137 research outputs found

    Precise radial velocities of giant stars. X. Bayesian stellar parameters and evolutionary stages for 372 giant stars from the Lick planet search

    Full text link
    The determination of accurate stellar parameters of giant stars is essential for our understanding of such stars in general and as exoplanet host stars in particular. Precise stellar masses are vital for determining the lower mass limit of potential substellar companions with the radial velocity method. Our goal is to determine stellar parameters, including mass, radius, age, surface gravity, effective temperature and luminosity, for the sample of giants observed by the Lick planet search. Furthermore, we want to derive the probability of these stars being on the horizontal branch (HB) or red giant branch (RGB), respectively. We compare spectroscopic, photometric and astrometric observables to grids of stellar evolutionary models using Bayesian inference. We provide tables of stellar parameters, probabilities for the current post-main sequence evolutionary stage, and probability density functions for 372 giants from the Lick planet search. We find that 81%81\% of the stars in our sample are more probably on the HB. In particular, this is the case for 15 of the 16 planet host stars in the sample. We tested the reliability of our methodology by comparing our stellar parameters to literature values and find very good agreement. Furthermore, we created a small test sample of 26 giants with available asteroseismic masses and evolutionary stages and compared these to our estimates. The mean difference of the stellar masses for the 24 stars with the same evolutionary stages by both methods is only ΔM=0.01±0.20  M\langle\Delta M\rangle=0.01\pm0.20\;\mathrm{M_\odot}. We do not find any evidence for large systematic differences between our results and estimates of stellar parameters based on other methods. In particular we find no significant systematic offset between stellar masses provided by asteroseismology to our Bayesian estimates based on evolutionary models.Comment: 15 pages, 7 figures, accepted for publication in A&

    Bose-Einstein condensates in fast rotation

    Full text link
    In this short review we present our recent results concerning the rotation of atomic Bose-Einstein condensates confined in quadratic or quartic potentials, and give an overview of the field. We first describe the procedure used to set an atomic gas in rotation and briefly discuss the physics of condensates containing a single vortex line. We then address the regime of fast rotation in harmonic traps, where the rotation frequency is close to the trapping frequency. In this limit the Landau Level formalism is well suited to describe the system. The problem of the condensation temperature of a fast rotating gas is discussed, as well as the equilibrium shape of the cloud and the structure of the vortex lattice. Finally we review results obtained with a quadratic + quartic potential, which allows to study a regime where the rotation frequency is equal to or larger than the harmonic trapping frequency.Comment: Laser Physics Letters 2, 275 (2005

    Observation of Phase Defects in Quasi-2D Bose-Einstein Condensates

    Full text link
    We have observed phase defects in quasi-2D Bose-Einstein condensates close to the condensation temperature. Either a single or several equally spaced condensates are produced by selectively evaporating the sites of a 1D optical lattice. When several clouds are released from the lattice and allowed to overlap, dislocation lines in the interference patterns reveal nontrivial phase defects

    Precise radial velocities of giant stars. XI. Two brown dwarfs in 6:1 mean motion resonance around the K giant star ν\nu Ophiuchi

    Full text link
    We present radial-velocity (RV) measurements for the K giant ν\nu Oph (= HIP88048, HD163917, HR6698), which reveal two brown dwarf companions with a period ratio close to 6:1. For our orbital analysis we use 150 precise RV measurements taken at Lick Observatory between 2000 and 2011, and we combine them with RV data for this star available in the literature. Using a stellar mass of M=2.7MM = 2.7\,M_\odot for ν\nu Oph and applying a self-consistent N-body model we estimate the minimum dynamical companion masses to be m1sini22.2MJupm_1\sin i \approx 22.2\,M_{\mathrm{Jup}} and m2sini24.7MJupm_2\sin i \approx 24.7\,M_{\mathrm{Jup}}, with orbital periods P1530P_1 \approx 530 d and P23185P_2 \approx 3185 d. We study a large set of potential orbital configurations for this system, employing a bootstrap analysis and a systematic χν2\chi_{\nu}^2 grid-search coupled with our dynamical fitting model, and we examine their long-term stability. We find that the system is indeed locked in a 6:1 mean motion resonance (MMR), with Δω\Delta \omega and all six resonance angles θ1,,θ6\theta_{1}, \ldots, \theta_{6} librating around 0^\circ. We also test a large set of coplanar inclined configurations, and we find that the system will remain in a stable resonance for most of these configurations. The ν\nu Oph system is important for probing planetary formation and evolution scenarios. It seems very likely that the two brown dwarf companions of ν\nu Oph formed like planets in a circumstellar disk around the star and have been trapped in a MMR by smooth migration capture.Comment: 17 pages, 9 figures. New version with corrected number in title. No other change

    Interference of an array of independent Bose-Einstein condensates

    Full text link
    We have observed high-contrast matter wave interference between 30 Bose-Einstein condensates with uncorrelated phases. Interference patterns were observed after independent condensates were released from a one-dimensional optical lattice and allowed to expand and overlap. This initially surprising phenomenon is explained with a simple theoretical model which generalizes the analysis of the interference of two independent condensates

    Seeing zeros of random polynomials: quantized vortices in the ideal Bose gas

    Full text link
    We propose a physical system allowing one to experimentally observe the distribution of the complex zeros of a random polynomial. We consider a degenerate, rotating, quasi-ideal atomic Bose gas prepared in the lowest Landau level. Thermal fluctuations provide the randomness of the bosonic field and of the locations of the vortex cores. These vortices can be mapped to zeros of random polynomials, and observed in the density profile of the gas.Comment: 4 page

    Personalized medicine: consequences for drug research and therapy

    Get PDF
    In drug research, a serious transformation has taken place. With increasing knowledge gained from molecular medicine, it became possible to refine and develop new therapies based on the molecular mechanisms of diseases. Medicine and drug development have seen a paradigm shift which can be characterized with the catchword “personalized medicine”, also called “stratified medicine” or “precision medicine”. Personalized medicine is based on defined tandems of therapeutic agents and diagnostic tests. With this addition to the regular medical examination of the patient, specific patient characteristics are determined. The results of such diagnostic tests are then decisive for the choice of therapy or control of the effectiveness of the chosen treatment. The benefit of personalized medicine for the patient is the higher probability of treatment success as well as improved effectiveness and reduced / avoided side effects. Health insurance systems and the public may have the advantage that the health funds can be used more efficiently on this basis. This new paradigm requires also a new debate on the remuneration in health care. In order to bring personalized therapies to patients as quickly as possible, all players in health care should work together to address the challenges associated with personalized medicine

    ВЛИЯНИЕ ТРАНСПОРТНыХ ЗАДЕРЖЕК ШЛАМОВыХ ПОТОКОВ НА ПРОДОЛЖИТЕЛЬНОСТЬ НЕСТАЦИОНАРНОГО РЕЖИМА РАБОТы ВОДНО-ШЛАМОВыХ СИСТЕМ

    No full text
    Проблема и ее связь с научными и практическими задачами. Все подре-шетные воды гравитационного отделения аккумулируются в зумпфах большой емкости и далее перекачиваются на операцию предварительной регенерации в гидроциклоны, классификаторы или сгустители. При этом необходимо обеспе-чить подачу на самую верхнюю отметку для дальнейшего распределения шла-мовых потоков самотеком. Как правило, такие потоки характеризуются высо-кими транспортными задержками. Магистрали для шламовых потоков перед узлами вывода имеют меньшие геометрические размеры, переносят незначи-тельное количество пульпы по сравнению с вводными коммуникациями

    New HARPS and FEROS observations of GJ1046

    Full text link
    In this paper we present new precise Doppler data of GJ1046 taken between November 2005 and July 2018 with the HARPS and the FEROS high-resolution spectographs. In addition, we provide a new stellar mass estimate of GJ1046 and we update the orbital parameters of the GJ1046 system. These new data and analysis could be used together with the GAIA epoch astrometry, when available, for braking the sini\sin i degeneracy and revealing the true mass of the GJ1046 system.Comment: 2 pages, 1 figure, 1 table with RV data (available only in the Astro-PH version of the paper), Accepted by RNAA
    corecore