959 research outputs found

    A multispectral view of the periodic events in eta Carinae

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    A full description of the 5.5-yr low excitation events in Eta Carinae is presented. We show that they are not as simple and brief as previously thought, but a combination of two components. The first, the 'slow variation' component, is revealed by slow changes in the ionization level of circumstellar matter across the whole cycle and is caused by gradual changes in the wind-wind collision shock-cone orientation, angular opening and gaseous content. The second, the 'collapse' component, is restricted to around the minimum, and is due to a temporary global collapse of the wind-wind collision shock. High energy photons (E > 16 eV) from the companion star are strongly shielded, leaving the Weigelt objects at low ionization state for >6 months. High energy phenomena are sensitive only to the 'collapse', low energy only to the 'slow variation' and intermediate energies to both components. Simple eclipses and mechanisms effective only near periastron (e.g., shell ejection or accretion onto the secondary star) cannot account for the whole 5.5-yr cycle. We find anti-correlated changes in the intensity and the radial velocity of P Cygni absorption profiles in FeII 6455 and HeI 7065 lines, indicating that the former is associated to the primary and the latter to the secondary star. We present a set of light curves representative of the whole spectrum, useful for monitoring the next event (2009 January 11).Comment: 16 pages, 7 EPS figures, accepted for publication on MNRA

    MINERvA neutrino detector response measured with test beam data

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    The MINERvA collaboration operated a scaled down replica of the solid scintillator tracking and sampling calorimeter regions of the MlNERvA detector in a hadron test beam at the Fermilab Test Beam Facility. This paper reports measurements with samples of protons, pions, and electrons from 0.35 to 2.0 GeV/c momentum. The calorimetric response to protons, pions, and electrons is obtained from these data. A measurement of the parameter in Birks\u27 law and an estimate of the tracking efficiency are extracted from the proton sample. Overall the data are well described by a Geant4-based Monte Carlo simulation of the detector and particle interactions with agreements better than 4% for the calorimetric response, though some features of the data are not precisely modeled. These measurements are used to tune the MINERvA detector simulation and evaluate systematic uncertainties in support of the MINERvA neutrino cross-section measurement program. (C) 2015 Published by Elsevier B.V

    CAD modeling, multibody system formalisms and visualization : an integrated approach

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    In this paper an integrated approach of CAD (Computer Aided Design) modeling, generation of equations of motion, simulation and visualization of multibody systems is described. An object-oriented data model for different multibody formalisms is integrated in a commercially available CAD-3D-system. With respect to existing CAD-interfaces, different solid model design methods and various visualization demands the datamodel allow, multi body modeling with a direct interface to a data base. Different software tools like an integrated Newton-Euler formalism are able to use immediately the parametrized multi body system data base. For multibody systems with closed kinematic loops a set of ordinary differential equations and decoupled algebraic equations is formulated automatically which can be solved with explicit multistep integration algorithms. This is achieved by a minimal set of generalized coordinates being specified during the numerical integration. A additional interface provides data for visualization from the simulation tool

    MINERvA neutrino detector response measured with test beam data

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    The MINERvA collaboration operated a scaled-down replica of the solid scintillator tracking and sampling calorimeter regions of the MINERvA detector in a hadron test beam at the Fermilab Test Beam Facility. This article reports measurements with samples of protons, pions, and electrons from 0.35 to 2.0 GeV/c momentum. The calorimetric response to protons, pions, and electrons are obtained from these data. A measurement of the parameter in Birks' law and an estimate of the tracking efficiency are extracted from the proton sample. Overall the data are well described by a Geant4-based Monte Carlo simulation of the detector and particle interactions with agreements better than 4%, though some features of the data are not precisely modeled. These measurements are used to tune the MINERvA detector simulation and evaluate systematic uncertainties in support of the MINERvA neutrino cross section measurement program.Comment: as accepted by NIM
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