Spectral classification of stars using synthetic model atmospheres

We devised a straightforward procedure to derive the atmosphere fundamental parameters of stars across the different MK spectral types by comparing mid-resolution spectroscopic observations with theoretical grids of synthetic spectra.The results of a preliminary experiment, by matching the Gunn and Stryker and Jacoby et al. spectrophotometric atlases with the Kurucz models, are briefly discussed. For stars in the A-K spectral range, effective temperature is obtained within a 1-2% relative uncertainty (at 2 sigma confidence level). This value raises to 4-5% for the hottest stars in the samples (O-B spectral types). A poorer fit is obtained throughout for stars cooler than 4000 K mainly due to the limiting input physics in the Kurucz models.Comment: 6 pages, 3 figures; Proc. of the 1st COROT-MONS Ground-Support Observations Workshop (Ghent 11-12/01/2001), Ed. C. Sterken, Brussel Univ., 2001, in preparatio

Implications of hydrodynamical simulations for the interpretation of direct dark matter searches

In recent years, realistic hydrodynamical simulations of galaxies like the Milky Way have become available, enabling a reliable estimate of the dark matter density and velocity distribution in the Solar neighborhood. We review here the status of hydrodynamical simulations and their implications for the interpretation of direct dark matter searches. We focus in particular on: the criteria to identify Milky Way-like galaxies; the impact of baryonic physics on the dark matter velocity distribution; the possible presence of substructures like clumps, streams, or dark disks; and on the implications for the direct detection of dark matter with standard and non-standard interactions.Comment: 31 pages, 7 figures, 3 tables; v2: added Sec. 6.2 and Fig. 3, version accepted for publication in IJMP

Relativistic Thomas-Fermi Model at Finite Temperatures

We briefly review the Thomas-Fermi statistical model of atoms in the classical non-relativistic formulation and in the generalised finite-nucleus relativistic formulation. We then discuss the classical generalisation of the model to finite temperatures in the non-relativistic approximation and present a new relativistic model at finite temperatures, investigating how to recover the existing theory in the limit of low temperatures. This work is intended to be a propedeutical study for the evaluation of equilibrium configurations of relativistic ``hot'' white dwarfs.Comment: 8 pages, Latex wsp9.cls. Proceedings Marcel Grossmann IX, Rome (Italy), 2-9 July 2000 (World Scientific

Parton Distributions with the Combined HERA Charm Production Cross Sections

Heavy quark structure functions from HERA provide a direct handle on the medium and small-x gluon PDF. In this contribution, we discuss ongoing progress on the implementation of the FONLL General-Mass scheme with running heavy quark masses, and of its benchmarking with the HOPPET and OpenQCDrad codes, and then present the impact of the recently released combined HERA charm production cross sections in the NNPDF2.3 analysis. We find that the combined charm data contribute to constraining the gluon and quarks at small values of Bjorken-x.Comment: 4 pages, 2 figures, 2 tables, contribution to the proceedings of the DIFFRACTION 2012 Workshop, Sep 10-15, Puerto del Carmen, Spai

On the dimension of the minimal vertex covers semigroup ring of an unmixed bipartite graph

In a paper in 2008, Herzog, Hibi and Ohsugi introduced and studied the semigroup ring associated to the set of minimal vertex covers of an unmixed bipartite graph. In this paper we relate the dimension of this semigroup ring to the rank of the Boolean lattice associated to the graph.Comment: 6 pages, Pragmatic 2008, University of Catania (Italy); corrected typo

Dynamical constraints on the dark matter distribution in the Milky Way

An accurate knowledge of the dark matter distribution in the Milky Way is of crucial importance for galaxy formation studies and current searches for particle dark matter. In this paper we set new dynamical constraints on the Galactic dark matter profile by comparing the observed rotation curve, updated with a comprehensive compilation of kinematic tracers, with that inferred from a wide range of observation-based morphologies of the bulge, disc and gas. The generalised Navarro-Frenk-White (NFW) and Einasto dark matter profiles are fitted to the data in order to determine the favoured ranges of local density, slope and scale radius. For a representative baryonic model, a typical local circular velocity of 230 km/s and a distance of the Sun to the Galactic centre of 8 kpc, we find a local dark matter density of 0.420+0.021-0.018 (2 sigma) +- 0.025 GeV/cm^3 (0.420+0.019-0.021 (2 sigma) +- 0.026 GeV/cm^3) for NFW (Einasto), where the second error is an estimate of the systematic due to baryonic modelling. Apart from the Galactic parameters, the main sources of uncertainty inside and outside the solar circle are baryonic modelling and rotation curve measurements, respectively. Upcoming astronomical observations are expected to reduce all these uncertainties substantially over the coming years.Comment: 10 pages, 5 figures, 2 tables, matches published versio