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University of Nevada, Reno Automated Nightly Observations for the Long-Term Monitoring of KIC 8462852 a Thesis Submitted in Part

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University of Nevada, Reno Automated Nightly Observations for the Long-Term Monitoring of KIC 8462852 a Thesis Submitted in Part University of Nevada, Reno Automated Nightly Observations for the Long-Term Monitoring of KIC 8462852 A thesis submitted in partial fulfillment of the Requirements for the degree of Master of Science in Physics by Jacob M. Fausett Dr. Melodi Rodrigue/Thesis Advisor May, 2019 Copyright by Jacob M. Fausett 2019 All Rights Reserved THE GRADUATE SCHOOL We recommend that the thesis prepared under our supervision by JACOB MONROE FAUSETT Entitled Automated Nightly Observations for the Long-Term Monitoring of KIC 8462852 be accepted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Melodi Rodrigue, Ph.D., Advisor W. Patrick Arnott, Ph.D., Committee Member Mathew J. Tucker, Ph.D., Graduate School Representative David W. Zeh, Ph.D., Dean, Graduate School May, 2019 i Abstract The star KIC 8462852 has puzzled astronomers since its aperiodic fluctuations in brightness and long-term secular dimming were discovered in 2016. Based on that initial data from the Kepler mission, an international collaboration has sought to better understand these two phenomena. Over the past three years, a network of observatories has been monitoring the star nightly in order to see these fluctuations in real time and send alerts to the community for further observation. The research presented here is in an effort to contribute to the continuous monitoring of KIC 8462852 using the Great Basin Observatory. Nightly observations are scheduled with ACP Observatory Control Software and an automated pipeline, using Python’s Astropy and IRAF (Image Reduction and Analysis Facility) has been setup to process the images and perform photometry in order to quickly recognize a dimming event. Since March of 2018, our data show the largest such event since the initial Kepler data and is consistent with other observations during that time. It also confirms the chromatic nature of these events, suggesting that the material obstructing the stars light is optically thin. Additionally, the secular dimming has not been witnessed and conversely, the star has portrayed a slight rising trend over this period. ii ACKNOWLEDGMENTS First, I would like to thank my advisor, Dr. Melodi Rodrigue. She has supported and encouraged me throughout this entire process and gave me the confidence to do my research in a field that is not typically researched in our department but is a passion for both of us. Her door was always open when I had questions or concerns and she has been incredibly invested in my personal and professional development. I would also like to thank Dr. Paul Neil and the entire physics department at the University of Nevada, Reno for approving me to complete a thesis in astronomy and for their continued support throughout the process Additionally, I would like to thank Dr. Tabetha Boyajian from Louisiana State University and Dr. Jon Swift from the Thacher School in Ojai CA. Their support and mentorship throughout this process has been crucial to my success and growth within the field. I would not have been able to complete this work without their guidance and direction. Finally, I would like to thank my wife and children for their continued support of my education, research, and completion of this thesis. It has been a long and challenging journey, but their continued encouragement has provided me with the drive to pursue my passion. iii Table of Contents Page ABSTRACT i ACKNOWLEDGEMENTS ii TABLE OF CONTENTS iii LIST OF TABLES v LIST OF FIGURES vi CHAPTER 1 INTRODUCTION 1 1.1 The Kepler Mission 1 1.2 Where’s the Flux? 3 1.3 Post Kepler Dips 6 1.4 Great Basin Observatory 6 2 THEORY 8 2.1 Literature Review 8 2.2 Photometry 20 3 METHODS 25 3.1 Instrumentation 25 3.2 Image Processing 27 3.2 IRAF, DS9, and Reference Stars 30 3.3 Python Automated Pipeline 36 4 RESULTS 40 4.1 2018 Light Curve 40 iv 4.2 Evangeline 42 4.3 Long Term Behavior 45 4.4 Pipeline and Future Work 46 5 CONCLUSIONS 5.1 Summary 49 REFERENCES 50 APPENDECIES A IRAF 53 Installation 53 Configuration 55 Parameters 60 B Pipeline 65 Crontab 65 Tabby_API.bash 66 Tabby_API.py 66 Tabby_pipe.py 67 v List of Tables Table 1. Apparent magnitude for various astronomical objects 22 Table 2. Sample IRAF coordinate table 34 Table 3. Table of magnitude information produced by IRAF 34 Table 4. Reference star information from Bruce L. Gary 35 vi List of Figures Figure 1. Kepler Field of View 1 Figure 2. Transit Light Curves 2 Figure 3. Where’s the Flux Light Curves 4 Figure 4. Fourier Transform of Kepler Data 8 Figure 5. Variability found in Kepler Data 8 Figure 6. Possible Companion star 9 Figure 7. Keck Image with Companion Star 9 Figure 8. LCO 2017 Events 12 Figure 9. Elsie Mosaic 13 Figure 10. LCO Elsie Zoom 14 Figure 11. GTC Event Depth vs. Average Depth 16 Figure 12. GTC AAC vs. Particle Radius 16 Figure 13. Archive Century Secular Dimming 19 Figure 14. Kepler Secular Dimming 19 Figure 15. Sloan Filters Spectrum 25 Figure 16. Johnson-Cousins Filters Spectrum 26 Figure 17. Calibration Frames 28 Figure 18. Raw Science Image 29 Figure 19. Reduced Science Image 30 Figure 20. IRAF Radial Plot 31 Figure 21. IRAF 1-D Gaussian 32 Figure 22. Annulus and Check Stars Image 33 vii List of Figures Figure 23. Bruce L. Gary Star Finder 35 Figure 24. 2018 Reference Star Plot 36 Figure 25. GBO 2018 Light Curve 40 Figure 26. LCO 2018 r’ Light Curve 41 Figure 27. GBO 2018 r’ Light Curve 41 Figure 28. GBO Evangeline Zoom 42 Figure 29. LCO Caral_Supe and Evangeline 43 Figure 30. LCO All Post-Kepler Dips 43 Figure 31. Evangeline Egress 44 Figure 33. 2018 Trend (g’ and r’ filters) 45 Figure 33. 2018 Trend (i’ and V filters) 46 Figure 34. Extinction Plot 47 1 Introduction 3.4 – The Kepler Mission Before discussing KIC 8462852 in detail, it is important to talk about the mission that from which its peculiar behavior was discovered. The Kepler spacecraft was launched on March 7, 2009 with a mission to explore the structure and diversity of planetary systems in a specific region of our galaxy in order to estimate these qualities throughout the Milky Way (Johnson, 2015). The spacecraft targeted a single field of view (FOV) (figure 1) and continuously monitored nearly 156,000 stars in this field to detect planetary transits (when a planet passes in front of a star and blocks some of its light) (Borucki et al., 2011). At the time of writing this, 2338 planet discoveries by the Kepler mission have been confirmed (“Exoplanet Archive Planet Counts,” n.d.). Figure 1. Shows Kepler’s field of view (FOV); which, crosses between the Cygnus and Lyra constellations. Depicts the array of 50x25 mm CCDs with 2200x1024 pixels each (Johnson 2015). https://exoplanetarchive.ipac.caltech.edu/docs/counts_detail.html 2 These planetary discoveries were made by identifying small variations in a star’s intensity that occurred on a periodic basis (transits). These transits are generally verifiable as planets, since they exhibit a regular period based on the planet’s distance from the star, and the amount of light blocked (depth) is also constant. Typical examples of these light curves are shown in figure 2 below. Figure 2. This figure shows the first five plant discoveries made by the Kepler mission. It shows the depth of the light curves, the inclination of the planets orbit (how far from center), and the orbital period (Johnson 2015). The period is governed by Kepler’s third law 푎3 퐺(푀 + 푚) (1) = 푇2 4휋2 where 푎 is the ellipse semi-major axis, 푇 is the orbital period, 퐺 is the 푚3 gravitational constant (6.674 ∗ 10−11 ), 푚 is the mass of the planet, and 푀 is 푘푔∗푠2 the mass of the star (“Kepler’s Laws,” n.d.). Additionally, the size of the planet determines the amount the light curve dips during a transit. This is given by 3 2 푅푝 (2) 퐷푒푝푡ℎ = ( ) 푅푠 where 퐷푒푝푡ℎ is the percentage of light blocked, 푅푝 is the radius of the planet, and 푅푠 is the radius of the star (“Transit Light Curve Tutorial,” n.d.). The original Kepler mission came to an end in 2013, when a second reaction wheel failed, and the craft could no longer remain fixed on the original FOV. Over the four- year mission, the Kepler spacecraft is responsible for discovering 4770 possible exoplanets (“Exoplanet Archive Planet Counts,” n.d.). Approximately half of these are still yet to be confirmed (“Exoplanet Archive Planet Counts,” n.d.). 1.2 – Where’s the Flux? While most of Kepler’s discoveries were easily recognizable as exoplanet transits, the data for KIC 8462852 did not fit with any known theories. The behavior was so unusual that in January 2016, Dr. Tabetha Boyajian and the Planet Hunters project titled a paper “Where’s the flux?,” as a clever play on the acronym WTF (T. S. Boyajian et al., 2016). Figure 3 shows the Kepler data light curve; which highlights the aperiodicity of the dips in addition to their highly irregular depth (T. S. Boyajian et al., 2016). Based on our equation above, even the largest known planet (radius = 2*radius of Jupiter) orbiting the KIC 8462852 (radius = 1.4*radius of the sun) would only block 2.2% of the light (Siegel, 2015) (T. S. Boyajian et al., 2016). This is obviously much less than the roughly 22% dip that is seen in these plots, shortly after day 1500 of the mission. 4 Figure 3.
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