upon further research.

Alex Spencer (Senior Thesis, April 2019, Advisor: Denise Stephens )

Abstract

Information gained from analyzing exoplanets should answer questions about planetary and solar system formation. At Brigham Young University, the existence of exoplanets are confirmed using the transit detection method. However, information about these objects of interest are shrouded by the telescope’s inherent noise. In order to analyze the desired information, noise reduction procedures must be applied manually through command-line methods. This reduction process is slow and tedious, causing the sought-after data to often go untouched for long periods of time. To circumvent this, a program—called the pipeline—was further developed to perform these procedures automatically. The pipeline calls C-style script files to complete each action automatically, analyzing and responding to the discrepancies in each data set. The pipeline performs noise reduction quickly, consistently, and reliably. When compared to student researchers performing reduction tasks manually, the pipeline displays improvements in the processed data. Most importantly, the pipeline allows student researchers more time to focus on analyzing results or to work on other projects.

2018

Emily Welch (Senior Thesis, August 2018, Advisor: Denise Stephens )

Abstract

Brown dwarfs form like stars but are not massive enough to fuse hydrogen fusion in the core. They from between 0.013 M⊙ and 0.072 M⊙ and are difficult to detect because of their low luminosities. Brown dwarfs act as point sources that when imaged spread out their light on the CCD in predictable patterns. These patterns are known as point spread functions (PSF). It is because of this “spreading” that brown dwarf binaries are unresolved when there is small angular separation. Kyle Matt has produced a python script that uses PSF models to determine binarity for unresolved brown dwarfs. I have tested this code and have found some problems in comparing the single and binary fits, but have used the metric of flux percentage from the script output to suggest probable binaries.

2017

Leanne Farnbach (Senior Thesis, April 2017, Advisor: Denise Stephens )

Abstract

Brown dwarf binary systems are typically too small and cold to be visually resolved, making the study of their spectral features the next best method to determine the general nature of these particu- lar systems. I obtained data from the Spitzer Heritage Archive in the near to mid-infrared spectrum for several brown dwarf binary candidates. Using a least-squares approach and over a thousand synthetic spectral models, I performed a statistical analysis to determine which models best fit the original data. From these models, I determined the most likely parameter values for each com- ponent of either the single or binary system which include the temperature, surface gravity, cloud density, and the amount of atmospheric convection for each star. A binary system, or combination of two models, was found to better fit the following dwarfs: Kelu-1, 2MASSW J0036159+182110, 2MASSW J2224438-015852, SDSS J080531.83+481233.1, SDSS J105213.51+442255.7AB, and 2MASS J05591914-1404488. Kelu-1 and SD1052 are visually confirmed binary systems. The results of the statistical fitting match the known temperatures of each component for both stars, implying that this is a reliable method. The next step will be to identify and perform the statistical spectral analysis on additional brown dwarf binary candidates.

Kyle Matt (Senior Thesis, April 2017, Advisor: Denise Stephens )

Abstract

A Brown Dwarf is a celestial object that forms like a star, but is not massive enough to undergo hydrogen fusion in its core. Due to a lack of an internal energy source, brown dwarf temperatures are not stable with age, making mass and age estimates difficult. Recent evidence suggests that models of brown dwarf evolution are inaccurate; to improve these models, direct mass measurements are required. One of the best methods to empirically measure mass is through observations of the orbital parameters of a binary pair. Angular separation between binary brown dwarfs is often small enough that they are unresolved in images. Due to the great distances from Earth, these brown dwarfs appear as point sources of light and spread out in images in a predictable pattern, due to diffraction, known as the point spread function (PSF). I have developed a Python script based on an older FORTRAN program to find binary systems which are unresolved by creating models of PSFs and testing those models against images taken from the Hubble Space Telescope archive.

Andrew Patterson (Senior Thesis, April 2017, Advisor: Denise Stephens )

Abstract

Transiting planets can be discovered through the method of photometry. The Kilodegree Extremely Little Telescope (KELT) Transit Survey team is a collaborative effort to discover more transiting planets. Image Reduction and Analysis Facility (IRAF) has been used to create a script to efficiently pipeline the night sky's raw images into processed ones to prepare them for photometric measurements. The details to the structure and reliability of the data reduction script are outlined. The photometric results are sent back to the KELT team. Discussion of the significance of the light curve is also detailed.

Emily Diane Safsten (Masters Thesis, August 2017, Advisor: Denise Stephens )

Abstract

Herbig Ae/Be (HAeBe) stars are intermediate mass (2-10 solar mass) pre-main sequence stars with circumstellar disks. Observing planets within these young disks would greatly aid in understanding planet formation processes and timescales particularly around massive stars. So far, only one planet, HD 100546 b, has been confirmed to orbit a HAeBe star. With over 250 HAeBe stars known, and several observed to have disks with structures thought to be related to planet formation, it seems likely that there are as yet undiscovered planetary companions within the circumstellar disks of some of these young stars. Direct detection of a low-luminosity companion near a star requires high contrast imaging, often with the use of a coronagraph, and the subtraction of the central star's point spread function (PSF). Several processing algorithms have been developed in recent years to improve PSF subtraction and enhance the signal-to-noise of sources close to the star. However, many HAeBe stars were observed via direct imaging before these algorithms came out. We used the PSF subtraction program PynPoint to reprocess archival images of HAeBe stars from the Advanced Camera for Surveys on the Hubble Space Telescope to increase the likelihood of detecting a planet in their disks. We believe we have recovered the known planet around HD 100546 and possibly its candidate second companion. We also detect new candidate sources in the vicinities of HD 141569 and HD 163296. Further observations are needed to confirm the reality of these detections and also establish their association with the host stars.

2015

Ben Fischer (Senior Thesis, December 2015, Advisor: Denise Stephens )

Abstract

The Kilodegree Extremely Little Telescope (KELT) program is exactly what the name suggests a small telescope that observes a large field of view. Operating since 2005 KELT has been gathering data on thousands of stars with the purpose of discovering transiting planets. KELT generally observes stars with magnitudes of approximately 10 and looks for variations in flux. The KELT team catalogs all candidates for transiting stars. Since there are many possible causes for drop in flux it is necessary to make follow-up observations on exoplanet candidates. Using information from the KELT catalog we decided on several possible target stars. Observations of the stars were done to gain more data to analyze. Using the newly gathered data we created light curves for each star. We also analyze this data to determine the cause of the drop in flux. We explain how to do this process in a way to allow others to continue this work.

Clement Gaillard (Senior Thesis, December 2015, Advisor: Denise Stephens )

Abstract

As the Kepler space telescope searched for transiting Earth-like planets, it observed thousands of stars, including a large collection of M-dwarfs. M-dwarfs are stars that are smaller, cooler and fainter than our Sun. Finding transiting planets around an M-dwarf is difficult because of the low signal-to-noise observations made by the Kepler mission for these specific stars. Using PyKE, a Python-based package developed by the NASA Kepler Guest Observer Office, we can minimize the noise introduced by the star and its neighbors to produce cleaner light curves for the fainter M-dwarfs. With this package we were able to produce light curves for 113 M-dwarfs in the Kepler database. We analyzed this data and detected transiting planet candidates. We present our methodology and analysis for one transiting planet candidate that we discovered.

Doug Gardner (Senior Thesis, August 2015, Advisor: Denise Stephens )

Abstract

The inability to resolve close stars due to the Rayleigh criterion complicates the search for closely orbiting binary brown dwarf systems. We have developed a Fortran computer program that uses point spread function fitting on Hubble archive data to find binary systems at separations that are visually unresolvable. To test the performance of this program under the full range of param- eters (brightness, separation, position angle, background noise), we have created and analyzed six hundred thousand simulated binary data sets. The results from this test suggest that our program should be able to successfully identify binary systems at separations of less than a pixel. In par- ticular, we can place limits of around 90 percent certainty that the brown dwarf star BD0559 is actually a binary system with a separation of 0.035 arcsec.

Elora Salway (Senior Thesis, April 2015, Advisor: Denise Stephens )

Abstract

The Hubble Space Telescope (HST) has observed a fair number of brown dwarfs which, in ground based images, appear to be single objects. Frequently, however, the higher angular resolution of HST reveals that some of these objects are binary systems. The small angular separation of these binaries hints that there may be many more unresolved binary brown dwarfs observed with HST. With Point-Spread Function (PSF) fitting, it is possible to identify binary brown dwarf candidates in the HST archives which are not visually resolved according to the Rayleigh criterion. By fitting a double PSF to each brown dwarf image in each filter and camera for which data exists, we can determine a range of fluxes for both components of the binary system. These fluxes will be used to constrain theoretical spectrum of brown dwarfs to the original data to find a range of temperature and gravity for both objects. This thesis presents the results of PSF fitting for the brown dwarf 2M 0559, which reveals the object to be a strong binary candidate.

Katrina Wright (Senior Thesis, April 2015, Advisor: Denise Stephens )

Abstract

Brown dwarf spectra may be the result of binary systems. Because of this, two models must be combined and the models must be rebinned to the spectra to perform a best fit. Previous work has been in a less useful language and less general. This thesis describes the process of making code in C++ which can be used to fit any spectrum to the models.

2014

Brigitte Stewart (Senior Thesis, December 2014, Advisor: Denise Stephens )

Abstract

The equatorial region of Saturn's moon Titan has five large sand seas with dunes similar to large linear dunes on Earth. Cassini Synthetic Aperture Radar (SAR) swaths have high enough resolution to measure dune parameters such as width and spacing, which helps inform us about formation conditions of the sand dunes. Previous measurements in locations scattered across Titan have revealed an average width of 1.3 km and spacing of 2.7 km, with variations by location. We are particularly interested in how these variations are affected by sand availability. This information could help us determine more accurately how much sand is in different regions of Titan, and how sand is transported between regions. We have taken over 1200 new measurements of dune width and spacing in the T8 swath, a region on the leading hemisphere of Titan in the Belet Sand Sea, between -5 and -9 degrees latitude. We have also taken over 900 measurements in the T44 swath, located on the anti-Saturn hemisphere in the Shangri-La Sand Sea, between 0 and 20 degrees latitude. We correlated each group of fifty measurements with the average distance from the edge of the dune field to obtain an estimate of how position within a dune field affects dune parameters. We found that in general, the width and spacing of dunes decrease with increasing distance of the dunes from the edge of the dune field, consistent with similar measurements in Australian sand seas on Earth. This correlation is likely due to the decrease of sand availability at the edges of dune fields. We suggest that in this particular case, the Australian sand seas may provide a better analogy for Titan than the Namib Sand Sea in Africa.

Emily Stoker (Senior Thesis, June 2014, Advisor: Denise Stephens )

Abstract

An unanticipated result of researching transiting planet candidates from the Kepler spacecraft mission was the discovery of several variable objects in the fields of some of the targets. One particular object, which it was determined had not been previously documented, had a light curve that indicated it was a contact eclipsing binary star system. We found that this object has a period of about 0.3462 days. We worked to find a model that best fit our observed data of this system. Our results indicate that the two stellar components have similar temperatures, one around 6240 Kelvin, and the other is about 110-130 K warmer. The mass ratio is about 4.5, and the system is nearly edge-on relative to the plane of the sky. We emphasize the inconclusive nature of our results as other models may also be valid and more data is needed to confirm the binary nature of this system.

2013

Tess Larson (Senior Thesis, August 2013, Advisor: Denise Stephens )

Abstract

The exoplanet research group at BYU has been observing and reducing data taken of objects on the Kepler planetary candidate list. We observed KOI667.01 at West Mountain Observatory (WMO) and realized that it was a false positive. Because the field we were interested in was very crowded we could not use aperture photometry to analyze the data. We used DAOPHOT in order to reduce the data and compute accurate light curves. We were able to determine which object within our crowded field was the eclipsing binary.

Emily Ranquist (Senior Thesis, August 2013, Advisor: Denise Stephens )

Abstract

Magnitudes are the quantitative measurements of a star’s brightness. By analyzing a plot of the magnitude over time, known as a light curve, one can detect objects with fluctuating light output, such as variable stars, eclipsing binaries, and stars with transiting planets. To obtain magnitudes, we must go through a time consuming process called photometry on multiple images for every star we wish to plot. Through the use of the command language and scripting tools in NOAO’s Image Reduction and Analysis Facility (IRAF), we have been able to develop a program called brightER that greatly reduces the amount of time spent on photometric procedures. BrightER is a compilation of multiple scripts, each designed to automate a specific part of the process. Using this program, we have been able to reproduce light curves in less than an hour that originally took days to create. The ease and efficiency of brightER allows us to focus less on data acquisition and more on the results.

2012

Nathaniel Cook (Senior Thesis, April 2012, Advisor: Denise Stephens, Darin Ragozzine )

Abstract

From our understanding of planet formation we know that many comets are created and ejected, but we have yet to observe "interstellar" comets from other stars. A detailed estimation of the population of these comets has been recently determined. Those results concluded that based on their size and distribution that the Large Synoptic Survey Telescope (LSST) would be unlikely to see any interstellar comets beyond 5 AU. Our work takes into account the gravitational focusing of the Sun and the brightening of comets as they come closer to the Sun. We will more accurately describe the probability of realistically observing these close interstellar comets. Using numerical simulations we track the comets in their hyperbolic orbits about the Sun. From this simulation we determine the rate of visible interstellar comets and the unique characteristics of their paths across the sky. We conclude that the LSST will be able to detect and identify interstellar comets.

Muxue Liu (Senior Thesis, April 2012, Advisor: Denise Stephens )

Abstract

On July 24th 2011, the Department of Physics and Astronomy of Brigham Young University observed the transiting exoplanet around object KOI1152, a Sun-like star imaged previously by NASA's Kepler telescope. After data reduction, clear light curves are obtained, which confirm the nature of the transiting object as a planet. The amount of magnitude decrease (~ 0.1 mag) agrees with the predicted value published by the Kepler team.

Joseph Rawlins (Senior Thesis, August 2012, Advisor: Denise Stephens )

Abstract

We have analyzed 80 trans-Neptunian objects (TNOs) observed with the near-infrared camera and multi-object spectrometer (NICMOS) aboard the Hubble Space Telescope (HST) and measured their (J - H) near-IR (NIR) magnitudes and colors. We used a model psf fitting process to obtain our results. While the (B - R) color of TNOs show a clear difference in color for objects with inclination angles < 6 degrees and those > 6 degrees, we find no such trends in the NIR (J - H) colors. Two of our objects are blue in the near-IR and have been identified with the Haumea collisional family. There are also hints of variability in (19255) 1999 VK8, 1999 OE4, 2000 CE105, 1998 KG62 and 1998 WX31.

2011

Tabitha Christi Buehler (PhD Dissertation, December 2011, Advisor: Denise Stephens )

Abstract

I have identified 51 young stellar object candidates in N206, an H II complex in the nearby Large Magellanic Cloud galaxy. Using archival images from the Spitzer Space Telescope, supplemented with other infrared and optical images, I located point sources in this region. I distinguished possible young stellar objects based on their spectral energy distributions, morphologies, and locations in color-magnitude space. I classified the young stellar object candidates based on their likelihood of being young stellar objects and based on their apparent evolutionary stages. The spatial distribution of these young stellar object candidates in N206 indicates that star formation is being triggered in a giant molecular cloud in the region.

Andrew DeWitt (Senior Thesis, August 2011, Advisor: Denise Stephens )

Abstract

Magnitude sensitivities and zero point values are presented for the Kodak KAF-09000 and Fairchild 3041-UV CCDs mounted on the 0.9m telescope at BYU's West Mountain Observatory. Sensitivities and zero points presented for the KAF-09000 and 3041-UV CCDs are given in the Johnson V, B, R, I and Johnson V, B, R filters, respectively. These values were calculated by performing aperture photometry on the open cluster NGC 188 and Landolt standard stars SA 110 using an aperture radius of 8 pixels. The sensitivities provide a starting point for determining exposure times to observe exoplanet candidates discovered by the NASA Kepler Mission and other stellar objects with short-term variability.

2010

Daniel R Allen (Masters Thesis, August 2010, Advisor: Denise Stephens )

Abstract

Cassini spacecraft images of Io obtained during its flyby of Jupiter in late 2000 and early 2001 were used to determine the lava composition and eruption style of three faint hotspots, Pillan, Wayland, and Loki. We found a maximum color temperature of 1130±289 K for Pillan and maximum color temperatures of 1297±289 K and 1387±287 K for Wayland and Loki, respectively. These temperatures are suggestive of basaltic lava. The temperatures with the best signal-to-noise ratios also suggested basaltic lava and were found to be 780±189 K, 1116±250 K, and 1017±177 K for Pillan, Wayland, and Loki, respectively. Pillan showed increased activity on the third eclipse day after being fairly constant for the first two days, suggesting increased fountaining or lava flow activity on the third day. The data also suggest that Pillan is surrounded by topography that blocked emission on day000 and caused a much more dramatic decrease in emission. Wayland’s intensity decreased over the three eclipses, consistent with a cooling lava flow or decreasing eruption. However, rapid decreases in intensity over periods of 26 to 48 minutes could have resulted from the eruption of highly exposed lava, perhaps an open channel or fountain. The data also suggest Wayland may be in a depression surrounded by ridges that blocked part of the emission. Intensities at Loki over the course of the observation varied in both directions, and were consistent with previous determinations of an often quiescent lava lake with periods of active overturning and fountains.

Taran Esplin (Senior Thesis, December 2010, Advisor: Denise Stephens )

Abstract

I present the results of a statistical modeling of the near to mid-infrared spectrum of the T4.5 brown dwarf 2MASS J05591914-1404488. The system is over-luminous and and suspected to be a possible unresolved binary but this has not been con firmed observationally. Using a least-squares approach the data is compared to 700,336 single and binary model spectra. I give results for a best single and binary t. A binary of an unequal mass and temperature (1300K and 1000K) is shown to be a statistically better t. The best t predicts cloud formation in the atmosphere of the 1000K secondary. Theoretical justification is given for the presence of clouds in a cool brown dwarf.