Haro15: Is it actually a low metallicity galaxy?

We present a detailed study of the physical properties of the nebular material in multiple knots of the blue compact dwarf galaxy Haro 15. Using long slit and echelle spectroscopy, obtained at Las Campanas Observatory, we study the physical conditions (electron density and temperature), ionic and total chemical abundances of several atoms, reddening and ionization structure. The latter was derived by comparing the oxygen and sulphur ionic ratios to their corresponding observed emission line ratios (the eta and eta' plots) in different regions of the galaxy. Applying direct and empirical methods for abundance determination, we perform a comparative analysis between these regions.Comment: (Poster paper) 2 pages, 2 figure

The IACOB project: A grid-based automatic tool for the quantitative spectroscopic analysis of O-stars

We present the IACOB grid-based automatic tool for the quantitative spectroscopic analysis of O-stars. The tool consists of an extensive grid of FASTWIND models, and a variety of programs implemented in IDL to handle the observations, perform the automatic analysis, and visualize the results. The tool provides a fast and objective way to determine the stellar parameters and the associated uncertainties of large samples of O-type stars within a reasonable computational time.Comment: 8 pages, 2 figures, 1 table. Proceedings of the "GREAT-ESF Stellar Atmospheres in the Gaia Era Workshop

Extracting topological features from dynamical measures in networks of Kuramoto oscillators

The Kuramoto model for an ensemble of coupled oscillators provides a paradigmatic example of non-equilibrium transitions between an incoherent and a synchronized state. Here we analyze populations of almost identical oscillators in arbitrary interaction networks. Our aim is to extract topological features of the connectivity pattern from purely dynamical measures, based on the fact that in a heterogeneous network the global dynamics is not only affected by the distribution of the natural frequencies, but also by the location of the different values. In order to perform a quantitative study we focused on a very simple frequency distribution considering that all the frequencies are equal but one, that of the pacemaker node. We then analyze the dynamical behavior of the system at the transition point and slightly above it, as well as very far from the critical point, when it is in a highly incoherent state. The gathered topological information ranges from local features, such as the single node connectivity, to the hierarchical structure of functional clusters, and even to the entire adjacency matrix.Comment: 11 pages, 10 figure

2D granular flows with the μ(I)\mu(I) rheology and side walls friction: a well balanced multilayer discretization

We present here numerical modelling of granular flows with the $\mu(I)$ rheology in confined channels. The contribution is twofold: (i) a model to approximate the Navier-Stokes equations with the $\mu(I)$ rheology through an asymptotic analysis. Under the hypothesis of a one-dimensional flow, this model takes into account side walls friction; (ii) a multilayer discretization following Fern\'andez-Nieto et al. (J. Fluid Mech., vol. 798, 2016, pp. 643-681). In this new numerical scheme, we propose an appropriate treatment of the rheological terms through a hydrostatic reconstruction which allows this scheme to be well-balanced and therefore to deal with dry areas. Based on academic tests, we first evaluate the influence of the width of the channel on the normal profiles of the downslope velocity thanks to the multilayer approach that is intrinsically able to describe changes from Bagnold to S-shaped (and vice versa) velocity profiles. We also check the well balance property of the proposed numerical scheme. We show that approximating side walls friction using single-layer models may lead to strong errors. Secondly, we compare the numerical results with experimental data on granular collapses. We show that the proposed scheme allows us to qualitatively reproduce the deposit in the case of a rigid bed (i. e. dry area) and that the error made by replacing the dry area by a small layer of material may be large if this layer is not thin enough. The proposed model is also able to reproduce the time evolution of the free surface and of the flow/no-flow interface. In addition, it reproduces the effect of erosion for granular flows over initially static material lying on the bed. This is possible when using a variable friction coefficient $\mu(I)$ but not with a constant friction coefficient

Fast generation of spin-squeezed states in bosonic Josephson junctions

We describe methods for fast production of highly coherent-spin-squeezed many-body states in bosonic Josephson junctions (BJJs). We start from the known mapping of the two-site Bose-Hubbard (BH) Hamiltonian to that of a single effective particle evolving according to a Schr\"odinger-like equation in Fock space. Since, for repulsive interactions, the effective potential in Fock space is nearly parabolic, we extend recently derived protocols for shortcuts to adiabatic evolution in harmonic potentials to the many-body BH Hamiltonian. The best scaling of the squeezing parameter for large number of atoms N is \xi^2_S ~ 1/N.Comment: Improved and enlarged version, accepted at Phys. Rev.

Analysis and test of the central-blue-spot infall hallmark

The infall of material onto a protostar, in the case of optically thick line emission, produces an asymmetry in the blue- and red-wing line emission. For an angularly resolved emission, this translates in a blue central spot in the first-order moment (intensity weighted velocity) map. An analytical expression for the first-order moment intensity as a function of the projected distance was derived, for the cases of infinite and finite infall radius. The effect of a finite angular resolution, which requires the numerical convolution with the beam, was also studied. This method was applied to existing data of several star-forming regions, namely G31.41+0.31 HMC, B335, and LDN 1287, obtaining good fits to the first-order moment intensity maps, and deriving values of the central masses onto which the infall is taking place (G31.41+0.31 HMC: 70-120 $M_\odot$; B335: 0.1 $M_\odot$; Guitar Core of LDN 1287: 4.8 $M_\odot$). The central-blue-spot infall hallmark appears to be a robust and reliable indicator of infall.Comment: Accepted for publication in A&

Testing models with non-minimal Higgs sector through the decay t->q+WZ

We study the contribution of charged Higgs boson to the rare decay of the top quark t->q+WZ (q=d,s,b) in models with Higgs sector that includes doublets and triplets. Higgs doublets are needed to couple charged Higgs with quarks, whereas the Higgs triplets are required to generate the non-standard vertex HWZ at tree-level. It is found that within a model that respect the custodial SU(2) symmetry and avoids flavour changing neutral currents by imposing discrete symmetries, the decay mode t->b+WZ, can reach a branching ratio of order 0.0178, whereas the decay modes t->(d,s)+WZ, can reach a similar branching ratio in models where flavour changing neutral currents are suppressed by flavour symmetries.Comment: Typeset using REVTEX and EPSF, 5 pag, 2 figure