16,574 research outputs found

    The Impact of Transiting Planet Science on the Next Generation of Direct-Imaging Planet Searches

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    Within the next five years, a number of direct-imaging planet search instruments, like the VLT SPHERE instrument, will be coming online. To successfully carry out their programs, these instruments will rely heavily on a-priori information on planet composition, atmosphere, and evolution. Transiting planet surveys, while covering a different semi-major axis regime, have the potential to provide critical foundations for these next-generation surveys. For example, improved information on planetary evolutionary tracks may significantly impact the insights that can be drawn from direct-imaging statistical data. Other high-impact results from transiting planet science include information on mass-to-radius relationships as well as atmospheric absorption bands. The marriage of transiting planet and direct-imaging results may eventually give us the first complete picture of planet migration, multiplicity, and general evolution.Comment: 4 pages, 3 figures, IAU Transiting Planets Proceedings, in pres

    Quantum Phonon Optics: Coherent and Squeezed Atomic Displacements

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    In this paper we investigate coherent and squeezed quantum states of phonons. The latter allow the possibility of modulating the quantum fluctuations of atomic displacements below the zero-point quantum noise level of coherent states. The expectation values and quantum fluctuations of both the atomic displacement and the lattice amplitude operators are calculated in these states---in some cases analytically. We also study the possibility of squeezing quantum noise in the atomic displacement using a polariton-based approach.Comment: 6 pages, RevTe

    Phonon Transmission Rate, Fluctuations, and Localization in Random Semiconductor Superlattices: Green's Function Approach

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    We analytically study phonon transmission and localization in random superlattices by using a Green's function approach. We derive expressions for the average transmission rate and localization length, or Lyapunov exponent, in terms of the superlattice structure factor. This is done by considering the backscattering of phonons, due to the complex mass density fluctuations, which incorporates all of the forward scattering processes. These analytical results are applied to two types of random superlattices and compared with numerical simulations based on the transfer matrix method. Our analytical results show excellent agreement with the numerical data. A universal relation for the transmission fluctuations versus the average transmission is derived explicitly, and independently confirmed by numerical simulations. The transient of the distribution of transmission to the log-normal distribution for the localized phonons is also studied.Comment: 36 pages, Late

    ALMA Observations of the Gravitational Lens SDP.9

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    We present long-baseline ALMA observations of the strong gravitational lens H-ATLAS J090740.0-004200 (SDP.9), which consists of an elliptical galaxy at zL=0.6129z_{\mathrm{L}}=0.6129 lensing a background submillimeter galaxy into two extended arcs. The data include Band 6 continuum observations, as well as CO JJ=6-5 molecular line observations, from which we measure an updated source redshift of zS=1.5747z_{\mathrm{S}}=1.5747. The image morphology in the ALMA data is different from that of the HST data, indicating a spatial offset between the stellar, gas, and dust component of the source galaxy. We model the lens as an elliptical power law density profile with external shear using a combination of archival HST data and conjugate points identified in the ALMA data. Our best model has an Einstein radius of θE=0.66±0.01\theta_{\mathrm{E}}=0.66\pm0.01 and a slightly steeper than isothermal mass profile slope. We search for the central image of the lens, which can be used constrain the inner mass distribution of the lens galaxy including the central supermassive black hole, but do not detect it in the integrated CO image at a 3σ\sigma rms level of 0.0471 Jy km s1^{-1}.Comment: Accepted for publication in ApJL; 6 pages, 2 figures, 3 table

    Optical Spatial integration methods for ambiguity function generation

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    A coherent optical spatial integration approach to ambiguity function generation is described. It uses one dimensional acousto-optic Bragg cells as input tranducers in conjunction with a space variant linear phase shifter, a passive optical element, to generate the two dimensional ambiguity function in one exposure. Results of a real time implementation of this system are shown

    The SONYC survey: Towards a complete census of brown dwarfs in star forming regions

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    SONYC, short for "Substellar Objects in Nearby Young Clusters", is a survey program to provide a census of the substellar population in nearby star forming regions. We have conducted deep optical and near-infrared photometry in five young regions (NGC1333, rho Ophiuchi, Chamaeleon-I, Upper Sco, and Lupus-3), combined with proper motions, and followed by extensive spectroscopic campaigns with Subaru and VLT, in which we have obtained more than 700 spectra of candidate low-mass objects. We have identified and characterized more than 60 new substellar objects, among them a handful of objects with masses close to, or below the Deuterium burning limit. Through SONYC and surveys by other groups, the substellar IMF is now well characterized down to ~ 5 - 10 MJup, and we find that the ratio of the number of stars with respect to brown dwarfs lies between 2 and 6. A comprehensive survey of NGC 1333 reveals that, down to ~5MJup, free-floating objects with planetary masses are 20-50 times less numerous than stars, i.e. their total contribution to the mass budget of the clusters can be neglected.Comment: to appear in the proceedings of the conference 'Brown dwarfs come of age', May 20-24 2013, Memorie della Societa Astronomica Italian

    Electron Correlations in the Quasi-Two-Dimensional Organic Conductor θ\theta-(BEDT-TTF)2_{2}I3_{3} investigated by 13^{13}C NMR

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    We report a 13^{13}C-NMR study on the ambient-pressure metallic phase of the layered organic conductor θ\theta-(BEDT-TTF)2_{2}I3_{3} [BEDT-TTF: bisethylenedithio-tetrathiafulvalene], which is expected to connect the physics of correlated electrons and Dirac electrons under pressure. The orientation dependence of the NMR spectra shows that all BEDT-TTF molecules in the unit cell are to be seen equivalent from a microscopic point of view. This feature is consistent with the orthorhombic symmetry of the BEDT-TTF sublattice and also indicates that the monoclinic I3I_{3} sublattice, which should make three molecules in the unit cell nonequivalent, is not practically influential on the electronic state in the conducting BEDT-TTF layers at ambient pressure. There is no signature of charge disproportionation in opposition to most of the θ\theta-type BEDT-TTF salts. The analyses of NMR Knight shift, KK, and the nuclear spin-lattice relaxation rate, 1/T11/T_{1}, revealed that the degree of electron correlation, evaluated by the Korringa ratio [1/(T1TK2\varpropto 1/(T_{1}TK^{2})], is in an intermediate regime. However, NMR relaxation rate 1/T11/T_{1} is enhanced above \sim 200K, which possibly indicates that the system enters into a quantum critical regime of charge-order fluctuations as suggested theoretically.Comment: 19pages, 6figure
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