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Spitzer observations of a gravitationally lensed quasar, QSO 2237+0305May 08 2009The four-image gravitationally lensed quasar QSO 2237+0305 is microlensed by stars in the lens galaxy. The amplitude of microlensing variability can be used to infer the relative size of the quasar as a function of wavelength; this provides a test of ... More

Finding White Dwarfs with Transit SearchesMar 20 2003Apr 18 2003We make predictions for the rate of discovery of eclipsing white dwarf-main sequence (WD-MS) binaries in terrestrial-planet transit searches, taking the planned Kepler and Eddington missions as examples. We use a population synthesis model to characterize ... More

Photon Damping of Waves in Accretion DisksMay 28 1998MHD turbulence is generally believed to have two important functions in accretion disks: it transports angular momentum outward, and the energy in its shortest wavelength modes is dissipated into the heat that the disks radiate. In this paper we examine ... More

Analytic Lightcurves for Planetary Transit SearchesOct 03 2002We present exact analytic formulae for the eclipse of a star described by quadratic or nonlinear limb darkening. In the limit that the planet radius is less than a tenth of the stellar radius, we show that the exact lightcurve can be well approximated ... More

Imaging a Quasar Accretion Disk with MicrolensingMay 10 1999We show how analysis of a quasar high-magnification microlensing event may be used to construct a map of the frequency-dependent surface brightness of the quasar accretion disk. The same procedure also allows determination of the disk inclination angle, ... More

Quasar Accretion Disks Are Strongly InhomogeneousDec 14 2010Active galactic nuclei (AGN) have been observed to vary stochastically with 10-20 rms amplitudes over a range of optical wavelengths where the emission arises in an accretion disk. Since the accretion disk is unlikely to vary coherently, local fluctuations ... More

A Fast New Public Code for Computing Photon Orbits in a Kerr SpacetimeMar 03 2009Relativistic radiative transfer problems require the calculation of photon trajectories in curved spacetime. We present a novel technique for rapid and accurate calculation of null geodesics in the Kerr metric. The equations of motion from the Hamilton-Jacobi ... More

Transit timing to first order in eccentricitySep 04 2015Apr 27 2016Characterization of transiting planets with transit timing variations (TTVs) requires understanding how to translate the observed TTVs into masses and orbital elements of the planets. This can be challenging in multi-planet transiting systems, but fortunately ... More

APOSTLE: Longterm Transit Monitoring and Stability Analysis of XO-2bApr 21 2013The Apache Point Survey of Transit Lightcurves of Exoplanets (APOSTLE) observed 10 transits of XO-2b over a period of three years. We present measurements which confirm previous estimates of system parameters like the normalized semi-major axis (a/R_{*}), ... More

APOSTLE: Eleven Transit Observations of TrES-3bNov 29 2012The Apache Point Survey of Transit Lightcurves of Exoplanets (APOSTLE) observed eleven transits of TrES-3b over two years in order to constrain system parameters and look for transit timing and depth variations. We describe an updated analysis protocol ... More

Magnetic Stress at the Marginally Stable Orbit: Altered Disk Structure, Radiation, and Black Hole Spin EvolutionAug 05 1999Magnetic connections to the plunging region can exert stresses on the inner edge of an accretion disk around a black hole. We recompute the relativistic corrections to the thin-disk dynamics equations when these stresses take the form of a time-steady ... More

Transit Timing and Duration Variations for the Discovery and Characterization of ExoplanetsJun 29 2017Jul 24 2017Transiting exoplanets in multi-planet systems have non-Keplerian orbits which can cause the times and durations of transits to vary. The theory and observations of transit timing variations (TTV) and transit duration variations (TDV) are reviewed. Since ... More

Volume change under drillingJan 17 2001Jan 11 2003Given a hyperbolic 3-manifold M containing an embedded closed geodesic, we estimate the volume of a complete hyperbolic metric on the complement of the geodesic in terms of the geometry of M. As a corollary, we show that the smallest volume orientable ... More

Measurement of planet masses with transit timing variations due to synodic "chopping" effectsOct 31 2014Gravitational interactions between planets in transiting exoplanetary systems lead to variations in the times of transit that are diagnostic of the planetary masses and the dynamical state of the system. Here we show that synodic "chopping" contributions ... More

APOGEE/Kepler Overlap Yields Orbital Solutions for a Variety of Eclipsing BinariesJun 28 2019Spectroscopic Eclipsing Binaries (SEBs) are fundamental benchmarks in stellar astrophysics and today are observed in breathtaking detail by missions like TESS, Kepler, and APOGEE. We develop a methodology for simultaneous analysis of high precision Kepler ... More

Inverting Phase Functions to Map ExoplanetsMar 25 2008We describe how to generate a longitudinal brightness map for a tidally locked exoplanet from its phase function light curve. We operate under a number of simplifying assumptions, neglecting limb darkening/brightening, star spots, detector ramps, as well ... More

Transit timing variations for planets near eccentricity-type mean motion resonancesSep 28 2015Apr 28 2016We derive the transit timing variations (TTVs) of two planets near a second order mean motion resonance on nearly circular orbits. We show that the TTVs of each planet are given by sinusoids with a frequency of $j n_2-(j-2)n_1$, where $j \ge 3$ is an ... More

Developments in Planet Detection using Transit Timing VariationsDec 15 2006In a transiting planetary system, the presence of a second planet will cause the time interval between transits to vary. These transit timing variations (TTV) are particularly large near mean-motion resonances and can be used to infer the orbital elements ... More

The Quasiperiodic Automated Transit Search AlgorithmOct 18 2012We present a new algorithm for detecting transiting extrasolar planets in time-series photometry. The Quasiperiodic Automated Transit Search (QATS) algorithm relaxes the usual assumption of strictly periodic transits by permitting a variable, but bounded, ... More

Exoplanet Mapping RevealedJun 27 2008One of the most exciting results of the Spitzer era has been the ability to construct longitudinal brightness maps from the infrared phase variations of hot Jupiters. We presented the first such map in Knutson et al. (2007), described the mapping theory ... More

An analysis of the transit times of TrES-1bSep 22 2005Nov 08 2005The presence of a second planet in a known, transiting-planet system will cause the time between transits to vary. These variations can be used to constrain the orbital elements and mass of the perturbing planet. We analyse the set of transit times of ... More

A limit on the presence of Earth-mass planets around a Sun-like starOct 05 2006We present a combined analysis of all publicly available, visible HST observations of transits of the planet HD 209458b. We derive the times of transit, planet radius, inclination, period, and ephemeris. The transit times are then used to constrain the ... More

Discovery and Characterization of Kepler-36bMay 13 2019We describe the circumstances that led to the discovery of Kepler-36b, and the subsequent characterization of its host planetary system. The Kepler-36 system is remarkable for its physical properties: the close separation of the planets, the contrasting ... More

A Model for Thermal Phase Variations of Circular and Eccentric ExoplanetsNov 01 2010We present a semi-analytic model atmosphere for close-in exoplanets that captures the essential physics of phase curves: orbital and viewing geometry, advection, and re-radiation. We calibrate the model with the well-characterized transiting planet, HD ... More

The Statistics of Albedo and Heat Recirculation on Hot ExoplanetsDec 30 2009Dec 20 2010[Abridged] If both the day-side and night-side effective temperatures of a planet can be measured, it is possible to estimate its Bond albedo, 0<A_B<1, as well as its day-night heat redistribution efficiency, 0<epsilon<1. We attempt a statistical analysis ... More

EXOFAST: A fast exoplanetary fitting suite in IDLJun 25 2012Jan 31 2013We present EXOFAST, a fast, robust suite of routines written in IDL which is designed to fit exoplanetary transits and radial velocity variations simultaneously or separately, and characterize the parameter uncertainties and covariances with a Differential ... More

Viewing the Shadow of the Black Hole at the Galactic CenterDec 14 1999In recent years, the evidence for the existence of an ultra-compact concentration of dark mass associated with the radio source Sgr A* in the Galactic Center has become very strong. However, an unambiguous proof that this object is indeed a black hole ... More

Keck Mid-Infrared Imaging of the QSO 2237+0305Jul 18 2000Using the Long Wavelength Spectrometer on Keck I, we have imaged the gravitationally lensed radio quiet quasi-stellar object (QSO) 2237+0305 at 8.9 and 11.7 microns for the first time. The mid-infrared flux ratios are inconsistent with the optical flux ... More

Planet-Planet Occultations in TRAPPIST-1 and Other Exoplanet SystemsNov 15 2017We explore the occurrence and detectability of planet-planet occultations (PPOs) in exoplanet systems. These are events during which a planet occults the disk of another planet in the same system, imparting a small photometric signal as its thermal or ... More

Spectral Eclipse TimingNov 19 2015We utilize multi-dimensional simulations of varying equatorial jet strength to predict wavelength dependent variations in the eclipse times of gas-giant planets. A displaced hot-spot introduces an asymmetry in the secondary eclipse light curve that manifests ... More

Polarization from magnetized accretion discs: II. The effects of absorption opacity on Faraday rotationDec 17 1996Equipartition magnetic fields can dramatically affect the polarization of radiation emerging from accretion disk atmospheres in active galactic nuclei. We extend our previous work on this subject by exploring the interaction between Faraday rotation and ... More

The Impact of Circumplantary Jets on Transit Spectra and Timing Offsets for Hot-JupitersOct 19 2011We present theoretical wavelength-dependent transit light curves for the giant planet HD209458b based on a number of state of the art 3D radiative hydrodynamical models. By varying the kinematic viscosity in the model we calculate observable signatures ... More

Continuum Spectra of Quasar Accretion Disk ModelsDec 11 1997We have calculated the spectrum and polarization of a standard thin accretion disk with parameters appropriate for a bright quasar. This model improves upon previous work by including ultraviolet metal line opacities, assumed for now to be in LTE. Though ... More

Millimeter Flares and VLBI Visibilities from Relativistic Simulations of Magnetized Accretion onto the Galactic Center Black HoleSep 01 2009The recent VLBI observation of the Galactic center black hole candidate Sgr A* at 1.3mm shows source structure on event-horizon scales. This detection enables a direct comparison of the emission region with models of the accretion flow onto the black ... More

The size of the jet launching region in M87Sep 27 2011Feb 02 2012The supermassive black hole candidate at the center of M87 drives an ultra-relativistic jet visible on kiloparsec scales, and its large mass and relative proximity allow for event horizon scale imaging with very long baseline interferometry at millimeter ... More

Radiative Models of Sagittarius A* and M87 from Relativistic MHD SimulationsFeb 02 2012Ongoing millimeter VLBI observations with the Event Horizon Telescope allow unprecedented study of the innermost portion of black hole accretion flows. Interpreting the observations requires relativistic, time-dependent physical modeling. We discuss the ... More

Robust Transiting Exoplanet Radii in the Presence of Starspots from Ingress and Egress DurationsJul 13 2018We typically measure the radii of transiting exoplanets from the transit depth, which is given by the ratio of cross-sectional areas of the planet and star. However, if a star has dark starspots (or bright regions) distributed throughout the transit chord, ... More

Two-Dimensional Hydrodynamic Simulations of Convection in Radiation-Dominated Accretion DisksMay 09 2001The standard equilibrium for radiation-dominated accretion disks has long been known to be viscously, thermally, and convectively unstable, but the nonlinear development of these instabilities---hence the actual state of such disks---has not yet been ... More

Kepler-62f: Kepler's First Small Planet in the Habitable Zone, but Is It Real?May 14 2019May 15 2019Kepler-62f is the first exoplanet small enough to plausibly have a rocky composition orbiting within the habitable zone (HZ) discovered by the Kepler Mission. The planet is 1.4 times the size of the Earth and has an orbital period of 267 days. At the ... More

Evidence for Large Temperature Fluctuations in Quasar Accretion Disks From Spectral VariabilityJan 06 2014The well-known bluer-when-brighter trend observed in quasar variability is a signature of the complex processes in the accretion disk, and can be a probe of the quasar variability mechanism. Using a sample of 604 variable quasars with repeat spectra in ... More

Finding Black Holes with MicrolensingMar 15 2002Sep 07 2002The MACHO and OGLE collaborations have argued that the three longest duration bulge microlensing events are likely caused by nearby black holes, given the small velocities measured with microlensing parallax and nondetection of the lenses. However, these ... More

Fast and scalable Gaussian process modeling with applications to astronomical time seriesMar 28 2017Jul 19 2017The growing field of large-scale time domain astronomy requires methods for probabilistic data analysis that are computationally tractable, even with large datasets. Gaussian Processes are a popular class of models used for this purpose but, since the ... More

Kepler-62f: Kepler's First Small Planet in the Habitable Zone, but Is It Real?May 14 2019Kepler-62f is the first exoplanet small enough to plausibly have a rocky composition orbiting within the habitable zone (HZ) discovered by the Kepler Mission. The planet is 1.4 times the size of the Earth and has an orbital period of 267 days. At the ... More

Non-LTE Models and Theoretical Spectra of Accretion Disks in Active Galactic Nuclei. III. Integrated Spectra for Hydrogen-Helium DisksNov 16 1999We have constructed a grid of non-LTE disk models for a wide range of black hole mass and mass accretion rate, for several values of viscosity parameter alpha, and for two extreme values of the black hole spin: the maximum-rotation Kerr black hole, and ... More

Non-LTE, Relativistic Accretion Disk Fits to 3C~273 and the Origin of the Lyman Limit Spectral BreakAug 28 2001We fit general relativistic, geometrically thin accretion disk models with non-LTE atmospheres to near simultaneous multiwavelength data of 3C~273, extending from the optical to the far ultraviolet. Our model fits show no flux discontinuity associated ... More

Hubble Imaging Excludes Cosmic String LensMar 30 2006Apr 14 2006The galaxy image pair CSL-1 has been a leading candidate for a cosmic string lens. High quality imaging data from the Hubble Space Telescope presented here show that it is not a lens but a pair of galaxies. The galaxies show different orientations of ... More

Predictable patterns in planetary transit timing variations and transit duration variations due to exomoonsApr 18 2016Jun 20 2016We present new ways to identify single and multiple moons around extrasolar planets using planetary transit timing variations (TTVs) and transit duration variations (TDVs). For planets with one moon, measurements from successive transits exhibit a hitherto ... More

The Submillimeter Bump in Sgr A* from Relativistic MHD SimulationsMay 21 2010Recent high resolution observations of the Galactic center black hole allow for direct comparison with accretion disk simulations. We compare two-temperature synchrotron emission models from three dimensional, general relativistic magnetohydrodynamic ... More

Detection of Substructure in the Gravitationally Lensed Quasar MG0414+0534 using Mid-Infrared and Radio VLBI ObservationsDec 10 2012Jul 02 2013We present 11.2 micron observations of the gravitationally lensed, radio-loud z_s=2.64 quasar MG0414+0534, obtained using the Michelle camera on Gemini North. We find a flux ratio anomaly of A2/A1= 0.93 +/- 0.02 for the quasar images A1 and A2. When combined ... More

Detection of a Companion Lens Galaxy using the Mid-infrared Flux Ratios of the Gravitationally Lensed Quasar H1413+117Apr 02 2009Jul 10 2009We present the first resolved mid-IR (11 micron) observations of the four-image quasar lens H1413+117 using the Michelle camera on Gemini North. All previous observations (optical, near-IR, and radio) of this lens show a "flux anomaly," where the image ... More

TTVFast: An efficient and accurate code for transit timing inversion problemsMar 07 2014Transit timing variations (TTVs) have proven to be a powerful technique for confirming Kepler planet candidates, for detecting non-transiting planets, and for constraining the masses and orbital elements of multi-planet systems. These TTV applications ... More

Spectropolarimetry and Modeling of the Eclipsing T Tauri Star KH 15DSep 11 2003KH 15D is a strongly variable T Tauri star in the young star cluster NGC 2264 that shows a decrease in flux of 3.5 magnitudes lasting for 18 days and repeating every 48 days. The eclipsing material is likely due to orbiting dust or rocky bodies in a partial ... More

The Center of Light: Spectroastrometric Detection of ExomoonsSep 04 2015Direct imaging of extrasolar planets with future space-based coronagraphic telescopes may provide a means of detecting companion moons at wavelengths where the moon outshines the planet. We propose a detection strategy based on the positional variation ... More

The Mass of the White Dwarf Companion in the Self-Lensing Binary KOI-3278: Einstein vs. NewtonApr 24 2019Jun 04 2019KOI-3278 is a self-lensing stellar binary consisting of a white-dwarf secondary orbiting a Sun-like primary star. Kruse and Agol (2014) noticed small periodic brightenings every 88.18 days in the Kepler photometry and interpreted these as the result of ... More

New Worlds on the Horizon: Earth-Sized Planets Close to Other StarsOct 11 2007The search for habitable planets like Earth around other stars fulfils an ancient imperative to understand our origins and place in the cosmos. The past decade has seen the discovery of hundreds of planets, but nearly all are gas giants like Jupiter and ... More

Detecting and Characterizing Planetary Systems with Transit TimingApr 04 2007In the coming decades, research in extrasolar planets aims to advance two goals: 1) detecting and characterizing low-mass planets increasingly similar to the Earth, and 2) improving our understanding of planet formation. We present a new planet detection ... More

Residual finiteness, QCERF, and fillings of hyperbolic groupsFeb 05 2008Mar 10 2008We prove that if every hyperbolic group is residually finite, then every quasi-convex subgroup of every hyperbolic group is separable. The main tool is relatively hyperbolic Dehn filling.

The Computational Complexity of Knot Genus and Spanning AreaMay 06 2002Jul 10 2004We investigate the computational complexity of some problems in three-dimensional topology and geometry. We show that the problem of determining a bound on the genus of a knot in a 3-manifold, is NP-complete. Using similar ideas, we show that deciding ... More

Observations of the WASP-2 System by the APOSTLE ProgramJan 17 2013We present transit observations of the WASP-2 exoplanet system by the Apache Point Survey of Transit Lightcurves of Exoplanets (APOSTLE) program. Model fitting to these data allows us to improve measurements of the hot-Jupiter exoplanet WASP-2b and its ... More

Compact Objects and Accretion DisksJul 13 2001Recent developments in the spectropolarimetric study of compact objects, specifically black holes (stellar and massive) and neutron stars are reviewed. The lectures are organized around five topics: disks, jets, outflows, neutron stars and black holes. ... More

An update to the EVEREST K2 pipeline: Short cadence, saturated stars, and Kepler-like photometry down to Kp = 15Feb 17 2017We present an update to the EVEREST K2 pipeline that addresses various limitations in the previous version and improves the photometric precision of the de-trended light curves. We develop a fast regularization scheme for third order pixel level decorrelation ... More

Exo-Planetary Transits of Limb Brightened Lines; Tentative Si IV Absorption by HD209458bAug 05 2010Transit light curves for stellar continua have only one minimum and a "U" shape. By contrast, transit curves for optically thin chromospheric emission lines can have a "W" shape because of stellar limb-brightening. We calculate light curves for an optically ... More

Evaluation of a College Freshman Diversity Research ProgramNov 21 2013Since 2005, the Pre-Major in Astronomy Program (Pre-MAP) at the University of Washington (UW) Department of Astronomy has made a concentrated effort to recruit and retain underrepresented undergraduates in science, technology, engineering and mathematics ... More

Transit Analysis Package (TAP and autoKep): IDL Graphical User Interfaces for Extrasolar Planet Transit PhotometryFeb 04 2011We present an IDL graphical user interface-driven software package designed for the analysis of extrasolar planet transit light curves. The Transit Analysis Package (TAP) software uses Markov Chain Monte Carlo (MCMC) techniques to fit light curves using ... More

Observations of Extrasolar Planets During the non-Cryogenic Spitzer Space Telescope MissionOct 22 2007Precision infrared photometry from Spitzer has enabled the first direct studies of light from extrasolar planets, via observations at secondary eclipse in transiting systems. Current Spitzer results include the first longitudinal temperature map of an ... More

Transits and secondary eclipses of HD 189733 with SpitzerJul 15 2008We present limits on transit timing variations and secondary eclipse depth variations at 8 microns with the Spitzer Space Telescope IRAC camera. Due to the weak limb darkening in the infrared and uninterrupted observing, Spitzer provides the highest accuracy ... More

The Effect of Orbital Configuration on the Possible Climates and Habitability of Kepler-62fMar 03 2016As lower-mass stars often host multiple rocky planets, gravitational interactions among planets can have significant effects on climate and habitability over long timescales. Here we explore a specific case, Kepler-62f, a potentially habitable planet ... More

The population of long-period transiting exoplanetsJul 27 2016The Kepler Mission has discovered thousands of exoplanets and revolutionized our understanding of their population. This large, homogeneous catalog of discoveries has enabled rigorous studies of the occurrence rate of exoplanets and planetary systems ... More

The population of long-period transiting exoplanetsJul 27 2016Oct 06 2016The Kepler Mission has discovered thousands of exoplanets and revolutionized our understanding of their population. This large, homogeneous catalog of discoveries has enabled rigorous studies of the occurrence rate of exoplanets and planetary systems ... More

EVEREST: Pixel Level Decorrelation of K2 Light curvesJul 02 2016We present EVEREST, an open-source pipeline for removing instrumental noise from K2 light curves. EVEREST employs a variant of pixel level decorrelation (PLD) to remove systematics introduced by the spacecraft's pointing error and a Gaussian process (GP) ... More

STARRY: Analytic Occultation Light CurvesOct 15 2018We derive analytic, closed form, numerically stable solutions for the total flux received from a spherical planet, moon or star during an occultation if the specific intensity map of the body is expressed as a sum of spherical harmonics. Our expressions ... More

Stellar Properties of Active G and K Stars: Exploring the Connection Between Starspots and Chromospheric ActivityJun 30 2019We gathered high resolution spectra for an ensemble of 55 bright active and inactive stars using the ARC 3.5 m Telescope Echelle Spectrograph at Apache Point Observatory ($R\approx$31,500). We measured spectroscopic effective temperatures, surface gravities ... More

Small 3-manifolds of large genusMay 09 2002We prove the existence of pure braids with arbitrarily many strands which are small, i.e. they contain no closed incompressible surface in the complement which is not boundary parallel. This implies the existence of irreducible non-Haken 3-manifolds of ... More

Pants immersed in hyperbolic 3-manifoldsFeb 19 2008We show that an immersed thrice-punctured sphere in a cusped orientable hyperbolic 3-manifold is either embedded or has a single clasp in a manifold obtained by hyperbolic Dehn filling on a cusp of the Whitehead link complement.

Bounds on exceptional Dehn filling IIMar 20 2008We show that there are at most finitely many one cusped orientable hyperbolic 3-manifolds which have more than eight non-hyperbolic Dehn fillings. Moreover, we show that determining these finitely many manifolds is decidable.

Lower bounds on volumes of hyperbolic Haken 3-manifoldsJun 27 1999In this paper, we find lower bounds for volumes of hyperbolic 3-manifolds with various topological conditions. Let V_3 = 1.01494 denote the volume of a regular ideal simplex in hyperbolic 3-space. As a special case of the main theorem, if a hyperbolic ... More

Criteria for virtual fiberingJul 31 2007Feb 24 2008We prove that an irreducible 3-manifold whose fundamental group satisfies a certain group-theoretic property called RFRS is virtually fibered. As a corollary, we show that 3-dimensional reflection orbifolds and arithmetic hyperbolic orbifolds defined ... More

Ideal Triangulations of Pseudo-Anosov Mapping ToriAug 09 2010Aug 21 2010We show how to construct an ideal triangulation of a mapping torus of a pseudo-Anosov map punctured along the singular fibers. This gives rise to a new conjugacy invariant of mapping classes, and a new proof of a theorem of Farb-Leininger-Margalit. The ... More

Tameness of hyperbolic 3-manifoldsMay 29 2004We show that hyperbolic 3-manifolds with finitely generated fundamental group are tame, that is the ends are products. We actually work in slightly greater generality with pinched negatively curved manifolds with hyperbolic cusps. This answers a conjecture ... More

Systoles of hyperbolic 4-manifoldsDec 11 2006We prove that for any \e>0, there exists a closed hyperbolic 4-manifold with a closed geodesic of length < \e.

Bounds on exceptional Dehn fillingJun 27 1999Nov 15 2000We show that for a hyperbolic knot complement, all but at most 12 Dehn fillings are irreducible with infinite word-hyperbolic fundamental group.

Are Starspots and Plages Co-Located on Active G and K Stars?Sep 12 2018We explore the connection between starspots and plages of three main-sequence stars by studying the chromospheric and photospheric activity over several rotation periods. We present simultaneous photometry and high-resolution ($R\sim 31,500$) spectroscopy ... More

Virtual betti numbers of symmetric spacesNov 27 2006We prove that a closed arithmetic hyperbolic 3-manifold with positive first betti number has virtually infinite first betti number.

The minimal volume orientable hyperbolic 2-cusped 3-manifoldsMar 31 2008May 18 2010We prove that the Whitehead link complement and the (-2, 3, 8) pretzel link complement are the minimal volume orientable hyperbolic 3-manifolds with two cusps, with volume 3.66... = 4 x Catalan's constant. We use topological arguments to establish the ... More

Finiteness of arithmetic Kleinian reflection groupsDec 24 2005We prove that there are only finitely many arithmetic Kleinian maximal reflection groups.

Transcendental ending laminationsJun 21 2004Yair Minsky showed that punctured torus groups are classified by a pair of ending laminations (\nu_-,\nu_+). In this note, we show that there are ending laminations \nu_+ such that for any choice of \nu_-, the punctured torus group is transcendental as ... More

The 8 Micron Phase Variation of the Hot Saturn HD 149026bAug 13 2009We monitor the star HD 149026 and its Saturn-mass planet at 8.0 micron over slightly more than half an orbit using the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We find an increase of 0.0227% +/- 0.0066% (3.4 sigma significance) in ... More

The Pale Green Dot: A Method to Characterize Proxima Centauri b using Exo-AuroraeSep 28 2016We examine the feasibility of detecting auroral emission from the potentially habitable exoplanet Proxima Centauri b. This planet's active, late-type M dwarf host makes detection of aurorae more favorable than around a solar-type star, primarily by increasing ... More

Rapid dynamical chaos in an exoplanetary systemJun 20 2012We report on the long-term dynamical evolution of the two-planet Kepler-36 system, which we studied through numerical integrations of initial conditions that are consistent with observations of the system. The orbits are chaotic with a Lyapunov time of ... More

Habitable Planets Around White Dwarfs: an Alternate Mission for the Kepler SpacecraftAug 30 2013A large fraction of white dwarfs (WDs) may host planets in their habitable zones. These planets may provide our best chance to detect bio-markers on a transiting exoplanet, thanks to the diminished contrast ratio between the Earth-sized WD and its Earth-sized ... More

The Pale Green Dot: A Method to Characterize Proxima Centauri b using Exo-AuroraeSep 28 2016Feb 14 2017We examine the feasibility of detecting auroral emission from the potentially habitable exoplanet Proxima Centauri b. Detection of aurorae would yield an independent confirmation of the planet's existence, constrain the presence and composition of its ... More

Exploring the Brown Dwarf Desert: New Substellar Companions from the SDSS-III MARVELS SurveyFeb 06 2017Planet searches using the radial velocity technique show a paucity of companions to solar-type stars within ~5 AU in the mass range of ~10 - 80 M$_{\text{Jup}}$. This deficit, known as the brown dwarf desert, currently has no conclusive explanation. New ... More

A Precise Estimate of the Radius of the Exoplanet HD 149026b from Spitzer PhotometryMay 06 2008Nov 13 2008We present Spitzer 8 micron transit observations of the extrasolar planet HD 149026b. At this wavelength, transit light curves are weakly affected by stellar limb-darkening, allowing for a simpler and more accurate determination of planetary parameters. ... More

A Higher Cadence Subsurvey Located in the Galactic PlaneDec 07 2018Presently, the Galactic plane receives relatively few observations compared to most of the LSST footprint. While this may address static science, the plane will also represent the highest density of variable Galactic sources. The proper characterization ... More

A Precise Estimate of the Radius of HD 149026bJul 08 2008We present Spitzer 8 micron transit observations of the extrasolar planet system HD 149026. At this wavelength, transit light curves are weakly affected by stellar limb-darkening, allowing for a simpler and more accurate determination of planetary parameters. ... More

Transit Timing Observations of the Extrasolar Hot-Neptune Planet GL 436bJan 03 2009Gliese 436 is an M dwarf with a mass of 0.45 Msun and hosts the extrasolar planet GL 436b [3, 6, 7, 2], which is currently the least massive transiting planet with a mass of ~23.17 Mearth [10], and the only planet known to transit an M dwarf. GL 436b ... More

Secure TTV Mass Measurements: Ten Kepler Exoplanets between 3 and 8 Earth Masses with Diverse Densities and Incident FluxesDec 07 2015Mar 21 2016We infer dynamical masses in eight multi-planet systems using transit times measured from Kepler's complete dataset, including short-cadence data where available. Of the eighteen dynamical masses that we infer, ten pass multiple tests for robustness. ... More

Non-detection of Contamination by Stellar Activity in the Spitzer Transit Light Curves of TRAPPIST-1Aug 08 2018We apply the transit light curve self-contamination technique of Morris et al. (2018) to search for the effect of stellar activity on the transits of the ultracool dwarf TRAPPIST-1 with 2018 Spitzer photometry. The self-contamination method fits the transit ... More

Kepler and Ground-based Transits of the Exo-Neptune HAT-P-11bJul 15 2011We analyze 26 archival Kepler transits of the exo-Neptune HAT-P-11b, supplemented by ground-based transits observed in the blue (B-band) and near-IR (J-band). Both the planet and host star are smaller than previously believed; our analysis yields Rp=4.31 ... More

Multi-Wavelength Constraints on the Day-Night Circulation Patterns of HD 189733bFeb 12 2008Sep 09 2008We present new Spitzer observations of the phase variation of the hot Jupiter HD 189733b in the MIPS 24 micron bandpass, spanning the same part of the planet's orbit as our previous observations in the IRAC 8 micron bandpass (Knutson et al. 2007). We ... More