393 research outputs found

    Guide star catalogue data retrieval software 2

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    The Guide Star Catalog (GSC), being the largest astronomical catalog to date, is widely used by the astronomical community for all sorts of applications, such as statistical studies of certain sky regions, searches for counterparts to observational phenomena, and generation of finder charts. It's format (2 CD-ROM's) requires minimum hardware and is ideally suited for all sorts of conditions, especially observations. Unfortunately, the actual GSC data is not easily accessible. It takes the form of FITS tables, and the coordinates of the objects are given in one coordinate system (equinox 2000). The included reading software is rudimentary at best. Thus, even generation of a simple finder chart is not a trivial undertaking. To solve this problem, at least for PC users, GUIDARES was created. GUIDARES is a user-friendly program that lets you look directly at the data in the GSC, either as a graphical sky map or as a text table. GUIDARES can read a sampling of GSC data from a given sky region, store this sampling in a text file, and display a graphical map of the sampled region in projected celestial coordinates (perfect for finder charts). GUIDARES supports rectangular and circular regions defined by coordinates in the equatorial, ecliptic (any equinox) or galactic systems

    On the mechanism for breaks in the cosmic ray spectrum

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    The proof of cosmic ray (CR) origin in supernova remnants (SNR) must hinge on full consistency of the CR acceleration theory with the observations; direct proof is impossible because of the orbit stochasticity of CR particles. Recent observations of a number of galactic SNR strongly support the SNR-CR connection in general and the Fermi mechanism of CR acceleration, in particular. However, many SNR expand into weakly ionized dense gases, and so a significant revision of the mechanism is required to fit the data. We argue that strong ion-neutral collisions in the remnant surrounding lead to the steepening of the energy spectrum of accelerated particles by \emph{exactly one power}. The spectral break is caused by a partial evanescence of Alfven waves that confine particles to the accelerator. The gamma-ray spectrum generated in collisions of the accelerated protons with the ambient gas is also calculated. Using the recent Fermi spacecraft observation of the SNR W44 as an example, we demonstrate that the parent proton spectrum is a classical test particle power law E2\propto E^{-2}, steepening to E3E^{-3} at Ebr7GeVE_{br}\approx7GeV.Comment: APS talk to appear in PoP, 4 figure

    On the Structure and Scale of Cosmic Ray Modified Shocks

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    Strong astrophysical shocks, diffusively accelerating cosmic rays (CR) ought to develop CR precursors. The length of such precursor LpL_{p} is believed to be set by the ratio of the CR mean free path λ\lambda to the shock speed, i.e., Lpcλ/Vshcrg/VshL_{p}\sim c\lambda/V_{sh}\sim cr_{g}/V_{sh}, which is formally independent of the CR pressure PcP_{c}. However, the X-ray observations of supernova remnant shocks suggest that the precursor scale may be significantly shorter than LpL_{p} which would question the above estimate unless the magnetic field is strongly amplified and the gyroradius rgr_{g} is strongly reduced over a short (unresolved) spatial scale. We argue that while the CR pressure builds up ahead of the shock, the acceleration enters into a strongly nonlinear phase in which an acoustic instability, driven by the CR pressure gradient, dominates other instabilities (at least in the case of low β\beta plasma). In this regime the precursor steepens into a strongly nonlinear front whose size scales with \emph{the CR pressure}as LfLp(Ls/Lp)2(Pc/Pg)2L_{f}\sim L_{p}\cdot(L_{s}/L_{p})^{2}(P_{c}/P_{g})^{2}, where LsL_{s} is the scale of the developed acoustic turbulence, and Pc/PgP_{c}/P_{g} is the ratio of CR to gas pressure. Since LsLpL_{s}\ll L_{p}, the precursor scale reduction may be strong in the case of even a moderate gas heating by the CRs through the acoustic and (possibly also) the other instabilities driven by the CRs.Comment: EPS 2010 paper, to appear in PPC

    Eclipsing variables: Catalogue and classification

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    A new version of the Catalogue of Eclipsing Variables is presented. The catalogue contains parameters and morphological types of light curves for some 7200 stars. Spectral classification is also given when available. Recently published information about classification of 1352 systems is also included in the catalogue. Thus, the catalogue represents the largest list of eclipsing binaries classified from observations. The analysis of stellar parameter distributions of catalogued eclipsing systems has been performed, and an algorithm of eclipsing-variable classification has been developed. Classification of some systems is troublesome or contradictory due to lack of modern observational data or their possible rare evolutionary class. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    Nanofine spatial dissipative structures with azimutal lattice curvation

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    The nanofine spatial dissipative structures (NSDS) were characterized by transmission electron microscopy and electron diffraction. The NSDS obtained by thermogradiently processing an amorphous selenium film by unilateral heating of its lower surface at T = 413 K preliminarily. The results indicate that the NSDS of hexagonal selenium obtained in an amorphous film possess an azimuthal curvature of the lattice and a nonlinear fan-shaped system of flexural contours on their electron microscopic image. The lattice of the above NSDS undergoes elastic - plastic rotational curvature around three mutually perpendicular directions. The lattice rotation angles of hexagonal selenium NSDS reach: around [001], - 25 , around the direction perpendicular [001] and lying in the plane of the amorphous film - 32 , around the direction perpendicular to the first two ones and not lying in the plane of the amorphous film - azimuthal curvature of the lattice, - 35 . Thus, as a result of electron-microscopic and microdiffraction studies, it was found that NSDS of hexagonal selenium with azimuthal curvature of the lattice, causing the curvature of its habitus, are in a nonequilibrium state. © Published under licence by IOP Publishing Ltd

    Aperiodic Schrodinger Crystals

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    In 1945, E. Schrödinger predicted the possibility of the existence of "aperiodic crystals,"that is, more and more increasing crystalline aggregates, but without a simple lattice repetition mechanism. In the present work, such structures are experimentally prepared using selenium as an example. By thermal gradient treatment of the amorphous selenium film, we have obtained nano-thin spatial dissipative structures (SDS) of hexagonal selenium, the lattice of which undergoes non-uniform rotational curvature around, in the general case, three mutually perpendicular directions. The formation of these nano-thin SDS of hexagonal selenium occurs as a result of cooperative rotations of selenium macromolecules around, in general, three mutually perpendicular directions. Since nano-thin SDS after hardening in air have all the features of crystals each of the above nano-thin SDS of hexagonal selenium obtained at different annealing temperatures corresponds to the concept of "aperiodic crystals"Thus, "aperiodic crystals"were obtained experimentally, the possibility of the existence of which was predicted by E. Schrödinger. © Published under licence by IOP Publishing Ltd
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