• Abstract and Figures
• Public Full-text

Copyright by Kevin Carl Gullikson 2016 The Dissertation Committee for Kevin Carl Gullikson certifies that this is the approved version of the following dissertation: Spectroscopic Detection and Characterization of Extreme Flux-Ratio Binary Systems Committee: Adam Kraus, Supervisor Sarah Dodson-Robinson Daniel T. Jaffe Edward L. Robinson Michael Meyer Spectroscopic Detection and Characterization of Extreme Flux-Ratio Binary Systems by Kevin Carl Gullikson, B.S; M.A. Dissertation Presented to the Faculty of the Graduate School of The University of Texas at Austin in Partial Fulfillment of the Requirements for the degree of Doctor of Philosophy The University of Texas at Austin May, 2016 Dedicated to my loving parents, who encouraged my exploration of science from an early age. Acknowledgements I would like to start by thanking everyone who served as a supervisor during part of my thesis. Mike Endl served as my co-supervisor for two years, taught me how to observe on the 2.7m telescope at McDonald observatory, and involved me in the planet search program for the last 5 years. That experience provided many interesting nights, a fun "side project", and gave me the confidence to do much of the observing for my main survey program. Sally Dodson-Robinson served as my thesis supervisor for my first two years. She gave me a great deal of independence in my project, while providing valuable feedback. I would like to thank both her and my current supervisor, Adam Kraus, for nominating me for several UT fellowships and funding me as a research assistant during much of my graduate career. The freedom to work exclusively on research has been invaluable, and facilitated much of the progress that I made. Adam, thank you for being a great advisor. Despite being brand new at this, you provide a great mix of a hands-on style when I need it and hands-off when I don't, and have been nothing but supportive in every way. I would also like to thank Rob Robinson, my committee member, for numerous discussions on statistical methods both while planning and analyzing the results of my survey program. Discussions with you, not to mention your excellent data analysis class, have really helped me to think of statistical methods in a way that makes sense. Finally, I would like to thank all of my friends and colleagues at UT for making these last years so much fun. From the usual crowd at Crown to cookouts at Paul's to boat parties and volleyball with Tom Montemayor, I have rarely lacked for a way to blow off some steam and relax in between the stressful moments. And of course, I would like to thank my girlfriend Cori Norman. You have made the last three years absolutely wonderful. v Spectroscopic Detection and Characterization of Extreme Flux-Ratio Binary Systems Kevin Carl Gullikson, Ph.D. The University of Texas at Austin, 2016 Supervisor: Adam Kraus Binary stars and higher-order multiple systems are a ubiquitous outcome of star formation, especially as the system mass increases. The companion mass-ratio distri- bution is a unique probe into the conditions of the collapsing cloud core and circum- stellar disk(s) of the binary fragments. Inside a ∼ 1000 AU the disks from the two forming stars can interact, and additionally companions can form directly through disk fragmentation. We might therefore expect the mass-ratio distribution of close companions to differ from that of wide companions. This prediction is difficult to test with intermediate-mass primary stars using traditional methods because the contrast ratios that would be required to detect low-mass companions at narrow working an- gles are not yet achievable. In this thesis, we present a spectroscopic method to detect and characterize close companions to a variety of stars. We demonstrate ap- plications of the method to detection of stars and even planets around sun-like stars, and present the results of a survey searching for companions to A- and B-type stars. As part of the survey, we estimate the temperatures and surface gravity of most of the 341 sample stars, and derive their masses and ages. We additionally estimate the temperatures and masses of the 64 companions we find, 23 of which are new detec- tions. We find that the mass-ratio distribution for our sample has a turnover near q ≈ 0:3, in contrast to the scale-free power law that describes the widely separated binary systems. We take this characteristic scale as evidence that companions are accreting a significant of material through disk interactions as they form, and that the scale is largely set by the disk lifetime and the time at which the fragments form. vi Contents List of Figures . x Chapter One: Introduction . 1 Binary Star Formation . 1 Other Implications of Binarity . 2 Detection Methods . 3 Previous Observational Results . 5 Chapter Two: Direct Spectral Detection: An Efficient Method to Detect and Characterize Binary Systems . 8 Background . 8 Direct Spectral Detection Method . 9 Observations and Data Reduction . 11 Parameter Determination . 15 Detection Sensitivity . 16 Application to Known Binary Systems . 20 Discussion and Conclusions . 23 Chapter Three: Correcting for Telluric Absorption: Methods, Case Studies, and the TelFit Code . 41 Introduction . 41 Observations and Reduction . 42 Telluric Fitting Method . 44 Results . 46 Conclusions . 48 vii Chapter Four: Mining Planet Search Data for Binary Stars: The 1 Draconis system . 55 Introduction . 55 Observations and Data Reduction . 56 Companion Search . 57 Orbital Fit . 62 Discussion and Conclusions . 64 Chapter Five: Future Direct Spectroscopic Detection of Hot Jupiters with IGRINS 68 Introduction . 68 Instrument and Methodology . 70 Results . 75 Summary and Conclusions . 78 Chapter Six: Detection of Low-Mass-ratio Stellar Binary Systems . 86 Introduction . 86 Direct Spectral Detection Method . 92 Star Sample . 93 Data Reduction and Telluric Correction . 95 Results . 97 Completeness . 101 Multiplicity Fraction . 102 Conclusion . 104 Chapter Seven: The Inner Mass-Ratio Distribution of Intermediate-Mass Stars 117 Background . 117 Observations and Data Reduction . 119 Companion Search . 122 viii Sample Star Parameters . 126 Survey Completeness . 128 Mass-Ratio Distribution . 132 Discussion . 136 Summary . 139 Chapter Eight: Summary & Conclusions . 174 Summary of Key Results . 174 The Separation-Variant Companion Mass-Ratio Distribution . 175 Theoretical Implications . 176 Future Work Needed . 177 Bibliography . 179 ix List of Figures 2.1 Correspondence between the companion temperature measured with the direct spectral detection method, and the actual (literature) values. In all figures, the red dashed line has unity slope, the values with uncertainties are the measurements from the synthetic binary observations (see Section 2.4), and the blue lines are the line of best-fit through the data. There is significant bias in all of the measurements except for those using the near-infrared IGRINS instrument. 14 2.2 Median detection rate as a function of companion temperature and ro- tation speed. Each cell represents the median detection rate for targets with no detection in Table 2.3. Companions represented by dark cells are detectable. See Section 2.5 for details of the analysis. 17 2.3 Typical probability density function for companion rotational velocity v sin i. The distribution peaks near ∼ 5 − 10 km s−1 and extends to very high velocities. Note that the x-axis is log-spaced to more clearly show the tails of the distribution. 19 2.4 Summary of the detection rate as a function of temperature for the sample stars (Table 2.3) in which we do not detect a companion. The red dashed line gives the median detection rate, and the blue filled area illustrates the range across different primary stars. The direct spectral detection method can detect companions as late as M0 for most of our targets. 20 2.5 Cross-correlation functions for detected companions . 26 2.6 Cross-correlation functions for detected companions . 27 2.7 Temperature comparison for binaries with known secondary spectral types. The x-axis shows the companion temperature expected from the literature data (see Section 2.6.1). 28 2.8 Observed (black) and expected (green) spectra for the known binary sys- tem HIP 88290. At the expected flux ratio, the spectral lines from the companion should be easily visible. 28 x 3.1 Correction of the water bands in optical spectra. All spectra are of the A0V star HIP 20264, and are smoothed with a Savitzky-Golay filter after telluric correction to remove any broad features in the stellar spectrum. The top panel of each figure shows the observed spectrum (black solid line) and the best-fit telluric model (red dashed line), and the bottom panel shows the residuals after division by the telluric model. The telluric water lines are corrected to very near the noise level of the spectrum in the top row, revealing weak interstellar Na D lines (top left). The telluric correction leaves residuals on the order of 5% of the continuum for strong telluric lines (bottom right), possibly due to an incorrect atmosphere pro- file for water vapor. 50 3.2 Correction of the O2 bands in optical spectra. All spectra are of the A0V star HIP 20264, and are smoothed with a Savitzky-Golay filter after telluric correction to remove any broad features in the stellar spectrum. The top panel of each figure shows the observed spectrum (black solid line) and the best-fit telluric model (red dashed line), and the bottom panel shows the residuals after division by the telluric model. 51 3.3 Empirical telluric corrections. Top Row: Correction at high S/N ratio, where all 7 frames of both the target star (HIP 20264, A0V) and the tel- luric standard star (HIP 25608, A1V) were co-added before the telluric correction.

Load more

  207

Copy Link