Determining the Mass of Kepler-78b With Nonparametric Gaussian Process Estimation

Kepler-78b is a transiting planet that is 1.2 times the radius of Earth and orbits a young, active K dwarf every 8 hours. The mass of Kepler-78b has been independently reported by two teams based on radial velocity measurements using the HIRES and HARPS-N spectrographs. Due to the active nature of the host star, a stellar activity model is required to distinguish and isolate the planetary signal in radial velocity data. Whereas previous studies tested parametric stellar activity models, we modeled this system using nonparametric Gaussian process (GP) regression. We produced a GP regression of relevant Kepler photometry. We then use the posterior parameter distribution for our photometric fit as a prior for our simultaneous GP + Keplerian orbit models of the radial velocity datasets. We tested three simple kernel functions for our GP regressions. Based on a Bayesian likelihood analysis, we selected a quasi-periodic kernel model with GP hyperparameters coupled between the two RV datasets, giving a Doppler amplitude of 1.86 $\pm$ 0.25 m s$^{-1}$ and supporting our belief that the correlated noise we are modeling is astrophysical. The corresponding mass of 1.87 $^{+0.27}_{-0.26}$ M$_{\oplus}$ is consistent with that measured in previous studies, and more robust due to our nonparametric signal estimation. Based on our mass and the radius measurement from transit photometry, Kepler-78b has a bulk density of 6.0$^{+1.9}_{-1.4}$ g cm$^{-3}$. We estimate that Kepler-78b is 32$\pm$26% iron using a two-component rock-iron model. This is consistent with an Earth-like composition, with uncertainty spanning Moon-like to Mercury-like compositions.Comment: 10 pages, 5 figures, accepted to ApJ 6/16/201

Domicile for Immigration and Federal Gift and Estate Tax Purposes--Is a Harmonious Rule Possible

This Article explores the question of when does a nonimmigrant alien establish a United States domicile and, thus, a residence subjecting him to estate and gift tax. The authors argue that the case law, in both the tax and immigration fields, gives only a partial answer to that question, and identifies only the G-4 visa holder as capable of establishing a domicile, but fail to include other categories. The authors recommend that regulations be promulgated to delineate whether and under what circumstances each category of nonimmigrant aliens may, if at all, establish a United States domicile

Giant Planets Transiting Giant Stars

Ph.D

Eclipsing binary and white dwarf features associated with K2 target EPIC251248385

White dwarfs, remnants of Sun-like stars which have completed their evolution, are one of the most common types of stars in space. Despite this, very few white dwarfs have been observed in transiting or eclipsing systems, and only two planetary systems around white dwarfs are currently known, thus motivating a search for white dwarfs with transits or eclipses as seen by the Kepler telescope. A systematic search of K2 white dwarf targets revealed one candidate with regular eclipses, but additional research was necessary to confirm the transits and white dwarf signal were coming from the same astrophysical source. The software package PyKe was utilized to adjust the light curve aperture, and perform principal component analysis which revealed that the transits were originating from a single pixel. Generating a new lightcurve from this pixel revealed the absolute transit depth, which was unconstrained previously. Ten additional images taken with the 2m LCOGT telescope revealed that a potential target star in the single Kepler pixel was actually a cluster of three stars, but no clear transits were seen from any of the potential target stars in the followup images. Additionally, analysis of transit depths in the single pixel light curve and additional investigation of nearby bright sources supported the hypothesis that the transits were more likely to be coming from the white dwarf rather than the two other sources. However, the transit duration and shape appear atypical for white dwarf systems. Thus, despite determining the potential sources and relative sizes for the potential eclipsing white dwarf candidate, or whether the eclipses come from the white dwarf target cannot be confirmed without additional data.https://iopscience.iop.org/article/10.3847/2515-5172/ab5861Published versio

Science, perception and scale: an interdisciplinary analysis of environmental change and community adaptive capacity

Thesis (Ph.D.) University of Alaska Fairbanks, 2020The discrepancy between science-based assessments of climate change and public acknowledgement of climate change has been extensively documented at a national level. The relationship of science-based assessments and public awareness of environmental change at the local community level is less studied. An understanding of how science-based information informs local perception is important to ensure that science communication effectively supports community decision making. This dissertation explores the gap between science-based assessments and local perception of environmental change within a framework of adaptive capacity. The research is divided into three interrelated studies that provide: 1) an assessment of community perception of local environmental change, 2) a local study that illustrates science-based assessment and reporting, and 3) an evaluation of the role news media plays in communicating science to the public. The first study implemented a survey of residents on Alaska's Kenai Peninsula to evaluate individual perception of environmental change as well as attitudes regarding climate change and natural resource management. Differences in perception of local environmental change were identified among respondents as well as shared perceptions. The use of property regulation to protect the Kenai River was identified as a divisive issue; however, there was a shared concern regarding the condition of local salmon populations. A second science-based ecological study was developed that examined those issues and linked conservation of riparian vegetation to juvenile salmon rearing habitat. This study examined the diet of stream-rearing juvenile Coho Salmon (Oncorhynchus kisutch) and determined that the proportion of invertebrates which enter the stream from riparian habitats varied based on vegetation type for three streams in the Kenai watershed. The third study investigated how news media play a role in the interpretation of technical, science-based reporting for the public. It demonstrated that local news media provide a unique opportunity to promote communication of science-based information to their audiences by providing content that is familiar and relevant, offering a variety of topical framings, developing authoritative or trusted voices, and providing frequent exposure to content.Chapter 1: Introduction -- 1.1 Background -- 1.1.1 Science Communication -- 1.1.2 Vulnerability, Resilience, and Adaptive Capacity -- 1.1.3 Adaptive Capacity Framework -- 1.1.4 Social Models of Risk Perception -- 1.1.5 Cognitive Models of Risk Perception -- 1.1.6 Research Overview -- 1.1.7 Socio-Cognitive Model -- 1.1.8 Global Warming, Climate Change, and Environmental Change -- 1.2 Methods -- 1.2.1 Research Approach -- 1.2.2 Organization of the Dissertation -- 1.3 Literature Cited. Chapter 2: Role of Perception in Determining Adaptive Capacity: Communities Adapting to Environmental Change -- 2.1 Abstract -- 2.2 Introduction -- 2.3 Background -- 2.4 Study Area -- 2.5 Methods/Results -- 2.5.1 Construction of Environmental Change Perception Scales -- 2.5.2 Demographics -- 2.5.3 Climate/Environmental Change Attitudes -- 2.5.4 Binary Logistic Model -- 2.5.5 Cultural Consensus Model -- 2.6 Discussion -- 2.6.1 Perception and Variability -- 2.6.2 Perception and Attitudes -- 2.6.3 Perception, Adaptive Capacity, and Communication -- 2.7 Conclusions -- 2.8 Acknowledgements -- 2.9 Literature Cited. Chapter 3: Invertebrate Prey Contributions to Juvenile Coho Salmon Diet from Riparian Habitats along Three Alaska Streams: Implications for Environmental Change -- 3.1 Abstract -- 3.2 Introduction -- 3.3 Materials and Methods -- 3.3.1 Study Area -- 3.3.2 Characterizing Vegetation Type -- 3.3.3 Juvenile Salmon Sampling -- 3.4 Results -- 3.4.1 Vegetation Type -- 3.4.2 Invertebrate Contributions to Juvenile Salmon Diet -- 3.5 Discussion -- 3.6 Acknowledgements -- 3.7 Literature Cited. Chapter 4: Role of Local Media in Promoting Science Communication -- 4.1 Abstract -- 4.2 Introduction -- 4.3 Background -- 4.4 Methods -- 4.5 Results -- 4.5.1 Content -- 4.5.2 Voice -- 4.5.3 Sentiment -- 4.6 Discussion -- 4.7 Acknowledgements -- 4.8 Literature Cited. Chapter 5: Conclusions -- 5.1 Overview -- 5.2 Discussion -- 5.3 Limitations of Research -- 5.4 Future Research -- 5.5 Literature Cited. Chapter 6: Appendix: UAA IRB

Permafrost Database Development, Characterization, and Mapping for Northern Alaska

List of Figures - ii List of Tables - iii Acknowledgements - iii Introduction - 1 Study Area - 2 Methods - 2 Permafrost Data Compilation - 2 Geomorphic Units - 3 Classification - 3 Mapping - 3 Permafrost-soil Landscapes - 4 Classification - 4 Mapping - 4 Permafrost Characteristics and Vulnerability - 5 Web-based Data Distribution - 5 Results and Discussion - 6 Permafrost Data Compilation - 6 Geomorphic Units - 12 Classification and Descriptions - 12 Mapping - 12 Permafrost-Soil Landscapes - 20 Classification and Descriptions - 20 Landscape Profiles - 20 Mapping - 29 Permafrost Characteristics and Vulnerability - 34 Web-based Data Distribution - 40 Summary and Conclusion - 41 Literature Cited - 4

Seeing double with K2: Testing re-inflation with two remarkably similar planets around red giant branch stars

Despite more than 20 years since the discovery of the first gas giant planet with an anomalously large radius, the mechanism for planet inflation remains unknown. Here, we report the discovery of EPIC228754001.01, an inflated gas giant planet found with the NASA K2 Mission, and a revised mass for another inflated planet, K2-97b. These planets reside on ~9 day orbits around host stars which recently evolved into red giants. We constrain the irradiation history of these planets using models constrained by asteroseismology and Keck/HIRES spectroscopy and radial velocity measurements. We measure planet radii of 1.31 +\- 0.11 Rjup and and 1.30 +\- 0.07 Rjup, respectively. These radii are typical for planets receiving the current irradiation, but not the former, zero age main sequence irradiation of these planets. This suggests that the current sizes of these planets are directly correlated to their current irradiation. Our precise constraints of the masses and radii of the stars and planets in these systems allow us to constrain the planetary heating efficiency of both systems as 0.03% +0.03%/-0.02%. These results are consistent with a planet re-inflation scenario, but suggest the efficiency of planet re-inflation may be lower than previously theorized. Finally, we discuss the agreement within 10% of stellar masses and radii, and planet masses, radii, and orbital periods of both systems and speculate that this may be due to selection bias in searching for planets around evolved stars.Comment: 18 pages, 15 figures, accepted to AJ. Figures 11, 12, and 13 are the key figures of the pape