Results for "P. Dufour"
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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. 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 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 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 SDSS DR7 White Dwarf CatalogDec 06 2012We present a new catalog of spectroscopically-confirmed white dwarf stars from the Sloan Digital Sky Survey Data Release 7 spectroscopic catalog. We find 20,407 white dwarf spectra, representing 19,712 stars, and provide atmospheric model fits to 14,120 ... 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 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 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 Signatures of indistinguishability in bosonic many-body dynamicsOct 24 2017Apr 20 2018The dynamics of bosons in generic multimode systems, such as Bose-Hubbard models, is not only determined by interactions among the particles, but also by their mutual indistinguishability manifested in many-particle interference. We introduce a measure ... 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 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 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 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 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 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 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 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 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 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 Power-of-$d$-Choices with Memory: Fluid Limit and OptimalityFeb 19 2018Apr 23 2019In 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 A step to Gronwall's conjectureJun 27 2019In this paper we will explore a way to prove the hundred years old Gronwall's conjecture: if two plane linear 3-webs with non-zero curvature are locally isomorphic, then the isomorphism is a homography. Using recent results of S. I. Agafonov, we exhibit ... More Johnson-Kendall-Roberts theory applied to living cellsOct 03 2005Johnson-Kendall-Roberts (JKR) theory is an accurate model for strong adhesion energies of soft slightly deformable material. Little is known about the validity of this theory on complex systems such as living cells. We have addressed this problem using ... 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 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 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 Les isomorphismes infinitésimaux des tissus de codimension 1Jan 19 2017We study local ($n+1$)-webs of codimension 1 on a manifold of dimension $n.$ We give a complete description of their possible Lie algebras of infinitesimal diffeomorphisms. More precisely we show that these Lie algebras are direct products of sub-algebras ... 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 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 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 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 The PICARD Payload Data CentreSep 20 2017PICARD is a scientific space mission dedicated to the study of the solar variability origin. A French micro-satellite will carry an imaging telescope for measuring the solar diameter, limb shape and solar oscillations, and two radiometers for measuring ... More