WorldWideScience

Sample records for star color-magnitude diagram

  1. MEASURING GALAXY STAR FORMATION RATES FROM INTEGRATED PHOTOMETRY: INSIGHTS FROM COLOR-MAGNITUDE DIAGRAMS OF RESOLVED STARS

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Benjamin D. [Institute d' Astrophysique de Paris, CNRS, UPMC, 98bis Bd Arago, F-75014 Paris (France); Weisz, Daniel R.; Dalcanton, Julianne J.; Johnson, L. C.; Williams, Benjamin F. [Department of Astronomy, Box 351580, University of Washington, Seattle, WA 98195 (United States); Dale, Daniel A. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Dolphin, Andrew E. [Raytheon, 1151 E. Hermans Road, Tucson, AZ 85756 (United States); Gil de Paz, Armando [CEI Campus Moncloa, UCM-UPM, Departamento de Astrofisica y CC. de la Atmosfera, Facultad de CC. Fisicas, Universidad Complutense de Madrid, Avda. Complutense s/n, E-28040 Madrid (Spain); Kennicutt, Robert C. Jr. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Lee, Janice C. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Skillman, Evan D. [Department of Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States); Boquien, Mederic [Marseille Universite, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France)

    2013-07-20

    We use empirical star formation histories (SFHs), measured from Hubble-Space-Telescope-based resolved star color-magnitude diagrams, as input into population synthesis codes to model the broadband spectral energy distributions (SEDs) of 50 nearby dwarf galaxies (6.5 < log M{sub *}/M{sub Sun} < 8.5, with metallicities {approx}10% solar). In the presence of realistic SFHs, we compare the modeled and observed SEDs from the ultraviolet (UV) through near-infrared and assess the reliability of widely used UV-based star formation rate (SFR) indicators. In the FUV through i bands, we find that the observed and modeled SEDs are in excellent agreement. In the Spitzer 3.6 {mu}m and 4.5 {mu}m bands, we find that modeled SEDs systematically overpredict observed luminosities by up to {approx}0.2 dex, depending on treatment of the TP-AGB stars in the synthesis models. We assess the reliability of UV luminosity as a SFR indicator, in light of independently constrained SFHs. We find that fluctuations in the SFHs alone can cause factor of {approx}2 variations in the UV luminosities relative to the assumption of a constant SFH over the past 100 Myr. These variations are not strongly correlated with UV-optical colors, implying that correcting UV-based SFRs for the effects of realistic SFHs is difficult using only the broadband SED. Additionally, for this diverse sample of galaxies, we find that stars older than 100 Myr can contribute from <5%-100% of the present day UV luminosity, highlighting the challenges in defining a characteristic star formation timescale associated with UV emission. We do find a relationship between UV emission timescale and broadband UV-optical color, though it is different than predictions based on exponentially declining SFH models. Our findings have significant implications for the comparison of UV-based SFRs across low-metallicity populations with diverse SFHs.

  2. The initial mass function for massive stars in the Magellanic Clouds. 1: UBV photometry and color-magnitude diagrams for 14 OB associations

    Science.gov (United States)

    Hill, Robert J.; Madore, Barry F.; Freedman, Wendy L.

    1994-01-01

    UBV charge coupled device (CCD) photometry has been obtained for 14 OB associations in the Magellanic Clouds using the University of Toronto's 0.6 m telescope and the Carnegie Institution of Washington's 1.0 m reflector, both on Las Campanas, Chile. The data are presented and used to construct color-magnitude diagrams for the purposes of investigating the massive-star content of the associations.

  3. Powerful CMD: a tool for color-magnitude diagram studies

    Science.gov (United States)

    Li, Zhong-Mu; Mao, Cai-Yan; Luo, Qi-Ping; Fan, Zhou; Zhao, Wen-Chang; Chen, Li; Li, Ru-Xi; Guo, Jian-Po

    2017-07-01

    We present a new tool for color-magnitude diagram (CMD) studies, Powerful CMD. This tool is built based on the advanced stellar population synthesis (ASPS) model, in which single stars, binary stars, rotating stars and star formation history have been taken into account. Via Powerful CMD, the distance modulus, color excess, metallicity, age, binary fraction, rotating star fraction and star formation history of star clusters can be determined simultaneously from observed CMDs. The new tool is tested via both simulated and real star clusters. Five parameters of clusters NGC 6362, NGC 6652, NGC 6838 and M67 are determined and compared to other works. It is shown that this tool is useful for CMD studies, in particular for those utilizing data from the Hubble Space Telescope (HST). Moreover, we find that inclusion of binaries in theoretical stellar population models may lead to smaller color excess compared to the case of single-star population models.

  4. The interpretation of color-magnitude diagrams through numerical simulation and Bayesian inference

    NARCIS (Netherlands)

    Tolstoy, E; Saha, A

    1996-01-01

    We present a new method designed to aid in the interpretation of the color-magnitude diagrams (CMDs) of resolved stars in nearby galaxies. A CMD is a two-dimensional distribution of data points with well understood Gaussian measurement errors created from two independent observations. The most

  5. Hierarchical Probabilistic Inference of the Color-Magnitude Diagram and Shrinkage of Stellar Distance Uncertainties

    Science.gov (United States)

    Leistedt, Boris; Hogg, David W.

    2017-12-01

    We present a hierarchical probabilistic model for improving geometric stellar distance estimates using color-magnitude information. This is achieved with a data-driven model of the color-magnitude diagram, not relying on stellar models but instead on the relative abundances of stars in color-magnitude cells, which are inferred from very noisy magnitudes and parallaxes. While the resulting noise-deconvolved color-magnitude diagram can be useful for a range of applications, we focus on deriving improved stellar distance estimates relying on both parallax and photometric information. We demonstrate the efficiency of this approach on the 1.4 million stars of the Gaia TGAS sample that also have AAVSO Photometric All Sky Survey magnitudes. Our hierarchical model has 4 million parameters in total, most of which are marginalized out numerically or analytically. We find that distance estimates are significantly improved for the noisiest parallaxes and densest regions of the color-magnitude diagram. In particular, the average distance signal-to-noise ratio (S/N) and uncertainty improve by 19% and 36%, respectively, with 8% of the objects improving in S/N by a factor greater than 2. This computationally efficient approach fully accounts for both parallax and photometric noise and is a first step toward a full hierarchical probabilistic model of the Gaia data.

  6. Some constraints on the color-magnitude diagram of giants in the galactic spheroid

    Science.gov (United States)

    Bahcall, J. N.; Soneira, R. M.; Morton, D. C.; Tritton, K. P.

    1983-01-01

    The color-magnitude diagram of giants in the Galactic spheroid is shown to be important in determining the number-color histogram of stars brighter than B = 19 mag. This result is demonstrated by comparing a standard Galaxy model with observations of 391 stars in a field in the direction of Aquarius (l = 36.5 deg, b = -51.1 deg). More than 80 percent of the spheroid stars and 40 percent of all stars in this magnitude range and direction are predicted to be giants. At most, a few percent of the spheroid stars in the current sample can lie on the main sequence bluer than the turn-off onto the giant branch near B - V approximately 0.4. The available observations suggest that the blue tip of the horizontal branch of the spheroid must be sparsely populated about a factor of 10 less than would be expected if the color-magnitude diagram of the spheroid were the same as diagrams for any of the globular clusters M3, M13, or M92. The total dispersion in colors (measurement errors and intrinsic dispersion) has a standard deviation in B - V color that is less than 0.2 mag.

  7. Beyond Blue Stragglers: Products of Non-Standard Stellar Evolution Across the Color Magnitude Diagram

    Science.gov (United States)

    Leiner, Emily

    2018-01-01

    Optical color-magnitude diagrams (CMDs) of open clusters reveal large populations of stars that do not fall along standard isochrones, and thus are not evolving according to standard theory. The most numerous of these stars are the blue stragglers, stars brighter and bluer than the cluster turnoff that are likely formed from mass transfer in a binary, stellar mergers, or collisions during dynamical encounters. The origins of other non-standard stars are not well understood, including the “yellow stragglers” found between the blue straggler region and the red giant branch, and “sub-subgiants” found fainter and redder than the giant branch. Understanding the formation and evolution of these non-standard stars is critical to properly modeling galactic stellar populations and revealing the binary evolution channels that form exotic end products like X-ray binaries, double degenerates, and Type 1a supernovae. In this talk I will present results of the first asteroseismic study of a yellow straggler in the old open cluster M67. This study shows the yellow straggler to be a red clump giant with a mass of at least twice the turnoff mass of M67, suggesting it is an evolved blue straggler formed from a merger or collision. I will also discuss the observed properties of the growing population of sub-subgiants discovered in open and globular clusters, and present models describing three possible formation pathways for these stars: mass-transfer in a binary, rapid envelope mass loss, and inhibition of convection due to the presence of strong magnetic fields. These studies represent some of the first efforts to understand cluster CMD outliers beyond the blue stragglers, and are a critical step forward in understanding binary evolution pathways.

  8. The Populations of Carina. I. Decoding the Color-Magnitude Diagram

    Science.gov (United States)

    Norris, John E.; Yong, David; Venn, Kim A.; Dotter, Aaron; Casagrande, Luca; Gilmore, Gerard

    2017-06-01

    We investigate the color-magnitude diagram (CMD) of the Carina dwarf spheroidal galaxy using data of Stetson et al. and synthetic CMDs based on isochrones of Dotter et al., in terms of the parameters [Fe/H], age, and [α/Fe], for the cases when (I) [α/Fe] is held constant and (II) [α/Fe] is varied. The data are well described by four basic epochs of star formation, having [Fe/H] = -1.85, -1.5, -1.2, and ˜-1.15 and ages ˜13, 7, ˜3.5, and ˜1.5 Gyr, respectively (for [α/Fe] = 0.1, constant [α/Fe], and [α/Fe] = 0.2, 0.1, -0.2, -0.2, variable [α/Fe]), with small spreads in [Fe/H] and age of order 0.1 dex and 1-3 Gyr. Within an elliptical radius 13.‧1, the mass fractions of the populations, at their times of formation, were (in decreasing age order) 0.34, 0.39, 0.23, and 0.04. This formalism reproduces five observed CMD features (two distinct subgiant branches of old and intermediate-age populations, two younger, main-sequence components, and the small color dispersion on the red giant branch (RGB). The parameters of the youngest population are less certain than those of the others, and given it is less centrally concentrated, it may not be directly related to them. High-resolution spectroscopically analyzed RGB samples appear statistically incomplete compared with those selected using radial velocity, which contain bluer stars comprising ˜5%-10% of the samples. We conjecture these objects may, at least in part, be members of the youngest population. We use the CMD simulations to obtain insight into the population structure of Carina's upper RGB.

  9. The Deepest Hubble Space Telescope Color-Magnitude Diagram of M32 : Evidence for Intermediate-age Populations

    NARCIS (Netherlands)

    Monachesi, Antonela; Trager, Scott C.; Lauer, Tod R.; Freedman, Wendy; Dressler, Alan; Grillmair, Carl; Mighell, Kenneth J.

    2011-01-01

    We present the deepest optical color-magnitude diagram (CMD) to date of the local elliptical galaxy M32. We have obtained F435W and F555W photometries based on Hubble Space Telescope (HST) Advanced Camera for Surveys/High-Resolution Channel images for a region 110 '' from the center of M32 (F1) and

  10. FROM THE COLOR-MAGNITUDE DIAGRAM OF {omega} CENTAURI AND (SUPER-)ASYMPTOTIC GIANT BRANCH STELLAR MODELS TO A GALACTIC PLANE PASSAGE GAS PURGING CHEMICAL EVOLUTION SCENARIO

    Energy Technology Data Exchange (ETDEWEB)

    Herwig, Falk; VandenBerg, Don A.; Navarro, Julio F. [Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, Victoria, BC V8W 3P6 (Canada); Ferguson, Jason [Department of Physics, Wichita State University Wichita, KS 67260 (United States); Paxton, Bill, E-mail: fherwig@uvic.ca, E-mail: vandenbe@uvic.ca, E-mail: jason.ferguson@wichita.edu, E-mail: paxton@kitp.ucsb.edu [KITP/UC Santa Barbara, Santa Barbara, CA 93106 (United States)

    2012-10-01

    We have investigated the color-magnitude diagram of {omega} Centauri and find that the blue main sequence (bMS) can be reproduced only by models that have a helium abundance in the range Y = 0.35-0.40. To explain the faint subgiant branch of the reddest stars ('MS-a/RG-a' sequence), isochrones for the observed metallicity ([Fe/H] Almost-Equal-To -0.7) appear to require both a high age ({approx}13 Gyr) and enhanced CNO abundances ([CNO/Fe] Almost-Equal-To 0.9). Y Almost-Equal-To 0.35 must also be assumed in order to counteract the effects of high CNO on turnoff colors and thereby to obtain a good fit to the relatively blue turnoff of this stellar population. This suggests a short chemical evolution period of time (<1 Gyr) for {omega} Cen. Our intermediate-mass (super-)asymptotic giant branch (AGB) models are able to reproduce the high helium abundances, along with [N/Fe] {approx}2 and substantial O depletions if uncertainties in the treatment of convection are fully taken into account. These abundance features distinguish the bMS stars from the dominant [Fe/H] Almost-Equal-To -1.7 population. The most massive super-AGB stellar models (M{sub ZAMS} {>=} 6.8 M{sub Sun }, M{sub He,core} {>=} 1.245 M{sub Sun }) predict too large N enhancements, which limit their role in contributing to the extreme populations. In order to address the observed central concentration of stars with He-rich abundance, we show here quantitatively that highly He- and N-enriched AGB ejecta have particularly efficient cooling properties. Based on these results and on the reconstruction of the orbit of {omega} Cen with respect to the Milky Way, we propose the Galactic plane passage gas purging scenario for the chemical evolution of this cluster. The bMS population formed shortly after the purging of most of the cluster gas as a result of the passage of {omega} Cen through the Galactic disk (which occurs today every {approx}40 Myr for {omega} Cen) when the initial mass function of the

  11. Pixel Color-Magnitude Diagram Analysis of the Brightest Cluster Galaxies in Dynamically Young and Old Clusters Abell 1139 and Abell 2589

    Science.gov (United States)

    Lee, Joon Hyeop; Oh, Sree; Jeong, Hyunjin; Yi, Sukyoung K.; Kyeong, Jaemann; Park, Byeong-Gon

    2017-07-01

    As a case study to understand the coevolution of Brightest Cluster Galaxies (BCGs) and their host clusters, we investigate the BCGs in dynamically young and old clusters Abell 1139 (A1139) and Abell 2589 (A2589). We analyze the pixel color-magnitude diagrams (pCMDs) using deep g- and r-band images, obtained from the Canada-France-Hawaii Telescope observations. After masking foreground/background objects and smoothing pixels in consideration of the observational seeing size, detailed pCMD features are compared between the two BCGs. (1) Although the overall shapes of the pCMDs are similar to those of typical early-type galaxies, the A2589-BCG tends to have redder mean pixel color and smaller pixel color deviation at given surface brightness than the A1139-BCG. (2) The mean pixel color distribution as a function of pixel surface brightness (pCMD backbone) indicates that the A2589-BCG formed a larger central body (˜2.0 kpc in radius) via major dry mergers at an early epoch than the A1139-BCG (a central body ˜1.3 kpc in radius), whereas they have grown commonly in subsequent minor mergers. (3) The spatial distributions of the pCMD outliers reveal that the A1139-BCG experienced considerable tidal events more recently than the A2589-BCG, whereas the A2589-BCG has an asymmetric compact core, possibly resulting from a major dry merger at an early epoch. (4) The A2589-BCG shows a very large faint-to-bright pixel number ratio, compared to early-type non-BCGs, whereas the ratio for the A1139-BCG is not distinctively large. These results are consistent with the idea that the BCG in the dynamically older cluster (A2589) formed earlier and is better relaxed.

  12. Color/magnitude calibration for National Aeronautics and Space Administration (NASA) standard Fixed-Head Star Trackers (FHST)

    Science.gov (United States)

    Landis, J.; Leid, Terry; Garber, A.; Lee, M.

    1994-01-01

    This paper characterizes and analyzes the spectral response of Ball Aerospace fixed-head star trackers, (FHST's) currently in use on some three-axis stabilized spacecraft. The FHST output is a function of the frequency and intensity of the incident light and the position of the star image in the field of view. The FHST's on board the Extreme Ultraviolet Explorer (EUVE) have had occasional problems identifying stars with a high B-V value. These problems are characterized by inaccurate intensity counts observed by the tracker. The inaccuracies are due to errors in the observed star magnitude values. These errors are unique to each individual FHST. For this reason, data were also collected and analyzed from the Upper Atmosphere Research Satellite (UARS). As a consequence of this work, the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) hopes to improve the attitude accuracy on these missions and to adopt better star selection procedures for catalogs.

  13. Maxima and O-C Diagrams for 489 Mira Stars

    Science.gov (United States)

    Karlsson, T.

    2013-11-01

    Maxima for 489 Mira stars have been compiled. They were computed with data from AAVSO, AFOEV, VSOLJ, and BAA-VSS and collected from published maxima. The result is presented in a mysql database and on web pages with O-C diagrams, periods and some statistical information for each star.

  14. Multiple Stars Across the H-R Diagram

    CERN Document Server

    Hubrig, Swetlana; Tokovinin, Andrei; Proceedings of the ESO Workshop held in Garching, Germany, 12-15 July 2005

    2008-01-01

    Stars show a marked tendency to be in systems of different multiplicity, ranging from simple binaries and triples to globular clusters with several 10,000's of stars. The formation and evolution of multiple systems remains a challenging part of astrophysics, and the contributions in this book report on the significant progress that had been made in this research field in the last years. The reader will find a variety of research topics addressed, such as the dynamical evolution in multiple stars, the effects of the environment on multiple system parameters, stellar evolution within multiple stars, multiplicity of massive stars, pre-main sequence and intermediate mass stars, multiplicity of low-mass stars from embedded protostars to open clusters, and brown dwarfs and extrasolar planets in multiples. This book presents the proceedings of the ESO Workshop on Multiple Stars across the H-R Diagram held in the summer of 2005.

  15. Hertzsprung-Russell diagram and mass distribution of barium stars

    Science.gov (United States)

    Escorza, A.; Boffin, H. M. J.; Jorissen, A.; Van Eck, S.; Siess, L.; Van Winckel, H.; Karinkuzhi, D.; Shetye, S.; Pourbaix, D.

    2017-12-01

    With the availability of parallaxes provided by the Tycho-Gaia Astrometric Solution, it is possible to construct the Hertzsprung-Russell diagram (HRD) of barium and related stars with unprecedented accuracy. A direct result from the derived HRD is that subgiant CH stars occupy the same region as barium dwarfs, contrary to what their designations imply. By comparing the position of barium stars in the HRD with STAREVOL evolutionary tracks, it is possible to evaluate their masses, provided the metallicity is known. We used an average metallicity [Fe/H] = -0.25 and derived the mass distribution of barium giants. The distribution peaks around 2.5 M⊙ with a tail at higher masses up to 4.5 M⊙. This peak is also seen in the mass distribution of a sample of normal K and M giants used for comparison and is associated with stars located in the red clump. When we compare these mass distributions, we see a deficit of low-mass (1 - 2 M⊙) barium giants. This is probably because low-mass stars reach large radii at the tip of the red giant branch, which may have resulted in an early binary interaction. Among barium giants, the high-mass tail is however dominated by stars with barium indices of less than unity, based on a visual inspection of the barium spectral line; that is, these stars have a very moderate barium line strength. We believe that these stars are not genuine barium giants, but rather bright giants, or supergiants, where the barium lines are strengthened because of a positive luminosity effect. Moreover, contrary to previous claims, we do not see differences between the mass distributions of mild and strong barium giants. Full Table A.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/608/A100

  16. Deep Hubble Space Telescope imaging of Sextans A. III. The star formation history

    NARCIS (Netherlands)

    Dolphin, AE; Saha, A; Skillman, ED; Dohm-Palmer, RC; Tolstoy, E; Cole, AA; Gallagher, JS; Hoessel, JG; Mateo, M

    We present a measurement of the star formation history of Sextans A, based on WFPC2 photometry that is 50% complete to V = 27.5 (M-V similar to +1.9) and I = 27.0. The star formation history and chemical enrichment history have been measured through modeling of the color-magnitude diagram (CMD). We

  17. On the co-existence of chemically peculiar Bp stars, slowly pulsating B stars and constant B stars in the same part of the H-R diagram

    NARCIS (Netherlands)

    Briquet, M.; Hubrig, S.; Cat, P. de; Aerts, C.; North, P.; Schöller, M.

    2007-01-01

    Aims. In order to better model massive B-type stars, we need to understand the physical processes taking place in slowly pulsating B (SPB) stars, chemically peculiar Bp stars, and non-pulsating normal B stars co-existing in the same part of the H-R diagram. Methods: We carry out a comparative study

  18. BVR PHOTOMETRY OF SUPERGIANT STARS IN HOLMBERG II

    Directory of Open Access Journals (Sweden)

    Y.-J. Sohn

    2006-03-01

    Full Text Available We report the photometric properties in BVR bands for the resolved bright supergiant stars in the dwarf galaxy Holmberg II. The color-magnitude diagrams and color-color diagram of 374 resolved stars indicate that the majority of the member stars are supergiant stars with a wide range of spectral type between B-K. A comparison with theoretical evolutionary tracks indicates that the supergiant stars in the observed field have progenitor masses between ~10M_⨀ and 20M_⨀. The exponent of luminosity function in V is in good agreement with those of the Small and Large Magellanic Clouds.

  19. The Color-Magnitude Relation for Metal-Poor Globular Clusters in M87: Confirmation From Deep HST/ACS Imaging

    OpenAIRE

    Peng, Eric W.; Jordan, Andres; Blakeslee, John P.; Mieske, Steffen; Cote, Patrick; Ferrarese, Laura; Harris, William E.; Madrid, Juan P.; Meurer, Gerhardt R.

    2009-01-01

    Metal-poor globular clusters (GCs) are our local link to the earliest epochs of star formation and galaxy building. Studies of extragalactic GC systems using deep, high-quality imaging have revealed a small but significant slope to the color-magnitude relation for metal-poor GCs in a number of galaxies. We present a study of the M87 GC system using deep, archival HST/ACS imaging with the F606W and F814W filters, in which we find a significant color-magnitude relation for the metal-poor GCs. T...

  20. Detection of the Red Giant Branch Stars in the M82 Using the Hubble Space Telescope

    Science.gov (United States)

    Madore, B.; Sakai, S.

    1999-01-01

    We present color-magnitude diagrams and luminosity functions or stars in two halo regions of the irregular galaxy in M82, based on F555W and F814W photometry taken with the Hubble Space Telescope and Wide Field Planetary Camera 2.

  1. ABOUT THE LINEARITY OF THE COLOR-MAGNITUDE RELATION OF EARLY-TYPE GALAXIES IN THE VIRGO CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Smith Castelli, Analia V.; Faifer, Favio R. [Instituto de Astrofisica de La Plata (CCT-La Plata, CONICET-UNLP), Paseo del Bosque s/n, B1900FWA, La Plata (Argentina); Gonzalez, Nelida M. [Facultad de Ciencias Astronomicas y Geofisicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, La Plata, B1900FWA (Argentina); Forte, Juan Carlos, E-mail: asmith@fcaglp.unlp.edu.ar, E-mail: ngonzalez@fcaglp.unlp.edu.ar, E-mail: favio@fcaglp.unlp.edu.ar, E-mail: forte@fcaglp.unlp.edu.ar [CONICET-Planetario de la Ciudad de Buenos Aires ' ' Galileo Galilei' ' , Av. Sarmiento y B. Roldan, Ciudad Autonoma de Buenos Aires (Argentina)

    2013-07-20

    We revisit the color-magnitude relation of Virgo Cluster early-type galaxies in order to explore its alleged nonlinearity. To this aim, we reanalyze the relation already published from data obtained within the ACS Virgo Cluster Survey of the Hubble Space Telescope and perform our own photometry and analysis of the images of 100 early-type galaxies observed as part of this survey. In addition, we compare our results with those reported in the literature from data of the Sloan Digital Sky Survey. We have found that when the brightest galaxies and untypical systems are excluded from the sample, a linear relation arises in agreement with what is observed in other groups and clusters. The central regions of the brightest galaxies also follow this relation. In addition, we notice that Virgo contains at least four compact elliptical galaxies besides the well-known object VCC 1297 (NGC 4486B). Their locations in the ({mu}{sub eff})-luminosity diagram define a trend different from that followed by normal early-type dwarf galaxies, setting an upper limit in effective surface brightness and a lower limit in the effective radius for their luminosities. Based on the distribution of different galaxy sub-samples in the color-magnitude and ({mu}{sub eff})-luminosity diagrams, we draw some conclusions on their formation and the history of their evolution.

  2. HST-ACS photometry of the isolated dwarf galaxy VV124=UGC 4879 : Detection of the blue horizontal branch and identification of two young star clusters

    NARCIS (Netherlands)

    Bellazzini, M.; Perina, S.; Galleti, S.; Oosterloo, T.

    We present deep V and I photometry of the isolated dwarf galaxy VV124=UGC 4879, obtained from archival images taken with the Hubble Space Telescope - Advanced Camera for Surveys. In the color-magnitude diagrams of stars at distances greater than 40″ from the center of the galaxy, we clearly identify

  3. Dissecting the Spitzer colour-magnitude diagrams of extreme Large Magellanic Cloud asymptotic giant branch stars

    Science.gov (United States)

    Dell'Agli, F.; Ventura, P.; García Hernández, D. A.; Schneider, R.; Di Criscienzo, M.; Brocato, E.; D'Antona, F.; Rossi, C.

    2014-07-01

    We trace the full evolution of low- and intermediate-mass stars (1 ≤ M ≤ 8 M⊙) during the asymptotic giant branch (AGB) phase in the Spitzer two-colour and colour-magnitude diagrams. We follow the formation and growth of dust particles in the circumstellar envelope with an isotropically expanding wind, in which gas molecules impinge upon pre-existing seed nuclei, favour their growth. These models are the first able to identify the main regions in the Spitzer data occupied by AGB stars in the Large Magellanic Cloud (LMC). The main diagonal sequence traced by LMC extreme stars in the [3.6] - [4.5] versus [5.8] - [8.0] and [3.6] - [8.0] versus [8.0] planes is nicely fit by carbon stars models; it results to be an evolutionary sequence with the reddest objects being at the final stages of their AGB evolution. The most extreme stars, with [3.6] - [4.5] > 1.5 and [3.6] - [8.0] > 3, are 2.5-3 M⊙ stars surrounded by solid carbon grains. In higher mass (>3 M⊙) models dust formation is driven by the extent of hot bottom burning (HBB) - most of the dust formed is in the form of silicates and the maximum obscuration phase by dust particles occurs when the HBB experienced is strongest, before the mass of the envelope is considerably reduced.

  4. Luminous and Variable Stars in M31 and M33. V. The Upper HR Diagram

    Energy Technology Data Exchange (ETDEWEB)

    Humphreys, Roberta M.; Davidson, Kris; Hahn, David [Minnesota Institute for Astrophysics, 116 Church St SE, University of Minnesota, Minneapolis, MN 55455 (United States); Martin, John C. [Barber Observatory, University of Illinois, Springfield, IL 62703 (United States); Weis, Kerstin, E-mail: roberta@umn.edu [Astronomical Institute, Ruhr-Universitaet Bochum (Germany)

    2017-07-20

    We present HR diagrams for the massive star populations in M31 and M33, including several different types of emission-line stars: the confirmed luminous blue variables (LBVs), candidate LBVs, B[e] supergiants, and the warm hypergiants. We estimate their apparent temperatures and luminosities for comparison with their respective massive star populations and evaluate the possible relationships of these different classes of evolved, massive stars, and their evolutionary state. Several of the LBV candidates lie near the LBV/S Dor instability strip that supports their classification. Most of the B[e] supergiants, however, are less luminous than the LBVs. Many are very dusty with the infrared flux contributing one-third or more to their total flux. They are also relatively isolated from other luminous OB stars. Overall, their spatial distribution suggests a more evolved state. Some may be post-RSGs (red supergiants) like the warm hypergiants, and there may be more than one path to becoming a B[e] star. There are sufficient differences in the spectra, luminosities, spatial distribution, and the presence or lack of dust between the LBVs and B[e] supergiants to conclude that one group does not evolve into the other.

  5. VizieR Online Data Catalog: MC massive stars IMF. I. (Hill+, 1994)

    Science.gov (United States)

    Hill, R. J.; Madore, B. F.; Freedman, W. L.

    1994-11-01

    UBV CCD photometry has been obtained for 14 OB associations in the Magellanic Clouds using the University of Toronto's 0.6m telescope and the Carnegie Institution of Washington's 1.0m reflector, both on Las Campanas, Chile. The data are presented and used to construct color-magnitude diagrams for the purposes of investigating the massive-star content of the associations. (1 data file).

  6. A Centrality and Event Plane Detector for STAR to Complete the Phase Diagram of Quantum Chromodynamics

    Science.gov (United States)

    Halal, George; STAR Collaboration

    2017-09-01

    The properties of the nearly perfect liquid, Quark Gluon Plasma (QGP), which filled the universe a microsecond after the Big Bang are studied by colliding heavy-ions at relativistic energies. Our project focuses on building and testing an Event Plane Detector (EPD) for the STAR experiment and analyzing the data collected from collisions. When a minimum ionizing particle hits one of the optically-isolated tiles of this detector, which are made of scintillator plastic, it lights up. The light then travels through a wavelength-shifting fiber embedded in the tile to a clear optical fiber to be detected by silicon photo-multipliers. This detector is an improved version of the Beam-Beam Counter, which is currently at STAR. It will help us measure the centrality and event plane of collisions with more precision. Data collected will aid us in mapping out the transition phase between the QGP and hadronic matter, which evolved into the chemical elements we see today, and in searching for a unique critical point in the phase diagram of Quantum Chromodynamics matter. In 2017, a commissioning run has taken place at RHIC, colliding protons at 510 GeV and gold ions at 54.4 GeV. Some data analysis from one eighth of the EPD that is installed will also be discussed.

  7. Weak G-band stars on the H-R diagram: clues to the origin of the Li anomaly

    Science.gov (United States)

    Palacios, A.; Parthasarathy, M.; Bharat Kumar, Y.; Jasniewicz, G.

    2012-02-01

    Aims: Weak G-band (WGB) stars are a rare class of cool luminous stars that present a strong depletion in carbon, but also lithium abundance anomalies that have been little explored in the literature since the first discovery of these peculiar objects in the early 1950s. Here we focus on the Li-rich WGB stars and report on their evolutionary status. We explored different paths to propose a tentative explanation for the lithium anomaly. Methods: Using archive data, we derived the fundamental parameters of WGB (Teff, log g, log (L/L⊙)) using Hipparcos parallaxes and recent temperature scales. From the equivalent widths of Li resonance line at 6707 Å, we uniformly derived the lithium abundances and applied NLTE corrections when possible following the procedure described by Lind et al. (2009). We also computed dedicated stellar evolution models in the mass range 3.0 to 4.5 M⊙, exploring the effects of rotation-induced and thermohaline mixing. These models are used to locate the WGB stars in the H-R diagram and to explore the origin of the abundance anomalies. Results: The location of WGB stars in the Hertzsprung-Russell diagram shows that these are intermediate mass stars of masses ranging from 3.0 to 4.5 M⊙ located at the clump, which implies a degeneracy of their evolutionary status between subgiant/red giant branch and core helium burning phases. The atmospheres of a large proportion of WGB stars (more than 50%) exhibit lithium abundances A(Li) ≥ 1.4 dex similar to Li-rich K giants. However, the position of WGB stars along with the Li-rich K giants in the H-R diagram, indicates that both are well-separated groups. The combined and tentatively consistent analysis of the abundance pattern for lithium, carbon, and nitrogen of WGB stars seems to indicate that carbon underabundance could be decorrelated from the lithium and nitrogen overabundances.

  8. On the Variability of Blue Straggler Stars in the Globular Cluster M53

    Directory of Open Access Journals (Sweden)

    Soo-Chang Rey

    1998-06-01

    Full Text Available We present the results of a search for photometric variable blue straggler stars (BSSs in the globular cluster M53. Six of the 151 probable BSSs are identified as variable candidates based on the robust variable star detection technique of Welch & Stetson (1993. Most variable BSS candidates appear to occupy the instability strip in the color-magnitude diagram, and they appear to have visual light amplitudes of 0.2 mag - 0.3 mag. Further observations are required, however, to resolve the nature of variability between pulsating stars and eclipsing binaries for these variable BSS candidates.

  9. Color-magnitude distribution of face-on nearby galaxies in Sloan digital sky survey DR7

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Shuo-Wen; Feng, Long-Long [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Gu, Qiusheng; Huang, Song; Shi, Yong, E-mail: qsgu@nju.edu.cn [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)

    2014-05-20

    We have analyzed the distributions in the color-magnitude diagram (CMD) of a large sample of face-on galaxies to minimize the effect of dust extinctions on galaxy color. About 300,000 galaxies with log (a/b) < 0.2 and redshift z < 0.2 are selected from the Sloan Digital Sky Survey DR7 catalog. Two methods are employed to investigate the distributions of galaxies in the CMD, including one-dimensional (1D) Gaussian fitting to the distributions in individual magnitude bins and two-dimensional (2D) Gaussian mixture model (GMM) fitting to galaxies as a whole. We find that in the 1D fitting, two Gaussians are not enough to fit galaxies with the excess present between the blue cloud and the red sequence. The fitting to this excess defines the center of the green valley in the local universe to be (u – r){sub 0.1} = –0.121M {sub r,} 0{sub .1} – 0.061. The fraction of blue cloud and red sequence galaxies turns over around M {sub r,} {sub 0.1} ∼ –20.1 mag, corresponding to stellar mass of 3 × 10{sup 10} M {sub ☉}. For the 2D GMM fitting, a total of four Gaussians are required, one for the blue cloud, one for the red sequence, and the additional two for the green valley. The fact that two Gaussians are needed to describe the distributions of galaxies in the green valley is consistent with some models that argue for two different evolutionary paths from the blue cloud to the red sequence.

  10. Semi-analytical formulas for the Hertzsprung-Russell diagram

    Directory of Open Access Journals (Sweden)

    Zaninetti L.

    2008-01-01

    Full Text Available The absolute visual magnitude as function of the observed color (B-V, also named Hertzsprung-Russell diagram, can be described through five equations; that when calibrated stars are available means eight constants. The developed framework allows to deduce the remaining physical parameters, mass, radius and luminosity. This new technique is applied to the first 10 pc, the first 50 pc, the Hyades and to the determination of the distance of a cluster. The case of the white dwarfs is analyzed assuming the absence of calibrated data: our equation produces a smaller χ2 with respect to the standard color-magnitude calibration when applied to the Villanova Catalog of Spectroscopically Identified White Dwarfs. The theoretical basis of the formulas for the colors and the bolometric correction of the stars is clarified by a Taylor expansion in the temperature of the Planck distribution.

  11. Study of the QCD Phase Diagram using STAR at RHIC - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Westfall, Gary [Michigan State Univ., East Lansing, MI (United States)

    2017-01-20

    This grant supported the MSU STAR Group from April 1, 1998 to October 31, 2016. Originally the MSU STAR Group consisted of the principal investigator (PI), a staff physicist, and one graduate student. Funds were provided for half the summer salary of the PI, the full salary of the staff physicist, and half the costs associated with one graduate student. The other half of the PI’s summer salary and graduate student costs was covered by NSCL. In addition, this grant provided funds for travel and workstations related to STAR. Starting in 2009, the MSU STAR Group replaced the staff physicist with a postdoctoral scientist.

  12. A catalog of 120 NGC open star clusters

    OpenAIRE

    Tadross, A. L.

    2011-01-01

    A sample of 145 JHK--2MASS observations of NGC open star clusters is studied, of which 132 have never been studied before. Twelve are classified as non-open clusters and 13 are re-estimated self-consistently, after applying the same methods in order to compare and calibrate our reduction procedures. The fundamental and structural parameters of the 120 new open clusters studied here are derived using color-magnitude diagrams of JHK Near-IR photometry with the fitting of solar metallicity isoch...

  13. A SECOND NEUTRON STAR IN M4?

    Energy Technology Data Exchange (ETDEWEB)

    Kaluzny, J.; Rozanska, A.; Rozyczka, M.; Krzeminski, W. [Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw (Poland); Thompson, Ian B. [Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2012-05-01

    We show that the optical counterpart of the X-ray source CX 1 in M4 is a {approx}20th magnitude star, located in the color-magnitude diagram on (or very close to) the main sequence of the cluster, and exhibiting sinusoidal variations of the flux. We find the X-ray flux to be also periodically variable, with X-ray and optical minima coinciding. Stability of the optical light curve, lack of UV-excess, and unrealistic mean density resulting from period-density relation for semidetached systems speak against the original identification of CX 1 as a cataclysmic variable. We argue that the X-ray active component of this system is a neutron star (probably a millisecond pulsar).

  14. The Type Ia Supernova Color-Magnitude Relation and Host Galaxy Dust: A Simple Hierarchical Bayesian Model

    Science.gov (United States)

    Mandel, Kaisey S.; Scolnic, Daniel M.; Shariff, Hikmatali; Foley, Ryan J.; Kirshner, Robert P.

    2017-06-01

    Conventional Type Ia supernova (SN Ia) cosmology analyses currently use a simplistic linear regression of magnitude versus color and light curve shape, which does not model intrinsic SN Ia variations and host galaxy dust as physically distinct effects, resulting in low color-magnitude slopes. We construct a probabilistic generative model for the dusty distribution of extinguished absolute magnitudes and apparent colors as the convolution of an intrinsic SN Ia color-magnitude distribution and a host galaxy dust reddening-extinction distribution. If the intrinsic color-magnitude (M B versus B - V) slope {β }{int} differs from the host galaxy dust law R B , this convolution results in a specific curve of mean extinguished absolute magnitude versus apparent color. The derivative of this curve smoothly transitions from {β }{int} in the blue tail to R B in the red tail of the apparent color distribution. The conventional linear fit approximates this effective curve near the average apparent color, resulting in an apparent slope {β }{app} between {β }{int} and R B . We incorporate these effects into a hierarchical Bayesian statistical model for SN Ia light curve measurements, and analyze a data set of SALT2 optical light curve fits of 248 nearby SNe Ia at z< 0.10. The conventional linear fit gives {β }{app}≈ 3. Our model finds {β }{int}=2.3+/- 0.3 and a distinct dust law of {R}B=3.8+/- 0.3, consistent with the average for Milky Way dust, while correcting a systematic distance bias of ˜0.10 mag in the tails of the apparent color distribution. Finally, we extend our model to examine the SN Ia luminosity-host mass dependence in terms of intrinsic and dust components.

  15. The Dearth of UV-bright Stars in M32: Implications for Stellar Evolution Theory

    Science.gov (United States)

    Sweigart, Allen V.; Kimble, Randy A.; Bowers, Charles W.

    2008-01-01

    Using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, we have obtained deep far ultraviolet images of the compact elliptical galaxy M32. When combined with earlier near-ultraviolet images of the same field, these data enable the construction of an ultraviolet color-magnitude diagram of the hot horizontal branch (HB) population and other hot stars in late phases of stellar evolution. We find few post-asymptotic giant branch (PAGB) stars in the galaxy, implying that these stars either cross the HR diagram more rapidly than expected, and/or that they spend a significant fraction of their time enshrouded in circumstellar material. The predicted luminosity gap between the hot HB and its AGB-Manque (AGBM) progeny is less pronounced than expected, especially when compared to evolutionary tracks with enhanced helium abundances, implying that the presence of hot HB stars in this metal-rich population is not due to (Delta)Y/(Delta)Z greater than or approx. 4. Only a small fraction (approx. 2%) of the HB population is hot enough to produce significant UV emission, yet most of the W emission in this galaxy comes from the hot HB and AGBM stars, implying that PAGB stars are not a significant source of W emission even in those elliptical galaxies with a weak W excess. Subject headings: galaxies: evolution - galaxies: stellar content - galaxies: individual (M32) - stars: evolution - stars: horizontal branch

  16. Searching for Young Stars in Cepheus C

    Science.gov (United States)

    Evans, Sam; Rebull, Luisa; Rutherford, Thomas; Stalnaker, Olivia; Taylor, John; Efsits, Gabriel; Harl, Linda; Keil, Shayna; Learman, Duncan; Leonard, Liam; Russell, Aaron

    2018-01-01

    We used archival Herschel Space Observatory data to search for young stellar objects (YSOs) in the Cepheus C region of the molecular cloud Cepheus OB3. Previous work by Gutermuth et al. (2009) identified 114 YSO candidates in this region based on Spitzer/IRAC data. Work by Orr et al. (2016) refined a list of approximately 300 young star candidates to 245 likely YSOs. Our initial search focused on longer infrared wavelength data – Herschel (70, 160, 250, 350, 500 μm) archival data and SCUBA (450, 850 μm) data from the literature (DiFrancesco et al. 2008). Through image inspection and catalog matching, we assembled a list of 54 candidate YSOs detected at wavelengths longer than 22 μm. For each source, we constructed a spectral energy distribution (SED) by aggregating available shorter wavelength data from the literature and assembling photometry from released PACS catalogs, preliminary SPIRE catalogs, and our own photometric measurements. We also created color-color and color-magnitude diagrams to see how these sources compared to each other, other populations of YSOs, and objects in extragalactic regions. Each source was then classified based on its SED shape and its locations on color-color and color-magnitude diagrams. From the initial list of 54 candidates, we suspect all are likely YSOs, some of which are very embedded; ~40% are likely SED Class I or 0. Approximately 20% of the 54 sources have not been previously identified. By beginning the investigation of YSOs in this region, we are adding to the body of YSO knowledge which can be used to understand the process of star formation. This research was made possible through the NASA/IPAC Teacher Archive Research Program (NITARP) and was funded by NASA Astrophysics Data Program.

  17. Which Stars Go BOOM?

    Science.gov (United States)

    Kalirai, Jason

    2014-10-01

    Intermediate mass stars with M = 6 to 10 Msun will end their lives by either losing mass quiescently and forming massive white dwarfs or by exploding as core collapse type II supernovae. The critical mass separating these two stellar evolution channels is not only a fundamental threshold of stellar astrophysics, but is a crucial ingredient to generate reliable galaxy evolution simulations. Given the steepness of the stellar IMF, small changes in the critical mass directly affects chemical evolution scenarios, energetics, and feedback relations. Although most astronomers reference the critical mass at M = 8 Msun, there is a lack of robust theoretical or observational confirmation of this number. We propose to measure the critical mass directly by verifying the end products of stellar evolution in four rich, young, co-eval stellar populations. With ages of 25 to 60 Myr and total stellar masses >10,000 Msun, the Magellanic Cloud globular clusters NGC 1818, NGC 330, NGC 1805, and NGC 2164 have present-day main-sequence turnoff masses of M = 6.2, 7.2, 8.5, and 9.8 Msun, respectively. Existing photometry verifies that each cluster has a rich upper main sequence of massive stars, and therefore would have formed dozen(s) of stars above the present day turnoff. If those stars did not explode as core collapse supernovae, they will populate a clear blue white dwarf cooling sequence. Our experiment uses the full power, wavelength coverage, and resolution of HST/WFC3 to detect these cooling sequences in high-precision, UV-sensitive color-magnitude diagrams.

  18. Evolution of long-lived globular cluster stars. III. Effect of the initial helium spread on the position of stars in a synthetic Hertzsprung-Russell diagram

    Science.gov (United States)

    Chantereau, W.; Charbonnel, C.; Meynet, G.

    2016-08-01

    Context. Globular clusters host multiple populations of long-lived low-mass stars whose origin remains an open question. Several scenarios have been proposed to explain the associated photometric and spectroscopic peculiarities. They differ, for instance, in the maximum helium enrichment they predict for stars of the second population, which these stars can inherit at birth as the result of the internal pollution of the cluster by different types of stars of the first population. Aims: We present the distribution of helium-rich stars in present-day globular clusters as it is expected in the original framework of the fast-rotating massive stars scenario (FRMS) as first-population polluters. We focus on NGC 6752. Methods: We completed a grid of 330 stellar evolution models for globular cluster low-mass stars computed with different initial chemical compositions corresponding to the predictions of the original FRMS scenario for [Fe/H] = -1.75. Starting from the initial helium-sodium relation that allows reproducing the currently observed distribution of sodium in NGC 6752, we deduce the helium distribution expected in that cluster at ages equal to 9 and 13 Gyr. We distinguish the stars that are moderately enriched in helium from those that are very helium-rich (initial helium mass fraction below and above 0.4, respectively), and compare the predictions of the FRMS framework with other scenarios for globular cluster enrichment. Results: The effect of helium enrichment on the stellar lifetime and evolution reduces the total number of very helium-rich stars that remain in the cluster at 9 and 13 Gyr to only 12% and 10%, respectively, from an initial fraction of 21%. Within this age range, most of the stars still burn their hydrogen in their core, which widens the MS band significantly in effective temperature. The fraction of very helium-rich stars drops in the more advanced evolution phases, where the associated spread in effective temperature strongly decreases. These

  19. A cautionary tale of interpreting O-C diagrams: period instability in a classical RR Lyr Star Z CVn mimicking as a distant companion

    Science.gov (United States)

    Skarka, M.; Liška, J.; Dřevěný, R.; Guggenberger, E.; Sódor, Á.; Barnes, T. G.; Kolenberg, K.

    2018-02-01

    We present a comprehensive study of Z CVn, an RR Lyrae star that shows long-term cyclic variations of its pulsation period. A possible explanation suggested from the shape of the O-C diagram is the light travel-time effect, which we thoroughly examine. We used original photometric and spectroscopic measurements and investigated the period evolution using available maximum times spanning more than one century. If the binary hypothesis is valid, Z CVn orbits around a black hole with minimal mass of 56.5 M_{⊙} on a very wide (Porbit = 78.3 yr) and eccentric orbit (e = 0.63). We discuss the probability of the formation of a black hole-RR Lyrae pair, and, although we found it possible, there is no observational evidence of the black hole in the direction to Z CVn. However, the main objection against the binary hypothesis is the comparison of the systemic radial velocity curve model and spectroscopic observations that clearly show that Z CVn cannot be bound in such a binary. Therefore, the variations of pulsation period are likely intrinsic to the star. This finding represents a discovery/confirmation of a new type of cyclic period changes in RR Lyrae stars. By the analysis of our photometric data, we found that the Blazhko modulation with period of 22.931 d is strongly dominant in amplitude. The strength of the phase modulation varies and is currently almost undetectable. We also estimated photometric physical parameters of Z CVn and investigated their variations during the Blazhko cycle using the inverse Baade-Wesselink method.

  20. Chemically-Deduced Star Formation Histories Of Dwarf Galaxies Using Barium

    Science.gov (United States)

    Duggan, Gina; Kirby, Evan

    2017-06-01

    Dwarf galaxies offer a unique opportunity to study the competing forces of galaxy evolution. Their simpler history (i.e., small size, fewer major mergers, and lack of active galactic nuclei) enables us to isolate different physical mechanisms more easily. The effects of these mechanisms are imprinted on the galaxy's star formation history. Traditionally, star formation histories are determined from color-magnitude diagrams. However, chemical abundances can increase the precision of this measurement. Here we present a simplistic galactic chemical evolution model to infer the star formation history. Chemical abundances are measured from spectra obtained with Keck/DEIMOS medium-resolution spectroscopy for over a hundred red giant stars from several satellite dwarf spheroidal galaxies and globular clusters. We focus our work on iron and barium abundances because they predominantly trace Type Ia supernovae and asymptotic giant branch stars, respectively. The different timescales of these two nucleosynthetic sources can be used to measure a finely resolved star formation history, especially when combined with existing [α/Fe] measurements. These models will inform the details of early star formation in dwarf galaxies and how it is affected by various physical processes, such as reionization and tidal stripping.

  1. Spatial Configuration of Stars Around Three Metal-poor Globular Clusters in the Galatic Bulge, NGC 6266, NGC 6273, and NGC 6681 : Surface Density Map and Radial Density Profile

    Directory of Open Access Journals (Sweden)

    Mihwa Han

    2017-06-01

    Full Text Available We present extra-tidal features of spatial configuration of stars around three metal-poor globular clusters (NGC 6266, NGC 6273, NGC 6681 located in the Galactic bulge. The wide-field photometric data were obtained in BVI bands with the MOSAIC II camera at CTIO 4 m Blanco telescope. The derived color-magnitude diagrams (CMDs contain stars in a total 71´×71´area including a cluster and its surrounding field outside of the tidal radius of the cluster. Applying statistical filtering technique, we minimized the field star contaminations on the obtained cluster CMDs and extracted the cluster members. On the spatial stellar density maps around the target clusters, we found overdensity features beyond the tidal radii of the clusters. We also found that the radial density profiles of the clusters show departures from the best-fit King model for their outer regions which support the overdensity patterns.

  2. Recovering the star formation rate in the solar neighborhood

    Science.gov (United States)

    Cignoni, M.; Degl'Innocenti, S.; Prada Moroni, P. G.; Shore, S. N.

    2006-12-01

    Aims.This paper develops a method for obtaining the star formation histories of a mixed, resolved population through the use of color-magnitude diagrams (CMDs). The method provides insight into the local star formation rate, analyzing the observations of the Hipparcos satellite through a comparison with synthetic CMDs computed for different histories with an updated stellar evolution library. Methods: .Parallax and photometric uncertainties are included explicitly and corrected using the Bayesian Richardson-Lucy algorithm. We first describe our verification studies using artificial data sets. From this sensitivity study, the critical factors determining the success of a recovery for a known star formation rate are a partial knowledge of the IMF and the age-metallicity relation, and sample contamination by clusters and moving groups (special populations whose histories are different than that of the whole sample). Unresolved binaries are less important impediments. We highlight how these limit the method. Results: .For the real field sample, complete to MV integrated star formation rates may indicate a global origin, possibly a collision with a satellite galaxy. We also discuss applications of this technique to general photometric surveys of other complex systems (e.g. Local Group dwarf galaxies) where the distances are well known.

  3. PHAT. XIX. The Ancient Star Formation History of the M31 Disk

    Science.gov (United States)

    Williams, Benjamin F.; Dolphin, Andrew E.; Dalcanton, Julianne J.; Weisz, Daniel R.; Bell, Eric F.; Lewis, Alexia R.; Rosenfield, Philip; Choi, Yumi; Skillman, Evan; Monachesi, Antonela

    2017-09-01

    We map the star formation history across M31 by fitting stellar evolution models to color-magnitude diagrams of each 83″ × 83″ (0.3 × 1.4 kpc, deprojected) region of the Panchromatic Hubble Andromeda Treasury (PHAT) survey outside of the innermost 6\\prime × 12\\prime portion. We find that most of the star formation occurred prior to ˜8 Gyr ago, followed by a relatively quiescent period until ˜4 Gyr ago, a subsequent star formation episode about 2 Gyr ago, and a return to relative quiescence. There appears to be little, if any, structure visible for populations with ages older than 2 Gyr, suggesting significant mixing since that epoch. Finally, assuming a Kroupa initial mass function from 0.1 to 100 M ⊙, we find that the total amount of star formation over the past 14 Gyr in the area over which we have fit models is 5 × 1010 M ⊙. Fitting the radial distribution of this star formation and assuming azimuthal symmetry, (1.5 ± 0.2) × 1011 M ⊙ of stars has formed in the M31 disk as a whole, (9 ± 2) × 1010 M ⊙ of which has likely survived to the present after accounting for evolutionary effects. This mass is about one-fifth of the total dynamical mass of M31.

  4. Relative Age Dating of Young Star Clusters from YSOVAR

    Science.gov (United States)

    Johnson, Chelen H.; Gibbs, John C.; Linahan, Marcella; Rebull, Luisa; Bernstein, Alexandra E.; Child, Sierra; Eakins, Emma; Elert, Julia T.; Frey, Grace; Gong, Nathaniel; Hedlund, Audrey R.; Karos, Alexandra D.; Medeiros, Emma M.; Moradi, Madeline; Myers, Keenan; Packer, Benjamin M.; Reader, Livia K.; Sorenson, Benjamin; Stefo, James S.; Strid, Grace; Sumner, Joy; Sundeen, Kiera A.; Taylor, Meghan; Ujjainwala, Zakir L.

    2018-01-01

    The YSOVAR (Young Stellar Object VARiability; Rebull et al. 2014) Spitzer Space Telescope observing program monitored a dozen star forming cores in the mid-infrared (3.6 and 4.5 microns). Rebull et al. (2014) placed these cores in relative age order based on numbers of YSO candidates in SED class bins (I, flat, II, III), which is based on the slope of the SED between 2 and 25 microns. PanSTARRS data have recently been released (Chambers et al. 2016); deep optical data are now available over all the YSOVAR clusters. We worked with eight of the YSOVAR targets (IC1396-N, AFGL 490, NGC 1333, Mon R2, GGD 12-15, L 1688, IRAS 20050+2720, and Ceph C) and the YSO candidates identified therein as part of YSOVAR (through their infrared colors or X-ray detections plus a star-like SED; see Rebull et al. 2014). We created and examined optical and NIR color-magnitude diagrams and color-color diagrams of these YSO candidates to determine if the addition of optical data contradicted or reinforced the relative age dating of the clusters obtained with SED class ratios.This project is a collaborative effort of high school students and teachers from three states. We analyzed data individually and later collaborated online to compare results. This project is the result of many years of work with the NASA/IPAC Teacher Archive Research Program (NITARP).

  5. The Abundance of Lithium in an ABG Star in the Globular Cluster M3 (NGC 5272)

    Science.gov (United States)

    Givens, R. A.; Pilachowski, C. A.

    2016-12-01

    A survey of red giants in the globular cluster M3 with the Hydra multi-object spectrograph on the WIYN 3.5 m telescope indicated a prominent Li i 6707 Å feature in the red giant vZ 1050. Followup spectroscopy with the ARC 3.5 m telescope confirmed this observation and yielded a derived abundance of A(Li)NLTE = 1.6 ± 0.05. In addition, the high oxygen and low sodium abundances measured from the same spectrum suggest that vZ 1050 is a first generation cluster star. The location of vZ 1050 above the horizontal branch and blueward of the red giant branch in the cluster’s color-magnitude diagram places vZ 1050 on M3's asymptotic giant branch. The likely source for the enhanced lithium abundance is the Cameron-Fowler mechanism operating in vZ 1050 itself.

  6. Variable Stars and Stellar Populations in Andromeda XXVII. IV. An Off-centered, Disrupted Galaxy

    Science.gov (United States)

    Cusano, Felice; Garofalo, Alessia; Clementini, Gisella; Cignoni, Michele; Muraveva, Tatiana; Tessicini, Gianni; Testa, Vincenzo; Paris, Diego; Federici, Luciana; Marconi, Marcella; Ripepi, Vincenzo; Musella, Ilaria

    2017-12-01

    We present B and V time-series photometry of the M31 satellite galaxy Andromeda XXVII (And XXVII) that we observed with the Large Binocular Cameras of the Large Binocular Telescope. In the field of And XXVII we have discovered a total of 90 variables: 89 RR Lyrae stars and 1 Anomalous Cepheid. The average period of the fundamental mode RR Lyrae stars (RRab) =0.59 {days} (σ = 0.05 day) and the period-amplitude diagram place And XXVII in the class of Oosterhoff I/Intermediate objects. Combining information from the color-magnitude diagram (CMD) and the variable stars, we find evidence for a single old and metal-poor stellar population with [Fe/H] ˜ -1.8 dex and t ˜ 13 Gyr in And XXVII. The spatial distributions of RR Lyrae and red giant branch (RGB) stars give clear indication that And XXVII is a completely disrupted system. This is also supported by the spread observed along the line of sight in the distance to the RR Lyrae stars. The highest concentration of RGB and RR Lyrae stars is found in a circular area of 4 arcmin in radius, centered about 0.°2 in the southeast direction from Richardson et al.’s center coordinates of And XXVII. The CMD of this region is well-defined, with a prominent RGB and 15 RR Lyrae stars (out of the 18 found in the region) tracing a very tight horizontal branch at =25.24 {mag} σ = 0.06 mag (average over 15 stars). We show that And XXVII is a strong candidate building block of the M31 halo. Based on data collected with the Large Binocular Cameras at the Large Binocular Telescope, PI: G. Clementini.

  7. Delayed star formation in isolated dwarf galaxies: Hubble space telescope star formation history of the Aquarius dwarf irregular

    Energy Technology Data Exchange (ETDEWEB)

    Cole, Andrew A. [School of Physical Sciences, University of Tasmania, Private Bag 37, Hobart, Tasmania, 7001 Australia (Australia); Weisz, Daniel R. [Department of Astronomy, University of California at Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Dolphin, Andrew E. [Raytheon, 1151 East Hermans Road, Tucson, AZ 85706 (United States); Skillman, Evan D. [Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55441 (United States); McConnachie, Alan W. [NRC Herzberg Institute of Astrophysics, Dominion Astrophysical Observatory, Victoria, BC, V9E 2E7 Canada (Canada); Brooks, Alyson M. [Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Leaman, Ryan, E-mail: andrew.cole@utas.edu.au, E-mail: drw@ucsc.edu, E-mail: adolphin@raytheon.com, E-mail: skillman@astro.umn.edu, E-mail: alan.mcconnachie@nrc-cnrc.gc.ca, E-mail: abrooks@physics.rutgers.edu, E-mail: rleaman@iac.es [Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife (Spain)

    2014-11-01

    We have obtained deep images of the highly isolated (d = 1 Mpc) Aquarius dwarf irregular galaxy (DDO 210) with the Hubble Space Telescope Advanced Camera for Surveys. The resulting color-magnitude diagram (CMD) reaches more than a magnitude below the oldest main-sequence turnoff, allowing us to derive the star formation history (SFH) over the entire lifetime of the galaxy with a timing precision of ≈10% of the lookback time. Using a maximum likelihood fit to the CMD we find that only ≈10% of all star formation in Aquarius took place more than 10 Gyr ago (lookback time equivalent to redshift z ≈ 2). The star formation rate increased dramatically ≈6-8 Gyr ago (z ≈ 0.7-1.1) and then declined until the present time. The only known galaxy with a more extreme confirmed delay in star formation is Leo A, a galaxy of similar M {sub H} {sub I}/M {sub *}, dynamical mass, mean metallicity, and degree of isolation. The delayed stellar mass growth in these galaxies does not track the mean dark matter accretion rate from CDM simulations. The similarities between Leo A and Aquarius suggest that if gas is not removed from dwarf galaxies by interactions or feedback, it can linger for several gigayears without cooling in sufficient quantity to form stars efficiently. We discuss possible causes for the delay in star formation including suppression by reionization and late-time mergers. We find reasonable agreement between our measured SFHs and select cosmological simulations of isolated dwarfs. Because star formation and merger processes are both stochastic in nature, delayed star formation in various degrees is predicted to be a characteristic (but not a universal) feature of isolated small galaxies.

  8. Parametric diagram

    DEFF Research Database (Denmark)

    Hermund, Anders

    2010-01-01

    This paper will introduce the PhD research into applied 3d modeling and parametric design outlining the idea of a parametric diagram linked to philosophical and applied examples.......This paper will introduce the PhD research into applied 3d modeling and parametric design outlining the idea of a parametric diagram linked to philosophical and applied examples....

  9. On the Origin of Sub-subgiant Stars. I. Demographics

    Science.gov (United States)

    Geller, Aaron M.; Leiner, Emily M.; Bellini, Andrea; Gleisinger, Robert; Haggard, Daryl; Kamann, Sebastian; Leigh, Nathan W. C.; Mathieu, Robert D.; Sills, Alison; Watkins, Laura L.; Zurek, David

    2017-05-01

    Sub-subgiants are stars that are observed to be redder than normal main-sequence stars and fainter than normal subgiant (and giant) stars in an optical color-magnitude diagram (CMD). The red straggler stars, which lie redward of the red giant branch, may be related and are often grouped together with the sub-subgiants in the literature. These stars defy our standard theory of single-star evolution and are important tests for binary evolution and stellar collision models. In total, we identify 65 sub-subgiants (SSG) and red stragglers (RS) in 16 open and globular star clusters from the literature; 50 of these, including 43 sub-subgiants, pass our strict membership selection criteria (though the remaining sources may also be cluster members). In addition to their unique location on the CMD, we find that at least 58% (25/43) of sub-subgiants in this sample are X-ray sources with typical 0.5-2.5 keV luminosities of order 1030-1031 erg s-1. Their X-ray luminosities and optical-to-X-ray flux ratios are similar to those of RS CVn active binaries. At least 65% (28/43) of the sub-subgiants in our sample are variables, 21 of which are known to be radial-velocity binaries. Typical variability periods are ≲15 days. At least 33% (14/43) of the sub-subgiants are Hα emitters. These observational demographics provide strong evidence that binarity is important for sub-subgiant formation. Finally, we find that the number of sub-subgiants per unit mass increases toward lower-mass clusters, such that the open clusters in our sample have the highest specific frequencies of sub-subgiants.

  10. The optical gravitational lensing experiment. Variable stars in globular clusters. I. Fields 5139A-C in ω Centauri.

    Science.gov (United States)

    Kaluzny, J.; Kubiak, M.; Szymanski, M.; Udalski, A.; Krzeminski, W.; Mateo, M.

    1996-11-01

    Three fields covering the central part of the globular cluster ω Cen were surveyed in a search for variable stars. We present V-band light curves for 39 periodic variables: 24 SX Phe stars, 7 contact binaries, 5 detached or semi-detached binaries, and 3 likely spotted variables (FK Com or RS CVn type stars). Only 2 of these variables were previously known. All SX Phe stars and all contact binaries from our sample belong to blue stragglers. Observed properties of these stars are consistent with their cluster membership. Of particular interest is detection of two well detached binaries with periods P=1.50day and P=2.47day. Further study of these two binaries can provide direct information about properties of turnoff stars in ω Cen. An incomplete light curve of a Mira variable known as V2 was obtained. We present V vs. V-I color-magnitude diagrams for the monitored part of the cluster.

  11. Electronic diagrams

    CERN Document Server

    Colwell, Morris A

    1976-01-01

    Electronic Diagrams is a ready reference and general guide to systems and circuit planning and in the preparation of diagrams for both newcomers and the more experienced. This book presents guidelines and logical procedures that the reader can follow and then be equipped to tackle large complex diagrams by recognition of characteristic 'building blocks' or 'black boxes'. The goal is to break down many of the barriers that often seem to deter students and laymen in learning the art of electronics, especially when they take up electronics as a spare time occupation. This text is comprised of nin

  12. SCADA Diagram

    OpenAIRE

    Rose, Matthew

    2004-01-01

    Matthew Rose worked at the Naval Postgraduate School as a graphic designer from February 2002-November 2011. His work for NPS included logos, brochures, business packs, movies/presentations, posters, the CyberSiege video game and many other projects. This material was organized and provided by the artist, for inclusion in the NPS Archive, Calhoun. Includes these files: Plan_ver.ai; powerline.jpg; SCADA diagram.ai; SCADA diagram.pdf; SCADA diagramsmall.pdf; SCADA2.pdf

  13. THE PAndAS VIEW OF THE ANDROMEDA SATELLITE SYSTEM. I. A BAYESIAN SEARCH FOR DWARF GALAXIES USING SPATIAL AND COLOR-MAGNITUDE INFORMATION

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Nicolas F.; Ibata, Rodrigo A. [Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l' Université, F-67000 Strasbourg (France); McConnachie, Alan W. [NRC Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Mackey, A. Dougal [Research School of Astronomy and Astrophysics, The Australian National University, Mount Stromlo Observatory, via Cotter Road, Weston, ACT 2611 (Australia); Ferguson, Annette M. N. [Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Irwin, Michael J. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Lewis, Geraint F. [Institute of Astronomy, School of Physics A28, University of Sydney, NSW 2006 (Australia); Fardal, Mark A., E-mail: nicolas.martin@astro.unistra.fr [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)

    2013-10-20

    We present a generic algorithm to search for dwarf galaxies in photometric catalogs and apply it to the Pan-Andromeda Archaeological Survey (PAndAS). The algorithm is developed in a Bayesian framework and, contrary to most dwarf galaxy search codes, makes use of both the spatial and color-magnitude information of sources in a probabilistic approach. Accounting for the significant contamination from the Milky Way foreground and from the structured stellar halo of the Andromeda galaxy, we recover all known dwarf galaxies in the PAndAS footprint with high significance, even for the least luminous ones. Some Andromeda globular clusters are also recovered and, in one case, discovered. We publish a list of the 143 most significant detections yielded by the algorithm. The combined properties of the 39 most significant isolated detections show hints that at least some of these trace genuine dwarf galaxies, too faint to be individually detected. Follow-up observations by the community are mandatory to establish which are real members of the Andromeda satellite system. The search technique presented here will be used in an upcoming contribution to determine the PAndAS completeness limits for dwarf galaxies. Although here tuned to the search of dwarf galaxies in the PAndAS data, the algorithm can easily be adapted to the search for any localized overdensity whose properties can be modeled reliably in the parameter space of any catalog.

  14. An all-sky sample of intermediate-mass star-forming regions

    Energy Technology Data Exchange (ETDEWEB)

    Lundquist, Michael J.; Kobulnicky, Henry A.; Alexander, Michael J. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Kerton, Charles R. [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Arvidsson, Kim [Trull School of Sciences and Mathematics, Schreiner University, 2100 Memorial Boulevard, Kerrville, TX 78028 (United States)

    2014-04-01

    We present an all-sky sample of 984 candidate intermediate-mass Galactic star-forming regions that are color selected from the Infrared Astronomical Satellite (IRAS) Point Source Catalog and morphologically classify each object using mid-infrared Wide-field Infrared Survey Explorer (WISE) images. Of the 984 candidates, 616 are probable star-forming regions (62.6%), 128 are filamentary structures (13.0%), 39 are point-like objects of unknown nature (4.0%), and 201 are galaxies (20.4%). We conduct a study of four of these regions, IRAS 00259+5625, IRAS 00420+5530, IRAS 01080+5717, and IRAS 05380+2020, at Galactic latitudes |b| > 5° using optical spectroscopy from the Wyoming Infrared Observatory, along with near-infrared photometry from the Two-Micron All Sky Survey, to investigate their stellar content. New optical spectra, color-magnitude diagrams, and color-color diagrams reveal their extinctions, spectrophotometric distances, and the presence of small stellar clusters containing 20-78 M {sub ☉} of stars. These low-mass diffuse star clusters contain ∼65-250 stars for a typical initial mass function, including one or more mid-B stars as their most massive constituents. Using infrared spectral energy distributions we identify young stellar objects near each region and assign probable masses and evolutionary stages to the protostars. The total infrared luminosity lies in the range 190-960 L {sub ☉}, consistent with the sum of the luminosities of the individually identified young stellar objects.

  15. The star formation histories of local group dwarf galaxies. II. Searching for signatures of reionization

    Energy Technology Data Exchange (ETDEWEB)

    Weisz, Daniel R. [Department of Astronomy, University of California at Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Dolphin, Andrew E. [Raytheon Company, 1151 East Hermans Road, Tucson, AZ 85756 (United States); Skillman, Evan D. [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States); Holtzman, Jon [Department of Astronomy, New Mexico State University, Box 30001, 1320 Frenger Street, Las Cruces, NM 88003 (United States); Gilbert, Karoline M.; Dalcanton, Julianne J.; Williams, Benjamin F., E-mail: drw@ucsc.edu [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)

    2014-07-10

    We search for signatures of reionization in the star formation histories (SFHs) of 38 Local Group dwarf galaxies (10{sup 4} < M{sub *} < 10{sup 9} M{sub ☉}). The SFHs are derived from color-magnitude diagrams using archival Hubble Space Telescope/Wide Field Planetary Camera 2 imaging. Only five quenched galaxies (And V, And VI, And XIII, Leo IV, and Hercules) are consistent with forming the bulk of their stars before reionization, when full uncertainties are considered. Observations of 13 of the predicted 'true fossils' identified by Bovill and Ricotti show that only two (Hercules and Leo IV) indicate star formation quenched by reionization. However, both are within the virial radius of the Milky Way and evidence of tidal disturbance complicates this interpretation. We argue that the late-time gas capture scenario posited by Ricotti for the low mass, gas-rich, and star-forming fossil candidate Leo T is observationally indistinguishable from simple gas retention. Given the ambiguity between environmental effects and reionization, the best reionization fossil candidates are quenched low mass field galaxies (e.g., KKR 25).

  16. ON THE ESTIMATION OF RANDOM UNCERTAINTIES OF STAR FORMATION HISTORIES

    Energy Technology Data Exchange (ETDEWEB)

    Dolphin, Andrew E., E-mail: adolphin@raytheon.com [Raytheon Company, Tucson, AZ, 85734 (United States)

    2013-09-20

    The standard technique for measurement of random uncertainties of star formation histories (SFHs) is the bootstrap Monte Carlo, in which the color-magnitude diagram (CMD) is repeatedly resampled. The variation in SFHs measured from the resampled CMDs is assumed to represent the random uncertainty in the SFH measured from the original data. However, this technique systematically and significantly underestimates the uncertainties for times in which the measured star formation rate is low or zero, leading to overly (and incorrectly) high confidence in that measurement. This study proposes an alternative technique, the Markov Chain Monte Carlo (MCMC), which samples the probability distribution of the parameters used in the original solution to directly estimate confidence intervals. While the most commonly used MCMC algorithms are incapable of adequately sampling a probability distribution that can involve thousands of highly correlated dimensions, the Hybrid Monte Carlo algorithm is shown to be extremely effective and efficient for this particular task. Several implementation details, such as the handling of implicit priors created by parameterization of the SFH, are discussed in detail.

  17. Proper motion with HST: Searching for high-velocity stars in the core of the globular cluster 47 Tucanae

    Energy Technology Data Exchange (ETDEWEB)

    Meylan, G. [European Southern Observatory, Garching b. Muenchen, (Germany); Minniti, D. [Lawrence Livermore National Lab., CA (United States); Pryor, C. [Rutgers, Univ., Dept. of Physics and Astronomy, New Jersey (United States); Tinney, C.G. [Anglo-Australian Observatory, Epping, NSW (Australia); Phinney, E.S. [Theoretical Astrophysics, Caltech, Pasadena, (United States); Sams, B. [Eagle-Picher Industries, Inc., Joplin, MO (United States). Electronics Div.

    1996-02-13

    Binary stars play an essential role during the late phases of the dynamical evolution of a globular cluster. They transfer energy to passing stars and so can strongly influence the cluster evolution, enough to delay, halt, and even reverse core collapse. Hard binaries are known to exist in cluster cores, e.g., in the form of millisecond pulsars (about half of the millisecond pulsars observed in 47 Tucanae are such hard binaries). The presence of hard binaries may also be revealed by searching for the by-products of close encounters: high- velocity stars, such as those discovered in the core of 47 Tuc by Meylan et al. (1991) and Gebhardt et al. (1995). These studies represent the limit of the radial velocity data which can be obtained from the ground. If more progress is to be made, it must come through obtaining proper motions--a task for which {ital only} the Hubble Space Telescope (HST) is suitable. We are using WFPC2 to obtain deep U (F300W) images of the core of 47 Tuc at three different epochs over two years, with which we will measure differential proper motions to a 1-{sigma} limit of 0.23 mas/yr. This--rather conservative--estimate corresponds to a 5-{sigma} detection of all stars with tangential velocities greater than 22 km s{sup -1}. By using the F300W filter we can measure stars over the whole color-magnitude diagram, from the red-giant branch to well down the main sequence. Such a complete census will provide unique constraints as a function of the stellar mass on relaxation processes, collision and ejection rates, and the velocity distribution. Here we report on the first-epoch (Cycle 5) observations of this project. Although no proper motions are available yet, some preliminary by-product results are presented. These include luminosity functions and color-magnitude diagrams for the core of 47 Tuc and the light curves of variable blue straggler stars and of a candidate X-ray source. 32 refs., 5 figs.

  18. The Impact of Star Formation Histories on Stellar Mass Estimation: Implications from the Local Group Dwarf Galaxies

    Science.gov (United States)

    Zhang, Hong-Xin; Puzia, Thomas H.; Weisz, Daniel R.

    2017-11-01

    Building on the relatively accurate star formation histories (SFHs) and metallicity evolution of 40 Local Group (LG) dwarf galaxies derived from resolved color-magnitude diagram modeling, we carried out a comprehensive study of the influence of SFHs, metallicity evolution, and dust extinction on the UV-to-near-IR color-mass-to-light ratio (color-{log}{{{\\Upsilon }}}\\star (λ)) distributions and M ⋆ estimation of local universe galaxies. We find that (1) the LG galaxies follow color-{log}{{{\\Upsilon }}}\\star (λ) relations that fall in between the ones calibrated by previous studies; (2) optical color-{log}{{{\\Upsilon }}}\\star (λ) relations at higher [M/H] are generally broader and steeper; (3) the SFH “concentration” does not significantly affect the color-{log}{{{\\Upsilon }}}\\star (λ) relations; (4) light-weighted ages }λ and metallicities }λ together constrain {log}{{{\\Upsilon }}}\\star (λ) with uncertainties ranging from ≲0.1 dex for the near-IR up to 0.2 dex for the optical passbands; (5) metallicity evolution induces significant uncertainties to the optical but not near-IR {{{\\Upsilon }}}\\star (λ) at a given }λ and }λ ; (6) the V band is the ideal luminance passband for estimating {{{\\Upsilon }}}\\star (λ) from single colors, because the combinations of {{{\\Upsilon }}}\\star (V) and optical colors such as B - V and g - r exhibit the weakest systematic dependences on SFHs, metallicities, and dust extinction; and (7) without any prior assumption on SFHs, M ⋆ is constrained with biases ≲0.3 dex by the optical-to-near-IR SED fitting. Optical passbands alone constrain M ⋆ with biases ≲0.4 dex (or ≲0.6 dex) when dust extinction is fixed (or variable) in SED fitting. SED fitting with monometallic SFH models tends to underestimate M ⋆ of real galaxies. M ⋆ tends to be overestimated (or underestimated) at the youngest (or oldest) }{mass}.

  19. First Hubble Space Telescope observations of the brightest stars in the Virgo galaxy M100 = NGC 4321

    Science.gov (United States)

    Freedman, Wendy L.; Madore, Barry F.; Stetson, Peter B.; Hughes, Shaun M. G.; Holtzman, Jon A.; Mould, Jeremy R.; Trauger, John T.; Gallagher, John S., III; Ballester, Gilda E.; Burrows, Christopher J.

    1994-01-01

    As part of both the Early Release Observations from the Hubble Space Telescope (HST) and the Key Project on the Extragalactic Distance Scale, we have obtained multiwavelength BVR Wide Field/Planetary Camera-2 (WFPC2) images for the face-on Virgo cluster spiral galaxy M100 = NGC 4321. We report here preliminary results from those observations, in the form of a color-magnitude diagram for approximately 11,500 stars down to V approximately 27 mag and a luminosity function for the brightest blue stars which is found to have a slope of 0.7, in excellent agreement with previous results obtained for significantly nearer galaxies. With the increased resolution now available using WFPC2, the number of galaxies in which we can directly measure Population I stars and thereby quantify the recent evolution, as well as test stellar evolution theory, has dramatically increased by at least a factor of 100. Finally, we find that the stars are present in M100 at the colors and luminosities expected for the brightest Cepheid variables in galaxies.

  20. A Novel Method to Automatically Detect and Measure the Ages of Star Clusters in Nearby Galaxies: Application to the Large Magellanic Cloud

    Science.gov (United States)

    Bitsakis, T.; Bonfini, P.; González-Lópezlira, R. A.; Ramírez-Siordia, V. H.; Bruzual, G.; Charlot, S.; Maravelias, G.; Zaritsky, D.

    2017-08-01

    We present our new, fully automated method to detect and measure the ages of star clusters in nearby galaxies, where individual stars can be resolved. The method relies purely on statistical analysis of observations and Monte-Carlo simulations to define stellar overdensities in the data. It decontaminates the cluster color-magnitude diagrams and, using a revised version of the Bayesian isochrone fitting code of Ramírez-Siordia et al., estimates the ages of the clusters. Comparisons of our estimates with those from other surveys show the superiority of our method to extract and measure the ages of star clusters, even in the most crowded fields. An application of our method is shown for the high-resolution, multiband imaging of the Large Magellanic Cloud. We detect 4850 clusters in the 7 deg2 we surveyed, 3451 of which have not been reported before. Our findings suggest multiple epochs of star cluster formation, with the most probable occurring ˜310 Myr ago. Several of these events are consistent with the epochs of the interactions among the Large and Small Magellanic Clouds, and the Galaxy, as predicted by N-body numerical simulations. Finally, the spatially resolved star cluster formation history may suggest an inside-out cluster formation scenario throughout the LMC, for the past 1 Gyr.

  1. Hubble Space Telescope imaging of super-star clusters in NGC 1569 and NGC 1705

    Science.gov (United States)

    O'Connell, Robert W.; Gallagher, John S., III; Hunter, Deidre A.

    1994-01-01

    We examine the structural properties of three super-star clusters in the nearby, H I-rich galaxies NGC 1569 and NGC 1705. The clusters, which have total absolute V magnitudes between -13.3 and -14.1, appear to be point sources on ground-based images but are partially resolved in new images obtained with the Hubble Space Telescope (HST) Planetary Camera. From deconvolved V- and I-band images we find that the three clusters have very compact cores with extended halos that are partially resolved into individual stars. Using new distances to the galaxies derived from color-magnitude diagrams for field stars, we find that the half-light radii are 2.2-3.4 pc. The cluster in NGC 1705 is barely resolved in the HST images. The clusters in NGC 1569, on the other hand, show significant substructure in their cores and ellipticities that are comparable to the flattenings seen in young clusters in the Large Magellanic Cloud (LMC). The clusters show internal (V-I) color gradients. The properties of these clusters are similar to R136, the core of the luminous star-forming complex 30 Doradus in the LMC, except that R136 has a lower luminosity and central surface brightness. The half-light surface brightness of the brightest cluster (NGC 1569 A) is 1.3 x 10(exp 6) L(sub v) solar/ sq cm, which is over 65 times higher than R136 and 1200 times higher than the mean rich LMC star cluster other than R136 after allowing for aging effects. The next brightest clusters in each of these galaxies are greater than or = 2 mag fainter. Thus, the super-star clusters represent an extreme but uncommon mode of star formation. In terms of luminosity and size, they appear to be good analogs of young globular clusters.

  2. Using a Weak CN Spectral Feature as a Marker for Massive AGB Stars in the Andromeda Galaxy

    Science.gov (United States)

    Guhathakurta, Puragra; Kamath, Anika; Sales, Alyssa; Sarukkai, Atmika; Hays, Jon; PHAT Collaboration; SPLASH Collaboration

    2017-01-01

    The Panchromatic Hubble Andromeda Treasury (PHAT) survey has produced six-filter photometry at near-ultraviolet, optical and nearly infrared wavelengths (F275W, F336W, F475W, F814W, F110W and F160W) for over 100 million stars in the disk of the of the Andromeda galaxy (M31). As part of the Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo (SPLASH) survey, medium resolution (R ~ 2000) spectra covering the wavelength range 4500-9500A were obtained for over 5000 relatively bright stars from the PHAT source catalog using the Keck II 10-meter telescope and DEIMOS spectrograph. While searching for carbon stars in the spectroscopic data set, we discovered a rare population of stars that show a weak CN spectral absorption feature at ~7900A (much weaker than the CN feature in typical carbon stars) along with other spectral absorption features like TiO and the Ca triplet that are generally not present/visible in carbon star spectra but that are typical for normal stars with oxygen rich atmospheres. These 150 or so "weak CN" stars appear to be fairly localized in six-filter space (i.e., in various color-color and color-magnitude diagrams) but are generally offset from carbon stars. Comparison to PARSEC model stellar tracks indicates that these weak CN stars are probably massive (5-10 Msun) asymptotic giant branch (AGB) stars in a relatively short-lived core helium burning phase of their evolution. Careful spectroscopic analysis indicates that the details of the CN spectral feature are about 3-4x weaker in weak CN stars than in carbon stars. The kinematics of weak CN stars are similar to those of other young stars (e.g., massive main sequence stars) and reflect the well ordered rotation of M31's disk.This research project is funded in part by NASA/STScI and the National Science Foundation. Much of this work was carried out by high school students and undergraduates under the auspices of the Science Internship Program and LAMAT program at the University of

  3. The evolution of massive stars

    Science.gov (United States)

    1982-01-01

    The hypotheses underlying theoretical studies of the evolution of massive model stars with and without mass loss are summarized. The evolutionary tracks followed by the models across theoretical Hertzsprung-Russell (HR) diagrams are compared with the observed distribution of B stars in an HR diagram. The pulsational properties of models of massive star are also described.

  4. On the Origin of Sub-subgiant Stars. II. Binary Mass Transfer, Envelope Stripping, and Magnetic Activity

    Science.gov (United States)

    Leiner, Emily; Mathieu, Robert D.; Geller, Aaron M.

    2017-05-01

    Sub-subgiant stars (SSGs) lie to the red of the main sequence and fainter than the red giant branch in cluster color-magnitude diagrams (CMDs), a region not easily populated by standard stellar evolution pathways. While there has been speculation on what mechanisms may create these unusual stars, no well-developed theory exists to explain their origins. Here we discuss three hypotheses of SSG formation: (1) mass transfer in a binary system, (2) stripping of a subgiant’s envelope, perhaps during a dynamical encounter, and (3) reduced luminosity due to magnetic fields that lower convective efficiency and produce large starspots. Using the stellar evolution code MESA, we develop evolutionary tracks for each of these hypotheses, and compare the expected stellar and orbital properties of these models with six known SSGs in the two open clusters M67 and NGC 6791. All three of these mechanisms can create stars or binary systems in the SSG CMD domain. We also calculate the frequency with which each of these mechanisms may create SSG systems, and find that the magnetic field hypothesis is expected to create SSGs with the highest frequency in open clusters. Mass transfer and envelope stripping have lower expected formation frequencies, but may nevertheless create occasional SSGs in open clusters. They may also be important mechanisms to create SSGs in higher mass globular clusters. This is paper number 74 in the WIYN Open Cluster Study.

  5. From State Diagram to Class Diagram

    DEFF Research Database (Denmark)

    Borch, Ole; Madsen, Per Printz

    2009-01-01

    UML class diagram and Java source code are interrelated and Java code is a kind of interchange format. Working with UML state diagram in CASE tools, a corresponding xml file is maintained. Designing state diagrams is mostly performed manually using design patterns and coding templates - a time...... consuming process. This article demonstrates how to compile such a diagram into Java code and later, by reverse engineering, produce a class diagram. The process from state diagram via intermediate SAX parsed xml file to Apache Velocity generated Java code is described. The result is a fast reproducible...

  6. Interstellar Reddening Effect on the Age Dating of Population II Stars

    Directory of Open Access Journals (Sweden)

    Sergio Ortolani

    2017-06-01

    Full Text Available The age measurement of the stellar halo component of the Galaxy is based mainly on the comparison of the main sequence turn-off luminosity of the globular cluster (GC stars with theoretical isochrones. The standard procedure includes a vertical shift, in order to account for the distance and extinction to the cluster, and a horizontal one, to compensate the reddening. However, the photometry is typically performed with broad-band filters where the shape of the stellar spectra introduces a shift of the effective wavelength response of the system, dependent on the effective temperature (or color index of the star. The result is an increasing distortion—actually a rotation and a progressive compression with the temperature—of the color-magnitude diagrams relatively to the standard unreddened isochrones, with increasing reddening. This effect is usually negligible for reddening E ( B - V on the order of or smaller than 0.15, but it can be quite relevant at larger extinction values. While the ratio of the absorption to the reddening is widely discussed in the literature, the importance of the latter effect is often overlooked. In this contribution, we present isochron simulations and discuss the expected effects on age dating of high-reddening globular clusters.

  7. Viral pathogenesis in diagrams

    National Research Council Canada - National Science Library

    Tremblay, Michel; Berthiaume, Laurent; Ackermann, Hans-Wolfgang

    2001-01-01

    .... The 268 diagrams in Viral Pathogenesis in Diagrams were selected from over 800 diagrams of English and French virological literature, including one derived from a famous drawing by Leonardo da Vinci...

  8. Stellar Populations and Star Formation History of the Metal-poor Dwarf Galaxy DDO 68

    Science.gov (United States)

    Sacchi, E.; Annibali, F.; Cignoni, M.; Aloisi, A.; Sohn, T.; Tosi, M.; van der Marel, R. P.; Grocholski, A. J.; James, B.

    2016-10-01

    We present the star formation history (SFH) of the extremely metal-poor dwarf galaxy DDO 68, based on our photometry with the Advanced Camera for Surveys. With a metallicity of only 12+{log}({{O}}/{{H}})=7.15 and a very isolated location, DDO 68 is one of the most metal-poor galaxies known. It has been argued that DDO 68 is a young system that started forming stars only ˜0.15 Gyr ago. Our data provide a deep and uncontaminated optical color-magnitude diagram (CMD) that allows us to disprove this hypothesis since we find a population of at least ˜1 Gyr old stars. The star formation activity has been fairly continuous over all the look-back time. The current rate is quite low, and the highest activity occurred between 10 and 100 Myr ago. The average star formation rate over the whole Hubble time is ≃0.01 M ⊙ yr-1, corresponding to a total astrated mass of ≃1.3 × 108 M ⊙. Our photometry allows us to infer the distance from the tip of the red giant branch, D = 12.08 ± 0.67 Mpc; however, to let our synthetic CMD reproduce the observed ones, we need a slightly higher distance, D = 12.65 Mpc, or (m - M)0 = 30.51, still inside the errors of the previous determination, and we adopt the latter. DDO 68 shows a very interesting and complex history, with its quite disturbed shape and a long tail, probably due to tidal interactions. The SFH of the tail differs from that of the main body mainly for enhanced activity at recent epochs likely triggered by the interaction. Based on observations obtained with the NASA/ESA Hubble Space Telescope at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy under NASA Contract NAS5-26555.

  9. THE STAR FORMATION HISTORY OF LEO T FROM HUBBLE SPACE TELESCOPE IMAGING

    Energy Technology Data Exchange (ETDEWEB)

    Weisz, Daniel R.; Dalcanton, Julianne J.; Gilbert, Karoline M.; Williams, Benjamin F. [Department of Astronomy, Box 351580, University of Washington, Seattle, WA 98195 (United States); Zucker, Daniel B. [Department of Physics and Astronomy, Macquarie University, Sydney 2109 (Australia); Dolphin, Andrew E. [Raytheon, 1151 E. Hermans Road, Tucson, AZ 85756 (United States); Martin, Nicolas F. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); De Jong, Jelte T. A. [Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 Leiden (Netherlands); Holtzman, Jon A. [Department of Astronomy, New Mexico State University, Box 30001, 1320 Frenger St., Las Cruces, NM 88003 (United States); Bell, Eric F. [Department of Astronomy, University of Michigan, 500 Church St., Ann Arbor, MI 48109 (United States); Belokurov, Vasily; Evans, N. Wyn, E-mail: dweisz@astro.washington.edu [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)

    2012-04-01

    We present the star formation history (SFH) of the faintest known star-forming galaxy, Leo T, based on deep imaging taken with the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2). The HST/WFPC2 color-magnitude diagram (CMD) of Leo T is exquisitely deep, extending {approx}2 mag below the oldest main-sequence turnoff, permitting excellent constraints on star formation at all ages. We use a maximum likelihood CMD fitting technique to measure the SFH of Leo T assuming three different sets of stellar evolution models: Padova (solar-scaled metallicity) and BaSTI (both solar-scaled and {alpha}-enhanced metallicities). The resulting SFHs are remarkably consistent at all ages, indicating that our derived SFH is robust to the choice of stellar evolution model. From the lifetime SFH of Leo T, we find that 50% of the total stellar mass formed prior to z {approx} 1 (7.6 Gyr ago). Subsequent to this epoch, the SFH of Leo T is roughly constant until the most recent {approx}25 Myr, where the SFH shows an abrupt drop. This decrease could be due to a cessation of star formation or stellar initial mass function sampling effects, but we are unable to distinguish between the two scenarios. Overall, our measured SFH is consistent with previously derived SFHs of Leo T. However, the HST-based solution provides improved age resolution and reduced uncertainties at all epochs. The SFH, baryonic gas fraction, and location of Leo T are unlike any of the other recently discovered faint dwarf galaxies in the Local Group, and instead bear strong resemblance to gas-rich dwarf galaxies (irregular or transition), suggesting that gas-rich dwarf galaxies may share common modes of star formation over a large range of stellar mass ({approx}10{sup 5}-10{sup 9} M{sub Sun }).

  10. The Epoch of the First Star Formation in the Closest Metal-Poor Blue Compact Dwarf Galaxy UGC 4483

    Science.gov (United States)

    Aloisi, Alessandra

    2017-08-01

    Metal-poor Blue Compact Dwarf (BCD) galaxies have been interpreted as nearby galaxies in formation. This view has been challenged by HST detection of Red Giant Branch (RGB) stars in all metal-poor BCDs where an RGB tip (TRGB, brightest RGB phase) has been searched for, impling the presence of stars at least 1 Gyr old. Due to the age-metallicity degeneracy, the RGB color provides little insight into the exact star formation history (SFH) beyond 1 Gyr. So, the first SF epoch may have occurred anywhere between 13 and 1 Gyr ago. To resolve this, it is necessary to reach features in the color-magnitude diagram (CMD) that are much fainter than the TRGB. Here we propose new WFC3/UVIS observations (with ACS/WFC in parallel) of the closest metal-poor BCD, UGC 4483. These data will yield an I vs. V-I CMD that goes 4 mag deeper than the TRGB allowing to detect red clump (RC) and horizontal branch (HB) stars. Variable stars of RR Lyrae type will also be detected. With their mere presence, these variables will indisputably prove the existence of a population at least 10 Gyr old. Apparent mag and width of RC, HB and RGB will independently constrain age and metallicity of the old/evolved stars, the presence of multiple SF episodes, their duration and metallicity spread. This deep crowded-field photometric project is only possible with HST. Due to UGC 4483 location in CVZ, it can be done in half the number of orbits that it would otherwise take. Since UGC 4483 is so close, it may be the only BCD for which these questions can be answered in the near future. It provides our best chance for learning about the true cosmological age and evolutionary state of these enigmatic galaxies.

  11. THE EFFECTS OF DIFFERENTIAL REDDENING AND STELLAR ROTATION ON THE APPEARANCE OF MULTIPLE POPULATIONS IN STAR CLUSTERS: THE CASE OF TRUMPLER 20

    Energy Technology Data Exchange (ETDEWEB)

    Platais, I. [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218 (United States); Melo, C. [European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei Muenchen (Germany); Quinn, S. N.; Latham, D. W. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Clem, J. L. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); De Mink, S. E.; Dotter, A.; Kozhurina-Platais, V. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Bellini, A., E-mail: imants@pha.jhu.edu [Dipartimento di Astronomia, Universita di Padova, Vicolo dell' Osservatorio 3, Padova, I-35122 (Italy)

    2012-05-20

    We present a detailed analysis of the upper main sequence of the {approx}1.3 Gyr old open cluster Trumpler 20. High-accuracy BVI photometry combined with the Very Large Telescope/FLAMES medium-resolution spectroscopy of 954 stars is essential to understanding the unusual appearance of the color-magnitude diagram (CMD), initially suggesting multiple populations in Trumpler 20. We show that differential reddening is a dominant contributor to the apparent splitting/widening of the main-sequence turnoff region. At its extreme, the excess differential reddening reaches {Delta}(B - V) {approx} 0.1 while the adopted minimum reddening for the cluster is E(B - V) = 0.36. A unique sample of measured projected rotational velocities indicates that stellar rotation is high near the main-sequence turnoff, reaching vsin i {approx} 180 km s{sup -1}. By dividing the upper main-sequence stars into two equal groups of slow and fast rotators, we find that fast rotators have a marginal blueshift of {delta}(V - I) {approx} -0.01, corresponding to a difference in the median vsin i of {approx}60 km s{sup -1} between these subsamples. We conclude that stellar rotation has an insignificant effect on the morphology of the upper main sequence of this intermediate-age open cluster. Trumpler 20 appears to contain a single coeval population of stars but there is evidence that the red clump is extended.

  12. Anomalous Eclipses of the Young Star RW Aur A

    Science.gov (United States)

    Lamzin, S.; Cheryasov, D.; Chuntonov, G.; Dodin, A.; Grankin, K.; Malanchev, K.; Nadzhip, A.; Safonov, B.; Shakhovskoy, D.; Shenavrin, V.; Tatarnikov, A.; Vozyakova, O.

    2017-06-01

    Results of UBVRIJHKLM photometry, VRI polarimetry and optical spectroscopy of a young star RW Aur A obtained during 2010-11 and 2014-16 dimming events are presented. During the second dimming the star decreased its brightness to ΔV >4.5 mag, polarization of its light in I-band was up to 30 %, and color-magnitude diagramm was similar to that of UX Ori type stars. We conclude that the reason of both dimmings is an eclipses of the star by dust screen, but the size of the screen is much larger than in the case of UXORs.

  13. Early-type Galaxies at z = 1.3. I. The Lynx Supercluster: Cluster and Groups at z = 1.3. Morphology and Color-Magnitude Relation

    Science.gov (United States)

    Mei, Simona; Stanford, S. Adam; Holden, Brad P.; Raichoor, Anand; Postman, Marc; Nakata, Fumiaki; Finoguenov, Alexis; Ford, Holland C.; Illingworth, Garth D.; Kodama, Tadayuki; Rosati, Piero; Tanaka, Masayuki; Huertas-Company, Marc; Rettura, Alessandro; Shankar, Francesco; Carrasco, Eleazar R.; Demarco, Ricardo; Eisenhardt, Peter; Jee, Myungkook J.; Koyama, Yusei; White, Richard L.

    2012-08-01

    We confirm the detection of three groups in the Lynx supercluster, at z ≈ 1.3, through spectroscopic follow-up and X-ray imaging, and we give estimates for their redshifts and masses. We study the properties of the group galaxies compared to the two central clusters, RX J0849+4452 and RX J0848+4453. Using spectroscopic follow-up and multi-wavelength photometric redshifts, we select 89 galaxies in the clusters, of which 41 are spectroscopically confirmed, and 74 galaxies in the groups, of which 25 are spectroscopically confirmed. We morphologically classify galaxies by visual inspection, noting that our early-type galaxy (ETG) sample would have been contaminated at the 30%-40% level by simple automated classification methods (e.g., based on Sérsic index). In luminosity-selected samples, both clusters and groups show high fractions of bulge-dominated galaxies with a diffuse component that we visually identified as a disk and which we classified as bulge-dominated spirals, e.g., Sas. The ETG fractions never rise above ≈50% in the clusters, which is low compared to the fractions observed in other massive clusters at z ≈ 1. In the groups, ETG fractions never exceed ≈25%. However, overall bulge-dominated galaxy fractions (ETG plus Sas) are similar to those observed for ETGs in clusters at z ~ 1. Bulge-dominated galaxies visually classified as spirals might also be ETGs with tidal features or merger remnants. They are mainly red and passive, and span a large range in luminosity. Their star formation seems to have been quenched before experiencing a morphological transformation. Because their fraction is smaller at lower redshifts, they might be the spiral population that evolves into ETGs. For mass-selected samples of galaxies with masses M > 1010.6 M ⊙ within Σ > 500 Mpc-2, the ETG and overall bulge-dominated galaxy fractions show no significant evolution with respect to local clusters, suggesting that morphological transformations might occur at lower masses

  14. Are We Correctly Measuring Star-Formation Rates?

    Science.gov (United States)

    McQuinn, Kristen B.; Skillman, Evan D.; Dolphin, Andrew E.; Mitchell, Noah P.

    2017-01-01

    Integrating our knowledge of star formation (SF) traced by observations at different wavelengths is essential for correctly interpreting and comparing SF activity in a variety of systems and environments. This study compares extinction-corrected, integrated ultraviolet (UV) emission from resolved galaxies with color-magnitude diagram (CMD) based star-formation rates (SFRs) derived from resolved stellar populations and CMD fitting techniques in 19 nearby starburst and post-starburst dwarf galaxies. The data sets are from the panchromatic Starburst Irregular Dwarf Survey (STARBIRDS) and include deep legacy GALEX UV imaging, Hubble Space Telescope optical imaging, and Spitzer MIPS imaging. For the majority of the sample, the integrated near-UV fluxes predicted from the CMD-based SFRs—using four different models—agree with the measured, extinction corrected, integrated near-UV fluxes from GALEX images, but the far-UV (FUV) predicted fluxes do not. Furthermore, we find a systematic deviation between the SFRs based on integrated FUV luminosities and existing scaling relations, and the SFRs based on the resolved stellar populations. This offset is not driven by different SF timescales, variations in SFRs, UV attenuation, nor stochastic effects. This first comparison between CMD-based SFRs and an integrated FUV emission SFR indicator suggests that the most likely cause of the discrepancy is the theoretical FUV-SFR calibration from stellar evolutionary libraries and/or stellar atmospheric models. We present an empirical calibration of the FUV-based SFR relation for dwarf galaxies, with uncertainties, which is ˜53% larger than previous relations. These results have signficant implications for measuring FUV-based SFRs of high-redshift galaxies.

  15. EARLY-TYPE GALAXIES AT z = 1.3. I. THE LYNX SUPERCLUSTER: CLUSTER AND GROUPS AT z = 1.3. MORPHOLOGY AND COLOR-MAGNITUDE RELATION

    Energy Technology Data Exchange (ETDEWEB)

    Mei, Simona; Raichoor, Anand; Huertas-Company, Marc [GEPI, Observatoire de Paris, Section de Meudon, 5 Place J. Janssen, 92190 Meudon Cedex (France); Adam Stanford, S.; Rettura, Alessandro; Jee, Myungkook J. [Department of Physics, University of California, Davis, CA 95616 (United States); Holden, Brad P.; Illingworth, Garth D. [UCO/Lick Observatories, University of California, Santa Cruz, CA 95065 (United States); Postman, Marc [Space Telescope Science Institute, Baltimore, MD (United States); Nakata, Fumiaki; Kodama, Tadayuki [Subaru Telescope, National Astronomical Observatory of Japan, 650 North A' ohoku Place, Hilo, HI 96720 (United States); Finoguenov, Alexis [Max-Planck-Instituet fuer Extraterrestrische Physik, Giessenbachstrasse, D-85478 Garching (Germany); Ford, Holland C. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Rosati, Piero [European South Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei Munchen (Germany); Tanaka, Masayuki; Koyama, Yusei [Institute for the Physics and Mathematics of the Universe, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8583 (Japan); Shankar, Francesco [Max-Planck-Instituet fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany); Carrasco, Eleazar R. [Gemini Observatory, Southern Operations Center, Casilla 603, La Serena (Chile); Demarco, Ricardo [Department of Astronomy, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile); Eisenhardt, Peter [Jet Propulsion Laboratory, California Institute of Technology, MS 169-327, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); and others

    2012-08-01

    We confirm the detection of three groups in the Lynx supercluster, at z Almost-Equal-To 1.3, through spectroscopic follow-up and X-ray imaging, and we give estimates for their redshifts and masses. We study the properties of the group galaxies compared to the two central clusters, RX J0849+4452 and RX J0848+4453. Using spectroscopic follow-up and multi-wavelength photometric redshifts, we select 89 galaxies in the clusters, of which 41 are spectroscopically confirmed, and 74 galaxies in the groups, of which 25 are spectroscopically confirmed. We morphologically classify galaxies by visual inspection, noting that our early-type galaxy (ETG) sample would have been contaminated at the 30%-40% level by simple automated classification methods (e.g., based on Sersic index). In luminosity-selected samples, both clusters and groups show high fractions of bulge-dominated galaxies with a diffuse component that we visually identified as a disk and which we classified as bulge-dominated spirals, e.g., Sas. The ETG fractions never rise above Almost-Equal-To 50% in the clusters, which is low compared to the fractions observed in other massive clusters at z Almost-Equal-To 1. In the groups, ETG fractions never exceed Almost-Equal-To 25%. However, overall bulge-dominated galaxy fractions (ETG plus Sas) are similar to those observed for ETGs in clusters at z {approx} 1. Bulge-dominated galaxies visually classified as spirals might also be ETGs with tidal features or merger remnants. They are mainly red and passive, and span a large range in luminosity. Their star formation seems to have been quenched before experiencing a morphological transformation. Because their fraction is smaller at lower redshifts, they might be the spiral population that evolves into ETGs. For mass-selected samples of galaxies with masses M > 10{sup 10.6} M{sub Sun} within {Sigma} > 500 Mpc{sup -2}, the ETG and overall bulge-dominated galaxy fractions show no significant evolution with respect to local

  16. Hubble Space Telescope Proper Motions along the Sagittarius Stream. I. Observations and Results for Stars in Four Fields

    Science.gov (United States)

    Sohn, Sangmo Tony; van der Marel, Roeland P.; Carlin, Jeffrey L.; Majewski, Steven R.; Kallivayalil, Nitya; Law, David R.; Anderson, Jay; Siegel, Michael H.

    2015-04-01

    We present a multi-epoch Hubble Space Telescope (HST) study of stellar proper motions (PMs) for four fields spanning 200° along the Sagittarius (Sgr) stream: one trailing arm field, one field near the Sgr dwarf spheroidal tidal radius, and two leading arm fields. We determine absolute PMs of dozens of individual stars per field, using established techniques that use distant background galaxies as the stationary reference frame. Stream stars are identified based on combined color-magnitude diagram and PM information. The results are broadly consistent with the few existing PM measurements for the Sgr galaxy and the trailing arm. However, our new results provide the highest PM accuracy for the stream to date, the first PM measurements for the leading arm, and the first PM measurements for individual stream stars; we also serendipitously determine the PM of the globular cluster NGC 6652. In the trailing-arm field, the individual PMs allow us to kinematically separate trailing-arm stars from leading-arm stars that are 360° further ahead in their orbit. Also, in three of our fields we find indications that two distinct kinematical components may exist within the same arm and wrap of the stream. Qualitative comparison of the HST data to the predictions of the Law & Majewski and Peñarrubia et al. N-body models show that the PM measurements closely follow the predicted trend with Sgr longitude. This provides a successful consistency check on the PM measurements, as well as on these N-body approaches (which were not tailored to fit any PM data).

  17. The optical gravitational lensing experiment. Variable stars in globular clusters. IV. Fields 104A-E in 47 Tucanae

    Science.gov (United States)

    Kaluzny, J.; Kubiak, M.; Szymanski, M.; Udalski, A.; Krzeminski, W.; Mateo, M.; Stanek, K. Z.

    1998-02-01

    Five fields located close to the center of the globular cluster NGC 104=47 Tuc were surveyed in a search for variable stars. We present V-band light curves for 42 variables. This sample includes 13 RR Lyr stars - 12 of them belong to the Small Magellanic Cloud (SMC) and 1 is a background object from the galactic halo. Twelve eclipsing binaries were identified - 9 contact systems and 3 detached/semi-detached systems. Seven eclipsing binaries are located in the blue straggler region on the cluster color-magnitude diagram (CMD) and four binaries can be considered main-sequence systems. One binary is probably a member of the SMC. Eight contact binaries are likely members of the cluster and one is most probably a foreground star. We show that for the surveyed region of 47 Tuc, the relative frequency of contact binaries is very low as compared with other recently surveyed globular clusters. The sample of identified variables also includes 15 red variables with periods ranging from about 2 days to several weeks. A large fraction of these 15 variables probably belong to the SMC but a few stars are likely to be red giants in 47 Tuc. VI photometry for about 50 000 stars from the cluster fields was obtained as a by product of our survey The photometric data presented in this paper are available in electronic form at the CDS, via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html}. Based on observations collected at the Las Campanas Observatory of the Carnegie Institution of Washington.

  18. STAR FORMATION ACTIVITY IN THE GALACTIC H II REGION Sh2-297

    Energy Technology Data Exchange (ETDEWEB)

    Mallick, K. K.; Ojha, D. K.; Dewangan, L. K. [Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai (Bombay) 400005 (India); Samal, M. R. [Laboratoire d' Astrophysique de Marseille (UMR 6110 CNRS and Universite de Provence), 38 rue F. Joliot-Curie, F-13388 Marseille Cedex 13 (France); Pandey, A. K. [Aryabhatta Research Institute of Observational Sciences, Manora Peak, Nainital 263129 (India); Bhatt, B. C. [Indian Institute of Astrophysics, Koramangala, Bangalore 560034 (India); Ghosh, S. K. [National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune 411007 (India); Tamura, M., E-mail: kshitiz@tifr.res.in [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)

    2012-11-01

    We present a multiwavelength study of the Galactic H II region Sh2-297, located in the Canis Major OB1 complex. Optical spectroscopic observations are used to constrain the spectral type of ionizing star HD 53623 as B0V. The classical nature of this H II region is affirmed by the low values of electron density and emission measure, which are calculated to be 756 cm{sup -3} and 9.15 Multiplication-Sign 10{sup 5} cm{sup -6} pc using the radio continuum observations at 610 and 1280 MHz, and Very Large Array archival data at 1420 MHz. To understand local star formation, we identified the young stellar object (YSO) candidates in a region of area {approx}7.'5 Multiplication-Sign 7.'5 centered on Sh2-297 using grism slitless spectroscopy (to identify the H{alpha} emission line stars), and near infrared (NIR) observations. NIR YSO candidates are further classified into various evolutionary stages using color-color and color-magnitude (CM) diagrams, giving 50 red sources (H - K > 0.6) and 26 Class II-like sources. The mass and age range of the YSOs are estimated to be {approx}0.1-2 M {sub Sun} and 0.5-2 Myr using optical (V/V-I) and NIR (J/J-H) CM diagrams. The mean age of the YSOs is found to be {approx}1 Myr, which is of the order of dynamical age of 1.07 Myr of the H II region. Using the estimated range of visual extinction (1.1-25 mag) from literature and NIR data for the region, spectral energy distribution models have been implemented for selected YSOs which show masses and ages to be consistent with estimated values. The spatial distribution of YSOs shows an evolutionary sequence, suggesting triggered star formation in the region. The star formation seems to have propagated from the ionizing star toward the cold dark cloud LDN1657A located west of Sh2-297.

  19. On the kinematic separation of field and cluster stars across the bulge globular NGC 6528

    Energy Technology Data Exchange (ETDEWEB)

    Lagioia, E. P.; Bono, G.; Buonanno, R. [Dipartimento di Fisica, Università degli Studi di Roma-Tor Vergata, via della Ricerca Scientifica 1, I-00133 Roma (Italy); Milone, A. P. [Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston, ACT 2611 (Australia); Stetson, P. B. [Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Prada Moroni, P. G. [Dipartimento di Fisica, Università di Pisa, I-56127 Pisa (Italy); Dall' Ora, M. [INAF-Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli (Italy); Aparicio, A.; Monelli, M. [Instituto de Astrofìsica de Canarias, E-38200 La Laguna, Tenerife, Canary Islands (Spain); Calamida, A.; Ferraro, I.; Iannicola, G. [INAF-Osservatorio Astronomico di Roma, Via Frascati 33, I-00044 Monte Porzio Catone (Italy); Gilmozzi, R. [European Southern Observatory, Karl-Schwarzschild-Straße 2, D-85748 Garching (Germany); Matsunaga, N. [Kiso Observatory, Institute of Astronomy, School of Science, The University of Tokyo, 10762-30, Mitake, Kiso-machi, Kiso-gun, 3 Nagano 97-0101 (Japan); Walker, A., E-mail: eplagioia@roma2.infn.it [Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603, La Serena (Chile)

    2014-02-10

    We present deep and precise multi-band photometry of the Galactic bulge globular cluster NGC 6528. The current data set includes optical and near-infrared images collected with ACS/WFC, WFC3/UVIS, and WFC3/IR on board the Hubble Space Telescope. The images cover a time interval of almost 10 yr, and we have been able to carry out a proper-motion separation between cluster and field stars. We performed a detailed comparison in the m {sub F814W}, m {sub F606W} – m {sub F814W} color-magnitude diagram with two empirical calibrators observed in the same bands. We found that NGC 6528 is coeval with and more metal-rich than 47 Tuc. Moreover, it appears older and more metal-poor than the super-metal-rich open cluster NGC 6791. The current evidence is supported by several diagnostics (red horizontal branch, red giant branch bump, shape of the sub-giant branch, slope of the main sequence) that are minimally affected by uncertainties in reddening and distance. We fit the optical observations with theoretical isochrones based on a scaled-solar chemical mixture and found an age of 11 ± 1 Gyr and an iron abundance slightly above solar ([Fe/H] = +0.20). The iron abundance and the old cluster age further support the recent spectroscopic findings suggesting a rapid chemical enrichment of the Galactic bulge.

  20. Astrophysical properties of star clusters in the Magellanic Clouds homogeneously estimated by ASteCA

    Science.gov (United States)

    Perren, G. I.; Piatti, A. E.; Vázquez, R. A.

    2017-06-01

    Aims: We seek to produce a homogeneous catalog of astrophysical parameters of 239 resolved star clusters, located in the Small and Large Magellanic Clouds, observed in the Washington photometric system. Methods: The cluster sample was processed with the recently introduced Automated Stellar Cluster Analysis (ASteCA) package, which ensures both an automatized and a fully reproducible treatment, together with a statistically based analysis of their fundamental parameters and associated uncertainties. The fundamental parameters determined for each cluster with this tool, via a color-magnitude diagram (CMD) analysis, are metallicity, age, reddening, distance modulus, and total mass. Results: We generated a homogeneous catalog of structural and fundamental parameters for the studied cluster sample and performed a detailed internal error analysis along with a thorough comparison with values taken from 26 published articles. We studied the distribution of cluster fundamental parameters in both Clouds and obtained their age-metallicity relationships. Conclusions: The ASteCA package can be applied to an unsupervised determination of fundamental cluster parameters, which is a task of increasing relevance as more data becomes available through upcoming surveys. A table with the estimated fundamental parameters for the 239 clusters analyzed is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/602/A89

  1. Spatial Distribution and Evolution of the Stellar Populations and Candidate Star Clusters in the Blue Compact Dwarf I Zwicky 18

    Science.gov (United States)

    Contreras Ramos, R.; Annibali, F.; Fiorentino, G.; Tosi, M.; Aloisi, A.; Clementini, G.; Marconi, M.; Musella, I.; Saha, A.; van der Marel, R. P.

    2011-10-01

    The evolutionary properties and spatial distribution of I Zwicky 18 (IZw18) stellar populations are analyzed by means of Hubble Space Telescope/Advanced Camera for Surveys deep and accurate photometry. A comparison of the resulting color-magnitude diagrams (CMDs) with stellar evolution models indicates that stars of all ages are present in all the system's components, including objects possibly up to 13 Gyr old, intermediate-age stars, and very young ones. The CMDs show evidence of thermally pulsing asymptotic giant branch and carbon stars. classical and ultra-long-period Cepheids as well as long-period variables have been measured. About 20 objects could be unresolved star clusters; these are mostly concentrated in the northwest (NW) portion of the main body (MB). If interpreted with simple stellar population models, these objects indicate a particularly active star formation over the past 100 Myr in IZw18. The stellar spatial distribution shows that the younger ones are more centrally concentrated, while old and intermediate-age stars are distributed homogeneously over the two bodies, although they are more easily detectable at the system's periphery. The oldest stars are most visible in the secondary body (SB) and in the southeast (SE) portion of the MB, where crowding is less severe, but are also present in the rest of the MB, where they are measured with larger uncertainties. The youngest stars are a few Myr old, are located predominantly in the MB, and are mostly concentrated in its NW portion. The SE portion of the MB appears to be in a similar, but not as young, evolutionary stage as the NW, while the SB stars are older than at least 10 Myr. There is then a sequence of decreasing age of the younger stars from the SB to the SE portion of the MB to the NW portion. All our results suggest that IZw18 is not atypical compared to other blue compact dwarfs. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science

  2. TRIGGERED STAR FORMATION IN A BRIGHT-RIMMED CLOUD (BRC 5) OF IC 1805

    Energy Technology Data Exchange (ETDEWEB)

    Fukuda, Naoya [Faculty of Biosphere-Geosphere Science, Okayama University of Science, 1-1 Ridai-chou, Okayama 700-0005 (Japan); Miao, Jingqi [Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury, Kent CT2 7NR (United Kingdom); Sugitani, Koji [Graduate School of Natural Sciences, Nagoya City University, Mizuho-ku, Nagoya 467-8501 (Japan); Kawahara, Kentaro [Faculty of Informatics, Okayama University of Science, 1-1 Ridai-chou, Okayama 700-0005 (Japan); Watanabe, Makoto [Department of Cosmosciences, Hokkaido University, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810 (Japan); Nakano, Makoto [Faculty of Education and Welfare Science, Oita University, Oita 870-1192 (Japan); Pickles, Andrew J., E-mail: fukudany@big.ous.ac.jp [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Goleta, CA 93117 (United States)

    2013-08-20

    We report recent optical, near-infrared (NIR), and millimeter observations which have revealed some new features of the bright-rimmed cloud BRC 5 associated with W4. With slitless spectroscopy, we detected 17 H{alpha} emission stars around the cloud; 4 are near the surface of the cloud, and 1 is toward IRAS 02252+6120. NIR photometry shows that the central H{alpha} emission star, together with one bright infrared source, has large NIR excesses and Class I spectral energy distributions. These two Class I objects are associated with the 2.9 mm continuum peaks and with a bipolar outflow, and are in between two separate, elongated C{sup 18}O(J = 1-0) cores. The C{sup 18}O cores and the two Class I sources are aligned along a line at position angle {approx}240 Degree-Sign , somewhat less than perpendicular to the direction of UV radiation from the OB stars. Most of the detected H{alpha} emission stars, all T Tauri candidates, are located within {approx}3' of the cloud on the exciting star side. An estimate of the age of the stars based on a color-magnitude diagram suggests that these T Tauri candidates have ages of {approx}1 Myr or less, but are more evolved objects than the central young stellar objects. This age sequence suggests sequential star formation within the BRC 5 cloud. The {sup 13}CO(J = 1-0) emission shows three elongated structures, which indicates the asymmetric structure toward the UV incident axis. We present our exploratory simulation results by using a smoothed particle hydrodynamic code that suggests that the asymmetrical BRC 5 structure could possibly result from the evolution of a preexisting prolate molecular cloud subject to radiation-driven implosion (RDI). Our best-fit prolate cloud has an initial mass of {approx}400 M{sub Sun }, an axial ratio of {approx}1.7, and a semi-major axis of {approx}1.6 pc, pointing away from the ionization flux by an angle of 15 Degree-Sign . The simulated cloud structure not only closely matches the observed

  3. New variable stars discovered in the fields of three Galactic open clusters using the VVV survey

    Science.gov (United States)

    Palma, T.; Minniti, D.; Dékány, I.; Clariá, J. J.; Alonso-García, J.; Gramajo, L. V.; Ramírez Alegría, S.; Bonatto, C.

    2016-11-01

    This project is a massive near-infrared (NIR) search for variable stars in highly reddened and obscured open cluster (OC) fields projected on regions of the Galactic bulge and disk. The search is performed using photometric NIR data in the J-, H- and Ks- bands obtained from the Vista Variables in the Vía Láctea (VVV) Survey. We performed in each cluster field a variability search using Stetson's variability statistics to select the variable candidates. Later, those candidates were subjected to a frequency analysis using the Generalized Lomb-Scargle and the Phase Dispersion Minimization algorithms. The number of independent observations range between 63 and 73. The newly discovered variables in this study, 157 in total in three different known OCs, are classified based on their light curve shapes, periods, amplitudes and their location in the corresponding color-magnitude (J -Ks ,Ks) and color-color (H -Ks , J - H) diagrams. We found 5 possible Cepheid stars which, based on the period-luminosity relation, are very likely type II Cepheids located behind the bulge. Among the newly discovered variables, there are eclipsing binaries, δ Scuti, as well as background RR Lyrae stars. Using the new version of the Wilson & Devinney code as well as the "Physics Of Eclipsing Binaries" (PHOEBE) code, we analyzed some of the best eclipsing binaries we discovered. Our results show that these studied systems turn out to be ranging from detached to double-contact binaries, with low eccentricities and high inclinations of approximately 80°. Their surface temperatures range between 3500 K and 8000 K.

  4. Finding High Quality Young Star Candidates in Ceph C using X-ray, Optical, and IR data

    Science.gov (United States)

    Orr, Laura; Rebull, Luisa M.; Johnson, Milton; Miller, Alexandra; Aragon Orozco, Anthony; Bakhaj, Benjamin; Bakshian, Jacquelyn; Chiffelle, Elizabeth; DeLint, Arie; Gerber, Stefan; Mader, Jared; Marengo, Amelia; McAdams, Jesse; Montufar, Cassandra; Orr, Quinton; San Emeterio, Lis; Stern, Eliyah; Weisserman, Drew

    2017-01-01

    We looked for new candidate young stars within the star forming region of Ceph OB3, more specifically in a region of this molecular cloud called Ceph C. While this region lies in the galactic plane and is included in several large surveys, Ceph C has not been well studied in the past and few young stellar objects (YSOs) have been identified there. The YSOVAR team (Rebull et al. 2014) has time-series monitoring data of this region, and in order to understand the diversity of the light curves, it is crucial to understand which objects in the field of view are likely YSOs, and which are foreground/background objects. The goal of our study is to identify candidate YSO sources as well as support the greater understanding of the variety, evolution, and variability of young stars. Our search for young stars includes data in X-ray, optical, and IR. Data points used are from Chandra, SDSS, IPHAS, 2MASS, Spitzer IRAC and MIPS, and WISE, giving us data over many orders of magnitude, 0.001 to 25 microns (0.36 to 25 microns without the X-rays). The catalogs were merged across all available wavelengths. Each source was inspected in all available images to insure good matches and quality of data across wavelengths and to eliminate poor candidates, those with contamination or confusion, and non-YSO objects. Spectral energy distributions (SEDs) for each candidate YSO were constructed and compared to images for greater assessment and reliable YSO identification. Color-color and color-magnitude diagrams have been created for the sources in this region and are used in conjunction with images, SEDs, X-ray, IR excess, and variability properties to identify candidate YSOs. Support provided for this work by the NASA/IPAC Teacher Archive Research Program (NITARP), which receives funding from the NASA ADP program.

  5. The Star Formation History of the Very Metal-poor Blue Compact Dwarf I Zw 18 from HST/ACS Data

    Science.gov (United States)

    Annibali, F.; Cignoni, M.; Tosi, M.; van der Marel, R. P.; Aloisi, A.; Clementini, G.; Contreras Ramos, R.; Fiorentino, G.; Marconi, M.; Musella, I.

    2013-12-01

    We have derived the star formation history (SFH) of the blue compact dwarf galaxy I Zw 18 through comparison of deep HST/ACS data with synthetic color-magnitude diagrams (CMDs). A statistical analysis was implemented for the identification of the best-fit SFH and relative uncertainties. We confirm that I Zw 18 is not a truly young galaxy, having started forming stars earlier than ~1 Gyr ago, and possibly at epochs as old as a Hubble time. In I Zw 18's main body we infer a lower limit of ≈2 × 106 M ⊙ for the mass locked up in old stars. I Zw 18's main body has been forming stars very actively during the last ~10 Myr, with an average star formation rate (SFR) as high as ≈1 M ⊙ yr-1 (or ≈2 × 10-5 M ⊙ yr-1 pc-2). On the other hand, the secondary body was much less active at these epochs, in agreement with the absence of significant nebular emission. The high current SFR can explain the very blue colors and the high ionized gas content in I Zw 18, resembling primeval galaxies in the early universe. Detailed chemical evolution models are required to quantitatively check whether the SFH from the synthetic CMDs can explain the low measured element abundances, or if galactic winds with loss of metals are needed. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., for NASA under contract NAS5-26555.

  6. THE STAR FORMATION HISTORY OF THE VERY METAL-POOR BLUE COMPACT DWARF I Zw 18 FROM HST/ACS DATA

    Energy Technology Data Exchange (ETDEWEB)

    Annibali, F.; Cignoni, M.; Tosi, M.; Clementini, G.; Contreras Ramos, R.; Fiorentino, G. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Van der Marel, R. P.; Aloisi, A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Marconi, M.; Musella, I., E-mail: francesca.annibali@oabo.inaf.it [INAF-Osservatorio Astronomico di Capodimonte, via Moiariello 16, I-80131 Napoli (Italy)

    2013-12-01

    We have derived the star formation history (SFH) of the blue compact dwarf galaxy I Zw 18 through comparison of deep HST/ACS data with synthetic color-magnitude diagrams (CMDs). A statistical analysis was implemented for the identification of the best-fit SFH and relative uncertainties. We confirm that I Zw 18 is not a truly young galaxy, having started forming stars earlier than ∼1 Gyr ago, and possibly at epochs as old as a Hubble time. In I Zw 18's main body we infer a lower limit of ≈2 × 10{sup 6} M {sub ☉} for the mass locked up in old stars. I Zw 18's main body has been forming stars very actively during the last ∼10 Myr, with an average star formation rate (SFR) as high as ≈1 M {sub ☉} yr{sup –1} (or ≈2 × 10{sup –5} M {sub ☉} yr{sup –1} pc{sup –2}). On the other hand, the secondary body was much less active at these epochs, in agreement with the absence of significant nebular emission. The high current SFR can explain the very blue colors and the high ionized gas content in I Zw 18, resembling primeval galaxies in the early universe. Detailed chemical evolution models are required to quantitatively check whether the SFH from the synthetic CMDs can explain the low measured element abundances, or if galactic winds with loss of metals are needed.

  7. Globular cluster photometry with the Hubble Space Telescope. 3: Blue stragglers and variable stars in the core of M3

    Science.gov (United States)

    Guhathakurta, Puragra; Yanny, Brian; Bahcall, John N.; Schneider, Donald P.

    1994-01-01

    This paper describes Hubble Space Telescope (HST)/Planetary Camera-I images of the core of the dense globular cluster M3 (NGC 5272). Stellar photometry in the F555W (V) and F785LP (I) bands, with a 1-sigma photometric accuracy of about 0.1 mag, has been used to construct color-magnitude diagrams of about 4700 stars above the main-sequence turnoff within r less than or approximately equal to 1 min of the cluster center. We have also analyzed archival HST F336W (U) images of M3 obtained by the Wide Field/Planetary Camera-I Instrument Definition Team. The UVI data are used to identify 28 blue straggler (BS) stars within the central 0.29 sq. arcmin. The specific frequency of BSs in this region of M3, N(sub BS)/N(sub V less than (V(HB)+2)) = 0.094 +/- 0.019, is about a factor of 2 - 3 higher than that found by Bolte et al. in a recent ground-based study of the same region, but comparable to that seen in the sparse outer parts of the same cluster and in HST observations of the core of the higher density cluster 47 Tuc. The BSs in M3 are slightly more centrally concentrated than red giant branch stars while horizontal branch stars are somewhat less concentrated red giants. The radial distribution of V-selected subgiant and turnoff stars is well fit by a King model with a core radius r(sub core) = 28 arcmin +/- 2 arcmin (90% confidence limits), which corresponds to 1.4 pc. Red giant and horizontal branch stars selected in the ultraviolet data (U less than 18) have a somewhat more compact distribution (r(sub core) = 22.5 arcmin). The HST U data consist of 17 exposures acquired over a span of three days. We have used these data to isolate 40 variable stars for which relative astrometry, brightnesses, colors, and light curves are presented. A Kolmogorov-Smirnov test indicates that, typically, the variability for each star is significant at the 95% level. We identify two variable BS candidates (probably of the SX Phe type), out of a sample of approximately 25 BSs in which

  8. Stars in the teaching of astrophysics at grammar schools.

    Science.gov (United States)

    Štefl, V.

    The paper subjects to theoretical analysis the topic "Stars" of the teaching programme of astrophysics at grammar schools. Diagrams express the relations among parameters of stars, sources of energy, structure and evolution of stars.

  9. Difference Decision Diagrams

    DEFF Research Database (Denmark)

    Moeller, Jesper; Lichtenberg, Jacob; Andersen, Henrik Reif

    1999-01-01

    This paper describes a new data structure, difference decision diagrams (DDDs), for representing a Boolean logic over inequalities of the form $x-y......This paper describes a new data structure, difference decision diagrams (DDDs), for representing a Boolean logic over inequalities of the form $x-y...

  10. The star formation histories of local group dwarf galaxies. I. Hubble space telescope/wide field planetary camera 2 observations

    Energy Technology Data Exchange (ETDEWEB)

    Weisz, Daniel R. [Department of Astronomy, University of California at Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Dolphin, Andrew E. [Raytheon Company, 1151 East Hermans Road, Tucson, AZ 85756 (United States); Skillman, Evan D. [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States); Holtzman, Jon [Department of Astronomy, New Mexico State University, Box 30001, 1320 Frenger Street, Las Cruces, NM 88003 (United States); Gilbert, Karoline M.; Dalcanton, Julianne J.; Williams, Benjamin F., E-mail: drw@ucsc.edu [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)

    2014-07-10

    We present uniformly measured star formation histories (SFHs) of 40 Local Group (LG) dwarf galaxies based on color-magnitude diagram (CMD) analysis from archival Hubble Space Telescope imaging. We demonstrate that accurate SFHs can be recovered from CMDs that do not reach the oldest main sequence turn-off (MSTO), but emphasize that the oldest MSTO is critical for precisely constraining the earliest epochs of star formation. We find that: (1) the average lifetime SFHs of dwarf spheroidals (dSphs) can be approximated by an exponentially declining SFH with τ ∼ 5 Gyr; (2) lower luminosity dSphs are less likely to have extended SFHs than more luminous dSphs; (3) the average SFHs of dwarf irregulars (dIrrs), transition dwarfs, and dwarf ellipticals can be approximated by the combination of an exponentially declining SFH (τ ∼ 3-4 Gyr) for lookback ages >10-12 Gyr ago and a constant SFH thereafter; (4) the observed fraction of stellar mass formed prior to z = 2 ranges considerably (80% for galaxies with M < 10{sup 5} M{sub ☉} to 30% for galaxies with M > 10{sup 7} M{sub ☉}) and is largely explained by environment; (5) the distinction between 'ultra-faint' and 'classical' dSphs is arbitrary; (6) LG dIrrs formed a significantly higher fraction of stellar mass prior to z = 2 than the Sloan Digital Sky Survey galaxies from Leitner and the SFHs from the abundance matching models of Behroozi et al. This may indicate higher than expected star formation efficiencies at early times in low mass galaxies. Finally, we provide all the SFHs in tabulated electronic format for use by the community.

  11. Automated search for Galactic star clusters in large multiband surveys. I. Discovery of 15 new open clusters in the Galactic anticenter region

    Science.gov (United States)

    Koposov, S. E.; Glushkova, E. V.; Zolotukhin, I. Yu.

    2008-08-01

    Aims: According to some estimations, there are as many as 100 000 open clusters in the Galaxy, but less than 2000 of them have been discovered, measured, and cataloged. We plan to undertake data mining of multiwavelength surveys to find new star clusters. Methods: We have developed a new method to search automatically for star clusters in very large stellar catalogs, which is based on convolution with density functions. We have applied this method to a subset of the Two Micron All Sky Survey catalog toward the Galactic anticenter. We also developed a method to verify whether detected stellar groups are real star clusters, which tests whether the stars that form the spatial density peak also fall onto a single isochrone in the color-magnitude diagram. By fitting an isochrone to the data, we estimate at the same time the main physical parameters of a cluster: age, distance, color excess. Results: For the present paper, we carried out a detailed analysis of 88 overdensity peaks detected in a field of 16×16 degrees near the Galactic anticenter. From this analysis, 15 overdensities were confirmed to be new open clusters and the physical and structural parameters were determined for 12 of them; 10 of them were previously suspected to be open clusters by Kronberger (2006) and Froebrich (2007). The properties were also determined for 13 yet-unstudied known open clusters, thus almost tripling the sample of open clusters with studied parameters in the anticenter. The parameters determined with this method showed a good agreement with published data for a set of well-known clusters. Figures 7-18 and Table 3 are only available in electronic form at http://www.aanda.org

  12. Star-Formation History of an Unmerged Fragment: the Leo A Dwarf Galaxy

    Science.gov (United States)

    Cole, Andrew

    2005-07-01

    The Leo A dwarf irregular is the only known Local Group galaxy that on the weight of current evidence has been suggested to have experienced its first star formation within the past 2-3 billion years. As a galaxy that could have been almost purely gaseous during the epoch of giant galaxy assembly, Leo A is the best nearby candidate to be a redshift zero analogue to the major building blocks of the Milky Way. We propose to obtain deep optical images of Leo A with the ACS/WFC to achieve three main goals: 1} To establish the fractions of star-formation, by mass, that occurred prior and subsequent to the main epoch of hierarchical merging {redshift z 2-4, Age 10-12.5 Gigayears}; 2} to measure the time variation in Leo A's star-formation rate over the past 10 Gyr, based on statistical analyses of its {V-I, I} color-magnitude diagram; and 3} to measure the radial distributions of young and old stellar populations and quantify the degree to which the optically prominent, young population is embedded in an extended, low-surface brightness sheet or halo of ancient stars. Because of the distance modulus {24.5 mag} and high degree of stellar crowding at the level of the oldest main-sequence turnoffs, the observations necessary to achieve these goals are unobtainable except with HST. The ONLY way to reliably derive the star-formation history of Leo A over its entire lifetime is with photometry to magnitudes of {B, I} = {28.6, 27.9}, the level of the oldest main-sequence turnoff in Leo A. These data would confirm and extend the limited inferences obtained from WFPC2 photometry over 2 magnitudes less deep, and provide the first opportunity to measure the complete star-formation history of a potential "living fossil" analogue to the building blocks of the Milky Way. We propose to use WFPC2 in parallel to measure radial variations in the stellar populations between the galaxy's core and outskirts. Because the expected 2-gyro jitter ellipse is comparable to the pixel scale of ACS

  13. Mapping the outer bulge with RRab stars from the VVV Survey

    Science.gov (United States)

    Gran, F.; Minniti, D.; Saito, R. K.; Zoccali, M.; Gonzalez, O. A.; Navarrete, C.; Catelan, M.; Contreras Ramos, R.; Elorrieta, F.; Eyheramendy, S.; Jordán, A.

    2016-07-01

    Context. The VISTA Variables in the Vía Láctea (VVV) is a near-IR time-domain survey of the Galactic bulge and southern plane. One of the main goals of this survey is to reveal the 3D structure of the Milky Way through their variable stars. In particular, enormous numbers of RR Lyrae stars have been discovered in the inner regions of the bulge (-8° ≲ b ≲ -1°) by optical surveys such as OGLE and MACHO, but leaving an unexplored window of more than ~47 sq deg (-10.0° ≲ ℓ ≲ + 10.7° and - 10.3° ≲ b ≲ -8.0°) observed by the VVV Survey. Aims: Our goal is to characterize the RR Lyrae stars in the outer bulge in terms of their periods, amplitudes, Fourier coefficients, and distances in order to evaluate the 3D structure of the bulge in this area. The distance distribution of RR Lyrae stars will be compared to that of red clump stars, which is known to trace a X-shaped structure, in order to determine whether these two different stellar populations share the same Galactic distribution. Methods: A search for RR Lyrae stars was performed in more than ~47 sq deg at low Galactic latitudes (-10.3° ≲ b ≲ -8.0°). In the procedure the χ2 value and analysis of variance (AoV) statistic methods were used to determine the variability and periodic features of the light curves, respectively. To prevent misclassifications, the analysis was performed only on the fundamental mode RR Lyrae stars (RRab) owing to similarities found in the near-IR light curve shapes of contact eclipsing binaries (W UMa) and first overtone RR Lyrae stars (RRc). On the other hand, the red clump stars of the same analyzed tiles were selected, and cuts in the color-magnitude diagram were applied and the maximum distance restricted to ~20 kpc in order to construct a similar catalog in terms of distances and covered area compared to the RR Lyrae stars. Results: We report the detection of more than 1000 RR Lyrae ab-type stars in the VVV Survey located in the outskirts of the Galactic bulge

  14. Feynman Diagrams for Beginners

    CERN Document Server

    Kumericki, Kresimir

    2016-01-01

    We give a short introduction to Feynman diagrams, with many exercises. Text is targeted at students who had little or no prior exposure to quantum field theory. We present condensed description of single-particle Dirac equation, free quantum fields and construction of Feynman amplitude using Feynman diagrams. As an example, we give a detailed calculation of cross-section for annihilation of electron and positron into a muon pair. We also show how such calculations are done with the aid of computer.

  15. Main-Sequence Star Populations in the Virgo Overdensity Region

    Science.gov (United States)

    Jerjen, H.; Da Costa, G. S.; Willman, B.; Tisserand, P.; Arimoto, N.; Okamoto, S.; Mateo, M.; Saviane, I.; Walsh, S.; Geha, M.; Jordán, A.; Olszewski, E.; Walker, M.; Zoccali, M.; Kroupa, P.

    2013-05-01

    We present deep color-magnitude diagrams (CMDs) for two Subaru Suprime-Cam fields in the Virgo Stellar Stream (VSS)/Virgo Overdensity (VOD) and compare them to a field centered on the highest concentration of Sagittarius (Sgr) Tidal Stream stars in the leading arm, Branch A of the bifurcation. A prominent population of main-sequence stars is detected in all three fields and can be traced as faint as g ≈ 24 mag. Using theoretical isochrone fitting, we derive an age of 9.1^{+1.0}_{-1.1} Gyr, a median abundance of [Fe/H] = -0.70^{+0.15}_{-0.20} dex, and a heliocentric distance of 30.9 ± 3.0 kpc for the main sequence of the Sgr Stream Branch A. The dominant main-sequence populations in the two VSS/VOD fields (Λ⊙ ≈ 265°, B ⊙ ≈ 13°) are located at a mean distance of 23.3 ± 1.6 kpc and have an age of ~8.2 Gyr, and an abundance of [Fe/H] = -0.67^{+0.16}_{-0.12} dex, similar to the Sgr Stream stars. These statistically robust parameters, derived from the photometry of 260 main-sequence stars, are also in good agreement with the age of the main population in the Sgr dwarf galaxy (8.0 ± 1.5 Gyr). They also agree with the peak in the metallicity distribution of 2-3 Gyr old M giants, [Fe/H] ≈-0.6 dex, in the Sgr north leading arm. We then compare the results from the VSS/VOD fields with the Sgr Tidal Stream model by Law & Majewski based on a triaxial Galactic halo shape that is empirically calibrated with Sloan Digital Sky Survey Sgr A-branch and Two Micron All Sky Survey M-giant stars. We find that the most prominent feature in the CMDs, the main-sequence population at 23 kpc, is not explained by the model. Instead the model predicts in these directions a low-density filamentary structure of Sgr debris stars at ~9 kpc and a slightly higher concentration of Sgr stars spread over a heliocentric distance range of 42-53 kpc. At best there is only marginal evidence for the presence of these populations in our data. Our findings then suggest that while there are

  16. Phosphatidylcholine: cholesterol phase diagrams.

    Science.gov (United States)

    Thewalt, J L; Bloom, M

    1992-10-01

    Two mono-cis-unsaturated phosphatidylcholine (PC) lipid molecules, having very different gel-liquid crystalline phase transition temperatures as a consequence of the relative positions of the double bond, exhibit PC:cholesterol phase diagrams that are very similar to each other and to that obtained previously for a fully saturated PC:cholesterol mixture (Vist, M. R., and J. H. Davis. 1990. Biochemistry 29:451-464). This leads to the conjecture that PC:cholesterol membrane phase diagrams have a universal form which is relatively independent of the precise chemical structure of the PC molecule. One feature of this phase diagram is the observation over a wide temperature range of a fluid but highly conformationally ordered phase at bilayer concentrations of more than approximately 25 mol% cholesterol. This ;liquid ordered' phase is postulated to be the relevant physical state for many biological membranes, such as the plasma membrane of eukaryotic cells, that contain substantial amounts of cholesterol or equivalent sterols.

  17. Dynamics and Stellar Content of the Giant Southern Stream in M31. I. Keck Spectroscopy of Red Giant Stars

    Science.gov (United States)

    Guhathakurta, Puragra; Rich, R. Michael; Reitzel, David B.; Cooper, Michael C.; Gilbert, Karoline M.; Majewski, Steven R.; Ostheimer, James C.; Geha, Marla C.; Johnston, Kathryn V.; Patterson, Richard J.

    2006-05-01

    of the M31 RGB stars are generally consistent with photometric estimates of their metallicity (derived by fitting RGB fiducials in the color-magnitude diagram). There is indirect evidence of a population of intermediate-age stars in the stream. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  18. Equational binary decision diagrams

    NARCIS (Netherlands)

    J.F. Groote (Jan Friso); J.C. van de Pol (Jaco)

    2000-01-01

    textabstractWe incorporate equations in binary decision diagrams (BDD). The resulting objects are called EQ-BDDs. A straightforward notion of ordered EQ-BDDs (EQ-OBDD) is defined, and it is proved that each EQ-BDD is logically equivalent to an EQ-OBDD. Moreover, on EQ-OBDDs satisfiability and

  19. Simulation Activity Diagrams

    OpenAIRE

    Ryan, John; Heavey, Cathal

    2003-01-01

    This paper presents a technique, Simulation Activity Diagrams (SAD), developed to lessen the modelling burden during the initial requirements gathering phases of a simulation project. The technique also allows the capture and visual communication of detailed information, to manufacturing personnel, which may otherwise be lost in detailed programming code.

  20. Compressing Binary Decision Diagrams

    DEFF Research Database (Denmark)

    Rune Hansen, Esben; Srinivasa Rao, S.; Tiedemann, Peter

    The paper introduces a new technique for compressing Binary Decision Diagrams in those cases where random access is not required. Using this technique, compression and decompression can be done in linear time in the size of the BDD and compression will in many cases reduce the size of the BDD to 1......-2 bits per node. Empirical results for our compression technique are presented, including comparisons with previously introduced techniques, showing that the new technique dominate on all tested instances....

  1. Compressing Binary Decision Diagrams

    DEFF Research Database (Denmark)

    Hansen, Esben Rune; Satti, Srinivasa Rao; Tiedemann, Peter

    2008-01-01

    The paper introduces a new technique for compressing Binary Decision Diagrams in those cases where random access is not required. Using this technique, compression and decompression can be done in linear time in the size of the BDD and compression will in many cases reduce the size of the BDD to 1......-2 bits per node. Empirical results for our compression technique are presented, including comparisons with previously introduced techniques, showing that the new technique dominate on all tested instances...

  2. Diagrams in creativity

    DEFF Research Database (Denmark)

    Hermund, Anders

    2017-01-01

    the outcome of a given artistic situation, with the intent to approach the essential needs in artistic creation. The specific diagrammatic methodology is fundamentally inspired by and further elaborated from C. S. Peirce’s semiotic system consisting of interrelated signs, wherein the diagram holds a very...... special position in the semiotic reasoning process. Viewing the creation of art pieces through the specific diagrammatic approach, indicates that, in the given case, it can be possible to organize the process of creation according to a diagrammatic system, and that this system is flexible enough to allow...

  3. STAR FORMATION AND YOUNG STELLAR CONTENT IN THE W3 GIANT MOLECULAR CLOUD

    Energy Technology Data Exchange (ETDEWEB)

    Rivera-Ingraham, Alana [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada); Martin, Peter G. [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada); Polychroni, Danae [INAF-IFSI, via Fosso del Cavaliere 100, 00133 Roma (Italy); Moore, Toby J. T. [Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD (United Kingdom)

    2011-12-10

    In this work, we have carried out an in-depth analysis of the young stellar content in the W3 giant molecular cloud (GMC). The young stellar object (YSO) population was identified and classified in the Infrared Array Camera/Multiband Imaging Photometer color-magnitude space according to the 'Class' scheme and compared to other classifications based on intrinsic properties. Class 0/I and II candidates were also compared to low-/intermediate-mass pre-main-sequence (PMS) stars selected through their colors and magnitudes in the Two Micron All Sky Survey. We find that a reliable color/magnitude selection of low-mass PMS stars in the infrared requires prior knowledge of the protostar population, while intermediate-mass objects can be more reliably identified. By means of the minimum spanning tree algorithm and our YSO spatial distribution and age maps, we investigated the YSO groups and the star formation history in W3. We find signatures of clustered and distributed star formation in both triggered and quiescent environments. The central/western parts of the GMC are dominated by large-scale turbulence likely powered by isolated bursts of star formation that triggered secondary star formation events. Star formation in the eastern high-density layer (HDL) also shows signs of quiescent and triggered stellar activity, as well as extended periods of star formation. While our findings support triggering as a key factor for inducing and enhancing some of the major star-forming activity in the HDL (e.g., W3 Main/W3(OH)), we argue that some degree of quiescent or spontaneous star formation is required to explain the observed YSO population. Our results also support previous studies claiming a spontaneous origin for the isolated massive star(s) powering KR 140.

  4. Markov Influence Diagrams.

    Science.gov (United States)

    Díez, Francisco J; Yebra, Mar; Bermejo, Iñigo; Palacios-Alonso, Miguel A; Calleja, Manuel Arias; Luque, Manuel; Pérez-Martín, Jorge

    2017-02-01

    Markov influence diagrams (MIDs) are a new type of probabilistic graphical model that extends influence diagrams in the same way that Markov decision trees extend decision trees. They have been designed to build state-transition models, mainly in medicine, and perform cost-effectiveness analyses. Using a causal graph that may contain several variables per cycle, MIDs can model various patient characteristics without multiplying the number of states; in particular, they can represent the history of the patient without using tunnel states. OpenMarkov, an open-source tool, allows the decision analyst to build and evaluate MIDs-including cost-effectiveness analysis and several types of deterministic and probabilistic sensitivity analysis-with a graphical user interface, without writing any code. This way, MIDs can be used to easily build and evaluate complex models whose implementation as spreadsheets or decision trees would be cumbersome or unfeasible in practice. Furthermore, many problems that previously required discrete event simulation can be solved with MIDs; i.e., within the paradigm of state-transition models, in which many health economists feel more comfortable.

  5. Program Synthesizes UML Sequence Diagrams

    Science.gov (United States)

    Barry, Matthew R.; Osborne, Richard N.

    2006-01-01

    A computer program called "Rational Sequence" generates Universal Modeling Language (UML) sequence diagrams of a target Java program running on a Java virtual machine (JVM). Rational Sequence thereby performs a reverse engineering function that aids in the design documentation of the target Java program. Whereas previously, the construction of sequence diagrams was a tedious manual process, Rational Sequence generates UML sequence diagrams automatically from the running Java code.

  6. Engineering Holographic Superconductor Phase Diagrams

    OpenAIRE

    Chen, Jiunn-Wei; Dai, Shou-Huang; Maity, Debaprasad; Zhang, Yun-Long

    2016-01-01

    We study how to engineer holographic models with features of a high temperature superconductor phase diagram. We introduce a field in the bulk which provides a tunable "doping" parameter in the boundary theory. By designing how this field changes the effective masses of other order parameter fields, desired phase diagrams can be engineered. We give examples of generating phase diagrams with phase boundaries similar to a superconducting dome and an anti-ferromagnetic phase by including two ord...

  7. The Small Magellanic Cloud Investigation of Dust and Gas Evolution (SMIDGE): The Dust Extinction Curve from Red Clump Stars

    Science.gov (United States)

    Yanchulova Merica-Jones, Petia; Sandstrom, Karin M.; Johnson, L. Clifton; Dalcanton, Julianne; Dolphin, Andrew E.; Gordon, Karl; Roman-Duval, Julia; Weisz, Daniel R.; Williams, Benjamin F.

    2017-10-01

    We use Hubble Space Telescope (HST) observations of red clump stars taken as part of the Small Magellanic Cloud Investigation of Dust and Gas Evolution (SMIDGE) program to measure the average dust extinction curve in a ˜200 pc × 100 pc region in the southwest bar of the Small Magellanic Cloud (SMC). The rich information provided by our eight-band ultraviolet through near-infrared photometry allows us to model the color-magnitude diagram of the red clump accounting for the extinction curve shape, a log-normal distribution of A V , and the depth of the stellar distribution along the line of sight. We measure an extinction curve with {R}475 ={A}475/({A}475{--}{A}814)=2.65+/- 0.11. This measurement is significantly larger than the equivalent values of published Milky Way (MW) R V = 3.1 ({R}475=1.83) and SMC Bar R V = 2.74 ({R}475=1.86) extinction curves. Similar extinction curve offsets in the Large Magellanic Cloud (LMC) have been interpreted as the effect of large dust grains. We demonstrate that the line-of-sight depth of the SMC (and LMC) introduces an apparent “gray” contribution to the extinction curve inferred from the morphology of the red clump. We show that no gray dust component is needed to explain extinction curve measurements when FWHM depth of 10 ± 2 kpc in the stellar distribution of the SMC (5 ± 1 kpc for the LMC) is considered, which agrees with recent studies of Magellanic Cloud stellar structure. The results of our work demonstrate the power of broadband HST imaging for simultaneously constraining dust and galactic structure outside the MW.

  8. Comparing M31 and Milky Way satellites: The extended star formation histories of Andromeda II and Andromeda XVI

    Energy Technology Data Exchange (ETDEWEB)

    Weisz, Daniel R. [Department of Astronomy, University of California at Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Skillman, Evan D.; McQuinn, Kristen B. W. [Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN (United States); Hidalgo, Sebastian L.; Monelli, Matteo; Gallart, Carme; Aparicio, Antonio [Instituto de Astrofísica de Canarias. Vía Láctea s/n., E-38200 La Laguna, Tenerife, Canary Islands (Spain); Dolphin, Andrew E. [Raytheon, 1151 E. Hermans Road, Tucson, AZ 85706 (United States); McConnachie, Alan; Stetson, Peter B. [Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Bernard, Edouard J. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Boylan-Kolchin, Michael [Astronomy Department, University of Maryland, College Park, MD (United States); Cassisi, Santi [INAF-Osservatorio Astronomico di Collurania, Teramo (Italy); Cole, Andrew A. [School of Mathematics and Physics, University of Tasmania, Hobart, Tasmania (Australia); Ferguson, Henry C. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Irwin, Mike [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Martin, Nicolas F. [Observatoire astronomique de Strasbourg, Universit de Strasbourg, CNRS, UMR 7550, 11 rue de l' Universit, F-67000 Strasbourg (France); Mayer, Lucio [Institut für Theoretische Physik, University of Zurich, Zürich (Switzerland); Navarro, Julio F., E-mail: drw@ucsc.edu [Department of Physics and Astronomy, University of Victoria, BC V8P 5C2 (Canada)

    2014-07-01

    We present the first comparison between the lifetime star formation histories (SFHs) of M31 and Milky Way (MW) satellites. Using the Advanced Camera for Surveys on board the Hubble Space Telescope, we obtained deep optical imaging of Andromeda II (And II; M{sub V} = –12.0; log(M {sub *}/M {sub ☉}) ∼ 6.7) and Andromeda XVI (And XVI; M{sub V} = –7.5; log(M {sub *}/M {sub ☉}) ∼ 4.9) yielding color-magnitude diagrams that extend at least 1 mag below the oldest main-sequence turnoff, and are similar in quality to those available for the MW companions. And II and And XVI show strikingly similar SFHs: both formed 50%-70% of their total stellar mass between 12.5 and 5 Gyr ago (z ∼ 5-0.5) and both were abruptly quenched ∼5 Gyr ago (z ∼ 0.5). The predominance of intermediate age populations in And XVI makes it qualitatively different from faint companions of the MW and clearly not a pre-reionization fossil. Neither And II nor And XVI appears to have a clear analog among MW companions, and the degree of similarity in the SFHs of And II and And XVI is not seen among comparably faint-luminous pairs of MW satellites. These findings provide hints that satellite galaxy evolution may vary substantially among hosts of similar stellar mass. Although comparably deep observations of more M31 satellites are needed to further explore this hypothesis, our results underline the need for caution when interpreting satellite galaxies of an individual system in a broader cosmological context.

  9. Transformations of triangle ladder diagrams

    Science.gov (United States)

    Kondrashuk, Igor; Vergara, Alvaro

    2010-03-01

    It is shown how dual space diagrammatic representation of momentum integrals corresponding to triangle ladder diagrams with an arbitrary number of rungs can be transformed to half-diamonds. In paper arXiv:0803.3420 [hep-th] the half-diamonds were related by conformal integral substitution to the diamonds which represent the dual space image of four-point ladder integrals in the four-dimensional momentum space. Acting in the way described in the present paper we do not need to use the known result for diamond (four-point) diagrams as an external input in deriving relations of arXiv:0803.3420 [hep-th], however, that result for the diamond diagram arises in the present proof as an intermediate consequence in a step-by-step diagrammatic transformation from the triangle ladder diagram to the half-diamond diagrams.

  10. Rectangular diagrams of surfaces: representability

    Science.gov (United States)

    Dynnikov, I. A.; Prasolov, M. V.

    2017-06-01

    Introduced here is a simple combinatorial way, which is called a rectangular diagram of a surface, to represent a surface in the three-sphere. It has a particularly nice relation to the standard contact structure on S^3 and to rectangular diagrams of links. By using rectangular diagrams of surfaces it is intended, in particular, to develop a method to distinguish Legendrian knots. This requires a lot of technical work of which the present paper addresses only the first basic question: which isotopy classes of surfaces can be represented by a rectangular diagram? Roughly speaking, the answer is this: there is no restriction on the isotopy class of the surface, but there is a restriction on the rectangular diagram of the boundary link arising from the presentation of the surface. The result extends to Giroux's convex surfaces for which this restriction on the boundary has a natural meaning. In a subsequent paper, transformations of rectangular diagrams of surfaces will be considered and their properties will be studied. By using the formalism of rectangular diagrams of surfaces an annulus in S^3 is produced here that is expected to be a counterexample to the following conjecture: if two Legendrian knots cobound an annulus and have zero Thurston-Bennequin numbers relative to this annulus, then they are Legendrian isotopic. Bibliography: 30 titles.

  11. The hot γ Doradus and Maia stars

    Science.gov (United States)

    Balona, L. A.; Engelbrecht, C. A.; Joshi, Y. C.; Joshi, S.; Sharma, K.; Semenko, E.; Pandey, G.; Chakradhari, N. K.; Mkrtichian, David; Hema, B. P.; Nemec, J. M.

    2016-08-01

    The hot γ Doradus stars have multiple low frequencies characteristic of γ Dor or SPB variables, but are located between the red edge of the SPB and the blue edge of the γ Dor instability strips where all low-frequency modes are stable in current models of these stars. Though δ Sct stars also have low frequencies, there is no sign of high frequencies in hot γ Dor stars. We obtained spectra to refine the locations of some of these stars in the H-R diagram and conclude that these are, indeed, anomalous pulsating stars. The Maia variables have multiple high frequencies characteristic of β Cep and δ Sct stars, but lie between the red edge of the β Cep and the blue edge of the δ Sct instability strips. We compile a list of all Maia candidates and obtain spectra of two of these stars. Again, it seems likely that these are anomalous pulsating stars which are currently not understood.

  12. The Genesis of Feynman Diagrams

    CERN Document Server

    Wuthrich, Adrian

    2011-01-01

    In a detailed reconstruction of the genesis of Feynman diagrams the author reveals that their development was constantly driven by the attempt to resolve fundamental problems concerning the uninterpretable infinities that arose in quantum as well as classical theories of electrodynamic phenomena. Accordingly, as a comparison with the graphical representations that were in use before Feynman diagrams shows, the resulting theory of quantum electrodynamics, featuring Feynman diagrams, differed significantly from earlier versions of the theory in the way in which the relevant phenomena were concep

  13. A DISCUSSION ON THE CLASSIFICATION AND EVOLUTION OF SYMBIOTIC STARS

    NARCIS (Netherlands)

    SEAL, P

    1990-01-01

    A H-R diagram is drawn from the bolometric luminosities and effective temperatures of 24 symbiotic stars and compared with theoretical evolutionary tracks of Population I metal-rich stars. It is shown that the S-type and D-type symbiotic stars are classified very clearly in course of their evolution

  14. Bayesian Networks and Influence Diagrams

    DEFF Research Database (Denmark)

    Kjærulff, Uffe Bro; Madsen, Anders Læsø

     Probabilistic networks, also known as Bayesian networks and influence diagrams, have become one of the most promising technologies in the area of applied artificial intelligence, offering intuitive, efficient, and reliable methods for diagnosis, prediction, decision making, classification...

  15. Second report on sintering diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Swinkels, F.B.; Ashby, M.F.

    1980-04-01

    Sintering-mechanism diagrams are diagrams with axes of neck-size or density, and temperature, which identify the fields of dominance of each of the several mechanisms which contribute to sintering, and show the rate or extent of sintering that all the mechanisms, acting together, produce. The present paper incorporates certain new ideas about sintering into the diagrams: the coupling of boundary diffusion and surface diffusion; new criteria for the stages of sintering; and an approximate treatment of particle rearrangement. Diagrams showing how both the neck size and the density of compacts of wires and of spheres change with time and temperature are developed. Their use is illustrated by an analysis of a large body of sintering data for both wires and spheres of Ag, Cu, Ni, Fe, W, NaCl and Stainless Steel.

  16. Wind Diagrams in Medieval Iceland

    DEFF Research Database (Denmark)

    Kedwards, Dale

    2014-01-01

    This article presents a study of the sole wind diagram that survives from medieval Iceland, preserved in the encyclopaedic miscellany in Copenhagen's Arnamagnæan Institute with the shelf mark AM 732b 4to (c. 1300-25). It examines the wind diagram and its accompanying text, an excerpt on the winds...... from Isidore of Seville's Etymologies. It also examines the perimeter of winds on two medieval Icelandic world maps, and the visual traditions from which they draw....

  17. Dwarf Galaxies in the Local Group

    NARCIS (Netherlands)

    Tolstoy, Eline; Bruzual, GA; Charlot, S

    2010-01-01

    Within the Local Universe galaxies can be studied in great detail star by star. The Color-Magnitude Diagram synthesis analysis method is well established as the most accurate way to determine the detailed star formation history of galaxies going back to the earliest times. This approach received a

  18. Model Dust Envelopes for Asymptotic Giant Branch Stars. Carbon Stars. II. Carbon Stars

    Directory of Open Access Journals (Sweden)

    Kyung-Won Suh

    1995-12-01

    Full Text Available We have modeled the dust envelopes around carbon stars with close attention to the evolution of the structure of the dust shells. We use various dust density distributions to take account the effect of the superwind due to the helium shell flash by adding a density increased region. Depending on the position and quality of the density increased region, the model results are different from the results with conventional density distribution. The new results fit the observations of some carbon stars better. The IR two-color diagrams comparing the results of the super wind models and IRAS observation of 252 carbon stars have been made. The new results can explain much wider regions on the IR two-color diagrams.

  19. Improving modeling with layered UML diagrams

    DEFF Research Database (Denmark)

    Störrle, Harald

    2013-01-01

    Layered diagrams are diagrams whose elements are organized into sets of layers. Layered diagrams are routinely used in many branches of engineering, except Software Engineering. In this paper, we propose to add layered diagrams to UML modeling tools, and elaborate the concept by exploring usage...

  20. Multi-currency Influence Diagrams

    DEFF Research Database (Denmark)

    Nielsen, Søren Holbech; Nielsen, Thomas Dyhre; Jensen, Finn V.

    2007-01-01

    When using the influence diagrams framework for solving a decision problem with several different quantitative utilities, the traditional approach has been to convert the utilities into one common currency. This conversion is carried out using a tacit transformation, under the assumption that the......When using the influence diagrams framework for solving a decision problem with several different quantitative utilities, the traditional approach has been to convert the utilities into one common currency. This conversion is carried out using a tacit transformation, under the assumption...... that the converted problem is equivalent to the original one. In this paper we present an extension of the influence diagram framework. The extension allows for these decision problems to be modelled in their original form. We present an algorithm that, given a linear conversion function between the currencies...

  1. Which of Kepler's Stars Flare?

    Science.gov (United States)

    Kohler, Susanna

    2017-12-01

    The habitability of distant exoplanets is dependent upon many factors one of which is the activity of their host stars. To learn about which stars are most likely to flare, a recent study examines tens of thousands of stellar flares observed by Kepler.Need for a Broader SampleArtists rendering of a flaring dwarf star. [NASAs Goddard Space Flight Center/S. Wiessinger]Most of our understanding of what causes a star to flare is based on observations of the only star near enough to examine in detail the Sun. But in learning from a sample size of one, a challenge arises: we must determine which conclusions are unique to the Sun (or Sun-like stars), and which apply to other stellar types as well.Based on observations and modeling, astronomers think that stellar flares result from the reconnection of magnetic field lines in a stars outer atmosphere, the corona. The magnetic activity is thought to be driven by a dynamo caused by motions in the stars convective zone.HR diagram of the Kepler stars, with flaring main-sequence (yellow), giant (red) and A-star (green) stars in the authors sample indicated. [Van Doorsselaere et al. 2017]To test whether these ideas are true generally, we need to understand what types of stars exhibit flares, and what stellar properties correlate with flaring activity. A team of scientists led by Tom Van Doorsselaere (KU Leuven, Belgium) has now used an enormous sample of flares observed by Kepler to explore these statistics.Intriguing TrendsVan Doorsselaere and collaborators used a new automated flare detection and characterization algorithm to search through the raw light curves from Quarter 15 of the Kepler mission, building a sample of 16,850 flares on 6,662 stars. They then used these to study the dependence of the flare occurrence rate, duration, energy, and amplitude on the stellar spectral type and rotation period.This large statistical study led the authors to several interesting conclusions, including:Flare star incidence rate as a a

  2. Phase diagrams and crystal growth

    Science.gov (United States)

    Venkrbec, Jan

    1980-04-01

    Phase diagrams are briefly treated as generalized property-composition relationships, with respect to crystal technology optimization. The treatment is based on mutual interaction of three systems related to semiconductors: (a) the semiconducting material systems, (b0 the data bank, (c) the system of crystallization methods. A model is proposed enabling optimatization on the path from application requirements to the desired material. Further, several examples of the selection as to the composition of LED and laser diode material are given. Some of molten-solution-zone methods are being successfully introduced for this purpose. Common features of these methods, the application of phase diagrams, and their pecularities compared with other crystallization methods are illustrated by schematic diagrams and by examples. LPE methods, particularly the steady-state LPE methods such as Woodall's ISM and Nishizawa's TDM-CVP, and the CAM-S (Crystallization Method Providing Composition Autocontrol in Situ) have been chosen as examples. Another approach of exploiting phase diagrams for optimal material selection and for determination of growth condition before experimentation through a simple calculation is presented on InP-GaP solid solutions. Ternary phase diagrams are visualized in space through calculation and constructions based on the corresponding thermodynamic models and anaglyphs. These make it easy to observe and qualitatively analyze the crystallization of every composition. Phase diagrams can be also used as a powerful tool for the deduction of new crystallization methods. Eutectic crystallization is an example of such an approach where a modified molten-solution-zone method can give a sandwich structure with an abrupt concentration change. The concentration of a component can range from 0 to 100% in the different solid phases.

  3. The diagram for phyllotactic series

    Directory of Open Access Journals (Sweden)

    Joanna Szymanowska-Pułka

    2014-01-01

    Full Text Available Many authors studying phyllotaxis in various plant species have reported the occurrence of many different numbers of contact parastichy pairs that are members of different Fibonacci-like series. On the basis of these reports a diagram was constructed in which any theoretically possible series was represented by the two first members of a given series.

  4. Phase diagram of Hertzian spheres

    NARCIS (Netherlands)

    Pàmies, J.C.; Cacciuto, A.; Frenkel, D.

    2009-01-01

    We report the phase diagram of interpenetrating Hertzian spheres. The Hertz potential is purely repulsive, bounded at zero separation, and decreases monotonically as a power law with exponent 5/2, vanishing at the overlapping threshold. This simple functional describes the elastic interaction of

  5. Phase diagrams for sonoluminescing bubbles

    NARCIS (Netherlands)

    Hilgenfeldt, Sascha; Lohse, Detlef; Brenner, Michael P.

    1996-01-01

    Sound driven gas bubbles in water can emit light pulses. This phenomenon is called sonoluminescence (SL). Two different phases of single bubble SL have been proposed: diffusively stable and diffusively unstable SL. We present phase diagrams in the gas concentration versus forcing pressure state

  6. Bayesian Networks and Influence Diagrams

    DEFF Research Database (Denmark)

    Kjærulff, Uffe Bro; Madsen, Anders Læsø

    Bayesian Networks and Influence Diagrams: A Guide to Construction and Analysis, Second Edition, provides a comprehensive guide for practitioners who wish to understand, construct, and analyze intelligent systems for decision support based on probabilistic networks. This new edition contains six new...

  7. Primordial main equence binary stars in the globular cluster M71

    Science.gov (United States)

    Yan, Lin; Mateo, Mario

    1994-01-01

    We report the identification of five short-period variables near the center of the metal-rich globular cluster M71. Our observations consist of multiepoch VI charge coupled device (CCD) images centered on the cluster and covering a 6.3 min x 6.3 min field. Four of these variables are contact eclipsing binaries with periods between 0.35 and 0.41 days; one is a detached or semidetached eclipsing binary with a period of 0.56 days. Two of the variables were first identified as possible eclipsing binaries in an earlier survey by Hodder et al. (1992). We have used a variety of arguments to conclude that all five binary stars are probable members of M71, a result that is consistent with the low number (0.15) of short-period field binaries expected along this line of sight. Based on a simple model of how contact binaries evolve from initially detached binaries, we have determined a lower limit of 1.3% on the frequency of primordial binaries in M71 with initial orbital periods in the range 2.5 - 5 days. This implies that the overall primordial binary frequency, f, is 22(sup +26)(sub -12)% assuming df/d log P = const ( the 'flat' distribution), or f = 57(sup +15)(sub -8)% for df/d log P = 0.032 log P + const as observed for G-dwarf binaries in the solar neighborhood (the 'sloped' distribution). Both estimates of f correspond to binaries with initial periods shorter than 800 yr since any longer-period binaries would have been disrupted over the lifetime of the cluster. Our short-period binary frequency is in excellent agreement with the observed frequency of red-giant binaries observed in globulars if we adopt the flat distribution. For the sloped distribution, our results significantly overestimate the number of red-giant binaries. All of the short-period M71 binaries lie within 1 mag of the luminosity of the cluster turnoff in the color-magnitude diagram despite the fact we should have easily detected similar eclipsing binaries 2 - 2.5 mag fainter than this. We discuss the

  8. Delta Scuti and related stars - Review

    Science.gov (United States)

    Breger, M.; Stockenhuber, H.

    Present knowledge on Delta Scuti stars, short-period pulsators of spectral types A and F situated on or above the main sequence, is reviewed. The topics discussed include: pulsation periods, pulsational mode-typing through line profiles, cluster stars, and SX Phe-type variables. The position of Delta Scuti stars in the H-R diagram is shown along with the observed period-luminosity-color relation for the stars. Correlations of average pulsation period and M(v) with cluster age are given, showing that the observed correlations can be explained by the PLC relation and main sequence evolution of the clusters.

  9. Stars and Star Myths.

    Science.gov (United States)

    Eason, Oliver

    Myths and tales from around the world about constellations and facts about stars in the constellations are presented. Most of the stories are from Greek and Roman mythology; however, a few Chinese, Japanese, Polynesian, Arabian, Jewish, and American Indian tales are also included. Following an introduction, myths are presented for the following 32…

  10. NIR properties of Be stars in star clusters in the Magellanic Clouds

    Science.gov (United States)

    Paul, K. T.; Subramaniam, Annapurni; Mathew, Blesson; Shruthi, S. B.

    2017-10-01

    Magellanic Clouds are the nearby galaxies which are ideal to study the properties of metal poor stellar population. In this study, we explore the near-IR properties of optically identified classical Be stars in 19 star clusters in the Magellanic Clouds. From an optically identified sample of 835 Be stars we obtained the J, H, K magnitudes of 389 stars from the IRSF MCPS catalog. Among these, 247 stars (36.4%) are found in 9 clusters in the Large Magellanic Cloud and 142 stars (55.5%) in 10 clusters in the Small Magellanic Cloud. After correcting for reddening, we studied their NIR properties in the (H - K)0 vs (J - H)0 diagram. We identified 14 stars with abnormally large near IR excesses, which were removed from the analysis, there by restricting our study to 355 classical Be stars. We propose an extended area in the near-IR (H - K)0 vs (J - H)0 diagram as the diagnostic location of Classical Be stars in the Magellanic Clouds. We identified 14 stars to have near-IR excess, higher than those seen in classical Be stars. From the analysis based on spectral energy distribution and luminosity estimate, we found that 8 candidate Be stars may be Herbig Ae/Be stars. We identified a new sample of 6 sgB[e] stars, which when added to the sparse existing sample of 15 sgB[e] stars in the Magellanic Clouds can provide insight to understand the evolutionary link between sgB[e] stars and Luminous Blue variables.

  11. Bayesian Networks and Influence Diagrams

    DEFF Research Database (Denmark)

    Kjærulff, Uffe Bro; Madsen, Anders Læsø

     Probabilistic networks, also known as Bayesian networks and influence diagrams, have become one of the most promising technologies in the area of applied artificial intelligence, offering intuitive, efficient, and reliable methods for diagnosis, prediction, decision making, classification......, and exercises are included for the reader to check his/her level of understanding. The techniques and methods presented for knowledge elicitation, model construction and verification, modeling techniques and tricks, learning models from data, and analyses of models have all been developed and refined......, troubleshooting, and data mining under uncertainty. Bayesian Networks and Influence Diagrams: A Guide to Construction and Analysis provides a comprehensive guide for practitioners who wish to understand, construct, and analyze intelligent systems for decision support based on probabilistic networks. Intended...

  12. Bayesian Networks and Influence Diagrams

    DEFF Research Database (Denmark)

    Kjærulff, Uffe Bro; Madsen, Anders Læsø

    , troubleshooting, and data mining under uncertainty. Bayesian Networks and Influence Diagrams: A Guide to Construction and Analysis provides a comprehensive guide for practitioners who wish to understand, construct, and analyze intelligent systems for decision support based on probabilistic networks. Intended...... Probabilistic networks, also known as Bayesian networks and influence diagrams, have become one of the most promising technologies in the area of applied artificial intelligence, offering intuitive, efficient, and reliable methods for diagnosis, prediction, decision making, classification......, and exercises are included for the reader to check his/her level of understanding. The techniques and methods presented for knowledge elicitation, model construction and verification, modeling techniques and tricks, learning models from data, and analyses of models have all been developed and refined...

  13. A Hubble Diagram for Quasars

    Directory of Open Access Journals (Sweden)

    Susanna Bisogni

    2018-01-01

    Full Text Available The cosmological model is at present not tested between the redshift of the farthest observed supernovae (z ~ 1.4 and that of the Cosmic Microwave Background (z ~ 1,100. Here we introduce a new method to measure the cosmological parameters: we show that quasars can be used as “standard candles” by employing the non-linear relation between their intrinsic UV and X-ray emission as an absolute distance indicator. We built a sample of ~1,900 quasars with available UV and X-ray observations, and produced a Hubble Diagram up to z ~ 5. The analysis of the quasar Hubble Diagram, when used in combination with supernovae, provides robust constraints on the matter and energy content in the cosmos. The application of this method to forthcoming, larger quasar samples, will also provide tight constraints on the dark energy equation of state and its possible evolution with time.

  14. Phase diagram of boron crystals

    Science.gov (United States)

    Shirai, Koun

    2017-05-01

    The current status of study on the phase diagram of boron is given from the theoretical viewpoint. Boron is the last elemental crystal whose phase diagram is missing. In the last decade, several new structures of boron allotropes were found, while some were disproven. Presently, even the number of allotropes of boron is uncertain. A simple reason for this is that there are many and complicated structures, and some are minimally different from the others. A theoretical study thus requires very high accuracy. The difficulty, however, is not merely a technical difficulty of computational scale. The physics involved is quite different from what is obtained by band theory, which is the most successful theory of solids. It is only recent that a fundamental problem of metal/insulator has been solved. We come to know that the interrelationships between nonstoichiometry, partially occupied sites, and the balance of intra/inter-icosahedral bonding, which were considered to be uncorrelated properties, inevitably determine the relative stability of various structures. The configuration of the defects in boron crystals is not capricious but there is some correlation among the defects. Many problems were solved on this ground, and contributed to the creation of the phase diagram. However, there are still many unsolved problems and some newly arose. In particular, for the tetragonal phase, sharp discrepancies are present in both experiment and theory. Thus, the problem of tetragonal phase is described in more detail. From the viewpoint of material research, the phase diagram provides the basis for searching new materials. State-of-the-art methods of structural prediction have stimulated researchers’ interest.

  15. Using Affinity Diagrams to Evaluate Interactive Prototypes

    OpenAIRE

    Lucero, Andrés

    2015-01-01

    International audience; Affinity diagramming is a technique used to externalize, make sense of, and organize large amounts of unstructured, far-ranging, and seemingly dissimilar qualitative data. HCI and interaction design practitioners have adopted and used affinity diagrams for different purposes. This paper discusses our particular use of affinity diagramming in prototype evaluations. We reflect on a decade’s experience using affinity diagramming across a number of projects, both in indust...

  16. Operations space diagram for ECRH and ECCD

    DEFF Research Database (Denmark)

    Bindslev, H.

    2004-01-01

    A Clemmov-Mullaly-Allis (CMA) type diagram, the ECW-CMA diagram, for representing the operational possibilities of electron cyclotron heating and current drive (ECRH/ECCD) systems for fusion plasmas is presented. In this diagram, with normalized density and normalized magnetic field coordinates...

  17. Reexamination of the possible tidal stream in front of the large Magellanic cloud

    NARCIS (Netherlands)

    Ibata, RA; Lewis, GF; Beaulieu, JP

    1998-01-01

    It has recently been suggested that the stars in a vertical extension of the red clump feature seen in LMC color-magnitude diagrams could belong to a tidal stream of material located in front of that galaxy. If this claim is correct, this foreground concentration of stars could contribute

  18. Evolution of dwarf galaxies in the Centaurus A group

    OpenAIRE

    Makarova, L.; Makarov, D.

    2007-01-01

    We consider star formation properties of dwarf galaxies in Cen A group observed within our HST/ACS projects number 9771 and 10235. We model color-magnitude diagrams of the galaxies under consideration and measure star formation rate and metallicity dependence on time. We study environmental dependence of the galaxy evolution and probable origin of the dwarf galaxies in the group.

  19. Wave Star

    DEFF Research Database (Denmark)

    Kramer, Morten; Brorsen, Michael; Frigaard, Peter

    Denne rapport beskriver numeriske beregninger af forskellige flydergeometrier for bølgeenergianlæget Wave Star.......Denne rapport beskriver numeriske beregninger af forskellige flydergeometrier for bølgeenergianlæget Wave Star....

  20. Diagram, a Learning Environment for Initiation to Object-Oriented Modeling with UML Class Diagrams

    Science.gov (United States)

    Py, Dominique; Auxepaules, Ludovic; Alonso, Mathilde

    2013-01-01

    This paper presents Diagram, a learning environment for object-oriented modelling (OOM) with UML class diagrams. Diagram an open environment, in which the teacher can add new exercises without constraints on the vocabulary or the size of the diagram. The interface includes methodological help, encourages self-correcting and self-monitoring, and…

  1. Using Affinity Diagrams to Evaluate Interactive Prototypes

    DEFF Research Database (Denmark)

    Lucero, Andrés

    2015-01-01

    our particular use of affinity diagramming in prototype evaluations. We reflect on a decade’s experience using affinity diagramming across a number of projects, both in industry and academia. Our affinity diagramming process in interaction design has been tailored and consists of four stages: creating......Affinity diagramming is a technique used to externalize, make sense of, and organize large amounts of unstructured, far-ranging, and seemingly dissimilar qualitative data. HCI and interaction design practitioners have adopted and used affinity diagrams for different purposes. This paper discusses...

  2. Diagram Size vs. Layout Flaws: Understanding Quality Factors of UML Diagrams

    DEFF Research Database (Denmark)

    Störrle, Harald

    2016-01-01

    , though, is our third goal of extending our analysis aspects of diagram quality. Method: We improve our definition of diagram size and add a (provisional) definition of diagram quality as the number of topographic layout flaws. We apply these metrics on 60 diagrams of the five most commonly used types......, and extend them to two new diagram types. We provide an improved definition of diagram size, and provide a definition of topographic layout quality, which is one more step towards a comprehensive definition of diagram quality as such. Both metrics are shown to be objectively applicable. We quantify......Context: Previously, we have defined the notion of diagram size and studied its impact on the understanding of UML diagrams. Subsequently, questions have been raised regarding the reliability and generality of our findings. Also, new questions arose regarding how the quality of diagrams could...

  3. Star clusters

    NARCIS (Netherlands)

    Gieles, M.

    2006-01-01

    Star clusters are observed in almost every galaxy. In this thesis we address several fundamental problems concerning the formation, evolution and disruption of star clusters. From observations of (young) star clusters in the interacting galaxy M51, we found that clusters are formed in complexes of

  4. Hybrid stars

    Indian Academy of Sciences (India)

    from two classes of EOS's and discuss their implications. Keywords. Neutron stars; phase transition. It is generally believed that the evolutionary journey of a star after it has exhausted all its fuel culminates into the formation of a compact object in the form of a white dwarf, a neutron star or a black hole depending on its mass.

  5. Massive Stars

    Science.gov (United States)

    Livio, Mario; Villaver, Eva

    2009-11-01

    Participants; Preface Mario Livio and Eva Villaver; 1. High-mass star formation by gravitational collapse of massive cores M. R. Krumholz; 2. Observations of massive star formation N. A. Patel; 3. Massive star formation in the Galactic center D. F. Figer; 4. An X-ray tour of massive star-forming regions with Chandra L. K. Townsley; 5. Massive stars: feedback effects in the local universe M. S. Oey and C. J. Clarke; 6. The initial mass function in clusters B. G. Elmegreen; 7. Massive stars and star clusters in the Antennae galaxies B. C. Whitmore; 8. On the binarity of Eta Carinae T. R. Gull; 9. Parameters and winds of hot massive stars R. P. Kudritzki and M. A. Urbaneja; 10. Unraveling the Galaxy to find the first stars J. Tumlinson; 11. Optically observable zero-age main-sequence O stars N. R. Walborn; 12. Metallicity-dependent Wolf-Raynet winds P. A. Crowther; 13. Eruptive mass loss in very massive stars and Population III stars N. Smith; 14. From progenitor to afterlife R. A. Chevalier; 15. Pair-production supernovae: theory and observation E. Scannapieco; 16. Cosmic infrared background and Population III: an overview A. Kashlinsky.

  6. A Hot Water Bottle for Aging Neutron Stars

    DEFF Research Database (Denmark)

    Alford, Mark; Jotwani, Pooja; Kouvaris, Christoforos

    2004-01-01

    The gapless color-flavor locked (gCFL) phase is the second-densest phase of matter in the QCD phase diagram, making it a plausible constituent of the core of neutron stars. We show that even a relatively small region of gCFL matter in a star will dominate both the heat capacity C_V and the heat...

  7. Observational constraints on mass loss and evolution of massive stars

    NARCIS (Netherlands)

    de Koter, A.

    2008-01-01

    We review the empirical mass-loss properties of early-type stars in the upper part of the Hertzsprung-Russell diagram. Specifically, we focus on the relation between mass loss and chemical composition by comparing properties of massive stars in our galaxy with those in the Magellanic Clouds. The

  8. Grid diagrams and Khovanov homology

    DEFF Research Database (Denmark)

    Droz, Jean-Marie; Wagner, Emmanuel

    2009-01-01

    We explain how to compute the Jones polynomial of a link from one of its grid diagrams and we observe a connection between Bigelow’s homological definition of the Jones polynomial and Kauffman’s definition of the Jones polynomial. Consequently, we prove that the Maslov grading on the Seidel–Smith...... symplectic link invariant coincides with the difference between the homological grading on Khovanov homology and the Jones grading on Khovanov homology. We give some evidence for the truth of the Seidel–Smith conjecture....

  9. Transformations of triangle ladder diagrams

    OpenAIRE

    Kondrashuk, Igor; Vergara, Alvaro

    2009-01-01

    It is shown how dual space diagrammatic representation of momentum integrals corresponding to triangle ladder diagrams with an arbitrary number of rungs can be transformed to half-diamonds. In paper arXiv:0803.3420 [hep-th] the half-diamonds were related by conformal integral substitution to the diamonds which represent the dual space image of four-point ladder integrals in the four-dimensional momentum space. Acting in the way described in the present paper we do not need to use the known re...

  10. Star-forming AGN host galaxies

    NARCIS (Netherlands)

    Barthel, P

    2001-01-01

    The symbiosis of nuclear activity and star-formation in galaxies, as manifested in their spectral energy distributions (SEDs) is reviewed. Attention is drawn to an Hertzsprung-Russell diagram - equivalent for such objects, as well as to the importance of the SEDs in cosmological context. (C) 2001

  11. Disconnected Diagrams in Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Gambhir, Arjun [College of William and Mary, Williamsburg, VA (United States)

    2017-08-01

    In this work, we present state-of-the-art numerical methods and their applications for computing a particular class of observables using lattice quantum chromodynamics (Lattice QCD), a discretized version of the fundamental theory of quarks and gluons. These observables require calculating so called \\disconnected diagrams" and are important for understanding many aspects of hadron structure, such as the strange content of the proton. We begin by introducing the reader to the key concepts of Lattice QCD and rigorously define the meaning of disconnected diagrams through an example of the Wick contractions of the nucleon. Subsequently, the calculation of observables requiring disconnected diagrams is posed as the computationally challenging problem of finding the trace of the inverse of an incredibly large, sparse matrix. This is followed by a brief primer of numerical sparse matrix techniques that overviews broadly used methods in Lattice QCD and builds the background for the novel algorithm presented in this work. We then introduce singular value deflation as a method to improve convergence of trace estimation and analyze its effects on matrices from a variety of fields, including chemical transport modeling, magnetohydrodynamics, and QCD. Finally, we apply this method to compute observables such as the strange axial charge of the proton and strange sigma terms in light nuclei. The work in this thesis is innovative for four reasons. First, we analyze the effects of deflation with a model that makes qualitative predictions about its effectiveness, taking only the singular value spectrum as input, and compare deflated variance with different types of trace estimator noise. Second, the synergy between probing methods and deflation is investigated both experimentally and theoretically. Third, we use the synergistic combination of deflation and a graph coloring algorithm known as hierarchical probing to conduct a lattice calculation of light disconnected matrix elements

  12. Bayesian Networks and Influence Diagrams

    DEFF Research Database (Denmark)

    Kjærulff, Uffe Bro; Madsen, Anders Læsø

    , and exercises are included for the reader to check his/her level of understanding. The techniques and methods presented for knowledge elicitation, model construction and verification, modeling techniques and tricks, learning models from data, and analyses of models have all been developed and refined......, troubleshooting, and data mining under uncertainty. Bayesian Networks and Influence Diagrams: A Guide to Construction and Analysis provides a comprehensive guide for practitioners who wish to understand, construct, and analyze intelligent systems for decision support based on probabilistic networks. Intended...... primarily for practitioners, this book does not require sophisticated mathematical skills or deep understanding of the underlying theory and methods nor does it discuss alternative technologies for reasoning under uncertainty. The theory and methods presented are illustrated through more than 140 examples...

  13. Phase diagrams for surface alloys

    DEFF Research Database (Denmark)

    Christensen, Asbjørn; Ruban, Andrei; Stoltze, Per

    1997-01-01

    of the heat of segregation from the bulk and the sign of the excess interactions between the atoms in the surface (the surface mixing energy). We also consider the more complicated cases a with ordered surface phases, nonpseudomorphic overlayers, second layer segregation, and multilayers. The discussion......We discuss surface alloy phases and their stability based on surface phase diagrams constructed from the surface energy as a function of the surface composition. We show that in the simplest cases of pseudomorphic overlayers there are four generic classes of systems, characterized by the sign...... is based on density-functional calculations using the coherent-potential approximation and on effective-medium theory. We give self-consistent density-functional results for the segregation energy and surface mixing energy for all combinations of the transition and noble metals. Finally we discuss...

  14. Stereo 3D spatial phase diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Jinwu, E-mail: kangjw@tsinghua.edu.cn; Liu, Baicheng, E-mail: liubc@tsinghua.edu.cn

    2016-07-15

    Phase diagrams serve as the fundamental guidance in materials science and engineering. Binary P-T-X (pressure–temperature–composition) and multi-component phase diagrams are of complex spatial geometry, which brings difficulty for understanding. The authors constructed 3D stereo binary P-T-X, typical ternary and some quaternary phase diagrams. A phase diagram construction algorithm based on the calculated phase reaction data in PandaT was developed. And the 3D stereo phase diagram of Al-Cu-Mg ternary system is presented. These phase diagrams can be illustrated by wireframe, surface, solid or their mixture, isotherms and isopleths can be generated. All of these can be displayed by the three typical display ways: electronic shutter, polarization and anaglyph (for example red-cyan glasses). Especially, they can be printed out with 3D stereo effect on paper, and watched by the aid of anaglyph glasses, which makes 3D stereo book of phase diagrams come to reality. Compared with the traditional illustration way, the front of phase diagrams protrude from the screen and the back stretches far behind of the screen under 3D stereo display, the spatial structure can be clearly and immediately perceived. These 3D stereo phase diagrams are useful in teaching and research. - Highlights: • Stereo 3D phase diagram database was constructed, including binary P-T-X, ternary, some quaternary and real ternary systems. • The phase diagrams can be watched by active shutter or polarized or anaglyph glasses. • The print phase diagrams retains 3D stereo effect which can be achieved by the aid of anaglyph glasses.

  15. A catalogue of Irish pollen diagrams

    OpenAIRE

    Mitchell, Fraser

    2013-01-01

    PUBLISHED The first Irish pollen diagram was published by Gunnar Erdtman in the Irish Naturalists? Journal in 1927. Since then over 471 pollen diagrams have been produced from locations throughout Ireland from a range of sites and time spans. The data from these pollen diagrams can be used to reconstruct vegetation dynamics over long time scales and so facilitate the investigation of climate change impacts, plant migration and the scale of human induced landscape change. In this paper we ...

  16. Collaborating on Affinity Diagrams Using Large Displays

    OpenAIRE

    Judge, Tejinder K.; McCrickard, D. Scott

    2008-01-01

    Gathering and understanding user requirements is an essential part of design. Techniques like affinity diagramming are useful for gathering and understanding user data but have shortcomings such as the difficulty to preserve the diagram after its creation, problems during the process such as searching for notes, and loss of shared awareness. We propose an early prototype that solves problems in the process of creating an affinity diagram and enhances it using a...

  17. Star Wreck

    CERN Document Server

    Kusenko, A; Tinyakov, Peter G; Tkachev, Igor I; Kusenko, Alexander; Shaposhnikov, Mikhail; Tkachev, Igor I.

    1998-01-01

    Electroweak models with low-energy supersymmetry breaking predict the existence of stable non-topological solitons, Q-balls, that can be produced in the early universe. The relic Q-balls can accumulate inside a neutron star and gradually absorb the baryons into the scalar condensate. This causes a slow reduction in the mass of the star. When the mass reaches a critical value, the neutron star becomes unstable and explodes. The cataclysmic destruction of the distant neutron stars may be the origin of the gamma-ray bursts.

  18. Neutron Stars

    Science.gov (United States)

    Cottam, J.

    2007-01-01

    Neutron stars were discovered almost 40 years ago, and yet many of their most fundamental properties remain mysteries. There have been many attempts to measure the mass and radius of a neutron star and thereby constrain the equation of state of the dense nuclear matter at their cores. These have been complicated by unknown parameters such as the source distance and burning fractions. A clean, straightforward way to access the neutron star parameters is with high-resolution spectroscopy. I will present the results of searches for gravitationally red-shifted absorption lines from the neutron star atmosphere using XMM-Newton and Chandra.

  19. Stage line diagram: An age-conditional reference diagram for tracking development

    NARCIS (Netherlands)

    Buuren, S. van; Ooms, J.C.L.

    2009-01-01

    This paper presents a method for calculating stage line diagrams, a novel type of reference diagram useful for tracking developmental processes over time. Potential fields of applications include: dentistry (tooth eruption), oncology (tumor grading, cancer staging), virology (HIV infection and

  20. Star Imager

    DEFF Research Database (Denmark)

    Madsen, Peter Buch; Jørgensen, John Leif; Thuesen, Gøsta

    1997-01-01

    The version of the star imager developed for Astrid II is described. All functions and features are described as well as the operations and the software protocol.......The version of the star imager developed for Astrid II is described. All functions and features are described as well as the operations and the software protocol....

  1. Star Polymers.

    Science.gov (United States)

    Ren, Jing M; McKenzie, Thomas G; Fu, Qiang; Wong, Edgar H H; Xu, Jiangtao; An, Zesheng; Shanmugam, Sivaprakash; Davis, Thomas P; Boyer, Cyrille; Qiao, Greg G

    2016-06-22

    Recent advances in controlled/living polymerization techniques and highly efficient coupling chemistries have enabled the facile synthesis of complex polymer architectures with controlled dimensions and functionality. As an example, star polymers consist of many linear polymers fused at a central point with a large number of chain end functionalities. Owing to this exclusive structure, star polymers exhibit some remarkable characteristics and properties unattainable by simple linear polymers. Hence, they constitute a unique class of technologically important nanomaterials that have been utilized or are currently under audition for many applications in life sciences and nanotechnologies. This article first provides a comprehensive summary of synthetic strategies towards star polymers, then reviews the latest developments in the synthesis and characterization methods of star macromolecules, and lastly outlines emerging applications and current commercial use of star-shaped polymers. The aim of this work is to promote star polymer research, generate new avenues of scientific investigation, and provide contemporary perspectives on chemical innovation that may expedite the commercialization of new star nanomaterials. We envision in the not-too-distant future star polymers will play an increasingly important role in materials science and nanotechnology in both academic and industrial settings.

  2. Wave Star

    DEFF Research Database (Denmark)

    Kramer, Morten; Brorsen, Michael; Frigaard, Peter

    Nærværende rapport beskriver numeriske beregninger af den hydrodynamiske interaktion mellem 5 flydere i bølgeenergianlægget Wave Star.......Nærværende rapport beskriver numeriske beregninger af den hydrodynamiske interaktion mellem 5 flydere i bølgeenergianlægget Wave Star....

  3. Diagrams Benefit Symbolic Problem-Solving

    Science.gov (United States)

    Chu, Junyi; Rittle-Johnson, Bethany; Fyfe, Emily R.

    2017-01-01

    Background: The format of a mathematics problem often influences students' problem-solving performance. For example, providing diagrams in conjunction with story problems can benefit students' understanding, choice of strategy, and accuracy on story problems. However, it remains unclear whether providing diagrams in conjunction with symbolic…

  4. Ferroelectric phase diagram of PVDF:PMMA

    NARCIS (Netherlands)

    Li, M.; Stingelin, N.; Michels, J.J.; Spijkman, M.-J.; Asadi, K.; Feldman, K.; Blom, P.W.M.; Leeuw, D.M. de

    2012-01-01

    We have investigated the ferroelectric phase diagram of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA). The binary nonequilibrium temperature composition diagram was determined and melting of α- and β-phase PVDF was identified. Ferroelectric β-PVDF:PMMA blend films were made

  5. Ferroelectric Phase Diagram of PVDF : PMMA

    NARCIS (Netherlands)

    Li, Mengyuan; Stingelin, Natalie; Michels, Jasper J.; Spijkman, Mark-Jan; Asadi, Kamal; Feldman, Kirill; Blom, Paul W. M.; de Leeuw, Dago M.

    2012-01-01

    We have investigated the ferroelectric phase diagram of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA). The binary nonequilibrium temperature composition diagram was determined and melting of alpha- and beta-phase PVDF was identified. Ferroelectric beta-PVDF:PMMA blend films

  6. Comprehending process diagrams in biology education

    NARCIS (Netherlands)

    Kragten, M.

    2015-01-01

    Students in secondary Science education seem to have difficulties with comprehending diagrams. Process diagrams are an important type of representation in Biology for explaining processes like protein synthesis, compound cycles, etc. In this thesis, we aimed at getting deeper insight into students’

  7. Phase diagram of ammonium nitrate

    Energy Technology Data Exchange (ETDEWEB)

    Dunuwille, Mihindra; Yoo, Choong-Shik, E-mail: csyoo@wsu.edu [Department of Chemistry and Institute for Shock Physics, Washington State University, Pullman, Washington 99164 (United States)

    2013-12-07

    Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO–AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N{sub 2}, N{sub 2}O, and H{sub 2}O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV{sup ′} transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C.

  8. New constraints on the star formation history of the star cluster NGC 1856

    NARCIS (Netherlands)

    Correnti, M.; Goudfrooij, P.; Puzia, T.H.; de Mink, S.E.

    2015-01-01

    We use the Wide Field Camera 3 onboard the Hubble Space Telescope to obtain deep, high-resolution photometry of the young (age ∼ 300 Myr) star cluster NGC 1856 in the Large Magellanic Cloud. We compare the observed colour-magnitude diagram (CMD), after having applied a correction for differential

  9. Experimental Approach to the QCD Phase Diagram - Beam Energy Scan at RHIC

    Science.gov (United States)

    Odyniec, G.

    2009-04-01

    The QCD phase diagram appears to be the most important single figure of our field. While recent progress in Lattice QCD (LQCD) and model calculations is impressive, the location of phase boundaries and the exact position of the hypothetical critical point (CP) remains unknown. The available theoretical estimates, however, indicate that the critical point might be in the region of the phase diagram probed by current heavy ion experiments. The Beam Energy Scan (BES) program at RHIC, described in this paper, was launched to expand the experimental study where theory cannot yet reach. Both large RHIC experiments, STAR and PHENIX, are in the process of preparing for the first run. Particularly STAR with its large, uniform acceptance and excellent particle identification capabilities, is uniquely positioned to cover this physics in unprecedented depth and detail.

  10. Faceting diagram for sticky steps

    Directory of Open Access Journals (Sweden)

    Noriko Akutsu

    2016-03-01

    Full Text Available Faceting diagrams for the step-faceting zone, the step droplet zone, and the Gruber-Mullins-Pokrovsky-Talapov (GMPT zone for a crystal surface are obtained by using the density matrix renormalization group method to calculate the surface tension. The model based on these calculations is the restricted solid-on-solid (RSOS model with a point-contact-type step-step attraction (p-RSOS model on a square lattice. The point-contact-type step-step attraction represents the energy gain obtained by forming a bonding state with orbital overlap at the meeting point of the neighboring steps. In the step-faceting zone, disconnectedness in the surface tension leads to the formation of a faceted macrostep on a vicinal surface at equilibrium. The disconnectedness in the surface tension also causes the first-order shape transition for the equilibrium shape of a crystal droplet. The lower zone boundary line (ZBL, which separates the step-faceting zone and the step droplet zone, is obtained by the condition γ 1 = lim n → ∞ γ n / n , where γn is the step tension of the n-th merged step. The upper ZBL, which separates the GMPT zone and the step droplet zone, is obtained by the condition Aq,eff = 0 and Bq,eff = 0, where Aq,eff and Bq,eff represent the coefficients for the | q → | 2 term and the | q → | 3 term, respectively, in the | q → | -expanded form of the surface free energy f eff ( q → . Here, q → is the surface gradient relative to the (111 surface. The reason why the vicinal surface inclined in the 〈101〉 direction does not exhibit step-faceting is explained in terms of the one-dimensional spinless quasi-impenetrable attractive bosons at absolute zero.

  11. Carbon Stars

    Indian Academy of Sciences (India)

    Abstract. In this paper, the present state of knowledge of the carbon stars is discussed. Particular attention is given to issues of classification, evolution, variability, populations in our own and other galaxies, and circumstellar material.

  12. Wave Star

    DEFF Research Database (Denmark)

    Kramer, Morten; Andersen, Thomas Lykke

    Nærværende rapport beskriver modelforsøg udført på Aalborg Universitet, Institut for Vand, Jord og Miljøteknik med bølgeenergianlægget Wave Star.......Nærværende rapport beskriver modelforsøg udført på Aalborg Universitet, Institut for Vand, Jord og Miljøteknik med bølgeenergianlægget Wave Star....

  13. Wave Star

    DEFF Research Database (Denmark)

    Kramer, Morten; Frigaard, Peter

    Nærværende rapport beskriver modelforsøg udført på Aalborg Universitet, Institut for Byggeri og Anlæg med bølgeenergianlæget Wave Star.......Nærværende rapport beskriver modelforsøg udført på Aalborg Universitet, Institut for Byggeri og Anlæg med bølgeenergianlæget Wave Star....

  14. Between Analogue and Digital Diagrams

    Directory of Open Access Journals (Sweden)

    Zoltan Bun

    2012-10-01

    Full Text Available This essay is about the interstitial. About how the diagram, as a method of design, has lead fromthe analogue deconstruction of the eighties to the digital processes of the turn of the millennium.Specifically, the main topic of the text is the interpretation and the critique of folding (as a diagramin the beginning of the nineties. It is necessary then to unfold its relationship with immediatelypreceding and following architectural trends, that is to say we have to look both backwards andforwards by about a decade. The question is the context of folding, the exchange of the analogueworld for the digital. To understand the process it is easier to investigate from the fields of artand culture, rather than from the intentionally perplicated1 thoughts of Gilles Deleuze. Both fieldsare relevant here because they can similarly be used as the yardstick against which the era itselfit measured. The cultural scene of the eighties and nineties, including performing arts, movies,literature and philosophy, is a wide milieu of architecture. Architecture responds parallel to itsera; it reacts to it, and changes with it and within it. Architecture is a medium, it has always beena medium, yet the relations are transformed. That’s not to say that technical progress, for exampleusing CAD-software and CNC-s, has led to the digital thinking of certain movements ofarchitecture, (it is at most an indirect tool. But the ‘up-to-dateness’ of the discipline, however,a kind of non-servile reading of an ‘applied culture’ or ‘used philosophy’2 could be the key.(We might recall here, parenthetically, the fortunes of the artistic in contemporary mass society.The proliferation of museums, the magnification of the figure of the artist, the existence of amassive consumption of printed and televised artistic images, the widespread appetite for informationabout the arts, all reflect, of course, an increasingly leisured society, but also relateprecisely to the fact

  15. Covariant diagrams for one-loop matching

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhengkang [Michigan Univ., Ann Arbor, MI (United States). Michigan Center for Theoretical Physics; Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2016-10-15

    We present a diagrammatic formulation of recently-revived covariant functional approaches to one-loop matching from an ultraviolet (UV) theory to a low-energy effective field theory. Various terms following from a covariant derivative expansion (CDE) are represented by diagrams which, unlike conventional Feynman diagrams, involve gaugecovariant quantities and are thus dubbed ''covariant diagrams.'' The use of covariant diagrams helps organize and simplify one-loop matching calculations, which we illustrate with examples. Of particular interest is the derivation of UV model-independent universal results, which reduce matching calculations of specific UV models to applications of master formulas. We show how such derivation can be done in a more concise manner than the previous literature, and discuss how additional structures that are not directly captured by existing universal results, including mixed heavy-light loops, open covariant derivatives, and mixed statistics, can be easily accounted for.

  16. On divisorial filtrations associated with Newton diagrams

    OpenAIRE

    Ebeling, Wolfgang; Gusein-Zade, Sabir M.

    2010-01-01

    We consider divisorial filtration on the rings of functions on hypersurface singularities associated with Newton diagrams and their analogues for plane curve singularities. We compute the multi-variable Poincar\\'e series for the latter ones.

  17. Architecture flow diagrams under teamwork reg sign

    Energy Technology Data Exchange (ETDEWEB)

    Nicinski, T.

    1992-02-01

    The Teamwork CASE tool allows Data Flow Diagrams (DFDs) to be maintained for structured analysis. Fermilab has extended teamwork under UNIX{trademark} to permit Hatley and Pirbhai Architecture Flow Diagrams (AFDs) to be associated with DFDs and subsequently maintained. This extension, called TWKAFD, allows a user to open an AFD, graphically edit it, and replace it into a TWKAFD maintained library. Other aspects of Hatley and Pirbhai's methodology are supported. This paper presents a quick tutorial on Architecture Diagrams. It then describes the user's view of TWKAFD, the experience incorporating it into teamwork, and the successes with using the Architecture Diagram methodology along with the shortcomings of using the teamwork/TWKAFD tool. 8 refs.

  18. Radial Color Gradient in a Globular Cluster 1. M68

    Directory of Open Access Journals (Sweden)

    Sukyoung Yi

    1990-12-01

    Full Text Available Stars in M68 from the observed color-magnitude diagrams with CCD were integrated to find any radial gradient. The result shows that M68 has a slightly bluer core. The main cause of these calculated radial color variations seems to come from the random distribution of giants.

  19. Anomalous evolution of the dwarf galaxy HIPASS J1321-31

    NARCIS (Netherlands)

    Pritzl, BJ; Knezek, PM; Gallagher, JS; Grossi, M; Disney, MJ; Minchin, RF; Freeman, KC; Tolstoy, E; Saha, A

    2003-01-01

    We present Hubble Space Telescope/WFPC2 observations of the dwarf galaxy HIPASS J1321-31. This unusual galaxy lies in the direction of the Centaurus A group of galaxies and has a color-magnitude diagram with a distinctive red plume of luminous stars. This feature could arise from (1) a red giant

  20. A universal structured-design diagramer

    Science.gov (United States)

    1981-01-01

    Program (FLOWCHARTER) generates standardized flowcharts and concordances for development and debugging of programs in any language. User describes programming-language grammar, providing syntax rules in Backus-Naur form (BNF), list of semantic rules, and set of concordance rules. Once grammar is described, user supplies only source code of program to be diagrammed. FLOWCHARTER automatically produces flow diagram and concordance. Source code for program is written for PASCAL Release 2 compiler, as distributed by University of Minnesota.

  1. ISS EPS Orbital Replacement Unit Block Diagrams

    Science.gov (United States)

    Schmitz, Gregory V.

    2001-01-01

    The attached documents are being provided to Switching Power Magazine for information purposes. This magazine is writing a feature article on the International Space Station Electrical Power System, focusing on the switching power processors. These units include the DC-DC Converter Unit (DDCU), the Bi-directional Charge/Discharge Unit (BCDU), and the Sequential Shunt Unit (SSU). These diagrams are high-level schematics/block diagrams depicting the overall functionality of each unit.

  2. An Introduction to Binary Decision Diagrams

    DEFF Research Database (Denmark)

    Andersen, Henrik Reif

    1996-01-01

    This note is a short introduction to Binary Decision Diagrams (BDDs). It provides some background knowledge and describes the core algorithms. It is used in the course "C4340 Advanced Algorithms" at the Technical University of Denmark, autumn 1996.......This note is a short introduction to Binary Decision Diagrams (BDDs). It provides some background knowledge and describes the core algorithms. It is used in the course "C4340 Advanced Algorithms" at the Technical University of Denmark, autumn 1996....

  3. Characterizing Communication Channel Deadlocks in Sequence Diagrams

    OpenAIRE

    Mitchell, Bill

    2008-01-01

    UML sequence diagrams (SDs) are a mainstay of requirements specifications for communication protocols. Mauw and Reniers' algebraic (MRA) semantics formally specifies a behaviour for these SDs that guarantees deadlock free processes. Practitioners commonly use communication semantics that differ from MRA, which may result in deadlocks. For example FIFO, token ring, etc. We define a process algebra that is an extension of the MRA semantics for regular sequence diagrams. Our algebra can describe...

  4. Random Young diagrams in a Rectangular Box

    DEFF Research Database (Denmark)

    Beltoft, Dan; Boutillier, Cédric; Enriquez, Nathanaël

    We exhibit the limit shape of random Young diagrams having a distribution proportional to the exponential of their area, and confined in a rectangular box. The Ornstein-Uhlenbeck bridge arises from the fluctuations around the limit shape.......We exhibit the limit shape of random Young diagrams having a distribution proportional to the exponential of their area, and confined in a rectangular box. The Ornstein-Uhlenbeck bridge arises from the fluctuations around the limit shape....

  5. The application of diagrams in architectural design

    Directory of Open Access Journals (Sweden)

    Dulić Olivera

    2014-01-01

    Full Text Available Diagrams in architecture represent the visualization of the thinking process, or selective abstraction of concepts or ideas translated into the form of drawings. In addition, they provide insight into the way of thinking about and in architecture, thus creating a balance between the visual and the conceptual. The subject of research presented in this paper are diagrams as a specific kind of architectural representation, and possibilities and importance of their application in the design process. Diagrams are almost old as architecture itself, and they are an element of some of the most important studies of architecture during all periods of history - which results in a large number of different definitions of diagrams, but also very different conceptualizations of their features, functions and applications. The diagrams become part of contemporary architectural discourse during the eighties and nineties of the twentieth century, especially through the work of architects like Bernard Tschumi, Peter Eisenman, Rem Koolhaas, SANAA and others. The use of diagrams in the design process allows unification of some of the essential aspects of the profession: architectural representation and design process, as well as the question of the concept of architectural and urban design at a time of rapid changes at all levels of contemporary society. The aim of the research is the analysis of the diagram as a specific medium for processing large amounts of information that the architect should consider and incorporate into the architectural work. On that basis, it is assumed that an architectural diagram allows the creator the identification and analysis of specific elements or ideas of physical form, thereby constantly maintaining concept of the integrity of the architectural work.

  6. Atomic energy levels and Grotrian diagrams

    CERN Document Server

    Bashkin, Stanley

    1975-01-01

    Atomic Energy Levels and Grotrian Diagrams, Volume I: Hydrogen I - Phosphorus XV presents diagrams of various elements that show their energy level and electronic transitions. The book covers the first 15 elements according to their atomic number. The text will be of great use to researchers and practitioners of fields such as astrophysics that requires pictorial representation of the energy levels and electronic transitions of elements.

  7. Theoretical flow regime diagrams for the AGCE

    Science.gov (United States)

    Fowlis, W. W.; Miller, T. L.; Roberts, G. O.; Kopecky, K. J.

    1984-01-01

    The major criterion for the design of the Atmospheric General Circulation Experiment is that it be possible to realize strong baroclinic instability in the apparatus. A spherical annulus configuration which allows only steady basic state flows was chosen for the first set of stability analyses. Baroclinic instability was found for this configuration and few results suggest a regime diagram very different from the cylindrical annulus regime diagram.

  8. Beyond Feynman Diagrams (1/3)

    CERN Multimedia

    CERN. Geneva

    2013-01-01

    For decades the central theoretical tool for computing scattering amplitudes has been the Feynman diagram. However, Feynman diagrams are just too slow, even on fast computers, to be able to go beyond the leading order in QCD, for complicated events with many jets of hadrons in the final state. Such events are produced copiously at the LHC, and constitute formidable backgrounds to many searches for new physics. Over the past few years, alternative methods that go beyond ...

  9. Spectropolarimetry of Giant stars: Probing the influence of magnetic field on evolved stars Spectropolarimetry of Giant stars: Probing the influence of magnetic field on evolved stars

    Science.gov (United States)

    da Costa, Jefferson; Castro, Matthieu; Petit, Pascal; do Nascimento, José-Dias, Jr.

    2015-08-01

    It is know that lithium is element easily destroyed in stellar interior, the existence of lithium rich stars means a great challenge in stellar evolution. In this context our observations ravels the serendipitous discovery of an unusually high lithium abundance star. This is a K0III HD 150050, which has strong deepening on lithium line (6707.8 Å) this means lithium abundance of 2.81 0.2 dex, therefore this star belong a rare group called super Li-Rich stars. A possible source of the non-standard episodes required to produce Li-rich stars were identified in magneto-thermohaline mixing accounted by models of extra-mixing induced by magnetic buoyancy. However to better understand this is necessary more observational data. In last three decades several studies has showed that late type red giant stars presents a remarkable modifications in these outer atmosphere layers when they become late type star in HR diagram. These changes are founded through X-ray, Ultraviolet, and Chromospheric activity analyses, and then we can establish the called “Dividing lines”. We made spectropalarimetric observations with ESPaDOnS@CFHT to achieve two main objectives: analyze the influence of magnetic field in the Li-rich giant stars, and understand how works the magnetic field in late type giants and supergiants across the “dividing line”.

  10. Mapping the Tidal Destruction of the Hercules Dwarf: A Wide-field DECam Imaging Search for RR Lyrae Stars

    Science.gov (United States)

    Garling, Christopher; Willman, Beth; Sand, David J.; Hargis, Jonathan; Crnojević, Denija; Bechtol, Keith; Carlin, Jeffrey L.; Strader, Jay; Zou, Hu; Zhou, Xu; Nie, Jundan; Zhang, Tianmeng; Zhou, Zhimin; Peng, Xiyan

    2018-01-01

    We investigate the hypothesized tidal disruption of the Hercules ultra-faint dwarf galaxy (UFD). Previous tidal disruption studies of the Hercules UFD have been hindered by the high degree of foreground contamination in the direction of the dwarf. We bypass this issue by using RR Lyrae stars, which are standard candles with a very low field-volume density at the distance of Hercules. We use wide-field imaging from the Dark Energy Camera on CTIO to identify candidate RR Lyrae stars, supplemented with observations taken in coordination with the Beijing–Arizona Sky Survey on the Bok Telescope. Combining color, magnitude, and light-curve information, we identify three new RR Lyrae stars associated with Hercules. All three of these new RR Lyrae stars lie outside its published tidal radius. When considered with the nine RR Lyrae stars already known within the tidal radius, these results suggest that a substantial fraction of Hercules’ stellar content has been stripped. With this degree of tidal disruption, Hercules is an interesting case between a visibly disrupted dwarf (such as the Sagittarius dwarf spheroidal galaxy) and one in dynamic equilibrium. The degree of disruption also shows that we must be more careful with the ways we determine object membership when estimating dwarf masses in the future. One of the three discovered RR Lyrae stars sits along the minor axis of Hercules, but over two tidal radii away. This type of debris is consistent with recent models that suggest Hercules’ orbit is aligned with its minor axis.

  11. Pathway collages: personalized multi-pathway diagrams.

    Science.gov (United States)

    Paley, Suzanne; O'Maille, Paul E; Weaver, Daniel; Karp, Peter D

    2016-12-13

    Metabolic pathway diagrams are a classical way of visualizing a linked cascade of biochemical reactions. However, to understand some biochemical situations, viewing a single pathway is insufficient, whereas viewing the entire metabolic network results in information overload. How do we enable scientists to rapidly construct personalized multi-pathway diagrams that depict a desired collection of interacting pathways that emphasize particular pathway interactions? We define software for constructing personalized multi-pathway diagrams called pathway-collages using a combination of manual and automatic layouts. The user specifies a set of pathways of interest for the collage from a Pathway/Genome Database. Layouts for the individual pathways are generated by the Pathway Tools software, and are sent to a Javascript Pathway Collage application implemented using Cytoscape.js. That application allows the user to re-position pathways; define connections between pathways; change visual style parameters; and paint metabolomics, gene expression, and reaction flux data onto the collage to obtain a desired multi-pathway diagram. We demonstrate the use of pathway collages in two application areas: a metabolomics study of pathogen drug response, and an Escherichia coli metabolic model. Pathway collages enable facile construction of personalized multi-pathway diagrams.

  12. On the Impact of Layout Quality to Understanding UML Diagrams: Diagram Type and Expertise

    DEFF Research Database (Denmark)

    Störrle, Harald

    2012-01-01

    . In the current paper, we expand on our earlier experiments by varying both diagram types and populations studied. We find no difference in the beneficial evidence of good layout wrt. diagram types. We also find support for the hypothesis that experts benefit less than novices. While still lacking independent...

  13. The Semiotic Structure of Geometry Diagrams: How Textbook Diagrams Convey Meaning

    Science.gov (United States)

    Dimmel, Justin K.; Herbst, Patricio G.

    2015-01-01

    Geometry diagrams use the visual features of specific drawn objects to convey meaning about generic mathematical entities. We examine the semiotic structure of these visual features in two parts. One, we conduct a semiotic inquiry to conceptualize geometry diagrams as mathematical texts that comprise choices from different semiotic systems. Two,…

  14. Pulsating stars

    CERN Document Server

    Catelan, M?rcio

    2014-01-01

    The most recent and comprehensive book on pulsating stars which ties the observations to our present understanding of stellar pulsation and evolution theory.  Written by experienced researchers and authors in the field, this book includes the latest observational results and is valuable reading for astronomers, graduate students, nuclear physicists and high energy physicists.

  15. Stars Underground

    CERN Multimedia

    Jean Leyder

    1996-01-01

    An imaginary voyage in time where we were witness of the birth of the universe itself, the time of the Big-Bang 15 billion years ago. Particules from the very first moments of time : protons, neutrons and electrons, and also much more energetic one. These particules are preparing to interact collider and generating others which will be the birth to the stars ........

  16. On the mass distribution of stars in the solar neighborhood

    Directory of Open Access Journals (Sweden)

    Ninković S.

    2006-01-01

    Full Text Available The present authors analyze samples consisting of Hipparcos stars. Based on the corresponding HR diagrams they estimate masses of Main-Sequence stars from their visual magnitudes. They find that already beyond the heliocentric radius of 10 pc the effects of observational selection against K and M dwarfs become rather strong. For this reason the authors are inclined to think that the results concerning this heliocentric sphere appear as realistic, i. e. the fraction of low-mass stars (under half solar mass is about 50% and, as a consequence, the mean star mass should be about 0.6 solar masses and Agekyan's factor about 1.2. That stars with masses higher than 5 M○ are very rare is confirmed also from the data concerning more remote stars. It seems that white dwarfs near the Sun are not too frequent so that their presence cannot affect the main results of the present work significantly.

  17. Chemistry of Carbon Rich Star IRAS 15194–5115 A. Ali

    Indian Academy of Sciences (India)

    1. Introduction. IRAS 15194–5115 is the third brightest carbon star at 12 µm and the brightest one known in the southern hemisphere. The object was identified as a carbon star from optical and infrared spectroscopy (Meadows et al. 1987), and from its position in the. [K-L, 12 µm–12 µm] color–color diagram (Epchtein et al.

  18. The ancient stellar population of M 32 : RR Lyrae variable stars confirmed

    NARCIS (Netherlands)

    Fiorentino, G.; Ramos, R. Contreras; Tolstoy, E.; Clementini, G.; Saha, A.

    Using archival multi-epoch ACS/WFC images in the F606W and F814W filters of a resolved stellar field in Local Group dwarf elliptical galaxy M 32 we have made an accurate colour-magnitude diagram and a careful search for RR Lyr variable stars. We identified 416 bona fide RR Lyr stars over our field

  19. Effects of axions on Population III stars

    Science.gov (United States)

    Choplin, Arthur; Coc, Alain; Meynet, Georges; Olive, Keith A.; Uzan, Jean-Philippe; Vangioni, Elisabeth

    2017-09-01

    Aims: Following the renewed interest in axions as a dark matter component, we revisit the effects of energy loss by axion emission on the evolution of the first generation of stars. These stars with zero metallicity are assumed to be massive, more compact, and hotter than subsequent generations. It is hence important to extend previous studies, which were restricted to solar metallicity stars. Methods: Our analysis first compares the evolution of solar metallicity 8, 10, and 12 M⊙ stars to previous work. We then calculate the evolution of 8 zero-metallicity stars with and without axion losses and with masses ranging from 20 to 150 M⊙. Results: For the solar metallicity models, we confirm the disappearance of the blue-loop phase for a value of the axion-photon coupling of gaγ = 10-10 GeV-1. We show that for gaγ = 10-10 GeV-1, the evolution of Population III stars is not much affected by axion losses, except within the range of masses 80-130 M⊙. Such stars show significant differences in both their tracks within the Tc-ρc diagram and their central composition (in particular 20Ne and 24Mg). We discuss the origin of these modifications from the stellar physics point of view, and also their potential observational signatures.

  20. Model FORC diagrams for hybrid magnetic elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Vaganov, M.V., E-mail: mikhail.vaganov.sci@gmail.com.ru [Institute of Continuous Media Mechanics, Russian Academy of Sciences, Ural Branch, Perm, 614013 (Russian Federation); Linke, J.; Odenbach, S. [Technische Universität Dresden, Dresden, 01062 Germany (Germany); Raikher, Yu.L. [Institute of Continuous Media Mechanics, Russian Academy of Sciences, Ural Branch, Perm, 614013 (Russian Federation); Ural Federal University, Ekaterinburg, 620083 (Russian Federation)

    2017-06-01

    We propose a model of hybrid magnetic elastomers filled with a mixture of magnetically soft and magnetically hard microparticles. The magnetically hard particles are described by the Stoner–Wohlfarth model, the magnetically soft phase obeys the Fröhlich–Kennelly equation. The interaction between the two types of particles is described by the mean-field approach. First-order reversal curve (FORC) diagrams were calculated for different values of the elastomer matrix elasticity. We demonstrate that the diagrams display specific new features, which identify the presence of both a deformable matrix and the two types of magnetic particles. - Highlights: • A model of hybrid magnetic elastomers is proposed. • The magnetically hard particles are described by the Stoner–Wohlfarth model. • The magnetically soft phase obeys the Fröhlich–Kennelly equation. The interaction between the phases is described by the mean-field approach. • FORC diagrams are calculated for different values of the elastomer matrix elasticity.

  1. Star Products and Applications

    OpenAIRE

    Iida, Mari; Yoshioka, Akira

    2010-01-01

    Star products parametrized by complex matrices are defined. Especially commutative associative star products are treated, and star exponentials with respect to these star products are considered. Jacobi's theta functions are given as infinite sums of star exponentials. As application, several concrete identities are obtained by properties of the star exponentials.

  2. Partial chord diagrams and matrix models

    DEFF Research Database (Denmark)

    Andersen, Jørgen Ellegaard; Fuji, Hiroyuki; Manabe, Masahide

    spectrum. Furthermore, we consider the boundary length and point spectrum that unifies the last two types of spectra. We introduce matrix models that encode generating functions of partial chord diagrams filtered by each of these spectra. Using these matrix models, we derive partial differential equations......In this article, the enumeration of partial chord diagrams is discussed via matrix model techniques. In addition to the basic data such as the number of backbones and chords, we also consider the Euler characteristic, the backbone spectrum, the boundary point spectrum, and the boundary length...

  3. Adding a Dimension to Logic Diagramming

    OpenAIRE

    Goldstein, Laurence

    2011-01-01

    A blind learner needs some method other than Venn diagrams to test syllogisms for validity. I present here a sketch of a three-dimensional apparatus, Sylloid, invented to fill this need and to inculcate deep learning rather than the mere ability to get answers right. What one learns in the design process is then used in designing a successor, Son of Sylloid, for sighted users that is pedagogically superior to Venn diagrams. This dog-legged approach to materials design is of wide application: ...

  4. Fusion Diagrams in the - and - Systems

    Science.gov (United States)

    Asadov, M. M.; Akhmedova, N. A.

    2014-10-01

    A calculation model of the Gibbs energy of ternary oxide compounds from the binary components was used. Thermodynamic properties of -- ternary systems in the condensed state were calculated. Thermodynamic data of binary and ternary compounds were used to determine the stable sections. The probability of reactions between the corresponding components in the -- system was estimated. Fusibility diagrams of systems - and - were studied by physical-chemical analysis. The isothermal section of the phase diagram of -- at 298 K is built, as well as the projection of the liquid surface of --.

  5. BDL: A Semantics Backbone for UML Dynamic Diagrams

    OpenAIRE

    Caillaud, Benoit; Talpin, Jean-Pierre; Jézéquel, Jean-Marc; Benveniste, Albert; Jard, Claude

    2000-01-01

    The UML (Unified Modelling Language) comprises various types of notations, to model the functional architecture, the behaviour of its components, and its deployment. Dynamic diagrams provide descriptions of the components and system behaviour. Examples of dynamic diagrams are collaboration and sequence diagrams to specify high level abstractions for sequences of actions involving several components of the system. Activity diagrams, state diagrams, and statecharts are used to specify the detai...

  6. Cool half of the H-R diagram in soft X-rays

    Energy Technology Data Exchange (ETDEWEB)

    Ayres, T.R.; Linsky, J.L.; Vaiana, G.S.; Golub, L.; Rosner, R.

    1981-11-01

    We report results of an Einstein Guest Observing program to map the occurrence of soft x-ray emission, which is a signature of hot stellar coronae (T>10/sup 6/ K), in the cool half of the Hertzsprung Russell (H-R) diagram. We detect X-rays from F--M dwarfs and late F through early K giants, but not from the cooler giants, other than the spectroscopic binary epsilon Car (K0 II+B), or from any supergiants, other than Canopus (F0IB--II). The empirical separation of the cool half of the H-R diagram into a region where stellar soft X-ray emission is a common phenomenon, and a region where hot coronae are rare, if present at all among single stars, is similar to that found previously by Linsky and Haisch for C IV lambdalambda1548,1551 emission (Troughly-equal10/sup 5/ K) and by Stencel and Mullan for the onset of rapid mass loss in strong, cool (T< or approx. =10/sup 4/ K) stellar winds. We discuss the energy balance in the outer atmospheres of the coronal stars, the likely absorption of X-ray emission by cool winds in the ''hybrid-spectrum'' supergiants, a rotation-activity connection among the G dwarfs, and possible evolutionary origins of the structure seen in the cool half of the X-ray H-R diagram.

  7. The STAR beam energy scan phase II physics and upgrades

    Czech Academy of Sciences Publication Activity Database

    Yang, C.; Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Bielčík, J.; Bielčíková, Jana; Chaloupka, P.; Federič, Pavol; Rusňák, Jan; Rusňáková, O.; Šimko, Miroslav; Šumbera, Michal; Vértési, Robert

    2017-01-01

    Roč. 967, č. 11 (2017), s. 800-803 ISSN 0375-9474 R&D Projects: GA MŠk LG15001; GA MŠk LM2015054 Institutional support: RVO:61389005 Keywords : STAR collaboration * BES-II * detector upgrade * QCD phase diagram * physics oppotrunity Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.916, year: 2016

  8. Wave Star

    DEFF Research Database (Denmark)

    Kramer, Morten; Frigaard, Peter; Brorsen, Michael

    Nærværende rapport beskriver foreløbige hovedkonklusioner på modelforsøg udført på Aalborg Universitet, Institut for Vand, Jord og Miljøteknik med bølgeenergianlægget Wave Star i perioden 13/9 2004 til 12/11 2004.......Nærværende rapport beskriver foreløbige hovedkonklusioner på modelforsøg udført på Aalborg Universitet, Institut for Vand, Jord og Miljøteknik med bølgeenergianlægget Wave Star i perioden 13/9 2004 til 12/11 2004....

  9. Star formation in blue compact dwarf Galaxies

    Science.gov (United States)

    Ramya, S.; Prabhu, T. P.; Sahu, D. K.

    Blue compact dwarf galaxies (BCDGs) are dwarfs undergoing current burst of star formation (SF). In our work, we determine the ages of the underlying old stellar population to be ˜4 Gyr that is dominating the mass of the galaxy, underlying the current burst of SF. An intermediate population of ˜500 Myr which dominates the stellar light from the galaxy is also detected. The burst of SF at the present epoch spans ˜10 Myr as estimated from various age estimators like Hα, diagnostic diagrams and colour-colour diagrams. BCDGs undergo a burst of SF for a longer duration (of about a few 100 Myr to a Gyr) followed by a short/long quiescence. The amount of column density of localized neutral hydrogen required for the current burst to occur seems to be 10^{21} cm^{-2}. This could be the threshold required for SF. Radio continuum emission reveals that the emission is coincident with the star forming regions. The star formation rates (SFR) estimated from Hα match well with the SFR estimated using non-thermal radio emission for individual star forming regions, but are ˜6-7 times less as compared to the SFR calculated from far-IR (FIR) emission.

  10. Star Forming Galaxies and AGN Hosts: The Seagull Wings

    Science.gov (United States)

    Stasińska, Grazyna; Cid Fernandes, Roberto; Mateus, Abîlio; Sodré, Laerte; Asari, Natalia V.

    2007-05-01

    We discuss the spectral signatures of normal star forming (NSF) galaxies and of AGN hosts of and present physically motivated techniques to distinguish these two classes of galaxies. We have determined the emission line intensities for a complete sample of galaxies extracted from the Sloan Digital sky Survey, after subtracting the stellar continuum obtained from spectral synthesis. With the help of sequences of photoionization models, we explain why, in the famous [OIII]/Hbeta vs [NII]/Halpha diagram, NSF galaxies and AGN hosts form two separate sequences, which look like the open wings of a seagull. We also examine other techniques to distinguish star forming galaxies from AGN hosts. Finally, we propose a new diagnostic diagram which can be used with optical spectra of galaxies with redshifts up to z=1.3. This new diagram has also the advantage of allowing one to show all the galaxies of a sample in one plot, including passive galaxies.

  11. Drawing conformal diagrams for a fractal landscape

    Science.gov (United States)

    Winitzki, Sergei

    2005-06-01

    Generic models of cosmological inflation and the recently proposed scenarios of a recycling universe and the string theory landscape predict spacetimes whose global geometry is a stochastic, self-similar fractal. To visualize the complicated causal structure of such a universe, one usually draws a conformal (Carter-Penrose) diagram. I develop a new method for drawing conformal diagrams, applicable to arbitrary 1+1-dimensional spacetimes. This method is based on a qualitative analysis of intersecting lightrays and thus avoids the need for explicit transformations of the spacetime metric. To demonstrate the power and simplicity of this method, I present derivations of diagrams for spacetimes of varying complication. I then apply the lightray method to three different models of an eternally inflating universe (scalar-field inflation, recycling universe, and string theory landscape) involving the nucleation of nested asymptotically flat, de Sitter and/or anti-de Sitter bubbles. I show that the resulting diagrams contain a characteristic fractal arrangement of lines.

  12. Spin wave Feynman diagram vertex computation package

    Science.gov (United States)

    Price, Alexander; Javernick, Philip; Datta, Trinanjan

    Spin wave theory is a well-established theoretical technique that can correctly predict the physical behavior of ordered magnetic states. However, computing the effects of an interacting spin wave theory incorporating magnons involve a laborious by hand derivation of Feynman diagram vertices. The process is tedious and time consuming. Hence, to improve productivity and have another means to check the analytical calculations, we have devised a Feynman Diagram Vertex Computation package. In this talk, we will describe our research group's effort to implement a Mathematica based symbolic Feynman diagram vertex computation package that computes spin wave vertices. Utilizing the non-commutative algebra package NCAlgebra as an add-on to Mathematica, symbolic expressions for the Feynman diagram vertices of a Heisenberg quantum antiferromagnet are obtained. Our existing code reproduces the well-known expressions of a nearest neighbor square lattice Heisenberg model. We also discuss the case of a triangular lattice Heisenberg model where non collinear terms contribute to the vertex interactions.

  13. Solution space diagram in conflict detection scenarios

    NARCIS (Netherlands)

    Rahman, S.M.A.; Borst, C.; Mulder, M.; Van Paassen, M.M.

    2015-01-01

    This research investigates the use of Solution Space Diagram (SSD) as a measure of sector complexity and also as a predictor of performance and workload, focusing on the scenarios regarding Air Traffic Controller (ATCO)’s ability to detect future conflicts. A human-in-the-loop experiment with

  14. Diagram of a LEP superconducting cavity

    CERN Multimedia

    1991-01-01

    This diagram gives a schematic representation of the superconducting radio-frequency cavities at LEP. Liquid helium is used to cool the cavity to 4.5 degrees above absolute zero so that very high electric fields can be produced, increasing the operating energy of the accelerator. Superconducting cavities were used only in the LEP-2 phase of the accelerator, from 1996 to 2000.

  15. Phase diagram of spiking neural networks.

    Science.gov (United States)

    Seyed-Allaei, Hamed

    2015-01-01

    In computer simulations of spiking neural networks, often it is assumed that every two neurons of the network are connected by a probability of 2%, 20% of neurons are inhibitory and 80% are excitatory. These common values are based on experiments, observations, and trials and errors, but here, I take a different perspective, inspired by evolution, I systematically simulate many networks, each with a different set of parameters, and then I try to figure out what makes the common values desirable. I stimulate networks with pulses and then measure their: dynamic range, dominant frequency of population activities, total duration of activities, maximum rate of population and the occurrence time of maximum rate. The results are organized in phase diagram. This phase diagram gives an insight into the space of parameters - excitatory to inhibitory ratio, sparseness of connections and synaptic weights. This phase diagram can be used to decide the parameters of a model. The phase diagrams show that networks which are configured according to the common values, have a good dynamic range in response to an impulse and their dynamic range is robust in respect to synaptic weights, and for some synaptic weights they oscillates in α or β frequencies, independent of external stimuli.

  16. Phase Diagrams of Strongly Interacting Theories

    DEFF Research Database (Denmark)

    Sannino, Francesco

    2010-01-01

    We summarize the phase diagrams of SU, SO and Sp gauge theories as function of the number of flavors, colors, and matter representation as well as the ones of phenomenologically relevant chiral gauge theories such as the Bars-Yankielowicz and the generalized Georgi-Glashow models. We finally report...

  17. Diagrams in Second or Foreign Language Learning??!

    NARCIS (Netherlands)

    Bosveld-de Smet, Leonie; Barker-Plummer, D.; Cox, R.; Swoboda, N.

    2006-01-01

    Existing diagrams for tense use as presented in grammar surveys for foreign learners have been analyzed from a semantic theoretic point of view. The analysis reveals that the notational systems used in the diagrammatic representations of the tense rules dealt with are defective in that they can give

  18. Spatial-temporal forecasting the sunspot diagram

    Science.gov (United States)

    Covas, Eurico

    2017-09-01

    Aims: We attempt to forecast the Sun's sunspot butterfly diagram in both space (i.e. in latitude) and time, instead of the usual one-dimensional time series forecasts prevalent in the scientific literature. Methods: We use a prediction method based on the non-linear embedding of data series in high dimensions. We use this method to forecast both in latitude (space) and in time, using a full spatial-temporal series of the sunspot diagram from 1874 to 2015. Results: The analysis of the results shows that it is indeed possible to reconstruct the overall shape and amplitude of the spatial-temporal pattern of sunspots, but that the method in its current form does not have real predictive power. We also apply a metric called structural similarity to compare the forecasted and the observed butterfly cycles, showing that this metric can be a useful addition to the usual root mean square error metric when analysing the efficiency of different prediction methods. Conclusions: We conclude that it is in principle possible to reconstruct the full sunspot butterfly diagram for at least one cycle using this approach and that this method and others should be explored since just looking at metrics such as sunspot count number or sunspot total area coverage is too reductive given the spatial-temporal dynamical complexity of the sunspot butterfly diagram. However, more data and/or an improved approach is probably necessary to have true predictive power.

  19. Rainbow's Stars

    OpenAIRE

    Garattini, Remo; Mandanici, Gianluca

    2016-01-01

    In recent years, a growing interest in the equilibrium of compact astrophysical objects like white dwarf and neutron stars has been manifested. In particular, various modifications due to Planck-scale energy effects have been considered. In this paper we analyze the modification induced by gravity’s rainbow on the equilibrium configurations described by the Tolman–Oppenheimer–Volkoff (TOV) equation. Our purpose is to explore the possibility that the rainbow Planck-scale deformation of space-t...

  20. Students' different understandings of class diagrams

    Science.gov (United States)

    Boustedt, Jonas

    2012-03-01

    The software industry needs well-trained software designers and one important aspect of software design is the ability to model software designs visually and understand what visual models represent. However, previous research indicates that software design is a difficult task to many students. This article reports empirical findings from a phenomenographic investigation on how students understand class diagrams, Unified Modeling Language (UML) symbols, and relations to object-oriented (OO) concepts. The informants were 20 Computer Science students from four different universities in Sweden. The results show qualitatively different ways to understand and describe UML class diagrams and the "diamond symbols" representing aggregation and composition. The purpose of class diagrams was understood in a varied way, from describing it as a documentation to a more advanced view related to communication. The descriptions of class diagrams varied from seeing them as a specification of classes to a more advanced view, where they were described to show hierarchic structures of classes and relations. The diamond symbols were seen as "relations" and a more advanced way was seeing the white and the black diamonds as different symbols for aggregation and composition. As a consequence of the results, it is recommended that UML should be adopted in courses. It is briefly indicated how the phenomenographic results in combination with variation theory can be used by teachers to enhance students' possibilities to reach advanced understanding of phenomena related to UML class diagrams. Moreover, it is recommended that teachers should put more effort in assessing skills in proper usage of the basic symbols and models and students should be provided with opportunities to practise collaborative design, e.g. using whiteboards.

  1. A Statistical Study on Double Neutron Star Masses

    Science.gov (United States)

    Yang, Yi-yan; Zhang, Cheng-min; Wang, De-hua; Pan, Yuan-yue; Zhou, Zhu-wen

    2017-10-01

    By statistically analyzing the masses of twelve double neutron star (DNS) systems, it is concluded that the weighted mean value of DNS masses is (1.339±0.042) M⊙, where the weighted mean masses of the primary and companion stars are respectively (1.439±0.036) M⊙ and (1.239±0.020) M⊙. The mean value of the masses of primary stars is higher than that of companion stars, which indicates that the primary star may increase its mass by accretion, or the mass of its progenitor star is higher. Therefore, the physical process of supernova explosion through which the high-mass stars become NSs can be investigated hereby. Also it is found that the total masses of the DNSs span a narrow range of 2.5∼2.8 M⊙, implying that the companion stars might impact on the mass formation of DNSs. Moreover, the mass ratios of the DNSs (primaries to companions) approximate 1 (slightly larger than 1), indicating that the masses of the progenitors of primary stars are approximately equal to the masses of the progenitors of companion stars. By analyzing the distribution of the 12 DNSs in the surface magnetic field strength versus spin period (B-Ps) diagram, it is found that the surface magnetic field strength in the primary stars of the DNSs is ∼ 1010 Gs, and the spin period is ∼ 50 ms; while the two pulsars, i.e. PSR J1906+0746 and PSR J0737-3039B, are located in the region of normal pulsars in the B-Ps diagram, their surface magnetic field strength is ∼ 1012 Gs, suggesting that they might not be accelerated through accretion.

  2. A Legal Negotiatiton Support System Based on A Diagram

    Science.gov (United States)

    Nitta, Katsumi; Shibasaki, Masato; Yasumura, Yoshiaki; Hasegawa, Ryuzo; Fujita, Hiroshi; Koshimura, Miyuki; Inoue, Katsumi; Shirai, Yasuyuki; Komatsu, Hiroshi

    We present an overview of a legal negotiation support system, ANS (Argumentation based Negotiation support System). ANS consists of a user interface, three inference engines, a database of old cases, and two decision support modules. The ANS users negotiates or disputes with others via a computer network. The negotiation status is managed in the form of the negotiation diagram. The negotiation diagram is an extension of Toulmin’s argument diagram, and it contains all arguments insisted by participants. The negotiation protocols are defined as operations to the negotiation diagram. By exchanging counter arguments each other, the negotiation diagram grows up. Nonmonotonic reasoning using rule priorities are applied to the negotiation diagram.

  3. Looking for extra dimensions in compact stars

    Science.gov (United States)

    Lugones, Germán; Arbañil, José D. V.

    2017-06-01

    The properties of spherically symmetric static compact stars are studied in the Randall-Sundrum II type braneworld model assuming that the spacetime outside the star is described by a Schwarzschild metric. The integration of the stellar structure equations employing the so called causal limit equation of state (EoS) shows that the equilibrium solutions can violate the general relativistic causal limit. An analysis of the properties of hadronic and strange quark stars using standard EoSs confirm the same result: there is a branch in the mass-radius diagram that shows the typical behaviour found within the frame of General Relativity and another branch of stars that are supported against collapse by the nonlocal effects of the bulk on the brane. Stars belonging to the new branch can violate the general relativistic causal limit, may have an arbitrarily large mass, and are stable under small radial perturbations. If they exist in Nature, these objects could be hidden among the population of black hole candidates. The future observation of compact stars with masses and radii falling above the causal limit of General Relativity but below the Schwarzschild limit maybe a promising astrophysical evidence for the existence of extra dimensions.

  4. Study of star formation in NGC 1084

    Science.gov (United States)

    Ramya, S.; Sahu, D. K.; Prabhu, T. P.

    2007-10-01

    We present UBVRI broad-band, Hα narrow-band photometry of the star-forming complexes in the infrared bright galaxy NGC 1084. Results of medium-resolution spectroscopy of some of the brighter complexes are also discussed. Spectroscopic data are used to better estimate the internal reddening within the galaxy which is found to be highly variable and to calculate metallicity which is close to the solar value. A diagnostic diagram identifies the shocked regions within this galaxy. The narrow-band Hα flux and its equivalent width are used to determine the star formation rates of the complexes and the distribution of ages. Star formation rates for a few of the complexes are found to be as high as 0.5Msolar yr-1. The star-forming complexes lie in the age range 3 to 6.5 Myr. A U - B versus V - I colour-colour mixed population model created using the Starburst99 model colours is used to estimate the ages of the stellar populations present within these regions. Using this technique, it is found that the star formation in NGC 1084 has taken place in a series of short bursts over the last 40 Myr or so. It is proposed that the likely trigger for enhanced star formation is merger with a gas-rich dwarf galaxy.

  5. When stars collide

    NARCIS (Netherlands)

    Glebbeek, E.; Pols, O.R.

    2007-01-01

    When two stars collide and merge they form a new star that can stand out against the background population in a star cluster as a blue straggler. In so called collision runaways many stars can merge and may form a very massive star that eventually forms an intermediate mass blackhole. We have

  6. Star Cluster Buzzing With Pulsars

    Science.gov (United States)

    2005-01-01

    A dense globular star cluster near the center of our Milky Way Galaxy holds a buzzing beehive of rapidly-spinning millisecond pulsars, according to astronomers who discovered 21 new pulsars in the cluster using the National Science Foundation's 100-meter Robert C. Byrd Green Bank Telescope (GBT) in West Virginia. The cluster, called Terzan 5, now holds the record for pulsars, with 24, including three known before the GBT observations. Pulsar Diagram Pulsar Diagram: Click on image for more detail. "We hit the jackpot when we looked at this cluster," said Scott Ransom, an astronomer at the National Radio Astronomy Observatory in Charlottesville, VA. "Not only does this cluster have a lot of pulsars -- and we still expect to find more in it -- but the pulsars in it are very interesting. They include at least 13 in binary systems, two of which are eclipsing, and the four fastest-rotating pulsars known in any globular cluster, with the fastest two rotating nearly 600 times per second, roughly as fast as a household blender," Ransom added. Ransom and his colleagues reported their findings to the American Astronomical Society's meeting in San Diego, CA, and in the online journal Science Express. The star cluster's numerous pulsars are expected to yield a bonanza of new information about not only the pulsars themselves, but also about the dense stellar environment in which they reside and probably even about nuclear physics, according to the scientists. For example, preliminary measurements indicate that two of the pulsars are more massive than some theoretical models would allow. "All these exotic pulsars will keep us busy for years to come," said Jason Hessels, a Ph.D student at McGill University in Montreal. Globular clusters are dense agglomerations of up to millions of stars, all of which formed at about the same time. Pulsars are spinning, superdense neutron stars that whirl "lighthouse beams" of radio waves or light around as they spin. A neutron star is what is

  7. Geometry Helps to Compare Persistence Diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Kerber, Michael; Morozov, Dmitriy; Nigmetov, Arnur

    2015-11-16

    Exploiting geometric structure to improve the asymptotic complexity of discrete assignment problems is a well-studied subject. In contrast, the practical advantages of using geometry for such problems have not been explored. We implement geometric variants of the Hopcroft--Karp algorithm for bottleneck matching (based on previous work by Efrat el al.), and of the auction algorithm by Bertsekas for Wasserstein distance computation. Both implementations use k-d trees to replace a linear scan with a geometric proximity query. Our interest in this problem stems from the desire to compute distances between persistence diagrams, a problem that comes up frequently in topological data analysis. We show that our geometric matching algorithms lead to a substantial performance gain, both in running time and in memory consumption, over their purely combinatorial counterparts. Moreover, our implementation significantly outperforms the only other implementation available for comparing persistence diagrams.

  8. Modeling the Round Earth through Diagrams

    Science.gov (United States)

    Padalkar, Shamin; Ramadas, Jayashree

    Earlier studies have found that students, including adults, have problems understanding the scientifically accepted model of the Sun-Earth-Moon system and explaining day-to-day astronomical phenomena based on it. We have been examining such problems in the context of recent research on visual-spatial reasoning. Working with middle school students in India, we have developed a pedagogical sequence to build the mental model of the Earth and tried it in three schools for socially and educationally disadvantaged students. This pedagogy was developed on the basis of (1) a reading of current research in imagery and visual-spatial reasoning and (2) students' difficulties identified during the course of pretests and interviews. Visual-spatial tools such as concrete (physical) models, gestures, and diagrams are used extensively in the teaching sequence. The building of a mental model is continually integrated with drawing inferences to understand and explain everyday phenomena. The focus of this article is inferences drawn with diagrams.

  9. Designing Class Methods from Dataflow Diagrams

    Science.gov (United States)

    Shoval, Peretz; Kabeli-Shani, Judith

    A method for designing the class methods of an information system is described. The method is part of FOOM - Functional and Object-Oriented Methodology. In the analysis phase of FOOM, two models defining the users' requirements are created: a conceptual data model - an initial class diagram; and a functional model - hierarchical OO-DFDs (object-oriented dataflow diagrams). Based on these models, a well-defined process of methods design is applied. First, the OO-DFDs are converted into transactions, i.e., system processes that supports user task. The components and the process logic of each transaction are described in detail, using pseudocode. Then, each transaction is decomposed, according to well-defined rules, into class methods of various types: basic methods, application-specific methods and main transaction (control) methods. Each method is attached to a proper class; messages between methods express the process logic of each transaction. The methods are defined using pseudocode or message charts.

  10. Butterfly Diagram and Activity Cycles in HR 1099

    Science.gov (United States)

    Berdyugina, Svetlana V.; Henry, Gregory W.

    2007-04-01

    We analyze photometric data of the active RS CVn-type star HR 1099 for the years 1975-2006 with an inversion technique and reveal the nature of two activity cycles of 15-16 yr and 5.3+/-0.1 yr duration. The 16 yr cycle is related to variations of the total spot area and is coupled with the differential rotation, while the 5.3 yr cycle is caused by the symmetric redistribution of the spotted area between the opposite stellar hemispheres (flip-flop cycle). We recover long-lived active regions comprising two active longitudes that migrate in the orbital reference frame with a variable rate because of the differential rotation along with changes in the mean spot latitudes. The migration pattern is periodic with the 16 yr cycle. Combining the longitudinal migration of the active regions with a previously measured differential rotation law, we recover the first stellar butterfly diagram without an assumption about spot shapes. We find that mean latitudes of active regions at opposite longitudes change antisymmetrically in the course of the 16 yr cycle: while one active region migrates to the pole, the other approaches the equator. This suggests a precession of the global magnetic field with respect to the stellar rotational axis.

  11. Proof test diagrams for Zerodur glass-ceramic

    Science.gov (United States)

    Tucker, D. S.

    1991-01-01

    Proof test diagrams for Zerodur glass-ceramics are calculated from available fracture mechanics data. It is shown that the environment has a large effect on minimum time-to-failure as predicted by proof test diagrams.

  12. The quark-gluon-plasma phase transition diagram, Hagedorn matter and quark-gluon liquid

    OpenAIRE

    Zakout, Ismail; Greiner, Carsten

    2010-01-01

    In order to study the nuclear matter in the relativistic heavy ion collisions and the compact stars, we need the hadronic density of states for the entire ($\\mu_B-T$) phase transition diagram. We present a model for the continuous high-lying mass (and volume) spectrum density of states that fits the Hagedorn mass spectrum. This model explains the origin of the tri-critical point besides various phenomena such as the quarkyonic matter and the quark-gluon liquid. The Hagedorn mass spectrum is d...

  13. Uranium phase diagram from first principles

    Science.gov (United States)

    Yanilkin, Alexey; Kruglov, Ivan; Migdal, Kirill; Oganov, Artem; Pokatashkin, Pavel; Sergeev, Oleg

    2017-06-01

    The work is devoted to the investigation of uranium phase diagram up to pressure of 1 TPa and temperature of 15 kK based on density functional theory. First of all the comparison of pseudopotential and full potential calculations is carried out for different uranium phases. In the second step, phase diagram at zero temperature is investigated by means of program USPEX and pseudopotential calculations. Stable and metastable structures with close energies are selected. In order to obtain phase diagram at finite temperatures the preliminary selection of stable phases is made by free energy calculation based on small displacement method. For remaining candidates the accurate values of free energy are obtained by means of thermodynamic integration method (TIM). For this purpose quantum molecular dynamics are carried out at different volumes and temperatures. Interatomic potentials based machine learning are developed in order to consider large systems and long times for TIM. The potentials reproduce the free energy with the accuracy 1-5 meV/atom, which is sufficient for prediction of phase transitions. The equilibrium curves of different phases are obtained based on free energies. Melting curve is calculated by modified Z-method with developed potential.

  14. Massive basketball diagram for a thermal scalar field theory

    Science.gov (United States)

    Andersen, Jens O.; Braaten, Eric; Strickland, Michael

    2000-08-01

    The ``basketball diagram'' is a three-loop vacuum diagram for a scalar field theory that cannot be expressed in terms of one-loop diagrams. We calculate this diagram for a massive scalar field at nonzero temperature, reducing it to expressions involving three-dimensional integrals that can be easily evaluated numerically. We use this result to calculate the free energy for a massive scalar field with a φ4 interaction to three-loop order.

  15. Content Repurposing of Electrical Diagrams for Presentation in Handheld Devices

    Science.gov (United States)

    2004-12-01

    design proposed here, techniques are proposed for understanding the semantics of electrical diagrams and for partitioning the drawing images in...complex diagrams fast, given the appropriate directions. Our work attempts to explore novel ways to infer the semantics of electrical diagrams

  16. Students’ Learning Activities While Studying Biological Process Diagrams

    NARCIS (Netherlands)

    Kragten, M.; Admiraal, W.; Rijlaarsdam, G.

    2015-01-01

    Process diagrams describe how a system functions (e.g. photosynthesis) and are an important type of representation in Biology education. In the present study, we examined students’ learning activities while studying process diagrams, related to their resulting comprehension of these diagrams. Each

  17. The role of perceptual cues in matrix diagrams

    NARCIS (Netherlands)

    van der Meij, Jan; van Amelsvoort, Marije; Anjewierden, A.

    An experiment was conducted to assess whether the design of a matrix diagram influences how people study the diagram and whether this has an effect on recall of the presented information. We compared four versions of a matrix diagram on antisocial personality disorder. It consisted of four header

  18. The Classroom as Rhizome: New Strategies for Diagramming Knotted Interactions

    Science.gov (United States)

    de Freitas, Elizabeth

    2012-01-01

    This article calls attention to the unexamined role of diagrams in educational research and offers examples of alternative diagramming practices or tools that shed light on classroom interaction as a rhizomatic process. Drawing extensively on the work of Latour, Deleuze and Guattari, and Chatelet, this article explores the power of diagramming as…

  19. Stability field diagrams for Ln–O–Cl systems

    Indian Academy of Sciences (India)

    Permanent link: http://www.ias.ac.in/article/fulltext/boms/039/03/0603-0611. Keywords. Predominance area diagram; Kellogg diagram; lanthanide oxychloride; rare-earth mineral processing; thermodynamic properties. Abstract. Isothermal stability field diagrams for Ln−O−Cl systems (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, ...

  20. NGC 7419: a young open cluster with a number of very young intermediate mass pre-MS stars

    Science.gov (United States)

    Subramaniam, Annapurni; Mathew, Blesson; Bhatt, Bhuwan Chandra; Ramya, S.

    2006-08-01

    We present a photometric and spectroscopic study of the young open cluster NGC 7419, which is known to host a large number of classical Be stars for reasons not well understood. Based on CCD photometric observations of 327 stars in UBV passbands, we estimated the cluster parameters as, reddening [E(B - V)] = 1.65 +/- 0.15 mag and distance = 2900 +/- 400 pc. The turn-off age of the cluster was estimated as 25 +/- 5 Myr using isochrone fits. UBV data of the stars were combined with the JHK data from Two-Micron All-Sky Survey (2MASS) and were used to create the near-infrared (NIR) (J - H) versus (H - K) colour-colour diagram. A large fraction of stars (42 per cent) was found to have NIR excess and their location in the diagram was used to identify them as intermediate mass pre-main-sequence (MS) stars. The isochrone fits to pre-MS stars in the optical colour-magnitude diagram showed that the turn-on age of the cluster is 0.3-3 Myr. This indicates that there has been a recent episode of star formation in the vicinity of the cluster. Slitless spectra were used to identify 27 stars which showed Hα in emission in the field of the cluster, of which six are new identifications. All these stars were found to show NIR excess and are located closer to the region populated by Herbig Ae/Be stars in the (J - H) versus (H - K) diagram. Slit spectra of 25 stars were obtained in the region 3700-9000 Å. The spectral features were found to be very similar to those of Herbig Be stars. These stars were found to be more reddened than the main-sequence stars by 0.4 mag, on an average. Thus, the emission-line stars found in this cluster are more similar to the Herbig Be-type stars where the circumstellar material is the remnant of the accretion disc. We conclude that the second episode of star formation has led to the formation of a large number of Herbig Be stars as well as intermediate mass pre-MS stars in the field of NGC 7419, thus explaining the presence of emission-line stars in

  1. Comprehending 3D Diagrams: Sketching to Support Spatial Reasoning.

    Science.gov (United States)

    Gagnier, Kristin M; Atit, Kinnari; Ormand, Carol J; Shipley, Thomas F

    2017-10-01

    Science, technology, engineering, and mathematics (STEM) disciplines commonly illustrate 3D relationships in diagrams, yet these are often challenging for students. Failing to understand diagrams can hinder success in STEM because scientific practice requires understanding and creating diagrammatic representations. We explore a new approach to improving student understanding of diagrams that convey 3D relations that is based on students generating their own predictive diagrams. Participants' comprehension of 3D spatial diagrams was measured in a pre- and post-design where students selected the correct 2D slice through 3D geologic block diagrams. Generating sketches that predicated the internal structure of a model led to greater improvement in diagram understanding than visualizing the interior of the model without sketching, or sketching the model without attempting to predict unseen spatial relations. In addition, we found a positive correlation between sketched diagram accuracy and improvement on the diagram comprehension measure. Results suggest that generating a predictive diagram facilitates students' abilities to make inferences about spatial relationships in diagrams. Implications for use of sketching in supporting STEM learning are discussed. Copyright © 2016 Cognitive Science Society, Inc.

  2. State-transition diagrams for biologists.

    Science.gov (United States)

    Bersini, Hugues; Klatzmann, David; Six, Adrien; Thomas-Vaslin, Véronique

    2012-01-01

    It is clearly in the tradition of biologists to conceptualize the dynamical evolution of biological systems in terms of state-transitions of biological objects. This paper is mainly concerned with (but obviously not limited too) the immunological branch of biology and shows how the adoption of UML (Unified Modeling Language) state-transition diagrams can ease the modeling, the understanding, the coding, the manipulation or the documentation of population-based immune software model generally defined as a set of ordinary differential equations (ODE), describing the evolution in time of populations of various biological objects. Moreover, that same UML adoption naturally entails a far from negligible representational economy since one graphical item of the diagram might have to be repeated in various places of the mathematical model. First, the main graphical elements of the UML state-transition diagram and how they can be mapped onto a corresponding ODE mathematical model are presented. Then, two already published immune models of thymocyte behavior and time evolution in the thymus, the first one originally conceived as an ODE population-based model whereas the second one as an agent-based one, are refactored and expressed in a state-transition form so as to make them much easier to understand and their respective code easier to access, to modify and run. As an illustrative proof, for any immunologist, it should be possible to understand faithfully enough what the two software models are supposed to reproduce and how they execute with no need to plunge into the Java or Fortran lines.

  3. State-transition diagrams for biologists.

    Directory of Open Access Journals (Sweden)

    Hugues Bersini

    Full Text Available It is clearly in the tradition of biologists to conceptualize the dynamical evolution of biological systems in terms of state-transitions of biological objects. This paper is mainly concerned with (but obviously not limited too the immunological branch of biology and shows how the adoption of UML (Unified Modeling Language state-transition diagrams can ease the modeling, the understanding, the coding, the manipulation or the documentation of population-based immune software model generally defined as a set of ordinary differential equations (ODE, describing the evolution in time of populations of various biological objects. Moreover, that same UML adoption naturally entails a far from negligible representational economy since one graphical item of the diagram might have to be repeated in various places of the mathematical model. First, the main graphical elements of the UML state-transition diagram and how they can be mapped onto a corresponding ODE mathematical model are presented. Then, two already published immune models of thymocyte behavior and time evolution in the thymus, the first one originally conceived as an ODE population-based model whereas the second one as an agent-based one, are refactored and expressed in a state-transition form so as to make them much easier to understand and their respective code easier to access, to modify and run. As an illustrative proof, for any immunologist, it should be possible to understand faithfully enough what the two software models are supposed to reproduce and how they execute with no need to plunge into the Java or Fortran lines.

  4. Ten proposed rules of numerical diagrams

    Science.gov (United States)

    Court, Arnold

    Diagrams have been used for 3 centuries to present numerical information succinctly. Yet no complete, specific rules are available for their preparation, similar to the rules of grammar, syntax, and spelling of language. Some guidance is offered in the dozen books on graphics published in the United States in the past 40 years, and fragments appear in textbooks and manuals. But none of these is complete or consistent, and each offers at least one glaring contravention of the basic tenets of mathematics and logic.

  5. Algorithms for Disconnected Diagrams in Lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Gambhir, Arjun Singh [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Stathopoulos, Andreas [College of William and Mary, Williamsburg, VA (United States); Orginos, Konstantinos [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Yoon, Boram [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gupta, Rajan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Syritsyn, Sergey [Stony Brook Univ., NY (United States)

    2016-11-01

    Computing disconnected diagrams in Lattice QCD (operator insertion in a quark loop) entails the computationally demanding problem of taking the trace of the all to all quark propagator. We first outline the basic algorithm used to compute a quark loop as well as improvements to this method. Then, we motivate and introduce an algorithm based on the synergy between hierarchical probing and singular value deflation. We present results for the chiral condensate using a 2+1-flavor clover ensemble and compare estimates of the nucleon charges with the basic algorithm.

  6. Failure Assessment Diagram for Titanium Brazed Joints

    Science.gov (United States)

    Flom, Yury; Jones, Justin S.; Powell, Mollie M.; Puckett, David F.

    2011-01-01

    The interaction equation was used to predict failure in Ti-4V-6Al joints brazed with Al 1100 filler metal. The joints used in this study were geometrically similar to the joints in the brazed beryllium metering structure considered for the ATLAS telescope. This study confirmed that the interaction equation R(sub sigma) + R(sub Tau) = 1, where R(sub sigma) and R(sub Tau)are normal and shear stress ratios, can be used as conservative lower bound estimate of the failure criterion in ATLAS brazed joints as well as for construction of the Failure Assessment Diagram (FAD).

  7. Topological phase diagram of superconducting carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Milz, Lars; Marganska-Lyzniak, Magdalena; Grifoni, Milena [Institut I - Theoretische Physik Universitaet Regensburg (Germany)

    2016-07-01

    The topological superconducting phase diagram of superconducting carbon nanotubes is discussed. Under the assumption of a short-ranged pairing potential, there are two spin-singlet states: an s-wave and an exotic p + ip-wave that are possible because of the special structure of the honeycomb lattice. The consequences for the possible presence of Majorana edge states in carbon nanotubes are addressed. In particular, regions in the magnetic field-chemical potential plane possibly hosting localized Majorana modes are discussed.

  8. Applications of zero-suppressed decision diagrams

    CERN Document Server

    Sasao, Tsutomu

    2014-01-01

    A zero-suppressed decision diagram (ZDD) is a data structure to represent objects that typically contain many zeros. Applications include combinatorial problems, such as graphs, circuits, faults, and data mining. This book consists of four chapters on the applications of ZDDs. The first chapter by Alan Mishchenko introduces the ZDD. It compares ZDDs to BDDs, showing why a more compact representation is usually achieved in a ZDD. The focus is on sets of subsets and on sum-of-products (SOP) expressions. Methods to generate all the prime implicants (PIs), and to generate irredundant SOPs are show

  9. High temperature phase equilibria and phase diagrams

    CERN Document Server

    Kuo, Chu-Kun; Yan, Dong-Sheng

    2013-01-01

    High temperature phase equilibria studies play an increasingly important role in materials science and engineering. It is especially significant in the research into the properties of the material and the ways in which they can be improved. This is achieved by observing equilibrium and by examining the phase relationships at high temperature. The study of high temperature phase diagrams of nonmetallic systems began in the early 1900s when silica and mineral systems containing silica were focussed upon. Since then technical ceramics emerged and more emphasis has been placed on high temperature

  10. On the properties of young multiple stars

    Science.gov (United States)

    Delgado-Donate, E. J.; Clarke, C. J.; Bate, M. R.; Hodgkin, S. T.

    2004-06-01

    We present numerical results on the properties of young binary and multiple stellar systems. Our analysis is based on a series of smoothed particle hydrodynamics (SPH) +N-body simulations of the fragmentation of small molecular clouds, which fully resolve the opacity limit for fragmentation. These simulations demonstrate that multiple star formation is a major channel for star formation in turbulent flows. We have produced a statistically significant number of stable multiple systems, with component separations in the range ~1-103 au. At the end of the hydrodynamic stage (0.5 Myr), we find that ~60 per cent of stars and brown dwarfs are members of multiples systems, with about a third of these being low-mass, weakly bound outliers in wide eccentric orbits. Our results imply that in the stellar regime most stars are in multiples (~80 per cent) and that this fraction is an increasing function of primary mass. After N-body integration to 10.5 Myr, the percentage of bound objects has dropped to about 40 per cent, this decrease arising mostly from very low-mass stars and brown dwarfs that have been released into the field. Brown dwarfs are never found to be very close companions to stars (the brown dwarf desert at very small separations), but one case exists of a brown dwarf companion at intermediate separations (10 au). Our simulations can accommodate the existence of brown dwarf companions at large separations, but only if the primaries of these systems are themselves multiples. We have compared the outcome of our simulations with the properties of real stellar systems as deduced from the infrared colour-magnitude diagram of the Praesepe cluster and from spectroscopic and high-resolution imaging surveys of young clusters and the field. We find that the spread of the observed main sequence of Praesepe in the 0.4-1 Msolar range appears to require that stars are indeed commonly assembled into high-order multiple systems. Similarly, observational results from Taurus and

  11. A comparative study of linear and region based diagrams

    Directory of Open Access Journals (Sweden)

    Björn Gottfried

    2015-06-01

    Full Text Available There are two categories of objects spatial information science investigates: actual objects and their spatial properties, such as in geography, and abstract objects which are employed metaphorically, as for visual languages. A prominent example of the latter are diagrams that model knowledge of some domain. Different aspects of diagrams are of interest, including their formal properties or how human users work with them, for example, with diagrams representing sets. The literature about diagrammatic systems for the representation of sets shows a dominance of region-based diagrams like Euler circles and Venn diagrams. The effectiveness of these diagrams, however, is limited because region-based diagrams become quite complex for more then three sets. By contrast, linear diagrams are not equally prevalent but enable the representation of a greater number of sets without getting cluttered. Cluttered diagrams exhibit inherent complexity due to overlapping objects, irrelevant details, or other reasons that impinge upon their legibility. This study contrasts both types of diagrammatic systems and investigates whether the performance of users differs for both kinds of diagrams. A significant difference can be shown regarding the number of diagrams that can be drawn within a fixed period of time and regarding the number of errors made. The results indicate that linear diagrams are more effective by being more restrictive and because region based diagrams show much clutter due to overlapping, coincident, and tangentially touching contours, as well as an overwhelming number of empty zones. Linear diagrams are less prone to errors and do not suffer from clutter.

  12. Lifestyles of the Stars.

    Science.gov (United States)

    National Aeronautics and Space Administration, Cocoa Beach, FL. John F. Kennedy Space Center.

    Some general information on stars is provided in this National Aeronautics and Space Administration pamphlet. Topic areas briefly discussed are: (1) the birth of a star; (2) main sequence stars; (3) red giants; (4) white dwarfs; (5) neutron stars; (6) supernovae; (7) pulsars; and (8) black holes. (JN)

  13. Egyptian "Star Clocks"

    Science.gov (United States)

    Symons, Sarah

    Diagonal, transit, and Ramesside star clocks are tables of astronomical information occasionally found in ancient Egyptian temples, tombs, and papyri. The tables represent the motions of selected stars (decans and hour stars) throughout the Egyptian civil year. Analysis of star clocks leads to greater understanding of ancient Egyptian constellations, ritual astronomical activities, observational practices, and pharaonic chronology.

  14. The efficiency and effectiveness of utilizing diagrams in interviews: an assessment of participatory diagramming and graphic elicitation.

    Science.gov (United States)

    Umoquit, Muriah J; Dobrow, Mark J; Lemieux-Charles, Louise; Ritvo, Paul G; Urbach, David R; Wodchis, Walter P

    2008-08-08

    This paper focuses on measuring the efficiency and effectiveness of two diagramming methods employed in key informant interviews with clinicians and health care administrators. The two methods are 'participatory diagramming', where the respondent creates a diagram that assists in their communication of answers, and 'graphic elicitation', where a researcher-prepared diagram is used to stimulate data collection. These two diagramming methods were applied in key informant interviews and their value in efficiently and effectively gathering data was assessed based on quantitative measures and qualitative observations. Assessment of the two diagramming methods suggests that participatory diagramming is an efficient method for collecting data in graphic form, but may not generate the depth of verbal response that many qualitative researchers seek. In contrast, graphic elicitation was more intuitive, better understood and preferred by most respondents, and often provided more contemplative verbal responses, however this was achieved at the expense of more interview time. Diagramming methods are important for eliciting interview data that are often difficult to obtain through traditional verbal exchanges. Subject to the methodological limitations of the study, our findings suggest that while participatory diagramming and graphic elicitation have specific strengths and weaknesses, their combined use can provide complementary information that would not likely occur with the application of only one diagramming method. The methodological insights gained by examining the efficiency and effectiveness of these diagramming methods in our study should be helpful to other researchers considering their incorporation into qualitative research designs.

  15. The efficiency and effectiveness of utilizing diagrams in interviews: an assessment of participatory diagramming and graphic elicitation

    Directory of Open Access Journals (Sweden)

    Ritvo Paul G

    2008-08-01

    Full Text Available Abstract Background This paper focuses on measuring the efficiency and effectiveness of two diagramming methods employed in key informant interviews with clinicians and health care administrators. The two methods are 'participatory diagramming', where the respondent creates a diagram that assists in their communication of answers, and 'graphic elicitation', where a researcher-prepared diagram is used to stimulate data collection. Methods These two diagramming methods were applied in key informant interviews and their value in efficiently and effectively gathering data was assessed based on quantitative measures and qualitative observations. Results Assessment of the two diagramming methods suggests that participatory diagramming is an efficient method for collecting data in graphic form, but may not generate the depth of verbal response that many qualitative researchers seek. In contrast, graphic elicitation was more intuitive, better understood and preferred by most respondents, and often provided more contemplative verbal responses, however this was achieved at the expense of more interview time. Conclusion Diagramming methods are important for eliciting interview data that are often difficult to obtain through traditional verbal exchanges. Subject to the methodological limitations of the study, our findings suggest that while participatory diagramming and graphic elicitation have specific strengths and weaknesses, their combined use can provide complementary information that would not likely occur with the application of only one diagramming method. The methodological insights gained by examining the efficiency and effectiveness of these diagramming methods in our study should be helpful to other researchers considering their incorporation into qualitative research designs.

  16. Phase Diagram of Spiking Neural Networks

    Directory of Open Access Journals (Sweden)

    Hamed eSeyed-Allaei

    2015-03-01

    Full Text Available In computer simulations of spiking neural networks, often it is assumed that every two neurons of the network are connected by a probablilty of 2%, 20% of neurons are inhibitory and 80% are excitatory. These common values are based on experiments, observations. but here, I take a different perspective, inspired by evolution. I simulate many networks, each with a different set of parameters, and then I try to figure out what makes the common values desirable by nature. Networks which are configured according to the common values, have the best dynamic range in response to an impulse and their dynamic range is more robust in respect to synaptic weights. In fact, evolution has favored networks of best dynamic range. I present a phase diagram that shows the dynamic ranges of different networks of different parameteres. This phase diagram gives an insight into the space of parameters -- excitatory to inhibitory ratio, sparseness of connections and synaptic weights. It may serve as a guideline to decide about the values of parameters in a simulation of spiking neural network.

  17. Phase diagram of nucleosome core particles.

    Science.gov (United States)

    Mangenot, S; Leforestier, A; Durand, D; Livolant, F

    2003-11-07

    We present a phase diagram of the nucleosome core particle (NCP) as a function of the monovalent salt concentration and applied osmotic pressure. Above a critical pressure, NCPs stack on top of each other to form columns that further organize into multiple columnar phases. An isotropic (and in some cases a nematic) phase of columns is observed in the moderate pressure range. Under higher pressure conditions, a lamello-columnar phase and an inverse hexagonal phase form under low salt conditions, whereas a 2D hexagonal phase or a 3D orthorhombic phase is found at higher salt concentration. For intermediate salt concentrations, microphase separation occurs. The richness of the phase diagram originates from the heterogeneous distribution of charges at the surface of the NCP, which makes the particles extremely sensitive to small ionic variations of their environment, with consequences on their interactions and supramolecular organization. We discuss how the polymorphism of NCP supramolecular organization may be involved in chromatin changes in the cellular context.

  18. The Birth of Massive Stars and Star Clusters

    OpenAIRE

    Tan, Jonathan C.

    2005-01-01

    In the present-day universe, it appears that most, and perhaps all, massive stars are born in star clusters. It also appears that all star clusters contain stars drawn from an approximately universal initial mass function, so that almost all rich young star clusters contain massive stars. In this review I discuss the physical processes associated with both massive star formation and with star cluster formation. First I summarize the observed properties of star-forming gas clumps, then address...

  19. Learning from Pulsating Stars: Progress over the Last Century (Abstract)

    Science.gov (United States)

    Smith, H.

    2016-12-01

    (Abstract only) Scarcely more than a century has elapsed since it began to be widely accepted that pulsation plays an important role in the variability of stars. During that century pulsating stars have been used as tools to explore a variety of astrophysical questions, including the determination of distances to other galaxies, the testing of timescales of evolution through the HR diagram, and the identification of the ages and star formation histories of stellar populations. Among the significant early milestones along this investigative path are Henrietta Leavitt's discovery of a relation between the periods and luminosities of Cepheids, Harlow Shapley's proposal that all Cepheids are pulsating stars, and Arthur Stanley Eddington's use of the observed period change of d Cephei to constrain its power source. Today our explorations of pulsating stars are bolstered by long observational histories of brighter variables, surveys involving unprecedentedly large numbers of stars, and improved theoretical analyses. This talk will review aspects of the history and our current understanding of pulsating stars, paying particular attention to RR Lyrae, d Scuti, and Cepheid variables. Observations by AAVSO members have provided insight into several questions regarding the behavior of these stars.

  20. Newtonian view of general relativistic stars

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, A.M. [Instituto Federal do Espirito Santo (IFES), Grupo de Ciencias Ambientais e Recursos Naturais, Guarapari (Brazil); Velten, H.E.S.; Fabris, J.C. [Universidade Federal do Espirito Santo (UFES), Departamento de Fisica, Vitoria (Brazil); Salako, I.G. [Institut de Mathematiques et de Sciences Physiques (IMSP), Porto-Novo (Benin)

    2014-11-15

    Although general relativistic cosmological solutions, even in the presence of pressure, can be mimicked by using neo-Newtonian hydrodynamics, it is not clear whether there exists the same Newtonian correspondence for spherical static configurations. General relativity solutions for stars are known as the Tolman-Oppenheimer-Volkoff (TOV) equations. On the other hand, the Newtonian description does not take into account the total pressure effects and therefore cannot be used in strong field regimes. We discuss how to incorporate pressure in the stellar equilibrium equations within the neo-Newtonian framework. We compare the Newtonian, neo-Newtonian, and the full relativistic theory by solving the equilibrium equations for both three approaches and calculating the mass-radius diagrams for some simple neutron stars' equations of state. (orig.)

  1. Modified TOV in gravity’s rainbow: properties of neutron stars and dynamical stability conditions

    Energy Technology Data Exchange (ETDEWEB)

    Hendi, S.H. [Physics Department and Biruni Observatory, College of Sciences, Shiraz University,Shiraz 71454 (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM),P.O. Box 55134-441, Maragha (Iran, Islamic Republic of); Bordbar, G.H. [Physics Department and Biruni Observatory, College of Sciences, Shiraz University,Shiraz 71454 (Iran, Islamic Republic of); Center for Excellence in Astronomy and Astrophysics (CEAA-RIAAM)-Maragha,P.O. Box 55134-441, Maragha 55177-36698 (Iran, Islamic Republic of); Panah, B. Eslam [Physics Department and Biruni Observatory, College of Sciences, Shiraz University,Shiraz 71454 (Iran, Islamic Republic of); Panahiyan, S. [Physics Department and Biruni Observatory, College of Sciences, Shiraz University,Shiraz 71454 (Iran, Islamic Republic of); Physics Department, Shahid Beheshti University,Tehran 19839 (Iran, Islamic Republic of)

    2016-09-09

    In this paper, we consider a spherical symmetric metric to extract the hydrostatic equilibrium equation of stars in (3+1)-dimensional gravity’s rainbow in the presence of cosmological constant. Then, we generalize the hydrostatic equilibrium equation to d-dimensions and obtain the hydrostatic equilibrium equation for this gravity. Also, we obtain the maximum mass of neutron star using the modern equations of state of neutron star matter derived from the microscopic calculations. It is notable that, in this paper, we consider the effects of rainbow functions on the diagrams related to the mass-central mass density (M-ρ{sub c}) relation and also the mass-radius (M-R) relation of neutron star. We also study the effects of rainbow functions on the other properties of neutron star such as the Schwarzschild radius, average density, strength of gravity and gravitational redshift. Then, we apply the cosmological constant to this theory to obtain the diagrams of M-ρ{sub c} (or M-R) and other properties of these stars. Next, we investigate the dynamical stability condition for these stars in gravity’s rainbow and show that these stars have dynamical stability. We also obtain a relation between mass of neutron stars and Planck mass. In addition, we compare obtained results of this theory with the observational data.

  2. Using Eye Tracking to Investigate Semantic and Spatial Representations of Scientific Diagrams During Text-Diagram Integration

    Science.gov (United States)

    Jian, Yu-Cin; Wu, Chao-Jung

    2015-02-01

    We investigated strategies used by readers when reading a science article with a diagram and assessed whether semantic and spatial representations were constructed while reading the diagram. Seventy-one undergraduate participants read a scientific article while tracking their eye movements and then completed a reading comprehension test. Our results showed that the text-diagram referencing strategy was commonly used. However, some readers adopted other reading strategies, such as reading the diagram or text first. We found all readers who had referred to the diagram spent roughly the same amount of time reading and performed equally well. However, some participants who ignored the diagram performed more poorly on questions that tested understanding of basic facts. This result indicates that dual coding theory may be a possible theory to explain the phenomenon. Eye movement patterns indicated that at least some readers had extracted semantic information of the scientific terms when first looking at the diagram. Readers who read the scientific terms on the diagram first tended to spend less time looking at the same terms in the text, which they read after. Besides, presented clear diagrams can help readers process both semantic and spatial information, thereby facilitating an overall understanding of the article. In addition, although text-first and diagram-first readers spent similar total reading time on the text and diagram parts of the article, respectively, text-first readers had significantly less number of saccades of text and diagram than diagram-first readers. This result might be explained as text-directed reading.

  3. Subsectors, Dynkin diagrams and new generalised geometries

    Science.gov (United States)

    Strickland-Constable, Charles

    2017-08-01

    We examine how generalised geometries can be associated with a labelled Dynkin diagram built around a gravity line. We present a series of new generalised geometries based on the groups Spin( d, d) × ℝ + for which the generalised tangent space transforms in a spinor representation of the group. In low dimensions these all appear in subsectors of maximal supergravity theories. The case d = 8 provides a geometry for eight-dimensional backgrounds of M theory with only seven-form flux, which have not been included in any previous geometric construction. This geometry is also one of a series of "half-exceptional" geometries, which "geometrise" a six-form gauge field. In the appendix, we consider exam-ples of other algebras appearing in gravitational theories and give a method to derive the Dynkin labels for the "section condition" in general. We argue that generalised geometry can describe restrictions and subsectors of many gravitational theories.

  4. Linear chord diagrams on two intervals

    DEFF Research Database (Denmark)

    Andersen, Jørgen Ellegaard; Penner, Robert; Reidys, Christian

    fatgraph which has some associated genus $g\\geq 0$, and we consider the natural generating function ${\\bf C}_g^{[2]}(z)=\\sum_{n\\geq 0} {\\bf c}^{[2]}_g(n)z^n$ for the number ${\\bf c}^{[2]}_g(n)$ of distinct such chord diagrams of fixed genus $g\\geq 0$ with a given number $n\\geq 0$ of chords. We prove here...... the surprising fact that ${\\bf C}^{[2]}_g(z)=z^{2g+1} R_g^{[2]}(z)/(1-4z)^{3g+2} $ is a rational function, for $g\\geq 0$, where the polynomial $R^{[2]}_g(z)$ with degree at most $g$ has integer coefficients and satisfies $R_g^{[2]}({1\\over 4})\

  5. The Eh-pH Diagram and Its Advances

    OpenAIRE

    Hsin-Hsiung Huang

    2016-01-01

    Since Pourbaix presented Eh versus pH diagrams in his “Atlas of Electrochemical Equilibria in Aqueous Solution”, diagrams have become extremely popular and are now used in almost every scientific area related to aqueous chemistry. Due to advances in personal computers, such diagrams can now show effects not only of Eh and pH, but also of variables, including ligand(s), temperature and pressure. Examples from various fields are illustrated in this paper. Examples include geochemical formation,...

  6. Geometrical diagrams as representation and communication :a functional analytic framework

    OpenAIRE

    Alshwaikh, Jehad

    2011-01-01

    Although diagrams are considered part and parcel of mathematics, mainstream mathematicians exhibit prejudice against the use of diagrams in public. Adopting a multimodality social semiotics approach, I consider diagrams as a semiotic mode of representation and communication which enable us to construct mathematical meaning. Mathematics is a multimodal discourse, where different modes of representation and communication are used, such as (spoken and written) language, algebra...

  7. The Role of Rotation in the Evolution of Massive Stars

    Science.gov (United States)

    Heap, Sara R.; Lanz, Thierry M.

    2003-01-01

    Recent evolutionary models of massive stars predict important effects of rotation including: increasing the rate of mass loss; lowering the effective gravity; altering the evolutionary track on the Hertzsprung-Russel Diagram (HRD); extending the main-sequence phase (both on the HR diagram and in time); and mixing of CNO-processed elements up to the stellar surface. Observations suggest that rotation is a more important factor at lower metallicities because of higher initial rotational velocities and weaker winds. This makes the Small Magellanic Cloud (SMC), a low-metallicity galaxy (Z=0.2 solar Z), an excellent environment for discerning the role of rotation in massive stars. We report on a FUSE+STIS+optical spectral analysis of 17 O-type stars in the SMC, where we found an enormous range in N abundances. Three stars in the sample have the same (low) CN abundances as the nebular material out of which they formed, namely C=0.085 solar C and N=0.034 solar N. However, more than half show N approx. solar N, an enrichment factor of 30X! Such unexpectedly high levels of N have ramifications for the evolution of massive stars including precursors to supernovae. They also raise questions about the sources of nitrogen in the early universe. This study was supported in part by grants from NASA's ADP, HST GO-7437, and FUSE B134.

  8. Neutrino Processes in Neutron Stars

    Directory of Open Access Journals (Sweden)

    Kolomeitsev E.E.

    2010-10-01

    Full Text Available The aim of these lectures is to introduce basic processes responsible for cooling of neutron stars and to show how to calculate the neutrino production rate in dense strongly interacting nuclear medium. The formalism is presented that treats on equal footing one-nucleon and multiple-nucleon processes and reactions with virtual bosonic modes and condensates. We demonstrate that neutrino emission from dense hadronic component in neutron stars is subject of strong modifications due to collective effects in the nuclear matter. With the most important in-medium processes incorporated in the cooling code an overall agreement with available soft X ray data can be easily achieved. With these findings the so-called “standard” and “non-standard” cooling scenarios are replaced by one general “nuclear medium cooling scenario” which relates slow and rapid neutron star coolings to the star masses (interior densities. The lectures are split in four parts. Part I: After short introduction to the neutron star cooling problem we show how to calculate neutrino reaction rates of the most efficient one-nucleon and two-nucleon processes. No medium effects are taken into account in this instance. The effects of a possible nucleon pairing are discussed. We demonstrate that the data on neutron star cooling cannot be described without inclusion of medium effects. It motivates an assumption that masses of the neutron stars are different and that neutrino reaction rates should be strongly density dependent. Part II: We introduce the Green’s function diagram technique for systems in and out of equilibrium and the optical theorem formalism. The latter allows to perform calculations of production rates with full Green’s functions including all off-mass-shell effects. We demonstrate how this formalism works within the quasiparticle approximation. Part III: The basic concepts of the nuclear Fermi liquid approach are introduced. We show how strong

  9. Architecture Diagrams: A Graphical Language for Architecture Style Specification

    Directory of Open Access Journals (Sweden)

    Anastasia Mavridou

    2016-08-01

    Full Text Available Architecture styles characterise families of architectures sharing common characteristics. We have recently proposed configuration logics for architecture style specification. In this paper, we study a graphical notation to enhance readability and easiness of expression. We study simple architecture diagrams and a more expressive extension, interval architecture diagrams. For each type of diagrams, we present its semantics, a set of necessary and sufficient consistency conditions and a method that allows to characterise compositionally the specified architectures. We provide several examples illustrating the application of the results. We also present a polynomial-time algorithm for checking that a given architecture conforms to the architecture style specified by a diagram.

  10. Star Formation in Merging Clusters of Galaxies

    Science.gov (United States)

    Mansheim, Alison Seiler

    -wavelength data, including 102 spectral members drawn from the ORELSE survey and precise photometric redshifts, we calculate extinction-corrected star formation rates and map the specific star formation rate density of the LSS galaxies. These analyses along with an investigation of the color-magnitude properties of LSS galaxies indicate lower levels of star formation activity in the region between the merging clusters relative to the outskirts of the system. We suggest gravitational tidal forces due to the potential of merging halos may be the physical mechanisms responsible for the observed suppression of star formation in galaxies caught between the merging clusters. (Abstract shortened by ProQuest.).

  11. Oak Ridge K-25 Site Technology Logic Diagram. Volume 2, Technology Logic Diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Fellows, R.L. [ed.

    1993-02-26

    The Oak Ridge K-25 Technology Logic Diagram (TLD), a decision support tool for the K-25 Site, was developed to provide a planning document that relates envirorunental restoration and waste management problems at the Oak Ridge K-25 Site to potential technologies that can remediate these problems. The TLD technique identifies the research necessary to develop these technologies to a state that allows for technology transfer and application to waste management, remedial action, and decontamination and decommissioning activities. The TLD consists of four separate volumes-Vol. 1, Vol. 2, Vol. 3A, and Vol. 3B. Volume 1 provides introductory and overview information about the TLD. This volume, Volume 2, contains logic diagrams with an index. Volume 3 has been divided into two separate volumes to facilitate handling and use.

  12. A Deeper Look at Leo IV: Star Formation History and Extended Structure

    Science.gov (United States)

    Sand, David J.; Seth, Anil; Olszewski, Edward W.; Willman, Beth; Zaritsky, Dennis; Kallivayalil, Nitya

    2010-07-01

    We present MMT/Megacam imaging of the Leo IV dwarf galaxy in order to investigate its structure and star formation history, and to search for signs of association with the recently discovered Leo V satellite. Based on parameterized fits, we find that Leo IV is round, with epsilon fake structures into our catalog with stellar populations identical to that of Leo IV. We show that we are sensitive to stream-like structures with surface brightness μ r <~ 29.6 mag arcsec-2, and at this limit we find no stellar bridge between Leo IV (out to a radius of ~0.5 kpc) and the recently discovered, nearby satellite Leo V. Using the color-magnitude fitting package StarFISH, we determine that Leo IV is consistent with a single age (~14 Gyr), single metallicity ([Fe/H] ~ -2.3) stellar population, although we cannot rule out a significant spread in these values. We derive a luminosity of MV = -5.5 ± 0.3. Studying both the spatial distribution and frequency of Leo IV's "blue plume" stars reveals evidence for a young (~2 Gyr) stellar population which makes up ~2% of its stellar mass. This sprinkling of star formation, only detectable in this deep study, highlights the need for further imaging of the new Milky Way satellites along with theoretical work on the expected, detailed properties of these possible "reionization fossils." Observations reported here were obtained at the MMT observatory, a joint facility of the Smithsonian Institution and the University of Arizona.

  13. 'Polaris, Mark Kummerfeldt's Star, and My Star.'

    Science.gov (United States)

    McLure, John W.

    1984-01-01

    In most astronomy courses, descriptions of stars and constellations reveal the western European origins of the astronomers who named them. However, it is suggested that a study of non-western views be incorporated into astronomy curricula. Descriptions of various stars and constellations from different cultures and instructional strategies are…

  14. Medicons: toward clinical examination diagrams standardization in medical documentation

    Directory of Open Access Journals (Sweden)

    Pafitanis G

    2017-05-01

    Full Text Available Georgios Pafitanis,1 Michalis Hadjiandreou,2 Leo Withers,1 Helen Dent3 1The Royal London Hospital, Barts Health NHS Trust, London, UK; 2Barts and the London School of Medicine and Dentistry, London, UK; 3St Richard’s Hospital, Chichester, UK Background: Electronic patient records (EPRs allow efficient and accurate medical documentation. Diagrams have traditionally been used to document clinical signs in patient notes. The interpretation of these diagrams may vary among doctors across a range of specialties, but this has never been tested previously. This study investigated how common diagrams were interpreted and explored the use of digitalized diagrams – Medicons in creating a common language to be used in digital clinical examination proformas. Materials and methods: A cross-sectional survey utilizing a multiple-choice questionnaire was carried out across London hospitals. Seventeen digitalized examination diagrams were included in a multiple-choice questionnaire to test doctors’ perception and explore their opinions of diagram usage. The questionnaire was sent to junior doctors in training.Results: A total of 206 responses were received from 31 foundation year 1 trainees, 45 foundation year 2 trainees, 94 core surgical trainees and 36 core medical trainees. Diagrams were interpreted correctly, on average, 75% of the time. The majority of doctors (94% felt that diagrams facilitated the understanding of clinical examination, documentation of pathologic site (98% and improved the efficiency of documentation (89.8%. All doctors felt that diagrams may benefit overall medical care provision.Conclusion: Digitalizing signs and symptoms in EPR will enhance clinical documentation and may contribute to better patient care. New initiatives need to be employed to increase the use of diagrams – Medicons, as young doctors perceived these to improve clinical documentation. Standardized electronic proformas should be included into EPR to improve the

  15. ENERGY STAR Certified Computers

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 6.1 ENERGY STAR Program Requirements for Computers that are effective as of June 2, 2014....

  16. ENERGY STAR Certified Boilers

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 3.0 ENERGY STAR Program Requirements for Boilers that are effective as of October 1,...

  17. ENERGY STAR Certified Dehumidifiers

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 3.0 ENERGY STAR Program Requirements for Dehumidifiers that are effective as of October...

  18. ENERGY STAR Certified Displays

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 7.0 ENERGY STAR Program Requirements for Displays that are effective as of July 1, 2016....

  19. Autonomous Star Tracker Algorithms

    DEFF Research Database (Denmark)

    Betto, Maurizio; Jørgensen, John Leif; Kilsgaard, Søren

    1998-01-01

    Proposal, in response to an ESA R.f.P., to design algorithms for autonomous star tracker operations.The proposal also included the development of a star tracker breadboard to test the algorithms performances.......Proposal, in response to an ESA R.f.P., to design algorithms for autonomous star tracker operations.The proposal also included the development of a star tracker breadboard to test the algorithms performances....

  20. Star operations and Pullbacks

    OpenAIRE

    Fontana, Marco; Park, Mi Hee

    2003-01-01

    In this paper we study the star operations on a pullback of integral domains. In particular, we characterize the star operations of a domain arising from a pullback of ``a general type'' by introducing new techniques for ``projecting'' and ``lifting'' star operations under surjective homomorphisms of integral domains. We study the transfer in a pullback (or with respect to a surjective homomorphism) of some relevant classes or distinguished properties of star operations such as $v-, t-, w-, b...

  1. How Small are Small Stars Really?

    Science.gov (United States)

    2002-11-01

    measured and the results are in excellent agreement with stellar theory, indicating that our present understanding of the structure and composition of very small stars is reasonably correct . More VLTI observations are soon to follow, eventually also of even smaller objects, like Brown Dwarfs. PR Photo 27a/02 : Proxima Centauri , the nearest star known. PR Photo 27b/02 : The "Hertzsprung-Russell (HR)" diagram of stars PR Photo 27c/02 : Diameters and masses of small stars. PR Photo 27d/02 : Interferometric fringes at VLTI/VINCI of the small star GJ 887. Proxima Centauri - barely a real star ESO PR Photo 27a/02 ESO PR Photo 27a/02 [Preview - JPEG: 656 x 400 pix - 456k] [Normal - JPEG: 1312 x 800 pix - 968k] ESO PR Photo 27b/02 ESO PR Photo 27b/02 [Preview - JPEG: 400 x 478 pix - 288k] [Normal - JPEG: 800 x 956 pix - 992k] Caption : PR Photo 27a/02 shows a small sky field with the nearest known star, Proxima Centauri , close to the centre. This object is cool and red and it is brighter on the near-infrared image (in the I-filter at 900 nm) to the left than on the red image (in the R-filter at 600 nm) to the right. The rapid motion is easy to perceive. The field measures 10 x 10 arcmin 2 ; North is up and East is left. Reproduced from the Digital Sky Survey (STScI Digitized Sky Survey, (C) 1993, 1994, AURA, Inc. all rights reserved - cf. http://archive.eso.org/dss/dss). PR Photo 27b/02 is a colourful rendering of the basic Hertzsprung-Russell diagram for stars [3]. Very-low-mass stars (also known as "M dwarfs") are faint and cool and are located to the lower right of the diagonal line (the "main sequence") on which most stars lie and which corresponds to where (and when) stars burn hydrogen into helium. The present location of the Sun is also indicated. From its spectrum, Proxima Centauri ( PR Photo 27a/02 ) is classified as a "late M-dwarf star". Such stars are among the smallest and faintest, but also the most numerous in our Milky Way galaxy. PR Photo 27b/02 displays their

  2. America's Star Libraries

    Science.gov (United States)

    Lyons, Ray; Lance, Keith Curry

    2009-01-01

    "Library Journal"'s new national rating of public libraries, the "LJ" Index of Public Library Service, identifies 256 "star" libraries. It rates 7,115 public libraries. The top libraries in each group get five, four, or three Michelin guide-like stars. All included libraries, stars or not, can use their scores to learn from their peers and improve…

  3. Superfluid neutron stars

    OpenAIRE

    Langlois, David

    2001-01-01

    Neutron stars are believed to contain (neutron and proton) superfluids. I will give a summary of a macroscopic description of the interior of neutron stars, in a formulation which is general relativistic. I will also present recent results on the oscillations of neutron stars, with superfluidity explicitly taken into account, which leads in particular to the existence of a new class of modes.

  4. Do students use and understand free-body diagrams?

    Directory of Open Access Journals (Sweden)

    David Rosengrant

    2009-06-01

    Full Text Available Physics education literature recommends using multiple representations to help students understand concepts and solve problems. However, there is little research concerning why students use the representations and whether those who use them are more successful. This study addresses these questions using free-body diagrams (diagrammatic representations used in problems involving forces as a type of representation. We conducted a two-year quantitative and qualitative study of students’ use of free-body diagrams while solving physics problems. We found that when students are in a course that consistently emphasizes the use of free-body diagrams, the majority of them do use diagrams on their own to help solve exam problems even when they receive no credit for drawing the diagrams. We also found that students who draw diagrams correctly are significantly more successful in obtaining the right answer for the problem. Lastly, we interviewed students to uncover their reasons for using free-body diagrams. We found that high achieving students used the diagrams to help solve the problems and as a tool to evaluate their work while low achieving students only used representations as aids in the problem-solving process.

  5. Heuristic Diagrams as a Tool to Teach History of Science

    Science.gov (United States)

    Chamizo, Jose A.

    2012-01-01

    The graphic organizer called here heuristic diagram as an improvement of Gowin's Vee heuristic is proposed as a tool to teach history of science. Heuristic diagrams have the purpose of helping students (or teachers, or researchers) to understand their own research considering that asks and problem-solving are central to scientific activity. The…

  6. Testing the GONG ring-diagram pipeline with HMI Dopplergrams

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Kiran; Tripathy, S C; Hernandez, I Gonzalez; Kholikov, S; Hill, F; Komm, R [GONG, National Solar Observatory, Tucson, AZ 85719-4933 (United States); Bogart, R [HEPL, Stanford University, Stanford, CA 94305-4085 (United States); Haber, D, E-mail: kjain@noao.edu [JILA, University of Colorado, Boulder, CO 80309-0440 (United States)

    2011-01-01

    The GONG ring-diagram pipeline was developed to analyze GONG+ Dopplergrams in order to extract information about solar subsurface flows and has been extensively tested for this purpose. Here we present preliminary results obtained by analyzing the HMI Dopplergrams with the GONG pipeline and compare them with those obtained from the HMI ring-diagram pipeline.

  7. The Metric Lens : Visualizing Metrics and Structure on Software Diagrams

    NARCIS (Netherlands)

    Byelas, Heorhiy; Telea, Alexandru; Hassan, AE; Zaidman, A; DiPenta, M

    2008-01-01

    We present the metric lens, a new visualization of method-level code metrics atop UML class diagrams, which allows performing metric-metric and metric-structure correlations on large diagrams. Me demonstrate air interactive visualization tool in which users can quickly specify a wide palette of

  8. Diagramming Word Problems: A Strategic Approach for Instruction

    Science.gov (United States)

    van Garderen, Delinda; Scheuermann, Amy M.

    2015-01-01

    While often recommended as a strategy to use in order to solve word problems, drawing a diagram is a complex process that requires a good depth of understanding. Many middle school students with learning disabilities (LD) often struggle to use diagrams in an effective and efficient manner. This article presents information for teaching middle…

  9. Alnus as a disturbing factor in pollen diagrams

    NARCIS (Netherlands)

    Janssen, C.R.

    1959-01-01

    It is commonly accepted that percentages of pollen in a pollen diagram do not express the exact composition of forests in earlier times. This inaccuracy is due to several factors, for instance the different quantities of pollen produced by plants, the distance of transport etc. A pollen diagram

  10. RNA secondary structure diagrams for very large molecules: RNAfdl

    DEFF Research Database (Denmark)

    Hecker, Nikolai; Wiegels, Tim; Torda, Andrew E.

    2013-01-01

    There are many programs that can read the secondary structure of an RNA molecule and draw a diagram, but hardly any that can cope with 10 3 bases. RNAfdl is slow but capable of producing intersection-free diagrams for ribosome-sized structures, has a graphical user interface for adjustments and p...

  11. Lattice investigations of the QCD phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Guenther, Jana

    2016-12-15

    To understand the physics in the early universe as well as in heavy ion collisions a throughout understanding of the theory of strong interaction, quantum chromodynamics (QCD), is important. Lattice QCD provides a tool to study it from first principles. However due to the sign problem direct simulations with physical conditions are at the moment limited to zero chemical potential. In this thesis I present a circumvention of this problem. We can gain information on the QCD phase diagram and the equation of state from analytical continuation of results extracted from simulations at imaginary chemical potential. The topological susceptibility is very expensive to compute in Lattice QCD. However it provides an important ingredient for the estimation of the axion mass. The axion is a possible candidate for a dark matter, which plays in important role in the understanding of our universe. In this thesis I discuss two techniques that make it possible to determine the topological susceptibility and allow for an estimation of the axion mass. I then use this mass restrain to analyze the idea of an experiment to detect axions with a dielectric mirror.

  12. Diagram of Cell to Cell Communication

    Science.gov (United States)

    2002-01-01

    Diagram depicts the importance of cell-cell communication as central to the understanding of cancer growth and progression, the focus of the NASA bioreactor demonstration system (BDS-05) investigation. Microgravity studies will allow us to unravel the signaling and communication between these cells with the host and potential development of therapies for the treatment of cancer metastasis. The NASA Bioreactor provides a low turbulence culture environment which promotes the formation of large, three-dimensional cell clusters. Due to their high level of cellular organization and specialization, samples constructed in the bioreactor more closely resemble the original tumor or tissue found in the body. The Bioreactor is rotated to provide gentle mixing of fresh and spent nutrient without inducing shear forces that would damage the cells. The work is sponsored by NASA's Office of Biological and Physical Research. The bioreactor is managed by the Biotechnology Cell Science Program at NASA's Johnson Space Center (JSC). NASA-sponsored bioreactor research has been instrumental in helping scientists to better understand normal and cancerous tissue development. In cooperation with the medical community, the bioreactor design is being used to prepare better models of human colon, prostate, breast and ovarian tumors. Cartilage, bone marrow, heart muscle, skeletal muscle, pancreatic islet cells, liver and kidney are just a few of the normal tissues being cultured in rotating bioreactors by investigators. Credit: Emory University.

  13. Community detection by graph Voronoi diagrams

    Science.gov (United States)

    Deritei, Dávid; Lázár, Zsolt I.; Papp, István; Járai-Szabó, Ferenc; Sumi, Róbert; Varga, Levente; Ravasz Regan, Erzsébet; Ercsey-Ravasz, Mária

    2014-06-01

    Accurate and efficient community detection in networks is a key challenge for complex network theory and its applications. The problem is analogous to cluster analysis in data mining, a field rich in metric space-based methods. Common to these methods is a geometric, distance-based definition of clusters or communities. Here we propose a new geometric approach to graph community detection based on graph Voronoi diagrams. Our method serves as proof of principle that the definition of appropriate distance metrics on graphs can bring a rich set of metric space-based clustering methods to network science. We employ a simple edge metric that reflects the intra- or inter-community character of edges, and a graph density-based rule to identify seed nodes of Voronoi cells. Our algorithm outperforms most network community detection methods applicable to large networks on benchmark as well as real-world networks. In addition to offering a computationally efficient alternative for community detection, our method opens new avenues for adapting a wide range of data mining algorithms to complex networks from the class of centroid- and density-based clustering methods.

  14. Planar diagrams and Calabi-Yau spaces

    CERN Document Server

    Ferrari, F

    2003-01-01

    Large N geometric transitions and the Dijkgraaf-Vafa conjecture suggest a deep relationship between the sum over planar diagrams and Calabi-Yau threefolds. We explore this correspondence in details, explaining how to construct the Calabi-Yau for a large class of M-matrix models, and how the geometry encodes the correlators. We engineer in particular two-matrix theories with potentials W(X,Y) that reduce to arbitrary functions in the commutative limit. We apply the method to calculate all correlators and in models of the form W(X,Y)=V(X)+U(Y)-XY and W(X,Y)=V(X)+YU(Y^{2})+XY^{2}. The solution of the latter example was not known, but when U is a constant we are able to solve the loop equations, finding a precise match with the geometric approach. We also discuss special geometry in multi-matrix models, and we derive an important property, the entanglement of eigenvalues, governing the expansion around classical vacua for which the matrices do not commute.

  15. Efficient computation of clipped Voronoi diagram for mesh generation

    KAUST Repository

    Yan, Dongming

    2013-04-01

    The Voronoi diagram is a fundamental geometric structure widely used in various fields, especially in computer graphics and geometry computing. For a set of points in a compact domain (i.e. a bounded and closed 2D region or a 3D volume), some Voronoi cells of their Voronoi diagram are infinite or partially outside of the domain, but in practice only the parts of the cells inside the domain are needed, as when computing the centroidal Voronoi tessellation. Such a Voronoi diagram confined to a compact domain is called a clipped Voronoi diagram. We present an efficient algorithm to compute the clipped Voronoi diagram for a set of sites with respect to a compact 2D region or a 3D volume. We also apply the proposed method to optimal mesh generation based on the centroidal Voronoi tessellation. Crown Copyright © 2011 Published by Elsevier Ltd. All rights reserved.

  16. A comparison of two approaches for solving unconstrained influence diagrams

    DEFF Research Database (Denmark)

    Ahlmann-Ohlsen, Kristian S.; Jensen, Finn V.; Nielsen, Thomas Dyhre

    2009-01-01

    Influence diagrams and decision trees represent the two most common frameworks for specifying and solving decision problems. As modeling languages, both of these frameworks require that the decision analyst specifies all possible sequences of observations and decisions (in influence diagrams......, this requirement corresponds to the constraint that the decisions should be temporarily linearly ordered). Recently, the unconstrained influence diagram was proposed to address this drawback. In this framework, we may have a partial ordering of the decisions, and a solution to the decision problem therefore...... consists not only of a decision policy for the various decisions, but also of a conditional specification of what to do next. Relative to the complexity of solving an influence diagram, finding a solution to an unconstrained influence diagram may be computationally very demanding w.r.t. both time and space...

  17. Analysis of Sequence Diagram Layout in Advanced UML Modelling Tools

    Directory of Open Access Journals (Sweden)

    Ņikiforova Oksana

    2016-05-01

    Full Text Available System modelling using Unified Modelling Language (UML is the task that should be solved for software development. The more complex software becomes the higher requirements are stated to demonstrate the system to be developed, especially in its dynamic aspect, which in UML is offered by a sequence diagram. To solve this task, the main attention is devoted to the graphical presentation of the system, where diagram layout plays the central role in information perception. The UML sequence diagram due to its specific structure is selected for a deeper analysis on the elements’ layout. The authors research represents the abilities of modern UML modelling tools to offer automatic layout of the UML sequence diagram and analyse them according to criteria required for the diagram perception.

  18. Developing Tool Support for Problem Diagrams with CPN and VDM++

    DEFF Research Database (Denmark)

    Tjell, Simon; Lassen, Kristian Bisgaard

    2008-01-01

    the structure and parallel decomposition of a software development problem while the CPN model is used for formal specification of assumed and desired behaviour of the domains found in the Problem Diagrams. After generation, the CPN model will be manually refined and during this process, it is repeatedly......In this paper, we describe ongoing work on the development of tool support for formal description of domains found in Problem Diagrams. The purpose of the tool is to handle the generation of a CPN model based on a collection of Problem Diagrams. The Problem Diagrams are used for representing...... validated against structural constraints found in the Problem Diagrams. The generation and validation algorithms as well as the definitions of the two modeling formalisms are specified using VDM++....

  19. Safety-barrier diagrams as a safety management tool

    DEFF Research Database (Denmark)

    Duijm, Nijs Jan

    2009-01-01

    Networks is discussed. Important advantages of safety-barrier diagrams as compared to other graphical risk-analysis methods are, firstly, the relative simplicity that supports communication with non-expert stakeholders and, secondly, the focus on deliberately inserted safety systems that supports......Safety-barrier diagrams and “bow-tie” diagrams have become popular methods in risk analysis and safety management. This paper describes the syntax and principles for constructing consistent and valid safety-barrier diagrams. The latter's relation to other methods such as fault trees and Bayesian...... the management and maintenance of these systems. Safety-barrier diagrams provide a useful framework for an electronic data structure that integrates information from risk analysis with operational safety management....

  20. Robust automatic photometry of local galaxies from SDSS. Dissecting the color magnitude relation with color profiles

    Science.gov (United States)

    Consolandi, Guido; Gavazzi, Giuseppe; Fumagalli, Michele; Dotti, Massimo; Fossati, Matteo

    2016-06-01

    We present an automatic procedure to perform reliable photometry of galaxies on SDSS images. We selected a sample of 5853 galaxies in the Coma and Virgo superclusters. For each galaxy, we derive Petrosian g and I magnitudes, surface brightness and color profiles. Unlike the SDSS pipeline, our procedure is not affected by the well known shredding problem and efficiently extracts Petrosian magnitudes for all galaxies. Hence we derived magnitudes even from the population of galaxies missed by the SDSS which represents ~25% of all local supercluster galaxies and ~95% of galaxies with g inner (r ≤ 1 kpc), intermediate (0.2RPet ≤ r ≤ 0.3RPet) and outer, disk-dominated (r ≥ 0.35RPet)) zone; and (II), we compute template color profiles, discussing the dependences of the templates on the galaxy masses and on their morphological type. The two analyses consistently lead to a picture where elliptical galaxies show no color gradients, irrespective of their masses. Spirals, instead, display a steeper gradient in their color profiles with increasing mass, which is consistent with the growing relevance of a bulge and/or a bar component above 1010 M⊙. Full Table A.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/591/A38

  1. The Color-Magnitude Distribution of Hilda Asteroids: Comparison with Jupiter Trojans

    Science.gov (United States)

    Wong, Ian; Brown, Michael E.

    2017-02-01

    Current models of solar system evolution posit that the asteroid populations in resonance with Jupiter are comprised of objects scattered inward from the outer solar system during a period of dynamical instability. In this paper, we present a new analysis of the absolute magnitude and optical color distribution of Hilda asteroids, which lie in 3:2 mean-motion resonance with Jupiter, with the goal of comparing the bulk properties with previously published results from an analogous study of Jupiter Trojans. We report an updated power-law fit of the Hilda magnitude distribution through H = 14. Using photometric data listed in the Sloan Moving Object Catalog, we confirm the previously reported strong bimodality in visible spectral slope distribution, indicative of two subpopulations with differing surface compositions. When considering collisional families separately, we find that collisional fragments follow a unimodal color distribution with spectral slope values consistent with the bluer of the two subpopulations. The color distributions of Hildas and Trojans are comparable and consistent with a scenario in which the color bimodality in both populations developed prior to emplacement into their present-day locations. We propose that the shallower magnitude distribution of the Hildas is a result of an initially much larger Hilda population, which was subsequently depleted as smaller bodies were preferentially ejected from the narrow 3:2 resonance via collisions. Altogether, these observations provide a strong case supporting a common origin for Hildas and Trojans as predicted by current dynamical instability theories of solar system evolution.

  2. Rotating Stars in Relativity

    Directory of Open Access Journals (Sweden)

    Stergioulas Nikolaos

    2003-01-01

    Full Text Available Rotating relativistic stars have been studied extensively in recent years, both theoretically and observationally, because of the information they might yield about the equation of state of matter at extremely high densities and because they are considered to be promising sources of gravitational waves. The latest theoretical understanding of rotating stars in relativity is reviewed in this updated article. The sections on the equilibrium properties and on the nonaxisymmetric instabilities in f-modes and r-modes have been updated and several new sections have been added on analytic solutions for the exterior spacetime, rotating stars in LMXBs, rotating strange stars, and on rotating stars in numerical relativity.

  3. Rotating Stars in Relativity

    Directory of Open Access Journals (Sweden)

    Nikolaos Stergioulas

    1998-06-01

    Full Text Available Because of the information they can yield about the equation of state of matter at extremely high densities and because they are one of the more possible sources of detectable gravitational waves, rotating relativistic stars have been receiving significant attention in recentyears. We review the latest theoretical and numerical methods for modeling rotating relativistic stars, including stars with a strong magnetic field and hot proto-neutron stars. We also review nonaxisymmetric oscillations and instabilities in rotating stars and summarize the latest developments regarding the gravitational wave-driven (CFS instability in both polar and axial quasi-normal modes.

  4. Nuclear physics of stars

    CERN Document Server

    Iliadis, Christian

    2015-01-01

    Most elements are synthesized, or ""cooked"", by thermonuclear reactions in stars. The newly formed elements are released into the interstellar medium during a star's lifetime, and are subsequently incorporated into a new generation of stars, into the planets that form around the stars, and into the life forms that originate on the planets. Moreover, the energy we depend on for life originates from nuclear reactions that occur at the center of the Sun. Synthesis of the elements and nuclear energy production in stars are the topics of nuclear astrophysics, which is the subject of this book

  5. The Fundamental Properties of Young Stars

    Science.gov (United States)

    Czekala, Ian

    specifically addresses the common problem of mismatches in model spectral line strengths (with respect to data) due to intrinsic model imperfections (e.g., in the atomic/molecular databases or opacity prescriptions) by developing a novel local covariance kernel formalism that identifies and self-consistently downweights pathological spectral line "outliers." We demonstrate some salient features of the framework by fitting the high resolution V-band spectrum of WASP-14, an F5 dwarf with a transiting exoplanet, and the moderate resolution K-band spectrum of Gliese 51, an M5 field dwarf. Direct spectroscopic inference provides one means to avoid the systematic error that results from the uncertain spectral type--effective temperature scale for low mass pre-main sequence stars when placing a star on the Hertzsprung Russell diagram. Lastly, we discuss recent progress in measuring the masses of a large sample of single pre-main sequence stars observed with the Submillimeter Array, which will double the number of disk-based dynamical mass estimates of pre-main sequence stars. With ALMA, the disk-based technique holds enormous promise to become the primary means of stellar mass for statistically large samples of pre-main sequence stars, ushering in a new era of high precision in star and planet formation studies.

  6. Collaborative diagramming during problem based learning in medical education: Do computerized diagrams support basic science knowledge construction?

    Science.gov (United States)

    De Leng, Bas; Gijlers, Hannie

    2015-05-01

    To examine how collaborative diagramming affects discussion and knowledge construction when learning complex basic science topics in medical education, including its effectiveness in the reformulation phase of problem-based learning. Opinions and perceptions of students (n = 70) and tutors (n = 4) who used collaborative diagramming in tutorial groups were collected with a questionnaire and focus group discussions. A framework derived from the analysis of discourse in computer-supported collaborative leaning was used to construct the questionnaire. Video observations were used during the focus group discussions. Both students and tutors felt that collaborative diagramming positively affected discussion and knowledge construction. Students particularly appreciated that diagrams helped them to structure knowledge, to develop an overview of topics, and stimulated them to find relationships between topics. Tutors emphasized that diagramming increased interaction and enhanced the focus and detail of the discussion. Favourable conditions were the following: working with a shared whiteboard, using a diagram format that facilitated distribution, and applying half filled-in diagrams for non-content expert tutors and\\or for heterogeneous groups with low achieving students. The empirical findings in this study support the findings of earlier more descriptive studies that diagramming in a collaborative setting is valuable for learning complex knowledge in medicine.

  7. Spectrophotometry of Symbiotic Stars

    Science.gov (United States)

    Boyd, David

    2017-06-01

    Symbiotic stars are fascinating objects - complex binary systems comprising a cool red giant star and a small hot object, often a white dwarf, both embedded in a nebula formed by a wind from the giant star. UV radiation from the hot star ionises the nebula producing a range of emission lines. These objects have composite spectra with contributions from both stars plus the nebula and these spectra can change on many timescales. Being moderately bright, they lend themselves well to amateur spectroscopy. This paper describes the symbiotic star phenomenon, shows how spectrophotometry can be used to extract astrophysically useful information about the nature of these systems, and gives results for three symbiotic stars based on the author's observations.

  8. The Eh-pH Diagram and Its Advances

    Directory of Open Access Journals (Sweden)

    Hsin-Hsiung Huang

    2016-01-01

    Full Text Available Since Pourbaix presented Eh versus pH diagrams in his “Atlas of Electrochemical Equilibria in Aqueous Solution”, diagrams have become extremely popular and are now used in almost every scientific area related to aqueous chemistry. Due to advances in personal computers, such diagrams can now show effects not only of Eh and pH, but also of variables, including ligand(s, temperature and pressure. Examples from various fields are illustrated in this paper. Examples include geochemical formation, corrosion and passivation, precipitation and adsorption for water treatment and leaching and metal recovery for hydrometallurgy. Two basic methods were developed to construct an Eh-pH diagram concerning the ligand component(s. The first method calculates and draws a line between two adjacent species based on their given activities. The second method performs equilibrium calculations over an array of points (500 × 800 or higher are preferred, each representing one Eh and one pH value for the whole system, then combines areas of each dominant species for the diagram. These two methods may produce different diagrams. The fundamental theories, illustrated results, comparison and required conditions behind these two methods are presented and discussed in this paper. The Gibbs phase rule equation for an Eh-pH diagram was derived and verified from actual plots. Besides indicating the stability area of water, an Eh-pH diagram normally shows only half of an overall reaction. However, merging two or more related diagrams together reveals more clearly the possibility of the reactions involved. For instance, leaching of Au with cyanide followed by cementing Au with Zn (Merrill-Crowe process can be illustrated by combining Au-CN and Zn-CN diagrams together. A second example of the galvanic conversion of chalcopyrite can be explained by merging S, Fe–S and Cu–Fe–S diagrams. The calculation of an Eh-pH diagram can be extended easily into another dimension, such

  9. Oak Ridge National Laboratory Technology Logic Diagram. Volume 2, Technology Logic Diagram: Part B, Remedial Action

    Energy Technology Data Exchange (ETDEWEB)

    1993-09-01

    The Oak Ridge National Laboratory Technology Logic Diagram (TLD) was developed to provide a decision support tool that relates environmental restoration (ER) and waste management (WM) problems at Oak Ridge National Laboratory (ORNL) to potential technologies that can remediate these problems. The TLD identifies the research, development, demonstration, testing, and evaluation needed to develop these technologies to a state that allows technology transfer and application to decontamination and decommissioning (D&D), remedial action (RA), and WM activities. The TLD consists of three fundamentally separate volumes: Vol. 1 (Technology Evaluation), Vol. 2 (Technology Logic Diagram), and Vol. 3 (Technology Evaluation Data Sheets). Part A of Vols. 1. and 2 focuses on D&D. Part B of Vols. 1 and 2 focuses on the RA of contaminated facilities. Part C of Vols. 1 and 2 focuses on WM. Each part of Vol. 1 contains an overview of the TLD, an explanation of the program-specific responsibilities, a review of identified technologies, and the rankings of remedial technologies. Volume 2 (Pts. A, B, and C) contains the logic linkages among EM goals, environmental problems, and the various technologies that have the potential to solve these problems. Volume 3 (Pts. A, B, and C) contains the TLD data sheets. Remedial action is the focus of Vol. 2, Pt. B, which has been divided into the three necessary subelements of the RA: characterization, RA, and robotics and automation. Each of these sections address general ORNL problems, which are then broken down by problem area/constituents and linked to potential remedial technologies. The diagrams also contain summary information about a technology`s status, its science and technology needs, and its implementation needs.

  10. Forest Dynamics at the Missouri Ozark Forest Ecosystem Project viewed through stocking diagrams

    Science.gov (United States)

    David R. Larsen; John M. Kabrick; Stephen R. Shifley; Randy G. Jensen

    2017-01-01

    Stocking diagrams come in two forms, the Gingrich diagram and the density management diagram. While they both present the same information about a forest stand, they each provide a different perspective on the data being displayed. Density management diagrams have been around since the 1930s and the Gingrich diagram has been around since the 1960s, but applications of...

  11. Absolute Nuv magnitudes of Gaia DR1 astrometric stars and a search for hot companions in nearby systems

    Science.gov (United States)

    Makarov, V. V.

    2017-10-01

    Accurate parallaxes from Gaia DR1 (TGAS) are combined with GALEX visual Nuv magnitudes to produce absolute Mnuv magnitudes and an ultraviolet HR diagram for a large sample of astrometric stars. A functional fit is derived of the lower envelope main sequence of the nearest 1403 stars (distance white dwarfs, stars younger than the Pleiades, or, most likely, tight interacting binaries of the BY Dra-type. A separate collection of 40 stars with precise trigonometric parallaxes and Nuv-G colors bluer than 2 mag is presented. It includes several known novae, white dwarfs, and binaries with hot subdwarf (sdOB) components, but most remain unexplored.

  12. SDSS IV MaNGA - spatially resolved diagnostic diagrams: a proof that many galaxies are LIERs

    Science.gov (United States)

    Belfiore, Francesco; Maiolino, Roberto; Maraston, Claudia; Emsellem, Eric; Bershady, Matthew A.; Masters, Karen L.; Yan, Renbin; Bizyaev, Dmitry; Boquien, Médéric; Brownstein, Joel R.; Bundy, Kevin; Drory, Niv; Heckman, Timothy M.; Law, David R.; Roman-Lopes, Alexandre; Pan, Kaike; Stanghellini, Letizia; Thomas, Daniel; Weijmans, Anne-Marie; Westfall, Kyle B.

    2016-09-01

    We study the spatially resolved excitation properties of the ionized gas in a sample of 646 galaxies using integral field spectroscopy data from the Sloan Digital Sky Survey IV Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) programme. Making use of Baldwin-Philips-Terlevich diagnostic diagrams we demonstrate the ubiquitous presence of extended (kpc scale) low-ionization emission-line regions (LIERs) in both star-forming and quiescent galaxies. In star-forming galaxies LIER emission can be associated with diffuse ionized gas, most evident as extraplanar emission in edge-on systems. In addition, we identify two main classes of galaxies displaying LIER emission: `central LIER' (cLIER) galaxies, where central LIER emission is spatially extended, but accompanied by star formation at larger galactocentric distances, and `extended LIER' (eLIER) galaxies, where LIER emission is extended throughout the whole galaxy. In eLIER and cLIER galaxies, LIER emission is associated with radially flat, low H α equivalent width of line emission (<3 Å) and stellar population indices demonstrating the lack of young stellar populations, implying that line emission follows tightly the continuum due to the underlying old stellar population. The H α surface brightness radial profiles are always shallower than 1/r2 and the line ratio [O III] λ5007/[O II] λλ3727,29 (a tracer of the ionization parameter of the gas) shows a flat gradient. This combined evidence strongly supports the scenario in which LIER emission is not due to a central point source but to diffuse stellar sources, the most likely candidates being hot, evolved (post-asymptotic giant branch) stars. Shocks are observed to play a significant role in the ionization of the gas only in rare merging and interacting systems.

  13. Studies of the QCD Phase Diagram with Heavy-Ion Collisions at J-PARC

    Science.gov (United States)

    Sako, Hiroyuki

    To clarify phase structures in the QCD phase diagram is an ultimate goal of heavy-ion collision experiments. Studies of internal structures of neutron stars are also one of the most important topics of nuclear physics since the discovery of neutron stars with two-solar mass. For these physics goals, J-PARC heavy-ion project (J-PARC-HI) has been proposed, where extremely dense matter with 5-10 times the normal nuclear density will be created. Heavy-ion beams up to Uranium will be accelerated to 1-19 AGeV/c, with the designed world's highest beam rate of 1011 Hz. The acceleration of such high-rate beams can be realized by a new heavy-ion linac and a new booster ring, in addition to the existing 3-GeV and 50-GeV proton synchrotrons. To study the above physics goals, following physics observables will be measured in extremely high statistics expected in J-PARC-HI. To search for the critical point, high-order event-by-event fluctuations of conserved charges such as a net-baryon number, an electric charge number, and a strangeness number will be measured. To study the chiral symmetry restoration, dilepton spectra from light vector meson decays will be measured. Also, collective flows, particle correlations will be measured to study the equation of state and hyperon-hyperon and hyperon-nucleon interactions related to neutron stars. Strange quark matter (strangelet) and multi-strangeness hypernuclei will be searched for which may be related directly to the matter constituting the neutron star core. In this work, the physics goals, the experimental design, and expected physics results of J-PARC-HI will be discussed.

  14. Dynamical evolution of viscous disks around be stars. II. Polarimetry

    Energy Technology Data Exchange (ETDEWEB)

    Haubois, X. [LESIA, Observatoire de Paris, CNRS UMR 8109, UPMC, Université Paris Diderot, 5 place Jules Janssen, F-92195 Meudon (France); Mota, B. C.; Carciofi, A. C.; Bednarski, D. [Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão 1226, Cidade Universitária, São Paulo, SP 05508-090 (Brazil); Draper, Z. H. [Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2 (Canada); Wisniewski, J. P. [H. L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks St Norman, OK 73019 (United States); Rivinius, Th., E-mail: xavier.haubois@obspm.fr [European Organisation for Astronomical Research in the Southern Hemisphere, Casilla 19001, Santiago 19 (Chile)

    2014-04-10

    Be stars exhibit variability for a great number of observables. Putting the pieces of the disk dynamics together is not an easy task and requires arduous modeling before achieving a good fit to the observational data. In order to guide the modeling process and make it more efficient, it is very instructive to investigate reference dynamical cases. This paper focuses on continuum polarimetric quantities and is the second of a series that aims to demonstrate the capacity of deriving the dynamical history and fundamental parameters of a classical Be star through follow-up of various observables. After a detailed study of the different opacities at play in the formation of polarized spectra, we investigate predictions of polarimetric observables in the continuum for different dynamical scenarios. Our models are based on a coupling of a hydrodynamic viscous decretion simulations in a disk and a three-dimensional non-LTE radiative transfer code. Through introduction of the polarization color diagram (PCD), we show that certain combinations of polarimetric observables exhibit features that are characteristic of a mass-loss history. This diagram also enables estimates of fundamental parameters such as the inclination angle, disk density scale, and the α viscous diffusion parameter. We present the PCD as a powerful diagnosis tool to track the dynamical phases of a Be star, such as disk build-up, dissipation, periodic, and episodic outbursts. Finally, we confront our models with observations of four Be stars that exhibited long-term polarimetric activity.

  15. Classical Process diagrams and Service oriented Architecture

    Directory of Open Access Journals (Sweden)

    Milan Mišovič

    2013-01-01

    services communicate with each other. The communication can involve either simple data or it could two or more services coordinating some activity. From the above mentioned we can pronounce a brief description of SOA. “SOA is an architectural style for consistency of business process logic and service architecture of the target software.”It is a complex of means for solution of special analysis, design, and integration of enterprise applications based on the use of enterprise services. The service solutions of the classic business process logic are, of course, based on the application of at least seven key principles of SOA (free relations, service contract, autonomy, abstraction, reusing, composition, no states. Key attributes of SOA are verbally described in (Erl, 2006. They are so important that a separate article should be devoted to their nature and formalization. On the other hand, there is also clear that each service solution of business logic should respect the principles published in SOA Manifesto, 2009, which are essentially derived from the key principles of SOA.In many publications there are given the SOA reference models usually composed of several layers (presentation layer, business process layer, composite services layer, application layer giving a meta idea of SOA implementation. Perfect knowledge of the business process logic is a necessary condition for the development of a proper service solution. The different types of business processes should be described in the necessary details and contexts.Interestingly, the SOA paradigm does not provide its own method of finding and describing business processes by giving a layered transparent business process diagram. On the other hand, the methodology provides deep understanding of not only the characteristics of services, but also their functionality and implementation of the key principles of SOA (Erl, 2006.Let us assume that the required process diagrams can be achieved by using some of the advanced

  16. Homotopy theory of modules over diagrams of rings

    Directory of Open Access Journals (Sweden)

    J. P. C. Greenlees

    2014-09-01

    Full Text Available Given a diagram of rings, one may consider the category of modules over them. We are interested in the homotopy theory of categories of this type: given a suitable diagram of model categories ℳ( (as runs through the diagram, we consider the category of diagrams where the object ( at comes from ℳ(. We develop model structures on such categories of diagrams and Quillen adjunctions that relate categories based on different diagram shapes. Under certain conditions, cellularizations (or right Bousfield localizations of these adjunctions induce Quillen equivalences. As an application we show that a cellularization of a category of modules over a diagram of ring spectra (or differential graded rings is Quillen equivalent to modules over the associated inverse limit of the rings. Another application of the general machinery here is given in work by the authors on algebraic models of rational equivariant spectra. Some of this material originally appeared in the preprint “An algebraic model for rational torus-equivariant stable homotopy theory”, arXiv:1101.2511, but has been generalized here.

  17. Penguin-like diagrams from the standard model

    Energy Technology Data Exchange (ETDEWEB)

    Ping, Chia Swee [High Impact Research, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2015-04-24

    The Standard Model is highly successful in describing the interactions of leptons and quarks. There are, however, rare processes that involve higher order effects in electroweak interactions. One specific class of processes is the penguin-like diagram. Such class of diagrams involves the neutral change of quark flavours accompanied by the emission of a gluon (gluon penguin), a photon (photon penguin), a gluon and a photon (gluon-photon penguin), a Z-boson (Z penguin), or a Higgs-boson (Higgs penguin). Such diagrams do not arise at the tree level in the Standard Model. They are, however, induced by one-loop effects. In this paper, we present an exact calculation of the penguin diagram vertices in the ‘tHooft-Feynman gauge. Renormalization of the vertex is effected by a prescription by Chia and Chong which gives an expression for the counter term identical to that obtained by employing Ward-Takahashi identity. The on-shell vertex functions for the penguin diagram vertices are obtained. The various penguin diagram vertex functions are related to one another via Ward-Takahashi identity. From these, a set of relations is obtained connecting the vertex form factors of various penguin diagrams. Explicit expressions for the gluon-photon penguin vertex form factors are obtained, and their contributions to the flavor changing processes estimated.

  18. Massive Star and Star Cluster Formation

    OpenAIRE

    Tan, Jonathan C.

    2006-01-01

    I review the status of massive star formation theories: accretion from collapsing, massive, turbulent cores; competitive accretion; and stellar collisions. I conclude the observational and theoretical evidence favors the first of these models. I then discuss: the initial conditions of star cluster formation as traced by infrared dark clouds; the cluster formation timescale; and comparison of the initial cluster mass function in different galactic environments.

  19. CCD Photometry of Field RR Lyrae Stars. I. Period Changes of SV ERI and XX and

    Directory of Open Access Journals (Sweden)

    Jong-Myung Joo

    1996-06-01

    Full Text Available CCD time series photometry was performed for two Oosterhoff type II± field RR Lyrae stars, SV Eri and XX And, to construct light curves in B and V bands. The maximum light times from our observations were combined with those in the literature to construct phase shift diagrams, from which we determined the period change rates β. We obtained large positive period change rates for these stars, which are expected from current evolutionary models if these stars are evolving rapidly from blue to red toward the end of core helium burning phase.

  20. The absence of the 10 um silicate feature in the isolated Herbig Ae star HD 100453

    OpenAIRE

    Meeus, G.; Bouwman, J.; Dominik, C.; Waters, L. B. F. M.; de Koter, A.

    2002-01-01

    We analyse the optical and IR spectra, as well as the spectral energy distribution (UV to mm) of the candidate Herbig Ae star HD100453. This star is particular, as it shows an energy distribution similar to that of other isolated Herbig Ae/Be stars (HAEBEs), but unlike most of them, it does not have a silicate emission feature at 10 um, as is shown in Meeus (2001). We confirm the HAEBE nature of HD100453 through an analysis of its optical spectrum and derived location in the H-R diagram. The ...

  1. Star-Branched Polymers (Star Polymers)

    KAUST Repository

    Hirao, Akira

    2015-09-01

    The synthesis of well-defined regular and asymmetric mixed arm (hereinafter miktoarm) star-branched polymers by the living anionic polymerization is reviewed in this chapter. In particular, much attention is being devoted to the synthetic development of miktoarm star polymers since 2000. At the present time, the almost all types of multiarmed and multicomponent miktoarm star polymers have become feasible by using recently developed iterative strategy. For example, the following well-defined stars have been successfully synthesized: 3-arm ABC, 4-arm ABCD, 5-arm ABCDE, 6-arm ABCDEF, 7-arm ABCDEFG, 6-arm ABC, 9-arm ABC, 12-arm ABC, 13-arm ABCD, 9-arm AB, 17-arm AB, 33-arm AB, 7-arm ABC, 15-arm ABCD, and 31-arm ABCDE miktoarm star polymers, most of which are quite new and difficult to synthesize by the end of the 1990s. Several new specialty functional star polymers composed of vinyl polymer segments and rigid rodlike poly(acetylene) arms, helical polypeptide, or helical poly(hexyl isocyanate) arms are introduced.

  2. Dark stars: a review.

    Science.gov (United States)

    Freese, Katherine; Rindler-Daller, Tanja; Spolyar, Douglas; Valluri, Monica

    2016-06-01

    Dark stars are stellar objects made (almost entirely) of hydrogen and helium, but powered by the heat from dark matter annihilation, rather than by fusion. They are in hydrostatic and thermal equilibrium, but with an unusual power source. Weakly interacting massive particles (WIMPs), among the best candidates for dark matter, can be their own antimatter and can annihilate inside the star, thereby providing a heat source. Although dark matter constitutes only [Formula: see text]0.1% of the stellar mass, this amount is sufficient to power the star for millions to billions of years. Thus, the first phase of stellar evolution in the history of the Universe may have been dark stars. We review how dark stars come into existence, how they grow as long as dark matter fuel persists, and their stellar structure and evolution. The studies were done in two different ways, first assuming polytropic interiors and more recently using the MESA stellar evolution code; the basic results are the same. Dark stars are giant, puffy (∼10 AU) and cool (surface temperatures  ∼10 000 K) objects. We follow the evolution of dark stars from their inception at  ∼[Formula: see text] as they accrete mass from their surroundings to become supermassive stars, some even reaching masses  >[Formula: see text] and luminosities  >[Formula: see text], making them detectable with the upcoming James Webb Space Telescope. Once the dark matter runs out and the dark star dies, it may collapse to a black hole; thus dark stars may provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation may exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The current review briefly discusses dark stars existing today, but focuses on the early generation of dark stars.

  3. Cu-Zn binary phase diagram and diffusion couples

    Science.gov (United States)

    Mccoy, Robert A.

    1992-01-01

    The objectives of this paper are to learn: (1) what information a binary phase diagram can yield; (2) how to construct and heat treat a simple diffusion couple; (3) how to prepare a metallographic sample; (4) how to operate a metallograph; (5) how to correlate phases found in the diffusion couple with phases predicted by the phase diagram; (6) how diffusion couples held at various temperatures could be used to construct a phase diagram; (7) the relation between the thickness of an intermetallic phase layer and the diffusion time; and (8) the effect of one species of atoms diffusing faster than another species in a diffusion couple.

  4. Research principles and the construction of mnemonic diagrams

    Science.gov (United States)

    Venda, V. F.; Mitkin, A. A.

    1973-01-01

    Mnemonic diagrams are defined as a variety of information display devices, the essential element of which is conventional graphical presentation of technological or functional-operational links in a controlled system or object. Graphically displaying the operational structure of an object, the interd dependence between different parameters, and the interdependence between indicators and control organs, the mneomonic diagram reduces the load on the operator's memory and facilitates perception and reprocessing of information and decision making, while at the same time playing the role of visual support to the information activity of the operator. The types of mnemonic diagrams are listed.

  5. Visual syntax of UML class and package diagram constructs as an ontology

    CSIR Research Space (South Africa)

    Thomas, A

    2015-11-01

    Full Text Available of the concrete syntax is useful in diagram processing applications as well as in achieving unambiguous understanding of diagrams. Unified Modeling Language (UML) is a commonly used modeling language to represent software models using its diagrams. Class...

  6. Isolated Neutron Stars

    Directory of Open Access Journals (Sweden)

    Popov S.

    2010-10-01

    Full Text Available Several aspects related to astrophysics of isolated neutron stars are discussed. We start with an introduction into the “new zoo” of young isolated neutron stars. In addition to classical radio pulsars, now we know several species (soft gamma-ray repeators, anomalous X-ray pulsars, central compact objects in supernova remnants, close-by cooling neutron stars - aka “Magnificent seven”, - RRATs, and some others. All these types are briefly discussed. In the second lecture a description of magneto-rotational evolution of neutron stars is given. Finally, in the third lecture we discuss population synthesis of isolated neutron stars. In some details we discuss population synthesis of young isolated radio pulsars and young close-by cooling neutron stars.

  7. Asymptotic giant branch stars in the Large Magellanic Cloud: evolution of dust in circumstellar envelopes

    Science.gov (United States)

    Dell'Agli, F.; Ventura, P.; Schneider, R.; Di Criscienzo, M.; García-Hernández, D. A.; Rossi, C.; Brocato, E.

    2015-03-01

    We calculated theoretical evolutionary sequences of asymptotic giant branch (AGB) stars, including the formation and evolution of dust grains in their circumstellar envelopes. By considering stellar populations of the Large Magellanic Cloud (LMC), we calculate synthetic colour-colour and colour-magnitude diagrams, which are compared with those obtained by the Spitzer Space Telescope. The comparison between observations and theoretical predictions outlines that extremely obscured carbon stars and oxygen-rich sources experiencing hot bottom burning (HBB) occupy well-defined, distinct regions in the colour-colour ([3.6] - [4.5], [5.8] - [8.0]) diagram. The C-rich stars are distributed along a diagonal strip that we interpret as an evolutionary sequence, becoming progressively more obscured as the stellar surface layers enrich in carbon. Their circumstellar envelopes host solid carbon dust grains with size in the range 0.05 2, are the descendants of stars with initial mass Min ˜ 2.5-3 M⊙ in the very latest phases of AGB life. The oxygen-rich stars with the reddest colours ([5.8] - [8.0] > 0.6) are those experiencing HBB, the descendants of ˜5 M⊙ objects formed 108 yr ago; alumina and silicate dust starts forming at different distances from the central star. The overall dust production rate in the LMC is ˜4.5 × 10-5 M⊙ yr-1, the relative percentages due to C and M stars being 85 and 15 per cent, respectively.

  8. SEARCHING FOR NEW YELLOW SYMBIOTIC STARS: POSITIVE IDENTIFICATION OF StHα63

    Energy Technology Data Exchange (ETDEWEB)

    Baella, N. O. [Unidad de Astronomía, Instituto Geofísico del Perú, Lima, Per (Peru); Pereira, C. B.; Alvarez-Candal, A. [Observatório Nacional/MCTI, Rua Gen. José Cristino, 77, 20921-400, Rio de Janeiro (Brazil); Miranda, L. F., E-mail: nobar.baella@gmail.com, E-mail: claudio@on.br, E-mail: alvarez@on.br, E-mail: lfm@iaa.es [Instituto de Astrofísica de Andalucía- CSIC, C/Glorieta de la Astronomía s/n, E-18008 Granada (Spain)

    2016-04-15

    Yellow symbiotic stars are useful targets for probing whether mass transfer has happened in their binary systems. However, the number of known yellow symbiotic stars is very scarce. We report spectroscopic observations of five candidate yellow symbiotic stars that were selected by their positions in the 2MASS (J − H) versus (H − K{sub s}) diagram and which were included in some emission-line catalogs. Among the five candidates, only StHα63 is identified as a new yellow symbiotic star because of its spectrum and its position in the [TiO]{sub 1}–[TiO]{sub 2} diagram, which indicates a K4–K6 spectral type. In addition, the derived electron density (∼10{sup 8.4} cm{sup −3}) and several emission-line intensity ratios provide further support for that classification. The other four candidates are rejected as symbiotic stars because three of them actually do not show emission lines and the fourth one only Balmer emission lines. We also found that the WISE W3–W4 index clearly separates normal K-giants from yellow symbiotic stars and therefore can be used as an additional tool for selecting candidate yellow symbiotic stars.

  9. The Theatre of stars

    Science.gov (United States)

    Cavedon, M.; Peri, F.

    Planetariums are special instruments in education and didactics of Astronomy and Astrophysics. Since 1930 the Planetarium of Milan, the most important planetarium in Italy, has played a fundamental role in outreach to the public. Italian tradition always preferred didactics in ``live'' lessons. Now technology expands the potential of the star projector and the theatre of stars is a real window on the universe, where you can travel among the stars and galaxies, to reach the boundaries of space and time.

  10. Why Stars Matter

    OpenAIRE

    Ajay K. Agrawal; John McHale; Alex Oettl

    2014-01-01

    The growing peer effects literature pays particular attention to the role of stars. We decompose the causal effect of hiring a star in terms of the productivity impact on: 1) co-located incumbents and 2) new recruits. Using longitudinal university department-level data we report that hiring a star does not increase overall incumbent productivity, although this aggregate effect hides offsetting effects on related (positive) versus unrelated (negative) colleagues. However, the primary impact co...

  11. Alaska NAD 83 Composite Block Diagram (CBD) Images

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Composite Block Diagram (CBD) images in Adobe pdf format for areas within the BOEM Alaska Region. Each CBD describes a single block within an...

  12. Phase diagram of Nitrogen at high pressures and temperatures

    Science.gov (United States)

    Jenei, Zsolt; Lin, Jung-Fu; Yoo, Choong-Shik

    2007-03-01

    Nitrogen is a typical molecular solid with relatively weak van der Waals intermolecular interactions but strong intramolecular interaction arising from the second highest binding energy of all diatomic molecules. The phase diagram of solid nitrogen is, however, complicated at high pressures, as inter-molecular interaction becomes comparable to the intra-molecular interaction. In this paper, we present an updated phase diagram of the nitrogen in the pressure-temperature region of 100 GPa and 1000 K, based on in-situ Raman and synchrotron x-ray diffraction studies using externally heated membrane diamond anvil cells. While providing an extension of the phase diagram, our results indicate a ``steeper'' slope of the δ/ɛ phase boundary than previously determined^1. We also studied the stability of the ɛ phase at high pressures and temperatures. Our new experimental results improve the understanding of the Nitrogen phase diagram. 1. Gregoryanz et al, Phys. Rev. B 66, 224108 (2002)

  13. Alaska NAD 83 Official Protraction Diagram (OPD) Outlines

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Official Protraction Diagram (OPD) outlines in ESRI shapefile format. At lower latitudes (0-48 degrees) OPDs are 1 degree in latitude by 2...

  14. Pacific NAD 83 Official Protraction Diagram (OPD) Images

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Official Protraction Diagrams (OPDs) in Adobe PDF format. Pacific Region OPDs are approximately 2 degrees wide by one degree high. OPDs are...

  15. Alaska NAD 83 Supplemental Official Protraction Diagram (OPD) Images

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Supplemental Official OCS Block Diagram (SOBD) images in Adobe pdf format for areas within the BOEM Alaska Region. Each SOBD describes a...

  16. Official Protraction Diagram and Leasing Map Boundaries - Direct Download

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This map layer shows official protraction diagram (OPD) and leasing map boundaries covering areas of the Outer Continental Shelf (OCS) within Federal jurisdiction....

  17. Outer Continental Shelf Official Protraction Diagrams - Atlantic Region NAD 83

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Official Protraction Diagram (OPD) outlines in ESRI shapefile format. Atlantic Region OPDs are approximately 2 degrees wide by one degree...

  18. Outer Continental Shelf Official Protraction Diagrams - Alaska Region NAD 83

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Official Protraction Diagram (OPD) outlines in ESRI shapefile format. At lower latitudes (0-48 degrees) OPDs are 1 degree in latitude by 2...

  19. Building Expert Medical Prognostic Systems Using Voronoi Diagram

    Directory of Open Access Journals (Sweden)

    Maria A. Ivanchuk

    2015-01-01

    Full Text Available The method of building expert systems for medical prediction of severity in patients is purposed. The method is based on using Voronoi diagrams. Examples of using the method are described in the paper.

  20. Architecture flow diagrams under teamwork{reg_sign}

    Energy Technology Data Exchange (ETDEWEB)

    Nicinski, T.

    1992-02-01

    The Teamwork CASE tool allows Data Flow Diagrams (DFDs) to be maintained for structured analysis. Fermilab has extended teamwork under UNIX{trademark} to permit Hatley and Pirbhai Architecture Flow Diagrams (AFDs) to be associated with DFDs and subsequently maintained. This extension, called TWKAFD, allows a user to open an AFD, graphically edit it, and replace it into a TWKAFD maintained library. Other aspects of Hatley and Pirbhai`s methodology are supported. This paper presents a quick tutorial on Architecture Diagrams. It then describes the user`s view of TWKAFD, the experience incorporating it into teamwork, and the successes with using the Architecture Diagram methodology along with the shortcomings of using the teamwork/TWKAFD tool. 8 refs.

  1. Atlantic NAD 83 Supplemental Official OCS Block Diagram (SOBD) Images

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Supplemental Official OCS Block Diagram (SOBD) images in Adobe pdf format for areas within the BOEM Atlantic Region. Each SOBD describes a...

  2. Atlantic NAD 83 Official Protraction Diagram (OPD) Images

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains Official Protraction Diagrams (OPDs) in Adobe PDF format. Atlantic Region OPDs are approximately 2 degrees wide by one degree high. OPDs are...

  3. VizieR Online Data Catalog: Common proper motion stars in the Kepler field (Janes, 2017)

    Science.gov (United States)

    Janes, K. A.

    2017-08-01

    In a search of proper motion catalogs for common proper motion stars in the field of the Kepler spacecraft I identified 93 likely binary systems. A comparison of their rotation periods is a test of the gyrochronology concept. To find their periods I calculated the autocorrelation function (ACF) of the Kepler mission photometry for each star. In most systems for which good periods can be found, the cooler star has a longer period than the hotter component, in general agreement with models. However, there is a wide range in the gradients of lines connecting binary pairs in a period-color diagram. Furthermore, near the solar color, only a few stars have longer periods than the Sun, suggesting that they, and their cooler companions, are not much older than the Sun. In addition, there is an apparent gap at intermediate periods in the period distribution of the late K and early M stars. Either star formation in this direction has been variable, or stars evolve in period at a non-uniform rate, or some stars evolve more rapidly than others at the same mass. Finally, using the ACF as a measure of the activity level, I found that while the F, G, and early K stars become less active as their periods increase, there is no correlation between period and activity for the mid K to early M stars. (1 data file).

  4. Interacting binary stars

    CERN Document Server

    Sahade, Jorge; Ter Haar, D

    1978-01-01

    Interacting Binary Stars deals with the development, ideas, and problems in the study of interacting binary stars. The book consolidates the information that is scattered over many publications and papers and gives an account of important discoveries with relevant historical background. Chapters are devoted to the presentation and discussion of the different facets of the field, such as historical account of the development in the field of study of binary stars; the Roche equipotential surfaces; methods and techniques in space astronomy; and enumeration of binary star systems that are studied

  5. Strange Nonchaotic Stars

    Science.gov (United States)

    Lindner, John F.; Kohar, Vivek; Kia, Behnam; Hippke, Michael; Learned, John G.; Ditto, William L.

    2015-08-01

    Exploiting the unprecedented capabilities of the planet-hunting Kepler space telescope, which stared at 150 000 stars for four years, we discuss recent evidence that certain stars dim and brighten in complex patterns with fractal features. Such stars pulsate at primary and secondary frequencies whose ratios are near the famous golden mean, the most irrational number. A nonlinear system driven by an irrational ratio of frequencies is generically attracted toward a “strange” behavior that is geometrically fractal without displaying the “butterfly effect” of chaos. Strange nonchaotic attractors have been observed in laboratory experiments and have been hypothesized to describe the electrochemical activity of the brain, but a bluish white star 16 000 light years from Earth in the constellation Lyra may manifest, in the scale-free distribution of its minor frequency components, the first strange nonchaotic attractor observed in the wild. The recognition of stellar strange nonchaotic dynamics may improve the classification of these stars and refine the physical modeling of their interiors. We also discuss nonlinear analysis of other RR Lyrae stars in Kepler field of view and discuss some toy models for modeling these stars.References: 1) Hippke, Michael, et al. "Pulsation period variations in the RRc Lyrae star KIC 5520878." The Astrophysical Journal 798.1 (2015): 42.2) Lindner, John F., et al. "Strange nonchaotic stars." Phys. Rev. Lett. 114, 054101 (2015)

  6. Covering tree with stars

    DEFF Research Database (Denmark)

    Baumbach, Jan; Guo, Jian-Ying; Ibragimov, Rashid

    2013-01-01

    We study the tree edit distance problem with edge deletions and edge insertions as edit operations. We reformulate a special case of this problem as Covering Tree with Stars (CTS): given a tree T and a set of stars, can we connect the stars in by adding edges between them such that the resulting...... tree is isomorphic to T? We prove that in the general setting, CST is NP-complete, which implies that the tree edit distance considered here is also NP-hard, even when both input trees having diameters bounded by 10. We also show that, when the number of distinct stars is bounded by a constant k, CTS...

  7. Covering tree with stars

    DEFF Research Database (Denmark)

    Baumbach, Jan; Guo, Jiong; Ibragimov, Rashid

    2015-01-01

    We study the tree edit distance problem with edge deletions and edge insertions as edit operations. We reformulate a special case of this problem as Covering Tree with Stars (CTS): given a tree T and a set of stars, can we connect the stars in by adding edges between them such that the resulting...... tree is isomorphic to T? We prove that in the general setting, CST is NP-complete, which implies that the tree edit distance considered here is also NP-hard, even when both input trees having diameters bounded by 10. We also show that, when the number of distinct stars is bounded by a constant k, CTS...

  8. ENERGY STAR Unit Reports

    Data.gov (United States)

    Department of Housing and Urban Development — These quarterly Federal Fiscal Year performance reports track the ENERGY STAR qualified HOME units that Participating Jurisdictions record in HUD's Integrated...

  9. Reactome diagram viewer: Data structures and strategies to boost performance.

    Science.gov (United States)

    Fabregat, Antonio; Sidiropoulos, Konstantinos; Viteri, Guilherme; Marin-Garcia, Pablo; Ping, Peipei; Stein, Lincoln; D'Eustachio, Peter; Hermjakob, Henning

    2017-11-23

    Reactome is a free, open-source, open-data, curated and peer-reviewed knowledgebase of biomolecular pathways. For web-based pathway visualisation, Reactome uses a custom pathway diagram viewer that has been evolved over the past years. Here, we present comprehensive enhancements in usability and performance based on extensive usability testing sessions and technology developments, aiming to optimise the viewer towards the needs of the community. The pathway diagram viewer version 3 achieves consistently better performance, loading and rendering of 97% of the diagrams in Reactome in less than 1 second. Combining the multi-layer html5 canvas strategy with a space partitioning data structure minimises CPU workload, enabling the introduction of new features that further enhance user experience. Through the use of highly optimised data structures and algorithms, Reactome has boosted the performance and usability of the new pathway diagram viewer, providing a robust, scalable and easy-to-integrate solution to pathway visualisation. As graph-based visualisation of complex data is a frequent challenge in bioinformatics, many of the individual strategies presented here are applicable to a wide range of web-based bioinformatics resources. Reactome is available online at: https://reactome.org. The diagram viewer is part of the Reactome pathway browser (https://reactome.org/PathwayBrowser/) and also available as a stand-alone widget at: https://reactome.org/dev/diagram/. The source code is freely available at: https://github.com/reactome-pwp/diagram. hhe@ebi.ac.uk, fabregat@ebi.ac.uk. An introductory video explaining the most relevant features of the Reactome pathway browser and the diagram viewer is available at https://youtu.be/-skixrvI4nU.

  10. The Pathway Tools cellular overview diagram and Omics Viewer

    OpenAIRE

    Paley, Suzanne M.; Karp, Peter D.

    2006-01-01

    The Pathway Tools cellular overview diagram is a visual representation of the biochemical network of an organism. The overview is automatically created from a Pathway/Genome Database describing that organism. The cellular overview includes metabolic, transport and signaling pathways, and other membrane and periplasmic proteins. Pathway Tools supports interrogation and exploration of cellular biochemical networks through the overview diagram. Furthermore, a software component called the Omics ...

  11. Construction of Penrose Diagrams for Dynamic Black Holes

    Science.gov (United States)

    Brown, Beth A.; Lindesay, James

    2008-01-01

    A set of Penrose diagrams is constructed in order to examine the large-scale causal structure of black holes with dynamic horizons. Coordinate dependencies of significant features, such as the event horizon and radial mass scale, are demonstrated on the diagrams. Unlike in static Schwarzschild geometries, the radial mass scale is clearly seen to differ from the horizon. Trajectories for photons near the horizon are briefly discussed.

  12. Elastic properties of cubic crystals: Every's versus Blackman's diagram

    OpenAIRE

    Paszkiewicz, T.; Wolski, S.

    2007-01-01

    Blackman's diagram of two dimensionless ratios of elastic constants is frequently used to correlate elastic properties of cubic crystals with interatomic bondings. Every's diagram of a different set of two dimensionless variables was used by us for classification of various properties of such crystals. We compare these two ways of characterization of elastic properties of cubic materials and consider the description of various groups of materials, e.g. simple metals, oxides, and alkali halide...

  13. Content repurposing of electrical diagrams for presentation in handheld devices

    OpenAIRE

    Papaliakos, Vasilios

    2004-01-01

    Approved for public release, distribution is unlimited This thesis proposes a design for content repurposing of electrical diagrams for presentation in small-screen wireless handheld devices. Content repurposing is the on-line adaptation of content to fit device capabilities and user's preferences. The focus of this thesis is on electrical diagrams of the schematic type used for maintenance purposes. Nevertheless, many of the proposed techniques are suitable for other technical drawings as...

  14. Horizontal Branch stars as AmFm/HgMn stars

    OpenAIRE

    Michaud, G.; Richer, J.

    2008-01-01

    Recent observations and models for horizontal branch stars are briefly described and compared to models for AmFm stars. The limitations of those models are emphasized by a comparison to observations and models for HgMn stars.

  15. Evolving R Coronae Borealis Stars with MESA

    Science.gov (United States)

    Clayton, Geoffrey C.; Lauer, Amber; Chatzopoulos, Emmanouil; Frank, Juhan

    2018-01-01

    R Coronae Borealis (RCB) stars form a small class of cool, carbon-rich supergiants that have almost no hydrogen. They undergo extreme, irregular declines in brightness of up to 8 magnitudes due to the formation of thick clouds of carbon dust. Two scenarios have been proposed for the origin of an RCB star: the merger of a CO/He white dwarf (WD) binary and a final helium-shell flash. We are using a combination of 3D hydrodynamics codes and the 1D MESA (Modules for Experiments in Stellar Astrophysics) stellar evolution code including nucleosynthesis to construct post-merger spherical models based on realistic merger progenitor models and on our hydrodynamical simulations, and then following the evolution into the region of the HR diagram where RCB stars are located. We are investigating nucleosynthesis in the dynamically accreting material of CO/He WD mergers which may provide a suitable environment for significant production of 18O and the very low 16O/18O values observed.Our MESA modeling consists of two steps: first mimicking the WD merger event using two different techniques, (a) by choosing a very high mass accretion rate with appropriate abundances and (b) by applying "stellar engineering" to an initial CO WD model to account for the newly merged material by applying an entropy adjusting procedure. Second, we follow the post-merger evolution using a large nuclear reaction network including the effects of convective and rotational instabilities to the mixing of material in order to match the observed RCB abundances. MESA follows the evolution of the merger product as it expands and cools to become an RCB star. We then examine the surface abundances and compare them to the observed RCB abundances. We also investigate how long fusion continues in the He shell near the core and how this processed material is mixed up to the surface of the star. We then model the later evolution of RCB stars to determine their likely lifetimes and endpoints when they have returned to

  16. Construction of UML class diagram with Model-Driven Development

    Directory of Open Access Journals (Sweden)

    Tomasz Górski

    2016-03-01

    Full Text Available Model transformations play a key role in software development projects based on Model--Driven Development (MDD principles. Transformations allow for automation of repetitive and well-defined steps, thus shortening design time and reducing a number of errors. In the object-oriented approach, the key elements are use cases. They are described, modelled and later designed until executable application code is obtained. The aim of the paper is to present transformation of a model-to-model type, Communication-2-Class, which automates construction of Unified Modelling Language (UML class diagram in the context of the analysis/design model. An UML class diagram is created based on UML communication diagram within use case realization. As a result, a class diagram shows all of the classes involved in the use case realization and the relationships among them. The plug-in which implements Communication-2-Class transformation was implemented in the IBM Rational Software Architect. The article presents the tests results of developed plug-in, which realizes Communication-2-Class transformation, showing capabilities of shortening use case realization’s design time.[b]Keywords[/b]: Model-Driven Development, transformations, Unified Modelling Language, analysis/design model, UML class diagram, UML communication diagram

  17. The evolved slowly pulsating B star 18 Peg: A testbed for upper main sequence stellar evolution

    Science.gov (United States)

    Irrgang, A.; De Cat, P.; Tkachenko, A.; Deshpande, A.; Moehler, S.; Mugrauer, M.; Janousch, D.

    2017-09-01

    The bright B3 III giant star 18 Peg turns out to be a slowly pulsating B star in a long period binary with a main-sequence star or a neutron star as companion. Given that it is one of the most evolved members of this class of massive pulsating stars, an accurate determination of the location of 18 Peg in the Hertzsprung-Russell (H-R) diagram would provide a lower limit on the width of the upper main sequence and hence would reveal information about the efficiency of the convective overshooting. We explain why long-term space-based observations are needed and how BRITE could play a crucial role in the gathering of the mandatory ingredients to test the models of the upper main sequence evolution.

  18. Merging strangeon stars

    Science.gov (United States)

    Lai, Xiao-Yu; Yu, Yun-Wei; Zhou, En-Ping; Li, Yun-Yang; Xu, Ren-Xin

    2018-02-01

    The state of supranuclear matter in compact stars remains puzzling, and it is argued that pulsars could be strangeon stars. What would happen if binary strangeon stars merge? This kind of merger could result in the formation of a hyper-massive strangeon star, accompanied by bursts of gravitational waves and electromagnetic radiation (and even a strangeon kilonova explained in the paper). The tidal polarizability of binary strangeon stars is different from that of binary neutron stars, because a strangeon star is self-bound on the surface by the fundamental strong force while a neutron star by the gravity, and their equations of state are different. Our calculation shows that the tidal polarizability of merging binary strangeon stars is favored by GW170817. Three kinds of kilonovae (i.e., of neutron, quark and strangeon) are discussed, and the light curve of the kilonova AT 2017 gfo following GW170817 could be explained by considering the decaying strangeon nuggets and remnant star spin-down. Additionally, the energy ejected to the fireball around the nascent remnant strangeon star, being manifested as a gamma-ray burst, is calculated. It is found that, after a prompt burst, an X-ray plateau could follow in a timescale of 102 ‑ 103 s. Certainly, the results could be tested also by further observational synergies between gravitational wave detectors (e.g., Advanced LIGO) and X-ray telescopes (e.g., the Chinese HXMT satellite and eXTP mission), and especially if the detected gravitational wave form is checked by peculiar equations of state provided by the numerical relativistical simulation.

  19. The cool half of the H-R diagram in soft X-rays

    Science.gov (United States)

    Ayres, T. R.; Linsky, J. L.; Vaiana, G. S.; Golub, L.; Rosner, R.

    1981-01-01

    The results of an Einstein Observatory program to map the occurrence of hot coronae (T greater than 1 million K) in the cool half of the Hertzsprung-Russell diagram are reported. F-M dwarfs, and late F through early K star giants characterized by 10,000 K chromospheric and 20,000-200,000 K FUV emission lines were studied in one region, while a second region study included red giants later than K2 III and supergiants later than G5 Ib with weaker chromospheric emission and no high temperature species. Program goals comprised determination of the C IV division as seen in soft X-rays, and identification of stellar parameters which distinguish strong from weak coronal X-ray sources. A summary of target stars, X-ray fluxes, and UV emission profiles is provided, and coronal emissions, comparisons of C IV and wind boundaries, hybrid-spectrum supergiants, the energy balance of stellar outer atmospheres, stellar rotation and coronae, and evolutionary considerations are discussed, along with lines of future research.

  20. Optimal photometry for colour-magnitude diagrams and its application to NGC 2547

    Science.gov (United States)

    Naylor, Tim; Totten, E. J.; Jeffries, R. D.; Pozzo, M.; Devey, C. R.; Thompson, S. A.

    2002-09-01

    We have developed the techniques required to use Naylor's optimal photometry algorithm of to create colour-magnitude diagrams with well-defined completeness functions. To achieve this we first demonstrate that the optimal extraction is insensitive to uncertainties in the measured position of the star. We then show how to correct the optimally extracted fluxes such that they correspond to those measured in a large aperture, so aperture photometry of standard stars can be used to place the measurements on a standard system. The technique simultaneously removes the effects of a position-dependent point spread function. Finally, we develop a method called `ghosting', which calculates the completeness corrections in the absence of an accurate description of the point spread function. We apply these techniques to the young cluster NGC 2547 (=C0809-491), and use an X-ray-selected sample to find an age of 20-35 Myr and an intrinsic distance modulus of 8.00-8.15 mag. We use these isochrones to select members from our photometric surveys. Our derived luminosity function shows a well-defined Wielen dip, making NGC 2547 the youngest cluster in which such a feature has been observed. Our derived mass function spans the range 0.1-6 Msolar and is similar to that for the field and the older, more massive clusters M35 and the Pleiades, supporting the idea of a universal initial mass function.

  1. Quark-Novae Ia in the Hubble diagram: implications for dark energy

    Science.gov (United States)

    Ouyed, Rachid; Koning, Nico; Leahy, Denis; Staff, Jan E.; Cassidy, Daniel T.

    2014-05-01

    The accelerated expansion of the Universe was proposed through the use of Type-Ia supernovae (SNe) as standard candles. The standardization depends on an empirical correlation between the stretch/color and peak luminosity of the light curves. The use of Type-Ia SNe as standard candles rests on the assumption that their properties (and this correlation) do not vary with redshift. We consider the possibility that the majority of Type-Ia SNe are in fact caused by a Quark-Nova detonation in a tight neutron-star-CO-white-dwarf binary system, which forms a Quark-Nova Ia (QN-Ia). The spin-down energy injected by the Quark-Nova remnant (the quark star) contributes to the post-peak light curve and neatly explains the observed correlation between peak luminosity and light curve shape. We demonstrate that the parameters describing QN-Ia are NOT constant in redshift. Simulated QN-Ia light curves provide a test of the stretch/color correlation by comparing the true distance modulus with that determined using SN light curve fitters. We determine a correction between the true and fitted distance moduli, which when applied to Type-Ia SNe in the Hubble diagram recovers the ΩM = 1 cosmology. We conclude that Type-Ia SNe observations do not necessitate the need for an accelerating expansion of the Universe (if the observed SNe Ia are dominated by QNe Ia) and by association the need for dark energy.

  2. Are pre-main-sequence stars older than we thought?

    Science.gov (United States)

    Naylor, Tim

    2009-10-01

    We fit the colour-magnitude diagrams of stars between the zero-age main-sequence and terminal-age main sequence in young clusters and associations. The ages we derive are a factor of 1.5-2 longer than the commonly used ages for these regions, which are derived from the positions of pre-main-sequence stars in colour-magnitude diagrams. From an examination of the uncertainties in the main-sequence and pre-main-sequence models, we conclude that the longer age scale is probably the correct one, which implies that we must revise upwards the commonly used ages for young clusters and associations. Such a revision would explain the discrepancy between the observational lifetimes of protoplanetary discs and theoretical calculations of the time to form planets. It would also explain the absence of clusters with ages between 5 and 30Myr. We use the τ2 statistic to fit the main-sequence data, but find that we must make significant modifications if we are to fit sequences which have vertical segments in the colour-magnitude diagram. We present this modification along with improvements to the methods of calculating the goodness-of-fit statistic and parameter uncertainties. Software implementing the methods described in this paper is available from http://www.astro.ex.ac.uk/people/timn/tau-squared/.

  3. Stars and Flowers, Flowers and Stars

    Science.gov (United States)

    Minti, Hari

    2012-12-01

    The author, a graduated from the Bucharest University (1964), actually living and working in Israel, concerns his book to variable stars and flowers, two domains of his interest. The analogies includes double stars, eclipsing double stars, eclipses, Big Bang. The book contains 34 chapters, each of which concerns various relations between astronomy and other sciences and pseudosciences such as Psychology, Religion, Geology, Computers and Astrology (to which the author is not an adherent). A special part of the book is dedicated to archeoastronomy and ethnoastronomy, as well as to history of astronomy. Between the main points of interest of these parts: ancient sanctuaries in Sarmizegetusa (Dacia), Stone Henge(UK) and other. The last chapter of the book is dedicated to flowers. The book is richly illustrated. It is designed for a wide circle of readers.

  4. Star Trek in the Schools

    Science.gov (United States)

    Journal of Aerospace Education, 1977

    1977-01-01

    Describes specific educational programs for using the Star Trek TV program from kindergarten through college. For each grade level lesson plans, ideas for incorporating Star Trek into future classes, and reports of specific programs utilizing Star Trek are provided. (SL)

  5. Hadrons in compact stars

    Indian Academy of Sciences (India)

    volving Bose–Einstein condensates of antikaons within relativistic models. Also, the structures of non-rotating neutron stars are calculated using this EoS. 2. Hadrons in cold and dense medium. At normal nuclear matter density, neutron star matter mainly consists of neutrons, protons and electrons. The particle population is ...

  6. ENERGY STAR Certified Telephones

    Science.gov (United States)

    Certified models meet all ENERGY STAR requirements as listed in the Version 3.0 ENERGY STAR Program Requirements for Telephony (cordless telephones and VoIP telephones) that are effective as of October 1, 2014. A detailed listing of key efficiency criteria are available at http://www.energystar.gov/index.cfm?c=phones.pr_crit_phones

  7. Science Through ARts (STAR)

    Science.gov (United States)

    Kolecki, Joseph; Petersen, Ruth; Williams, Lawrence

    2002-01-01

    Science Through ARts (STAR) is an educational initiative designed to teach students through a multidisciplinary approach to learning. This presentation describes the STAR pilot project, which will use Mars exploration as the topic to be integrated. Schools from the United Kingdom, Japan, the United States, and possibly eastern Europe are expected to participate in the pilot project.

  8. Neutron Stars: Formation and Structure

    OpenAIRE

    Kutschera, Marek

    1998-01-01

    A short introduction is given to astrophysics of neutron stars and to physics of dense matter in neutron stars. Observed properties of astrophysical objects containing neutron stars are discussed. Current scenarios regarding formation and evolution of neutron stars in those objects are presented. Physical principles governing the internal structure of neutron stars are considered with special emphasis on the possible spin ordering in the neutron star matter.

  9. Are Pulsars Bare Strange Stars?

    Science.gov (United States)

    Xu, R. X.; Qiao, G. J.; Zhang, B.

    It is believed that pulsars are neutron stars or strange stars with crusts. However we suggest here that pulsars may be bare strange stars (i.e., strange stars without crust). Due to rapid rotation and strong emission, young strange stars produced in supernova explosions should be bare when they act as radio pulsars. Because of strong magnetic field, two polar-crusts would shield the polar caps of an accreting strange star. Such a suggestion can be checked by further observations.

  10. Magnetic Fields of Massive Stars

    OpenAIRE

    Lundin, Andreas

    2010-01-01

    This paper is an introduction to the subject of magnetic fields on stars, with a focus on hotter stars. Basic astrophysical concepts are explained, including: spectroscopy, stellar classification, general structure and evolution of stars. The Zeeman effect and how absorption line splitting  is used to detect and measure magnetic fields is explained. The properties of a prominent type of magnetic massive star, Ap-stars, are delved into. These stars have very stable, global, roughly dipolar mag...

  11. Rotating stars in relativity.

    Science.gov (United States)

    Paschalidis, Vasileios; Stergioulas, Nikolaos

    2017-01-01

    Rotating relativistic stars have been studied extensively in recent years, both theoretically and observationally, because of the information they might yield about the equation of state of matter at extremely high densities and because they are considered to be promising sources of gravitational waves. The latest theoretical understanding of rotating stars in relativity is reviewed in this updated article. The sections on equilibrium properties and on nonaxisymmetric oscillations and instabilities in f -modes and r -modes have been updated. Several new sections have been added on equilibria in modified theories of gravity, approximate universal relationships, the one-arm spiral instability, on analytic solutions for the exterior spacetime, rotating stars in LMXBs, rotating strange stars, and on rotating stars in numerical relativity including both hydrodynamic and magnetohydrodynamic studies of these objects.

  12. Neutron Stars and Pulsars

    CERN Document Server

    Becker, Werner

    2009-01-01

    Neutron stars are the most compact astronomical objects in the universe which are accessible by direct observation. Studying neutron stars means studying physics in regimes unattainable in any terrestrial laboratory. Understanding their observed complex phenomena requires a wide range of scientific disciplines, including the nuclear and condensed matter physics of very dense matter in neutron star interiors, plasma physics and quantum electrodynamics of magnetospheres, and the relativistic magneto-hydrodynamics of electron-positron pulsar winds interacting with some ambient medium. Not to mention the test bed neutron stars provide for general relativity theories, and their importance as potential sources of gravitational waves. It is this variety of disciplines which, among others, makes neutron star research so fascinating, not only for those who have been working in the field for many years but also for students and young scientists. The aim of this book is to serve as a reference work which not only review...

  13. How Stars Form

    Science.gov (United States)

    McKee, Christopher F.

    2017-01-01

    Stars are the atoms of the universe. The process by which stars form is at the nexus of astrophysics since they are believed to be responsible for the re-ionization of the universe, they created the heavy elements, they play a central role in the formation and evolution of galaxies, and their formation naturally leads to the formation of planets. Whereas early work on star formation was based on the assumption that it is a quiescent process, it is now believed that turbulence plays a dominant role. In this overview, I shall discuss the evolution of our understanding of how stars form and current ideas about the stellar initial mass function and the rate of star formation.

  14. Infrared thermography method for fast estimation of phase diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Palomo Del Barrio, Elena [Université de Bordeaux, Institut de Mécanique et d’Ingénierie, Esplanade des Arts et Métiers, 33405 Talence (France); Cadoret, Régis [Centre National de la Recherche Scientifique, Institut de Mécanique et d’Ingénierie, Esplanade des Arts et Métiers, 33405 Talence (France); Daranlot, Julien [Solvay, Laboratoire du Futur, 178 Av du Dr Schweitzer, 33608 Pessac (France); Achchaq, Fouzia, E-mail: fouzia.achchaq@u-bordeaux.fr [Université de Bordeaux, Institut de Mécanique et d’Ingénierie, Esplanade des Arts et Métiers, 33405 Talence (France)

    2016-02-10

    Highlights: • Infrared thermography is proposed to determine phase diagrams in record time. • Phase boundaries are detected by means of emissivity changes during heating. • Transition lines are identified by using Singular Value Decomposition techniques. • Different binary systems have been used for validation purposes. - Abstract: Phase change materials (PCM) are widely used today in thermal energy storage applications. Pure PCMs are rarely used because of non adapted melting points. Instead of them, mixtures are preferred. The search of suitable mixtures, preferably eutectics, is often a tedious and time consuming task which requires the determination of phase diagrams. In order to accelerate this screening step, a new method for estimating phase diagrams in record time (1–3 h) has been established and validated. A sample composed by small droplets of mixtures with different compositions (as many as necessary to have a good coverage of the phase diagram) deposited on a flat substrate is first prepared and cooled down to ambient temperature so that all droplets crystallize. The plate is then heated at constant heating rate up to a sufficiently high temperature for melting all the small crystals. The heating process is imaged by using an infrared camera. An appropriate method based on singular values decomposition technique has been developed to analyze the recorded images and to determine the transition lines of the phase diagram. The method has been applied to determine several simple eutectic phase diagrams and the reached results have been validated by comparison with the phase diagrams obtained by Differential Scanning Calorimeter measurements and by thermodynamic modelling.

  15. Star spot location estimation using Kalman filter for star tracker.

    Science.gov (United States)

    Liu, Hai-bo; Yang, Jian-kun; Wang, Jiong-qi; Tan, Ji-chun; Li, Xiu-jian

    2011-04-20

    Star pattern recognition and attitude determination accuracy is highly dependent on star spot location accuracy for the star tracker. A star spot location estimation approach with the Kalman filter for a star tracker has been proposed, which consists of three steps. In the proposed approach, the approximate locations of the star spots in successive frames are predicted first; then the measurement star spot locations are achieved by defining a series of small windows around each predictive star spot location. Finally, the star spot locations are updated by the designed Kalman filter. To confirm the proposed star spot location estimation approach, the simulations based on the orbit data of the CHAMP satellite and the real guide star catalog are performed. The simulation results indicate that the proposed approach can filter out noises from the measurements remarkably if the sampling frequency is sufficient. © 2011 Optical Society of America

  16. Non-radial modes in AGB stars

    Directory of Open Access Journals (Sweden)

    Montalbán Josefina

    2017-01-01

    Full Text Available The success of asteroseismology in characterising G-K giants has motivated the extension of the same techniques to stars after the central He-burning and M-giants. The latter have been usually studied only as radial pulsators; the presence, however, of fine-structure in the period-luminosity diagram of red variables in the Magellanic Clouds could result from the presence of non-radial oscillations, offering the potential of observational indexes based on non-radial oscillations also for luminous red giants. We present here the results of a first approach aiming to identify the origin of the sub-ridges in the sequence A of the LMC red variables.

  17. Monte Carlo simulation of star/linear and star/star blends with chemically identical monomers

    Energy Technology Data Exchange (ETDEWEB)

    Theodorakis, P E [Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina (Greece); Avgeropoulos, A [Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina (Greece); Freire, J J [Departamento de Ciencias y Tecnicas FisicoquImicas, Universidad Nacional de Educacion a Distancia, Facultad de Ciencias, Senda del Rey 9, 28040 Madrid (Spain); Kosmas, M [Department of Chemistry, University of Ioannina, 45110 Ioannina (Greece); Vlahos, C [Department of Chemistry, University of Ioannina, 45110 Ioannina (Greece)

    2007-11-21

    The effects of chain size and architectural asymmetry on the miscibility of blends with chemically identical monomers, differing only in their molecular weight and architecture, are studied via Monte Carlo simulation by using the bond fluctuation model. Namely, we consider blends composed of linear/linear, star/linear and star/star chains. We found that linear/linear blends are more miscible than the corresponding star/star mixtures. In star/linear blends, the increase in the volume fraction of the star chains increases the miscibility. For both star/linear and star/star blends, the miscibility decreases with the increase in star functionality. When we increase the molecular weight of linear chains of star/linear mixtures the miscibility decreases. Our findings are compared with recent analytical and experimental results.

  18. Highlights from STAR heavy ion program

    Science.gov (United States)

    Okorokov, Vitalii

    2017-10-01

    Recent experimental results obtained in STAR experiment at the Relativistic heavy-ion collider (RHIC) with ion beams will be discussed. Investigations of different nuclear collisions in some recent years focus on two main tasks, namely, detail study of quark-gluon matter properties and exploration of the quantum chromodynamics (QCD) phase diagram. Results at top RHIC energy show clearly the collective behavior of heavy quarks in nucleus-nucleus interactions. Jet and heavy hadron measurements lead to new constraints for energy loss models for various flavors. Heavy-ion collisions are unique tool for the study of topological properties of theory as well as the magneto-hydrodynamics of strongly interacting matter. Experimental results obtained for discrete QCD symmetries at finite temperatures confirm indirectly the topologically non-trivial structure of QCD vacuum. Finite global vorticity observed in non-central Au+Au collisions can be considered as important signature for presence of various chiral effects in sQGP. Most results obtained during stage I of the RHIC beam energy scan (BES) program show smooth behavior vs initial energy. However certain results suggest the transition in the domain of dominance of hadronic degrees of freedom at center-of-mass energies between 10-20 GeV. The stage II of the BES at RHIC will occur in 2019-2020 and will explore with precision measurements in the domain of the QCD phase diagram with high baryon densities. Future developments and more precise studies of features of QCD phase diagram in the framework of stage II of RHIC BES will be briefly discussed.

  19. Star Cluster Structure from Hierarchical Star Formation

    Science.gov (United States)

    Grudic, Michael; Hopkins, Philip; Murray, Norman; Lamberts, Astrid; Guszejnov, David; Schmitz, Denise; Boylan-Kolchin, Michael

    2018-01-01

    Young massive star clusters (YMCs) spanning 104-108 M⊙ in mass generally have similar radial surface density profiles, with an outer power-law index typically between -2 and -3. This similarity suggests that they are shaped by scale-free physics at formation. Recent multi-physics MHD simulations of YMC formation have also produced populations of YMCs with this type of surface density profile, allowing us to narrow down the physics necessary to form a YMC with properties as observed. We show that the shallow density profiles of YMCs are a natural result of phase-space mixing that occurs as they assemble from the clumpy, hierarchically-clustered configuration imprinted by the star formation process. We develop physical intuition for this process via analytic arguments and collisionless N-body experiments, elucidating the connection between star formation physics and star cluster structure. This has implications for the early-time structure and evolution of proto-globular clusters, and prospects for simulating their formation in the FIRE cosmological zoom-in simulations.

  20. A high fraction of Be stars in young massive clusters: evidence for a large population of near-critically rotating stars

    Science.gov (United States)

    Bastian, N.; Cabrera-Ziri, I.; Niederhofer, F.; de Mink, S.; Georgy, C.; Baade, D.; Correnti, M.; Usher, C.; Romaniello, M.

    2017-03-01

    Recent photometric analyses of the colour-magnitude diagrams of young massive clusters (YMCs) have found evidence for splitting in the main sequence and extended main-sequence turn-offs, both of which have been suggested to be caused by stellar rotation. Comparison of the observed main-sequence splitting with models has led various authors to suggest a rather extreme stellar rotation distribution, with a minority (10-30 per cent) of stars with low rotational velocities and the remainder (70-90 per cent) of stars rotating near the critical rotation (I.e. near break-up). We test this hypothesis by searching for Be stars within two YMCs in the Large Magellanic Cloud (NGC 1850 and NGC 1856), which are thought to be critically rotating stars with decretion discs that are (partially) ionized by their host stars. In both clusters, we detect large populations of Be stars at the main-sequence turn-off (˜30-60 per cent of stars), which supports previous suggestions of large populations of rapidly rotating stars within massive clusters.

  1. The real population of star clusters in the bar of the Large Magellanic Cloud

    Science.gov (United States)

    Piatti, Andrés E.

    2017-09-01

    We report results on star clusters located in the south-eastern half of the Large Magellanic (LMC) bar from Washington CT1 photometry. Using appropriate kernel density estimators, we detected 73 star cluster candidates, three of which do not show any detectable trace of star cluster sequences in their colour-magnitude diagrams (CMDs). We did not detect the other 38 previously catalogued clusters, which could not be recognized when visually inspecting the C and T1 images either; the distribution of stars in their respective fields do not resemble that of a stellar aggregate. They represent 33 per cent of all catalogued objects located within the analysed LMC bar field. From matching theoretical isochrones to the cluster CMDs cleaned from field star contamination, we derived ages in the range 7.2 formation activity has taken place during the period log(t yr-1) 8.0-9.0. Since 100 Myr ago, clusters have been formed during a few bursting formation episodes. When comparing the observed CF to that recovered from the star formation rate, we found noticeable differences, which suggests that field star and star cluster formation histories could have been significantly different. Photometric catalogues of the studied star clusters are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/606/A21

  2. The Pathway Tools cellular overview diagram and Omics Viewer.

    Science.gov (United States)

    Paley, Suzanne M; Karp, Peter D

    2006-01-01

    The Pathway Tools cellular overview diagram is a visual representation of the biochemical network of an organism. The overview is automatically created from a Pathway/Genome Database describing that organism. The cellular overview includes metabolic, transport and signaling pathways, and other membrane and periplasmic proteins. Pathway Tools supports interrogation and exploration of cellular biochemical networks through the overview diagram. Furthermore, a software component called the Omics Viewer provides visual analysis of whole-organism datasets using the overview diagram as an organizing framework. For example, gene expression and metabolomics measurements, alone or in combination, can be painted onto the overview, as can computed whole-organism datasets, such as predicted reaction-flux values. The cellular overview and Omics Viewer provide a mechanism whereby biologists can apply the pattern-recognition capabilities of the human visual system to analyze large-scale datasets in a biologically meaningful context. SRI's BioCyc.org website provides overview diagrams for more than 200 organisms. This article describes enhancements to the overview made since a 1999 publication, including the automatic layout capability, expansion of the cellular machinery that it includes, new semantic zooming and poster-generating capabilities, and extension of the Omics Viewer to support painting of metabolites, animations and zooming to individual pathway diagrams.

  3. A Community Based Systems Diagram of Obesity Causes.

    Science.gov (United States)

    Allender, Steven; Owen, Brynle; Kuhlberg, Jill; Lowe, Janette; Nagorcka-Smith, Phoebe; Whelan, Jill; Bell, Colin

    2015-01-01

    Application of system thinking to the development, implementation and evaluation of childhood obesity prevention efforts represents the cutting edge of community-based prevention. We report on an approach to developing a system oriented community perspective on the causes of obesity. Group model building sessions were conducted in a rural Australian community to address increasing childhood obesity. Stakeholders (n = 12) built a community model that progressed from connection circles to causal loop diagrams using scripts from the system dynamics literature. Participants began this work in identifying change over time in causes and effects of childhood obesity within their community. The initial causal loop diagram was then reviewed and elaborated by 50 community leaders over a full day session. The process created a causal loop diagram representing community perceptions of determinants and causes of obesity. The causal loop diagram can be broken down into four separate domains; social influences; fast food and junk food; participation in sport; and general physical activity. This causal loop diagram can provide the basis for community led planning of a prevention response that engages with multiple levels of existing settings and systems.

  4. Dynamic Project Risk Analysis and Management Based on Influence Diagrams

    Science.gov (United States)

    Liu, Xiaohua; Yue, Chaoyuan

    This paper presents a real-time process-oriented project risk analysis and management model which can be combined with the project general management, based on the hierarchical risk influence diagram which is constructed on the basis of network planning. Through network planning, it can solve the problems of the dynamic and overall identification of risk elements, and the showing and analysis of risk transfer along with the working procedure, and the timely and dynamic risk prevention and control as well. The influence diagram can effectively represent the risk combination and transfer in time and logic order. And it is good at the analysis of the sensitivity and control value of risk elements, as well as being convenient for communicating between experts, managers and owner. So the hierarchical risk influence diagram can make the decision of risk management timelier and more accurate. The problems of risk description, diagrams construction and risk evaluation are solved very well in applying the general influence diagram to dynamic project risk analysis. In the end, good result is attained in the example.

  5. Elastic properties of cubic crystals: Every's versus Blackman's diagram

    Science.gov (United States)

    Paszkiewicz, T.; Wolski, S.

    2008-03-01

    Blackman's diagram of two dimensionless ratios of elastic constants is frequently used to correlate elastic properties of cubic crystals with interatomic bondings. Every's diagram of a different set of two dimensionless variables was used by us for classification of various properties of such crystals. We compare these two ways of characterization of elastic properties of cubic materials and consider the description of various groups of materials, e.g. simple metals, oxides, and alkali halides. With exception of intermediate valent compounds, the correlation coefficients for Every's diagrams of various groups of materials are greater than for Blackaman's diagrams, revealing the existence of a linear relationship between two dimensionless Every's variables. Alignment of elements and compounds along lines of constant Poisson's ratio v(lang100rang, m), (m arbitrary perpendicular to lang100rang) is observed. Division of the stability region in Blackman's diagram into region of complete auxetics, auxetics and non-auxetics is introduced. Correlations of a scaling and an acoustic anisotropy parameter are considered.

  6. A Community Based Systems Diagram of Obesity Causes.

    Directory of Open Access Journals (Sweden)

    Steven Allender

    Full Text Available Application of system thinking to the development, implementation and evaluation of childhood obesity prevention efforts represents the cutting edge of community-based prevention. We report on an approach to developing a system oriented community perspective on the causes of obesity.Group model building sessions were conducted in a rural Australian community to address increasing childhood obesity. Stakeholders (n = 12 built a community model that progressed from connection circles to causal loop diagrams using scripts from the system dynamics literature. Participants began this work in identifying change over time in causes and effects of childhood obesity within their community. The initial causal loop diagram was then reviewed and elaborated by 50 community leaders over a full day session.The process created a causal loop diagram representing community perceptions of determinants and causes of obesity. The causal loop diagram can be broken down into four separate domains; social influences; fast food and junk food; participation in sport; and general physical activity.This causal loop diagram can provide the basis for community led planning of a prevention response that engages with multiple levels of existing settings and systems.

  7. Making star teams out of star players.

    Science.gov (United States)

    Mankins, Michael; Bird, Alan; Root, James

    2013-01-01

    Top talent is an invaluable asset: In highly specialized or creative work, for instance, "A" players are likely to be six times as productive as "B" players. So when your company has a crucial strategic project, why not multiply all that firepower and have a team of your best performers tackle it? Yet many companies hesitate to do this, believing that all-star teams don't work: Big egos will get in the way. The stars won't be able to work with one another. They'll drive the team Leader crazy. Mankins, Bird, and Root of Bain & Company believe it's time to set aside that thinking. They have seen all-star teams do extraordinary work. But there is a right way and a wrong way to organize them. Before you can even begin to assemble such a team, you need to have the right talent management practices, so you hire and develop the best people and know what they're capable of. You have to give the team appropriate incentives and leaders and support staffers who are stars in their own right. And projects that are ill-defined or small scale are not for all-star teams. Use them only for critical missions, and make sure their objectives are clear. Even with the right setup, things can still go wrong. The wise executive will take steps to manage egos, prune non-team-players, and prevent average coworkers from feeling completely undervalued. She will also invest a lot of time in choosing the right team Leader and will ask members for lots of feedback to monitor how that leader is doing.

  8. Pseudosynchronization of Heartbeat Stars

    Science.gov (United States)

    Zimmerman, Mara; Thompson, Susan E.; Hambleton, Kelly; Fuller, Jim; Shporer, Avi; Isaacson, Howard T.; Howard, Andrew; Kurtz, Donald

    2016-01-01

    A type of eccentric binary star that undergoes extreme dynamic tidal forces, known as Heartbeat stars, were discovered by the Kepler Mission. As the two stars pass through periastron, the tidal distortion causes unique brightness variations. Short period, eccentric binary stars, like these, are theorized to pseudosynchronize, or reach a rotational frequency that matches the weighted average orbital angular velocity of the system. This pseudosynchronous rate, as predicted by Hut (1981), depends on the binary's orbital period and eccentricity. We tested whether sixteen heartbeat stars have pseudosynchronized. We measure the rotation rate from obvious spot signatures in the light curve. We measure the eccentricity by fitting the light curve using PHOEBE and are actively carrying out a radial velocity monitoring program with Keck/HIRES in order to improve these orbital parameters. Our initial results show that while most heartbeat stars appear to have pseudosynchronized we find stars with rotation frequencies both longer and shorter than this rate. We thank the SETI Institute REU program, the NSF, and the Kepler Guest Observer Program for making this work possible.

  9. Dense Axion Stars.

    Science.gov (United States)

    Braaten, Eric; Mohapatra, Abhishek; Zhang, Hong

    2016-09-16

    If the dark matter particles are axions, gravity can cause them to coalesce into axion stars, which are stable gravitationally bound systems of axions. In the previously known solutions for axion stars, gravity and the attractive force between pairs of axions are balanced by the kinetic pressure. The mass of these dilute axion stars cannot exceed a critical mass, which is about 10^{-14}M_{⊙} if the axion mass is 10^{-4}  eV. We study axion stars using a simple approximation to the effective potential of the nonrelativistic effective field theory for axions. We find a new branch of dense axion stars in which gravity is balanced by the mean-field pressure of the axion Bose-Einstein condensate. The mass on this branch ranges from about 10^{-20}M_{⊙} to about M_{⊙}. If a dilute axion star with the critical mass accretes additional axions and collapses, it could produce a bosenova, leaving a dense axion star as the remnant.

  10. Cooling of Neutron Stars

    Directory of Open Access Journals (Sweden)

    Grigorian H.

    2010-10-01

    Full Text Available We introduce the theoretical basis for modeling the cooling evolution of compact stars starting from Boltzmann equations in curved space-time. We open a discussion on observational verification of different neutron star models by consistent statistics. Particular interest has the question of existence of quark matter deep inside of compact object, which has to have a specific influence on the cooling history of the star. Besides of consideration of several constraints and features of cooling evolution, which are susceptible of being critical for internal structure of hot compact stars we have introduced a method of extraction of the mass distribution of the neutron stars from temperature and age data. The resulting mass distribution has been compared with the one suggested by supernove simulations. This method can be considered as an additional checking tool for the consistency of theoretical modeling of neutron stars. We conclude that the cooling data allowed existence of neutron stars with quark cores even with one-flavor quark matter.

  11. Entropy Production of Stars

    Directory of Open Access Journals (Sweden)

    Leonid M. Martyushev

    2015-06-01

    Full Text Available The entropy production (inside the volume bounded by a photosphere of main-sequence stars, subgiants, giants, and supergiants is calculated based on B–V photometry data. A non-linear inverse relationship of thermodynamic fluxes and forces as well as an almost constant specific (per volume entropy production of main-sequence stars (for 95% of stars, this quantity lies within 0.5 to 2.2 of the corresponding solar magnitude is found. The obtained results are discussed from the perspective of known extreme principles related to entropy production.

  12. Hyperons in neutron stars

    Directory of Open Access Journals (Sweden)

    Tetsuya Katayama

    2015-07-01

    Full Text Available Using the Dirac–Brueckner–Hartree–Fock approach, the properties of neutron-star matter including hyperons are investigated. In the calculation, we consider both time and space components of the vector self-energies of baryons as well as the scalar ones. Furthermore, the effect of negative-energy states of baryons is partly taken into account. We obtain the maximum neutron-star mass of 2.08M⊙, which is consistent with the recently observed, massive neutron stars. We discuss a universal, repulsive three-body force for hyperons in matter.

  13. Infrared spectroscopy of stars

    Science.gov (United States)

    Merrill, K. M.; Ridgway, S. T.

    1979-01-01

    This paper reviews applications of IR techniques in stellar classification, studies of stellar photospheres, elemental and isotopic abundances, and the nature of remnant and ejected matter in near-circumstellar regions. Qualitative IR spectral classification of cool and hot stars is discussed, along with IR spectra of peculiar composite star systems and of obscured stars, and IR characteristics of stellar populations. The use of IR spectroscopy in theoretical modeling of stellar atmospheres is examined, IR indicators of stellar atmospheric composition are described, and contributions of IR spectroscopy to the study of stellar recycling of interstellar matter are summarized. The future of IR astronomy is also considered.

  14. Reexamination of Kerker's conditions by means of the phase diagram

    Science.gov (United States)

    Lee, Jeng Yi; Miroshnichenko, Andrey E.; Lee, Ray-Kuang

    2017-10-01

    For passive electromagnetic scatterers, we explore a variety of extreme limits on directional scattering patterns in a phase diagram, regardless of the details on the geometric configurations and material properties. By demonstrating the extinction cross sections with the power conservation intrinsically embedded in the phase diagram, we give an alternative interpretation for Kerker's first and second conditions, associated with zero backward scattering (ZBS) and nearly zero forward scattering (NZFS). Physical boundaries and limitations for these directional radiations are illustrated along with a generalized Kerker's condition with implicit parameters. By taking the dispersion relations of gold silicon core-shell nanoparticles into account, we reveal the realistic parameters to experimentally implement ZBS and NZFS at optical frequencies by means of a phase diagram.

  15. Anytime decision making based on unconstrained influence diagrams

    DEFF Research Database (Denmark)

    Luque, Manuel; Nielsen, Thomas Dyhre; Jensen, Finn Verner

    2016-01-01

    . This paper addresses this problem by proposing an anytime algorithm that at any time provides a qualified recommendation for the first decisions of the problem. The algorithm performs a heuristic-based search in a decision tree representation of the problem. We provide a framework for analyzing......Unconstrained influence diagrams extend the language of influence diagrams to cope with decision problems in which the order of the decisions is unspecified. Thus, when solving an unconstrained influence diagram we not only look for an optimal policy for each decision, but also for a so-called step......-policy specifying the next decision given the observations made so far. However, due to the complexity of the problem, temporal constraints can force the decision maker to act before the solution algorithm has finished, and, in particular, before an optimal policy for the first decision has been computed...

  16. UML activity diagrams in requirements specification of logic controllers

    Science.gov (United States)

    Grobelna, Iwona; Grobelny, Michał

    2015-12-01

    Logic controller specification can be prepared using various techniques. One of them is the wide understandable and user-friendly UML language and its activity diagrams. Using formal methods during the design phase increases the assurance that implemented system meets the project requirements. In the approach we use the model checking technique to formally verify a specification against user-defined behavioral requirements. The properties are usually defined as temporal logic formulas. In the paper we propose to use UML activity diagrams in requirements definition and then to formalize them as temporal logic formulas. As a result, UML activity diagrams can be used both for logic controller specification and for requirements definition, what simplifies the specification and verification process.

  17. Phase diagrams of low-density polyethylene-alkylbenzene systems

    Science.gov (United States)

    Ilyasova, A. N.; Kudryavtsev, Y. V.; Lebedeva, T. N.; Levashova, I. V.; Flyagina, Yu. A.; Pochivalov, K. V.

    2017-03-01

    Complete phase diagrams for mixtures of low-density polyethylene with p- and m-xylene are plotted by optical means in developing the concept of which partially crystalline polymers are microstructured liquids. It is shown that in contrast to the ones presented in the literature, both diagrams contain the solubility boundary curve of the low-molecular weight component in the polymer, above which the polyethylene has the structure of a single-phase gel (crosslinks formed by crystallites and amorphous regions saturated with xylene). At the figurative point on the diagrams, a situation is observed in which the dissolution of all the liquid contained in the initial two-phase system in the polymer is accompanied by its simultaneous complete amorphization. The parameters of the figurative point allow us to estimate the thermodynamic affinity of different alkylbenzenes toward polyethylene.

  18. Generation of Finite Life Distributional Goodman Diagrams for Reliability Prediction

    Science.gov (United States)

    Kececioglu, D.; Guerrieri, W. N.

    1971-01-01

    The methodology of developing finite life distributional Goodman diagrams and surfaces is described for presenting allowable combinations of alternating stress and mean stress to the design engineer. The combined stress condition is that of an alternating bending stress and a constant shear stress. The finite life Goodman diagrams and surfaces are created from strength distributions developed at various ratios of alternating to mean stress at particular cycle life values. The conclusions indicate that the Von Mises-Hencky ellipse, for cycle life values above 1000 cycles, is an adequate model of the finite life Goodman diagram. In addition, suggestions are made which reduce the number of experimental data points required in a fatigue data acquisition program.

  19. Generalized internal multiple imaging (GIMI) using Feynman-like diagrams

    KAUST Repository

    Zuberi, M. A. H.

    2014-05-19

    Single scattering events recorded in surface seismic data do not fully illuminate the subsurface structure, especially if it is complicated. In such cases, multiple internal scatterings (internal multiples) can help improve the illumination. We devise a generalized internal multiple imaging (GIMI) procedure that maps internal multiple energy to their true location with a relatively mild addition to the computational cost. GIMI theory relies heavily on seismic interferometry, which often involves cumbersome algebra, especially when one is dealing with high-order terms in the perturbation series. To make the derivations, and inference of the results easier, we introduce Feynman-like diagrams to represent different terms of the perturbation series (solution to the Lippman–Schwinger equation). The rules we define for the diagrams allow operations like convolution and cross-correlation in the series to be compressed in diagram form. The application of the theory to a double scattering example demonstrates the power of the method.

  20. On the impact of layout quality to understanding UML diagrams

    DEFF Research Database (Denmark)

    Störrle, Harald

    2011-01-01

    Practical experience suggests that use and understanding of UML diagrams is greatly affected by the quality of their layout. However, existing experimental evidence for this effect is been weak and inconclusive. In this paper, we explore two explanations. Firstly, we observe that the visual...... qualities of diagrams are more prominent in earlier life cycle phases so that the impact of layout quality should be more apparent in models and diagram types used there, an aspect not studied in previous research. Secondly, in practice, good layouts use many different heuristics simultaneously whereas...... previous research considered them in isolation only. In this paper, we report the results of a series of controlled experiments using compound layouts on requirements analysis models. With very high significance, we find a notable impact of the layout quality measured by different aspects of cognitive load....

  1. The limit shape problem for ensembles of Young diagrams

    CERN Document Server

    Hora, Akihito

    2016-01-01

    This book treats ensembles of Young diagrams originating from group-theoretical contexts and investigates what statistical properties are observed there in a large-scale limit. The focus is mainly on analyzing the interesting phenomenon that specific curves appear in the appropriate scaling limit for the profiles of Young diagrams. This problem is regarded as an important origin of recent vital studies on harmonic analysis of huge symmetry structures. As mathematics, an asymptotic theory of representations is developed of the symmetric groups of degree n as n goes to infinity. The framework of rigorous limit theorems (especially the law of large numbers) in probability theory is employed as well as combinatorial analysis of group characters of symmetric groups and applications of Voiculescu's free probability. The central destination here is a clear description of the asymptotic behavior of rescaled profiles of Young diagrams in the Plancherel ensemble from both static and dynamic points of view.

  2. Program design by a multidisciplinary team. [for structural finite element analysis on STAR-100 computer

    Science.gov (United States)

    Voigt, S.

    1975-01-01

    The use of software engineering aids in the design of a structural finite-element analysis computer program for the STAR-100 computer is described. Nested functional diagrams to aid in communication among design team members were used, and a standardized specification format to describe modules designed by various members was adopted. This is a report of current work in which use of the functional diagrams provided continuity and helped resolve some of the problems arising in this long-running part-time project.

  3. Influence Diagram Use With Respect to Technology Planning and Investment

    Science.gov (United States)

    Levack, Daniel J. H.; DeHoff, Bryan; Rhodes, Russel E.

    2009-01-01

    Influence diagrams are relatively simple, but powerful, tools for assessing the impact of choices or resource allocations on goals or requirements. They are very general and can be used on a wide range of problems. They can be used for any problem that has defined goals, a set of factors that influence the goals or the other factors, and a set of inputs. Influence diagrams show the relationship among a set of results and the attributes that influence them and the inputs that influence the attributes. If the results are goals or requirements of a program, then the influence diagram can be used to examine how the requirements are affected by changes to technology investment. This paper uses an example to show how to construct and interpret influence diagrams, how to assign weights to the inputs and attributes, how to assign weights to the transfer functions (influences), and how to calculate the resulting influences of the inputs on the results. A study is also presented as an example of how using influence diagrams can help in technology planning and investment. The Space Propulsion Synergy Team (SPST) used this technique to examine the impact of R&D spending on the Life Cycle Cost (LCC) of a space transportation system. The question addressed was the effect on the recurring and the non-recurring portions of LCC of the proportion of R&D resources spent to impact technology objectives versus the proportion spent to impact operational dependability objectives. The goals, attributes, and the inputs were established. All of the linkages (influences) were determined. The weighting of each of the attributes and each of the linkages was determined. Finally the inputs were varied and the impacts on the LCC determined and are presented. The paper discusses how each of these was accomplished both for credibility and as an example for future studies using influence diagrams for technology planning and investment planning.

  4. Radial velocity variations of photometrically quiet, chromospherically inactive Kepler stars: A link between RV jitter and photometric flicker

    Energy Technology Data Exchange (ETDEWEB)

    Bastien, Fabienne A.; Stassun, Keivan G.; Pepper, Joshua [Physics and Astronomy Department, Vanderbilt University, 1807 Station B, Nashville, TN 37235 (United States); Wright, Jason T. [Center for Exoplanets and Habitable Worlds, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16803 (United States); Aigrain, Suzanne [Sub-department of Astrophysics, Department of Physics, University of Oxford, Oxford OX1 3RH (United Kingdom); Basri, Gibor [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Johnson, John A. [Department of Astrophysics, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Howard, Andrew W. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Walkowicz, Lucianne M. [Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544 (United States)

    2014-02-01

    We compare stellar photometric variability, as measured from Kepler light curves by Basri et al., with measurements of radial velocity (RV) rms variations of all California Planet Search overlap stars. We newly derive rotation periods from the Kepler light curves for all of the stars in our study sample. The RV variations reported herein range from less than 4 to 135 m s{sup –1}, yet the stars all have amplitudes of photometric variability less than 3 mmag, reflecting the preference of the RV program for chromospherically 'quiet' stars. Despite the small size of our sample, we find with high statistical significance that the RV rms manifests strongly in the Fourier power spectrum of the light curve: stars that are noisier in RV have a greater number of frequency components in the light curve. We also find that spot models of the observed light curves systematically underpredict the observed RV variations by factors of ∼2-1000, likely because the low-level photometric variations in our sample are driven by processes not included in simple spot models. The stars best fit by these models tend to have simpler light curves, dominated by a single relatively high-amplitude component of variability. Finally, we demonstrate that the RV rms behavior of our sample can be explained in the context of the photometric variability evolutionary diagram introduced by Bastien et al. We use this diagram to derive the surface gravities of the stars in our sample, revealing many of them to have moved off the main sequence. More generally, we find that the stars with the largest RV rms are those that have evolved onto the 'flicker floor' sequence in that diagram, characterized by relatively low amplitude but highly complex photometric variations which grow as the stars evolve to become subgiants.

  5. GPU based detection of topological changes in Voronoi diagrams

    Science.gov (United States)

    Bernaschi, M.; Lulli, M.; Sbragaglia, M.

    2017-04-01

    The Voronoi diagrams are an important tool having theoretical and practical applications in a large number of fields. We present a new procedure, implemented as a set of CUDA kernels, which detects, in a general and efficient way, topological changes in case of dynamic Voronoi diagrams whose generating points move in time. The solution that we provide has been originally developed to identify plastic events during simulations of soft-glassy materials based on a lattice Boltzmann model with frustrated-short range attractive and mid/long-range repulsive-interactions. Along with the description of our approach, we present also some preliminary physics results.

  6. Microsoft Visio 2013 business process diagramming and validation

    CERN Document Server

    Parker, David

    2013-01-01

    Microsoft Visio 2013 Business Process Diagramming and Validation provides a comprehensive and practical tutorial including example code and demonstrations for creating validation rules, writing ShapeSheet formulae, and much more.If you are a Microsoft Visio 2013 Professional Edition power user or developer who wants to get to grips with both the essential features of Visio 2013 and the validation rules in this edition, then this book is for you. A working knowledge of Microsoft Visio and optionally .NET for the add-on code is required, though previous knowledge of business process diagramming

  7. An automatic system for elaboration of chip breaking diagrams

    DEFF Research Database (Denmark)

    Andreasen, Jan Lasson; De Chiffre, Leonardo

    1998-01-01

    A laboratory system for fully automatic elaboration of chip breaking diagrams has been developed and tested. The system is based on automatic chip breaking detection by frequency analysis of cutting forces in connection with programming of a CNC-lathe to scan different feeds, speeds and cutting...... depths. An evaluation of the system based on a total of 1671 experiments has shown that unfavourable snarled chips can be detected with 98% certainty which indeed makes the system a valuable tool in chip breakability tests. Using the system, chip breaking diagrams can be elaborated with a previously...

  8. Phase diagram of the lattice SU(2) Higgs model

    Energy Technology Data Exchange (ETDEWEB)

    Bonati, C., E-mail: bonati@df.unipi.i [Dipartimento di Fisica and INFN, Pisa (Italy); Cossu, G., E-mail: cossu@post.kek.j [Scuola Normale Superiore and INFN, Pisa (Italy); D' Elia, M., E-mail: Massimo.Delia@ge.infn.i [Dipartimento di Fisica and INFN, Genova (Italy); Di Giacomo, A., E-mail: digiaco@df.unipi.i [Dipartimento di Fisica and INFN, Pisa (Italy)

    2010-03-21

    We perform a detailed study of the phase diagram of the lattice Higgs SU(2) model with fixed Higgs field length. Consistently with previsions based on the Fradkin-Shenker theorem we find a first order transition line with an endpoint whose position we determined. The diagram also shows cross-over lines: the cross-over corresponding to the pure SU(2) bulk is also present at nonzero coupling with the Higgs field and merges with the one that continues the line of first order transition beyond the critical endpoint. At high temperature the first order line becomes a crossover, whose position moves by varying the temperature.

  9. Choking Affects the Operation Diagram of a CFB Riser

    Directory of Open Access Journals (Sweden)

    H. L. Zhang

    2014-01-01

    Full Text Available Experiments in 3 different CFB risers have confirmed that common riser operations can be hampered in a well-defined (U, G range where choking occurs. Geldart A-type powders were investigated. Experimental results of the choking velocity were empirically correlated, being about 30% lower than predicted by the correlation of Bi and Fan, but largely exceeding other predictions. Introducing the findings into the operation diagram presented by Mahmoudi et al. adds a region where stable riser operation is impossible. The adapted diagram enables CFB designers to better delineate the operating characteristics.

  10. UML activity diagram swimlanes in logic controller design

    Science.gov (United States)

    Grobelny, Michał; Grobelna, Iwona

    2015-12-01

    Logic controller behavior can be specified using various techniques, including UML activity diagrams and control Petri nets. Each technique has its advantages and disadvantages. Application of both specification types in one project allows to take benefits from both of them. Additional elements of UML models make it possible to divide a specification into some parts, considered from other point of view (logic controller, user or system). The paper introduces an idea to use UML activity diagrams with swimlanes to increase the understandability of design models.

  11. A descriptive notation system for contingency diagramming in behavior analysis

    Science.gov (United States)

    Goldwater, Bram C.; Acker, Loren E.

    1995-01-01

    We describe a notation system for diagramming behavioral contingencies. The system is descriptive. Stimulus functions are not represented with special symbols, such as SR, SD, or UCS, but are simply described in terms of the relation between behavior and stimulus change, and the resulting outcome. The system is atheoretical, self-explanatory, and easy to use. Our goal is to provide an approach to contingency diagramming for the student that represents directly the exact relations and outcomes involved in operant and respondent processes. PMID:22478210

  12. Equivalence Checking of Combinational Circuits using Boolean Expression Diagrams

    DEFF Research Database (Denmark)

    Hulgaard, Henrik; Williams, Poul Frederick; Andersen, Henrik Reif

    1999-01-01

    The combinational logic-level equivalence problem is to determine whether two given combinational circuits implement the same Boolean function. This problem arises in a number of CAD applications, for example when checking the correctness of incremental design changes (performed either manually...... or by a design automation tool).This paper introduces a data structure called Boolean Expression Diagrams (BEDs) and two algorithms for transforming a BED into a Reduced Ordered Binary Decision Diagram (OBDD). BEDs are capable of representing any Boolean circuit in linear space and can exploit structural...

  13. Theory and evidence of global Rossby waves in upper main-sequence stars: r-mode oscillations in many Kepler stars

    Science.gov (United States)

    Saio, Hideyuki; Kurtz, Donald W.; Murphy, Simon J.; Antoci, Victoria L.; Lee, Umin

    2018-02-01

    Asteroseismic inference from pressure modes (p modes) and buoyancy, or gravity, modes (g modes) is ubiquitous for stars across the Hertzsprung-Russell diagram. Until now, however, discussion of r modes (global Rossby waves) has been rare. Here we derive the expected frequency ranges of r modes in the observational frame by considering the visibility of these modes. We find that the frequencies of r modes of azimuthal order m appear as groups at slightly lower frequency than m times the rotation frequency. Comparing the visibility curves for r modes with Fourier amplitude spectra of Kepler light curves of upper main-sequence B, A, and F stars, we find that r modes are present in many γ Dor stars (as first discovered by Van Reeth et al.), spotted stars, and so-called heartbeat stars, which are highly eccentric binary stars. We also find a signature of r modes in a frequently bursting Be star observed by Kepler. In the amplitude spectra of moderately to rapidly rotating γ Dor stars, r-mode frequency groups appear at lower frequency than prograde g-mode frequency groups, while in the amplitude spectra of spotted early A to B stars, groups of symmetric (with respect to the equator) r-mode frequencies appear just below the frequency of a structured peak that we suggest represents an approximate stellar rotation rate. In many heartbeat stars, a group of frequencies can be fitted with symmetric m = 1 r modes, which can be used to obtain rotation frequencies of these stars.

  14. Dance of the double stars

    Energy Technology Data Exchange (ETDEWEB)

    Theokas, A.

    1985-09-19

    The paper concerns pairs of stars orbiting one another. The evolutionary path model for close binary stars, involving a mass transfer of gases between the stars, is described. The life history of a single star; cataclysmic variables; the algol paradox, matter and lagranges' point; x-ray binaries and bursters; and pulsars; are all briefly discussed.

  15. Observational Effects of Strange Stars

    OpenAIRE

    Lu, T.

    1998-01-01

    In this talk, after briefly reviewing some historical remarks concerning strange stars, the achievements in physics and dynamical behavior of strange stars are discussed. Especially, various observational effects in distinguishing strange stars from neutron stars such as mechanical effects, cooling effects, phase transition and related interesting phenomena are stressed.

  16. THE CARINA PROJECT. VI. THE HELIUM-BURNING VARIABLE STARS

    Energy Technology Data Exchange (ETDEWEB)

    Coppola, G.; Marconi, M.; Ripepi, V.; Dall' Ora, M.; Musella, I. [INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, I-80131 Napoli (Italy); Stetson, P. B. [Dominion Astrophysical Observatory, NRC-Herzberg, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Bono, G.; Buonanno, R. [Dipartimento di Fisica-Universita di Roma Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Roma (Italy); Fabrizio, M. [INAF-Osservatorio Astronomico di Collurania, via M. Maggini, I-64100 Teramo (Italy); Ferraro, I.; Iannicola, G.; Pulone, L. [INAF-Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monte Porzio Catone (Italy); Fiorentino, G. [INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Monelli, M. [Instituto de Astrofisica de Canarias, Calle Via Lactea s/n, E-38205 La Laguna, Tenerife (Spain); Nonino, M. [INAF-Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, I-40131 Trieste (Italy); Thevenin, F. [Universite de Nice-Sophia Antipolis, Lab. Lagrange, UMR 7293, Observatoire de la Cote dAzur, BP 4229, F-06304 Nice (France); Walker, A. R., E-mail: coppola@na.astro.it [Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603, La Serena (Chile)

    2013-09-20

    We present new optical (BVI) time-series data for the evolved variable stars in the Carina dwarf spheroidal galaxy. The quality of the data and the observing strategy allowed us to identify 14 new variable stars. Eight out of the 14 are RR Lyrae (RRL) stars, 4 are Anomalous Cepheids (ACs), and 2 are geometrical variables. Comparison of the period distribution for the entire sample of RRLs with similar distributions in nearby dwarf spheroidal galaxies and in the Large Magellanic Cloud indicates that the old stellar populations in these systems share similar properties. This finding is also supported by the RRL distribution in the Bailey diagram. On the other hand, the period distribution and the Bailey diagram of ACs display significant differences among the above stellar systems. This evidence suggests that the properties of intermediate-age stellar populations might be affected both by environmental effects and structural parameters. We use the BV Period-Wesenheit (PW) relation of RRLs together with evolutionary prescriptions and find a true distance modulus of 20.09 {+-} 0.07 (intrinsic) {+-} 0.1 (statistical) mag that agrees quite well with similar estimates available in the literature. We identified four peculiar variables. Taking into account their position in the Bailey diagram and in the BV PW relation, two of them (V14 and V149) appear to be candidate ACs, while two (V158 and V182) might be peculiar RRLs. In particular, the variable V158 has a period and a V-band amplitude very similar to the low-mass RRL-RRLR-02792-recently identified by Pietrzynski et al. in the Galactic bulge.

  17. Interferometric star tracker Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Optical Physics Company (OPC) proposes to develop a high accuracy version of its interferometric star tracker capable of meeting the milli-arcsecond-level pointing...

  18. Principles of star formation

    CERN Document Server

    Bodenheimer, Peter H

    2011-01-01

    Understanding star formation is one of the key fields in present-day astrophysics. This book treats a wide variety of the physical processes involved, as well as the main observational discoveries, with key points being discussed in detail. The current star formation in our galaxy is emphasized, because the most detailed observations are available for this case. The book presents a comparison of the various scenarios for star formation, discusses the basic physics underlying each one, and follows in detail the history of a star from its initial state in the interstellar gas to its becoming a condensed object in equilibrium. Both theoretical and observational evidence to support the validity of the general evolutionary path are presented, and methods for comparing the two are emphasized. The author is a recognized expert in calculations of the evolution of protostars, the structure and evolution of disks, and stellar evolution in general. This book will be of value to graduate students in astronomy and astroph...

  19. Sounds of a Star

    Science.gov (United States)

    2001-06-01

    Acoustic Oscillations in Solar-Twin "Alpha Cen A" Observed from La Silla by Swiss Team Summary Sound waves running through a star can help astronomers reveal its inner properties. This particular branch of modern astrophysics is known as "asteroseismology" . In the case of our Sun, the brightest star in the sky, such waves have been observed since some time, and have greatly improved our knowledge about what is going on inside. However, because they are much fainter, it has turned out to be very difficult to detect similar waves in other stars. Nevertheless, tiny oscillations in a solar-twin star have now been unambiguously detected by Swiss astronomers François Bouchy and Fabien Carrier from the Geneva Observatory, using the CORALIE spectrometer on the Swiss 1.2-m Leonard Euler telescope at the ESO La Silla Observatory. This telescope is mostly used for discovering exoplanets (see ESO PR 07/01 ). The star Alpha Centauri A is the nearest star visible to the naked eye, at a distance of a little more than 4 light-years. The new measurements show that it pulsates with a 7-minute cycle, very similar to what is observed in the Sun . Asteroseismology for Sun-like stars is likely to become an important probe of stellar theory in the near future. The state-of-the-art HARPS spectrograph , to be mounted on the ESO 3.6-m telescope at La Silla, will be able to search for oscillations in stars that are 100 times fainter than those for which such demanding observations are possible with CORALIE. PR Photo 23a/01 : Oscillations in a solar-like star (schematic picture). PR Photo 23b/01 : Acoustic spectrum of Alpha Centauri A , as observed with CORALIE. Asteroseismology: listening to the stars ESO PR Photo 23a/01 ESO PR Photo 23a/01 [Preview - JPEG: 357 x 400 pix - 96k] [Normal - JPEG: 713 x 800 pix - 256k] [HiRes - JPEG: 2673 x 3000 pix - 2.1Mb Caption : PR Photo 23a/01 is a graphical representation of resonating acoustic waves in the interior of a solar-like star. Red and blue

  20. Catch a Star 2008!

    Science.gov (United States)

    2007-10-01

    ESO and the European Association for Astronomy Education have just launched the 2008 edition of 'Catch a Star', their international astronomy competition for school students. Now in its sixth year, the competition offers students the chance to win a once-in-a-lifetime trip to ESO's flagship observatory in Chile, as well as many other prizes. CAS logo The competition includes separate categories - 'Catch a Star Researchers' and 'Catch a Star Adventurers' - to ensure that every student, whatever their level, has the chance to enter and win exciting prizes. In teams, students investigate an astronomical topic of their choice and write a report about it. An important part of the project for 'Catch a Star Researchers' is to think about how ESO's telescopes such as the Very Large Telescope (VLT) or future telescopes such as the Atacama Large Millimeter/submillimeter Array (ALMA) and the European Extremely Large Telescope (E-ELT) could contribute to investigations of the topic. Students may also include practical activities such as observations or experiments. For the artistically minded, 'Catch a Star' also offers an artwork competition, 'Catch a Star Artists'. Last year, hundreds of students from across Europe and beyond took part in 'Catch a Star', submitting astronomical projects and artwork. "'Catch a Star' gets students thinking about the wonders of the Universe and the science of astronomy, with a chance of winning great prizes. It's easy to take part, whether by writing about astronomy or creating astronomically inspired artwork," said Douglas Pierce-Price, Education Officer at ESO. As well as the top prize - a trip to ESO's Very Large Telescope in Chile - visits to observatories in Austria and Spain, and many other prizes, can also be won. 'Catch a Star Researchers' winners will be chosen by an international jury, and 'Catch a Star Adventurers' will be awarded further prizes by lottery. Entries for 'Catch a Star Artists' will be displayed on the web and winners

  1. STAR: Copperhead interface

    OpenAIRE

    Cahill, Thomas Everett

    1981-01-01

    Approved for public release; distribution is unlimited This thesis provides the general design logic for a computer representation of the Field Artillery's precision guided munition- Copperhead. The design has been specifically structured to enable its integration into the Simulation of Tactical Alternative Responses (STAR) model. (STAR is a stochastic force-on-force combat simulation.) Routines and events are developed which portray the target identification, target selection, firing a...

  2. On the Origin of Sub-subgiant Stars. I. Demographics

    Energy Technology Data Exchange (ETDEWEB)

    Geller, Aaron M. [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60201 (United States); Leiner, Emily M.; Mathieu, Robert D. [Department of Astronomy, University of Wisconsin–Madison, 475 North Charter Street, Madison, WI 53706 (United States); Bellini, Andrea; Watkins, Laura L. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Gleisinger, Robert; Haggard, Daryl [Department of Physics, McGill University, McGill Space Institute, 3550 University Street, Montreal, QC H3A 2A7 (Canada); Kamann, Sebastian [Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Leigh, Nathan W. C.; Zurek, David [Department of Astrophysics, American Museum of Natural History, Central Park West and 79th Street, New York, NY 10024 (United States); Sills, Alison, E-mail: a-geller@northwestern.edu [Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 (Canada)

    2017-05-10

    Sub-subgiants are stars that are observed to be redder than normal main-sequence stars and fainter than normal subgiant (and giant) stars in an optical color–magnitude diagram (CMD). The red straggler stars, which lie redward of the red giant branch, may be related and are often grouped together with the sub-subgiants in the literature. These stars defy our standard theory of single-star evolution and are important tests for binary evolution and stellar collision models. In total, we identify 65 sub-subgiants (SSG) and red stragglers (RS) in 16 open and globular star clusters from the literature; 50 of these, including 43 sub-subgiants, pass our strict membership selection criteria (though the remaining sources may also be cluster members). In addition to their unique location on the CMD, we find that at least 58% (25/43) of sub-subgiants in this sample are X-ray sources with typical 0.5–2.5 keV luminosities of order 10{sup 30}–10{sup 31} erg s{sup −1}. Their X-ray luminosities and optical–to–X-ray flux ratios are similar to those of RS CVn active binaries. At least 65% (28/43) of the sub-subgiants in our sample are variables, 21 of which are known to be radial-velocity binaries. Typical variability periods are ≲15 days. At least 33% (14/43) of the sub-subgiants are H α emitters. These observational demographics provide strong evidence that binarity is important for sub-subgiant formation. Finally, we find that the number of sub-subgiants per unit mass increases toward lower-mass clusters, such that the open clusters in our sample have the highest specific frequencies of sub-subgiants.

  3. HUBBLE SPACE TELESCOPE CAPTURES FIRST DIRECT IMAGE OF A STAR

    Science.gov (United States)

    2002-01-01

    This is the first direct image of a star other than the Sun, made with NASA's Hubble Space Telescope. Called Alpha Orionis, or Betelgeuse, it is a red supergiant star marking the shoulder of the winter constellation Orion the Hunter (diagram at right). The Hubble image reveals a huge ultraviolet atmosphere with a mysterious hot spot on the stellar behemoth's surface. The enormous bright spot, more than ten times the diameter of Earth, is at least 2,000 Kelvin degrees hotter than the surface of the star. The image suggests that a totally new physical phenomenon may be affecting the atmospheres of some stars. Follow-up observations will be needed to help astronomers understand whether the spot is linked to oscillations previously detected in the giant star, or whether it moves systematically across the star's surface under the grip of powerful magnetic fields. The observations were made by Andrea Dupree of the Harvard- Smithsonian Center for Astrophysics in Cambridge, MA, and Ronald Gilliland of the Space Telescope Science Institute in Baltimore, MD, who announced their discovery today at the 187th meeting of the American Astronomical Society in San Antonio, Texas. The image was taken in ultraviolet light with the Faint Object Camera on March 3, 1995. Hubble can resolve the star even though the apparent size is 20,000 times smaller than the width of the full Moon -- roughly equivalent to being able to resolve a car's headlights at a distance of 6,000 miles. Betelgeuse is so huge that, if it replaced the Sun at the center of our Solar System, its outer atmosphere would extend past the orbit of Jupiter (scale at lower left). Credit: Andrea Dupree (Harvard-Smithsonian CfA), Ronald Gilliland (STScI), NASA and ESA Image files in GIF and JPEG format and captions may be accessed on Internet via anonymous ftp from oposite.stsci.edu in /pubinfo.

  4. Characterizing bursty star formation

    Science.gov (United States)

    Emami, Najmeh

    2018-01-01

    An ongoing area of research in galaxy evolution is the efficiency of star formation as a function of galaxy halo mass. At low mass, it is believed that supernova feedback can expel gas from the galaxy and shut down star formation. However, there are still significant uncertainties in how the momentum/energy of the supernova couple with the gas and the efficiency with which it drives winds. Particularly uncertain are the parameters of the resulting bursts of star formation —amplitudes, durations, and periods — with important implications for interpreting observations of dwarf galaxies. Some hydrodynamical simulations predict order of magnitude bursts (and quenching) on very short (indicators of dwarf galaxies (H-alpha and ultraviolet luminosities) that trace star formation on different time scales (~5 Myr and ~20 Myr, respectively), as well as their relation to the average galaxies of similar stellar mass, to better constrain the parameters of the star formation bursts. We find that the burst amplitude increases with decreasing stellar mass, with amplitudes ranging two orders of magnitude at stellar masses of 10^7. We also find that the star formation is quenched very rapidly, with e-folding times less than 10 Myr in galaxies with stellar masses less than 10^(7.5). We conclude by comparing our results to recent hydrodynamical simulations and discussing the effects of stochastic sampling of the stellar initial mass function.

  5. Collapsing Enormous Stars

    Science.gov (United States)

    Kohler, Susanna

    2015-09-01

    One of the big puzzles in astrophysics is how supermassive black holes (SMBHs) managed to grow to the large sizes weve observed in the very early universe. In a recent study, a team of researchers examines the possibility that they were formed by the direct collapse of supermassive stars.Formation MysterySMBHs billions of times as massive as the Sun have been observed at a time when the universe was less than a billion years old. But thats not enough time for a stellar-mass black hole to grow to SMBH-size by accreting material so another theory is needed to explain the presence of these monsters so early in the universes history. A new study, led by Tatsuya Matsumoto (Kyoto University, Japan), poses the following question: what if supermassive stars in the early universe collapsed directly into black holes?Previous studies of star formation in the early universe have suggested that, in the hot environment of these primordial times, stars might have been able to build up mass much faster than they can today. This could result in early supermassive stars roughly 100,000 times more massive than the Sun. But if these early stars end their lives by collapsing to become massive black holes in the same way that we believe massive stars can collapse to form stellar-mass black holes today this should result in enormously violent explosions. Matusmoto and collaborators set out to model this process, to determine what we would expect to see when it happens!Energetic BurstsThe authors modeled the supermassive stars prior to collapse and then calculated whether a jet, created as the black hole grows at the center of the collapsing star, would be able to punch out of the stellar envelope. They demonstrated that the process would work much like the widely-accepted collapsar model of massive-star death, in which a jet successfully punches out of a collapsing star, violently releasing energy in the form of a long gamma-ray burst (GRB).Because the length of a long GRB is thought to

  6. DIAGRAM SOLVE THE USE OF SIMULINK BLOCK DIAGRAM TO SOLVE MATHEMA THEMATICAL CONTROL EQU MATHEMATICAL MODELS AND CONTROL EQUATIONS

    Directory of Open Access Journals (Sweden)

    N.M. Ghasem

    2003-12-01

    Full Text Available In this paper, the simulink block diagram is used to solve a model consists of a set of ordinary differential and algebraic equations to control the temperature inside a simple stirred tank heater. The flexibility of simulink block diagram gives students a better understanding of the control systems. The simulink also allows solution of mathematical models and easy visualization of the system variables. A polyethylene fluidized bed reactor is considered as an industrial example and the effect of the Proportional, Integral and Derivative control policy is presented for comparison.

  7. Cognitive Activities in Complex Science Text and Diagrams

    Science.gov (United States)

    Cromley, Jennifer G.; Snyder-Hogan, Lindsey E.; Luciw-Dubas, Ulana A.

    2010-01-01

    Ainsworth's (2006) DeFT framework posits that different representations may lead learners to use different strategies. We wanted to investigate whether students use different strategies, and more broadly, different cognitive activities in diagrams vs. in running text. In order to do so, we collected think-aloud protocol and other measures from 91…

  8. Integrating Mathematics and Science: Ecology and Venn Diagrams

    Science.gov (United States)

    Leszczynski, Eliza; Munakata, Mika; Evans, Jessica M.; Pizzigoni, Francesca

    2014-01-01

    Efforts to integrate mathematics and science have been widely recognized by mathematics and science educators. However, successful integration of these two important school disciplines remains a challenge. In this article, a mathematics and science activity extends the use of Venn diagrams to a life science context and then circles back to a…

  9. A cut-away diagram of the DELPHI experiment

    CERN Multimedia

    1996-01-01

    A diagram of the DELPHI end-cap and barrel. Detectors are used in layers to detect different particles produced by the collisions in the beam pipe at the vertex detector. Each detector makes many different measurements, which are read off to a system of computers for analysis.

  10. Visualising Knowledge from Chat Debates in Argument Diagrams

    Science.gov (United States)

    Salminen, T.; Marttunen, M.; Laurinen, L.

    2010-01-01

    This study investigates whether combining chat discussion and construction of an argument diagram stimulates students to formulate new ideas in practising argumentation. In this study, 16 secondary school students discussed vivisection and gender equality in pairs using both free and structured chat tools. In structured chat, the students selected…

  11. Expanding Application of the Wiggers Diagram to Teach Cardiovascular Physiology

    Science.gov (United States)

    Mitchell, Jamie R.; Wang, Jiun-Jr

    2014-01-01

    Dr. Carl Wiggers' careful observations have provided a meaningful resource for students to learn how the heart works. Throughout the many years from his initial reports, the Wiggers diagram has been used, in various degrees of complexity, as a fundamental tool for cardiovascular instruction. Often, the various electrical and mechanical plots…

  12. Phase diagram for droplet impact on superheated surfaces

    NARCIS (Netherlands)

    Staat, Erik-Jan; Tran, Tuan; Geerdink, B.M.; Riboux, G.; Sun, Chao; Gordillo, J.M.; Lohse, Detlef

    2015-01-01

    We experimentally determine the phase diagram for impacting ethanol droplets on a smooth, sapphire surface in the parameter space of Weber number We versus surface temperature T. We observe two transitions, namely the one towards splashing (disintegration of the droplet) with increasing We, and the

  13. Using Photographs and Diagrams to Test Young Children's Mass Thinking

    Science.gov (United States)

    Cheeseman, Jill; McDonough, Andrea

    2013-01-01

    This paper reports the results of a pencil-and-paper test developed to assess young children's understanding of mass measurement. The innovative element of the test was its use of photographs. We found many children of the 295 6-8 year-old children tested could "read" the photographs and diagrams and recognise the images as…

  14. Bifurcation diagrams in relation to synchronization in chaotic systems

    Indian Academy of Sciences (India)

    We numerically study some of the three-dimensional dynamical systems which exhibit complete synchronization as well as generalized synchronization to show that these systems can be conveniently partitioned into equivalent classes facilitating the study of bifurcation diagrams within each class. We demonstrate how ...

  15. Riparian Sediment Delivery Ratio: Stiff Diagrams and Artifical Neural Networks

    Science.gov (United States)

    Various methods are used to estimate sediment transport through riparian buffers and grass jilters with the sediment delivery ratio having been the most widely applied. The U.S. Forest Service developed a sediment delivery ratio using the stiff diagram and a logistic curve to int...

  16. Threshold queueing describes the fundamental diagram of uninterrupted traffic

    NARCIS (Netherlands)

    Baër, Niek; Boucherie, Richardus J.; van Ommeren, Jan C.W.

    2012-01-01

    Queueing due to congestion is an important aspect of road traffic. This paper provides a brief overview of queueing models for traffic and a novel threshold queue that captures the main aspects of the empirical shape of the fundamental diagram. Our numerical results characterises the sources of

  17. Interpreting Evolutionary Diagrams: When Topology and Process Conflict

    Science.gov (United States)

    Catley, Kefyn M.; Novick, Laura R.; Shade, Courtney K.

    2010-01-01

    The authors argue that some diagrams in biology textbooks and the popular press presented as depicting evolutionary relationships suggest an inappropriate (anagenic) conception of evolutionary history. The goal of this research was to provide baseline data that begin to document how college students conceptualize the evolutionary relationships…

  18. A Formal Semantics for UML Activity Diagrams - Formalising Workflow Models

    NARCIS (Netherlands)

    Eshuis, H.; Wieringa, Roelf J.

    In this report we define a formal execution semantics for UML activity diagrams that is appropriate for workflow modelling. Our workflow models express software requirements and therefore assume a perfect implementation. In our semantics, software state changes do not take time. It is based upon the

  19. Introducing the Circular Flow Diagram to Business Students

    Science.gov (United States)

    Daraban, Bogdan

    2010-01-01

    The circular flow of income diagram is a simplified representation of the functioning of a free-market economic system. It illustrates how businesses interact with the other economic participants within the key macroeconomic markets that coordinate the flow of income through the national economy. Therefore, it can provide students of business with…

  20. A deductive view on process-data diagrams

    NARCIS (Netherlands)

    Jeusfeld, M.A.; Ralyte, J.; Mirbel, I.I.; Deneckere, R.

    2011-01-01

    Process-Data Diagrams (PDDs) are a popular technique to represent method fragments and their recombination to new adapted method specifications. It turns out that PDDs are at odds with a strict separation of MOF/MDA abstraction levels as advocated by MOF/MDA. We abandon the restriction and specify

  1. Phase diagram of compressively strained nickelate thin films

    Directory of Open Access Journals (Sweden)

    A. S. Disa

    2013-09-01

    Full Text Available The complex phase diagrams of strongly correlated oxides arise from the coupling between physical and electronic structure. This can lead to a renormalization of the phase boundaries when considering thin films rather than bulk crystals due to reduced dimensionality and epitaxial strain. The well-established bulk RNiO3 phase diagram shows a systematic dependence between the metal-insulator transition and the perovskite A-site rare-earth ion, R. Here, we explore the equivalent phase diagram for nickelate thin films under compressive epitaxial strain. We determine the metal-insulator phase diagram for the solid solution of Nd1-yLayNiO3 thin films within the range 0 ≤ y ≤ 1. We find qualitative similarity between the films and their bulk analogs, but with an overall renormalization in the metal-insulator transition to lower temperature. A combination of x-ray diffraction measurements and soft x-ray absorption spectroscopy indicates that the renormalization is due to increased Ni–O bond hybridization for coherently strained thin films.

  2. Stabilization diagrams using operationalmodal analysis and sliding filters

    DEFF Research Database (Denmark)

    Olsen, Peter; Juul, Martin O.; Tarpø, Marius

    2017-01-01

    This paper presents a filtering technique for doing effective operational modal analysis. The result of the filtering method is construction of stabilization diagram that clearly separates physical poles from spurious noise poles needed for unbiased fitting. A band pass filter is moved slowly ove...

  3. Stabilization diagrams using operational modal analysis and sliding filters

    DEFF Research Database (Denmark)

    Olsen, Peter; Juul, Martin Ørum Ørhem; Tarpø, Marius Glindtvad

    2017-01-01

    This paper presents a filtering technique for doing effective operational modal analysis. The result of the filtering method is construction of stabilization diagram that clearly separates physical poles from spurious noise poles needed for unbiased fitting. A band pass filter is moved slowly ove...

  4. Failure Assessment Diagram for Brazed 304 Stainless Steel Joints

    Science.gov (United States)

    Flom, Yory

    2011-01-01

    Interaction equations were proposed earlier to predict failure in Albemet 162 brazed joints. Present study demonstrates that the same interaction equations can be used for lower bound estimate of the failure criterion in 304 stainless steel joints brazed with silver-based filler metals as well as for construction of the Failure Assessment Diagrams (FAD).

  5. Diagrams for certain quotients of PSL(2,Z[i])

    Indian Academy of Sciences (India)

    types. A technique is developed to count the number of fragments which frequently occur in the diagrams for the action of the Picard group on PL(Fp). ..... a Pythagorean prime, are composed of various types of fragments. There are .... The code is developed in Mathematica software to generate the permutation group of the.

  6. The Effect of Diagrams on Online Reading Processes and Memory

    Science.gov (United States)

    McCrudden, Matthew T.; Magliano, Joseph P.; Schraw, Gregory

    2011-01-01

    This work examined how adjunct displays influence college readers' moment-by-moment processing of text and the products of reading, using reading time (Experiments 1 & 2), and think-aloud methodologies (Experiment 3). Participants did or did not study a diagram before reading a text. Overall, the reading time data, think-aloud data, and recall…

  7. Two-loop sunset diagrams with three massive lines

    Energy Technology Data Exchange (ETDEWEB)

    Kniehl, B.A. [II. Institut fuer Theoretische Physik, Universitaet Hamburg, 22761 Hamburg (Germany)]. E-mail: kniehl@desy.de; Kotikov, A.V. [II. Institut fuer Theoretische Physik, Universitaet Hamburg, 22761 Hamburg (Germany); Bogolyubov Laboratory for Theoretical Physics, JINR, 141980 Dubna, Moscow region (Russian Federation); Onishchenko, A.I. [II. Institut fuer Theoretische Physik, Universitaet Hamburg, 22761 Hamburg (Germany); Theoretical Physics Department, Petersburg Nuclear Physics Institute, Orlova Roscha, 188300 Gatchina (Russian Federation); Veretin, O.L. [II. Institut fuer Theoretische Physik, Universitaet Hamburg, 22761 Hamburg (Germany); Petrozavodsk State University, 185910 Petrozavodsk, Karelia (Russian Federation)

    2006-03-20

    In this paper, we consider the two-loop sunset diagram with two different masses, m and M, at spacelike virtuality q{sup 2}=-m{sup 2}. We find explicit representations for the master integrals and an analytic result through O(-bar ) in d=4-2-bar space-time dimensions for the case of equal masses, m=M.

  8. Stability field diagrams for Ln–O–Cl systems

    Indian Academy of Sciences (India)

    −Cl system at constant temperature indicates that the system is invariant when three condensed phases coexist with a gas phase. Hence, partial pressures of oxygen and chlorine are uniquely defined. Isothermal stability field diagram is a plot ...

  9. Phase Stability Diagrams for High Temperature Corrosion Processes

    Directory of Open Access Journals (Sweden)

    J. J. Ramos-Hernandez

    2013-01-01

    Full Text Available Corrosion phenomena of metals by fused salts depend on chemical composition of the melt and environmental conditions of the system. Detail knowledge of chemistry and thermodynamic of aggressive species formed during the corrosion process is essential for a better understanding of materials degradation exposed to high temperature. When there is a lack of kinetic data for the corrosion processes, an alternative to understand the thermodynamic behavior of chemical species is to utilize phase stability diagrams. Nowadays, there are several specialized software programs to calculate phase stability diagrams. These programs are based on thermodynamics of chemical reactions. Using a thermodynamic data base allows the calculation of different types of phase diagrams. However, sometimes it is difficult to have access to such data bases. In this work, an alternative way to calculate phase stability diagrams is presented. The work is exemplified in the Na-V-S-O and Al-Na-V-S-O systems. This system was chosen because vanadium salts is one of the more aggressive system for all engineering alloys, especially in those processes where fossil fuels are used.

  10. Generalized balanced power diagrams for 3D representations of polycrystals

    DEFF Research Database (Denmark)

    Alpers, Andreas; Brieden, Andreas; Gritzmann, Peter

    2015-01-01

    Characterizing the grain structure of polycrystalline material is an important task in material science. The present paper introduces the concept of generalized balanced power diagrams as a concise alternative to voxelated mappings. Here, each grain is represented by (measured approximations of...... governing the forming of such polycrystals in the underlying process quite well....

  11. Kinematical Diagrams for Conical Relativistic Jets Gopal-Krishna ...

    Indian Academy of Sciences (India)

    2007-02-28

    Feb 28, 2007 ... Kinematical Diagrams for Conical Relativistic Jets. Gopal-Krishna. 1. , Pronoy Sircar. 2. & Samir Dhurde. 3. 1National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune. University Campus, Post Bag No. 3, Pune 411 007, India. e-mail: krishna@ncra.tifr.res.in. 2Department of ...

  12. Phase diagrams for geoscientists an atlas of the Earth's interior

    CERN Document Server

    Gasparik, Tibor

    2014-01-01

    Presented in this new, full-color edition, with the first polychrome phase diagrams to be published, this geoscientific atlas is backed by the author's unrivalled dataset, and amounts to the most complete survey yet of phase relations in Earth's chemistry.

  13. Software Tool Integrating Data Flow Diagrams and Petri Nets

    Science.gov (United States)

    Thronesbery, Carroll; Tavana, Madjid

    2010-01-01

    Data Flow Diagram - Petri Net (DFPN) is a software tool for analyzing other software to be developed. The full name of this program reflects its design, which combines the benefit of data-flow diagrams (which are typically favored by software analysts) with the power and precision of Petri-net models, without requiring specialized Petri-net training. (A Petri net is a particular type of directed graph, a description of which would exceed the scope of this article.) DFPN assists a software analyst in drawing and specifying a data-flow diagram, then translates the diagram into a Petri net, then enables graphical tracing of execution paths through the Petri net for verification, by the end user, of the properties of the software to be developed. In comparison with prior means of verifying the properties of software to be developed, DFPN makes verification by the end user more nearly certain, thereby making it easier to identify and correct misconceptions earlier in the development process, when correction is less expensive. After the verification by the end user, DFPN generates a printable system specification in the form of descriptions of processes and data.

  14. Enteric pathogens: use of flow diagrams for identification.

    Science.gov (United States)

    Pezzlo, M; Valter, P J

    1977-07-01

    A protocol is presented for the cultural processing of stool specimens. Flow diagrams were developed which allow all stool cultures to be processed in a consistent and efficient manner. Criteria have been established to indicate when definitive identification and antimicrobial susceptibility testing are required. A review of the food-poisoning syndrome and infective gastrointestinal disease due to bacterial agents is included.

  15. From objects to diagrams for ranges of functors

    CERN Document Server

    Gillibert, Pierre

    2011-01-01

    This work introduces tools from the field of category theory that make it possible to tackle a number of representation problems that have remained unsolvable to date (e.g. the determination of the range of a given functor). The basic idea is: if a functor lifts many objects, then it also lifts many (poset-indexed) diagrams.

  16. Investigating the QCD phase diagram with hadron multiplicities at NICA

    Energy Technology Data Exchange (ETDEWEB)

    Becattini, F. [Universita di Firenze (Italy); INFN, Firenze (Italy); Stock, R. [Goethe University, Frankfurt am Main (Germany)

    2016-08-15

    We discuss the potential of the experimental programme at NICA to investigate the QCD phase diagram and particularly the position of the critical line at large baryon-chemical potential with accurate measurements of particle multiplicities. We briefly review the present status and we outline the tasks to be accomplished both theoretically and the experimentally to make hadronic abundances a sensitive probe. (orig.)

  17. Very Low-mass Stars and Brown Dwarfs in Upper Scorpius Using Gaia DR1: Mass Function, Disks, and Kinematics

    Science.gov (United States)

    Cook, Neil J.; Scholz, Aleks; Jayawardhana, Ray

    2017-12-01

    Our understanding of the brown dwarf population in star-forming regions is dependent on knowing distances and proper motions and therefore will be improved through the Gaia space mission. In this paper, we select new samples of very low-mass objects (VLMOs) in Upper Scorpius using UKIDSS colors and optimized proper motions calculated using Gaia DR1. The scatter in proper motions from VLMOs in Upper Scorpius is now (for the first time) dominated by the kinematic spread of the region itself, not by the positional uncertainties. With age and mass estimates updated using Gaia parallaxes for early-type stars in the same region, we determine masses for all VLMOs. Our final most complete sample includes 453 VLMOs of which ˜125 are expected to be brown dwarfs. The cleanest sample is comprised of 131 VLMOs, with ˜105 brown dwarfs. We also compile a joint sample from the literature that includes 415 VLMOs, out of which 152 are likely brown dwarfs. The disk fraction among low-mass brown dwarfs (M< 0.05 {M}⊙ ) is substantially higher than in more massive objects, indicating that disks around low-mass brown dwarfs survive longer than in low-mass stars overall. The mass function for 0.01< M< 0.1 {M}⊙ is consistent with the Kroupa Initial Mass Function. We investigate the possibility that some “proper motion outliers” have undergone a dynamical ejection early in their evolution. Our analysis shows that the color-magnitude cuts used when selecting samples introduce strong bias into the population statistics due to varying levels of contamination and completeness.

  18. About the new B- and A-type periodic variable stars

    Science.gov (United States)

    Mowlavi, Nami; Saesen, Sophie; Barblan, Fabio; Semaan, Thierry; Eyer, Laurent

    2015-08-01

    New periodic variable stars of type B and A were discovered in 2013 in the open cluster NGC 3766 (Mowlavi et al. 2013), in a region of the Hertzsprung-Rusell diagram on the main sequence, between delta-Scuti and Slowly Pulsating B stars, where no periodic star was expected to be found. The observational properties of the potentially new class of variability challenged model predictions of pulsating stars that were available at the time of their discovery, and triggered new theoretical developments in the field.Meanwhile, we obtained additional observational elements that shed new light on these new periodic variable stars. First, we analyzed photometric data of three other young clusters with ages between about 15 to about 70 million years, for which we had up to seven years of observations. The analysis reveals the presence of the new periodic B- and A-type stars in those clusters as well, with properties similar to those found in NGC 3766, but with also new features. Second, we took spectra of all new periodic variables found in NGC 3766, using Giraffe multi-fiber spectrometer mounted on the VLT. Those data enable a better characterization of the nature of those stars.We present in this contribution the results of those two new studies, and their impacts on our understanding of the new periodic stars.

  19. Non-LTE analysis of extremely helium-rich stars. The hot sdO stars LSE 153, 259 and 263

    Science.gov (United States)

    Husfeld, D.; Butler, K.; Heber, U.; Drilling, J. S.

    1989-01-01

    Results of a non-LTE fine analysis based mainly on high-resolution CASPEC spectra for three extremely helium-rich sdO stars are discussed in order to explain hydrogen deficiency in single stars. High temperature (Teff = 70,000 to 75,000 K) and a position in the log Teff - log g diagram were found close to the Eddington limit. Various abundance estimates are derived for hydrogen (upper limits only), carbon, nitrogen, and magnesium. Hydrogen is reduced to less than 10 percent by number in LSE 153 and LSE 263, and to less than 5 percent in LSE 259. The hydrogen deficiency is accompanied by nitrogen- and carbon-enrichment in LSE 153 and LSE 259 only. In LSE 263, carbon is depleted by about 1 dex. Stellar masses obtained by assuming that a core mass-luminosity relation holds for these stars, were found to be in the range 0.6-0.9 solar mass, yielding luminosities log L/L:solar = 3.7-4.5. Two of the program stars (LSE 153 and 259) appear to be possible successors of the R CrB and helium B stars, whereas the third star (LSE 263) displays a much lower carbon content in its photosphere making it an exceptional case among the known hydrogen deficient stars.

  20. Amplitude modulation in δ Sct stars: statistics from an ensemble of Kepler targets

    Directory of Open Access Journals (Sweden)

    Bowman Dominic M.

    2017-01-01

    Full Text Available The results of a search for amplitude modulation of pulsation modes in 983 δ Sct stars, which have effective temperatures between 6400 ⩽ Teff ⩽ 10 000 K in the Kepler Input Catalogue and were continuously observed by the Kepler Space Telescope for 4 yr, are presented. A total of 603 δ Sct stars (61.3 per cent are found to exhibit at least one pulsation mode that varies significantly in amplitude over 4 yr. Furthermore, it is found that amplitude modulation is not restricted to a specific region within the classical instability strip in the HR diagram, therefore its cause is not necessarily dependent on stellar parameters such as Teff or log g. On the other hand, many δ Sct stars show constant pulsation amplitudes demonstrating that the cause of pulsational non-linearity in these stars is not well understood.

  1. Super Star Clusters

    Science.gov (United States)

    O'Connell, R. W.

    1994-05-01

    Super star clusters represent an extreme in the star formation process. They are very luminous, compact objects with L_V > 10(6) L_{V,sun} and diameters = 100 times higher than normal OB associations and clusters in ``giant H II regions''. Prior to HST about a dozen such objects had been identified in nearby galaxies, but at ground-based resolution they are nearly point sources. We review recent HST observations of individual super star clusters in NGC 1140, 1569, and 1705. They have half-light radii of only 2--3.5 pc, and some show evidence of substructure which should be resolvable with the repaired HST. After allowing for age differences, the surface brightness of NGC 1569-A is over 65 times higher than the core of 30 Doradus in the LMC and 1200 times higher than the mean rich LMC star cluster. In some cases, the energy released by the clusters into their surroundings is sufficient to drive galaxy-wide winds. Their properties make super star clusters good analogues of young globular clusters. In some, though not all, cases super star clusters appear to form in the aftermath of a merger or accretion event. The most impressive examples are the clusters detected by HST in NGC 1275 and 7252, one of which has the extraordinary luminosity ~ 6 times 10(8) L_{V,sun}. M82 affords a nearby view of a post-interaction system. HST imaging has identified over 80 super star clusters in its central regions with mean luminosities of ~ 3 times 10(6) L_{V,sun}. Their close packing and signs of interaction with the well-known supernova-driven wind suggest that they do not evolve independently. Super cluster evolution in starbursts is probably a collective phenomenon.

  2. Metal-Rich SX Phe Stars in the Kepler Field

    Directory of Open Access Journals (Sweden)

    Nemec James M.

    2015-01-01

    Full Text Available High-resolution spectroscopic observations have been made for 32 of the 34 candidate SX Phe stars identified in the Kepler field by Balona & Nemec (2012. All available long-and short-cadence Q0-Q17 Kepler photometry has been analyzed for the 34 candidates. Radial velocities (RVs, space motions (U, V, W, projected rotation velocities (υ sin i, spectral types, and atmospheric characteristics (Teff, log g, [M/H], υmic, etc. were derived from ~ 160 spectra taken with the ESPaDOnS spectrograph on the Canada-France-Hawaii 3.6-m telescope and with the ARCES spectrograph on the Apache Point Observatory 3.5-m telescope. Two thirds of the stars are fast rotators with υ sin i > 50 km/s, including four stars with υ sin i > 200 km/s. Three of the stars have (negative RVs > 250 km/s and retrograde space motions, and seven stars have total space motions > 400 km/s. All the spectroscopically measured SX Phe candidates have positions in a Toomre diagram that are consistent with being bona fide halo and thick-disk stars. Although several stars show a marked metal weakness, the mean [Fe/H] of the sample is near 0.0 dex (σ ~ 0.25 dex, which is considerably more metal-rich than is normally expected for a sample of Pop. II stars. Observed pulsation frequency modulations and optical time delays suggest that at least eight of the SX Phe stars are in binary systems, some of which show significant RV variations. Six of the time-delay binaries have secondary masses ranging from 0.05 to 0.70 M☉ and orbital periods in the range 9 to 1570 days. Another star appears to be an ellipsoidal variable with a 2.3-day orbital period; and two other systems have orbital periods longer than the ~ 4-year sampling interval of the Kepler data.

  3. Collaborative diagramming during problem based learning in medical education: Do computerized diagrams support basic science knowledge construction?

    NARCIS (Netherlands)

    de Leng, Bas; Gijlers, Aaltje H.

    2015-01-01

    Aim: To examine how collaborative diagramming affects discussion and knowledge construction when learning complex basic science topics in medical education, including its effectiveness in the reformulation phase of problem-based learning. Methods: Opinions and perceptions of students (n = 70) and

  4. Near-infrared variability study of the central 2.3 × 2.3 arcmin2 of the Galactic Centre - II. Identification of RR Lyrae stars in the Milky Way nuclear star cluster

    Science.gov (United States)

    Dong, Hui; Schödel, Rainer; Williams, Benjamin F.; Nogueras-Lara, Francisco; Gallego-Cano, Eulalia; Gallego-Calvente, Teresa; Wang, Q. Daniel; Rich, R. Michael; Morris, Mark R.; Do, Tuan; Ghez, Andrea

    2017-11-01

    Because of strong and spatially highly variable interstellar extinction and extreme source crowding, the faint (K ≥ 15) stellar population in the Milky Way's nuclear star cluster is still poorly studied. RR Lyrae stars provide us with a tool to estimate the mass of the oldest, relative dim stellar population. Recently, we analysed HST/WFC3/IR observations of the central 2.3 × 2.3 arcmin2 of the Milky Way and found 21 variable stars with periods between 0.2 and 1 d. Here, we present a further comprehensive analysis of these stars. The period-luminosity relationship of RR Lyrae is used to derive their extinctions and distances. Using multiple approaches, we classify our sample as 4 RRc stars, 4 RRab stars, 3 RRab candidates and 10 binaries. Especially, the four RRab stars show sawtooth light curves and fall exactly on to the Oosterhoff I division in the Bailey diagram. Compared to the RRab stars reported by Minniti et al., our new RRab stars have higher extinction (AK > 1.8) and should be closer to the Galactic Centre. The extinction and distance of one RRab stars match those for the Milky Way's nuclear star cluster given in previous works. We perform simulations and find that after correcting for incompleteness, there could be not more than 40 RRab stars within the Milky Way's nuclear star cluster and in our field of view. Through comparing with the known globular clusters of the Milky Way, we estimate that if there exists an old, metal-poor (-1.5 nuclear star cluster on a scale of 5 × 5 pc, then it contributes at most 4.7 × 105 M⊙, i.e. ˜18 per cent of the stellar mass.

  5. Circulation of Stars

    Science.gov (United States)

    Boitani, P.

    2016-01-01

    Since the dawn of man, contemplation of the stars has been a primary impulse in human beings, who proliferated their knowledge of the stars all over the world. Aristotle sees this as the product of primeval and perennial “wonder” which gives rise to what we call science, philosophy, and poetry. Astronomy, astrology, and star art (painting, architecture, literature, and music) go hand in hand through millennia in all cultures of the planet (and all use catasterisms to explain certain phenomena). Some of these developments are independent of each other, i.e., they take place in one culture independently of others. Some, on the other hand, are the product of the “circulation of stars.” There are two ways of looking at this. One seeks out forms, the other concentrates on the passing of specific lore from one area to another through time. The former relies on archetypes (for instance, with catasterism), the latter constitutes a historical process. In this paper I present some of the surprising ways in which the circulation of stars has occurred—from East to West, from East to the Far East, and from West to East, at times simultaneously.

  6. Investigation of faint galactic carbon stars from the first Byurakan spectral survey. III. Infrared characteristics

    OpenAIRE

    Gigoyan, K. S.; A. Sarkissian; Rossi, C.; Russeil, D.,; Kostandyan, G.; Calabresi, M.; Zamkotsian, F.; Meftah, M.

    2017-01-01

    Infra-Red(IR) astronomical databases, namely, IRAS, 2MASS, WISE, and Spitzer, are used to analyze photometric data of 126 carbon stars whose spectra are visible in the First Byurakan Survey low-resolution spectral plates. Among these, six new objects, recently confirmed on the digitized FBS plates, are included. For three of them, moderate-resolution CCD optical spectra are also presented. In this work several IR color-color diagrams are studied. Early and late-type C stars are separated in t...

  7. The Populations of Carina. I. Decoding the Color–Magnitude Diagram

    Energy Technology Data Exchange (ETDEWEB)

    Norris, John E.; Yong, David; Dotter, Aaron; Casagrande, Luca [Research School of Astronomy and Astrophysics, The Australian National University, Canberra, ACT 2611 (Australia); Venn, Kim A. [Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 1A1 (Canada); Gilmore, Gerard, E-mail: jen@mso.anu.edu.au, E-mail: yong@mso.anu.edu.au, E-mail: aaron.dotter@gmail.com, E-mail: luca@mso.anu.edu.au, E-mail: kvenn@uvic.ca, E-mail: gil@ast.cam.ac.uk [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)

    2017-06-01

    We investigate the color–magnitude diagram (CMD) of the Carina dwarf spheroidal galaxy using data of Stetson et al. and synthetic CMDs based on isochrones of Dotter et al., in terms of the parameters [Fe/H], age, and [ α /Fe], for the cases when (i) [ α /Fe] is held constant and (ii) [ α /Fe] is varied. The data are well described by four basic epochs of star formation, having [Fe/H] = −1.85, −1.5, −1.2, and ∼−1.15 and ages ∼13, 7, ∼3.5, and ∼1.5 Gyr, respectively (for [ α /Fe] = 0.1, constant [ α /Fe], and [ α /Fe] = 0.2, 0.1, −0.2, −0.2, variable [ α /Fe]), with small spreads in [Fe/H] and age of order 0.1 dex and 1–3 Gyr. Within an elliptical radius 13.′1, the mass fractions of the populations, at their times of formation, were (in decreasing age order) 0.34, 0.39, 0.23, and 0.04. This formalism reproduces five observed CMD features (two distinct subgiant branches of old and intermediate-age populations, two younger, main-sequence components, and the small color dispersion on the red giant branch (RGB). The parameters of the youngest population are less certain than those of the others, and given it is less centrally concentrated, it may not be directly related to them. High-resolution spectroscopically analyzed RGB samples appear statistically incomplete compared with those selected using radial velocity, which contain bluer stars comprising ∼5%–10% of the samples. We conjecture these objects may, at least in part, be members of the youngest population. We use the CMD simulations to obtain insight into the population structure of Carina's upper RGB.

  8. Stars a very short introduction

    CERN Document Server

    King, Andrew

    2012-01-01

    Stars: A Very Short Introduction looks at how stars live, producing all the chemical elements beyond helium, and how they die, leaving remnants such as black holes. Every atom of our bodies has been part of a star. Our very own star, the Sun, is crucial to the development and sustainability of life on Earth. Understanding stars is key to understanding the galaxies they inhabit, the existence of planets, and the history of our entire Universe. This VSI explores the science of stars, the mechanisms that allow them to form, the processes that allow them to shine, and the results of their death.

  9. Lithium in LMC carbon stars

    OpenAIRE

    Hatzidimitriou, D.; Morgan, D. H.; Cannon, R. D.; Croke, B. F. W.

    2003-01-01

    Nineteen carbon stars that show lithium enrichment in their atmospheres have been discovered among a sample of 674 carbon stars in the Large Magellanic Cloud. Six of the Li-rich carbon stars are of J-type, i.e. with strong 13C isotopic features. No super-Li-rich carbon stars were found. The incidence of lithium enrichment among carbon stars in the LMC is much rarer than in the Galaxy, and about five times more frequent among J-type than among N-type carbon stars. The bolometric magnitudes of ...

  10. An Undergraduate Research Experience on Studying Variable Stars

    Science.gov (United States)

    Amaral, A.; Percy, J. R.

    2016-06-01

    We describe and evaluate a summer undergraduate research project and experience by one of us (AA), under the supervision of the other (JP). The aim of the project was to sample current approaches to analyzing variable star data, and topics related to the study of Mira variable stars and their astrophysical importance. This project was done through the Summer Undergraduate Research Program (SURP) in astronomy at the University of Toronto. SURP allowed undergraduate students to explore and learn about many topics within astronomy and astrophysics, from instrumentation to cosmology. SURP introduced students to key skills which are essential for students hoping to pursue graduate studies in any scientific field. Variable stars proved to be an excellent topic for a research project. For beginners to independent research, it introduces key concepts in research such as critical thinking and problem solving, while illuminating previously learned topics in stellar physics. The focus of this summer project was to compare observations with structural and evolutionary models, including modelling the random walk behavior exhibited in the (O-C) diagrams of most Mira stars. We found that the random walk could be modelled by using random fluctuations of the period. This explanation agreed well with observations.

  11. Giant star seismology

    Science.gov (United States)

    Hekker, S.; Christensen-Dalsgaard, J.

    2017-06-01

    The internal properties of stars in the red-giant phase undergo significant changes on relatively short timescales. Long near-uninterrupted high-precision photometric timeseries observations from dedicated space missions such as CoRoT and Kepler have provided seismic inferences of the global and internal properties of a large number of evolved stars, including red giants. These inferences are confronted with predictions from theoretical models to improve our understanding of stellar structure and evolution. Our knowledge and understanding of red giants have indeed increased tremendously using these seismic inferences, and we anticipate that more information is still hidden in the data. Unraveling this will further improve our understanding of stellar evolution. This will also have significant impact on our knowledge of the Milky Way Galaxy as well as on exo-planet host stars. The latter is important for our understanding of the formation and structure of planetary systems.

  12. Dynamical Boson Stars

    Directory of Open Access Journals (Sweden)

    Steven L. Liebling

    2012-05-01

    Full Text Available The idea of stable, localized bundles of energy has strong appeal as a model for particles. In the 1950s, John Wheeler envisioned such bundles as smooth configurations of electromagnetic energy that he called geons, but none were found. Instead, particle-like solutions were found in the late 1960s with the addition of a scalar field, and these were given the name boson stars. Since then, boson stars find use in a wide variety of models as sources of dark matter, as black hole mimickers, in simple models of binary systems, and as a tool in finding black holes in higher dimensions with only a single Killing vector. We discuss important varieties of boson stars, their dynamic properties, and some of their uses, concentrating on recent efforts.

  13. Collapse of axion stars

    Energy Technology Data Exchange (ETDEWEB)

    Eby, Joshua [Department of Physics, University of Cincinnati,2600 Clifton Ave, Cincinnati, OH, 45221 (United States); Fermi National Accelerator Laboratory,P.O. Box 500, Batavia, IL, 60510 (United States); Leembruggen, Madelyn; Suranyi, Peter; Wijewardhana, L.C.R. [Department of Physics, University of Cincinnati,2600 Clifton Ave, Cincinnati, OH, 45221 (United States)

    2016-12-15

    Axion stars, gravitationally bound states of low-energy axion particles, have a maximum mass allowed by gravitational stability. Weakly bound states obtaining this maximum mass have sufficiently large radii such that they are dilute, and as a result, they are well described by a leading-order expansion of the axion potential. Heavier states are susceptible to gravitational collapse. Inclusion of higher-order interactions, present in the full potential, can give qualitatively different results in the analysis of collapsing heavy states, as compared to the leading-order expansion. In this work, we find that collapsing axion stars are stabilized by repulsive interactions present in the full potential, providing evidence that such objects do not form black holes. In the last moments of collapse, the binding energy of the axion star grows rapidly, and we provide evidence that a large amount of its energy is lost through rapid emission of relativistic axions.

  14. Dynamical boson stars

    Science.gov (United States)

    Liebling, Steven L.; Palenzuela, Carlos

    2017-11-01

    The idea of stable, localized bundles of energy has strong appeal as a model for particles. In the 1950s, John Wheeler envisioned such bundles as smooth configurations of electromagnetic energy that he called geons, but none were found. Instead, particle-like solutions were found in the late 1960s with the addition of a scalar field, and these were given the name boson stars. Since then, boson stars find use in a wide variety of models as sources of dark matter, as black hole mimickers, in simple models of binary systems, and as a tool in finding black holes in higher dimensions with only a single Killing vector. We discuss important varieties of boson stars, their dynamic properties, and some of their uses, concentrating on recent efforts.

  15. Heavy Metal Stars

    Science.gov (United States)

    2001-08-01

    La Silla Telescope Detects Lots of Lead in Three Distant Binaries Summary Very high abundances of the heavy element Lead have been discovered in three distant stars in the Milky Way Galaxy . This finding strongly supports the long-held view that roughly half of the stable elements heavier than Iron are produced in common stars during a phase towards the end of their life when they burn their Helium - the other half results from supernova explosions. All the Lead contained in each of the three stars weighs about as much as our Moon. The observations show that these "Lead stars" - all members of binary stellar systems - have been more enriched with Lead than with any other chemical element heavier than Iron. This new result is in excellent agreement with predictions by current stellar models about the build-up of heavy elements in stellar interiors. The new observations are reported by a team of Belgian and French astronomers [1] who used the Coude Echelle Spectrometer on the ESO 3.6-m telescope at the La Silla Observatory (Chile). PR Photo 26a/01 : A photo of HD 196944 , one of the "Lead stars". PR Photo 26b/01 : A CES spectrum of HD 196944 . The build-up of heavy elements Astronomers and physicists denote the build-up of heavier elements from lighter ones as " nucleosynthesis ". Only the very lightest elements (Hydrogen, Helium and Lithium [2]) were created at the time of the Big Bang and therefore present in the early universe. All the other heavier elements we now see around us were produced at a later time by nucleosynthesis inside stars. In those "element factories", nuclei of the lighter elements are smashed together whereby they become the nuclei of heavier ones - this process is known as nuclear fusion . In our Sun and similar stars, Hydrogen is being fused into Helium. At some stage, Helium is fused into Carbon, then Oxygen, etc. The fusion process requires positively charged nuclei to move very close to each other before they can unite. But with increasing

  16. Dynamical boson stars.

    Science.gov (United States)

    Liebling, Steven L; Palenzuela, Carlos

    2017-01-01

    The idea of stable, localized bundles of energy has strong appeal as a model for particles. In the 1950s, John Wheeler envisioned such bundles as smooth configurations of electromagnetic energy that he called geons, but none were found. Instead, particle-like solutions were found in the late 1960s with the addition of a scalar field, and these were given the name boson stars. Since then, boson stars find use in a wide variety of models as sources of dark matter, as black hole mimickers, in simple models of binary systems, and as a tool in finding black holes in higher dimensions with only a single Killing vector. We discuss important varieties of boson stars, their dynamic properties, and some of their uses, concentrating on recent efforts.

  17. Atomic diffusion in stars

    CERN Document Server

    Michaud, Georges; Richer, Jacques

    2015-01-01

    This book gives an overview of atomic diffusion, a fundamental physical process, as applied to all types of stars, from the main sequence to neutron stars. The superficial abundances of stars as well as their evolution can be significantly affected. The authors show where atomic diffusion plays an essential role and how it can be implemented in modelling.  In Part I, the authors describe the tools that are required to include atomic diffusion in models of stellar interiors and atmospheres. An important role is played by the gradient of partial radiative pressure, or radiative acceleration, which is usually neglected in stellar evolution. In Part II, the authors systematically review the contribution of atomic diffusion to each evolutionary step. The dominant effects of atomic diffusion are accompanied by more subtle effects on a large number of structural properties throughout evolution. One of the goals of this book is to provide the means for the astrophysicist or graduate student to evaluate the importanc...

  18. Pulsating Star Mystery Solved

    Science.gov (United States)

    2010-11-01

    By discovering the first double star where a pulsating Cepheid variable and another star pass in front of one another, an international team of astronomers has solved a decades-old mystery. The rare alignment of the orbits of the two stars in the double star system has allowed a measurement of the Cepheid mass with unprecedented accuracy. Up to now astronomers had two incompatible theoretical predictions of Cepheid masses. The new result shows that the prediction from stellar pulsation theory is spot on, while the prediction from stellar evolution theory is at odds with the new observations. The new results, from a team led by Grzegorz Pietrzyński (Universidad de Concepción, Chile, Obserwatorium Astronomiczne Uniwersytetu Warszawskiego, Poland), appear in the 25 November 2010 edition of the journal Nature. Grzegorz Pietrzyński introduces this remarkable result: "By using the HARPS instrument on the 3.6-metre telescope at ESO's La Silla Observatory in Chile, along with other telescopes, we have measured the mass of a Cepheid with an accuracy far greater than any earlier estimates. This new result allows us to immediately see which of the two competing theories predicting the masses of Cepheids is correct." Classical Cepheid Variables, usually called just Cepheids, are unstable stars that are larger and much brighter than the Sun [1]. They expand and contract in a regular way, taking anything from a few days to months to complete the cycle. The time taken to brighten and grow fainter again is longer for stars that are more luminous and shorter for the dimmer ones. This remarkably precise relationship makes the study of Cepheids one of the most effective ways to measure the distances to nearby galaxies and from there to map out the scale of the whole Universe [2]. Unfortunately, despite their importance, Cepheids are not fully understood. Predictions of their masses derived from the theory of pulsating stars are 20-30% less than predictions from the theory of the

  19. Really Hot Stars

    Science.gov (United States)

    2003-04-01

    Spectacular VLT Photos Unveil Mysterious Nebulae Summary Quite a few of the most beautiful objects in the Universe are still shrouded in mystery. Even though most of the nebulae of gas and dust in our vicinity are now rather well understood, there are some which continue to puzzle astronomers. This is the case of a small number of unusual nebulae that appear to be the subject of strong heating - in astronomical terminology, they present an amazingly "high degree of excitation". This is because they contain significant amounts of ions, i.e., atoms that have lost one or more of their electrons. Depending on the atoms involved and the number of electrons lost, this process bears witness to the strength of the radiation or to the impact of energetic particles. But what are the sources of that excitation? Could it be energetic stars or perhaps some kind of exotic objects inside these nebulae? How do these peculiar objects fit into the current picture of universal evolution? New observations of a number of such unusual nebulae have recently been obtained with the Very Large Telescope (VLT) at the ESO Paranal Observatory (Chile). In a dedicated search for the origin of their individual characteristics, a team of astronomers - mostly from the Institute of Astrophysics & Geophysics in Liège (Belgium) [1] - have secured the first detailed, highly revealing images of four highly ionized nebulae in the Magellanic Clouds, two small satellite galaxies of our home galaxy, the Milky Way, only a few hundred thousand light-years away. In three nebulae, they succeeded in identifying the sources of energetic radiation and to eludicate their exceptional properties: some of the hottest, most massive stars ever seen, some of which are double. With masses of more than 20 times that of the Sun and surface temperatures above 90 000 degrees, these stars are truly extreme. PR Photo 09a/03: Nebula around the hot star AB7 in the SMC. PR Photo 09b/03: Nebula near the hot Wolf-Rayet star BAT99

  20. General Relativity&Compact Stars

    Energy Technology Data Exchange (ETDEWEB)

    Glendenning, Norman K.

    2005-08-16

    Compact stars--broadly grouped as neutron stars and white dwarfs--are the ashes of luminous stars. One or the other is the fate that awaits the cores of most stars after a lifetime of tens to thousands of millions of years. Whichever of these objects is formed at the end of the life of a particular luminous star, the compact object will live in many respects unchanged from the state in which it was formed. Neutron stars themselves can take several forms--hyperon, hybrid, or strange quark star. Likewise white dwarfs take different forms though only in the dominant nuclear species. A black hole is probably the fate of the most massive stars, an inaccessible region of spacetime into which the entire star, ashes and all, falls at the end of the luminous phase. Neutron stars are the smallest, densest stars known. Like all stars, neutron stars rotate--some as many as a few hundred times a second. A star rotating at such a rate will experience an enormous centrifugal force that must be balanced by gravity or else it will be ripped apart. The balance of the two forces informs us of the lower limit on the stellar density. Neutron stars are 10{sup 14} times denser than Earth. Some neutron stars are in binary orbit with a companion. Application of orbital mechanics allows an assessment of masses in some cases. The mass of a neutron star is typically 1.5 solar masses. They can therefore infer their radii: about ten kilometers. Into such a small object, the entire mass of our sun and more, is compressed.

  1. Searching for new young stars in the Northern hemisphere: the Pisces moving group

    Science.gov (United States)

    Binks, A. S.; Jeffries, R. D.; Ward, J. L.

    2018-01-01

    Using the kinematically unbiased technique described in Binks, Jeffries & Maxted (2015), we present optical spectra for a further 122 rapidly rotating (rotation periods rich G- and K-type stars that have a dispersion of only ∼3 km s-1 in each Galactic space velocity coordinate. The group members are approximately coeval in the colour-magnitude diagram, with an age of 30-50 Myr, and have similar, though not identical, kinematics to the Octans-Near MG.

  2. A Real Shooting Star

    Science.gov (United States)

    2007-01-01

    [figure removed for brevity, see original site] Click on the image for movie of A Real Shooting Star This artist's animation illustrates a star flying through our galaxy at supersonic speeds, leaving a 13-light-year-long trail of glowing material in its wake. The star, named Mira (pronounced my-rah) after the latin word for 'wonderful,' sheds material that will be recycled into new stars, planets and possibly even life. NASA's Galaxy Evolution Explorer discovered the long trail of material behind Mira during its survey of the entire sky in ultraviolet light. The animation begins by showing a close-up of Mira -- a red-giant star near the end of its life. Red giants are red in color and extremely bloated; for example, if a red giant were to replace our sun, it would engulf everything out to the orbit of Mars. They constantly blow off gas and dust in the form of stellar winds, supplying the galaxy with molecules, such as oxygen and carbon, that will make their way into new solar systems. Our sun will mature into a red giant in about 5 billion years. As the animation pulls out, we can see the enormous trail of material deposited behind Mira as it hurls along between the stars. Like a boat traveling through water, a bow shock, or build up of gas, forms ahead of the star in the direction of its motion. Gas in the bow shock is heated and then mixes with the cool hydrogen gas in the wind that is blowing off Mira. This heated hydrogen gas then flows around behind the star, forming a turbulent wake. Why does the trailing hydrogen gas glow in ultraviolet light? When it is heated, it transitions into a higher-energy state, which then loses energy by emitting ultraviolet light - a process known as fluorescence. Finally, the artist's rendering gives way to the actual ultraviolet image taken by the Galaxy Evolution Explorer Mira is located 350 light-years from Earth in the constellation Cetus, otherwise known as the whale. Coincidentally, Mira and its 'whale of a tail' can be

  3. Superfluidity in neutron stars

    Energy Technology Data Exchange (ETDEWEB)

    Shaham, J.

    1980-01-01

    The possible role played by superfluid neutrons in the dynamics of neutron stars is discussed, with attention given to vortex structure and dynamics, the modes of the free vortex lattice, and the pinning of crustal vortices. Some effects associated with the interior superfluid state of neutron stars are discussed, including (1) the macroscopic post-glitch time scales, resulting from coupling between normal and superfluid components, (2) glitches due to unpinning events or to crust breaking by pinning vortices, (3) possible long-term modulation in rotation period, resulting from vortex coherent modes, and (4) gyroscopic effects of pinned vorticity.

  4. Synthetic guide star generation

    Science.gov (United States)

    Payne, Stephen A [Castro Valley, CA; Page, Ralph H [Castro Valley, CA; Ebbers, Christopher A [Livermore, CA; Beach, Raymond J [Livermore, CA

    2008-06-10

    A system for assisting in observing a celestial object and providing synthetic guide star generation. A lasing system provides radiation at a frequency at or near 938 nm and radiation at a frequency at or near 1583 nm. The lasing system includes a fiber laser operating between 880 nm and 960 nm and a fiber laser operating between 1524 nm and 1650 nm. A frequency-conversion system mixes the radiation and generates light at a frequency at or near 589 nm. A system directs the light at a frequency at or near 589 nm toward the celestial object and provides synthetic guide star generation.

  5. Compact boson stars

    Energy Technology Data Exchange (ETDEWEB)

    Hartmann, Betti [School of Engineering and Science, Jacobs University, Postfach 750 561, D-28725 Bremen (Germany); Kleihaus, Burkhard; Kunz, Jutta [Institut fuer Physik, Universitaet Oldenburg, Postfach 2503, D-26111 Oldenburg (Germany); Schaffer, Isabell, E-mail: i.schaffer@jacobs-university.de [School of Engineering and Science, Jacobs University, Postfach 750 561, D-28725 Bremen (Germany)

    2012-07-24

    We consider compact boson stars that arise for a V-shaped scalar field potential. They represent a one parameter family of solutions of the scaled Einstein-Gordon equations. We analyze the physical properties of these solutions and determine their domain of existence. Along their physically relevant branch emerging from the compact Q-ball solution, their mass increases with increasing radius. Employing arguments from catastrophe theory we argue that this branch is stable, until the maximal value of the mass is reached. There the mass and size are on the order of magnitude of the Schwarzschild limit, and thus the spiraling respectively oscillating behaviour, well known for compact stars, sets in.

  6. The Drifting Star

    Science.gov (United States)

    2008-04-01

    By studying in great detail the 'ringing' of a planet-harbouring star, a team of astronomers using ESO's 3.6-m telescope have shown that it must have drifted away from the metal-rich Hyades cluster. This discovery has implications for theories of star and planet formation, and for the dynamics of our Milky Way. ESO PR Photo 09a/08 ESO PR Photo 09a/08 Iota Horologii The yellow-orange star Iota Horologii, located 56 light-years away towards the southern Horologium ("The Clock") constellation, belongs to the so-called "Hyades stream", a large number of stars that move in the same direction. Previously, astronomers using an ESO telescope had shown that the star harbours a planet, more than 2 times as large as Jupiter and orbiting in 320 days (ESO 12/99). But until now, all studies were unable to pinpoint the exact characteristics of the star, and hence to understand its origin. A team of astronomers, led by Sylvie Vauclair from the University of Toulouse, France, therefore decided to use the technique of 'asteroseismology' to unlock the star's secrets. "In the same way as geologists monitor how seismic waves generated by earthquakes propagate through the Earth and learn about the inner structure of our planet, it is possible to study sound waves running through a star, which forms a sort of large, spherical bell," says Vauclair. The 'ringing' from this giant musical instrument provides astronomers with plenty of information about the physical conditions in the star's interior. And to 'listen to the music', the astronomers used one of the best instruments available. The observations were conducted in November 2006 during 8 consecutive nights with the state-of-the-art HARPS spectrograph mounted on the ESO 3.6-m telescope at La Silla. Up to 25 'notes' could be identified in the unique dataset, most of them corresponding to waves having a period of about 6.5 minutes. These observations allowed the astronomers to obtain a very precise portrait of Iota Horologii: its

  7. Isolating Triggered Star Formation

    Energy Technology Data Exchange (ETDEWEB)

    Barton, Elizabeth J.; Arnold, Jacob A.; /UC, Irvine; Zentner, Andrew R.; /KICP, Chicago /Chicago U., EFI; Bullock, James S.; /UC, Irvine; Wechsler, Risa H.; /KIPAC, Menlo

    2007-09-12

    Galaxy pairs provide a potentially powerful means of studying triggered star formation from galaxy interactions. We use a large cosmological N-body simulation coupled with a well-tested semi-analytic substructure model to demonstrate that the majority of galaxies in close pairs reside within cluster or group-size halos and therefore represent a biased population, poorly suited for direct comparison to 'field' galaxies. Thus, the frequent observation that some types of galaxies in pairs have redder colors than 'field' galaxies is primarily a selection effect. We use our simulations to devise a means to select galaxy pairs that are isolated in their dark matter halos with respect to other massive subhalos (N= 2 halos) and to select a control sample of isolated galaxies (N= 1 halos) for comparison. We then apply these selection criteria to a volume-limited subset of the 2dF Galaxy Redshift Survey with M{sub B,j} {le} -19 and obtain the first clean measure of the typical fraction of galaxies affected by triggered star formation and the average elevation in the star formation rate. We find that 24% (30.5 %) of these L* and sub-L* galaxies in isolated 50 (30) h{sup -1} kpc pairs exhibit star formation that is boosted by a factor of {approx}> 5 above their average past value, while only 10% of isolated galaxies in the control sample show this level of enhancement. Thus, 14% (20 %) of the galaxies in these close pairs show clear triggered star formation. Our orbit models suggest that 12% (16%) of 50 (30) h{sup -1} kpc close pairs that are isolated according to our definition have had a close ({le} 30 h{sup -1} kpc) pass within the last Gyr. Thus, the data are broadly consistent with a scenario in which most or all close passes of isolated pairs result in triggered star formation. The isolation criteria we develop provide a means to constrain star formation and feedback prescriptions in hydrodynamic simulations and a very general method of understanding

  8. The formation of stars

    CERN Document Server

    Stahler, Steven W

    2008-01-01

    This book is a comprehensive treatment of star formation, one of the most active fields of modern astronomy. The reader is guided through the subject in a logically compelling manner. Starting from a general description of stars and interstellar clouds, the authors delineate the earliest phases of stellar evolution. They discuss formation activity not only in the Milky Way, but also in other galaxies, both now and in the remote past. Theory and observation are thoroughly integrated, with the aid of numerous figures and images. In summary, this volume is an invaluable resource, both as a text f

  9. Probing neutron star physics using accreting neutron stars

    NARCIS (Netherlands)

    Patruno, A.

    2010-01-01

    We give an obervational overview of the accreting neutron stars systems as probes of neutron star physics. In particular we focus on the results obtained from the periodic timing of accreting millisecond X-ray pulsars in outburst and from the measurement of X-ray spectra of accreting neutron stars

  10. Model Checking with Edge-Valued Decision Diagrams

    Science.gov (United States)

    Roux, Pierre; Siminiceanu, Radu I.

    2010-01-01

    We describe an algebra of Edge-Valued Decision Diagrams (EVMDDs) to encode arithmetic functions and its implementation in a model checking library. We provide efficient algorithms for manipulating EVMDDs and review the theoretical time complexity of these algorithms for all basic arithmetic and relational operators. We also demonstrate that the time complexity of the generic recursive algorithm for applying a binary operator on EVMDDs is no worse than that of Multi- Terminal Decision Diagrams. We have implemented a new symbolic model checker with the intention to represent in one formalism the best techniques available at the moment across a spectrum of existing tools. Compared to the CUDD package, our tool is several orders of magnitude faster

  11. A Visual Interface Diagram For Mapping Functions In Integrated Products

    DEFF Research Database (Denmark)

    Ingerslev, Mattias; Oliver Jespersen, Mikkel; Göhler, Simon Moritz

    2015-01-01

    In product development there is a recognized tendency towards increased functionality for each new product generation. This leads to more integrated and complex products, with the risk of development delays and quality issues as a consequence of lacking overview and transparency. The work described...... in this article has been conducted in collaboration with Novo Nordisk on the insulin injection device FlexTouch® as case product. The FlexTouch® reflects the characteristics of an integrated product with several functions shared between a relatively low number of parts. In this article we present a novel way...... of visualizing relations between parts and functions in highly integrated mechanical products. The result is an interface diagram that supports design teams in communication, decision making and design management. The diagram gives the designer an overview of the couplings and dependencies within a product...

  12. SOURCES OF SUPPLY CHAIN CONFLICTS – A FISHBONE DIAGRAM CORRELATION

    Directory of Open Access Journals (Sweden)

    Gabriel-Cristian CONSTANTINESCU

    2017-05-01

    Full Text Available Identifying the sources of conflict in a supply chain is the starting point of managing conflicts along chain and initiating the proper actions for lasting outcomes. An extended review of literature on sources of supply chain conflict was concluded with an ample list of various causes. The conflicts sources were classified in 8 categories: commercial, financial, logistics, management, quality, relationship along the chain, inter-personal communication and business environment. The main identified category of conflict sources was relationship along the chain, but commercial, financial, management and logistics were also important categories of conflict cause. The overall analysis emphasizes a fishbone diagram of supply chain conflict causes, having the 8 identified categories as branches and being highly developed with the related sources. This general diagram could be a good lead-off for a deeper analysis of conflict causes in a particular supply chain.

  13. Oak Ridge K-25 Site Technology Logic Diagram

    Energy Technology Data Exchange (ETDEWEB)

    Fellows, R.L. (ed.)

    1993-02-26

    The Oak Ridge K-25 Technology Logic Diagram (TLD), a decision support tool for the K-25 Site, was developed to provide a planning document that relates envirorunental restoration and waste management problems at the Oak Ridge K-25 Site to potential technologies that can remediate these problems. The TLD technique identifies the research necessary to develop these technologies to a state that allows for technology transfer and application to waste management, remedial action, and decontamination and decommissioning activities. The TLD consists of four separate volumes-Vol. 1, Vol. 2, Vol. 3A, and Vol. 3B. Volume 1 provides introductory and overview information about the TLD. This volume, Volume 2, contains logic diagrams with an index. Volume 3 has been divided into two separate volumes to facilitate handling and use.

  14. Phase Diagrams of Electrostatically Self-Assembled Amphiplexes

    Energy Technology Data Exchange (ETDEWEB)

    V Stanic; M Mancuso; W Wong; E DiMasi; H Strey

    2011-12-31

    We present the phase diagrams of electrostatically self-assembled amphiplexes (ESA) comprised of poly(acrylic acid) (PAA), cetyltrimethylammonium chloride (CTACl), dodecane, pentanol, and water at three different NaCl salt concentrations: 100, 300, and 500 mM. This is the first report of phase diagrams for these quinary complexes. Adding a cosurfactant, we were able to swell the unit cell size of all long-range ordered phases (lamellar, hexagonal, Pm3n, Ia3d) by almost a factor of 2. The added advantage of tuning the unit cell size makes such complexes (especially the bicontinuous phases) attractive for applications in bioseparation, drug delivery, and possibly in oil recovery.

  15. Magnetic phase diagram of Ho/Er alloys

    DEFF Research Database (Denmark)

    Cowley, R.A.; Simpson, J.A.; Bryn-Jacobsen, C.

    1998-01-01

    are found, arising from the competition between the exchange and anisotropic crystal-field interactions, the latter of which are of opposite sign for Ho and Er. The magnetic phase diagram has five distinct phases with long-range magnetic order: basal-plane helical, tilted helical, cycloidal, c......-axis longitudinally modulated, and conical. The cycloid and tilted helix have both incommensurate and commensurate q = 1/4c* forms, and all of the thin films have a conical structure at low temperatures, even though corresponding films of pure Ho and Er do not exhibit this phase. There is a pentacritical point......, and probably a disordered phase which is completely surrounded in the phase diagram by magnetic phases with long-range order. A Landau theory is developed to describe these results....

  16. (Big Data, Diagram Aesthetics and the Question concerning Beauty

    Directory of Open Access Journals (Sweden)

    Falk Heinrich

    2016-03-01

    The article’s introductory part presents some examples of data visualisations and introduces relevant notions of beauty and big data. The main part discusses the changes in our concept of beauty by analysing data visualisation in the light of conceptual art and its aesthetics of the sublime. Data visualizations present potentially unfathomable and complex information that is associated with the sublime, but represent data in a way that allows for understanding by means of imaginations, which are aspects of beauty. The article elaborates on the simultaneity of and oscillation between aesthetic beauty and the aesthetic sublime, by introducing Deleuze’s understandings of the concept of the diagram that is able to mediate between visualisation as representation and diagrams as performative machine of formation and displacement of data relations.

  17. Formal verification of Simulink/Stateflow diagrams a deductive approach

    CERN Document Server

    Zhan, Naijun; Zhao, Hengjun

    2017-01-01

    This book presents a state-of-the-art technique for formal verification of continuous-time Simulink/Stateflow diagrams, featuring an expressive hybrid system modelling language, a powerful specification logic and deduction-based verification approach, and some impressive, realistic case studies. Readers will learn the HCSP/HHL-based deductive method and the use of corresponding tools for formal verification of Simulink/Stateflow diagrams. They will also gain some basic ideas about fundamental elements of formal methods such as formal syntax and semantics, and especially the common techniques applied in formal modelling and verification of hybrid systems. By investigating the successful case studies, readers will realize how to apply the pure theory and techniques to real applications, and hopefully will be inspired to start to use the proposed approach, or even develop their own formal methods in their future work.

  18. Magnetic phase diagrams of classical triangular and kagome antiferromagnets

    Energy Technology Data Exchange (ETDEWEB)

    Gvozdikova, M V [Department of Physics, Kharkov National University, 61077 Kharkov (Ukraine); Melchy, P-E; Zhitomirsky, M E, E-mail: mike.zhitomirsky@cea.fr [Service de Physique Statistique, Magnetisme et Supraconductivite, UMR-E9001 CEA-INAC/UJF, 17 rue des Martyrs, 38054 Grenoble (France)

    2011-04-27

    We investigate the effect of geometrical frustration on the H-T phase diagrams of the classical Heisenberg antiferromagnets on triangular and kagome lattices. The phase diagrams for the two models are obtained from large-scale Monte Carlo simulations. For the kagome antiferromagnet, thermal fluctuations are unable to lift degeneracy completely and stabilize translationally disordered multipolar phases. We find a substantial difference in the temperature scales of the order by disorder effect related to different degeneracy of the low- and the high-field classical ground states in the kagome antiferromagnet. In the low-field regime, the Kosterlitz-Thouless transition into a spin-nematic phase is produced by unbinding of half-quantum vortices.

  19. Oak Ridge K-25 Site Technology Logic Diagram

    Energy Technology Data Exchange (ETDEWEB)

    Fellows, R.L. (ed.)

    1993-02-26

    The Oak Ridge K-25 Technology Logic Diagram (TLD), a decision support tool for the K-25 Site, was developed to provide a planning document that relates environmental restoration and waste management problems at the Oak Ridge K-25 Site to potential technologies that can remediate these problems. The TLD technique identifies the research necessary to develop these technologies to a state that allows for technology transfer and application to waste management, remedial action, and decontamination and decommissioning activities. The TLD consists of four separate volumes-Vol. 1, Vol. 2, Vol. 3A, and Vol. 3B. Volume 1 provides introductory and overview information about the TLD. Volume 2 contains logic diagrams. Volume 3 has been divided into two separate volumes to facilitate handling and use. This report is part A of Volume 3 concerning characterization, decontamination, and dismantlement.

  20. Numerical Simulation of Nonperiodic Rail Operation Diagram Characteristics

    Directory of Open Access Journals (Sweden)

    Yongsheng Qian

    2014-01-01

    Full Text Available This paper succeeded in utilizing cellular automata (CA model to simulate the process of the train operation under the four-aspect color light system and getting the nonperiodic diagram of the mixed passenger and freight tracks. Generally speaking, the concerned models could simulate well the situation of wagon in preventing trains from colliding when parking and restarting and of the real-time changes the situation of train speeds and displacement and get hold of the current train states in their departures and arrivals. Finally the model gets the train diagram that simulates the train operation in different ratios of the van and analyzes some parameter characters in the process of train running, such as time, speed, through capacity, interval departing time, and departing numbers.