1,110 research outputs found

    On a proper acute triangulation of a polyhedral surface

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    AbstractLet Σ be a polyhedral surface in R3 with n edges. Let L be the length of the longest edge in Σ, δ be the minimum value of the geodesic distance from a vertex to an edge that is not incident to the vertex, and θ be the measure of the smallest face angle in Σ. We prove that Σ can be triangulated into at most CLn/(δθ) planar and rectilinear acute triangles, where C is an absolute constant

    Reconstruction of the Structure of Accretion Disks in Dwarf Novae from the Multi-Band Light Curves of Early Superhumps

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    We propose a new method to reconstruct the structure of accretion disks in dwarf novae using multi-band light curves of early superhumps. Our model assumes that early superhumps are caused by the rotation effect of non-axisymmetrically flaring disks. We have developed a Bayesian model for this reconstruction, in which a smoother disk-structure tends to have a higher prior probability. We analyzed simultaneous optical and near-infrared photometric data of early superhumps of the dwarf nova, V455 And using this technique. The reconstructed disk has two flaring parts in the outermost region of the disk. These parts are responsible for the primary and secondary maxima of the light curves. The height-to-radius ratio is h/r=0.20-0.25 in the outermost region. In addition to the outermost flaring structures, flaring arm-like patterns can be seen in an inner region of the reconstructed disk. The overall profile of the reconstructed disk is reminiscent of the disk structure that is deformed by the tidal effect. However, an inner arm-like pattern, which is responsible for the secondary minimum in the light curve, cannot be reproduced only by the tidal effect. It implies the presence of another mechanism that deforms the disk structure. Alternatively, the temperature distribution of the disk could be non-axisymmetric. We demonstrate that the disk structure with weaker arm-like patterns is optimal in the model including the irradiation effect. However, the strongly irradiated disk gives quite blue colors, which may conflict with the observation. Our results suggest that the amplitude of early superhumps depends mainly on the height of the outermost flaring regions of the disk. We predict that early superhumps can be detected with an amplitude of >0.02 mag in about 90% of WZ Sge stars.Comment: 17 pages, 17 figures, accepted for publication in PAS

    Photometric Properties of Kiso Ultraviolet-Excess Galaxies in the Lynx-Ursa Major Region

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    We have performed a systematic study of several regions in the sky where the number of galaxies exhibiting star formation (SF) activity is greater than average. We used Kiso ultraviolet-excess galaxies (KUGs) as our SF-enhanced sample. By statistically comparing the KUG and non-KUG distributions, we discovered four KUG-rich regions with a size of 10×10\sim 10^\circ \times 10^\circ. One of these regions corresponds spatially to a filament of length 60h1\sim 60 h^{-1} Mpc in the Lynx-Ursa Major region (α9h10h,δ4248\alpha \sim 9^{\rm h} - 10^{\rm h}, \delta \sim 42^\circ - 48^\circ). We call this ``the Lynx-Ursa Major (LUM) filament''. We obtained V(RI)CV(RI)_{\rm C} surface photometry of 11 of the KUGs in the LUM filament and used these to investigate the integrated colors, distribution of SF regions, morphologies, and local environments. We found that these KUGs consist of distorted spiral galaxies and compact galaxies with blue colors. Their star formation occurs in the entire disk, and is not confined to just the central regions. The colors of the SF regions imply that active star formation in the spiral galaxies occurred 107810^{7 - 8} yr ago, while that of the compact objects occurred 106710^{6-7} yr ago. Though the photometric characteristics of these KUGs are similar to those of interacting galaxies or mergers, most of these KUGs do not show direct evidence of merger processes.Comment: 39 pages LaTeX, using aasms4.sty, 20 figures, ApJS accepted. The Title of the previous one was truncated by the author's mistake, and is corrected. Main body of the paper is unchange

    Optical and CO Radio Observations of Poor Cluster Zwicky 1615.8+3505

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    The cluster Zwicky 1615.8+3505 is considered to be a dynamically young poor cluster. To investigate the morphology and star-formation activity of galaxies under the environment of a dynamically young poor cluster, we have performed V, R, and I surface photometry, optical low-resolution spectroscopy, and 12CO (J=1-0) line observations for member galaxies. Our data show that more than 90% of the observed galaxies show regular morphologies and no star-formation activities, indicating that the environment does not affect these galaxy properties. Among sixteen galaxies observed, only NGC 6104 shows a significant star-formation activity, and shows a distorted morphology, indicating a tidal interaction. This galaxy contains double knots, and only one knot possesses Seyfert activity, though the sizes and luminosities are similar to each other; we also discuss this feature.Comment: LaTeX manuscript (text.tex, use PASJ style files), four PS figures (fig[a-d].ps), and three PASJ style files. text.tex, figb.ps, and figd.ps are up-dated. To be appeared in The Publications of the Astronomical Society of Japan, Vol. 51, No. 3 (1999 June issue

    A heavy Higgs boson from flavor and electroweak symmetry breaking unification

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    We present a unified picture of flavor and electroweak symmetry breaking based on a nonlinear sigma model spontaneously broken at the TeV scale. Flavor and Higgs bosons arise as pseudo-Goldstone modes. Explicit collective symmetry breaking yields stable vacuum expectation values and masses protected at one loop by the little-Higgs mechanism. The coupling to the fermions generates well-definite mass textures--according to a U(1) global flavor symmetry--that correctly reproduce the mass hierarchies and mixings of quarks and leptons. The model is more constrained than usual little-Higgs models because of bounds on weak and flavor physics. The main experimental signatures testable at the LHC are a rather large mass m_{h^0} = 317\pm 80 GeV for the (lightest) Higgs boson and a characteristic spectrum of new bosons and fermions at the TeV scale.Comment: 5 page

    Drug-induced pemphigus

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    Drug-induced pemphigus can be induced or triggered by drugs, most often by penicillamine and other thiol-associated drugs. The time from first intake of the drug to onset of the reaction is often relatively long compared to other cutaneous adverse drug reactions. Clinically it presents most often as pemphigus vulgaris or pemphigus foliaceus. Opposing to idiopathic pemphigus, pruritus, a prodromal stage and absence of mucosal involvement are regularly observed, while immunopathological findings are similar. The pathogenesis is not completely known, but probably includes endogenous and exogenous factors, and is likely based on both a biochemical and immunological process. Withdrawal of the culprit drug is mandatory and can result in remission, although the disease not always subsides, especially in cases caused by non-thiol drugs. Additionally, drugs may also cause a flare or exacerbation of pre-existing pemphigus.</p

    KIC 4150611: a rare multi-eclipsing quintuple with a hybrid pulsator

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    We present the results of our analysis of KIC 4150611 (HD 181469) - an interesting, bright quintuple system that includes a hybrid δ\delta Sct/γ\gamma Dor pulsator. Four periods of eclipses - 94.2, 8.65, 1.52 and 1.43 d - have been observed by the Kepler satellite, and three point sources (A, B, and C) are seen in high angular resolution images. From spectroscopic observations made with the HIDES spectrograph attached to the 1.88-m telescope of the Okayama Astrophysical Observatory (OAO), for the first time we calculated radial velocities (RVs) of the component B - a pair of G-type stars - and combined them with Kepler photometry in order to obtain absolute physical parameters of this pair. We also managed to directly measure RVs of the pulsator, also for the first time. Additionally, we modelled the light curves of the 1.52 and 1.43-day pairs, and measured their eclipse timing variations (ETVs). We also performed relative astrometry and photometry of three sources seen on the images taken with the NIRC2 camera of the Keck II telescope. Finally, we compared our results with theoretical isochrones. The brightest component Aa is the hybrid pulsator, transited every 94.2 days by a pair of K/M-type stars (Ab1+Ab2), which themselves form a 1.52-day eclipsing binary. The components Ba and Bb are late G-type stars, forming another eclipsing pair with a 8.65 day period. Their masses and radii are MBa=0.894±0.010M_{Ba}=0.894\pm0.010 M_\odot, RBa=0.802±0.044R_{Ba}=0.802\pm0.044 R_\odot for the primary, and MBb=0.888±0.010M_{Bb}=0.888\pm0.010 M_\odot, RBb=0.856±0.038R_{Bb}=0.856\pm0.038 R_\odot for the secondary. The remaining period of 1.43 days is possibly related to a faint third star C, which itself is most likely a background object. The system's properties are well-represented by a 35 Myr isochrone. There are also hints of additional bodies in the system.Comment: 14 pages, 15 figures, 7 tables, to appear in A&A, abstract modified in order to fit the arXiv limi
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