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Brickman, Jacklyn E. "Experiments in Biological Planet Formation and Plants: Nourishing Bodies, Nourishing Planets." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595340630648528.
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Trotta, Leonardo Di Schiavi. "Modelo dinâmico 3-D para a evolução do sistema Plutão-Caronte /." Rio Claro, 2017. http://hdl.handle.net/11449/150604.
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Orientador: Tadashi YokoyamaBanca: Nelson Callegari Junior
Banca: Rodney da Silva Gomes
Resumo: O sistema Plutão-Caronte é um par quase binário em estado de duplo sincronismo. Hoje sabe-se que Plutão possui cinco satélites: Caronte, Styx, Nix, Kerberos e Hydra, onde os últimos quatro são muito menores que Caronte. A origem mais plausível para o sistema Plutão-Caronte é a de um impacto de grandes proporções entre corpos de tamanhos similares, onde o impactador (que viria a ser Caronte) permanece quase intacto após o evento. Caronte iniciaria o movimento orbital próximo de Plutão (ex: a≈4 Rp) com ambos rotacionando rapidamente, como consequência da colisão mútua. Devido a intensa maré, suas distâncias irão evoluir e seus equadores (provavelmente desalinhados devido ao choque) irão também evoluir em consonância com seus respectivos spins. Alguns autores, por meio de um modelo bidimensional, tomando a maré modelada por Mignard (1980) e Peale (2007), usando dois métodos distintos, evoluíram Plutão-Caronte à partir deste cenário, reproduzindo os parâmetros orbitais e rotacionais atuais do sistema. Neste trabalho fazemos um estudo tridimensional, usando na parte rotacional as variáveis canônicas de Andoyer. Nesta abordagem, integramos a atitude de Plutão e Caronte por meio das equações de Hamilton, enquanto que a dinâmica translacional é feita classicamente via equações cartesianas de Newton. As contribuições dos torques, devidas às interações por efeito de maré entre Plutão e Caronte são inseridas nas equações de Hamilton. Como resultado mostramos o alinhamento dos equadores ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The Pluto-Charon system is almost a binary system in dual synchronous state. It is well known that Pluto has five satellites: Charon, Styx, Nix, Kerberos and Hydra, where the latter four are much smaller than Charon. The most plausible origin for the Pluto-Charon system is an oblique impact of great proportions between bodies with similar sizes. In this scenario, the impactor, which would later originate Charon, would remain almost intact after the collision. Initially the satellite would be revolving very close to Pluto (ex: a≈4Rp), with both bodies rotating very fast, as consequence of the mutual collision. The strong tidal effects, due to the initial approximation of both bodies combined with the fast rotation, expanded Charon's orbit, so as their equators aligned (probably misaligned due to the collision), in consonance with their respective spins. Some authors, using a two dimensional system and tidal forces modeled by Mignard (1980) and Peale (2007), with two distinct methods, evolved PlutoCharon from this scenario. They were able to reproduce the current orbital and rotational parameters of the system. In our work, a three-dimensional study was done, using the Andoyer's variable for the rotational problem. We integrated Pluto and Charon's atitude through Hamilton's equation, while the translational dynamics is calculated classically through Newton's cartesian equations. Torque's contributions due to tides raised on both Pluto and Charon are introduced in Hamilton's equ... (Complete abstract click electronic access below)
Mestre
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Joos, Franco. "Polarimetry of gas planets /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17051.
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Turner, Jake D., Robin M. Leiter, Lauren I. Biddle, Kyle A. Pearson, Kevin K. Hardegree-Ullman, Robert M. Thompson, Johanna K. Teske, et al. "Investigating the physical properties of transiting hot Jupiters with the 1.5-m Kuiper Telescope." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/626279.
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We present new photometric data of 11 hot Jupiter transiting exoplanets (CoRoT-12b, HATP-5b, HAT-P-12b, HAT-P-33b, HAT-P-37b, WASP-2b, WASP-24b, WASP-60b, WASP-80b, WASP-103b and XO-3b) in order to update their planetary parameters and to constrain information about their atmospheres. These observations of CoRoT-12b, HAT-P-37b and WASP-60b are the first follow-up data since their discovery. Additionally, the first near-UV transits of WASP-80b and WASP-103b are presented. We compare the results of our analysis with previous work to search for transit timing variations (TTVs) and a wavelength dependence in the transit depth. TTVs may be evidence of a third body in the system, and variations in planetary radius with wavelength can help constrain the properties of the exoplanet's atmosphere. For WASP-103b and XO-3b, we find a possible variation in the transit depths which may be evidence of scattering in their atmospheres. The B-band transit depth of HAT-P-37b is found to be smaller than its near-IR transit depth and such a variation may indicate TiO/VO absorption. These variations are detected from 2-4.6s, so follow-up observations are needed to confirm these results. Additionally, a flat spectrum across optical wavelengths is found for five of the planets (HAT-P-5b, HAT-P-12b, WASP-2b, WASP-24b and WASP-80b), suggestive that clouds may be present in their atmospheres. We calculate a refined orbital period and ephemeris for all the targets, which will help with future observations. No TTVs are seen in our analysis with the exception of WASP-80b and follow-up observations are needed to confirm this possible detection.
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Ortiz, Álvarez Mauricio [Verfasser], and Andreas [Akademischer Betreuer] Quirrenbach. "Planets around giant stars: Two close-in transiting planets and one S-type planet in an eccentric binary system / Mauricio Ortiz Álvarez ; Betreuer: Andreas Quirrenbach." Heidelberg : Universitätsbibliothek Heidelberg, 2017. http://d-nb.info/118073890X/34.
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Lines, Stefan Matthew. "The formation of circumbinary planets." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.702118.
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The discovery of nearly two thousand extrasolar planets over the last two decades is indicative that planets form everywhere. Exoplanet detections have been made of a plethora of planetary types and sizes across a wide range of orbital characteristics. One of the more exotic locations that planets have been discovered in is around stellar binaries. Their proximity to such a large time-dependent potential from the orbital motion of the stars can be problematic for their formation and long-term stability. Circumbinary planets, with orbits that fully encompass the binary, have been found to orbit as close as 0.3 au to the binary barycenter and are thus subject to strong gravitational perturbations. In the formation stage, the circumbinary protoplanetary disk experiences interactions with the binary which significantly alters the dynamics and hence collisional evolution of planetesimals which struggle to grow into the planets we see. To answer the question: Could observed circumbinary planets have formed in-situ? we perform a combination of N-body, hydro dynamical and subsequently hybrid simulations to investigate the feasibility of planet growth under these conditions. Our initial N-body simulations are performed in association with an advanced collision model to identify locations in the disk where planetesimals can accrete. We perform hydro dynamical simulations of circumbinary gas disks to investigate the structure and evolution of a fluid in response to a binary, across a wide range of fluid parameters. The resulting data, a quasi-steady-state surface density profile, is integrated in a semi-analytical way to account for gas feedback on planetesimals. Our work suggests that the majority of observed closely-orbiting circumbinary planets could not form in-situ due to an overwhelming number of erosive collisions caused by high impact velocities originating from the planetesimals' dynamical interaction with the binary and gas gravity. Planetary embryos must have formed further out in the disk, where velocities are lower, and this result indicates that migration is a necessary component of planetary evolution in these systems.
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Janes, Daniel Mark. "Tectonics of one-plate planets." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185087.
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The Voyager 2 encounter with Neptune and its moons in August of 1989 completed the discovery phase of planetary exploration. In the 25 years since Mariner 4 returned the first images of another planet, geophysical models for such basic processes as mantle convection and loading which were developed for the Earth have been strained beyond their limits by features such as the Tharsis rise on Mars and the coronae of Miranda which cover as much as a quarter of their planetary circumference. In this work I develop a general planetary shell model in spherical coordinates that is capable of treating shells of arbitrary thickness and driving forces of arbitrary breadth. I then present a methodology for finding the forces exerted on the shell from two processes. I first develop a treatment for mantle convection driven by a density anomaly within a viscous mantle. This model is applied to the small moon of Uranus, Miranda, to study the three large coronae which dominate its surface and for which several competing hypotheses were offered, two of which invoked mantle convection driven by density anomalies of opposite sign. I then develop a general model for loading of the lithosphere and examine the effects of a range of load breadths and lithosphere thicknesses. I map out the combinations of these two variables where classical approximations such as the flat-plate and thin-shell models are applicable as well as determine the nature and extent of the transition between these two regimes. Finally, I employ finite element modeling to investigate the coronae on Venus, showing that morphological aspects of these features reported in the literature can be produced by flexure of the lithosphere beneath a volcanic load and gravitational sliding of a cooled crust off these volcanic mounds. I then, however, produce independent characteristic topographic profiles for three of the more regular coronae which question how typical the reported morphologies are in the coronae in general.
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Fortney, Jonathan J. "The evolution of giant planets." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/290002.
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As a whole this dissertation aims to understand giant planets as an entire class of astronomical objects. Initially we investigate the mechanics and evolutionary effects of phase separation in the deep interiors of giant planets. We present the first models of Saturn and Jupiter to couple their evolution to both a radiative-atmosphere grid and to high-pressure phase diagrams of hydrogen with helium and other admixtures. We find that previously calculated hydrogen-helium phase diagrams in which Saturn's interior reaches a region of predicted helium immiscibility do not allow enough energy release to prolong Saturn's cooling to its known age and effective temperature. We explore modifications to published phase diagrams that would lead to greater energy release. Alternatively, we also explore the evolutionary effects of the phase separation of an icy component. We then expand our inhomogeneous evolutionary models to the evolution of hypothetical extrasolar giant planets (EGPs) in the 0.15 to 3.0 Jupiter mass range, incorporating helium phase separation using the hydrogen-helium phase diagram we have calibrated to Jupiter and Saturn. We show how phase separation increases the luminosity, effective temperature, and radii, and decreases the atmospheric helium mass fraction, for various giant planets as a function of age. We also show the effects of irradiation and dense cores. Next we turn to the atmosphere of the transiting EGP, HD209458b. Using a self-consistent atmosphere code, we construct a new model of the planet's atmosphere to investigate the disparity between the observed strength of the sodium absorption feature at 589 nm and the predictions of previous models. For the atmospheric temperature-pressure profile we derive, silicate and iron clouds reside at a pressure of several mbar in the planet's atmosphere. These clouds lead to increased absorption in bands directly adjacent to the sodium line core. Using a non-LTE sodium ionization model, we show that ionization leads to a slight weakening of the sodium feature. The sensitivity of our conclusions to the derived atmospheric temperature-pressure profile is discussed. We show how our investigation leads to a better understanding of how the planetary radius measurements should be compared to model radii.
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Zaranek, Sarah Ellen. "Roles of convection in the evolution of planetary interiors and terrestrial lithospheres /." View online version; access limited to Brown University users, 2005. http://wwwlib.umi.com/dissertations/fullcit/3174708.
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Steffen, Jason. "Detecting new planets in transiting systems /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/9686.
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Barker, Adrian John. "Tidal interactions between planets and stars." Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/240581.
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Since the first discovery of an extrasolar planet around a solar-type star, observers have detected over 500 planets outside the solar system. Many of these planets have Jovian masses and orbit their host stars in orbits of only a few days, the so-called 'Hot Jupiters'. At such close proximity to their parent stars, strong tidal interactions between the two bodies are expected to cause significant secular spin-orbit evolution. This thesis tackles two problems regarding the tidal evolution of short-period extrasolar planets. In the first part, we adopt a simple model of the orbit-averaged effects of tidal friction, to study the tidal evolution of planets on inclined orbits. We also analyse the effects of stellar magnetic braking. We then discuss the implications of our results for the importance of Rossiter-Mclaughlin effect observations. In the second part, we study the mechanisms of tidal dissipation in solar-type stars. In particular, internal gravity waves are launched at the interface of the convection and radiation zones of such a star, by the tidal forcing of a short-period planet. The fate of these waves as they approach the centre of the star is studied, primarily using numerical simulations, in both two and three dimensions. We find that the waves undergo instability and break above a critical amplitude. A model for the tidal dissipation that results from this process is presented, and its validity is verified by numerical integrations of the linear tidal response, in an extensive set of stellar models. The dissipation is efficient, and varies by less than an order of magnitude between all solar-type stars, throughout their main-sequence lifetimes, for a given planetary orbit. The implications of this mechanism for the survival of short-period extrasolar planets is discussed, and we propose a possible explanation for the survival of all of the extrasolar planets currently observed in short-period orbits around F, G and K stars. We then perform a stability analysis of a standing internal gravity wave near the centre of a solar-type star, to understand the early stages of the wave breaking process in more detail, and to determine whether the waves are subject to weaker parametric instabilities, below the critical amplitude required for wave breaking. We discuss the relevance of our results to our explanation for the survival of short-period planets presented in the second part of this thesis. Finally, we propose an alternative mechanism of tidal dissipation, involving the gradual radiative damping of the waves. Based on a simple estimate, it appears that this occurs even for low mass planets. However, it is in conflict with current observations since it would threaten the survival of all planets in orbits shorter than 2 days. We discuss some hydrodynamic instabilities and magnetic stresses which may prevent this process.
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Carter, Andrew James. "Observation and modeling of extrasolar planets." Thesis, Open University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578669.
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The field of exoplanet research has currently yielded the discovery of 552 planets. This figure includes 132 transiting planets which can be studied in greater detail and have formed the cornerstone of research to characterise the exoplanet population. In particular, such studies seek to analyse the planetary atmospheres, but research has thus far yielded more questions than answers. Exoplanetary atmospheric studies have typically focussed on one planet apiece - complicating any comparative analysis as every result employs different methods and instruments. For a comprehensive, comparative study, a robust and reliable means of reducing and analysing such observations is required, along with a body of data from a single instrument. One such instrument is the Bubble Space Telescope (BST) whose NICMOS (Near Infrared Camera and Multi-Object Spectrometer) instrument has observed the transits of nine extrasolar planets across multiple wavelengths in the near-infrared. A robust pipeline has been developed to reduce all such observations using the fame techniques. This pipeline reduces grism images of an exoplanet host star across a transit event. These exposures are checked for bad pixels, flat fielded and background-subtracted before robust extraction of a transit light curve. This light curve is then detrended to remove systematic noise by application of a new technique developed in this study. Following detrending, the light curve is modelled using a be- spoke MCMC (Markov-Chain Monte-Carlo) algorithm to determine the planetary parameters. A continuum of wavelength-dependent transit light curves is also extracted, detrended and modelled to de- termine the variation in transit depth with wavelength; and .hereby infer the transmission spectrum of the planet's atmosphere. The finished pipeline has been applied to three sets of HST NIC- MOS observations covering the transits of WASP-2b, HD189733b and GJ436b. For each data set, a new set of planetary parameters has been derived and for WASP-2b and HD189733b an atmospheric transmission spectrum extracted. Both spectra show signs of atmospheric haze and molecular absorption, but also evidence of residual systematic noise, complicating analysis.
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Tsapras, Yiannis. "Microlensing search for extra solar planets." Thesis, University of St Andrews, 2002. http://hdl.handle.net/10023/7092.
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Gravitational microlensing may be used to probe distant stars for planetary companions. The presence of a planet in the vicinity of a star acting as the lens may cause a short lived anomaly in the observed lightcurve of the lensing event. By quantifying these anomalies we may place limits on the mass of the companion relative to the lens as well as the position of the planet relative to the primary lens. The detection probability is proportional to mp, where mp is the planet mass. All current follow-up teams use dedicated observations on a preselected sample of mainly high-amplification events. Microlensing has yet to yield an undisputed planetary detection. In chapter 1 we give an introduction to the field of extra-solar planets and proceed to present the theory employed in microlensing studies in chapter 2. Chapter 3 deals with the principles of data aquisition and data reduction techniques that provide the high precision photometry needed for these studies. In the data analysis presented in chapters 4 and 5 of this thesis, we use a different observing approach. We spread our observing time between many targets obtaining 1 to 2 frames per night on each event. Our aim is not to characterize, but only detect the first exoplanetary signal in a microlensing campaign. The pilot run presented in chapter 4 showed it is possible to place significant limits on the presence of planets even from observations performed from a Northern site. In Chapter 5 we analyse data obtained from the JKT at La Palma together with publicly available OGLE data to place useful constraints on the presence of planets orbiting the lens stars. We detect no undisputed planetary signals but calculate high detection probabilities for two events. In chapter 6 we present our analysis of three years (1998-2000) of OGLE data (146 events). We compute the detection probability for each event individually and the total detection probability for the whole sample. Our selection criteria return 6 candidate events, 5 of which could possibly be attributed to planets. However, the OGLE data is insufficient to draw definite conclusions. If we assume that the observed deviations are not due to planetary companions, we conclude that less than 18% of the lens stars have planets with mp = m5., orbiting them at an orbital radius of 1.1 <a<3 AU. We conclude with a summary of this thesis in chapter 7.
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Watkins, Christopher Lloyd. "Atmospheric gravity waves on giant planets." Thesis, Queen Mary, University of London, 2012. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8683.
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Internal gravity waves are a common feature of stratified fluids. They facilitate transport of momentum and energy – thus influencing the evolution of the fluid. There is a large body of research addressing the behaviour of gravity waves in the terrestrial atmosphere. This thesis builds and extends the research to giant planets – in particular to close-in extrasolar giant planets and the solar system giant planet, Jupiter. Because the atmospheres of close-in giant planets are expected to be strongly stratified, knowledge of the behaviour of gravity waves in such atmospheres is especially important. Close-in giant planets are thought to have their rotations and orbital period 1:1 synchronised, i.e., they are “tidally locked”. Such planets do not exist in the Solar System. However, many are known from observations of extrasolar systems. Their synchronisation means that they have a permanent day-side and night-side leading to interesting atmospheric dynamics. Modelling these circulations with global circulation models (GCMs) and comparing these models with observations is an active research area. However, many GCMs filter some or all gravity waves removing their effects. This thesis addresses this by explicitly looking at the effects gravity waves can have on the circulation. It is shown that gravity waves provide a mechanism for accelerating, decelerating, and heating the flow. Further, horizontally propagating gravity waves are shown to provide a possible means for coupling the day- and night-sides of tidally locked planets. As well as affecting the dynamics of the atmosphere, gravity wave behaviour is affected by the dynamics of the atmosphere. Therefore, gravity waves can be used to explore atmospheric properties. In this thesis gravity waves observed in Jupiter’s atmosphere, by the Galileo probe, are used to identify features of Jupiter’s atmosphere such as the altitude of the turbopause and the vertical profile of zonal winds at the probe entry site.
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Muterspaugh, Matthew Ward. "Binary star systems and extrasolar planets." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34646.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.Includes bibliographical references (p. 121-137).
For ten years, planets around stars similar to the Sun have been discovered, confirmed, and their properties studied. Planets have been found in a variety of environments previously thought impossible. The results have revolutionized the way in which scientists understand planet and star formation and evolution, and provide context for the roles of the Earth and our own solar system. Over half of star systems contain more than one stellar component. Despite this, binary stars have often been avoided by programs searching for planets. Discovery of giant planets in compact binary systems would indirectly probe the timescales of planet formation, an important quantity in determining by which processes planets form. A new observing method has been developed to perform very high precision differntial astrometry on bright binary stars with separations in the range of 0.1 - 1.0 arcseconds. Typical measurement precisions over an hour of integration are on the order of 10 micro-arcseconds (as), enabling one to look for perturbations to the Keplerian orbit that would indicate the presence of additional components to the system. This method is used as the basis for a new program to find extrasolar planets. The Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES) is a search for giant planets orbiting either star in 50 binary systems. The goal of this search is to detect or rule out planets in the systems observed and thus place limits on any enhancements of planet formation in binaries. It is also used to measure fundamental properties of the stars comprising the binary, such as masses and distances, useful for constraining stellar models at the 10-3 level.
(cont.) This method of differential astrometry is applied to three star systems. Equulei is among the most well-studied nearby binary star systems. Results of its observation have been applied to a wide range of fundamental studies of binary systems and stellar astrophysics. PHASES data are combined with previously published radial velocity data and other previously published differential astrometry measurements to produce a combined model for the system orbit. The distance to the system is determined to within a twentieth of a parsec and the component masses are determined at the level of a percent. n Pegasi is a well-known, nearby triple star system consisting of a "wide" pair with semi-major axis 235 milli-arcseconds, one component of which is a single-line spectroscopic binary (semi-major axis 2.5 milli-arcseconds). Using high-precision differential astrometry and radial velocity observations, the masses for all three components are determined and the relative inclination between the wide and narrow pairs' orbits is found to be 43.8 ± 3.0 degrees, just over the threshold for the three body Kozai resonance. The system distance is determined to a fifth of a parsec, and is consistent with trigonometric parallax measurements. V819 Herculis is a well-studied triple star system consisting of a "wide" pair with 5.5 year period, one component of which is a 2.2-day period eclipsing single-line spectroscopic binary. Differential astrometry measurements from PHASES determine the relative inclination of the short- and long-period orbits. Finally, the prospects for finding planets that simultaneously circle both stars in a binary system are evaluated. Planet searches of this type would represent a complementary investigation to PHASES and contribute similar scientific results.
by Matthew Ward Muterspaugh.
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Mustill, Alexander James. "The dynamics of planets and discs." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610345.
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Jackson, Brian. "Tidal Evolution of Extra-Solar Planets." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/196152.
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In both our solar system and extra-solar planetary systems, tides may have a variety of effects, driving complex orbital evolution and geophysical processes. For extra-solar planets with orbits that pass very close to their host stars, tides have reduced orbital eccentricities and semi-major axes, and the rates of tidal evolution may change dramatically as orbits evolve. Understanding how the orbits have evolved and, ultimately, discerning the origins of close-in extra-solar planets require accounting for all the complexity of tidal evolution. The accompanying dissipation of tidal energy within the planets has probably also affected their internal structures. In some cases, tidal dissipation may account the apparent discrepancy between predictions and observations of the radii of extra-solar planets that transit their host stars. Evolutionary models for these planets that allow determinations of their internal structures and composition must include highly variable tidal heating rates. The same tidal evolution and heating probably also affects the orbital and geophysical properties of rocky extra-solar planets and may play a key role in determining whether such a planet can harbor life. As tides reduce a planet's semi-major axis, the planet may eventually pass so close to its host star that the star's gravity completely disrupts the planet, leading to the destruction of many planets. Tidal destruction has left a discernible signature on the distribution of extra-solar planetary orbits, and so interpretations of the distribution in terms of the origins of planets must include consideration of the effects of tidal destruction.
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Loyd, R. O. Parke, T. T. Koskinen, Kevin France, Christian Schneider, and Seth Redfield. "Ultraviolet C ii and Si iii Transit Spectroscopy and Modeling of the Evaporating Atmosphere of GJ436b." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624389.
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Hydrogen gas evaporating from the atmosphere of the hot-Neptune GJ436b absorbs over 50% of the stellar Lya emission during transit. Given the planet's atmospheric composition and energy-limited escape rate, this hydrogen outflow is expected to entrain heavier atoms such as C and O. We searched for C and Si in the escaping atmosphere of GJ436b using far-ultraviolet Hubble Space Telescope COS G130M observations made during the planet's extended H I transit. These observations show no transit absorption in the C II 1334,1335 angstrom and Si III 1206 angstrom lines integrated over [-100, 100] km s(-1), imposing 95% (2 sigma) upper limits of 14% (C II) and 60% (Si III) depth on the transit of an opaque disk and 22% (C II) and 49% (Si III) depth on an extended highly asymmetric transit similar to that of H I Ly alpha. C+ is likely present in the outflow according to a simulation we carried out using a spherically symmetric photochemical-hydrodynamical model. This simulation predicts an similar to 2% transit over the integrated bandpass, consistent with the data. At line center, we predict the C II transit depth to be as high as 19%. Our model predicts a neutral hydrogen escape rate of 1.6 x 10(9) g s(-1) (3.1 x 10(9) g s(-1) for all species) for an upper atmosphere composed of hydrogen and helium.
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Turner, Oliver David. "Discovery and characterisation of transiting extra-solar planets with the Wide Angle Search for Planets (WASP) survey." Thesis, Keele University, 2017. http://eprints.keele.ac.uk/3563/.
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In July of 2012 the WASP-South instrument was modified to allow it to collect data on brighter stars. This change was motivated by the dearth of planets known to orbit bright hosts in the southern hemisphere and the depth of study possible for HD209458 b and HD189733 b. These two planets orbit very bright stars in the northern hemisphere and have lead to a wealth of discoveries thanks to the relative ease with which they can be studied. My initial work with the Wide Angle Search for Planets (WASP) project was to contribute to updating the existing automated data reduction pipeline. I investigated the effects of, and helped to implement, various changes made to the pipeline in order to optimise its performance for brighter stars. During these investigations I also contributed fixes for several pipeline bugs. As a result of these changes the pipeline provides a level of precision with the new data as the previous version did with data from the unmodified instrument. The modified instrument was initially intended to collect data for 3 years. I performed an investigation in order to see if there was value to be gained in extending this period. I injected simplified transit signals into data gathered with the modified instrument that showed no known or candidate signals. These transit signals had a variety of different periods and depths, ranging from those we would expect to detect to those we would expect to be below our detection limits. My results showed that we can expect to recover between 42% and 72% of hot-Jupiters with transit depths between 0.5% and 2% and periods shorter than 10 days. This is comparable to a similar study of WASP-South before the modifications. I have also contributed to the follow-up of several newly discovered and previously known planets. I have presented the tools used by WASP to discover and characterise exoplanetary systems and have applied them to the investigation of these systems. With new data, I update and refine parameters for 7 previously known WASP planets. I resolve discrepancies in previous studies of WASP-31, show that WASP-42 may be an important probe of planet migration theory and show that seemingly “typical” systems may warrant re-observing. I present three newly discovered systems: WASP-120 b, a system with a star showing variable activity and a possibly eccentric planet orbit, WASP-122 b, which offers a good opportunity for atmospheric study, and WASP-123 b, which orbits an old star, ∼ 7 Gyr.
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McLeod, Scott Stuart. "Isostatically compensated extensional tectonics on Enceladus." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/mcleod/McLeodS0509.pdf.
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Saturn's moon Enceladus is the smallest body in the solar system known to be geologically active. Extensive, energetic resurfacing processes are ongoing and it possesses a system of geysers at the South Pole that supply material to the E-ring. The South Polar Terrain (SPT) is the youngest region on Enceladus and its contacts with the older cratered and grooved plains to the north are delineated by a variety of complex geologic features including mountain ranges and massive grabens. Many of the geologic features seen on Enceladus bear superficial resemblance to terrestrial structures associated with plate tectonics. A detailed structural geologic analysis, supported by crater counting studies, was used to determine whether the features seen on Enceladus are compatible with terrestrial-style plate tectonics. On Earth, new lithosphere is created at spreading centers and consumed at subduction zones, enabled by the compositional dichotomy between oceanic and continental crust. Enceladus's lithosphere appears to be made entirely of pure water ice, so any newly formed crust will have the same composition, but lower density due to higher temperature, making subduction and consequently spreading, as we understand it on Earth, impossible. Geometrically, the absence of fold-thrust belts and transform faults in the presence of normal faults and basin and range-style features implies extension without corresponding shortening elsewhere. This is not possible in a conventional (terrestrial) plate tectonic regime as surface area is not conserved; therefore, an alternate explanation is required. Topographic features associated with density contrasts between old and new terrain that are diagnostic of terrestrial spreading centers are also not observed on Enceladus. I conclude that features observed on Enceladus are inconsistent with terrestrial-style plate tectonic spreading, and represent a style of tectonism peculiar to bodies with icy lithospheres. I present an interpretation in which the cordillera surrounding the SPT is a broadly developed extensional regime, and describe a model for its formation that is consistent with the known physical properties of Enceladus, dependent on the presence of a water-ice phase transition below the south polar terrain.
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Turse, Carol Louise. "Testing the hydrogen peroxide-water hypothesis of life on Mars using the differential scanning calorimeter as an analog for the TEGA instrument on the Mars Phoenix lander." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Summer2009/c_turse_072309.pdf.
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Thesis (M.S. in environmental science)--Washington State University, August 2009.Title from PDF title page (viewed on Sept. 22, 2009). "School of Earth and Environmental Sciences." Includes bibliographical references (p. 92-97).
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Underwood, David R. "The stability of orbits of putative Earth-mass planets or satellites of giant planets within known exoplanetary systems." Thesis, Open University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437779.
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Espinoza, Nestor, Rafael Brahm, Andres Jordan, James S. Jenkins, Felipe Rojas, Paula Jofre, Thomas Madler, et al. "DISCOVERY AND VALIDATION OF A HIGH-DENSITY SUB-NEPTUNE FROM THE K2 MISSION." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/624071.
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We report the discovery of K2-56b, a high-density sub-Neptune exoplanet, made using photometry from Campaign 4 of the two-wheeled Kepler (K2) mission, ground-based radial velocity (RV) follow-up from HARPS and high-resolution lucky and adaptive optics imaging obtained using AstraLux and MagAO, respectively. The host star is a bright (V - 11.04, K-s - 9.37), slightly metal-poor ([Fe/H] - -0.15 +/- 0.05 dex) solar analogue located at 152.1(-7.4)(+9.7) pc from Earth, for which we find a radius of R-* = 0.928(-04040)(+0.055) and a mass of M-* = 0.961(-0.029)(+0.032) M-circle dot. A joint analysis of the K2 photometry and HARPS RVs reveal that the planet is in a approximate to 42 day orbit around its host star, has a radius of 2.23(011)(+0.14)R(circle plus), and a mass of 16.3(6.1)(+6.0) M-circle plus. Although the data at hand put the planet in the region of the massradius diagram where we could expect planets with a pure rock (i.e., magnesium silicate) composition using two-layer models (i.e., between rock/iron and rock/ice compositions), we discuss more realistic three-layer composition models which can explain the high density of the discovered exoplanet. The fact that the planet lies in the boundary between "possibly rocky" and "non-rocky" exoplanets makes it an interesting planet for future RV follow-up.
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Doellinger, Michaela. "Hunting for extrasolar planets around K giants." Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-99700.
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Leigh, Christopher. "The detection and characterisation of extrasolar planets." Thesis, University of St Andrews, 2004. http://hdl.handle.net/10023/12943.
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Since the discovery of 51 Pegasi b in 1995, continued observations have indirectly identified over 110 planetary objects. These Jupiter-mass objects cause their host star to "wobble" slightly about the common centre-of-mass of the system, which is detectable as radial motion in high-precision Doppler spectroscopy. Of the known planets, approximately 20% are found to orbit within 0.1 AU of the star, whilst the transit of HD209458 has inferred the gas-giant nature of these close-in extrasolar giant planets (CEGPs). The discovery of CEGPs has produced a wave of speculative theory as to the exact nature of these objects, and how they came to exist so close to their parent star. Our spectroscopic technique provides a method of achieving the direct detection of a CEGP atmosphere, the results of which will allow us to test emerging models that aim to predict the atmospheric nature of CEGPs and may provide additional information on the orbital inclination and mass of the planet. We start with a historical review of the field of extrasolar planets, followed by an introduction to the fundamental concepts which underpin the reflection of starlight from a planet's surface. We then investigate the prospects of detecting such a reflection, before detailing the technique we have devised and applied here to two known CEGP hosts. In the first instance, r Bootis, we combined observations at the 4.2-m William Herschel telescope in 1998, 1999 and 2000. The dataset comprised 893 high-resolution échelle spectra with a total integration time of 75hr 32min spanning 17 nights. We establish an upper limit on the planet's geometric albedo p < 0.39 (at the 99.9% significance level) at the most probable orbital inclination i ~ 36 deg, assuming a grey albedo, a Venus-like phase function and a planetary radius Rp - 1.2RJup. Although a weak candidate signal appears near to the most probable radial velocity amplitude, its statistical significance is insufficient for us to claim a detection with any confidence. In the second instance, HD75289, 4 nights of VLT(UT2)/UVES observations were secured in 2003 Jan, yielding 684 high-resolution spectra with a total integration time of 26 hours. We establish an upper limit on the planet's geometric albedo p < 0.12 (to the 99.9% significance level) at the most probable orbital inclination i ~/= 60 deg, assuming a grey albedo, a Venus-like phase function and a planetary radius Rp = 1.6RJup. In both cases, we are able to rule out some combinations of the predicted planetary radius and atmospheric albedo models with high, reflective cloud decks.
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Joiner, Joanna. "Millimeter-wave spectra of the jovian planets." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/15641.
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Barnett, D. N. "Convection, elasticity and flexure inside terrestrial planets." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596394.
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In this dissertation, the large-scale geophysical behaviour of the Earth, Venus and Mars are compared, using data collected by the Magellan spaceprobe (for Venus) and the Viking and Mars Global Surveyor (MGS) probes (for Mars). Neither Venus nor Mars show evidence of plate tectonics operating at the present day. On Venus, the lack of water means the frictional resistance at faults and the viscous drag on the base of the moving lithospheric plates are too high to be overcome by the driving forces for plate tectonics. The high elastic thickness of Mars results in a large frictional resistance to fault motion, although the faults themselves are probably no stronger than those on the Earth, and means large compressive stresses are required to initiate subduction. The likely high viscosity of the martian mantle, a consequence of its probable dryness and low temperature, may also result in large drag forces on the base of the lithosphere. Plate tectonics may have operated in the past on both planets, providing a possible explanation for the rapid resurfacing of Venus required by the crater counts and the linear magnetic anomalies recently discovered on Mars.
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Lam, Hoanh An. "H'+â†3 in the jovian planets." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338995.
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Daley-Yates, Simon. "Radio emission from hot stars and planets." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8585/.
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The winds of hot massive stars and hot giant planets grant us insight into the mechanisms by which the interstellar medium is enriched and the history behind planetary system formation. This thesis comprises a series of studies investigating the magnetospheric dynamics and emission properties of both these astronomical bodies. An analytic study of thermal radio and sub-mm emission from the winds of massive stars investigates the contribution from acceleration and wind clumping. The results show strong variation of the spectral index, corresponding to the wind acceleration region and clumping of the wind. This shows a strong dependence of the emission on the wind velocity and clumping profile. By performing simulations of a magnetic rotating massive star with a non-zero dipole obliquity, it has been shown that the predicted radio and sub mm observable light curves and continuum spectra are highly dependent on the magnetic confinement of the stellar wind close to the surface, and that understanding the observer inclination and magnetic dipole obliquity are vital for determining the stellar mass-loss rate from radio observations. Hot Jupiter exoplanets are expected to produce strong radio emission in the MHz range but have not been detected. To explain the absence of observational results, simulations of the interactions between a solar type star and hot Jupiter were conducted and used to calculate the efficiency of radio emission generation within the planet's magnetosphere. Results show that it is completely inhibited by the planet's expanding atmosphere. Finally, the first simulations of wind-wind interactions between a solar type star and a short period hot Jupiter exoplanet that resolves accretion onto the surface of the star are presented. The accretion point, rate and periodicity are quantified, with the results indicating that material accreting onto the star perturbs surface density and temperature in a periodic manner, in agreement with observations.
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Nikku, Madhusudhan 1980. "Retrieval of atmospheric properties of extrasolar planets." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/63006.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 133-137).
We present a new method to retrieve molecular abundances and temperature profiles from exoplanet atmosphere photometry and spectroscopy. Our method allows us to run millions of 1-D atmosphere models in order to cover the large range of allowed parameter space. In order to run such a large number of models, we have developed a parametric pressure-temperature (P-T) profile coupled with line-by-line radiative transfer, hydrostatic equilibrium, and energy balance, along with prescriptions for non-equilibrium molecular composition and energy redistribution. The major difference from traditional 1-D radiative transfer models is the parametric P-T profile, which essentially means adopting energy balance only at the top of the atmosphere and not in each layer. We see the parametric P-T model as a parallel approach to the traditional exoplanet atmosphere models that rely on several free parameters to encompass unknown absorbers and energy redistribution. The parametric P-T profile captures the basic physical features of temperature structures in planetary atmospheres (including temperature inversions), and reproduces a wide range of published P-T profiles, including those of solar system planets. We apply our temperature and abundance retrieval method to two exoplanets which have the best data available, HD 189733b and HD 209458b. For each planet, we compute - 107 atmospheric spectra on a grid in the parameter space, and report contours of the error surface, given the data. For the day-side of HD 189733b, we place constraints on the atmospheric properties based on three different data sets available. Our best-fit models to one of the data sets allow for very efficient daynight energy redistribution in HD 189733b. The different constraints on molecular abundances confirm the presence of H20, CH4 , CO and CO 2 in HD 189733b. Our results also rule out the presence of a thermal inversion in this planet. The model constraints due to the different data sets indicate that the planetary atmosphere is variable, both, in its energy redistribution state and in the chemical abundances. The variability is evident in the data; some key observations with different instruments at the same wavelength differ at the - 2- level. If, on the other hand, the differences in data represent underestimated errors, and if all the data sets have to be reconciled simultaneously, then we are unable to make specific constraints on the molecular abundances or on the temperature profile, beyond identification of molecules and the presence or absence of a thermal inversion. For HD 209458b, we confirm and constrain a thermal inversion in the day-side atmosphere, and the data allows for very efficient day-night redistribution of energy. We report detection of CO, CH4 and CO 2 on the dayside of HD 209458b, along with placing an upper-limit on the amount of H2 0. We also report atmospheric models for three transiting exoplanets with limited data: TrES-2, HAT-P-7b, GJ 436b. For TrES-2 and HAT-P-7b, where only four observations each are available, we find that the data can be fit with models with and without thermal inversions, if we make no assumptions of chemical equilibrium. Finally, in this work, we report the first steps towards developing a parameter estimation procedure for exoplanetary atmospheres. We demonstrate with simulated data that our model can be used with a formal Bayesian parameter estimation algorithm, like MCMC, to place constraints on the atmospheric properties of hot Jupiters.
by Nikku, Madhusudhan.
Ph.D.
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Verrier, Patricia Eleanor. "The dynamics of planets in multistellar systems." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612466.
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Kipping, D. M. "The transits of extrasolar planets with moons." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1306758/.
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The search for extrasolar planets is strongly motivated by the goal of characterizing how frequent habitable worlds and life may be within the Galaxy. Whilst much effort has been spent on searching for Earth-like planets, large moons may also be common, temperate abodes for life as well. The methods to detect extrasolar moons, or “exomoons” are more subtle than their planetary counterparts and in this thesis I aim to provide a method to find such bodies in transiting systems, which offer the greatest potential for detection. Before one can search for the tiny perturbations to the planetary signal, an understanding of the planetary transit must be established. Therefore, in Chapters 3 to 5 I discuss the transit model and provide several new insights. Chapter 4 presents new analytic expressions for the times of transit minima and the transit duration, which will be critical in the later search for exomoons. Chapter 5 discusses two sources of distortion to the transit signal, namely blending (with a focus on the previously unconsidered self-blending scenario) and light curve smearing due to long integration times. I provide methods to compensate for both of these effects, thus permitting for the accurate modelling of the planetary transit light curve. In Chapter 6, I discuss methods to detect exomoons through their gravitational influence on the host planet, giving rise to transit timing and duration variations (TTV and TDV). The previously known TTV effect is updated with a new model and the associated critical problems are outlined. I then predict a new effect, TDV, which solves these problems, making exomoon detection viable. Chapter 7 presents a feasibility study for detecting habitable-zone exomoons with Kepler, where it is found that moons down to 0.2M⊕ are detectable. Finally, conclusions and future work are discussed in Chapter 8.
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Hoyer, Miranda Sergio David. "Search for unseen planets transit timing variations." Tesis, Universidad de Chile, 2012. http://www.repositorio.uchile.cl/handle/2250/111555.
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Doctor en Ciencias, Mención AstronomíaObserving the changes in the orbital period of transiting exoplanets produced by gravitational perturbations allows to detect unseen orbital companions in the system. With this technique,known asTransitTimingVariations(TTVs),itispossibletodetectperturbers down to Earth-like masses, overcoming the limits of current Radial Velocity searches. This PhDthesishasled to along termproject: TransitMonitoringin theSouth(TraMoS)project, which consists in a methodical and homogeneous monitoring of transiting exoplanets observable from the Southern Hemisphere with the goal of searching for orbital companions, and potentially finding Earth-mass planets. Aditionally, the cumulative light curves provide improvedvalues of thephysicalparameters of theplanets, such as orbitalinclination and radius, and from those absolute mass and mean planetary density, which are critical to our model understanding of thephysics of exoplanetary interiors and their evolution. Also, establishing thepresence orabsence of otherplanetashelpsdeterminethe architecture of multi-planetary systems, and therefore is key to discriminate between different models of formation and evolution of exoplanets. In thisThesisIpresent the observations and analysis of29 transits of4 exoplanets: OGLETR-111b, WASP-5b, WASP-4b and WASP-7b. Based on the analysis of the light curves of these exoplanets we refined the ephemeris and physical parameters of all these exoplanets. Based on the temporal analysis, we found no evidence of the presence of additional planets with masses larger than ∼10 Min those systems. We place strong limits in the mass of ~10 M⊕possible perturbers especially in the orbital resonances with the transiting planets. These results support the formation theories that predict a paucity of planetary companions to Jupiter-like planets.
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Jermyn, Adam Sean. "Turbulence and transport in stars and planets." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/278021.
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In this dissertation I have argued that the study of stars and gaseous planets has relied too heavily on simplifying assumptions. In particular, I have demonstrated that the assumptions of spherical symmetry, thermal equilibrium, dynamical equilibrium and turbulent anisotropy all hide interesting phenomena which make a true difference to the structure and evolution of these bodies. To begin I developed new theoretical tools for probing these phenomena, starting with a new model of turbulent motion which accounts for many different sources of anisotropy. Building on this I studied rotating convection zones and determined scaling relations for the magnitude of differential rotation. In slowly-rotating systems the differential rotation is characterised by a power law with exponent of order unity, while in rapidly-rotating systems this exponent is strongly suppressed by the rotation. This provides a full characterisation of the magnitude of differential rotation in gaseous convection zones, and is in reasonable agreement with a wide array of simulations and observations. I then focused on the convection zones of rotating massive stars and found them to exhibit significantly anisotropic heat fluxes. This results in significant deviations from spherical symmetry and ultimately in qualitatively enhanced circulation currents in their envelopes. Accordingly, these stars ought to live much longer and have a different surface temperature. This potentially resolves several outstanding questions such as the anomalously slow evolution of stars on the giant branch, the dispersion in the observed properties of giant stars and the difficulty stellar modelling has to form massive binary black holes. In the same vein I examined the convection zones of bloated hot Jupiters and discovered a novel feedback mechanism between non-equilibrium tidal dissipation and the thermal structure of their upper envelopes. This mechanism stabilises shallow radiative zones against the convective instability, which would otherwise take over early on in the planet's formation as it proceeds to thermal equilibrium. Hence tidal dissipation is dramatically enhanced, which serves to inject significant quantities of heat into the upper layers of the planet and causes it to inflate. This mechanism can explain most of the observed population of inflated planets. Finally, I studied material mixing in the outer layers of accreting stars and developed a method for relating the observed surface chemistry to the bulk and accreting chemistries. This enables the direct inference of properties of circumstellar material and accretion rates for a wide variety of systems.
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Portron, Stéphane. "Epicyclic gears dynamics and planets support conditions." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI061.
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Ce doctorat est issu d'un partenariat entre SAFRAN Transmission Systems et le laboratoire LaMCoS de l'INSA de Lyon et dans le cadre la chaire INSA-SAFRAN "Transmissions mécaniques innovantes pour l'aéronautique". L'introduction de trains planétaires dans les turbofans a récemment émergé comme une solution technologique prometteuse pour réduire la vitesse de rotation des aubes dans la prochaine génération de moteurs d'avions. Au vu des vitesses de rotation et des charges au cours du fonctionnement, les paliers hydrodynamiques apparaissent comme une solution intéressante puisque d'une part ils permettent de supporter une charge élevée à haute vitesse, et d'autre part ils apportent un amortissement significatif dans les systèmes mécaniques. Cette thèse a pour but de comprendre les couplages statiques et dynamiques entre les paliers hydrodynamiques et les engrènements dans les trains épicycloïdaux. Un modèle à paramètres concentrés du solaire, des satellites et de la couronne est couplé à un modèle éléments finis condensé du porte-satellite en utilisant les paliers hydrodynamiques comme interface. Les réactions paliers sont linéarisées autour de l'équilibre quasi-statique du système afin d'utiliser des algorithmes classiques pour l'intégration temporelle. L'élasticité des dentures aux interfaces d'engrènement est modélisée par une approche de type "tranches minces", pour laquelle une raideur élémentaire est attachée à chaque cellule de discrétisation le long de la ligne de contact. Des ensembles de déviations normales sont ajoutés aux cellules de discrétisation afin de prendre en compte les effets des erreurs d'assemblage et de fabrication, mais aussi des corrections de dentures. Le modèle est confronté à des résultats issus de la littérature afin de valider la précision du modèle, particulièrement par rapport au contenu fréquentiel des signaux de sortie de la simulation. Ce travail concerne deux aspects principaux: a) L'effet des corrections longitudinales de dentures sur le comportement statique et dynamique du train planétaire et b) L'influence des paliers hydrodynamiques comme supports des satellites par rapport à des paliers à éléments roulants. Une attention particulière est mise sur les propriétés de raideur et d'amortissement apportées par les paliers hydrodynamiquesThis PhD has been carried out within a partnership between SAFRAN Transmission Systems and the LaMCoS laboratory of INSA Lyon in the framework of the INSA-SAFRAN Chair on Innovative Mechanical Transmissions for Aeronautics. The introduction of planetary gears in turbofans has recently emerged as a promising technological solution to reduce fan rotational speeds in the next generation of aircraft engines. In view of the rotational speeds and loads, journal bearings appear as interesting since, beyond their load carrying capacity at high speeds, they bring significant damping in mechanical systems. The present work aims at understanding the static and dynamic couplings between journal bearings and gear meshes in epicyclic gears. Lumped parameters models of the sun-gear, planets and ring-gear are coupled with a condensed finite elements model of the carrier using the planets bearings as interface elements. The journal bearings reactions are linearized around the quasi-static equilibrium of the system in order to use classical algorithms for the time-step integration. The gear teeth elasticity at the mesh interfaces are modelled using a thin-slices approach with an elemental stiffness attached to each discrete cell on the lines of contact. Sets of normal deviations are added to the discrete cells to account for the effect of manufacturing and assembly errors, as well as toot modifications. A number of comparisons with results from the literature validate the precision of the model, especially regarding the frequency contents of the output signals of the simulation. This work focuses on two main aspects: a) the effect of tooth lead modifications on the static and dynamics of a planetary gear set and, b) the influence of journal bearings as planet supports compared with rolling elements bearings. Particular emphasis is placed on the stiffness and damping properties brought by journal bearings
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Gaudi, B. Scott. "Microlensing and the search for extrasolar planets /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488199501405399.
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Dressing, Courtney Danielle. "The Prevalence and Compositions of Small Planets." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17467474.
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This thesis describes three investigations of the galactic abundance and properties of small planets.
First, I revised the properties of the smallest Kepler target stars and searched their light curves for transits using a custom transit detection pipeline. Combining the detected population of 156 planet candidates (including one previously undetected candidate) with an empirical estimate of the search completeness based on transit injection and recovery simulations, I found occurrence rates of 0.24 (+0.18/-0.08) Earth-size planets (1− 1.5 Earth radii) and 0.21 (+0.11/-0.06) super-Earths (1.5−2 Earth radii) per M dwarf habitable zone. Consequently, the most probable distances to the nearest non-transiting and transiting potentially habitable planets are 2.6 ± 0.4 pc and 10.6 (+1.6/-1.8) pc, respectively.
Second, I conducted an adaptive optics imaging survey of 87 bright Kepler target stars with ARIES at the MMT to search for nearby stars that might be diluting the depths of the planetary transits. I identified visual companions within 1” for 5 stars, between 1” and 2” for 7 stars, and between 2” and 4” for 15 stars. For all stars observed, I placed limits (typically delta Ks = 5.3 at 1” and delta Ks = 5.7 at 2”) on the presence of undetected nearby stars.
Third, I investigated the composition of Kepler-93b, a 1.478 ± 0.019 Earth radius planet with a 4.7-day orbit around a bright (V = 10.2) asteroseismically-characterized host star with a mass of 0.911 ± 0.033 solar masses and a radius of 0.919 ± 0.011 solar radii. Based on two seasons of observations with HARPS-N at the Telescopio Nazionale Galileo and archival observations from Keck/HIRES, I found a mass of 4.02 ± 0.68 Earth masses and a density of 6.88 ± 1.18 g/cc. Comparing Kepler-93b to the other nine exoplanets smaller than 2.7 Earth radii with well-constrained parameters, I found that all dense exoplanets with masses of approximately 1 – 6 Earth masses are consistent with the same fixed ratio of iron to rock as the Earth and Venus. There are currently no such planets with masses greater than 7 Earth masses. Future measurements of the masses and radii of a larger sample of planets receiving a wider range of stellar insolations will reveal whether the fixed compositional model found for these seven highly-irradiated dense exoplanets extends to the full population of dense 1 – 6 Earth mass planets.Astronomy
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Langton, Jonathan. "Atmospheric dynamics on strongly irradiated Jovian planets /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2008. http://uclibs.org/PID/11984.
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Lewis, Nikole Kae. "Atmospheric Circulation of Eccentric Extrasolar Giant Planets." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/242352.
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This dissertation explores the three-dimensional coupling between radiative and dynamical processes in the atmospheres of eccentric extrasolar giant planets GJ436b, HAT-P-2b, and HD80606b. Extrasolar planets on eccentric orbits are subject to time-variable heating and probable non-synchronous rotation, which results in significant variations in global circulation and thermal patterns as a function of orbital phase. Atmospheric simulations for the low eccentricity (e=0.15) Neptune sized planet GJ436b reveal that when Neptune-like atmospheric compositions are assumed day/night temperature contrasts and equatorial jet speeds are significantly increased relative to models that assume a solar-like composition. Comparisons between our theoretical light curves and recent observations support a high metallicity atmosphere with disequilibrium carbon chemistry for GJ436b. The analysis of full-orbit light curve observations at 3.6 and 4.5 microns of the HAT-P-2 system reveal swings in the planet's temperature of more than 900 K during its significantly eccentric (e=0.5) orbit with a four to six hour offset between periapse passage and the peak of the planet's observed flux. Comparisons between our atmospheric model of HAT-P-2b and the observed light curves indicate an increased carbon to oxygen ratio in HAT-P-2b's atmosphere compared to solar values. Atmospheric simulations of the highly eccentric (e=0.9) HD80606b show that flash-heating events completely alter planetary thermal and jet structures and that assumptions about the rotation period of this planet could affect the shape of light curve observations near periapse. Our simulations of HD80606b also show the development an atmospheric shock on the nightside of the planet that is associated with an observable thermal signature in our theoretical light curves. The simulations and observations presented in this dissertation mark an important step in the exploration of atmospheric circulation on the more than 300 exoplanets known to possess significantly non-zero eccentricities.
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Moro-Martin, Maria A. "Signatures of planets in circumstellar debris disks." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/290124.
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Main sequence stars are commonly surrounded by debris disks, composed of cold dust continuously replenished by a reservoir of undetected dust-producing planetesimals. In the outer Solar System, Kuiper Belt (KB) objects produce dust by mutual or interstellar grain collisions. The orbital evolution of KB dust has been numerically modeled. Its equilibrium radial density distribution can be accurately estimated even though there are inherent uncertainties in the prediction of structure, owing to the chaotic dynamics of dust orbital evolution imposed by resonant gravitational perturbations of the planets. The particle size distribution of dust is greatly changed from the distribution at production, as a result of radiation forces and the perturbations of the planets. The contribution of KB dust to the population of interplanetary dust particles collected at Earth may be as low as a few percent. Gravitational scattering by giant planets creates an outflow of large grains. We quantify the characteristics of this large-particle outflow in different planetary architectures, discuss its implications for exo-planetary debris disks, and for the interpretation of in-situ dust detection experiments in space probes traveling in the outer Solar System. These outflows may contribute to the clearing of circumstellar debris in planetary systems, affecting the particle size distribution of their local ISM. In anticipation of future observations of unresolved debris disks with Spitzer, we are interested in studying how the structure carved by planets affects the shape of the disk's spectral energy distribution (SED), and consequently if the SED can be used to infer the presence of planets. We numerically calculate the equilibrium spatial density distributions and SEDs of dust disks originated by an outer belt of planetesimals (35-50 AU) in the presence of different planetary configurations, and for a representative sample of chemical compositions. The dynamical models are needed to estimate the enhancement of particles near the mean motion resonances with the planets, and to determine how many particles drift inside the planet's orbit. Based on the SEDs and predicted Spitzer colors we discuss what types of planetary systems can be distinguishable from one another.
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Sissa, Elena. "Observation of extrasolar planets at various ages." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3426311.
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The search and characterization of extrasolar planets is one of the main topics of current astronomy, with the ultimate goals of understanding the formation and evolution of planetary systems, the general conditions for the formation of life-friendly environments, and possibly detecting signature of extra-solar life.
In the last decades the research of extrasolar planets underwent a steep increase of interest and different methods of detection were developed.
Each of them has its own merit and lack in studying the extrasolar system architecture and the characteristics of extrasolar planets.
Stars and their planetary entourage form and grow together, at least in most cases, tied by the circumstellar disk.
A unique theory that can describe all the processes that happen between the protostellar cloud collapse and the final system stabilization is not available at the moment. Indirect methods are very useful to study more evolved systems, where the protoplanetary disk contribution is negligible, in their innermost regions.
On the other hand, direct imaging with high-contrast instruments offers the possibility to study the early phases of the planet formation, that are not accessible to other indirect methods of planets detection, and plays a key role in current planet formation theories.
This thesis focuses on the capabilities of direct imaging with SPHERE, the new high-contrast imager of VLT, in detecting planets at different stages of their evolution, coupled with radial velocities observations of old systems obtained from SARG, the old TNG echelle spectrograph.
Chapter 1 briefly introduces the planet formation and evolution theories with the most important exoplanets research methods.
Chapter 2 describes the SPHERE instrument used for the majority of the results presented in this thesis.
In Chapter 3 I present the case of four young objects. I exploit the SPHERE visible channel to study Z CMa jets, and the near-IR channel for HD 100546 and T Cha, looking for the presence of planets. At the same time, I was able to study in detail the circumplanetary disk of HD 100546 in a quite wide spectral range: in the dedicated Section I show that the system brightest structures suggest the presence of at least three gaps in the inner regions of the disk, coupled with other structures, such as spiral arms.
I detected a diffuse source at the location of the claimed planet HD 100546 b, but the nature of this emission is, however, still unknown.
Lastly, LkCa15 was studied both in the visible and in the near-IR of SPHERE.
In Chapter 4 I present the study of the accretion signature in a few objects. GQ Lup b accretion was observed both in H_alpha and in Paschen beta, exploiting all three SPHERE subsystems.
Two systems that have already cleaned out their surroundings from gas and dust are presented in Chapter 5: HIP 80591 and HD 65426. In the latter, I first found out that one companion candidate had high probability to be bound to the star due to its position and it spectral features. These findings were later confirmed by a deeper analysis and follow up observations that demonstrate HD 65426 b, the companion I studied, is a warm Jupiter-like planet with mass between 6 and 12 M_J.
In Chapter 6, I study the chromospheric activity in older binary stars in order to detect a radial velocity signal hidden by the Doppler shift induced by the activity. I found out that Ha-excess, an index based on the Halpha line, is a good indicator of the star activity when the log_RHK' index is not available and can be used also to infer stellar ages in case of stars younger then 1.5 Gyr. Moreover, HD 76073 B shows a high radial velocities scatter that can be explained by the presence of a low-mass companion (Sissa et al. 2016).
Finally, in Chapter 7 I give the conclusions and explain future prospects.
Appendixes are dedicated to the more technical aspects of my work, that were needed to improve instrument capabilities and data reduction, and to better defining the instrument set-ups needed to achieve different scientific aims.La ricerca e la caratterizzazione dei pianeti extrasolari è uno dei maggiori campi di ricerca dell’astronomia attuale, con lo scopo ultimo di capire i meccanismi di formazione e di evoluzione dei sistemi planetari, le condizioni che permettono la formazione di ambienti adatti alla vita, e di trovare le prove di vita extra-solare. Negli ultimi decenni, la ricerca dei pianeti extrasolari ha visto un rapido aumento di interesse, e sono state cosí sviluppate nuove metodologie di ricerca. Ognuna di esse ha aspetti positivi e negativi per lo studio dell’architettura dei sistemi extrasolari e la caratterizzazione dei pianeti. Le stelle e il loro entourage planetario si formano e crescono assieme, per lo meno nella maggioranza dei casi, legate dal disco circumstellare. Al momento manca una teoria universale che possa descrivere tutti i processi che accadono tra le fasi del collasso della nube protostellare e la stabilizzazione finale del sistema. I metodi indiretti sono molto utili per studiare le zone interne dei sistemi più evoluti, nei quali il contributo del disco protoplanetario è trascurabile. Dall’altro lato, la tecnica dell’imaging diretto con strumenti ad alto contrasto offre la possibilità di studiare le prime fasi della formazione planetaria, non accessibili con altri metodi indiretti, e gioca un ruolo fondamentale per le attuali teorie di formazione planetaria. Questa tesi si focalizza sulle capacità dell’imaging diretto ottenuto con SPHERE, il nuovo strumento ad alto contrasto del VLT, nel rivelare pianeti in diversi stadi della loro evoluzione, e presenta uno studio complementare di sistemi vecchi basato sulle osservazioni delle velocità radiali con SARG, il vecchio spettrografo echelle del TNG. Il Capitolo 1 introduce brevemente le teorie di formazione ed evoluzione dei pianeti con i più importanti metodi di ricerca. Il Capitolo \ref{sec:sphere} descrive SPHERE, lo strumento usato per la maggior parte dei risultati presentati in questa tesi. Nel Capitolo 3 presento il caso di quattro oggetti giovani. Ho sfruttato il canale visibile di SPHERE per studiare i jet di Z CMa, e il canale nel vicino infrarosso per HD 100546 e T Cha, cercando segnali della presenza di pianeti. Allo stesso tempo, ho potuto studiare in dettaglio il disco circumstellare di HD 100546 in un intervallo spettrale relativamente ampio: nella sezione ad esso dedicata mostra che le strutture più brillanti del sistema suggeriscono la presenza di almeno tre regioni vuote nelle zone interne del disco, assieme ad altre strutture, come ad esempio bracci a spirale. Ho anche rilevato la presenza di una sorgente diffusa nella posizione attesa per il potenziale pianeta b, ma la natura di questa emissione è, tuttavia, ancora sconosciuta. Infine, LkCa 15 è stato studiato sia nel canale visibile che in quello del vicino infrarosso di SPHERE. Nel Capitolo 4 presento lo studio dei segni distintivi di accrescimento in un gruppo di oggetti. L’accrescimento di GQ Lup b è stato osservato sia in H_alpha che il Paschen beta, sfruttando tutti e tre i sottosistemi di SPHERE. Due sistemi i cui dintorni sono già stati ripuliti dal gas e dalla polvere sono presentati nel Capitolo 5: HIP 80591 e HIP 65426. In quest’ultimo, ho scoperto che uno dei candidati compagni aveva un’alta probabilità di essere legato alla stella a causa della sua posizione e delle sue caratteristiche spettrali. Queste conclusioni sono state poi confermate da un’analisi approfondita e da ulteriori osservazioni che hanno dimostrato che quel compagno, HD 65426 b, è un pianeta gioviano caldo con massa compresa tra 6 e 12 M_J. Nel Capitolo 6, studio l’attività cromosferica in stelle binarie vecchie allo scopo di identificare un segnale nelle velocità radiali nascosto dallo spostamento Doppler indotto dall’attività. Ho scoperto che Ha-excess, un indice basato sulla riga \Ha, è un buon indicatore dell’attività stellare quando l’indice \RHK\ non è disponibile e può essere anche usato per derivare l’età delle stelle nel caso siano più giovani di 1.5 Gyr. Inoltre, HD 76037 B mostra una variazione elevata delle velocità radiali che puo’ essere spiegata con la presenza di un compagno di piccola massa (Sissa et al. 2017) Infine, nel Capitolo 7 fornisco le conclusioni del lavoro ed espongo sviluppi futuri. Le appendici sono dedicate agli aspetti più tecnici del mio lavoro, che sono stati necessari per migliorare le capacità dello strumento e la riduzione dei dati, e per definire al meglio i set-up necessari allo strumento per raggiungere i differenti scopi scientifici.
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Wahl, Sean M., William B. Hubbard, and Burkhard Militzer. "TIDAL RESPONSE OF PRELIMINARY JUPITER MODEL." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622055.
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In anticipation of improved observational data for Jupiter's gravitational field, from the Juno spacecraft, we predict the static tidal response for a variety of Jupiter interior models based on ab initio computer simulations of hydrogen-helium mixtures. We calculate hydrostatic-equilibrium gravity terms, using the non-perturbative concentric Maclaurin Spheroid method that eliminates lengthy expansions used in the theory of figures. Our method captures terms arising from the coupled tidal and rotational perturbations, which we find to be important for a rapidly rotating planet like Jupiter. Our predicted static tidal Love number, k(2) = 0.5900, is similar to 10% larger than previous estimates. The value is, as expected, highly correlated with the zonal harmonic coefficient J(2), and is thus nearly constant when plausible changes are made to the interior structure while holding J(2) fixed at the observed value. We note that the predicted static k(2) might change, due to Jupiter's dynamical response to the Galilean moons, and find reasons to argue that the change may be detectable-although we do not present here a theory of dynamical tides for highly oblate Jovian planets. An accurate model of Jupiter's tidal response will be essential for interpreting Juno observations and identifying tidal signals from effects of other interior dynamics of Jupiter's gravitational field.
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Komacek, Thaddeus D., and Dorian S. Abbot. "EFFECT OF SURFACE-MANTLE WATER EXCHANGE PARAMETERIZATIONS ON EXOPLANET OCEAN DEPTHS." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622455.
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Terrestrial exoplanets in the canonical habitable zone may have a variety of initial water fractions due to random volatile delivery by planetesimals. If the total planetary water complement is high, the entire surface may be covered in water, forming a "waterworld." On a planet with active tectonics, competing mechanisms act to regulate the abundance of water on the surface by determining the partitioning of water between interior and surface. Here we explore how the incorporation of different mechanisms for the degassing and regassing of water changes the volatile evolution of a planet. For all of the models considered, volatile cycling reaches an approximate steady state after similar to 2 Gyr. Using these steady. states, we find that if volatile cycling is either solely dependent on temperature or seafloor pressure, exoplanets require a high abundance (greater than or similar to 0.3% of total mass) of water to have fully inundated surfaces. However, if degassing is more dependent on seafloor pressure and regassing mainly dependent on mantle temperature, the degassing rate is relatively large at late times and a steady. state between degassing and regassing is reached with a substantial surface water fraction. If this hybrid model is physical, super-Earths with a total water fraction similar to that of the Earth can become waterworlds. As a result, further understanding of the processes that drive volatile cycling on terrestrial planets is needed to determine the water fraction at which they are likely to become waterworlds.
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Ortiz, Mauricio, Sabine Reffert, Trifon Trifonov, Andreas Quirrenbach, David S. Mitchell, Grzegorz Nowak, Esther Buenzli, et al. "Precise radial velocities of giant stars." EDP SCIENCES S A, 2016. http://hdl.handle.net/10150/622444.
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Context. For over 12 yr, we have carried out a precise radial velocity (RV) survey of a sample of 373 G- and K-giant stars using the Hamilton Echelle Spectrograph at the Lick Observatory. There are, among others, a number of multiple planetary systems in our sample as well as several planetary candidates in stellar binaries. Aims. We aim at detecting and characterizing substellar and stellar companions to the giant star HD 59686 A (HR 2877, HIP 36616). Methods. We obtained high-precision RV measurements of the star HD 59686 A. By fitting a Keplerian model to the periodic changes in the RVs, we can assess the nature of companions in the system. To distinguish between RV variations that are due to non-radial pulsation or stellar spots, we used infrared RVs taken with the CRIRES spectrograph at the Very Large Telescope. Additionally, to characterize the system in more detail, we obtained high-resolution images with LMIRCam at the Large Binocular Telescope. Results. We report the probable discovery of a giant planet with a mass of m(p) sin i = 6.92(-0.24)(+0.18) M-Jup orbiting at a(p) = 1.0860(-0.0007)(+0.0006) aufrom the giant star HD 59686 A. In addition to the planetary signal, we discovered an eccentric (e(B) = 0.729(-0.003)(+0.004)) binary companionwith a mass of m(B) sin i = 0.5296(-0.0008)(+0.0011) M-circle dot orbiting at a close separation from the giant primary with a semi-major axis of a(B) = 13.56(-0.14)(+0.18) au. Conclusions. The existence of the planet HD 59686 Ab in a tight eccentric binary system severely challenges standard giant planet formation theories and requires substantial improvements to such theories in tight binaries. Otherwise, alternative planet formation scenarios such as second-generation planets or dynamical interactions in an early phase of the system's lifetime need to be seriously considered to better understand the origin of this enigmatic planet.
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Tan, Xianyu, and Adam P. Showman. "Effects of Latent Heating on Atmospheres of Brown Dwarfs and Directly Imaged Planets." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624643.
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The growing number of observations of brown dwarfs (BDs) has provided evidence for strong atmospheric circulation on these objects. Directly imaged planets share similar observations and can be viewed as low-gravity versions of BDs. Vigorous condensate cycles of chemical species in their atmospheres are inferred by observations and theoretical studies, and latent heating associated with condensation is expected to be important in shaping atmospheric circulation and influencing cloud patchiness. We present a qualitative description of the mechanisms by which condensational latent heating influences circulation, and then illustrate them using an idealized general circulation model that includes a condensation cycle of silicates with latent heating and molecular weight effect due to the rainout of the condensate. Simulations with conditions appropriate for typical T dwarfs exhibit the development of localized storms and east-west jets. The storms are spatially inhomogeneous, evolving on a timescale of hours to days and extending vertically from the condensation level to the tropopause. The fractional area of the BD covered by active storms is small. Based on a simple analytic model, we quantitatively explain the area fraction of moist plumes and show its dependence on the radiative timescale and convective available potential energy (CAPE). We predict that if latent heating dominates cloud formation processes, the fractional coverage area of clouds decreases as the spectral type goes through the L/T transition from high to lower effective temperature. This is a natural consequence of the variation of the radiative timescale and CAPE with the spectral type.
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Costa, André Izidoro Ferreira da [UNESP]. "Estudos da formação de planetas terrestres." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/102493.
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costa_aif_dr_guara.pdf: 4600583 bytes, checksum: 3d77d0ac5008ebea1c760741e6b7ed43 (MD5)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O estudo da formação de planetas terrestres no Sistema Solar, é crucial para compre- endermos como outros sistemas planetários formam e também inferir as condições que poderiam ter influenciado a origem e evolução de vida na Terra. Esta Tese de douto- rado apresenta um estudo numérico da formação de planetas terrestres. Nosso objetivo principal é analisar o último estágio da formação desses planetas no Sistema Solar, em particular, a formação de Marte e a origem da água da Terra. Esses dois pontos têm intrigado cientistas ao longo de muitos anos. Enquanto que o planeta produzido ao redor de 1.5 UA é, em geral, muito mais massivo do que Marte, na grande parte das simulações, a origem da água da Terra é outro tema de intenso debate. Em vista disso, nós desenvol- vemos um cenário considerando uma depleção local de massa, no disco protoplanetário, a fim de analisarmos a origem da baixa massa de Marte, e também usamos um modelo composto para estudarmos a origem da água da Terra. Este trabalho apresenta um grande número de simulações numéricas explorando uma diversidade de parâmetros do sistema. Entre os principais podemos citar as variadas configurações de planetas gigantes, discos com diferentes perfis de densidade superficial de massa e modelos de distribuição de água. Nós também apresentamos um estudo dos efeitos de ressonâncias seculares nesses discos protoplanetários. Os principais resultados desses experimentos apontam a possibilidade da formação de planetas similares a Marte ao redor de 1.5 UA, especialmente, quando é considerado uma escala de depleção local, no disco protoplanetário, moderadamente alta (50-75%), localizada ao redor de 1.5 UA. Isto é observado juntamente com a formação de planetas do tipo Terra, em torno de 1 UA do Sol, com substanciais...
The study of terrestrial planet formation in the Solar System is crucial to understand how other planetary systems form and to infer the conditions that favored the origin and evolution of life on Earth. In this Thesis we present a numerical study of the accretion of terrestrial planets. Our main goal is study the late stage of the terrestrial planet accretion in the Solar System, especially the formation of Mars and the origin of Earth’s water. These two points have intrigued scientists for many years. Whereas the planet formed around Mars’ semimajor axis is, in general, much more massive than Mars, the origin of Earth’s water is a matter of intense debate. In view of that, we have developed a scenario considering a local depletion in the density of the protosolar nebula in order to analyze the low mass of Mars, and also explored a compound model of water distribution to study the origin of Earth’s water. We have carried out extensive numerical simulations of the formation of terrestrial planets in protoplanetary disks exploring a large variety of parameters of the system, as different giant planet configurations, surface density profiles and water distribution models. We also have presented a study of the effects of secular resonances on the evolution of these protoplanetary disks. Our main results point to the possibility of the formation of Mars-sized bodies around 1.5 AU, especifically when is considered a scale of the disk local mass-depletion moderately high (50-75%) around 1.5 AU, as well as Earth-sized planets can form around 1 AU with substantial amount of water. Regarding the origin of Earth’s water, we find that the compound model incorporating both the principal endogenous and exogenous theories, play an important role by... (Complete abstract click electronic access below)
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Costa, André Izidoro Ferreira da. "Estudos da formação de planetas terrestres /." Guaratinguetá, 2013. http://hdl.handle.net/11449/102493.
Full textAbstract:
Orientador: Othon Cabo WinterCoorientador: Massayoshi Tsuchida
Banca: Tadashi Yokoyama
Banca: Nelson Callegari Junior
Banca: Roberto Vieira Martins
Banca: Fernando Virgilio Roig
Resumo: O estudo da formação de planetas terrestres no Sistema Solar, é crucial para compre- endermos como outros sistemas planetários formam e também inferir as condições que poderiam ter influenciado a origem e evolução de vida na Terra. Esta Tese de douto- rado apresenta um estudo numérico da formação de planetas terrestres. Nosso objetivo principal é analisar o último estágio da formação desses planetas no Sistema Solar, em particular, a formação de Marte e a origem da água da Terra. Esses dois pontos têm intrigado cientistas ao longo de muitos anos. Enquanto que o planeta produzido ao redor de 1.5 UA é, em geral, muito mais massivo do que Marte, na grande parte das simulações, a origem da água da Terra é outro tema de intenso debate. Em vista disso, nós desenvol- vemos um cenário considerando uma depleção local de massa, no disco protoplanetário, a fim de analisarmos a origem da baixa massa de Marte, e também usamos um modelo composto para estudarmos a origem da água da Terra. Este trabalho apresenta um grande número de simulações numéricas explorando uma diversidade de parâmetros do sistema. Entre os principais podemos citar as variadas configurações de planetas gigantes, discos com diferentes perfis de densidade superficial de massa e modelos de distribuição de água. Nós também apresentamos um estudo dos efeitos de ressonâncias seculares nesses discos protoplanetários. Os principais resultados desses experimentos apontam a possibilidade da formação de planetas similares a Marte ao redor de 1.5 UA, especialmente, quando é considerado uma escala de depleção local, no disco protoplanetário, moderadamente alta (50-75%), localizada ao redor de 1.5 UA. Isto é observado juntamente com a formação de planetas do tipo Terra, em torno de 1 UA do Sol, com substanciais... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The study of terrestrial planet formation in the Solar System is crucial to understand how other planetary systems form and to infer the conditions that favored the origin and evolution of life on Earth. In this Thesis we present a numerical study of the accretion of terrestrial planets. Our main goal is study the late stage of the terrestrial planet accretion in the Solar System, especially the formation of Mars and the origin of Earth's water. These two points have intrigued scientists for many years. Whereas the planet formed around Mars' semimajor axis is, in general, much more massive than Mars, the origin of Earth's water is a matter of intense debate. In view of that, we have developed a scenario considering a local depletion in the density of the protosolar nebula in order to analyze the low mass of Mars, and also explored a compound model of water distribution to study the origin of Earth's water. We have carried out extensive numerical simulations of the formation of terrestrial planets in protoplanetary disks exploring a large variety of parameters of the system, as different giant planet configurations, surface density profiles and water distribution models. We also have presented a study of the effects of secular resonances on the evolution of these protoplanetary disks. Our main results point to the possibility of the formation of Mars-sized bodies around 1.5 AU, especifically when is considered a scale of the disk local mass-depletion moderately high (50-75%) around 1.5 AU, as well as Earth-sized planets can form around 1 AU with substantial amount of water. Regarding the origin of Earth's water, we find that the compound model incorporating both the principal endogenous and exogenous theories, play an important role by... (Complete abstract click electronic access below)
Doutor
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Komacek, Thaddeus D., and Andrew N. Youdin. "Structure and Evolution of Internally Heated Hot Jupiters." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/625158.
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Hot Jupiters receive strong stellar irradiation, producing equilibrium temperatures of 1000-2500 K. Incoming irradiation directly heats just their thin outer layer, down to pressures of similar to 0.1 bars. In standard irradiated evolution models of hot Jupiters, predicted transit radii are too small. Previous studies have shown that deeper heating-at a small fraction of the heating rate from irradiation-can explain observed radii. Here we present a suite of evolution models for HD 209458b, where we systematically vary both the depth and intensity of internal heating, without specifying the uncertain heating mechanism(s). Our models start with a hot, high-entropy planet whose radius decreases as the convective interior cools. The applied heating suppresses this cooling. We find that very shallow heating-at pressures of 1-10 bars-does not significantly suppress cooling, unless the total heating rate is greater than or similar to 10% of the incident stellar power. Deeper heating, at 100 bars, requires heating at only 1% of the stellar irradiation to explain the observed transit radius of 1.4R(Jup) after 5 Gyr of cooling. In general, more intense and deeper heating results in larger hot-Jupiter radii. Surprisingly, we find that heat deposited at 10(4) bars-which is exterior to approximate to 99% of the planet's mass-suppresses planetary cooling as effectively as heating at the center. In summary, we find that relatively shallow heating is required to explain the radii of most hot Jupiters, provided that this heat is applied early and persists throughout their evolution.
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Cauley, P. Wilson, Seth Redfield, Adam G. Jensen, and Travis Barman. "VARIATION IN THE PRE-TRANSIT BALMER LINE SIGNAL AROUND THE HOT JUPITER HD 189733B." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621234.
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As followup to our recent detection of a pre-transit signal around HD 189733 b, we obtained full pre-transit phase coverage of a single planetary transit. The pre-transit signal is again detected in the Balmer lines but with variable strength and timing, suggesting that the bow shock geometry reported in our previous work does not describe the signal from the latest transit. We also demonstrate the use of the Ca II H and K residual core flux as a proxy for the stellar activity level throughout the transit. A moderate trend is found between the pre-transit absorption signal in the 2013 data and the Ca II H flux. This suggests that some of the 2013 pre-transit hydrogen absorption can be attributed to varying stellar activity levels. A very weak correlation is found between the Ca II H core flux and the Balmer line absorption in the 2015 transit, hinting at a smaller contribution from stellar activity compared to the 2013 transit. We simulate how varying stellar activity levels can produce changes in the Balmer line transmission spectra. These simulations show that the strength of the 2013 and 2015 pre-transit signals can be reproduced by stellar variability. If the pre-transit signature is attributed to circumplanetary material, its evolution in time can be described by accretion clumps spiraling toward the star, although this interpretation has serious limitations. Further high-cadence monitoring at H alpha is necessary to distinguish between true absorption by transiting material and short-term variations in the stellar activity level.
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Biller, Beth A., Johanna Vos, Esther Buenzli, Katelyn Allers, Mickaël Bonnefoy, Benjamin Charnay, Bruno Bézard, et al. "Simultaneous Multiwavelength Variability Characterization of the Free-floating Planetary-mass Object PSO J318.5−22." IOP PUBLISHING LTD, 2018. http://hdl.handle.net/10150/627034.
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We present simultaneous Hubble Space Telescope (HST) WFC3+Spitzer IRAC variability monitoring for the highly variable young (similar to 20 Myr) planetary-mass object PSO J318.5-22. Our simultaneous HST + Spitzer observations covered approximately two rotation periods with Spitzer and most of a rotation period with the HST. We derive a period of 8.6. +/-. 0.1 hr from the Spitzer light curve. Combining this period with the measuredvsinifor this object, we find an inclination of 56 degrees.2. +/-. 8 degrees.1. We measure peak-to-trough variability amplitudes of 3.4%. +/-. 0.1% for Spitzer Channel 2 and 4.4%-5.8% (typical 68% confidence errors of similar to 0.3%) in the near-IR bands (1.07-1.67 mu m) covered by the WFC3 G141 prism-the mid-IR variability amplitude for PSO J318.5-22 is one of the highest variability amplitudes measured in the mid-IR for any brown dwarf or planetary-mass object. Additionally, we detect phase offsets ranging from 200 degrees to 210 degrees (typical error of similar to 4 degrees) between synthesized near-IR light curves and the Spitzer mid-IR light curve, likely indicating depth-dependent longitudinal atmospheric structure in this atmosphere. The detection of similar variability amplitudes in wide spectral bands relative to absorption features suggests that the driver of the variability may be inhomogeneous clouds (perhaps a patchy haze layer over thick clouds), as opposed to hot spots or compositional inhomogeneities at the top-of-atmosphere level.