Results for "P. Dufour"

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Stars with Unusual Compositions: Carbon and Oxygen in Cool White Dwarf StarsSep 30 2011I present a broad historical review on cool white dwarf stars with carbon and/or oxygen detected at the photosphere. This book chapter covers the observational signatures, physical properties, and evolution of DQ, DBQ and Hot DQ white dwarfs, and also ... More
An aluminum/calcium-rich, iron-poor, white dwarf star: evidence for an extrasolar planetary lithosphere?Jul 12 2011The presence of elements heavier than helium in white dwarf atmospheres is often a signpost for the existence of rocky objects that currently or previously orbited these stars. We have measured the abundances of various elements in the hydrogen-atmosphere ... More
The Discovery of a Debris Disk Around the DAV White Dwarf PG 1541+651Oct 17 2011To search for circumstellar disks around evolved stars, we targeted roughly 100 DA white dwarfs from the Palomar Green survey with the Peters Automated Infrared Imaging Telescope (PAIRITEL). Here we report the discovery of a debris disk around one of ... More
A New Generation of Cool White Dwarf Atmosphere Models. III. WD J2356$-$209: Accretion of a Planetesimal with an Unusual CompositionFeb 08 2019WD J2356$-$209 is a cool metal-polluted white dwarf whose visible spectrum is dominated by a strong and broad sodium feature. Although discovered nearly two decades ago, no detailed and realistic analysis of this star had yet been realized. In the absence ... More
Does a Differentiated, Carbonate-Rich, Rocky Object Pollute the White Dwarf SDSSJ104341.53+085558.2?Oct 25 2016We present spectroscopic observations of the dust- and gas-enshrouded, polluted, single white dwarf star SDSSJ104341.53+085558.2 (hereafter SDSSJ1043+0855). Hubble Space Telescope Cosmic Origins Spectrograph far-ultraviolet spectra combined with deep ... More
The Frequency of Debris Disks at White DwarfsSep 14 2012We present near- and mid-infrared photometry and spectroscopy from PAIRITEL, IRTF, and Spitzer of a metallicity-unbiased sample of 117 cool, hydrogen-atmosphere white dwarfs from the Palomar-Green survey and find five with excess radiation in the infrared, ... More
Semi-local invariants for non-resonnant Poisson structures on S1xRnDec 13 2004The purpose of this paper is to give a semi-local study along generic closed curves of zeros: we formally classify Poisson structures defined in a neighborhood of Gamma:=S^1x{0} in S^1xR^n, that vanish on Gamma, and whose linear approximation at one point ... More
Power-of-$d$-Choices with Memory: Fluid Limit and OptimalityFeb 19 2018In multi-server distributed queueing systems, the access of stochastically arriving jobs to resources is often regulated by a dispatcher, also known as load balancer. A fundamental problem consists in designing a load balancing algorithm that minimizes ... More
Singularities and bifurcations of 3-dimensional Poisson structureFeb 25 1998We give a normal form for families of 3-dimensional Poisson structures. This allows us to classify singularities with nonzero 1-jet and typical bifurcations. The Appendix contains corollaries on classification of families of integrable 1-forms on $R^3 ... More
A Detailed Spectroscopic and Photometric Analysis of DQ White DwarfsMar 21 2005We present an analysis of spectroscopic and photometric observations of cool DQ white dwarfs based on improved model atmosphere calculations. In particular, we revise the atmospheric parameters of the trigonometric parallax sample of Bergeron, Leggett, ... More
Detailed Spectroscopic and Photometric Analysis of DQ White DwarfsMar 04 2005We present an analysis of spectroscopic and photometric data for cool DQ white dwarfs based on improved model atmosphere calculations. In particular, we revise the atmospheric parameters of the trigonometric parallax sample of Bergeron et al.(2001), and ... More
Might Carbon-Atmosphere White Dwarfs Harbour a New Type of Pulsating Star?Mar 14 2008In the light of the recent and unexpected discovery of a brand new type of white dwarfs, those with carbon-dominated atmospheres, we examine the asteroseismological potential of such stars. The motivation behind this is based on the observation that past ... More
Analysis of DA White Dwarfs from the McCook & Sion CatalogMar 04 2005Mar 04 2005The Sloan Digital Sky Survey has already doubled the number of spectroscopically identified white dwarfs. However, there remains a wealth of white dwarfs in the McCook & Sion catalog for which little or nothing is known. We have thus undertaken a spectroscopic ... More
Discovery of a Cool, Massive, and Metal-Rich DAZ White DwarfOct 28 2004We report the discovery of a new metal-rich DAZ white dwarf, GD 362. High signal-to-noise optical spectroscopy reveals the presence of spectral lines from hydrogen as well as CaI, CaII, MgI, and FeI. A detailed model atmosphere analysis of this star yields ... More
Identification-robust moment-based tests for Markov-switching in autoregressive modelsDec 30 2016This paper develops tests of the null hypothesis of linearity in the context of autoregressive models with Markov-switching means and variances. These tests are robust to the identification failures that plague conventional likelihood-based inference ... More
Veronese curves and webs interpolationAug 18 2004Sep 01 2004Veronese webs appear as the natural way of passing to the quotient of curves in the projective space. In thi paper, we give the link between classical multidimensionnal webs and veronse webs by mean of interpolation.
Spectroscopic Analysis of the White Dwarf KUV 02196+2816: A New Unresolved DA+DB Degenerate BinaryFeb 20 2009A spectroscopic analysis of the DBA (or DAB) white dwarf KUV 02196+2816 is presented. The observed hydrogen and helium line profiles are shown to be incompatible with model spectra calculated under the assumption of a homogeneous hydrogen and helium chemical ... More
Separation of the monopole contribution to the nuclear HamiltonianMay 08 1995It is shown that the nuclear Hamiltonian can be separated rigorously as ${\cal H}={\cal H}_m+{\cal H}_M.$ For sufficiently smooth forces the monopole part ${\cal H}_m $is entirely responsible for Hartree-Fock selfconsistency and hence saturation properties. ... More
Taking Advantage of the COS Time-Tag Capability: Observations of Pulsating Hot DQ White Dwarfs and Discovery of a New OneApr 13 2011We present an analysis of the ultraviolet light curves of five Hot DQ white dwarfs recently observed with the Cosmic Origins Spectrograph (COS) on board the Hubble Space Telescope (HST). These light curves were constructed by extracting the time-tag information ... More
Magnetic White Dwarfs with Heavy ElementsOct 05 2016Using our newly developed model atmosphere code appropriate for magnetic white dwarfs with metal lines in the Paschen-Back regime, we study various magnetic white dwarfs and explore the effects of various parameters such as the field geometry and the ... More
Pressure Distortion of the H$_2$-He Collision-Induced Absorption at the Photosphere of Cool White Dwarf StarsSep 05 2017Collision-induced absorption (CIA) from molecular hydrogen is a dominant opacity source in the atmosphere of cool white dwarfs. It results in a significant flux depletion in the near-IR and IR parts of their spectra. Because of the extreme conditions ... More
Follow-up Studies of the Pulsating Magnetic White Dwarf SDSS J142625.71+575218.3Jul 13 2009We present a follow-up analysis of the unique magnetic luminosity-variable carbon-atmosphere white dwarf SDSS J142625.71+575218.3. This includes the results of some 106.4 h of integrated light photometry which have revealed, among other things, the presence ... More
Nonparametric estimation of the jump rate for non-homogeneous marked renewal processesFeb 10 2012Sep 13 2012This paper is devoted to the nonparametric estimation of the jump rate and the cumulative rate for a general class of non-homogeneous marked renewal processes, defined on a separable metric space. In our framework, the estimation needs only one observation ... More
Average Continuous Control of Piecewise Deterministic Markov ProcessesSep 02 2008This paper deals with the long run average continuous control problem of piecewise deterministic Markov processes (PDMP's) taking values in a general Borel space and with compact action space depending on the state variable. The control variable acts ... More
A Progress Report on the Carbon Dominated Atmosphere White DwarfsJan 22 2009Recently, Dufour et al. (2007) reported the unexpected discovery that a few white dwarfs found in the Sloan Digital Sky Survey had an atmosphere dominated by carbon with little or no trace of hydrogen and helium. Here we present a progress report on these ... More
The first polluted white dwarf from Gaia DR2: the cool DAZ GaiaJ1738-0826Jun 24 2018We present the first metal-polluted single white dwarf star identified through Gaia DR2. GaiaJ1738-0826, selected from color and absolute magnitude cuts in the Gaia DR2 data, was discovered to have strong Ca~II absorption in initial spectroscopic characterization ... More
Cool DZ white dwarfs in the SDSSMay 02 2011We report the identification of 26 cool DZ white dwarfs that lie across and below the main sequence in the Sloan Digital Sky Survey (SDSS) u-g vs. g-r two-color diagram; 21 of these stars are new discoveries. The sample was identified by visual inspection ... More
The Magnetic and Metallic Degenerate G77-50Jan 11 2011An accumulation of multi-epoch, high-resolution, optical spectra reveal that the nearby star G77-50 is a very cool DAZ white dwarf externally polluted by Mg, Fe, Al, Ca, and possibly Na, Cr, Mn. The metallic and hydrogen absorption features all exhibit ... More
Rare White dwarf stars with carbon atmospheresNov 20 2007White dwarfs represent the endpoint of stellar evolution for stars with initial masses between approximately 0.07 msun and 8-10 msun, where msun is the mass of the Sun (more massive stars end their life as either black holes or neutron stars). The theory ... More
Hot DQ White Dwarf Stars: A New Challenge to Stellar EvolutionNov 21 2007We report the discovery of a new class of hydrogen-deficient stars: white dwarfs with an atmosphere primarily composed of carbon, with little or no trace of hydrogen or helium. Our analysis shows that the atmospheric parameters found for these stars do ... More
Evidence for Gas from a Disintegrating Extrasolar AsteroidNov 18 2015We report high-resolution spectroscopic observations of WD 1145+017 -- a white dwarf that recently has been found to be transitted by multiple asteroid-sized objects within its tidal radius. We have discovered numerous circumstellar absorption lines with ... More
Implication of a large θ_13 for the Tokai to Kamioka and Korea setupNov 16 2012In this paper, I present the implications of the large value of \theta_13 on the Tokai to Kamioka and Korea setup (T2KK). I study the sensitivity of T2KK when using a 750 kW beam (the design luminosity of T2K planned to be achieved by 2017) and a potential ... More
The Solar Neighborhood. XIX. Discovery and Characterization of 33 New Nearby White Dwarf SystemsApr 06 2007We present spectra for 33 previously unclassified white dwarf systems brighter than V = 17 primarily in the southern hemisphere. Of these new systems, 26 are DA, 4 are DC, 2 are DZ, and 1 is DQ. We suspect three of these systems are unresolved double ... More
Quantum reflection and Liouville transformations from wells to wallsDec 04 2014Liouville transformations map in a rigorous manner one Schr\"odinger equation into another, with a changed scattering potential. They are used here to transform quantum reflection of an atom on an attractive well into reflection of the atom on a repulsive ... More
Distant White Dwarfs in the US Naval Observatory Flagstaff Station Parallax SampleSep 28 2018This paper presents new trigonometric parallaxes and proper motions for 214 stars. The measurements were made at the US Naval Observatory Flagstaff Station (NOFS) between 1989 and 2017, and the average uncertainty in the parallax values is 0.6 mas. We ... More
The Solar Neighborhood. XX. Discovery and Characterization of 21 New Nearby White Dwarf SystemsMay 16 2008We present medium resolution spectroscopy and multi-epoch VRI photometry for 21 new nearby (< 50 pc) white dwarf systems brighter than V ~ 17. Of the new systems, ten are DA (including a wide double degenerate system with two DA components), eight are ... More
Detailed compositional analysis of the heavily polluted DBZ white dwarf SDSS J073842.56+183509.06: A window on planet formation?Jan 30 2012We present a new model atmosphere analysis of the most metal contaminated white dwarf known, the DBZ SDSS J073842.56+183509.06. Using new high resolution spectroscopic observations taken with Keck and Magellan, we determine precise atmospheric parameters ... More
Follow-up Observations of the Second and Third Known Pulsating Hot DQ White DwarfsJul 24 2009We present follow-up time-series photometric observations that confirm and extend the results of the significant discovery made by Barlow et al.(2008) that the Hot DQ white dwarfs SDSS J220029.08-074121.5 and SDSS J234843.30-094245.3 are luminosity variable. ... More
Pulsation in carbon-atmosphere white dwarfs: A new chapter in white dwarf asteroseismologyJan 22 2009We present some of the results of a survey aimed at exploring the asteroseismological potential of the newly-discovered carbon-atmosphere white dwarfs. We show that, in certains regions of parameter space, carbon-atmosphere white dwarfs may drive low-order ... More
The Montreal White Dwarf Database: a Tool for the CommunityOct 04 2016We present the "Montreal White Dwarf Database" (MWDD), an accessible database with sortable/filterable table and interactive plots that will, when fully completed, allow the community to explore the physical properties of all white dwarfs ever analyzed ... More
Precise Atmospheric Parameters for the Shortest Period Binary White Dwarfs: Gravitational Waves, Metals, and PulsationsAug 13 2014Aug 16 2014We present a detailed spectroscopic analysis of 61 low mass white dwarfs and provide precise atmospheric parameters, masses, and updated binary system parameters based on our new model atmosphere grids and the most recent evolutionary model calculations. ... More
Rocky Planetesimals as the Origin of Metals in DZ StarsJan 27 2010{Abridged}. An analysis of the calcium and hydrogen abundances, Galactic positions and kinematics of 146 DZ stars from the Sloan Digital Sky Survey demonstrates that interaction with the interstellar medium cannot account for their externally polluted ... More
Stark Broadening of Carbon and Oxygen Lines in Hot DQ White Dwarf Stars: Recent Results and ApplicationsJul 15 2011White dwarf stars are traditionally found to have surface compositions made primarily of hydrogen or helium. However, a new family has recently been uncovered, the so-called Hot DQ white dwarfs, which have surface compositions dominated by carbon and ... More
The Chemical Composition of an Extrasolar Kuiper-Belt-ObjectFeb 09 2017The Kuiper Belt of our solar system is a source of short-period comets that may have delivered water and other volatiles to Earth and the other terrestrial planets. However, the distribution of water and other volatiles in extrasolar planetary systems ... More
Evidence for an Anhydrous Carbonaceous Extrasolar Minor PlanetNov 18 2014Using Keck/HIRES, we report abundances of 11 different elements heavier than helium in the spectrum of Ton 345, a white dwarf that has accreted one of its own minor planets. This particular extrasolar planetesimal which was at least 60% as massive as ... More
A Comprehensive Spectroscopic Analysis of DB White DwarfsMay 27 2011We present a detailed analysis of 108 helium-line (DB) white dwarfs based on model atmosphere fits to high signal-to-noise optical spectroscopy. We derive a mean mass of 0.67 Mo for our sample, with a dispersion of only 0.09 Mo. White dwarfs also showing ... More
SDSS J000555.90-100213.5: a hot, magnetic carbon-atmosphere WD rotating with a 2.1 day periodMay 09 2013A surprisingly large fraction (70%) of hot, carbon dominated atmosphere (DQ) white dwarfs are magnetic and/or photometrically variable on short timescales up to ~1000 s. However, here we show that the hot DQ magnetic white dwarf SDSS J000555.90-100213.5 ... More
MISOLFA solar monitor for the ground PICARD programDec 15 2014Developed at the Observatoire de la C\^ote d'Azur (OCA) within the framework of the PICARD space mission (Thuillier et al., 2006) and with support from the french spatial agency (CNES), MISOLFA (Moniteur d'Images Solaires Franco-Alg\'erien) is a new generation ... More
Identifying and Characterizing New Nearby White DwarfsOct 31 2006How confident are we that all of the nearest white dwarfs (WDs) have been identified? In an effort to answer this question, we have begun an initiative to identify and characterize new nearby WDs, particularly in the southern hemisphere. We estimate physical ... More
Evidence for a merger of binary white dwarfs: the case of GD 362Apr 10 2007GD 362 is a massive white dwarf with a spectrum suggesting a H-rich atmosphere which also shows very high abundances of Ca, Mg, Fe and other metals. However, for pure H-atmospheres the diffusion timescales are so short that very extreme assumptions have ... More
Accretion and activity on the post-common-envelope binary RR~CaeJul 23 2013Current scenarios for the evolution of interacting close binaries - such as cataclysmic variables (CVs) - rely mainly on our understanding of low-mass star angular momentum loss (AML) mechanisms. The coupling of stellar wind with its magnetic field, i.e., ... More
Ignition and extinction phenomena in helium micro hollow cathode dischargesApr 29 2016Micro hollow cathode discharges (MHCD) were produced using 250 m thick dielectric layer of alumina sandwiched between two nickel electrodes of 8 m thickness. A through cavity at the center of the chip was formed by laser drilling technique. MHCD with ... More
A subtle IR excess associated with a young White Dwarf in the Edinburgh-Cape Blue Object SurveyAug 15 2016We report the discovery of a subtle infrared excess associated with the young white dwarf EC\,05365--4749 at 3.35 and 4.6\,$\mu$m. Follow-up spectroscopic observations are consistent with a hydrogen atmosphere white dwarf of effective temperature 22\,800\,K ... More
Low-density polyethylene films treated by an atmospheric Ar--O2 post-discharge: functionalization, etching, degradation and partial recovery of the native wettability stateApr 29 2016To optimize the adhesion of layers presenting strong barrier properties on low-density polyethylene (LDPE) surfaces, we investigated the influence of argon and argon-oxygen atmospheric pressure post-discharges. This study was performed using x-ray photoelectron ... More
Hot DQ White Dwarfs: Something DifferentMay 03 2008We present a detailed analysis of all the known Hot DQ white dwarfs in the Fourth Data Release of the Sloan Digital Sky Survey (SDSS) recently found to have carbon dominated atmospheres. Our spectroscopic and photometric analysis reveals that these objects ... More
Hubble Space Telescope Imaging of the Binary Nucleus of the Planetary Nebula EGB 6May 02 2013EGB 6 is an ancient, low-surface-brightness planetary nebula. The central star, also cataloged as PG 0950+139, is a very hot DAOZ white dwarf (WD) with an apparent M dwarf companion, unresolved from the ground but detected initially through excesses in ... More
SDSS J142625.71+575218.3: The First Pulsating White Dwarf with a Large Detectable Magnetic FieldJul 07 2008We report the discovery of a strong magnetic field in the unique pulsating carbon-atmosphere white dwarf SDSS J142625.71+575218.3. From spectra gathered at the MMT and Keck telescopes, we infer a surface field of B_s ~1.2 MG, based on obvious Zeeman components ... More
A Multi-Survey Approach to White Dwarf DiscoveryMar 27 2012By selecting astrometric and photometric data from the Sloan Digital Sky Survey (SDSS), the L{\'e}pine & Shara Proper Motion North Catalog (LSPM-North), the Two Micron All Sky Survey (2MASS), and the USNO-B1.0 catalog, we use a succession of methods to ... More
On the Interpretation of High Velocity White Dwarfs as Members of the Galactic HaloFeb 17 2005Feb 18 2005A detailed analysis of 32 of the 38 halo white dwarf candidates identified by Oppenheimer et al. is presented, based on model atmosphere fits to observed energy distributions built from optical BVRI and infrared JHK CCD photometry. Effective temperatures ... More
The Discovery of the Most Metal-Rich White Dwarf: Composition of a Tidally Disrupted Extrasolar Dwarf PlanetJun 18 2010Cool white dwarf stars are usually found to have an outer atmosphere that is practically pure in hydrogen or helium. However, a small fraction have traces of heavy elements that must originate from the accretion of extrinsic material, most probably circumstellar ... More
Experimental study and simulation of a micro-discharge with limited cathode areaApr 29 2016We report in this paper simulation results and experimental measurements to characterize a micro-discharge generated in a single micro cavity device operating in helium. By spatially limiting the cathode surface area using a dielectric layer, we demonstrate ... More
Accretion of a Terrestrial-Like Minor Planet by a White DwarfFeb 01 2011We present optical and infrared characterization of the polluted DAZ white dwarf GALEX J193156.8+011745. Imaging and spectroscopy from the ultraviolet to the thermal infrared indicates that the white dwarf hosts excess infrared emission consistent with ... More
A Linear Programming Formulation for Constrained Discounted Continuous Control for Piecewise Deterministic Markov ProcessesFeb 25 2014This papers deals with the constrained discounted control of piecewise deterministic Markov process (PDMPs) in general Borel spaces. The control variable acts on the jump rate and transition measure, and the goal is to minimize the total expected discounted ... More
Experimental Status of Neutrino PhysicsJul 17 2012After a fascinating phase of discoveries, neutrino physics still has a few mysteries such as the absolute mass scale, the mass hierarchy, the existence of CP violation in the lepton sector and the existence of right-handed neutrinos. It is also entering ... More
La formule de la trace pour les tissus planairesMay 01 2015We give a complete proof of the fact that the trace of the curvature of the connection associated to a planar d-web (d>3) is the sum of the Blaschke curvatures of its sub 3-webs.
Gaseous Material Orbiting the Polluted, Dusty White Dwarf HE1349-2305Apr 05 2012We present new spectroscopic observations of the polluted, dusty, helium-dominated atmosphere white dwarf star HE1349-2305. Optical spectroscopy reveals weak CaII infrared triplet emission indicating that metallic gas debris orbits and is accreted by ... More
Circular Nim GamesNov 01 2012A circular Nim game is a two player impartial combinatorial game consisting of n stacks of tokens placed in a circle. A move consists of choosing k consecutive stacks, and taking at least one token from one or more of the k stacks. The last player able ... More
Stabilisation of the chiral phase of the SU($N=6m$) Heisenberg model on the honeycomb lattice at filling $m\geq 2$Jul 18 2016We show that, when $N$ is a multiple of 6 ($N=6m$, $m$ integer), the \SU{N} Heisenberg model on the honeycomb lattice with $m$ particles per site has a clear tendency toward chiral order as soon as $m\geq 2$. This conclusion has been reached by a systematic ... More
Quantum Reflection of Antihydrogen in the GBAR ExperimentDec 20 2013In the GBAR experiment, cold antihydrogen atoms will be left to fall on an annihilation plate with the aim of measuring the gravitational acceleration of antimatter. Here, we study the quantum reflection of these antiatoms due to the Casimir-Polder potential ... More
Anderson localization of pairs in bichromatic optical latticesJun 01 2012Oct 16 2012We investigate the formation of bound states made of two interacting atoms moving in a one dimensional (1D) quasi-periodic optical lattice. We derive the quantum phase diagram for Anderson localization of both attractively and repulsively bound pairs. ... More
The realistic collective nuclear HamiltonianMay 08 1995The residual part of the realistic forces ---obtained after extracting the monopole terms responsible for bulk properties--- is strongly dominated by pairing and quadrupole interactions, with important $\sigma\tau\cdot\sigma \tau$, octupole and hexadecapole ... More
Synthesis of Membrane-Electrode Assembly for Fuel Cells by Means of (Sub)-Atmospheric Plasma ProcessesFeb 06 2018An easy procedure to build up membrane-electrode assemblies for applications dedicated to miniaturized PEMFC using H2 or CH3OH by a two-steps atmospheric plasma process is reported. Firstly, catalyst nanoparticles are grafted on carbon substrates by spraying ... More
On the expected total reward with unbounded returns for Markov decision processesDec 21 2017Oct 05 2018We consider a discrete-time Markov decision process with Borel state and action spaces. The performance criterion is to maximize a total expected {utility determined by unbounded return function. It is shown the existence of optimal strategies under general ... More
Legendre transformation and lifting of multi-vectorsFeb 03 2005Feb 21 2005This paper has three objectives. First to recall the link between the classical Legendre-Fenschel transformation and a useful isomorphism between 1-jets of functions on a vector bundle and on its dual. As a particular consequence we obtain the classical ... More
From Shock Breakout to Peak and Beyond: Extensive Panchromatic Observations of the Type Ib Supernova 2008D associated with Swift X-ray Transient 080109May 15 2008Jun 17 2009We present extensive early photometric (ultraviolet through near-infrared) and spectroscopic (optical and near-infrared) data on supernova (SN) 2008D as well as X-ray data analysis on the associated Swift/X-ray transient (XRT) 080109. Our data span a ... More
Multiwavelength Observations of the Hot DB Star PG 0112+104Jun 02 2010We present a comprehensive multiwavelength analysis of the hot DB white dwarf PG 0112+104. Our analysis relies on newly-acquired FUSE observations, on medium-resolution FOS and GHRS data, on archival high-resolution GHRS observations, on optical spectrophotometry ... More
Model Atmosphere Analysis of the Weakly Magnetic DZ White Dwarf G165-7Aug 02 2006A reanalysis of the strongly metal-blanketed DZ white dwarf G165-7 is presented. An improved grid of model atmospheres and synthetic spectra is used to analyze BVRI, JHK, and ugriz photometric observations as well as a high quality Sloan Digital Sky Survey ... More
The Solar Neighborhood. XXI. Parallax Results from the CTIOPI 0.9m Program: 20 New Members of the 25 Parsec White Dwarf SampleFeb 03 2009We present accurate trigonometric parallaxes for 20 new members of the 25 pc white dwarf sample as part of the DENSE project (Discovery and Evalution of Nearby Stellar Embers, Previously, there were a total of 112 white dwarf ... More
Characterization of Flexible RF Microcoil Dedicated to Surface MriNov 21 2007In Magnetic Resonance Imaging (MRI), to achieve sufficient Signal to Noise Ratio (SNR), the electrical performance of the RF coil is critical. We developed a device (microcoil) based on the original concept of monolithic resonator. This paper presents ... More
A spectroscopy approach to measure the gravitational mass of antihydrogenMar 19 2014We study a method to induce resonant transitions between antihydrogen ($\bar{H}$) quantum states above a material surface in the gravitational field of the Earth. The method consists of applying a gradient of magnetic field, which is temporally oscillating ... More
Deviations from He I Case B Recombination Theory and Extinction Corrections in the Orion NebulaOct 20 2006We are engaged in a comprehensive program to find reliable elemental abundances in and to probe the physical structure of the Orion Nebula, the brightest and best-resolved H II region. In the course of developing a robust extinction correction covering ... More
Experimental Plan to Verify the YPCP Model: "Yukawa Pico Chemistry and Physics" Implications in the CF-Lenr FieldOct 06 2008In the CF-LERN field (Cold Fusion and Low Energy Nuclear reactions) many experimental results are available: unexplained energy production, presence of unusual patterns of classical fusion reaction products, isotopic composition variations, sporadic emission ... More
Nambu structures and integrable 1-formsFeb 21 2000Mar 02 2000Some years ago Mosh\'e Flato pointed up that it could be interesting to develop the Nambu's idea to generalize Hamiltonian mechanic. An interesting new formalism in that direction was proposed by T. Takhtajan. His theory gave new perspectives concerning ... More
Courbure des tissus planaires définis implicitement par une équation différentielle polynomiale en y'. ProgrammationMay 01 2015The aim of this paper is mainly, after some theoretical explanations, to provide a program on Maple for computing, whatever be d, the curvature of the planar d-web implicitely defined by a differential equation F(x,y,y')=0, F being polynomial of degree ... More
Integrated micro-plasmas in silicon operating in heliumApr 29 2016Microplasma arrays operating in helium in a DC regime have been produced in silicon microre-actors. Cathode boundary layer (CBL) type microdevices were elaborated using clean room facilities and semiconductor processing techniques. Ignition of the micro-discharge ... More
On the Spectral Evolution of Cool, Helium-Atmosphere White Dwarfs: Detailed Spectroscopic and Photometric Analysis of DZ StarsMar 29 2007We present a detailed analysis of a large spectroscopic and photometric sample of DZ white dwarfs based on our latest model atmosphere calculations. We revise the atmospheric parameters of the trigonometric parallax sample of Bergeron, Leggett, & Ruiz ... More
Temperature Variations from HST Spectroscopy of the Orion NebulaDec 10 2002We present HST/STIS long-slit spectroscopy of NGC 1976. Our goal is to measure the intrinsic line ratio [O III] 4364/5008 and thereby evaluate the electron temperature (T_e) and the fractional mean-square T_e variation (t_A^2) across the nebula. We also ... More
Topological rigidity for certain families of differentiable plane curvesJun 15 1999We show that the topological classification and the smooth classification are generically the same for certain families of plane curves in a semi-local case(the double local case). Especially we give the normal form of transversely jointed two families ... More
Des séries de tissus ordinaires de rang maximum en toute dimensionNov 04 2014In this paper, we define, from a finite set E of functions, a family of holomorphic webs ${\cal W}(n;E)$ of codimension one in any dimension $ n $. We prove that it is sufficient to check a finite number of conditions for these webs to be all ordinary ... More
Infrared Spectroscopy of Atomic Lines in Gaseous NebulaeSep 23 2001Spectroscopy in the infrared provides a means to assess important properties of the plasma in gaseous nebulae. We present some of our own work that illustrates the need for interactions between the themes of this conference - astronomical data, atomic ... More
SDSS J074511.56+194926.5: Discovery of a Metal-Rich and Tidally Distorted Extremely Low Mass White DwarfDec 05 2013Dec 16 2013We present the discovery of an unusual, tidally-distorted extremely low mass white dwarf (WD) with nearly solar metallicity. Radial velocity measurements confirm that this is a compact binary with an orbital period of 2.6975 hrs and a velocity semi-amplitude ... More
A discussion of stock market speculation by Pierre-Joseph ProudhonMay 03 2010The object of this contribution is to present the ideas behind the thinking of the French economist Pierre-Joseph Proudhon (1809-1865) in relation to the causes and effects of Stock market speculation. It is based upon the works of this author but particularly ... More
Numerical method for impulse control of Piecewise Deterministic Markov ProcessesNov 26 2010Aug 30 2011This paper presents a numerical method to calculate the value function for a general discounted impulse control problem for piecewise deterministic Markov processes. Our approach is based on a quantization technique for the underlying Markov chain defined ... More
Impulsive control for continuous-time Markov Decision ProcessesFeb 25 2014The objective of this work is to study continuous-time Markov decision processes on a general Borel state space with both impulsive and continuous controls for the infinite-time horizon discounted cost. The continuous-time controlled process is shown ... More
Limits on the Number of Galactic Young Supernova Remnants Emitting in the Decay Lines of 44TiAug 22 2013We revise the assumptions of the parameters involved in predicting the number of supernova remnants detectable in the nuclear lines of the decay chain of 44Ti. Specifically, we consider the distribution of the supernova progenitors, the supernova rate ... More
Periodic vacuum and particles in two dimensionsMar 11 1999Dec 05 1999Different dynamical symmetry breaking patterns are explored for the two dimensional phi4 model with higher order derivative terms. The one-loop saddle point expansion predicts a rather involved phase structure and a new Gaussian critical line. This vacuum ... More
Calcul explicite de la courbure des tissus calibrés ordinairesAug 18 2014We present a MAPLE program for the explicit computation of the curvature of calibrated ordinary webs in codimension one in any dimension (recall that all planar webs are calibrated and ordinary). The vanishing of this curvature means the maximality of ... More
Stability of higher order singular points of Poisson manifolds and Lie algebroidsJan 11 2005Sep 06 2005We study the stability of singular points for smooth Poisson structures as well as general Lie algebroids. We give sufficient conditions for stability lying on the first (not necessarily linear) approximation of the given Poisson structure or Lie algebroid ... More
On the local structure of Dirac manifoldsMay 13 2004Jun 15 2004We give a local normal form for Dirac structures. As a consequence, we show that the dimensions of the pre-symplectic leaves of a Dirac manifold have the same parity. We also show that, given a point $m$ of a Dirac manifold $M$, there is a well-defined ... More
A Dark Spot on a Massive White DwarfNov 23 2015We present the serendipitous discovery of eclipse-like events around the massive white dwarf SDSS J152934.98+292801.9 (hereafter J1529+2928). We selected J1529+2928 for time-series photometry based on its spectroscopic temperature and surface gravity, ... More