A5024534230- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Planetary Science and Exploration
- Geophysics and Gravity Measurements
- Space Science and Extraterrestrial Life
- Astronomical and nuclear sciences
- Spacecraft Dynamics and Control
- Scientific Research and Discoveries
- Spacecraft and Cryogenic Technologies
- Adaptive optics and wavefront sensing
- Calibration and Measurement Techniques
- Spacecraft Design and Technology
- Mechanics and Biomechanics Studies
- Oceanographic and Atmospheric Processes
- Control Systems and Identification
- Relativity and Gravitational Theory
- Approximation Theory and Sequence Spaces
- Advanced Algebra and Geometry
University of California, Los Angeles
2014-2024
UCLA Health
2009-2019
Florida Gulf Coast University
2016
Institute of Geophysics
2011
Planetary Science Institute
2007-2010
Mathematical Sciences Research Institute
2004
Princeton University
2000-2003
University of Toronto
1996-2001
Canadian Institute for Theoretical Astrophysics
1997-2001
Canadian Institute for Advanced Research
1998
We analyse the sample of pulsar proper motions, taking detailed account selection effects original surveys. treat censored data using survival statistics. From a comparison our results with Monte Carlo simulations, we find that mean birth speed is ~250–300 km s−1, rather than 450 s−1 found by Lyne & Lorimer. The resultant distribution consistent Maxwellian dispersion συ = 190 s−1. Despite large velocities, pulsars long characteristic ages show asymmetric drift, indicating they are...
A planet orbiting in a disk of planetesimals can experience an instability which it migrates to smaller orbital radii. Resonant interactions between the and remove angular momentum from planetesimals, increasing their eccentricities. Subsequently, either collide with or are ejected by planet, reducing semimajor axis planet. If surface density exceeds critical value, corresponding 0.03 solar masses gas inside orbit Jupiter, will migrate inward large distance. This may explain presence...
High-resolution atmospheric flow simulations of the tidally locked extrasolar giant planet HD 209458b show large-scale spatio-temporal variability. This is in contrast to simple, permanent day/night (i.e., hot/cold) picture. The planet's global circulation characterized by a polar vortex motion around each pole and banded structure corresponding approximately three broad zonal (east-west) jets. For very strong jets, circulation-induced temperature difference between moving hot cold regions...
A significant fraction of white dwarfs (WDs) are observed to be polluted with metals despite high surface gravities and short settling times. The current theoretical model for this pollution is accretion rocky bodies delivered the WD through perturbations by orbiting planets. Using N-body simulations, we examine possibility a single planet as source pollution. We determine stability test particles on circular orbits in systems located at 4 au range masses eccentricities, comparing fractions...
We investigate the role that planet detection order plays in Kepler pipeline. The pipeline typically detects planets of descending signal strength (MES). find detectability transits experiences an additional 5.5 per cent and 15.9 efficiency loss, for periods <200 days >200 respectively, when detected after strongest transit a multiple-planet system. provide method determining probability systems by marginalizing over empirical dataset. Furthermore, because appears to be function order, we...
We discuss atmosphere models of HD209458b in light the recent day-side flux measurement HD209458b's secondary eclipse by Spitzer-MIPS at 24 microns. In addition, we present a revised IRTF upper limit 2.2 microns which places stringent constraint on adjacent H2O absorption band depths. These two measurements are complementary because they both shaped and former is Wien tail planet's thermal emission spectrum latter near peak. A wide range fit observational data, confirming our basic...
We present results from a set of over 300 pseudospectral simulations atmospheric circulation on extrasolar giant planets with circular orbits.The are high enough resolution (up to 341 total and sectoral modes) resolve small-scale eddies waves, required for reasonable physical accuracy.In this work, we focus the global pattern that emerges in shallow, "equivalent-barotropic", turbulent atmosphere both tidally synchronized unsynchronized planets.A full exploration large numerical...
We examine the effect of secular perturbations by giant planets on systems multiple, lower mass orbiting Sun-like stars. simulate effects forcing both eccentricity and inclination, separately together. compare our results to statistics observed Kepler data whether these can be used explain excess single transiting planets. cannot pumping only inclination without driving most over edge dynamical instability. Thus, we expect underlying planetary population for with a transitting planet contain...
We study spectroscopically determined iron abundances of 640 solar-type stars to search for the signature accreted iron-rich material. find that metallicity [Fe/H] a subset 466 main-sequence stars, when plotted as function stellar mass, mimics pattern seen in lithium open clusters. Using Monte Carlo models, we that, on average, these appear have ~0.5 M⊕ while main-sequence. A consistency check is provided by much smaller sample 19 Hertzsprung gap, which are slightly evolved and convection...
Recent Spitzer infrared measurements of hot Jupiter eclipses suggest that eclipse mapping techniques could be used to spatially resolve the day-side photospheric emission these planets using partial occultations. As a first step in this direction, we simulate ingress/egress lightcurves for three brightest known eclipsing Jupiters and evaluate degree which parameterized models can distinguished from each other with repeated, noisy measurements. We find photometric accuracy is insufficient use...
We describe the long-term evolution of compact systems terrestrial planets, using a set simulations that match statistical properties observed exoplanet distribution. The is driven by tidal dissipation in planetary interiors, but evolve as whole due to secular gravitational interactions. find that, for Earth-like levels, orbits can be circularised out periods order 100 days, an magnitude larger than possible single planets. resulting distribution eccentricities qualitative inferred from...
Abstract The Gaia mission has detected many white dwarfs (WDs) in binary and triple configurations, while observations suggest that triple-stellar systems are common our Galaxy, not much attention was devoted to WDs triples. For stability reasons, these triples must have hierarchical i.e., two stars on a tight orbit (the inner binary), with the third companion wider about binary. In such system, orbits torque each other via eccentric Kozai–Lidov mechanism, which can alter orbital...
Abstract The large eccentricities of cold Jupiters and the existence hot have long challenged theories planet formation. A proposed solution to both these puzzles is high-eccentricity migration, in which an initially Jupiter excited high before being tidally circularized. Secular perturbations from inclined stellar companion are a potential source eccentricity oscillations, phenomenon known as Eccentric Kozai–Lidov (EKL) mechanism. Previous studies found that distribution produced by EKL...
Shallow-water numerical simulations show that the atmospheric circulation of close-in extrasolar giant planet (EGP) HD 209458b is characterized by moving circumpolar vortices and few bands/jets (in contrast to ~10 absence polar on cloud-top Jupiter Saturn). The large spatial scales structures may generate detectable variability planet's signatures. In this Letter, we generalize these results other EGPs, noting shallow-water dynamics essentially specified values Rossby (Ro) Burger (Bu)...
Physical conditions in the atmospheres of tidally locked, slowly rotating hot Jupiters correspond to dynamical circulation regimes with Rhines scales and Rossby deformation radii comparable planetary radii. Consequently, large spatial moving atmospheric structures could generate significant photospheric variability. Here we estimate level thermal infrared variability expected successive secondary eclipse depths, according Jupiter turbulent "shallow-layer" models. The variability, at few...
We present a new distance determination to the Galactic globular cluster 47 Tucanae by fitting spectral energy distributions of its white dwarfs pure hydrogen atmosphere dwarf models. Our photometric dataset is obtained from 121 orbit Hubble Space Telescope program using Wide Field Camera 3 UVIS/IR channels, capturing F390W, F606W, F110W, and F160W images. These images cover more than 60 square arcmins extend over radial range 5-13.7 arcmin (6.5-17.9 pc) within cluster. Using likelihood...
We demonstrate that tidal evolution of the inner planet (`e') system orbiting star rho 55 Cancri could have led to passage through two secular resonances with other planets in system. The consequence this is excitation both planetary eccentricity and inclination relative original orbital plane. large mass ratio between innermost others means these excitations can be substantial amplitude dramatic consequences for organisation. Such potentially explain observed mutual outermost system,...
Warm jupiters are an unexpected population of extrasolar planets that too near to their host have formed in situ, but distant enough retain a significant eccentricity the face tidal damping. These curiously absent around stars larger than two solar radii. We hypothesize warm migrating due Kozai–Lidov oscillations, which lead transient episodes high and consequent decay. As evolves, such would be rapidly dragged or engulfed at minimum periapse, leading dramatic depletion this with increasing...
We examine the consequences of a model for circulation solids in protoplanetary nebula which aerodynamic drag is counterbalanced by recycling material to outer disc protostellar outflow or wind. This population circulating dust eventually becomes unstable formation planetesimals gravitational instability, and results ultimate deposition ∼30–50 M⊕ on scales R<1 au. Such may provide an appropriate justification approximately power-law initial conditions needed reproduce observed planetary...
Using the updated exoplanet population parameters of our previous study, which includes planetary radius updates from Gaia DR2 and an inferred multiplicity distribution, we provide a revised $\eta_{\oplus}$ calculation. This is achieved by sampling planets derived model determining meet criterion for habitability. To ensure robust results, probabilities calculated over range upper limits. Our most optimistic habitability provides value $0.34\pm 0.02 \frac{\rm planets}{\rm star}$. We also...
Abstract More than half of all main-sequence (MS) stars have one or more companions, and many those with initial masses <8 M ⊙ are born in hierarchical triples. These systems feature two a close orbit (the inner binary) while tertiary star orbits them on wider outer binary). In triples, three-body dynamics combined stellar evolution drives interactions and, cases, merges the binary entirely to create renovated “post-merger binary” (PMB). By leveraging dynamical simulations tracking...
We present new results from a photometric study of the main-sequence stars in M4 (NGC 6121=C1620-264), closest globular cluster to Sun. Multifield, multiepoch observations at approximately 1, 2, and 6 core radii were obtained with WFPC2 on Hubble Space Telescope through either F606W filter or F555W (V) F814W (I) filters. The allowed us clean data basis proper motion thus separate field extragalactic objects. In all fields main sequence can be traced least V = 27.0, but there remains trail...
We show that a model in which Mars grows near Earth and Venus but is then scattered out of the terrestrial region yields natural pathway to explain low masses Martian moons Phobos & Deimos. In this scenario, last giant impact experienced by followed an extended period (tens hundreds Myr) close passages other planetary embryos. These perturb dynamically heat any system forming satellites left over can substantially reduce mass satellite (sometimes zero). The passage massive perturbing bodies...