Extrasolar Planets and Their Host Stars

In order to understand the exoplanet, you need to understand its parent star. Astrophysical parameters of extrasolar planets are directly and indirectly dependent on the properties of their respective host stars. These host stars are very frequently the only visible component in the systems. This book describes our work in the field of characterization of exoplanet host stars using interferometry to determine angular diameters, trigonometric parallax to determine physical radii, and SED fitting to determine effective temperatures and luminosities. The interferometry data are based on our decade-long survey using the CHARA Array. We describe our methods and give an update on the status of the field, including a table with the astrophysical properties of all stars with high-precision interferometric diameters out to 150 pc (status Nov 2016). In addition, we elaborate in more detail on a number of particularly significant or important exoplanet systems, particularly with respect to (1) insights gained from transiting exoplanets, (2) the determination of system habitable zones, and (3) the discrepancy between directly determined and model-based stellar radii. Finally, we discuss current and future work including the calibration of semi-empirical methods based on interferometric data.Comment: 80 pages in SpringerBrief format containing a few blank pages, 16 figures, 1 table of all stars with high-precision interferometric diameters, glossary of commonly encountered terms, SpringerBrief 2017, ISBN 978-3-319-61198-

Predicting Stellar Angular Diameters from VV, ICI_C, HH, KK Photometry

Determining the physical properties of microlensing events depends on having accurate angular sizes of the source star. Using long-baseline optical interferometry we are able to measure the angular sizes of nearby stars with uncertainties $\leq 2\%$. We present empirically derived relations of angular diameters that are calibrated using both a sample of dwarfs/subgiants and a sample of giant stars. These relations are functions of five color indices in the visible and near-infrared, and have uncertainties of 1.8-6.5% depending on the color used. We find that a combined sample of both main-sequence and evolved stars of A-K spectral types is well fit by a single relation for each color considered. We find that in the colors considered, metallicity does not play a statistically significant role in predicting stellar size, leading to a means of predicting observed sizes of stars from color alone.Comment: 8 pages, 1 figure, accepted for publication in MNRA

Non-grey dimming events of KIC 8462852 from GTC spectrophotometry

We report ground-based spectrophotometry of KIC 8462852, during its first dimming events since the end of the Kepler mission. The dimmings show a clear colour-signature, and are deeper in visual blue wavelengths than in red ones. The flux loss' wavelength dependency can be described with an \AA ngstr\"om absorption coefficient of $2.19\pm0.45$, which is compatible with absorption by optically thin dust with particle sizes on the order of 0.0015 to 0.15 $\mu$m. These particles would be smaller than is required to be resistant against blow-out by radiation pressure when close to the star. During occultation events, these particles must be replenished on time-scales of days. If dust is indeed the source of KIC 8462852's dimming events, deeper dimming events should show more neutral colours, as is expected from optically thick absorbers.Comment: 5 pages, accepted for A&A letter

The Sound of Money: Securing Copyright, Royalties, and Creative Progress in the Digital Music Revolution

Academics and popular critics alike want to distill, reform, or altogether destroy U.S. copyright law as we know it. Much of this stems from animosity toward the old-guard record industry\u27s alleged practices of overcharging consumers, underpaying royalties to artists, and suing teenagers and grandmas. But what those calling for reform all seem to neglect is a tiny but inevitable fact: for the first time in history, composers and recording artists can keep their copyrights. Tangible media sales are being replaced by P2P file sharing, retail downloads, and streaming Webcasts. Digital technologies and wireless networks have opened prime channels for music production, marketing, and distribution. Everything that used to be done by corporate middlemen like record labels and music publishers can now be accomplished either by the artist or for a reasonable professional service fee. As a result, artists can finally retain their constitutionally mandated copyright protections and control the way they license and derive royalties from their original works. Given these considerations, the administration, the Congress, and the courts should recognize that our existing strong copyright laws can benefit and incentivize artists in unprecedented ways. Instead of entertaining suggestions for massive copyright reforms such as rewriting our copyright statutes, adding more compulsory license provisions, imposing levies on technology, and expanding the fair use doctrine, let us rather embrace a simpler national innovation policy--one which protects artists\u27 incentives through strong copyright laws and promotes the practice of licensing. Ensuring that artists have the most flexible options to license their works will result in maximized creation and dissemination of original works to the public. And what better way to strive toward the constitutional objective of cultural creative Progress than by stimulating proliferation of more original works

The Sound of Money: Securing Copyright, Royalties, and Creative Progress in the Digital Music Revolution

Academics and popular critics alike want to distill, reform, or altogether destroy U.S. copyright law as we know it. Much of this stems from animosity toward the old-guard record industry\u27s alleged practices of overcharging consumers, underpaying royalties to artists, and suing teenagers and grandmas. But what those calling for reform all seem to neglect is a tiny but inevitable fact: for the first time in history, composers and recording artists can keep their copyrights. Tangible media sales are being replaced by P2P file sharing, retail downloads, and streaming Webcasts. Digital technologies and wireless networks have opened prime channels for music production, marketing, and distribution. Everything that used to be done by corporate middlemen like record labels and music publishers can now be accomplished either by the artist or for a reasonable professional service fee. As a result, artists can finally retain their constitutionally mandated copyright protections and control the way they license and derive royalties from their original works. Given these considerations, the administration, the Congress, and the courts should recognize that our existing strong copyright laws can benefit and incentivize artists in unprecedented ways. Instead of entertaining suggestions for massive copyright reforms such as rewriting our copyright statutes, adding more compulsory license provisions, imposing levies on technology, and expanding the fair use doctrine, let us rather embrace a simpler national innovation policy--one which protects artists\u27 incentives through strong copyright laws and promotes the practice of licensing. Ensuring that artists have the most flexible options to license their works will result in maximized creation and dissemination of original works to the public. And what better way to strive toward the constitutional objective of cultural creative Progress than by stimulating proliferation of more original works

Mode I fracture and durability of the CFRP -concrete interface bond

The continual degradation of civil infrastructures worldwide has prompted the need for effective solutions, posing major challenges to those involved with reinforced concrete structures. Externally bonded fiber reinforced polymer (FRP) composites have proven to be an efficient means of rehabilitation and enhancement to both existing and new structures alike. An important issue regarding this technology that needs further exploration, however, is the strength and integrity of the interface bond---the inadequacy of which can result in premature failure of the reinforced member.;Until now, there were no available methods to rigorously evaluate the interface bond strength and integrity for concrete structures externally reinforced with FRP materials. Existing large-scale tests of structural components used for stiffness and strength evaluations, on the one hand, are ill suited for detecting delamination effects. On the other, small-scale tests only provide average interface strength properties that neither describe failure mechanisms nor provide fracture toughness data.;In an effort to resolve this dilemma, a new test methodology, referred to as the Single Contoured-Cantilever Beam (SCCB) specimen, conceived and fashioned after the established double cantilever beam (DCB), is implemented. Using this newly developed experimental fracture approach, insights have been gained into the elusive fracture toughness of the CFRP-concrete interface. This methodology is then extended to evaluate the fracture toughness of the same interface as subjected to one of three commonly encountered field exposure-conditions: (1) wet-dry cycling under sodium-sulfate (Na2SO4), (2) wet-dry cycling under sodium-hydroxide (NaOH), and (3) freeze-thaw cycling under calcium chloride (CaCl2) attack. Considerable degradation of the interface bond integrity is found to have resulted in each case, when compared with companion specimens of the same age. This new test method can therefore serve both to qualify existing products as well as in developing new formulations of adhesives and FRP systems

The full spectral radiative properties of Proxima Centauri

The discovery of Proxima b, a terrestrial temperate planet, presents the opportunity of studying a potentially habitable world in optimal conditions. A key aspect to model its habitability is to understand the radiation environment of the planet in the full spectral domain. We characterize the X-rays to mid-IR radiative properties of Proxima with the goal of providing the top-of-atmosphere fluxes on the planet. We also aim at constraining the fundamental properties of the star. We employ observations from a large number of facilities and make use of different methodologies to piece together the full spectral energy distribution of Proxima. In the high-energy domain, we pay particular attention to the contribution by rotational modulation, activity cycle, and flares so that the data provided are representative of the overall radiation dose received by the atmosphere of the planet. We present the full spectrum of Proxima covering 0.7 to 30000 nm. The integration of the data shows that the top-of-atmosphere average XUV irradiance on Proxima b is 0.293 W m^-2, i.e., nearly 60 times higher than Earth, and that the total irradiance is 877+/-44 W m^-2, or 64+/-3% of the solar constant but with a significantly redder spectrum. We also provide laws for the XUV evolution of Proxima corresponding to two scenarios. Regarding the fundamental properties of Proxima, we find M=0.120+/-0.003 Msun, R=0.146+/-0.007 Rsun, Teff=2980+/-80 K, and L=0.00151+/-0.00008 Lsun. In addition, our analysis reveals a ~20% excess in the 3-30 micron flux of the star that is best interpreted as arising from warm dust in the system. The data provided here should be useful to further investigate the current atmospheric properties of Proxima b as well as its past history, with the overall aim of firmly establishing the habitability of the planet.Comment: 12 pages, 5 figures, accepted for publication in Astronomy & Astrophysic

The use of a work program assignment in casework treatment in a residential treatment home

Thesis (M.S.)--Boston Universit