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Sample records for blazhko star rr

  1. Kepler photometry of the prototypical Blazhko star RR Lyr: an old friend seen in a new light

    DEFF Research Database (Denmark)

    Kolenberg, Katrien; Bryson, S.; Szabó, R.

    2011-01-01

    We present our analysis of the long-cadence Kepler data for the well-studied Blazhko star RR Lyr, gathered during the first two quarters of the satellite's observations and covering a total of 127 d. Besides being of great importance for our understanding of RR Lyrae stars in general, these RR Lyr...... data can be regarded as a case study for observations of bright stars with Kepler. Kepler can perform high-precision photometry on targets like RR Lyr, as the saturated flux is conserved to a very high degree. The Kepler data on RR Lyr are revolutionary in several respects. Even with long......-cadence sampling (one measurement per 29.4 min), the unprecedented precision (star's extreme light-curve variations in detail. The multiplet structures at the main frequency and its harmonics, typical for Blazhko stars, are clearly detected up...

  2. First Kepler Results on RR Lyrae Stars

    DEFF Research Database (Denmark)

    Kolenberg, K.; Szabó, R.; Kurtz, D. W.

    2010-01-01

    We present the first results of our analyses of selected RR Lyrae stars for which data have been obtained by the Kepler Mission. As expected, we find a significant fraction of the RRab stars to show the Blazhko effect, a still unexplained phenomenon that manifests itself as periodic amplitude and...

  3. The complex case of V445 Lyr observed with Kepler: two Blazhko modulations, a non-radial mode, possible triple mode RR Lyrae pulsation, and more

    DEFF Research Database (Denmark)

    Guggenberger, E.; Kolenberg, K.; Nemec, J. M.

    2012-01-01

    Rapid and strong changes in the Blazhko modulation of RR Lyrae stars, as they have recently been detected in high precision satellite data, have become a crucial topic in finding an explanation of the long-standing mystery of the Blazhko effect. We present here an analysis of the most extreme cas...

  4. RR Lyrae Stars in M4

    Science.gov (United States)

    Kuehn, Charles A.; Moskalik, Pawel; Drury, Jason A.

    2017-10-01

    Observations by Kepler/K2 have revolutionized the study of RR Lyrae stars by allowing the detection of new phenomna, such as low amplitude additional modes and period doubling, which had not previously been seen from the ground. During campaign 2, K2 observed the globular cluster M4, providiing the first opportunity to study a sizeable group of RR Lyrae stars that belong to a single population; the other RR Lyrae stars that have been observed from space are field stars in the galactic halo and thus belong to an assortment of populations. In this poster we present the results of our study of the RR Lyrae variables in M4 from K2 photometry. We have identified additional, low amplitude pulsation modes in both observed RRc stars. In 3 RRab stars we have found the Blazhko effect with periods of 16.6d, 22.4d, and 44.5d.

  5. RR Lyrae Stars in M4

    Directory of Open Access Journals (Sweden)

    Kuehn Charles A

    2017-01-01

    Full Text Available Observations by Kepler/K2 have revolutionized the study of RR Lyrae stars by allowing the detection of new phenomna, such as low amplitude additional modes and period doubling, which had not previously been seen from the ground. During campaign 2, K2 observed the globular cluster M4, providiing the first opportunity to study a sizeable group of RR Lyrae stars that belong to a single population; the other RR Lyrae stars that have been observed from space are field stars in the galactic halo and thus belong to an assortment of populations. In this poster we present the results of our study of the RR Lyrae variables in M4 from K2 photometry. We have identified additional, low amplitude pulsation modes in both observed RRc stars. In 3 RRab stars we have found the Blazhko effect with periods of 16.6d, 22.4d, and 44.5d.

  6. Metal Abundances, Radial Velocities, and Other Physical Characteristics for the RR Lyrae Stars in The Kepler Field

    Science.gov (United States)

    Nemec, James M.; Cohen, Judith G.; Ripepi, Vincenzo; Derekas, Aliz; Moskalik, Pawel; Sesar, Branimir; Chadid, Merieme; Bruntt, Hans

    2013-08-01

    Spectroscopic iron-to-hydrogen ratios, radial velocities, atmospheric parameters, and new photometric analyses are presented for 41 RR Lyrae stars (and one probable high-amplitude δ Sct star) located in the field-of-view of the Kepler space telescope. Thirty-seven of the RR Lyrae stars are fundamental-mode pulsators (i.e., RRab stars) of which sixteen exhibit the Blazhko effect. Four of the stars are multiperiodic RRc pulsators oscillating primarily in the first-overtone mode. Spectroscopic [Fe/H] values for the 34 stars for which we were able to derive estimates range from -2.54 ± 0.13 (NR Lyr) to -0.05 ± 0.13 dex (V784 Cyg), and for the 19 Kepler-field non-Blazhko stars studied by Nemec et al. the abundances agree will with their photometric [Fe/H] values. Four non-Blazhko RR Lyrae stars that they identified as metal-rich (KIC 6100702, V2470 Cyg, V782 Cyg and V784 Cyg) are confirmed as such, and four additional stars (V839 Cyg, KIC 5520878, KIC 8832417, KIC 3868420) are also shown here to be metal-rich. Five of the non-Blazhko RRab stars are found to be more metal-rich than [Fe/H] ~-0.9 dex while all of the 16 Blazhko stars are more metal-poor than this value. New P-\\phi _31^s-[Fe/H] relationships are derived based on ~970 days of quasi-continuous high-precision Q0-Q11 long- and short-cadence Kepler photometry. With the exception of some Blazhko stars, the spectroscopic and photometric [Fe/H] values are in good agreement. Several stars with unique photometric characteristics are identified, including a Blazhko variable with the smallest known amplitude and frequency modulations (V838 Cyg). Based in part on observations made 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 Keck Observatory was made possible by the generous financial support of the W.M. Keck Foundation. Also, based in part on

  7. First detection of multi-shocks in RR Lyrae stars from Antarctica : A possible explanation of the Blazhko effect

    International Nuclear Information System (INIS)

    Chadid, M.; Vernin, J.; Zalian, C.; Pouzenc, C.; Abe, L.; Agabi, A.; Aristidi, E.; Mékarnia, D.; Preston, G.; Liu, L.Y.; Trinquet, H.

    2014-01-01

    We present the first detection of multi-shocks propagating through the atmosphere of the Blazhko star S Arae using uninterrupted, accurate optical photometric data collected during one polar night, 150 days from Antarctica at Dome C, with the Photometer AntarctIca eXtinction (PAIX). We acquired 89,736 CCD frames during 323 pulsation cycles and 3 Blazhko cycles. We detected two new light curve properties in the PAIX light curve, jump and rump, which we associated with two new post-maximum shock waves Sh PM1 and Sh PM2 . jump, lump, rump, bump, and hump are induced by five shock waves, with different amplitudes and origins, Sh PM1 , Sh PM , Sh PM2 , Sh PM3 , and the main shock Sh H+He . Correlations between the length of rise time and light amplitude and Sh PM3 are monotonous during three Blazhko cycles, but the pulsation curve is double peaked. We discuss the physical mechanisms driving the modulation of these quantities. Finally, we hypothesize that the origin of the Blazhko effect is a dynamical interaction between a multi-shock structure and an outflowing wind in a coronal structure.

  8. First detection of multi-shocks in RR Lyrae stars from Antarctica : A possible explanation of the Blazhko effect

    Energy Technology Data Exchange (ETDEWEB)

    Chadid, M.; Vernin, J.; Zalian, C.; Pouzenc, C.; Abe, L.; Agabi, A.; Aristidi, E.; Mékarnia, D. [Université Nice Sophia-Antipolis, Observatoire de la Côte d' Azur, UMR 7293, Parc Valrose, F-06108 Nice Cedex 02 (France); Preston, G. [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Liu, L.Y. [National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing (China); Trinquet, H., E-mail: chadid@unice.fr [DGA Matrise de l' Information, BP 7, F-35998 Rennes Armees (France)

    2014-11-01

    We present the first detection of multi-shocks propagating through the atmosphere of the Blazhko star S Arae using uninterrupted, accurate optical photometric data collected during one polar night, 150 days from Antarctica at Dome C, with the Photometer AntarctIca eXtinction (PAIX). We acquired 89,736 CCD frames during 323 pulsation cycles and 3 Blazhko cycles. We detected two new light curve properties in the PAIX light curve, jump and rump, which we associated with two new post-maximum shock waves Sh{sub PM1} and Sh{sub PM2}. jump, lump, rump, bump, and hump are induced by five shock waves, with different amplitudes and origins, Sh{sub PM1}, Sh{sub PM}, Sh{sub PM2}, Sh{sub PM3}, and the main shock Sh{sub H+He}. Correlations between the length of rise time and light amplitude and Sh{sub PM3} are monotonous during three Blazhko cycles, but the pulsation curve is double peaked. We discuss the physical mechanisms driving the modulation of these quantities. Finally, we hypothesize that the origin of the Blazhko effect is a dynamical interaction between a multi-shock structure and an outflowing wind in a coronal structure.

  9. Analysis of a selected sample of RR Lyrae stars in the LMC from OGLE-III

    International Nuclear Information System (INIS)

    Chen Bing-Qiu; Jiang Bi-Wei; Yang Ming

    2013-01-01

    A systematic study of RR Lyrae stars is performed using a selected sample of 655 objects in the Large Magellanic Cloud (LMC) with long-term observations and numerous measurements from the Optical Gravitational Lensing Experiment III project. The phase dispersion method and linear superposition of the harmonic oscillations are used to derive the pulsation frequency and properties of light variation. It is found that a dichotomy exists in Oosterhoff Type I and Oosterhoff Type II for RR Lyrae stars in the LMC. Due to our strict criteria for identifying a frequency, a lower limit for the incidence rate of Blazhko modulation in the LMC is estimated in various subclasses of RR Lyrae stars. For fundamental-mode RR Lyrae stars, the rate of 7.5% is smaller than the previous result. In the case of the first-overtone RR Lyrae variables, the rate of 9.1% is relatively high. In addition to the Blazhko variables, 15 objects are identified to pulsate in the fundamental/first-overtone double mode. Furthermore, four objects show a period ratio around 0.6, which makes them very likely to be rare pulsators in the fundamental/second-overtone double mode. (research papers)

  10. Studying RR Lyrae Stars in M4 with K2

    Science.gov (United States)

    Kuehn, Charles A.; Drury, Jason; Moskalik, Pawel

    2017-01-01

    Observations by Kepler/K2 have revolutionized the study of RR Lyrae stars by allowing the detection of new phenomena, such as low amplitude additional modes and period doubling, which had not previously been seen from the ground. During its campaign 2, K2 observed the globular cluster M4, providing the first opportunity to study a sizeable group of RR Lyrae stars that belong to a single population; the other RR Lyrae stars that have been observed from space are field stars in the galactic halo and thus belong to an assortment of populations. We present the results of our study of the RR Lyrae variables in M4 from K2 photometry. We have identified additional, low amplitude pulsation modes in the two observed RRc stars. In three RRab stars we have found the Blazhko effect with periods of 16.6 days, 22.4 days, and 44.5 days.

  11. THE ALL-SKY GEOS RR Lyr SURVEY WITH THE TAROT TELESCOPES: ANALYSIS OF THE BLAZHKO EFFECT

    International Nuclear Information System (INIS)

    Le Borgne, J.-F.; Klotz, A.; Poretti, E.; Boër, M.; Butterworth, N.; Dvorak, S.; Dumont, M.; Hambsch, F.-J.; Vandenbroere, J.; Hund, F.; Kugel, F.; Vilalta, J. M.

    2012-01-01

    We used the GEOS database to study the Blazhko effect of galactic RRab stars. The database is continuously enriched by maxima supplied by amateur astronomers and by a dedicated survey by means of the two TAROT robotic telescopes. The same value of the Blazhko period is observed at different values of the pulsation periods and different values of the Blazhko periods are observed at the same value of the pulsation period. There are clues suggesting that the Blazhko effect is changing from one cycle to the next. The secular changes in the pulsation and Blazhko periods of Z CVn are anticorrelated. The diagrams of magnitudes against phases of the maxima clearly show that the light curves of Blazhko variables can be explained as modulated signals, both in amplitude and in frequency. The closed curves describing the Blazhko cycles in such diagrams have different shapes, reflecting the phase shifts between the epochs of the brightest maximum and the maximum O – C. Our sample shows that both clockwise and counterclockwise directions are possible for similar shapes. The improved observational knowledge of the Blazhko effect, in addition to some peculiarities of the light curves, has yet to be explained by a satisfactory physical mechanism.

  12. THE ALL-SKY GEOS RR Lyr SURVEY WITH THE TAROT TELESCOPES: ANALYSIS OF THE BLAZHKO EFFECT

    Energy Technology Data Exchange (ETDEWEB)

    Le Borgne, J.-F.; Klotz, A.; Poretti, E. [Universite de Toulouse, UPS-OMP, IRAP, 31400 Toulouse (France); Boeer, M. [ARTEMIS, Universite Nice Sophia-Antipolis, CNRS, Observatoire de la Cote d' Azur, Nice (France); Butterworth, N.; Dvorak, S. [American Association of Variable Star Observers (AAVSO), 49 Bay State Rd., Cambridge, MA 02138 (United States); Dumont, M.; Hambsch, F.-J.; Vandenbroere, J. [Groupe Europeen d' Observations Stellaires (GEOS), 23 Parc de Levesville, 28300 Bailleau l' Eveque (France); Hund, F. [Bundesdeutsche Arbeitsgemeinschaft fuer Veraenderliche Sterne e.V. (BAV), Munsterdamm 90, 12169 Berlin (Germany); Kugel, F. [Observatoire Chante-Perdrix, 04150 Banon (France); Vilalta, J. M. [Agrupacio Astronomica de Sabadell (AAS), Apartat de Correus, 50, 08200 Sabadell, Barcelona (Spain)

    2012-08-15

    We used the GEOS database to study the Blazhko effect of galactic RRab stars. The database is continuously enriched by maxima supplied by amateur astronomers and by a dedicated survey by means of the two TAROT robotic telescopes. The same value of the Blazhko period is observed at different values of the pulsation periods and different values of the Blazhko periods are observed at the same value of the pulsation period. There are clues suggesting that the Blazhko effect is changing from one cycle to the next. The secular changes in the pulsation and Blazhko periods of Z CVn are anticorrelated. The diagrams of magnitudes against phases of the maxima clearly show that the light curves of Blazhko variables can be explained as modulated signals, both in amplitude and in frequency. The closed curves describing the Blazhko cycles in such diagrams have different shapes, reflecting the phase shifts between the epochs of the brightest maximum and the maximum O - C. Our sample shows that both clockwise and counterclockwise directions are possible for similar shapes. The improved observational knowledge of the Blazhko effect, in addition to some peculiarities of the light curves, has yet to be explained by a satisfactory physical mechanism.

  13. Does Kepler unveil the mystery of the Blazhko effect? First detection of period doubling in Kepler Blazhko RR Lyrae stars

    DEFF Research Database (Denmark)

    Szabó, R.; Kollath, Z.; Molnár, L.

    2010-01-01

    -doubling bifurcation in our non-linear RR Lyrae models computed by the Florida-Budapest hydrocode. This enabled us to trace the origin of this instability in RR Lyrae stars to a resonance, namely a 9:2 resonance between the fundamental mode and a high-order (ninth) radial overtone showing strange-mode characteristics...

  14. RR LYRAE ATMOSPHERICS: WRINKLES OLD AND NEW. A PREVIEW

    International Nuclear Information System (INIS)

    Preston, George W.

    2011-01-01

    I report some results of an echelle spectroscopic survey of RR Lyrae stars begun in 2006 that I presented in my Henry Norris Lecture of 2010 January 4. Topics include (1) atmospheric velocity gradients, (2) phase-dependent envelope turbulence as it relates to Peterson's discoveries of axial rotation on the horizontal branch and to Stothers' explanation of the Blazhko effect, (3) the three apparitions of hydrogen emission during a pulsation cycle, (4) the occurrence of He I lines in emission and absorption, (5) detection of He II emission and metallic line doubling in Blazhko stars, and finally (6) speculation about what helium observations of RR Lyrae stars in omega Centauri might tell us about the putative helium populations and the horizontal branch of that strange globular cluster.

  15. Pulsations and period changes of the non-Blazhko RR lyrae variable Y oct observed from Dome A, Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Zhihua, Huang; Jianning, Fu; Weikai, Zong; Lingzhi, Wang; Zonghong, Zhu [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); M, Macri Lucas; Lifan, Wang [Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, College Station, TX (United States); Ashley, Michael C. B.; S, Lawrence Jon; Daniel, Luong-Van [School of Physics, University of New South Wales, NSW (Australia); Xiangqun, Cui; Long-Long, Feng; Xuefei, Gong; Qiang, Liu; Huigen, Yang; Xiangyan, Yuan; Xu, Zhou; Zhenxi, Zhu [Chinese Center for Antarctic Astronomy, Nanjing (China); R, Pennypacker Carl [Center for Astrophysics, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); G, York Donald, E-mail: jnfu@bnu.edu.cn [Department of Astronomy and Astrophysics and Enrico Fermi Institute, University of Chicago, Chicago, IL (United States)

    2015-01-01

    During the operation of the Chinese Small Telescope Array (CSTAR) in Dome A of Antarctica in the years 2008, 2009, and 2010, large amounts of photometric data have been obtained for variable stars in the CSTAR field. We present here the study of one of six RR Lyrae variables, Y Oct, observed with CSTAR in Dome A, Antarctica. Photometric data in the i band were obtained in 2008 and 2010, with a duty cycle (defined as the fraction of time representing scientifically available data to CSTAR observation time) of about 44% and 52%, respectively. In 2009, photometric data in the g and r bands were gathered for this star, with a duty cycle of 65% and 60%, respectively. Fourier analysis of the data in the three bands only shows the fundamental frequency and its harmonics, which is characteristic of the non-Blazhko RR Lyrae variables. Values of the fundamental frequency and the amplitudes, as well as the total pulsation amplitude, are obtained from the data in the three bands separately. The amplitude of the fundamental frequency and the total pulsation amplitude in the g band are the largest, and those in the i band the smallest. Two-hundred fifty-one times of maximum are obtained from the three seasons of data, which are analyzed together with 38 maximum times provided in the GEOS RR Lyrae database. A period change rate of −0.96 ± 0.07 days Myr{sup −1} is then obtained, which is a surprisingly large negative value. Based on relations available in the literature, the following physical parameters are derived: [Fe/H] = −1.41 ± 0.14, M{sub V} = 0.696 ± 0.014 mag, V−K = 1.182 ± 0.028 mag, logT{sub eff} = 3.802 ± 0.003 K, logg = 2.705 ± 0.004, logL/L{sub ⊙} = 1.625 ± 0.013, and logM/M{sub ⊙} = −0.240 ± 0.019.

  16. 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.

  17. Dynamical investigation of modulated Kepler RR Lyrae stars

    Directory of Open Access Journals (Sweden)

    Plachy E.

    2015-01-01

    Full Text Available We performed a non-linear dynamical analysis on the Blazhko modulation for the first time. Our results suggest that the detection of chaotic nature behind the phenomenon is limited by the instrumental effects and the data processing problems of the Kepler pipeline concerning high-amplitude variable stars.

  18. High-precision 2MASS JHK{sub s} light curves and other data for RR Lyrae star SDSS J015450 + 001501: Strong constraints for nonlinear pulsation models

    Energy Technology Data Exchange (ETDEWEB)

    Szabó, Róbert; Ivezić, Željko; Kiss, László L.; Kolláth, Zoltán [Konkoly Observatory, MTA CSFK, Konkoly Thege Miklós út 15-17, H-1121 Budapest (Hungary); Jones, Lynne; Becker, Andrew C.; Davenport, James R. A. [Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); Sesar, Branimir [Division of Physics, Mathematics and Astronomy, Caltech, Pasadena, CA 91125 (United States); Cutri, Roc M., E-mail: rszabo@konkoly.hu [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States)

    2014-01-01

    We present and discuss an extensive data set for the non-Blazhko ab-type RR Lyrae star SDSS J015450+001501, including optical Sloan Digital Sky Survey ugriz light curves and spectroscopic data, LINEAR and Catalina Sky Survey unfiltered optical light curves, and infrared Two Micron All Sky Survey (2MASS) JHK{sub s} and Wide-field Infrared Survey Explorer W1 and W2 light curves. Most notable is that light curves obtained by 2MASS include close to 9000 photometric measures collected over 3.3 yr and provide an exceedingly precise view of near-infrared variability. These data demonstrate that static atmosphere models are insufficient to explain multiband photometric light-curve behavior and present strong constraints for nonlinear pulsation models for RR Lyrae stars. It is a challenge to modelers to produce theoretical light curves that can explain data presented here, which we make publicly available.

  19. Exploring M33 Through RR Lyrae Stars

    OpenAIRE

    Pritzl, Barton J.

    2013-01-01

    Recent surveys have detected RR Lyrae stars in M33, the Triangulum Galaxy. These variable stars are excellent tracers of ancient stellar populations. The RR Lyrae stars have been used to estimate metallicities at various locations within M33, as well as determining the distance to the galaxy. A summary of the M33 RR Lyrae stars is presented here as well as an analysis on what their properties imply for the unique M33 galaxy

  20. VARIABLE STARS IN THE LARGE MAGELLANIC CLOUD GLOBULAR CLUSTER NGC 2257. I. RESULTS BASED ON 2007-2008 B, V PHOTOMETRY

    International Nuclear Information System (INIS)

    Nemec, James M.; Walker, Alistair; Jeon, Young-Beom

    2009-01-01

    The variable stars in the Large Magellanic Cloud star cluster NGC 2257 are reinvestigated using photometry (to ∼20th mag) of over 400 new B, V CCD images taken with the CTIO 0.9 m telescope on 14 nights in 2007 December and 2008 January. New period searches have been made using two independent algorithms (CLEAN, Period04); the resultant periods of most of the stars are consistent with the pulsation periods derived previously, and where there are discrepancies these have been resolved. For the B and V light curves, accurate Fourier coefficients and parameters are given. Six new variable stars have been discovered (V45-50), including a bright candidate long-period variable star showing secondary oscillations (V45) and two anomalously bright RRc stars (V48 and V50), which are shown to be brightened and reddened by nearby red giant stars. Also discovered among the previously known variable stars are three double-mode RR Lyrae stars (V8, V16, and V34) and several Blazhko variables. Archival Hubble Space Telescope images and the photometry by Johnson et al. have been used to define better the properties of the most crowded variable stars. The total number of cluster variable stars now stands at forty-seven: 23 RRab stars, four of which show Blazhko amplitude variations; 20 RRc stars, one showing clear Blazhko variations and another showing possible Blazhko variations; the three RRd stars, all having the dominant period ∼0.36 day and period ratios P 1 /P 0 ∼0.7450; and an LPV star located near the tip of the red giant branch. A comparison of the RRd stars with those in other environments shows them to be most similar to those in IC4499.

  1. Flavours of variability

    DEFF Research Database (Denmark)

    Benkö, J.M.; Kolenberg, Katrien; Szabó, R.

    2010-01-01

    frequencies beyond the well-known harmonics and Blazhko multiplets have been found. These frequencies are located around the half-integer multiples of the main pulsation frequency for at least three stars. In four stars, these frequencies are close to the first and/or second overtone modes. The amplitudes...... of these periodicities seem to vary over the Blazhko cycle. V350 Lyr, a non-Blazhko star in our sample, is the first example of a double-mode RR Lyrae star that pulsates in its fundamental and second overtone modes....

  2. Radial velocities of RR Lyrae stars

    International Nuclear Information System (INIS)

    Hawley, S.L.; Barnes, T.G. III

    1985-01-01

    283 spectra of 57 RR Lyrae stars have been obtained using the 2.1-m telescope at McDonald Observatory. Radial velocities were determined using a software cross-correlation technique. New mean radial velocities were determined for 46 of the stars. 11 references

  3. VARIABLE STARS IN THE GLOBULAR CLUSTER NGC 2808

    International Nuclear Information System (INIS)

    Kunder, Andrea; Walker, Alistair R.; Stetson, Peter B.; Catelan, Márcio; Amigo, Pía

    2013-01-01

    The first calibrated broadband BVI time-series photometry is presented for the variable stars in NGC 2808, with observations spanning a range of 28 years. We have also redetermined the variability types and periods for the variable stars identified previously by Corwin et al., revising the number of probable fundamental-mode RR Lyrae variables (RR0) to 11 and the number of first-overtone variables (RR1) to five. Our observations were insufficient to discern the nature of the previously identified RR1 star, V24, and the tentatively identified RR1 star, V13. These two variables are ∼0.8 mag brighter than the RR Lyrae variables, appear to have somewhat erratic period and/or luminosity changes, and lie inside the RR Lyrae instability strip. Curiously, all but one of the RR Lyrae stars studied in this relatively metal-rich cluster exhibit the Blazhko phenomenon, an effect thought to occur with higher frequency in metal-poor environments. The mean periods of the RR0 and RR1 variables are (P) RR0 = 0.56 ± 0.01 d and RR1 = 0.30 ± 0.02 d, respectively, supporting an Oosterhoff I classification of the cluster. On the other hand, the number ratio of RR1-to-RR0-type variables is high, though not unprecedented, for an Oosterhoff I cluster. The RR Lyrae variables have no period shifts at a given amplitude compared to the M3 variables, making it unlikely that these variables are He enhanced. Using the recent recalibration of the RR Lyrae luminosity scale by Catelan and Cortés, a mean distance modulus of (m – M) V = 15.57 ± 0.13 mag for NGC 2808 is obtained, in good agreement with that determined here from its type II Cepheid and SX Phoenicis population. Our data have also allowed the discovery of two new candidate SX Phoenicis stars and an eclipsing binary in the blue straggler region of the NGC 2808 color-magnitude diagram.

  4. V 1343 aquilae (SS 433) as a double-periodic star

    International Nuclear Information System (INIS)

    Goranskij, V.P.

    1983-01-01

    The new computer method of double periodicity search earlier tested on the Blazhko effect in RR Lyrae type variable stars is applied to define more precise periods of brightness variability of the binary V 1343 Aql (SS 433). Computer program was used in the two-parameter search regime. The obtained periods are P 1 = 13sup(d).074+-0sup(d).008 and P 2 = 163sup(d).8+-1sup(d).2. The periodically repeating brithness curve deeps treated as primary minima (the accretion disc eclipsed by the star) vary their shape with the phase of period P 2 . The expected eclipse at 1979 October 16 did nor occur

  5. Period Changes of 23 Field RR Lyrae Stars

    Directory of Open Access Journals (Sweden)

    Soo-Chang Rey

    1994-12-01

    Full Text Available The secular period behavior of 23 field RR Lyrae stars is studied in order to determine if the observed period changes could be attributed, at least in the mean, to stellar evolution. The sample of stars is subdivided into two Oosterhoff groups based on the metallicity and period-shift. Despite the small sample size, we found a distinct bias toward positive period changes in the group variables. The period changes of the group variables in globular clusters. This provides yet another support for the Lee, Demarque, and Zinn(1990 evolutionary models of RR Lyrae stars and their explanation of the Sandage period-shift effect.

  6. Contamination of RR Lyrae stars from Binary Evolution Pulsators

    Science.gov (United States)

    Karczmarek, Paulina; Pietrzyński, Grzegorz; Belczyński, Krzysztof; Stępień, Kazimierz; Wiktorowicz, Grzegorz; Iłkiewicz, Krystian

    2016-06-01

    Binary Evolution Pulsator (BEP) is an extremely low-mass member of a binary system, which pulsates as a result of a former mass transfer to its companion. BEP mimics RR Lyrae-type pulsations but has different internal structure and evolution history. We present possible evolution channels to produce BEPs, and evaluate the contamination value, i.e. how many objects classified as RR Lyrae stars can be undetected BEPs. In this analysis we use population synthesis code StarTrack.

  7. The RRc Stars: Chemical Abundances and Envelope Kinematics

    Energy Technology Data Exchange (ETDEWEB)

    Sneden, Christopher; Adamów, Monika [Department of Astronomy and McDonald Observatory, The University of Texas, Austin, TX 78712 (United States); Preston, George W. [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Chadid, Merieme, E-mail: chris@verdi.as.utexas.edu, E-mail: astromysz@gmail.com, E-mail: gwp@obs.carnegiescience.edu, E-mail: chadid@unice.fr [Université Nice Sophia–Antipolis, Observatoire de la Côte dAzur, UMR 7293, Parc Valrose, F-06108, Nice Cedex 02 (France)

    2017-10-10

    We analyzed series of spectra obtained for 12 stable RRc stars observed with the echelle spectrograph of the du Pont telescope at Las Campanas Observatory and we analyzed the spectra of RRc Blazhko stars discussed by Govea et al. We derived model atmosphere parameters, [Fe/H] metallicities, and [X/Fe] abundance ratios for 12 species of 9 elements. We co-added all spectra obtained during the pulsation cycles to increase signal to noise and demonstrate that these spectra give results superior to those obtained by co-addition in small phase intervals. The RRc abundances are in good agreement with those derived for the RRab stars of Chadid et al. We used radial velocity (RV) measurements of metal lines and H α to construct variations of velocity with phase, and center-of-mass velocities. We used these to construct RV templates for use in low- to medium-resolution RV surveys of RRc stars. Additionally, we calculated primary accelerations, radius variations, and metal and H α velocity amplitudes, which we display as regressions against primary acceleration. We employ these results to compare the atmosphere structures of metal-poor RRc stars with their RRab counterparts. Finally, we use the RV data for our Blazhko stars and the Blazhko periods of Szczygieł and Fabrycky to falsify the Blazhko oblique rotator hypothesis.

  8. Carbon and oxygen abundances of field RR Lyrae stars. I. Carbon abundances

    International Nuclear Information System (INIS)

    Butler, D.; Manduca, A.; Deming, D.; Bell, R.A.

    1982-01-01

    From an analysis of KPNO 4-m echelle plates and simultaneous uvbyβ photometry, we have determined carbon abundances and carbon-to-iron ratios for a large number of field RR Lyrae stars having [Fe/H]> or approx. =-1.2. It is found that these field RR Lyrae stars: stars which are known to be in an advanced evolutionary state: have carbon-to-iron ratios which are similar to those of unevolved stars

  9. Gauging the Galactic thick disk with RR Lyrae stars

    Directory of Open Access Journals (Sweden)

    Cruz G.

    2012-02-01

    Full Text Available In this contribution we present results from the QUEST RR Lyrae Survey of the thick disk. The survey spans ~480 sq. deg. at low latitude |b| < 30°, with multi-epoch VRI observations, obtained with the QUEST-I camera at the 1m Jürgen Stock Schmidt telescope located at the National Astronomical Observatory of Venezuela. This constitutes the first deep RR Lyrae survey of the Galactic thick disk conducted at low galactic latitudes, covering simultaneously a large range in radial (8RR Lyrae stars having accurate distances (errors <7% and individual reddenings derived from each star’s color curve at minimum light. Moreover, the use of RR Lyrae stars as tracers ensures negligible contamination from the Galactic thin disk. We find a thick disk mean scale height hZ = 0.94 ± 0.11kpc and scale length hR = 3.2 ± 0.4kpc, derived from the vertical and radial mean density profiles of RR Lyrae stars. We also find evidence of thick disk flaring and results that may suggest the thick disk radial density profile shows signs of antitruncation. We discuss our findings in the context of recent thick disk formation models.

  10. VBLUM photometry of RR Lyrae stars in ω Cen and M4

    International Nuclear Information System (INIS)

    DeBruijn, J.W.; Lub, J.

    1987-01-01

    Multicolour VBLUW photometry of RR Lyrae stars in the globular clusters M4 and ω Cen is used to derive information on reddening, blanketing, effective temperatures and gravity of these stars. The methods employed in the literature to determine the reddening of globular clusters from the UBV colours of the RR Lyrae stars are in complete agreement with the results from VBLUW photometry. The most important conclusions of the present work are: the close similarity between the RR Lyrae variables in the field and in globular clusters, and the agreement between the reddenings derived for RR Lyrae in the field and in globular clusters. This means that at least one parameter which normally is taken as a free parameter in studying globular cluster colour magnitude diagrams can be constrained very precisely

  11. The effect of Livermore OPAL opacities on the evolutionary masses of RR Lyrae stars

    Science.gov (United States)

    Yi, Sukyoung; Lee, Young-Wook; Demarque, Pierre

    1993-01-01

    We have investigated the effect of the new Livermore OPAL opacities on the evolution of horizontal-branch (HB) stars. This work was motivated by the recent stellar pulsation calculations using the new Livermore opacities, which suggest that the masses of double-mode RR Lyrae stars are 0.1-0.2 solar mass larger than those based on earlier opacities. Unlike the pulsation calculations, we find that the effect of opacity change on the evolution of HB stars is not significant. In particular, the effect of the mean masses of RR Lyrae stars is very small, showing a decrease of only 0.01-0.02 solar mass compared to the models based on old Cox-Stewart opacities. Consequently, with the new Livermore OPAL opacities, both the stellar pulsation and evolution models now predict approximately the same masses for the RR Lyrae stars. Our evolutionary models suggest that the mean masses of the RR Lyrae stars are about 0.76 and about 0.71 solar mass for M15 (Oosterhoff group II) and M3 (group I), respectively. If (alpha/Fe) = 0.4, these values are decreased by about 0.03 solar mass. Variations of the mean masses of RR Lyrae stars with HB morphology and metallicity are also presented.

  12. The VMC survey - XXVI. Structure of the Small Magellanic Cloud from RR Lyrae stars

    Science.gov (United States)

    Muraveva, T.; Subramanian, S.; Clementini, G.; Cioni, M.-R. L.; Palmer, M.; van Loon, J. Th.; Moretti, M. I.; de Grijs, R.; Molinaro, R.; Ripepi, V.; Marconi, M.; Emerson, J.; Ivanov, V. D.

    2018-01-01

    We present results from the analysis of 2997 fundamental mode RR Lyrae variables located in the Small Magellanic Cloud (SMC). For these objects, near-infrared time series photometry from the VISTA survey of the Magellanic Clouds system (VMC) and visual light curves from the OGLE IV (Optical Gravitational Lensing Experiment IV) survey are available. In this study, the multi-epoch Ks-band VMC photometry was used for the first time to derive intensity-averaged magnitudes of the SMC RR Lyrae stars. We determined individual distances to the RR Lyrae stars from the near-infrared period-absolute magnitude-metallicity (PM_{K_s}Z) relation, which has some advantages in comparison with the visual absolute magnitude-metallicity (MV-[Fe/H]) relation, such as a smaller dependence of the luminosity on interstellar extinction, evolutionary effects and metallicity. The distances we have obtained were used to study the three-dimensional structure of the SMC. The distribution of the SMC RR Lyrae stars is found to be ellipsoidal. The actual line-of-sight depth of the SMC is in the range 1-10 kpc, with an average depth of 4.3 ± 1.0 kpc. We found that RR Lyrae stars in the eastern part of the SMC are affected by interactions of the Magellanic Clouds. However, we do not see a clear bimodality observed for red clump stars, in the distribution of RR Lyrae stars.

  13. ON THE RR LYRAE STARS IN GLOBULARS. IV. ω CENTAURI OPTICAL UBVRI PHOTOMETRY

    Energy Technology Data Exchange (ETDEWEB)

    Braga, V. F.; Bono, G.; Buonanno, R. [Department of Physics, Università di Roma Tor Vergata, via della Ricerca Scientifica 1, I-00133 Roma (Italy); Stetson, P. B. [NRC-Herzberg, Dominion Astrophysical Observatory, 5071 West Saanich Road, Victoria BC V9E 2E7 (Canada); Dall’Ora, M. [INAF-Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli (Italy); Ferraro, I.; Iannicola, G.; Castellani, M. [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); Freyhammer, L. M. [Jeremiah Horrocks Institute of Astrophysics, University of Central Lancashire, Preston PR1 2HE (United Kingdom); Marengo, M.; Neeley, J. [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Valenti, E. [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei Munchen (Germany); Calamida, A. [National Optical Astronomy Observatory, 950 N Cherry Avenue, Tucson, AZ 85719 (United States); Da Silva, R.; Fabrizio, M.; Giuffrida, G. [ASDC, via del Politecnico snc, I-00133 Roma (Italy); Degl’Innocenti, S. [INFN, Sezione di Pisa, Largo Pontecorvo 3, I-56127, Pisa (Italy); Di Cecco, A. [INAF-Osservatorio Astronomico di Teramo, Via Mentore Maggini snc, Loc. Collurania, I-64100 Teramo (Italy); Freedman, W. L. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); and others

    2016-12-01

    New accurate and homogeneous optical UBVRI photometry has been obtained for variable stars in the Galactic globular cluster ω Cen (NGC 5139). We secured 8202 CCD images covering a time interval of 24 years and a sky area of 84 × 48 arcmin. The current data were complemented with data available in the literature and provided new, homogeneous pulsation parameters (mean magnitudes, luminosity amplitudes, periods) for 187 candidate ω Cen RR Lyrae (RRLs). Among them we have 101 RRc (first overtone) and 85 RRab (fundamental) variables, and a single candidate RRd (double-mode) variable. Candidate Blazhko RRLs show periods and colors that are intermediate between the RRc and RRab variables, suggesting that they are transitional objects. A comparison of the period distribution and the Bailey diagram indicates that RRLs in ω Cen show a long-period tail not present in typical Oosterhoff II (OoII) globulars. The RRLs in dwarf spheroidals and in ultra-faint dwarfs have properties between Oosterhoff intermediate and OoII clusters. Metallicity plays a key role in shaping the above evidence. These findings do not support the hypothesis that ω Cen is the core remnant of a spoiled dwarf galaxy. Using optical period–Wesenheit relations that are reddening-free and minimally dependent on metallicity we find a mean distance to ω Cen of 13.71 ± 0.08 ± 0.01 mag (semi-empirical and theoretical calibrations). Finally, we invert the I -band period–luminosity–metallicity relation to estimate individual RRLs’ metal abundances. The metallicity distribution agrees quite well with spectroscopic and photometric metallicity estimates available in the literature.

  14. A surface brightness analysis of eight RR Lyrae stars

    International Nuclear Information System (INIS)

    Hawley, S.L.; Barnes, T.G. III; Moffett, T.J.

    1987-01-01

    The authors have used a surface brightness, (V-R) relation to analyze new contemporaneous photometry and radial velocity data for 6 RR-ab type stars and to re-analyze previously published data for RR Lyrae and X Arietis. Systematic effects were found in the surface brightness at phases near minimum radius. Excluding these phases, they determine the slope of the surface brightness relation and the mean radius for each star. They also find a zero point which includes both a distance term and the zero point of the surface brightness relation. The sample includes stars with Preston's metallicity indicator ΔS = 0 to 9, with periods ranging from 0.397 days to 0.651 days. Their results indicate a log(R/R solar ) vs. log P relation in the sense that stars with longer periods have larger radii, in agreement with theoretical predictions. Their radii are consistent with bolometric magnitudes in the range 0.2 - 0.8 magnitude but accurate magnitudes must await a reliable T e - color calibration

  15. Z CVn - Still mysterious

    Science.gov (United States)

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

    2018-04-01

    We comment on short- and long-term pulsation period variations of Z CVn, a classical RR Lyrae star with the Blazhko effect. Z CVn shows cyclic-like O-C diagram that can be interpreted as a consequence of binarity throught the light travel time effect. We show that this hypothesis is false and that the observed long-term period variations must be caused by some effect that is intrinsic to the star. We also show that the Blazhko period is not simply anti-correlated with the long-term period variations as was suggested by previous authors.

  16. EPIC 201585823, a rare triple-mode RR Lyrae star discovered in K2 mission data

    DEFF Research Database (Denmark)

    Kurtz, Donald W.; Bowman, Dominic M.; Ebo, Simon J.

    2016-01-01

    We have discovered a new, rare triple-mode RR Lyr star, EPIC 201585823, in the Kepler K2 mission Campaign 1 data. This star pulsates primarily in the fundamental and first-overtone radial modes, and, in addition, a third non-radial mode. The ratio of the period of the non-radial mode...... pixels with significant signal for the star, but without correction for pointing changes, is best for frequency analysis of this star, and, by implication, other RR Lyr stars observed by the K2 mission. We compare several pipeline reductions of the K2 mission data for this star....

  17. Chemical abundances and physical parameters of RR Lyrae stars

    International Nuclear Information System (INIS)

    Manduca, A.

    1980-01-01

    A grid of model stellar atmospheres has been calculated with a range of physical parameters which effectively cover RR Lyrae stars over all phases of their pulsation cycle. The models, calculated with the computer program MARCS, are flux-constant and include the effects of convection and line blanketing. Synthetic spectra were calculated for these models from 3000 A to 9600 A at 0.1 A resolution using the computer program SSG. These spectra were used directly in the applications below and were also used to computer theoretical colors on the UBVR, Stromgren uvby, and Walraven systems for the models. The uvby colors were used in determinations of effective temperature and surface gravity from photometry by various observers. The models, synthetic spectra, and colors were then applied to the problems detailed below. The data collected by Freeman and Rodgers (1975) for 25 RR Lyrae stars in ω Cen was reanalyzed with an alternative, synthetic spectrum approach to the calibration of their theoretical relations. The results confirm a wide range in calcium abundance for the stars in the cluster but at much lower values than reported by Freeman and Rodgers: a range of [Ca/H] = -1.0 to -1.9 was found. A theoretical calibration was performed for the ΔS system of determining metal abundances for RR Lyrae stars. The results support the existing empirical calibration of Butler in the range [Fe/H] = -0.6 to -2.2 and indicate how the calibration should be extrapolated to even lower metal abundances. For higher metal abundances, however, our calibration yields [Fe/H] values lower than Butler by as much as 0.4. Possible explanations of this discrepancy are investigated and the implications are discussed

  18. VizieR Online Data Catalog: Mid-infrared study of RR Lyrae stars (Gavrilchenko+, 2014)

    Science.gov (United States)

    Gavrilchenko, T.; Klein, C. R.; Bloom, J. S.; Richards, J. W.

    2015-02-01

    The first goal was to find a large sample of WISE-observed RR Lyrae stars. A data base of previously identified RR Lyrae stars was created, combining information from General Catalogue of Variable Stars (GCVS), All Sky Automated Survey (ASAS), SIMBAD, VizieR, and individual papers. For many of the sources in this data base the only available data were the coordinates and RR Lyrae classification. When provided, information about the period, distance, subclass, and magnitude for several different wavebands was also stored. If a single source appeared in multiple surveys or papers, information from all relevant surveys was included, with markers indicating contradicting measurements between surveys. The resulting data base contains about 17000 sources, of which about 5000 sources have documented V-band periods. (3 data files).

  19. Reddening and blanketing of RR-Lyrae stars, ch. 3

    International Nuclear Information System (INIS)

    Lub, J.

    1977-01-01

    The effects of metal line blanketing and interstellar reddening upon the colours of the RR-Lyrae Stars are discussed. Due to the faintness of these stars in the ultraviolet W channel (at lambda 3720 A) the photometry is in most cases reduced to a four-colour VBLU photometry, i.e. there are only three colour indices available for the determination of the four quantities: interstellar reddening, effective temperature, atmospheric pressure (or effective gravity), and metal line strength which determine the energy distribution that was measured

  20. Extended Aperture Photometry of K2 RR Lyrae stars

    Science.gov (United States)

    Plachy, Emese; Klagyivik, Péter; Molnár, László; Sódor, Ádám; Szabó, Róbert

    2017-10-01

    We present the method of the Extended Aperture Photometry (EAP) that we applied on K2 RR Lyrae stars. Our aim is to minimize the instrumental variations of attitude control maneuvers by using apertures that cover the positional changes in the field of view thus contain the stars during the whole observation. We present example light curves that we compared to the light curves from the K2 Systematics Correction (K2SC) pipeline applied on the automated Single Aperture Photometry (SAP) and on the Pre-search Data Conditioning Simple Aperture Photometry (PDCSAP) data.

  1. DISTANCE SCALE ZERO POINTS FROM GALACTIC RR LYRAE STAR PARALLAXES

    Energy Technology Data Exchange (ETDEWEB)

    Benedict, G. Fritz; McArthur, Barbara E.; Barnes, Thomas G. [McDonald Observatory, University of Texas, Austin, TX 78712 (United States); Feast, Michael W. [Centre for Astrophysics, Cosmology and Gravitation, Astronomy Department, University of Cape Town, Rondebosch 7701 (South Africa); Harrison, Thomas E. [Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States); Bean, Jacob L.; Kolenberg, Katrien [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Menzies, John W.; Laney, C. D. [South African Astronomical Observatory, Observatory 7935 (South Africa); Chaboyer, Brian [Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755 (United States); Fossati, Luca [Department of Physics and Astronomy, Open University, Milton Keynes MK7 6AA (United Kingdom); Nesvacil, Nicole [Institute of Astronomy, University of Vienna, A-1180 Vienna (Austria); Smith, Horace A. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Kochukhov, Oleg [Department of Physics and Astronomy, Uppsala University, 75120 Uppsala (Sweden); Nelan, Edmund P.; Taylor, Denise [STScI, Baltimore, MD 21218 (United States); Shulyak, D. V. [Institute of Astrophysics, Georg-August-University, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany); Freedman, Wendy L. [The Observatories, Carnegie Institution of Washington, Pasadena, CA 91101 (United States)

    2011-12-15

    We present new absolute trigonometric parallaxes and proper motions for seven Population II variable stars-five RR Lyr variables: RZ Cep, XZ Cyg, SU Dra, RR Lyr, and UV Oct; and two type 2 Cepheids: VY Pyx and {kappa} Pav. We obtained these results with astrometric data from Fine Guidance Sensors, white-light interferometers on Hubble Space Telescope. We find absolute parallaxes in milliseconds of arc: RZ Cep, 2.12 {+-} 0.16 mas; XZ Cyg, 1.67 {+-} 0.17 mas; SU Dra, 1.42 {+-} 0.16 mas; RR Lyr, 3.77 {+-} 0.13 mas; UV Oct, 1.71 {+-} 0.10 mas; VY Pyx, 6.44 {+-} 0.23 mas; and {kappa} Pav, 5.57 {+-} 0.28 mas; an average {sigma}{sub {pi}}/{pi} = 5.4%. With these parallaxes, we compute absolute magnitudes in V and K bandpasses corrected for interstellar extinction and Lutz-Kelker-Hanson bias. Using these RR Lyrae variable star absolute magnitudes, we then derive zero points for M{sub V} -[Fe/H] and M{sub K} -[Fe/H]-log P relations. The technique of reduced parallaxes corroborates these results. We employ our new results to determine distances and ages of several Galactic globular clusters and the distance of the Large Magellanic Cloud. The latter is close to that previously derived from Classical Cepheids uncorrected for any metallicity effect, indicating that any such effect is small. We also discuss the somewhat puzzling results obtained for our two type 2 Cepheids.

  2. Extended Aperture Photometry of K2 RR Lyrae stars

    Directory of Open Access Journals (Sweden)

    Plachy Emese

    2017-01-01

    Full Text Available We present the method of the Extended Aperture Photometry (EAP that we applied on K2 RR Lyrae stars. Our aim is to minimize the instrumental variations of attitude control maneuvers by using apertures that cover the positional changes in the field of view thus contain the stars during the whole observation. We present example light curves that we compared to the light curves from the K2 Systematics Correction (K2SC pipeline applied on the automated Single Aperture Photometry (SAP and on the Pre-search Data Conditioning Simple Aperture Photometry (PDCSAP data.

  3. 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.

  4. Machine-learned Identification of RR Lyrae Stars from Sparse, Multi-band Data: The PS1 Sample

    Science.gov (United States)

    Sesar, Branimir; Hernitschek, Nina; Mitrović, Sandra; Ivezić, Željko; Rix, Hans-Walter; Cohen, Judith G.; Bernard, Edouard J.; Grebel, Eva K.; Martin, Nicolas F.; Schlafly, Edward F.; Burgett, William S.; Draper, Peter W.; Flewelling, Heather; Kaiser, Nick; Kudritzki, Rolf P.; Magnier, Eugene A.; Metcalfe, Nigel; Tonry, John L.; Waters, Christopher

    2017-05-01

    RR Lyrae stars may be the best practical tracers of Galactic halo (sub-)structure and kinematics. The PanSTARRS1 (PS1) 3π survey offers multi-band, multi-epoch, precise photometry across much of the sky, but a robust identification of RR Lyrae stars in this data set poses a challenge, given PS1's sparse, asynchronous multi-band light curves (≲ 12 epochs in each of five bands, taken over a 4.5 year period). We present a novel template fitting technique that uses well-defined and physically motivated multi-band light curves of RR Lyrae stars, and demonstrate that we get accurate period estimates, precise to 2 s in > 80 % of cases. We augment these light-curve fits with other features from photometric time-series and provide them to progressively more detailed machine-learned classification models. From these models, we are able to select the widest (three-fourths of the sky) and deepest (reaching 120 kpc) sample of RR Lyrae stars to date. The PS1 sample of ˜45,000 RRab stars is pure (90%) and complete (80% at 80 kpc) at high galactic latitudes. It also provides distances that are precise to 3%, measured with newly derived period-luminosity relations for optical/near-infrared PS1 bands. With the addition of proper motions from Gaia and radial velocity measurements from multi-object spectroscopic surveys, we expect the PS1 sample of RR Lyrae stars to become the premier source for studying the structure, kinematics, and the gravitational potential of the Galactic halo. The techniques presented in this study should translate well to other sparse, multi-band data sets, such as those produced by the Dark Energy Survey and the upcoming Large Synoptic Survey Telescope Galactic plane sub-survey.

  5. Ground-based photometry for 42 Kepler-field RR Lyrae stars

    Science.gov (United States)

    Jeon, Young-Beom; Ngeow, Chow-Choong; Nemec, James M.

    2014-02-01

    Follow-up (U)BVRI photometric observations have been carried out for 42 RR Lyrae stars in the Kepler field. The new magnitude and color information will complement the available extensive high-precision Kepler photometry and recent spectroscopic results. The photometric observations were made with the following telescopes: 1-m and 41-cm telescopes of Lulin Observatory (Taiwan), 81-cm telescope of Tenagra Observatory (Arizona, USA), 1-m telescope at the Mt. Lemmon Optical Astronomy Observatory (LOAO, Arizona, USA), 1.8-m and 15-cm telescopes at the Bohyunsan Optical Astronomy Observatory (BOAO, Korea) and 61-cm telescope at the Sobaeksan Optical Astronomy Observatory (SOAO, Korea). The observations span from 2010 to 2013, with ~200 to ~600 data points per light curve. Preliminary results of the Korean observations were presented at the 5th KASC workshop in Hungary. In this work, we analyze all observations. These observations permit the construction of full light curves for these RR Lyrae stars and can be used to derive multi-filter Fourier parameters.

  6. DISCOVERY OF RR LYRAE STARS IN THE NUCLEAR BULGE OF THE MILKY WAY

    Energy Technology Data Exchange (ETDEWEB)

    Minniti, Dante; Ramos, Rodrigo Contreras; Zoccali, Manuela; Gran, Felipe [Instituto Milenio de Astrofisica, Santiago (Chile); Rejkuba, Marina; Valenti, Elena [European Southern Observatory, Karl-Schwarszchild-Str. 2, D-85748 Garching bei Muenchen (Germany); Gonzalez, Oscar A., E-mail: dante@astrofisica.cl, E-mail: rcontrer@astro.puc.cl [UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom)

    2016-10-10

    Galactic nuclei, such as that of the Milky Way, are extreme regions with high stellar densities, and in most cases, the hosts of a supermassive black hole. One of the scenarios proposed for the formation of the Galactic nucleus is merging of primordial globular clusters. An implication of this model is that this region should host stars that are characteristically found in old Milky Way globular clusters. RR Lyrae stars are primary distance indicators, well known representatives of old and metal-poor stellar populations, and therefore are regularly found in globular clusters. Here we report the discovery of a dozen RR Lyrae type ab stars in the vicinity of the Galactic center, i.e., in the so-called nuclear stellar bulge of the Milky Way. This discovery provides the first direct observational evidence that the Galactic nuclear stellar bulge contains ancient stars (>10 Gyr old). Based on this we conclude that merging globular clusters likely contributed to the build-up of the high stellar density in the nuclear stellar bulge of the Milky Way.

  7. VizieR Online Data Catalog: Abundances of 8 RR Lyrae subclass C variable stars (Govea+, 2014)

    Science.gov (United States)

    Govea, J.; Gomez, T.; Preston, G. W.; Sneden, C.

    2016-02-01

    We chose 10 candidate RR Lyrae variable stars of subclass c (RRc) stars for spectroscopic observation. Many of these stars were first identified as RRc variables by the All Sky Automated Survey (ASAS) of Pojmanski 2003 (cat. II/264). The target star list included ASAS 144154-0324.7 and ASAS 204440-2402.7. But our spectroscopic study suggest that these two stars are probably W UMa binaries instead of RR Lyrae stars Our spectra were obtained with the echelle spectrograph of the du Pont 2.5m telescope at the Las Campanas Observatory. Four observing runs during 2009-2010 were partly devoted to this project. The spectrograph was used with the 1.5*4'' entrance slit, which translates to a resolving power of R=λ/Δλ~27000 at the MgI b lines near 5180Å. The total continuous wavelength coverage of the spectra was 3500-9000Å. (6 data files).

  8. Nonlinear Convective Models of RR Lyrae Stars

    Science.gov (United States)

    Feuchtinger, M.; Dorfi, E. A.

    The nonlinear behavior of RR Lyrae pulsations is investigated using a state-of-the-art numerical technique solving the full time-dependent system of radiation hydrodynamics. Grey radiative transfer is included by a variable Eddington-factor method and we use the time-dependent turbulent convection model according to Kuhfuss (1986, A&A 160, 116) in the version of Wuchterl (1995, Comp. Phys. Comm. 89, 19). OPAL opacities extended by the Alexander molecule opacities at temperatures below 6000 K and an equation of state according to Wuchterl (1990, A&A 238, 83) close the system. The resulting nonlinear system is discretized on an adaptive mesh developed by Dorfi & Drury (1987, J. Comp. Phys. 69, 175), which is important to provide the necessary spatial resolution in critical regions like ionization zones and shock waves. Additionally, we employ a second order advection scheme, a time centered temporal discretizaton and an artificial tensor viscosity in order to treat discontinuities. We compute fundamental as well first overtone models of RR Lyrae stars for a grid of stellar parameters both with and without convective energy transport in order to give a detailed picture of the pulsation-convection interaction. In order to investigate the influence of the different features of the convection model calculations with and without overshooting, turbulent pressure and turbulent viscosity are performed and compared with each other. A standard Fourier decomposition is used to confront the resulting light and radial velocity variations with recent observations and we show that the well known RR Lyrae phase discrepancy problem (Simon 1985, ApJ 299, 723) can be resolved with these stellar pulsation computations.

  9. Exploring the Milky Way halo with SDSS-II SN survey RR Lyrae stars

    Science.gov (United States)

    De Lee, Nathan

    This thesis details the creation of a large catalog of RR Lyrae stars, their lightcurves, and their associated photometric and kinematic parameters. This catalog contains 421 RR Lyrae stars with 305 RRab and 116 RRc. Of these, 241 stars have stellar spectra taken with either the Blanco 4m RC spectrograph or the SDSS/SEGUE survey, and in some cases taken by both. From these spectra and photometric methods derived from them, an analysis is conducted of the RR lyrae's distribution, metallicity, kinematics, and photometric properties within the halo. All of these RR Lyrae originate from the SDSS-II Supernova Survey. The SDSS-II SN Survey covers a 2.5 degree equatorial stripe ranging from -60 to +60 degrees in RA. This corresponds to relatively high southern galactic latitudes in the anti-center direction. The full catalog ranges from g 0 magnitude 13 to 20 which covers a distance of 3 to 95 kpc from the sun. Using this sample, we explore the Oosterhoff dichotomy through the D log P method as a function of | Z | distance from the plane. This results in a clear division of the RRab stars into OoI and OoII groups at lower | Z |, but the population becomes dominated by OoI stars at higher | Z |. The idea of a dual halo is explored primarily in the context of radial velocity distributions as a function of | Z |. In particular, V gsr , the radial velocity in the galactic standard of rest, is used as a proxy for V [straight phi] , the cylindrical rotational velocity. This is then compared against a single halo model galaxy, which results in very similar V gsr histograms for both at low to medium | Z |. However, at high | Z | there is a clear separation into two distinct velocity groups for the data without a corresponding separation in the model, suggesting that at least a two-component model for the halo is necessary. The final part of the analysis involves [Fe/H] measurements from both spectra and photometric relations cut in both | Z | and radial velocity. In this case

  10. RR Lyrae stars in and around NGC 6441: signatures of dissolving cluster stars

    Science.gov (United States)

    Kunder, Andrea

    2018-06-01

    Detailed elemental abundance patterns of metal-poor ([Fe/H]~ -1 dex) stars in the Galactic bulge indicate that a number of them are consistent with globular cluster (GC) stars and may be former members of dissolved GCs. This would indicate that a few per cent of the Galactic bulge was built up from destruction and/or evaporation of globular clusters. Here an attempt is made to identify such presumptive destroyed stars originating from the massive, inner Galaxy globular cluster NGC~6441 using its rich RR Lyrae variable star (RRL) population. We present radial velocities of forty RRLs centered on the globular cluster NGC~6441. All of the 13 RRLs observed within the cluster tidal radius have velocities consistent with cluster membership, with an average radial velocity of 24 +- 5~km/s and a star-to-star scatter of 11~km/s. This includes two new RRLs that were previously not associated with the cluster. Eight RRLs with radial velocities consistent with cluster membership but up to three time the distance from the tidal radius are also reported. These potential extra-tidal RRLs also have exceptionally long periods, which is a curious characteristic of the NGC~6441 RRL population that hosts RRLs with periods longer than seen anywhere else in the Milky Way. As expected of stripped cluster stars, most are inline with the cluster's orbit. Therefore, either the tidal radius of NGC~6441 is underestimated and/or we are seeing dissolving cluster stars stemming from NGC~6441 that are building up the old spheroidal bulge. Both the mean velocity of the cluster as well as the underlying field population is consistent with belonging to an old spheroidal bulge with low rotation and high velocity dispersion that formed before the bar.

  11. Metal-rich RRc Stars in the Carnegie RR Lyrae Survey

    Science.gov (United States)

    Sneden, Christopher; Preston, George W.; Kollmeier, Juna A.; Crane, Jeffrey D.; Morrell, Nidia; Prieto, José L.; Shectman, Stephen A.; Skowron, Dorota M.; Thompson, Ian B.

    2018-01-01

    We describe and employ a stacking procedure to investigate abundances derived from the low signal-to-noise ratio spectra obtained in the Carnegie RR Lyrae Survey (CARRS). We find iron metallicities that extend from [Fe/H] ∼ ‑2.5 to values at least as large as [Fe/H] ∼ ‑0.5 in the 274-spectrum CARRS RRc data set. We consider RRc sample contamination by high amplitude solar metallicity δ Scuti stars (HADS) at periods less than 0.3 days, where photometric discrimination between RRc and δ Scuti stars has proven to be problematic. We offer a spectroscopic discriminant, the well-marked overabundance of heavy elements, principally [Ba/H], that is a common, if not universal, characteristic of HADS of all periods and axial rotations. No bona fide RRc stars known to us have verified heavy-element overabundances. Three out of 34 stars in our sample with [Fe/H] > ‑0.7 exhibit anomalously strong features of Sr, Y, Zr, Ba, and many rare earths. However, carbon is not enhanced in these three stars, and we conclude that their elevated n-capture abundances have not been generated in interior neutron-capture nucleosynthesis. Contamination by HADS appears to be unimportant, and metal-rich RRc stars occur in approximately the same proportion in the Galactic field as do metal-rich RRab stars. An apparent dearth of metal-rich RRc is probably a statistical fluke. Finally, we show that RRc stars have a similar inverse period–metallicity relationship as has been found for RRab stars.

  12. Gaia’s Cepheids and RR Lyrae stars and luminosity calibrations based on Tycho-Gaia Astrometric Solution

    Directory of Open Access Journals (Sweden)

    Clementini Gisella

    2017-01-01

    Full Text Available Gaia Data Release 1 contains parallaxes for more than 700 Galactic Cepheids and RR Lyrae stars, computed as part of the Tycho-Gaia Astrometric Solution (TGAS. We have used TGAS parallaxes, along with literature (V, I, J, Ks, W1 photometry and spectroscopy, to calibrate the zero point of the period-luminosity and period-Wesenheit relations of classical and type II Cepheids, and the near-infrared period-luminosity, period-luminosity-metallicity and optical luminosity-metallicity relations of RR Lyrae stars. In this contribution we briefly summarise results obtained by fitting these basic relations adopting different techniques that operate either in parallax or distance (absolute magnitude space.

  13. CCD time-series photometry of the globular cluster NGC 5053: RR Lyrae, Blue Stragglers and SX Phoenicis stars revisited

    Science.gov (United States)

    Arellano Ferro, A.; Giridhar, Sunetra; Bramich, D. M.

    2010-02-01

    We report the results of CCD V, r and I time-series photometry of the globular cluster NGC 5053. New times of maximum light are given for the eight known RR Lyrae stars in the field of our images, and their periods are revised. Their V light curves were Fourier decomposed to estimate their physical parameters. A discussion on the accuracy of the Fourier-based iron abundances, temperatures, masses and radii is given. New periods are found for the five known SX Phe stars, and a critical discussion of their secular period changes is offered. The mean iron abundance for the RR Lyrae stars is found to be [Fe/H] ~ -1.97 +/- 0.16 and lower values are not supported by the present analysis. The absolute magnitude calibrations of the RR Lyrae stars yield an average true distance modulus of 16.12 +/- 0.04 or a distance of 16.7 +/- 0.3 kpc. Comparison of the observational colour magnitude diagram (CMD) with theoretical isochrones indicates an age of 12.5 +/- 2.0 Gyr for the cluster. A careful identification of all reported blue stragglers (BS) and their V, I magnitudes leads to the conclusion that BS12, BS22, BS23 and BS24 are not BS. On the other hand, three new BS are reported. Variability was found in seven BS, very likely of the SX Phe type in five of them, and in one red giant star. The new SX Phe stars follow established Period-Luminosity relationships and indicate a distance in agreement with the distance from the RR Lyrae stars. Based on observations collected at the Indian Astrophysical Observatory, Hanle, India. E-mail: armando@astroscu.unam.mx (AAF); giridhar@iiap.res.in (SG); dan.bramich@hotmail.co.uk (DMB)

  14. Gaia Data Release 1. Testing parallaxes with local Cepheids and RR Lyrae stars

    NARCIS (Netherlands)

    Gaia Collaboration, [Unknown; Clementini, G.; Eyer, L.; Ripepi, V.; Marconi, M.; Muraveva, T.; Garofalo, A.; Sarro, L. M.; Palmer, M.; Luri, X.; Molinaro, R.; Rimoldini, L.; Szabados, L.; Musella, I.; Anderson, R. I.; Prusti, T.; de Bruijne, J. H. J.; Brown, A. G. A.; Vallenari, A.; Babusiaux, C.; Bailer-Jones, C. A. L.; Bastian, U.; Biermann, M.; Evans, D. W.; Jansen, F.; Jordi, C.; Klioner, S. A.; Lammers, U.; Lindegren, L.; Mignard, F.; Panem, C.; Pourbaix, D.; Randich, S.; Sartoretti, P.; Siddiqui, H. I.; Soubiran, C.; Valette, V.; van Leeuwen, F.; Walton, N. A.; Aerts, C.; Arenou, F.; Cropper, M.; Drimmel, R.; Høg, E.; Katz, D.; Lattanzi, M. G.; O'Mullane, W.; Grebel, E. K.; Holland, A. D.; Huc, C.; Passot, X.; Perryman, M.; Bramante, L.; Cacciari, C.; Castañeda, J.; Chaoul, L.; Cheek, N.; De Angeli, F.; Fabricius, C.; Guerra, R.; Hernández, J.; Jean-Antoine-Piccolo, A.; Masana, E.; Messineo, R.; Mowlavi, N.; Nienartowicz, K.; Ordóñez-Blanco, D.; Panuzzo, P.; Portell, J.; Richards, P. J.; Riello, M.; Seabroke, G. M.; Tanga, P.; Thévenin, F.; Torra, J.; Els, S. G.; Gracia-Abril, G.; Comoretto, G.; Garcia-Reinaldos, M.; Lock, T.; Mercier, E.; Altmann, M.; Andrae, R.; Astraatmadja, T. L.; Bellas-Velidis, I.; Benson, K.; Berthier, J.; Blomme, R.; Busso, G.; Carry, B.; Cellino, A.; Cowell, S.; Creevey, O.; Cuypers, J.; Davidson, M.; De Ridder, J.; de Torres, A.; Delchambre, L.; Dell'Oro, A.; Ducourant, C.; Frémat, Y.; García-Torres, M.; Gosset, E.; Halbwachs, J.-L.; Hambly, N. C.; Harrison, D. L.; Hauser, M.; Hestroffer, D.; Hodgkin, S. T.; Huckle, H. E.; Hutton, A.; Jasniewicz, G.; Jordan, S.; Kontizas, M.; Korn, A. J.; Lanzafame, A. C.; Manteiga, M.; Moitinho, A.; Muinonen, K.; Osinde, J.; Pancino, E.; Pauwels, T.; Petit, J.-M.; Recio-Blanco, A.; Robin, A. C.; Siopis, C.; Smith, M.; Smith, K. W.; Sozzetti, A.; Thuillot, W.; van Reeven, W.; Viala, Y.; Abbas, U.; Abreu Aramburu, A.; Accart, S.; Aguado, J. J.; Allan, P. M.; Allasia, W.; Altavilla, G.; Álvarez, M. A.; Alves, J.; Andrei, A. H.; Anglada Varela, E.; Antiche, E.; Antoja, T.; Antón, S.; Arcay, B.; Bach, N.; Baker, S. G.; Balaguer-Núñez, L.; Barache, C.; Barata, C.; Barbier, A.; Barblan, F.; Barrado y Navascués, D.; Barros, M.; Barstow, M. A.; Becciani, U.; Bellazzini, M.; Bello García, A.; Belokurov, V.; Bendjoya, P.; Berihuete, A.; Bianchi, L.; Bienaymé, O.; Billebaud, F.; Blagorodnova, N.; Blanco-Cuaresma, S.; Boch, T.; Bombrun, A.; Borrachero, R.; Bouquillon, S.; Bourda, G.; Bragaglia, A.; Breddels, M. A.; Brouillet, N.; Brüsemeister, T.; Bucciarelli, B.; Burgess, P.; Burgon, R.; Burlacu, A.; Busonero, D.; Buzzi, R.; Caffau, E.; Cambras, J.; Campbell, H.; Cancelliere, R.; Cantat-Gaudin, T.; Carlucci, T.; Carrasco, J. M.; Castellani, M.; Charlot, P.; Charnas, J.; Chiavassa, A.; Clotet, M.; Cocozza, G.; Collins, R. S.; Costigan, G.; Crifo, F.; Cross, N. J. G.; Crosta, M.; Crowley, C.; Dafonte, C.; Damerdji, Y.; Dapergolas, A.; David, P.; David, M.; De Cat, P.; de Felice, F.; de Laverny, P.; De Luise, F.; De March, R.; de Souza, R.; Debosscher, J.; del Pozo, E.; Delbo, M.; Delgado, A.; Delgado, H. E.; Di Matteo, P.; Diakite, S.; Distefano, E.; Dolding, C.; Dos Anjos, S.; Drazinos, P.; Durán, J.; Dzigan, Y.; Edvardsson, B.; Enke, H.; Evans, N. W.; Eynard Bontemps, G.; Fabre, C.; Fabrizio, M.; Falcão, A. J.; Farràs Casas, M.; Federici, L.; Fedorets, G.; Fernández-Hernández, J.; Fernique, P.; Fienga, A.; Figueras, F.; Filippi, F.; Findeisen, K.; Fonti, A.; Fouesneau, M.; Fraile, E.; Fraser, M.; Fuchs, J.; Gai, M.; Galleti, S.; Galluccio, L.; Garabato, D.; García-Sedano, F.; Garralda, N.; Gavras, P.; Gerssen, J.; Geyer, R.; Gilmore, G.; Girona, S.; Giuffrida, G.; Gomes, M.; González-Marcos, A.; González-Núñez, J.; González-Vidal, J. J.; Granvik, M.; Guerrier, A.; Guillout, P.; Guiraud, J.; Gúrpide, A.; Gutiérrez-Sánchez, R.; Guy, L. P.; Haigron, R.; Hatzidimitriou, D.; Haywood, M.; Heiter, U.; Helmi, A.; Hobbs, D.; Hofmann, W.; Holl, B.; Holland, G.; Hunt, J. A. S.; Hypki, A.; Icardi, V.; Irwin, M.; Jevardat de Fombelle, G.; Jofré, P.; Jonker, P. G.; Jorissen, A.; Julbe, F.; Karampelas, A.; Kochoska, A.; Kohley, R.; Kolenberg, K.; Kontizas, E.; Koposov, S. E.; Kordopatis, G.; Koubsky, P.; Krone-Martins, A.; Kudryashova, M.; Bachchan, R. K.; Lacoste-Seris, F.; Lanza, A. F.; Lavigne, J.-B.; Le Poncin-Lafitte, C.; Lebreton, Y.; Lebzelter, T.; Leccia, S.; Leclerc, N.; Lecoeur-Taibi, I.; Lemaitre, V.; Lenhardt, H.; Leroux, F.; Liao, S.; Licata, E.; Lindstrøm, H. E. P.; Lister, T. A.; Livanou, E.; Lobel, A.; Löffler, W.; López, M.; Lorenz, D.; MacDonald, I.; Magalhães Fernandes, T.; Managau, S.; Mann, R. G.; Mantelet, G.; Marchal, O.; Marchant, J. M.; Marinoni, S.; Marrese, P. M.; Marschalkó, G.; Marshall, D. J.; Martín-Fleitas, J. M.; Martino, M.; Mary, N.; Matijevič, G.; McMillan, P. J.; Messina, S.; Michalik, D.; Millar, N. R.; Miranda, B. M. H.; Molina, D.; Molinaro, M.; Molnár, L.; Moniez, M.; Montegriffo, P.; Mor, R.; Mora, A.; Morbidelli, R.; Morel, T.; Morgenthaler, S.; Morris, D.; Mulone, A. F.; Narbonne, J.; Nelemans, G.; Nicastro, L.; Noval, L.; Ordénovic, C.; Ordieres-Meré, J.; Osborne, P.; Pagani, C.; Pagano, I.; Pailler, F.; Palacin, H.; Palaversa, L.; Parsons, P.; Pecoraro, M.; Pedrosa, R.; Pentikäinen, H.; Pichon, B.; Piersimoni, A. M.; Pineau, F.-X.; Plachy, E.; Plum, G.; Poujoulet, E.; Prša, A.; Pulone, L.; Ragaini, S.; Rago, S.; Rambaux, N.; Ramos-Lerate, M.; Ranalli, P.; Rauw, G.; Read, A.; Regibo, S.; Reylé, C.; Ribeiro, R. A.; Riva, A.; Rixon, G.; Roelens, M.; Romero-Gómez, M.; Rowell, N.; Royer, F.; Ruiz-Dern, L.; Sadowski, G.; Sagristà Sellés, T.; Sahlmann, J.; Salgado, J.; Salguero, E.; Sarasso, M.; Savietto, H.; Schultheis, M.; Sciacca, E.; Segol, M.; Segovia, J. C.; Segransan, D.; Shih, I.-C.; Smareglia, R.; Smart, R. L.; Solano, E.; Solitro, F.; Sordo, R.; Soria Nieto, S.; Souchay, J.; Spagna, A.; Spoto, F.; Stampa, U.; Steele, I. A.; Steidelmüller, H.; Stephenson, C. A.; Stoev, H.; Suess, F. F.; Süveges, M.; Surdej, J.; Szegedi-Elek, E.; Tapiador, D.; Taris, F.; Tauran, G.; Taylor, M. B.; Teixeira, R.; Terrett, D.; Tingley, B.; Trager, S. C.; Turon, C.; Ulla, A.; Utrilla, E.; Valentini, G.; van Elteren, A.; Van Hemelryck, E.; van Leeuwen, M.; Varadi, M.; Vecchiato, A.; Veljanoski, J.; Via, T.; Vicente, D.; Vogt, S.; Voss, H.; Votruba, V.; Voutsinas, S.; Walmsley, G.; Weiler, M.; Weingrill, K.; Wevers, T.; Wyrzykowski, Ł.; Yoldas, A.; Žerjal, M.; Zucker, S.; Zurbach, C.; Zwitter, T.; Alecu, A.; Allen, M.; Allende Prieto, C.; Amorim, A.; Anglada-Escudé, G.; Arsenijevic, V.; Azaz, S.; Balm, P.; Beck, M.; Bernstein, H.-H.; Bigot, L.; Bijaoui, A.; Blasco, C.; Bonfigli, M.; Bono, G.; Boudreault, S.; Bressan, A.; Brown, S.; Brunet, P.-M.; Bunclark†, P.; Buonanno, R.; Butkevich, A. G.; Carret, C.; Carrion, C.; Chemin, L.; Chéreau, F.; Corcione, L.; Darmigny, E.; de Boer, K. S.; de Teodoro, P.; de Zeeuw, P. T.; Delle Luche, C.; Domingues, C. D.; Dubath, P.; Fodor, F.; Frézouls, B.; Fries, A.; Fustes, D.; Fyfe, D.; Gallardo, E.; Gallegos, J.; Gardiol, D.; Gebran, M.; Gomboc, A.; Gómez, A.; Grux, E.; Gueguen, A.; Heyrovsky, A.; Hoar, J.; Iannicola, G.; Isasi Parache, Y.; Janotto, A.-M.; Joliet, E.; Jonckheere, A.; Keil, R.; Kim, D.-W.; Klagyivik, P.; Klar, J.; Knude, J.; Kochukhov, O.; Kolka, I.; Kos, J.; Kutka, A.; Lainey, V.; LeBouquin, D.; Liu, C.; Loreggia, D.; Makarov, V. V.; Marseille, M. G.; Martayan, C.; Martinez-Rubi, O.; Massart, B.; Meynadier, F.; Mignot, S.; Munari, U.; Nguyen, A.-T.; Nordlander, T.; O'Flaherty, K. S.; Ocvirk, P.; Olias Sanz, A.; Ortiz, P.; Osorio, J.; Oszkiewicz, D.; Ouzounis, A.; Park, P.; Pasquato, E.; Peltzer, C.; Peralta, J.; Péturaud, F.; Pieniluoma, T.; Pigozzi, E.; Poels†, J.; Prat, G.; Prod'homme, T.; Raison, F.; Rebordao, J. M.; Risquez, D.; Rocca-Volmerange, B.; Rosen, S.; Ruiz-Fuertes, M. I.; Russo, F.; Serraller Vizcaino, I.; Short, A.; Siebert, A.; Silva, H.; Sinachopoulos, D.; Slezak, E.; Soffel, M.; Sosnowska, D.; Straižys, V.; ter Linden, M.; Terrell, D.; Theil, S.; Tiede, C.; Troisi, L.; Tsalmantza, P.; Tur, D.; Vaccari, M.; Vachier, F.; Valles, P.; Van Hamme, W.; Veltz, L.; Virtanen, J.; Wallut, J.-M.; Wichmann, R.; Wilkinson, M. I.; Ziaeepour, H.; Zschocke, S.

    2017-01-01

    Context. Parallaxes for 331 classical Cepheids, 31 Type II Cepheids, and 364 RR Lyrae stars in common between Gaia and the Hipparcos and Tycho-2 catalogues are published in Gaia Data Release 1 (DR1) as part of the Tycho-Gaia Astrometric Solution (TGAS). Aims: In order to test these first parallax

  15. Macho project photometry of RR Lyrae stars in the Sagittarius dwarf galaxy

    Energy Technology Data Exchange (ETDEWEB)

    Alcock, C. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)]|[Center for Particle Astrophysics, University of California, Berkeley, California 94720 (United States); Allsman, R.A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)]|[Mount Stromlo and Siding Spring Observatories, Australian National University, Weston, ACT 2611 (Australia); Alves, D.R. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)]|[Department of Physics, University of California, Davis, California 95616 (United States); Axelrod, T.S. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)]|[Mount Stromlo and Siding Spring Observatories, Australian National University, Weston, ACT 2611 (Australia); Becker, A.C. [Center for Particle Astrophysics, University of California, Berkeley, California 94720 (United States)]|[Department of Astronomy, University of Washington, Seattle, Washington 98195 (United States); Bennett, D.P.; Cook, K.H. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)]|[Center for Particle Astrophysics, University of California, Berkeley, California 94720 (United States); Freeman, K.C. [Mount Stromlo and Siding Spring Observatories, Australian National University, Weston, ACT 2611 (Australia); Griest, K. [Center for Particle Astrophysics, University of California, Berkeley, California 94720 (United States)]|[Department of Physics, University of California, San Diego, California 92093 (United States); Guern, J.A.; Lehner, M.J. [Department of Physics, University of California, San Diego, California 92093 (United States); Marshall, S.L.; Minniti, D. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Peterson, B.A. [Mount Stromlo and Siding Spring Observatories, Australian National University, Weston, ACT 2611 (Australia); Pratt, M.R.

    1997-01-01

    We report the discovery of 30 type a, b RR Lyrae (RRab) stars that are likely members of the Sagittarius dwarf galaxy (Sgr). Accurate positions, periods, amplitudes, and magnitudes are presented. Their distances are determined with respect to RRab stars in the Galactic bulge found also in the MACHO 1993 data. For R{sub {circle_dot}}=8kpc, the mean distance to these stars is D=22{plus_minus}1kpc, smaller than previous determinations for this galaxy. This indicates that Sgr has an elongated main body extending for more than 10 kpc, which is inclined along the line of sight, with its northern part (in Galactic coordinates) closer to us. The size and shape of Sgr give clues about the past history of this galaxy. If the shape of Sgr follows the direction of its orbit, the observed spatial orientation suggests that Sgr is moving away from the Galactic plane. Also, Sgr stars may be the sources of some of the microlensing events seen toward the bulge. {copyright} {ital 1997} {ital The American Astronomical Society}

  16. The ACS LCID project : RR Lyrae stars as tracers of old population gradients in the isolated dwarf spheroidal galaxy tucana

    NARCIS (Netherlands)

    Bernard, Edouard J.; Gallart, Carme; Monelli, Matteo; Aparicio, Antonio; Cassisi, Santi; Skillman, Evan D.; Stetson, Peter B.; Cole, Andrew A.; Drozdovsky, Igor; Hidalgo, Sebastian L.; Mateo, Mario; Tolstoy, Eline

    2008-01-01

    We present a study of the radial distribution of RR Lyrae variables, which present a range of photometric and pulsational properties, in the dwarf spheroidal galaxy Tucana. We find that the fainter RR Lyrae stars, having a shorter period, are more centrally concentrated than the more luminous,

  17. Identification and period investigation of pulsation variable star UY Camelopardalis, an RR Lyrae star in binary system

    Science.gov (United States)

    Li, Lin-Jia; Qian, Sheng-Bang; Voloshina, Irina; Metlov, Vladimir G.; Zhu, Li-Ying; Liao, Wen-Ping

    2018-06-01

    We present photometric measurements of the short period variable star UY Cam, which has been classified as a δ Scuti or c-type RR Lyrae (RRc) variable in different catalogs. Based on the analyses on Fourier coefficients and (NUV - V)0, we find that UY Cam is probably an RRc star. We obtain 58 new times of light maximum for UY Cam based on several sky surveys and our observations. Combining these with the times of light maximum in literature, a total of 154 times of light maximum are used to analyze the O - C diagram of UY Cam. The results show that the O - C pattern can be described by a downward parabolic component with a rate of -6.86 ± 0.47 × 10-11 d d-1, and a cyclic variation with a period of 65.7 ± 2.4 yr. We suppose these components are caused by the stellar evolution and the light travel time effect (LiTE) of a companion in elliptical orbit, respectively. By calculation, the minimum mass of the potential companion is about 0.17 M⊙, and its mass should be less than or equal to the pulsation primary star when the inclination i > 22.5°D. Therefore, the companion should be a low-mass star, like a late-type main-sequence star or a white dwarf. Due to the unique property of UY Cam, we suggest that more observations and studies on UY Cam and other RRc stars are needed to check the nature of these stars, including the pulsations and binarities.

  18. NONLINEAR ASTEROSEISMOLOGY OF RR LYRAE

    Energy Technology Data Exchange (ETDEWEB)

    Molnar, L.; Kollath, Z.; Szabo, R. [Konkoly Observatory, MTA CSFK, H-1121 Budapest, Konkoly Thege Miklos ut 15-17 (Hungary); Bryson, S.; Mullally, F.; Thompson, S. E. [NASA Ames Research Center, MS 244-30, Moffet Field, CA 94035 (United States); Kolenberg, K., E-mail: molnar.laszlo@csfk.mta.hu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138 (United States)

    2012-09-20

    The observations of the Kepler Space Telescope revealed that fundamental-mode RR Lyrae stars may show various radial overtones. The presence of multiple radial modes may allow us to conduct nonlinear asteroseismology: comparison of mode amplitudes and frequency shifts between observations and models. Here we report the detection of three radial modes in the star RR Lyr, the eponym of the class, using the Kepler short cadence data: besides the fundamental mode, both the first and the ninth overtones can be derived from the data set. RR Lyrae shows period doubling, but switches occasionally to a state where a pattern of six pulsation cycles repeats instead of two. We found hydrodynamic models that show the same three modes and the period-six state, allowing for comparison with the observations.

  19. Galactic archaeology for amateur astronomers: RR Lyrae stars as tracers of the Milky Way formation

    Science.gov (United States)

    Carballo-Bello, Julio A.; Martínez-Delgado, David; Fliri, Jürgen

    2011-06-01

    Cosmological models predict that large galaxies like the Milky Way formed from the accretion of smaller stellar systems. The most spectacular of these merger events are stellar tidal streams, rivers of stars and dark matter that envelop the discs of spiral galaxies. We present a research project for a collaboration with amateur astronomers in the study of the formation process of our Galaxy. The main objective is the search for RR Lyrae variable stars in the known stellar streams (Sagitarius, Monoceros, Orphan, etc) a project that can be carried out using small telescopes. The catalogue of candidate variable stars were selected from SDSS data based in colour criteria and it will be sent to interested amateur astronomers who wish to participate in scientific research in one of the most active and competitive topics in Galactic astronomy.

  20. THE RR LYRAE VARIABLES AND HORIZONTAL BRANCH OF NGC 6656 (M22) {sup ,}

    Energy Technology Data Exchange (ETDEWEB)

    Kunder, Andrea; Walker, Alistair R.; Paredes Alvarez, Leonardo [Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile); Stetson, Peter B. [Dominion Astrophysical Observatory, NRC-Herzberg, National Research Council, Victoria BC, V9E 2E7 (Canada); Cassisi, Santi [INAF-Osservatorio Astronomico di Collurania, Via M. Maggini, I-64100 Teramo (Italy); Layden, Andrew [Bowling Green State University, Bowling Green, OH 43403 (United States); Bono, Giuseppe [Dipartimento di Fisica, Universita di Roma Tor Vergata, Rome (Italy); Catelan, Márcio [Pontificia Universidad Católica de Chile, Departamento de Astronomía y Astrofísica, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago (Chile); Clem, James L. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States); Matsunaga, Noriyuki [Department of Astronomy, School of Science, The University of Tokyo (Japan); Salaris, Maurizio [Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD (United Kingdom); Lee, Jae-Woo [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Chaboyer, Brian, E-mail: akunder@ctio.noao.edu, E-mail: mcatelan@astro.puc.cl [Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755 (United States)

    2013-11-01

    The first calibrated broadband UBVI time-series photometry is presented for the RR Lyrae variable stars in NGC 6656 (M22), with observations spanning a range of 22 years. We have also redetermined the variability types and periods for the RR Lyrae stars identified previously by photographic observations, revising the number of fundamental-mode RR Lyrae variables (RR0) to 10 and the number of first-overtone variables (RR1) to 16. The mean periods of the RR0 and RR1 variables are (P) {sub RR0} = 0.66 ± 0.02 days and (P) {sub RR1} = 0.33 ± 0.01 days, respectively, supporting an Oosterhoff II classification for the cluster. The number ratio of RR1-type to all RR-type variables is N {sub 1}/N{sub RR} = 0.61, also consistent with an Oosterhoff II designation. Both the RR Lyrae stars' minimum light colors and the blue edge of the RR Lyrae instability strip suggest E( B – – V) = 0.36 ± 0.02 mag toward M22. Regarding the HB morphology of M22, we find (B-R)/(B+V+R) = +0.97 ± 0.1 and at least one ''gap'' located in an unusual part of the blue HB, in the middle of the so-called hot HB stars.

  1. Gaia Data Release 1. Testing the parallaxes with local Cepheids and RR Lyrae stars

    OpenAIRE

    Gaia Collaboration; Clementini, G.; Eyer, L.; Ripepi, V.; Marconi, M.; Muraveva, T.; Garofalo, A.; Sarro, L. M.; Palmer, M.; Luri, X.; Molinaro, R.; Rimoldini, L.; Szabados, L.; Musella, I.; Anderson, R. I.

    2017-01-01

    Context. Parallaxes for 331 classical Cepheids, 31 Type II Cepheids, and 364 RR Lyrae stars in common between Gaia and the HIPPARCOS and Tycho-2 catalogues are published in Gaia Data Release 1 (DR1) as part of the Tycho-Gaia Astrometric Solution (TGAS). Aims. In order to test these first parallax measurements of the primary standard candles of the cosmological distance ladder, which involve astrometry collected by Gaia during the initial 14 months of science operation, we compared them with l...

  2. La Silla quest RR Lyrae star survey: Region I

    International Nuclear Information System (INIS)

    Zinn, R.; Miller, L.; Horowitz, B.; Baltay, C.; Ellman, N.; Hadjiyska, E.; Rabinowitz, D.; Vivas, A. K.

    2014-01-01

    A search for RR Lyrae stars (RRLSs) in ∼840 deg 2 of the sky in right ascension 150°-210° and declination –10° to + 10° yielded 1013 type ab and 359 type c RRLS. This sample is used to study the density profile of the Galactic halo, halo substructures, and the Oosterhoff type of the halo over distances (d ☉ ) from ∼5 to ∼80 kpc. The halo is flattened toward the Galactic plane, and its density profile steepens in slope at galactocentric distances greater than ∼25 kpc. The RRLS in the stellar stream from the Sagittarius dwarf spheroidal (dSph) galaxy match well the model of Law and Majewski for the stars that were stripped 1.3-3.2 Gyr ago, but not for the ones stripped 3.2-5.0 Gyr ago. Over densities are found at the locations of the Virgo Overdensity and the Virgo Stellar Stream. Within 1° of 1220-1, which Jerjen et al. identify as a halo substructure at d ☉ ∼ 24 kpc, there are four RRLS that are possibly members. Away from substructures, the RRLS are a mixture of Oosterhoff types I and II, but mostly OoI (∼73%). The accretion of galaxies resembling in RRLS content the most massive Milky Way satellites (LMC, SMC, For, Sgr) may explain this preponderance of OoI. Six new RRLS and three new anomalous Cepheids were found in the Sextans dSph galaxy.

  3. 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 < [Fe/H] < -1) stellar population in the Milky Way 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.

  4. A HIGH-VELOCITY BULGE RR LYRAE VARIABLE ON A HALO-LIKE ORBIT

    International Nuclear Information System (INIS)

    Kunder, Andrea; Storm, J.; Rich, R. M.; Hawkins, K.; Poleski, R.; Johnson, C. I.; Shen, J.; Li, Z.-Y.; Cordero, M. J.; Nataf, D. M.; Bono, G.; Walker, A. R.; Koch, A.; De Propris, R.; Udalski, A.; Szymanski, M. K.; Soszynski, I.; Pietrzynski, G.; Ulaczyk, K.; Wyrzykowski, Ł.

    2015-01-01

    We report on the RR Lyrae variable star, MACHO 176.18833.411, located toward the Galactic bulge and observed within the data from the ongoing Bulge RR Lyrae Radial Velocity Assay, which has the unusual radial velocity of −372 ± 8 km s −1 and true space velocity of −482 ± 22 km s −1 relative to the Galactic rest frame. Located less than 1 kpc from the Galactic center and toward a field at (l, b) = (3, −2.5), this pulsating star has properties suggesting it belongs to the bulge RR Lyrae star population, yet a velocity indicating it is abnormal, at least with respect to bulge giants and red clump stars. We show that this star is most likely a halo interloper and therefore suggest that halo contamination is not insignificant when studying metal-poor stars found within the bulge area, even for stars within 1 kpc of the Galactic center. We discuss the possibility that MACHO 176.18833.411 is on the extreme edge of the bulge RR Lyrae radial velocity distribution, and also consider a more exotic scenario in which it is a runaway star moving through the Galaxy

  5. La Silla quest RR Lyrae star survey: Region I

    Energy Technology Data Exchange (ETDEWEB)

    Zinn, R.; Miller, L. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States); Horowitz, B.; Baltay, C.; Ellman, N.; Hadjiyska, E.; Rabinowitz, D. [Department of Physics, Yale University, P.O. Box 208120, New Haven, CT 06511-8499 (United States); Vivas, A. K. [Centro de Investigaciones de Astronomía, Apartado Postal 264, Mérida 5101-A (Venezuela, Bolivarian Republic of)

    2014-01-20

    A search for RR Lyrae stars (RRLSs) in ∼840 deg{sup 2} of the sky in right ascension 150°-210° and declination –10° to + 10° yielded 1013 type ab and 359 type c RRLS. This sample is used to study the density profile of the Galactic halo, halo substructures, and the Oosterhoff type of the halo over distances (d {sub ☉}) from ∼5 to ∼80 kpc. The halo is flattened toward the Galactic plane, and its density profile steepens in slope at galactocentric distances greater than ∼25 kpc. The RRLS in the stellar stream from the Sagittarius dwarf spheroidal (dSph) galaxy match well the model of Law and Majewski for the stars that were stripped 1.3-3.2 Gyr ago, but not for the ones stripped 3.2-5.0 Gyr ago. Over densities are found at the locations of the Virgo Overdensity and the Virgo Stellar Stream. Within 1° of 1220-1, which Jerjen et al. identify as a halo substructure at d {sub ☉} ∼ 24 kpc, there are four RRLS that are possibly members. Away from substructures, the RRLS are a mixture of Oosterhoff types I and II, but mostly OoI (∼73%). The accretion of galaxies resembling in RRLS content the most massive Milky Way satellites (LMC, SMC, For, Sgr) may explain this preponderance of OoI. Six new RRLS and three new anomalous Cepheids were found in the Sextans dSph galaxy.

  6. A HIGH-VELOCITY BULGE RR LYRAE VARIABLE ON A HALO-LIKE ORBIT

    Energy Technology Data Exchange (ETDEWEB)

    Kunder, Andrea; Storm, J. [Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); Rich, R. M. [Department of Physics and Astronomy, University of California at Los Angeles, Los Angeles, CA 90095-1562 (United States); Hawkins, K. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Poleski, R. [Department of Astronomy, Ohio State University, 140 W. 18th Avenue, Columbus, OH 43210 (United States); Johnson, C. I. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Shen, J.; Li, Z.-Y. [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Cordero, M. J. [Astronomisches Rechen-Institut: Zentrum für Astronomie, Mönchhofstr. 12-14, D-69120 Heidelberg (Germany); Nataf, D. M. [Research School of Astronomy and Astrophysics, The Australian National University, Canberra, ACT 2611 (Australia); Bono, G. [Dipartimento di Fisica, Universita di Roma Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Roma (Italy); Walker, A. R. [Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603, La Serena (Chile); Koch, A. [Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, D-69117 Heidelberg (Germany); De Propris, R. [Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Turku (Finland); Udalski, A.; Szymanski, M. K.; Soszynski, I.; Pietrzynski, G.; Ulaczyk, K.; Wyrzykowski, Ł. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); and others

    2015-07-20

    We report on the RR Lyrae variable star, MACHO 176.18833.411, located toward the Galactic bulge and observed within the data from the ongoing Bulge RR Lyrae Radial Velocity Assay, which has the unusual radial velocity of −372 ± 8 km s{sup −1} and true space velocity of −482 ± 22 km s{sup −1} relative to the Galactic rest frame. Located less than 1 kpc from the Galactic center and toward a field at (l, b) = (3, −2.5), this pulsating star has properties suggesting it belongs to the bulge RR Lyrae star population, yet a velocity indicating it is abnormal, at least with respect to bulge giants and red clump stars. We show that this star is most likely a halo interloper and therefore suggest that halo contamination is not insignificant when studying metal-poor stars found within the bulge area, even for stars within 1 kpc of the Galactic center. We discuss the possibility that MACHO 176.18833.411 is on the extreme edge of the bulge RR Lyrae radial velocity distribution, and also consider a more exotic scenario in which it is a runaway star moving through the Galaxy.

  7. Gaia Data Release 1. Testing parallaxes with local Cepheids and RR Lyrae stars

    Science.gov (United States)

    Gaia Collaboration; Clementini, G.; Eyer, L.; Ripepi, V.; Marconi, M.; Muraveva, T.; Garofalo, A.; Sarro, L. M.; Palmer, M.; Luri, X.; Molinaro, R.; Rimoldini, L.; Szabados, L.; Musella, I.; Anderson, R. I.; Prusti, T.; de Bruijne, J. H. J.; Brown, A. G. A.; Vallenari, A.; Babusiaux, C.; Bailer-Jones, C. A. L.; Bastian, U.; Biermann, M.; Evans, D. W.; Jansen, F.; Jordi, C.; Klioner, S. A.; Lammers, U.; Lindegren, L.; Mignard, F.; Panem, C.; Pourbaix, D.; Randich, S.; Sartoretti, P.; Siddiqui, H. I.; Soubiran, C.; Valette, V.; van Leeuwen, F.; Walton, N. A.; Aerts, C.; Arenou, F.; Cropper, M.; Drimmel, R.; Høg, E.; Katz, D.; Lattanzi, M. G.; O'Mullane, W.; Grebel, E. K.; Holland, A. D.; Huc, C.; Passot, X.; Perryman, M.; Bramante, L.; Cacciari, C.; Castañeda, J.; Chaoul, L.; Cheek, N.; De Angeli, F.; Fabricius, C.; Guerra, R.; Hernández, J.; Jean-Antoine-Piccolo, A.; Masana, E.; Messineo, R.; Mowlavi, N.; Nienartowicz, K.; Ordóñez-Blanco, D.; Panuzzo, P.; Portell, J.; Richards, P. J.; Riello, M.; Seabroke, G. M.; Tanga, P.; Thévenin, F.; Torra, J.; Els, S. G.; Gracia-Abril, G.; Comoretto, G.; Garcia-Reinaldos, M.; Lock, T.; Mercier, E.; Altmann, M.; Andrae, R.; Astraatmadja, T. L.; Bellas-Velidis, I.; Benson, K.; Berthier, J.; Blomme, R.; Busso, G.; Carry, B.; Cellino, A.; Cowell, S.; Creevey, O.; Cuypers, J.; Davidson, M.; De Ridder, J.; de Torres, A.; Delchambre, L.; Dell'Oro, A.; Ducourant, C.; Frémat, Y.; García-Torres, M.; Gosset, E.; Halbwachs, J.-L.; Hambly, N. C.; Harrison, D. L.; Hauser, M.; Hestroffer, D.; Hodgkin, S. T.; Huckle, H. E.; Hutton, A.; Jasniewicz, G.; Jordan, S.; Kontizas, M.; Korn, A. J.; Lanzafame, A. C.; Manteiga, M.; Moitinho, A.; Muinonen, K.; Osinde, J.; Pancino, E.; Pauwels, T.; Petit, J.-M.; Recio-Blanco, A.; Robin, A. C.; Siopis, C.; Smith, M.; Smith, K. W.; Sozzetti, A.; Thuillot, W.; van Reeven, W.; Viala, Y.; Abbas, U.; Abreu Aramburu, A.; Accart, S.; Aguado, J. J.; Allan, P. M.; Allasia, W.; Altavilla, G.; Álvarez, M. A.; Alves, J.; Andrei, A. H.; Anglada Varela, E.; Antiche, E.; Antoja, T.; Antón, S.; Arcay, B.; Bach, N.; Baker, S. G.; Balaguer-Núñez, L.; Barache, C.; Barata, C.; Barbier, A.; Barblan, F.; Barrado y Navascués, D.; Barros, M.; Barstow, M. A.; Becciani, U.; Bellazzini, M.; Bello García, A.; Belokurov, V.; Bendjoya, P.; Berihuete, A.; Bianchi, L.; Bienaymé, O.; Billebaud, F.; Blagorodnova, N.; Blanco-Cuaresma, S.; Boch, T.; Bombrun, A.; Borrachero, R.; Bouquillon, S.; Bourda, G.; Bragaglia, A.; Breddels, M. A.; Brouillet, N.; Brüsemeister, T.; Bucciarelli, B.; Burgess, P.; Burgon, R.; Burlacu, A.; Busonero, D.; Buzzi, R.; Caffau, E.; Cambras, J.; Campbell, H.; Cancelliere, R.; Cantat-Gaudin, T.; Carlucci, T.; Carrasco, J. M.; Castellani, M.; Charlot, P.; Charnas, J.; Chiavassa, A.; Clotet, M.; Cocozza, G.; Collins, R. S.; Costigan, G.; Crifo, F.; Cross, N. J. G.; Crosta, M.; Crowley, C.; Dafonte, C.; Damerdji, Y.; Dapergolas, A.; David, P.; David, M.; De Cat, P.; de Felice, F.; de Laverny, P.; De Luise, F.; De March, R.; de Souza, R.; Debosscher, J.; del Pozo, E.; Delbo, M.; Delgado, A.; Delgado, H. E.; Di Matteo, P.; Diakite, S.; Distefano, E.; Dolding, C.; Dos Anjos, S.; Drazinos, P.; Durán, J.; Dzigan, Y.; Edvardsson, B.; Enke, H.; Evans, N. W.; Eynard Bontemps, G.; Fabre, C.; Fabrizio, M.; Falcão, A. J.; Farràs Casas, M.; Federici, L.; Fedorets, G.; Fernández-Hernández, J.; Fernique, P.; Fienga, A.; Figueras, F.; Filippi, F.; Findeisen, K.; Fonti, A.; Fouesneau, M.; Fraile, E.; Fraser, M.; Fuchs, J.; Gai, M.; Galleti, S.; Galluccio, L.; Garabato, D.; García-Sedano, F.; Garralda, N.; Gavras, P.; Gerssen, J.; Geyer, R.; Gilmore, G.; Girona, S.; Giuffrida, G.; Gomes, M.; González-Marcos, A.; González-Núñez, J.; González-Vidal, J. J.; Granvik, M.; Guerrier, A.; Guillout, P.; Guiraud, J.; Gúrpide, A.; Gutiérrez-Sánchez, R.; Guy, L. P.; Haigron, R.; Hatzidimitriou, D.; Haywood, M.; Heiter, U.; Helmi, A.; Hobbs, D.; Hofmann, W.; Holl, B.; Holland, G.; Hunt, J. A. S.; Hypki, A.; Icardi, V.; Irwin, M.; Jevardat de Fombelle, G.; Jofré, P.; Jonker, P. G.; Jorissen, A.; Julbe, F.; Karampelas, A.; Kochoska, A.; Kohley, R.; Kolenberg, K.; Kontizas, E.; Koposov, S. E.; Kordopatis, G.; Koubsky, P.; Krone-Martins, A.; Kudryashova, M.; Bachchan, R. K.; Lacoste-Seris, F.; Lanza, A. F.; Lavigne, J.-B.; Le Poncin-Lafitte, C.; Lebreton, Y.; Lebzelter, T.; Leccia, S.; Leclerc, N.; Lecoeur-Taibi, I.; Lemaitre, V.; Lenhardt, H.; Leroux, F.; Liao, S.; Licata, E.; Lindstrøm, H. E. P.; Lister, T. A.; Livanou, E.; Lobel, A.; Löffler, W.; López, M.; Lorenz, D.; MacDonald, I.; Magalhães Fernandes, T.; Managau, S.; Mann, R. G.; Mantelet, G.; Marchal, O.; Marchant, J. M.; Marinoni, S.; Marrese, P. M.; Marschalkó, G.; Marshall, D. J.; Martín-Fleitas, J. M.; Martino, M.; Mary, N.; Matijevič, G.; McMillan, P. J.; Messina, S.; Michalik, D.; Millar, N. R.; Miranda, B. M. H.; Molina, D.; Molinaro, M.; Molnár, L.; Moniez, M.; Montegriffo, P.; Mor, R.; Mora, A.; Morbidelli, R.; Morel, T.; Morgenthaler, S.; Morris, D.; Mulone, A. F.; Narbonne, J.; Nelemans, G.; Nicastro, L.; Noval, L.; Ordénovic, C.; Ordieres-Meré, J.; Osborne, P.; Pagani, C.; Pagano, I.; Pailler, F.; Palacin, H.; Palaversa, L.; Parsons, P.; Pecoraro, M.; Pedrosa, R.; Pentikäinen, H.; Pichon, B.; Piersimoni, A. M.; Pineau, F.-X.; Plachy, E.; Plum, G.; Poujoulet, E.; Prša, A.; Pulone, L.; Ragaini, S.; Rago, S.; Rambaux, N.; Ramos-Lerate, M.; Ranalli, P.; Rauw, G.; Read, A.; Regibo, S.; Reylé, C.; Ribeiro, R. A.; Riva, A.; Rixon, G.; Roelens, M.; Romero-Gómez, M.; Rowell, N.; Royer, F.; Ruiz-Dern, L.; Sadowski, G.; Sagristà Sellés, T.; Sahlmann, J.; Salgado, J.; Salguero, E.; Sarasso, M.; Savietto, H.; Schultheis, M.; Sciacca, E.; Segol, M.; Segovia, J. C.; Segransan, D.; Shih, I.-C.; Smareglia, R.; Smart, R. L.; Solano, E.; Solitro, F.; Sordo, R.; Soria Nieto, S.; Souchay, J.; Spagna, A.; Spoto, F.; Stampa, U.; Steele, I. A.; Steidelmüller, H.; Stephenson, C. A.; Stoev, H.; Suess, F. F.; Süveges, M.; Surdej, J.; Szegedi-Elek, E.; Tapiador, D.; Taris, F.; Tauran, G.; Taylor, M. B.; Teixeira, R.; Terrett, D.; Tingley, B.; Trager, S. C.; Turon, C.; Ulla, A.; Utrilla, E.; Valentini, G.; van Elteren, A.; Van Hemelryck, E.; van Leeuwen, M.; Varadi, M.; Vecchiato, A.; Veljanoski, J.; Via, T.; Vicente, D.; Vogt, S.; Voss, H.; Votruba, V.; Voutsinas, S.; Walmsley, G.; Weiler, M.; Weingrill, K.; Wevers, T.; Wyrzykowski, Ł.; Yoldas, A.; Žerjal, M.; Zucker, S.; Zurbach, C.; Zwitter, T.; Alecu, A.; Allen, M.; Allende Prieto, C.; Amorim, A.; Anglada-Escudé, G.; Arsenijevic, V.; Azaz, S.; Balm, P.; Beck, M.; Bernstein, H.-H.; Bigot, L.; Bijaoui, A.; Blasco, C.; Bonfigli, M.; Bono, G.; Boudreault, S.; Bressan, A.; Brown, S.; Brunet, P.-M.; Bunclark, P.; Buonanno, R.; Butkevich, A. G.; Carret, C.; Carrion, C.; Chemin, L.; Chéreau, F.; Corcione, L.; Darmigny, E.; de Boer, K. S.; de Teodoro, P.; de Zeeuw, P. T.; Delle Luche, C.; Domingues, C. D.; Dubath, P.; Fodor, F.; Frézouls, B.; Fries, A.; Fustes, D.; Fyfe, D.; Gallardo, E.; Gallegos, J.; Gardiol, D.; Gebran, M.; Gomboc, A.; Gómez, A.; Grux, E.; Gueguen, A.; Heyrovsky, A.; Hoar, J.; Iannicola, G.; Isasi Parache, Y.; Janotto, A.-M.; Joliet, E.; Jonckheere, A.; Keil, R.; Kim, D.-W.; Klagyivik, P.; Klar, J.; Knude, J.; Kochukhov, O.; Kolka, I.; Kos, J.; Kutka, A.; Lainey, V.; LeBouquin, D.; Liu, C.; Loreggia, D.; Makarov, V. V.; Marseille, M. G.; Martayan, C.; Martinez-Rubi, O.; Massart, B.; Meynadier, F.; Mignot, S.; Munari, U.; Nguyen, A.-T.; Nordlander, T.; O'Flaherty, K. S.; Ocvirk, P.; Olias Sanz, A.; Ortiz, P.; Osorio, J.; Oszkiewicz, D.; Ouzounis, A.; Park, P.; Pasquato, E.; Peltzer, C.; Peralta, J.; Péturaud, F.; Pieniluoma, T.; Pigozzi, E.; Poels, J.; Prat, G.; Prod'homme, T.; Raison, F.; Rebordao, J. M.; Risquez, D.; Rocca-Volmerange, B.; Rosen, S.; Ruiz-Fuertes, M. I.; Russo, F.; Serraller Vizcaino, I.; Short, A.; Siebert, A.; Silva, H.; Sinachopoulos, D.; Slezak, E.; Soffel, M.; Sosnowska, D.; Straižys, V.; ter Linden, M.; Terrell, D.; Theil, S.; Tiede, C.; Troisi, L.; Tsalmantza, P.; Tur, D.; Vaccari, M.; Vachier, F.; Valles, P.; Van Hamme, W.; Veltz, L.; Virtanen, J.; Wallut, J.-M.; Wichmann, R.; Wilkinson, M. I.; Ziaeepour, H.; Zschocke, S.

    2017-09-01

    Context. Parallaxes for 331 classical Cepheids, 31 Type II Cepheids, and 364 RR Lyrae stars in common between Gaia and the Hipparcos and Tycho-2 catalogues are published in Gaia Data Release 1 (DR1) as part of the Tycho-Gaia Astrometric Solution (TGAS). Aims: In order to test these first parallax measurements of the primary standard candles of the cosmological distance ladder, which involve astrometry collected by Gaia during the initial 14 months of science operation, we compared them with literature estimates and derived new period-luminosity (PL), period-Wesenheit (PW) relations for classical and Type II Cepheids and infrared PL, PL-metallicity (PLZ), and optical luminosity-metallicity (MV-[Fe/H]) relations for the RR Lyrae stars, with zero points based on TGAS. Methods: Classical Cepheids were carefully selected in order to discard known or suspected binary systems. The final sample comprises 102 fundamental mode pulsators with periods ranging from 1.68 to 51.66 days (of which 33 with σϖ/ϖimpressive. Conclusions: TGAS parallaxes bring a significant added value to the previous Hipparcos estimates. The relations presented in this paper represent the first Gaia-calibrated relations and form a work-in-progress milestone report in the wait for Gaia-only parallaxes of which a first solution will become available with Gaia Data Release 2 (DR2) in 2018. Full Tables A.1-A.3 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/605/A79

  8. RR lyrae variable pulsations and the Oosterhoff groups

    International Nuclear Information System (INIS)

    Cox, A.N.

    1981-01-01

    It is concluded that Oosterhoff group I clusters have 0.55 M/sub sun/ stars and group II clusters have 0.65 M/sub sun/ stars. The Y value is always about 0.29. Mean log L/L/sub sun/ values are 1.66 and 1.78 giving M/sub bol/ = 0.60 and 0.30 for the RR Lyrae variables in these two groups of clusters. For field RR Lyrae variables at M = approx. 0.5 M/sub sun/ or less, perhaps M/sub bol/ = 0.90 or even larger as Clube and Jones propose. Apparently all evolution is blueward for RR Lyrae variables, and the color overlap of F and 1H pulsators is not real

  9. Evidence for Distinct Components of the Galactic Stellar Halo from 838 RR Lyrae Stars Discovered in the LONEOS-I Survey

    Energy Technology Data Exchange (ETDEWEB)

    Miceli, A; Rest, A; Stubbs, C W; Hawley, S L; Cook, K H; Magnier, E A; Krisciunas, K; Bowell, E; Koehn, B

    2007-02-23

    We present 838 ab-type RR Lyrae stars from the Lowell Observatory Near Earth Objects Survey Phase I (LONEOS-I). These objects cover 1430 deg{sup 2} and span distances ranging from 3-30kpc from the Galactic Center. Object selection is based on phased, photometric data with 28-50 epochs. We use this large sample to explore the bulk properties of the stellar halo, including the spatial distribution. The period-amplitude distribution of this sample shows that the majority of these RR Lyrae stars resemble Oosterhoff type I, but there is a significant fraction (26%) which have longer periods and appear to be Oosterhoff type II. We find that the radial distributions of these two populations have significantly different profiles ({rho}{sub OoI} {approx} R{sup -2.26{+-}0.07} and {rho}{sub OoII} {approx} R{sup -2.88{+-}0.11}). This suggests that the stellar halo was formed by at least two distinct accretion processes and supports dual-halo models.

  10. VizieR Online Data Catalog: CTIO/DECam photometry of RR Lyrae stars in M5 (Vivas+, 2017)

    Science.gov (United States)

    Vivas, A. K.; Saha, A.; Olsen, K.; Blum, R.; Olszewski, E. W.; Claver, J.; Valdes, F.; Axelrod, T.; Kaleida, C.; Kunder, A.; Narayan, G.; Matheson, T.; Walker, A.

    2017-11-01

    Observations were obtained during 2013 (2013 Jun 7-9, and 2013 Jun 21) and 2014 (2014 Mar 7-9) with the Dark Energy Camera (DECam) imager on the 4m Blanco Telescope at Cerro Tololo Inter-American Observatory (CTIO), Chile. Repeated DECam images of a field centered on M5 (R.A.=15:18:33.2, decl.=+02:04:51.7, J2000.0) were obtained using the u,g,r,i, and z filters. The large field of view (FOV) of DECam (2.2°) easily covers the whole globular cluster with only the central CCDs of the camera. A total of 66 RR Lyrae stars and 1 SX Phe were recognized in the field of M5. The individual measurements for the periodic variable stars are provided in Table2. In Table3, we present the list of periodic variable stars. (3 data files).

  11. THE ARAUCARIA PROJECT: THE DISTANCE TO THE CARINA DWARF GALAXY FROM INFRARED PHOTOMETRY OF RR LYRAE STARS

    Energy Technology Data Exchange (ETDEWEB)

    Karczmarek, Paulina; Pietrzynski, Grzegorz; Suchomska, Ksenia; Konorski, Piotr; Górski, Marek; Pilecki, Bogumił; Wielgórski, Piotr [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478, Warsaw (Poland); Gieren, Wolfgang; Graczyk, Dariusz, E-mail: pkarczmarek@astrouw.edu.pl, E-mail: ksenia@astrouw.edu.pl, E-mail: piokon@astrouw.edu.pl, E-mail: pilecki@astrouw.edu.pl, E-mail: pwielgorski@astrouw.edu.pl, E-mail: pietrzyn@astrouw.edu.pl, E-mail: wgieren@astro-udec.cl, E-mail: mgorski@astrouw.edu.pl, E-mail: darek@astro-udec.cl [Universidad de Concepción, Departamento de Astronomia, Casilla 160-C, Concepción (Chile)

    2015-09-15

    We obtained single-phase near-infrared (NIR) magnitudes in the J- and K-band for a sample of 33 RR Lyrae (RRL) stars in the Carina dSph galaxy. Applying different theoretical and empirical calibrations of the NIR period–luminosity–metallicity relation for RRL stars, we find consistent results and obtain a true, reddening-corrected distance modulus of 20.118 ± 0.017 (statistical) ± 0.11 (systematic) mag. This value is in excellent agreement with the results obtained in the context of the Araucaria Project from NIR photometry of red clump stars (20.165 ± 0.015) and the tip of red giant branch (20.09 ± 0.03 ± 0.12 mag in the J band, 20.14 ± 0.04 ± 0.14 mag in the K band), as well as with most independent distance determinations to this galaxy. The NIR RRL method proved to be a reliable tool for accurate distance determination at the 5% level or better, particularly for galaxies and globular clusters that lack young standard candles, like Cepheids.

  12. Little Bear’s pulsating stars: Variable star census of UMi dSph Galaxy

    Directory of Open Access Journals (Sweden)

    Kinemuchi K.

    2017-01-01

    Full Text Available Recent observations and a photometric search for variable stars in the Ursa Minor dwarf spheroidal galaxy (UMi dSph are presented. Our observations were taken at Apache Point Observatory in 2014 and 2016 using the 0.5m ARCSAT telescope and the West Mountain Observatory (WMO 0.9m telescope of Brigham Young University in 2016. Previously known RR Lyrae stars in our field of view of the UMi dSph are identified, and we also catalog new variable star candidates. Tentative classifications are given for some of the new variable stars. We have conducted period searches with the data collected with the WMO telescope. Our ultimate goal is to create an updated catalog of variable stars in the UMi dSph and to compare the RR Lyrae stellar characteristics to other RR Lyrae stars found in the Local Group dSph galaxies.

  13. Characterization of the VVV Survey RR Lyrae Population across the Southern Galactic Plane

    International Nuclear Information System (INIS)

    Minniti, Dante; Palma, Tali; Pullen, Joyce; Tissera, Patricia; Dékány, Istvan; Majaess, Daniel; Rejkuba, Marina; Valenti, Elena; Alonso-García, Javier; Catelan, Marcio; Contreras Ramos, Rodrigo; Zoccali, Manuela; Gonzalez, Oscar A.; Hempel, Maren; Irwin, Mike; Lucas, Philip W.; Saito, Roberto K.

    2017-01-01

    Deep near-IR images from the VISTA Variables in the Vía Láctea (VVV) Survey were used to search for RR Lyrae stars in the Southern Galactic plane. A sizable sample of 404 RR Lyrae of type ab stars was identified across a thin slice of the fourth Galactic quadrant (295° < ℓ < 350°, −2.°24 < b < −1.°05). The sample’s distance distribution exhibits a maximum density that occurs at the bulge tangent point, which implies that this primarily Oosterhoff type I population of RRab stars does not trace the bar delineated by their red clump counterparts. The bulge RR Lyrae population does not extend beyond ℓ  ∼ 340°, and the sample’s spatial distribution presents evidence of density enhancements and substructure that warrants further investigation. Indeed, the sample may be employed to evaluate Galactic evolution models, and is particularly lucrative since half of the discovered RR Lyrae are within reach of Gaia astrometric observations.

  14. Characterization of the VVV Survey RR Lyrae Population across the Southern Galactic Plane

    Energy Technology Data Exchange (ETDEWEB)

    Minniti, Dante; Palma, Tali; Pullen, Joyce; Tissera, Patricia [Departamento de Ciencias Físicas, Facultad de Ciencias Exactas, Universidad Andrés Bello, Av. Fernández Concha 700, Las Condes, Santiago (Chile); Dékány, Istvan [Astronomisches Rechen-Institut, Zentrum fuer Astronomie der Universitaet Heidelberg, Moenchhofstr. 12-14, D-69120 Heidelberg (Germany); Majaess, Daniel [Mount Saint Vincent University, Halifax, Nova Scotia (Canada); Rejkuba, Marina; Valenti, Elena [European Southern Observatory, Karl-Schwarszchild-Str. 2, D-85748 Garching bei Muenchen (Germany); Alonso-García, Javier; Catelan, Marcio; Contreras Ramos, Rodrigo; Zoccali, Manuela [Instituto Milenio de Astrofísica, Santiago (Chile); Gonzalez, Oscar A. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom); Hempel, Maren [Pontificia Universidad Católica de Chile, Instituto de Astrofisica, Av. Vicuna Mackenna 4860, Santiago (Chile); Irwin, Mike [Institute of Astronomy, Cambridge University, Cambridge, CB3 0HA (United Kingdom); Lucas, Philip W. [Department of Astronomy, University of Hertfordshire, Hertfordshire (United Kingdom); Saito, Roberto K. [Departamento de Física, Universidade Federal de Santa Catarina, Trindade 88040-900, Florianópolis, SC (Brazil)

    2017-04-01

    Deep near-IR images from the VISTA Variables in the Vía Láctea (VVV) Survey were used to search for RR Lyrae stars in the Southern Galactic plane. A sizable sample of 404 RR Lyrae of type ab stars was identified across a thin slice of the fourth Galactic quadrant (295° < ℓ < 350°, −2.°24 < b < −1.°05). The sample’s distance distribution exhibits a maximum density that occurs at the bulge tangent point, which implies that this primarily Oosterhoff type I population of RRab stars does not trace the bar delineated by their red clump counterparts. The bulge RR Lyrae population does not extend beyond ℓ  ∼ 340°, and the sample’s spatial distribution presents evidence of density enhancements and substructure that warrants further investigation. Indeed, the sample may be employed to evaluate Galactic evolution models, and is particularly lucrative since half of the discovered RR Lyrae are within reach of Gaia astrometric observations.

  15. PERIOD–COLOR AND AMPLITUDE–COLOR RELATIONS AT MAXIMUM AND MINIMUM LIGHT FOR RR LYRAE STARS IN THE SDSS STRIPE 82 REGION

    Energy Technology Data Exchange (ETDEWEB)

    Ngeow, Chow-Choong [Graduate Institute of Astronomy, National Central University, Jhongli 32001, Taiwan (China); Kanbur, Shashi M.; Schrecengost, Zachariah [Department of Physics, SUNY Oswego, Oswego, NY 13126 (United States); Bhardwaj, Anupam; Singh, Harinder P. [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)

    2017-01-10

    Investigation of period–color (PC) and amplitude–color (AC) relations at the maximum and minimum light can be used to probe the interaction of the hydrogen ionization front (HIF) with the photosphere and the radiation hydrodynamics of the outer envelopes of Cepheids and RR Lyraes. For example, theoretical calculations indicated that such interactions would occur at minimum light for RR Lyrae and result in a flatter PC relation. In the past, the PC and AC relations have been investigated by using either the ( V − R ){sub MACHO} or ( V − I ) colors. In this work, we extend previous work to other bands by analyzing the RR Lyraes in the Sloan Digital Sky Survey Stripe 82 Region. Multi-epoch data are available for RR Lyraes located within the footprint of the Stripe 82 Region in five ( ugriz ) bands. We present the PC and AC relations at maximum and minimum light in four colors: ( u − g ){sub 0}, ( g − r ){sub 0}, ( r − i ){sub 0}, and ( i − z ){sub 0}, after they are corrected for extinction. We found that the PC and AC relations for this sample of RR Lyraes show a complex nature in the form of flat, linear or quadratic relations. Furthermore, the PC relations at minimum light for fundamental mode RR Lyrae stars are separated according to the Oosterhoff type, especially in the ( g − r ){sub 0} and ( r − i ){sub 0} colors. If only considering the results from linear regressions, our results are quantitatively consistent with the theory of HIF-photosphere interaction for both fundamental and first overtone RR Lyraes.

  16. Spectrophotometry of RR Telescopii

    International Nuclear Information System (INIS)

    Walker, A.R.

    1977-01-01

    The strongest emission lines in the nova-like variable RR Telescopii were measured during late 1974 using a spectrum scanner. The wavelength range 3350 to 7700 A was scanned with a resolution of 50 A. The results are compared with published spectrophotometry covering the period 1961 to 72, with the conclusion that few changes have taken place in the last 6 yr. No evidence was found that suggested the existence of a cool star, nor was there any indication of night-to-night changes in the emission line intensities. The spectrophotometry of the past 15 yr is consistent with an expanding shell, the emission from this shell being caused by high-energy radiation from an underlying star. (author)

  17. The Araucaria Project: The Distance to the Fornax Dwarf Galaxy from Near-infrared Photometry of RR Lyrae Stars

    Science.gov (United States)

    Karczmarek, Paulina; Pietrzyński, Grzegorz; Górski, Marek; Gieren, Wolfgang; Bersier, David

    2017-12-01

    We have obtained single-phase near-infrared (NIR) magnitudes in the J and K bands for 77 RR Lyrae (RRL) stars in the Fornax Dwarf Spheroidal Galaxy. We have used different theoretical and empirical NIR period-luminosity-metallicity calibrations for RRL stars to derive their absolute magnitudes, and found a true, reddening-corrected distance modulus of 20.818+/- 0.015{{(statistical)}}+/- 0.116{{(systematic)}} mag. This value is in excellent agreement with the results obtained within the Araucaria Project from the NIR photometry of red clump stars (20.858 ± 0.013 mag), the tip of the red giant branch (20.84+/- 0.04+/- 0.14 mag), as well as with other independent distance determinations to this galaxy. The effect of metallicity and reddening is substantially reduced in the NIR domain, making this method a robust tool for accurate distance determination at the 5% level. This precision is expected to reach the level of 3% once the zero points of distance calibrations are refined thanks to the Gaia mission. NIR period-luminosity-metallicity relations of RRL stars are particularly useful for distance determinations to galaxies and globular clusters up to 300 kpc, that lack young standard candles, like Cepheids. Based on data collected with the VLT/HAWK-I instrument at ESO Paranal Observatory, Chile, as a part of programme 082.D-0123(B).

  18. Steam in RR Telescopii and Henize 2-38

    Energy Technology Data Exchange (ETDEWEB)

    Allen, D A [Anglo-Australian Observatory, Epping (Australia); Beattie, D H; Lee, T J; Stewart, J M; Williams, P M

    1978-03-01

    Low-resolution scans in the 1.9-2.6..mu..m atmospheric window reveal steam (H/sub 2/O) and CO adsorption bands in the spectra of the symbiotic stars RR Tel and He 2-38. The steam absorption in RR Tel is particularly intense while the CO is weak, implying the presence in the system of a Mira variable seen near minimum light. In He 2-38 the steam band is weaker while the CO is stronger, as expected for a Mira seen near maximum.

  19. The Globular Cluster NGC 6402 (M14). II. Variable Stars

    DEFF Research Database (Denmark)

    Contreras Peña, C.; Catelan, M.; Grundahl, F.

    2018-01-01

    approaches for the calibration of the absolute magnitudes of RR Lyrae stars. The possible presence of second-overtone RR Lyrae in M14 is critically addressed, with our results arguing against this possibility. By considering all of the RR Lyrae stars as members of the cluster, we derive =0.589 {{d...

  20. VARIABILITY AND STAR FORMATION IN LEO T, THE LOWEST LUMINOSITY STAR-FORMING GALAXY KNOWN TODAY

    Energy Technology Data Exchange (ETDEWEB)

    Clementini, Gisella; Cignoni, Michele; Ramos, Rodrigo Contreras; Federici, Luciana; Tosi, Monica [INAF, Osservatorio Astronomico di Bologna, I-40127 Bologna (Italy); Ripepi, Vincenzo; Marconi, Marcella; Musella, Ilaria, E-mail: gisella.clementini@oabo.inaf.it, E-mail: rodrigo.contreras@oabo.inaf.it, E-mail: luciana.federici@oabo.inaf.it, E-mail: monica.tosi@oabo.inaf.it, E-mail: michele.cignoni@unibo.it, E-mail: ripepi@na.astro.it, E-mail: marcella@na.astro.it, E-mail: ilaria@na.astro.it [INAF, Osservatorio Astronomico di Capodimonte, I-80131 Napoli (Italy)

    2012-09-10

    We present results from the first combined study of variable stars and star formation history (SFH) of the Milky Way 'ultra-faint' dwarf (UFD) galaxy Leo T, based on F606W and F814W multi-epoch archive observations obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. We have detected 14 variable stars in the galaxy. They include one fundamental-mode RR Lyrae star and 11 Anomalous Cepheids with periods shorter than 1 day, thus suggesting the occurrence of multiple star formation episodes in this UFD, of which one about 10 Gyr ago produced the RR Lyrae star. A new estimate of the distance to Leo T of 409{sup +29}{sub -27} kpc (distance modulus of 23.06 {+-} 0.15 mag) was derived from the galaxy's RR Lyrae star. Our V, V - I color-magnitude diagram (CMD) of Leo T reaches V {approx} 29 mag and shows features typical of a galaxy in transition between dwarf irregular and dwarf spheroidal types. A quantitative analysis of the SFH, based on the comparison of the observed V, V - I CMD with the expected distribution of stars for different evolutionary scenarios, confirms that Leo T has a complex SFH dominated by two enhanced periods about 1.5 and 9 Gyr ago, respectively. The distribution of stars and gas shows that the galaxy has a fairly asymmetric structure.

  1. The Globular Cluster NGC 6402 (M14). II. Variable Stars

    Science.gov (United States)

    Contreras Peña, C.; Catelan, M.; Grundahl, F.; Stephens, A. W.; Smith, H. A.

    2018-03-01

    We present time-series BVI photometry for the Galactic globular cluster NGC 6402 (M14). The data consist of ∼137 images per filter, obtained using the 0.9 and 1.0 m SMARTS telescopes at the Cerro Tololo Inter-American Observatory. The images were obtained during two observing runs in 2006–2007. The image-subtraction package ISIS, along with DAOPHOT II/ALLFRAME, was used to perform crowded-field photometry and search for variable stars. We identified 130 variables, eight of which are new discoveries. The variable star population is comprised of 56 ab-type RR Lyrae stars, 54 c-type RR Lyrae, 6 type II Cepheids, 1 W UMa star, 1 detached eclipsing binary, and 12 long-period variables. We provide Fourier decomposition parameters for the RR Lyrae, and discuss the physical parameters and photometric metallicity derived therefrom. The M14 distance modulus is also discussed, based on different approaches for the calibration of the absolute magnitudes of RR Lyrae stars. The possible presence of second-overtone RR Lyrae in M14 is critically addressed, with our results arguing against this possibility. By considering all of the RR Lyrae stars as members of the cluster, we derive =0.589 {{d}}{{a}}{{y}}{{s}}. This, together with the position of the RR Lyrae stars of both Bailey types in the period–amplitude diagram, suggests an Oosterhoff-intermediate classification for the cluster. Such an intermediate Oosterhoff type is much more commonly found in nearby extragalactic systems, and we critically discuss several other possible indications that may point to an extragalactic origin for this cluster. Based on observations obtained with the 0.9 m and 1 m telescopes at the Cerro Tololo Inter-American Observatory, Chile, operated by the SMARTS consortium.

  2. TIME-SERIES PHOTOMETRY OF GLOBULAR CLUSTERS: M62 (NGC 6266), THE MOST RR LYRAE-RICH GLOBULAR CLUSTER IN THE GALAXY?

    International Nuclear Information System (INIS)

    Contreras, R.; Catelan, M.; Smith, H. A.; Kuehn, C. A.; Pritzl, B. J.; Borissova, J.

    2010-01-01

    We present new time-series CCD photometry, in the B and V bands, for the moderately metal-rich ([Fe/H] ≅ -1.3) Galactic globular cluster M62 (NGC 6266). The present data set is the largest obtained so far for this cluster and consists of 168 images per filter, obtained with the Warsaw 1.3 m telescope at the Las Campanas Observatory and the 1.3 m telescope of the Cerro Tololo Inter-American Observatory, in two separate runs over the time span of 3 months. The procedure adopted to detect the variable stars was the optimal image subtraction method (ISIS v2.2), as implemented by Alard. The photometry was performed using both ISIS and Stetson's DAOPHOT/ALLFRAME package. We have identified 245 variable stars in the cluster fields that have been analyzed so far, of which 179 are new discoveries. Of these variables, 133 are fundamental mode RR Lyrae stars (RRab), 76 are first overtone (RRc) pulsators, 4 are type II Cepheids, 25 are long-period variables (LPVs), 1 is an eclipsing binary, and 6 are not yet well classified. Such a large number of RR Lyrae stars places M62 among the top two most RR Lyrae-rich (in the sense of total number of RR Lyrae stars present) globular clusters known in the Galaxy, second only to M3 (NGC 5272) with a total of 230 known RR Lyrae stars. Since this study covers most but not all of the cluster area, it is not unlikely that M62 is in fact the most RR Lyrae-rich globular cluster in the Galaxy. In like vein, thanks to the time coverage of our data sets, we were also able to detect the largest sample of LPVs known so far in a Galactic globular cluster. We analyze a variety of Oosterhoff type indicators for the cluster, including mean periods, period distribution, Bailey diagrams, and Fourier decomposition parameters (as well as the physical parameters derived therefrom). All of these indicators clearly show that M62 is an Oosterhoff type I system. This is in good agreement with the moderately high metallicity of the cluster, in spite of its

  3. The Cluster AgeS Experiment (CASE). Variable Stars in the Field of the Globular Cluster M22

    Science.gov (United States)

    Rozyczka, M.; Thompson, I. B.; Pych, W.; Narloch, W.; Poleski, R.; Schwarzenberg-Czerny, A.

    2017-09-01

    The field of the globular cluster M22 (NGC 6656) was monitored between 2000 and 2008 in a search for variable stars. BV light curves were obtained for 359 periodic, likely periodic, and long-term variables, 238 of which are new detections. 39 newly detected variables, and 63 previously known ones are members or likely members of the cluster, including 20 SX Phe, 10 RRab and 16 RRc type pulsators, one BL Her type pulsator, 21 contact binaries, and 9 detached or semi-detached eclipsing binaries. The most interesting among the identified objects are V112 - a bright multimode SX Phe pulsator, V125 - a β Lyr type binary on the blue horizontal branch, V129 - a blue/yellow straggler with a W UMa-like light curve, located halfway between the extreme horizontal branch and red giant branch, and V134 - an extreme horizontal branch object with P=2.33 d and a nearly sinusoidal light curve. All four of them are proper motion members of the cluster. Among nonmembers, a P=2.83 d detached eclipsing binary hosting a δ Sct type pulsator was found, and a peculiar P=0.93 d binary with ellipsoidal modulation and narrow minimum in the middle of one of the descending shoulders of the sinusoid. We also collected substantial new data for previously known variables. In particular we revise the statistics of the occurrence of the Blazhko effect in RR Lyr type variables of M22.

  4. WEAK GALACTIC HALO-DWARF SPHEROIDAL CONNECTION FROM RR LYRAE STARS

    Energy Technology Data Exchange (ETDEWEB)

    Fiorentino, Giuliana [INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Bono, Giuseppe [Dipartimento di Fisica, Universitá di Roma Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Roma (Italy); Monelli, Matteo; Gallart, Carme; Martínez-Vásquez, Clara E. [Instituto de Astrofísica de Canarias, Calle Via Lactea s/n, E-38205 La Laguna, Tenerife (Spain); Stetson, Peter B. [National Research Council, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Tolstoy, Eline [Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen (Netherlands); Salaris, Maurizio [Astrophysics Research Institute, Liverpool John Moores University IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L35RF (United Kingdom); Bernard, Edouard J., E-mail: giuliana.fiorentino@oabo.inaf.it [SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom)

    2015-01-01

    We discuss the role that dwarf galaxies may have played in the formation of the Galactic halo (Halo) using RR Lyrae stars (RRL) as tracers of their ancient stellar component. The comparison is performed using two observables (periods, luminosity amplitudes) that are reddening and distance independent. Fundamental mode RRL in 6 dwarf spheroidals (dSphs) and 11 ultra faint dwarf galaxies (∼1300) show a Gaussian period distribution well peaked around a mean period of (Pab) = 0.610 ± 0.001 days (σ = 0.03). The Halo RRL (∼15,000) are characterized by a broader period distribution. The fundamental mode RRL in all the dSphs apart from Sagittarius are completely lacking in High Amplitude Short Period (HASP) variables, defined as those having P ≲ 0.48 days and A{sub V} ≥ 0.75 mag. Such variables are not uncommon in the Halo and among the globular clusters and massive dwarf irregulars. To further interpret this evidence, we considered 18 globulars covering a broad range in metallicity (–2.3 ≲ [Fe/H] ≲ –1.1) and hosting more than 35 RRL each. The metallicity turns out to be the main parameter, since only globulars more metal-rich than [Fe/H] ∼ –1.5 host RRL in the HASP region. This finding suggests that dSphs similar to the surviving ones do not appear to be the major building-blocks of the Halo. Leading physical arguments suggest an extreme upper limit of ∼50% to their contribution. On the other hand, massive dwarfs hosting an old population with a broad metallicity distribution (Large Magellanic Cloud, Sagittarius) may have played a primary role in the formation of the Halo.

  5. Spectral Variability of the UXOR Star RR Tau Over 2.5 Magnitudes in V

    Science.gov (United States)

    Rodgers, B.; Wooden, D. H.; Grinin, V. P.; Shakhovskoy, D.

    2000-12-01

    We present moderate resolution optical spectra of the highly variable Herbig Ae star RR Tau over 12 epochs spanning 2.5 magnitudes in V. The data cover most of the optical spectrum from the CaII K line in the blue to the CaII infrared triplet in the far red. Using contemporaneous photometric measurements from two sources, we have reliable estimates of the visual magnitude of the system at each spectral epoch. We find some spectral activity to be closely correlated with photometric variability, while other features are remarkably stable. Significant variability is common in the cores of Hα and Hβ , but is not well correlated with photometric variability. On the other hand, the wings (Δ v>400km/s) of the Balmer lines are quite stable, showing no change in spectral type when compared to Kurucz line profiles. This, along with the constant equivalent width seen in several weak metal lines, suggest that the physical conditions of the underlying continuum source are not changing significantly, despite a factor of ten change in brightness. In contrast, strong low-ionization permitted lines, such as FeII, CaII and NaI, are seen in deep absorption when the star is bright (V <= 12), but disappear during photometric minima to reveal weak emission lines. These absorption lines are not being filled in by the emission but rather are physically disappearing from the system. This could occur, for example, if an obscuring screen moved between the continuum source and the absorbing gas. The [OI]6300 line, a common wind diagnostic, is seen in emission at all epochs, with flux which is roughly constant except increasing slightly when the system is faint. We discuss these data in the context of different scenarios for the photometric variability and find them to be more consistent with the obscuration hypothesis, than changing accretion luminosity. This work is part of the dissertation research of B. Rodgers, which has been funded in large part by a NASA Graduate Student Research

  6. The globular cluster ω Centauri and its RR Lyrae variables

    International Nuclear Information System (INIS)

    Dickens, R.J.

    1989-07-01

    The significance of some of the unusual characteristics of the globular cluster ωCentauri in various fundamental problems is explored. Interest is centred on the properties of the cluster RR Lyraes, and what they can contribute to studies of early cluster chemical enrichment, stellar pulsation, the distance scale, stellar evolution, stellar ages and the Oosterhoff period-shift problem. This article, which is intended to highlight problems and progress rather than give a comprehensive review, includes new results based on photometry of the RR Lyraes, red giants, subgiants, horizontal-branch and main sequence stars in the cluster. (author)

  7. Halo star streams in the solar neighborhood

    NARCIS (Netherlands)

    Kepley, Amanda A.; Morrison, Heather L.; Helmi, Amina; Kinman, T. D.; Van Duyne, Jeffrey; Martin, John C.; Harding, Paul; Norris, John E.; Freeman, Kenneth C.

    2007-01-01

    We have assembled a sample of halo stars in the solar neighborhood to look for halo substructure in velocity and angular momentum space. Our sample ( 231 stars) includes red giants, RR Lyrae variable stars, and red horizontal branch stars within 2.5 kpc of the Sun with [Fe/H] less than -1.0. It was

  8. RR Lyrae star distance scale and kinematics from inner bulge to 50 kpc

    Directory of Open Access Journals (Sweden)

    Dambis Andrei

    2017-01-01

    Full Text Available We use the currently most complete sample of ∼ 3500 type ab RR Lyraes in our Galaxy with available radial-velocity and [Fe/H] measurements to perform a statisticalparallax analysis for a subsample of ∼ 600 type ab RR Lyraes located within 5 kpc from the Sun to refine the parameters of optical and WISE W1-band period-metallicityluminosity relations and adjust our preliminary distances. The new zero point implies the rescaled estimates for the solar Galactocentric distance (RG = 7.99 ± 0.37 kpc and the LMC distance modulus (DMLMC = 18.39 ±0.09. We use the kinematic data for the entire sample to explore the dependence of the halo and thick-disk RR Lyrae velocity ellipsoids on Galactocentric distance from the inner bulge out to R ∼ 50 kpc.

  9. THE LEO IV DWARF SPHEROIDAL GALAXY: COLOR-MAGNITUDE DIAGRAM AND PULSATING STARS

    International Nuclear Information System (INIS)

    Moretti, Maria Ida; Dall'Ora, Massimo; Ripepi, Vincenzo

    2009-01-01

    We present the first V, B - V color-magnitude diagram of the Leo IV dwarf spheroidal galaxy, a faint Milky Way satellite recently discovered by the Sloan Digital Sky Survey. We have obtained B, V time-series photometry reaching about half a magnitude below the Leo IV turnoff, which we detect at V = 24.7 mag, and have performed the first study of the variable star population. We have identified three RR Lyrae stars (all fundamental-mode pulsators, RRab) and one SX Phoenicis variable in the galaxy. In the period-amplitude diagram the Leo IV RR Lyrae stars are located close to the loci of Oosterhoff type I systems and the evolved fundamental-mode RR Lyrae stars in the Galactic globular cluster M3. However, their mean pulsation period, (Pab) = 0.655 days, would suggest an Oosterhoff type II classification for this galaxy. The RR Lyrae stars trace very well the galaxy's horizontal branch, setting its average magnitude at (V RR ) = 21.48 ± 0.03 mag (standard deviation of the mean). This leads to a distance modulus of μ 0 = 20.94 ± 0.07 mag, corresponding to a distance of 154 ± 5 kpc, by adopting for the Leo IV dSph a reddening E(B - V) = 0.04 ± 0.01 mag and a metallicity of [Fe/H] = -2.31 ± 0.10.

  10. The Outer Halo of the Milky Way as Probed by RR Lyr Variables from the Palomar Transient Facility

    Science.gov (United States)

    Cohen, Judith G.; Sesar, Branimir; Bahnolzer, Sophianna; He, Kevin; Kulkarni, Shrinivas R.; Prince, Thomas A.; Bellm, Eric; Laher, Russ R.

    2017-11-01

    RR Lyrae stars are ideal massless tracers that can be used to study the total mass and dark matter content of the outer halo of the Milky Way (MW). This is because they are easy to find in the light-curve databases of large stellar surveys and their distances can be determined with only knowledge of the light curve. We present here a sample of 112 RR Lyr stars beyond 50 kpc in the outer halo of the MW, excluding the Sgr streams, for which we have obtained moderate-resolution spectra with Deimos on the Keck II Telescope. Four of these have distances exceeding 100 kpc. These were selected from a much larger set of 447 candidate RR Lyr stars that were data-mined using machine-learning techniques applied to the light curves of variable stars in the Palomar Transient Facility database. The observed radial velocities taken at the phase of the variable corresponding to the time of observation were converted to systemic radial velocities in the Galactic standard of rest. From our sample of 112 RR Lyr stars we determine the radial velocity dispersion in the outer halo of the MW to be ˜90 km s-1 at 50 kpc, falling to about 65 km s-1 near 100 kpc once a small number of major outliers are removed. With reasonable estimates of the completeness of our sample of 447 candidates and assuming a spherical halo, we find that the stellar density in the outer halo declines as {r}-4. Based in part on observations obtained at the W. M. Keck Observatory, which is operated jointly by the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration.

  11. VARIABLE STARS IN THE ULTRA-FAINT DWARF SPHEROIDAL GALAXY URSA MAJOR I

    Energy Technology Data Exchange (ETDEWEB)

    Garofalo, Alessia; Moretti, Maria Ida [Dipartimento di Astronomia, Universita di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Cusano, Felice; Clementini, Gisella [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Ripepi, Vincenzo; Dall' Ora, Massimo; Coppola, Giuseppina; Musella, Ilaria; Marconi, Marcella, E-mail: alessia.garofalo@studio.unibo.it, E-mail: fcusano@na.astro.it, E-mail: gisella.clementini@oabo.inaf.it, E-mail: ripepi@na.astro.it, E-mail: dallora@na.astro.it, E-mail: imoretti@na.astro.it, E-mail: coppola@na.astro.it, E-mail: ilaria@na.astro.it, E-mail: marcella@na.astro.it [INAF-Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli (Italy)

    2013-04-10

    We have performed the first study of the variable star population of Ursa Major I (UMa I), an ultra-faint dwarf satellite recently discovered around the Milky Way (MW) by the Sloan Digital Sky Survey. Combining time series observations in the B and V bands from four different telescopes, we have identified seven RR Lyrae stars in UMa I, of which five are fundamental-mode (RRab) and two are first-overtone pulsators (RRc). Our V, B - V color-magnitude diagram of UMa I reaches V {approx} 23 mag (at a signal-to-noise ratio of {approx}6) and shows features typical of a single old stellar population. The mean pulsation period of the RRab stars (P{sub ab}) = 0.628, {sigma} = 0.071 days (or (P{sub ab}) = 0.599, {sigma} = 0.032 days, if V4, the longest period and brightest variable, is discarded) and the position on the period-amplitude diagram suggest an Oosterhoff-intermediate classification for the galaxy. The RR Lyrae stars trace the galaxy horizontal branch (HB) at an average apparent magnitude of (V(RR)) = 20.43 {+-} 0.02 mag (average on six stars and discarding V4), giving in turn a distance modulus for UMa I of (m - M){sub 0} = 19.94 {+-} 0.13 mag, distance d = 97.3{sup +6.0}{sub -5.7} kpc, in the scale where the distance modulus of the Large Magellanic Cloud is 18.5 {+-} 0.1 mag. Isodensity contours of UMa I red giants and HB stars (including the RR Lyrae stars identified in this study) show that the galaxy has an S-shaped structure, which is likely caused by the tidal interaction with the MW. Photometric metallicities were derived for six of the UMa I RR Lyrae stars from the parameters of the Fourier decomposition of the V-band light curves, leading to an average metal abundance of [Fe/H] = -2.29 dex ({sigma} = 0.06 dex, average on six stars) on the Carretta et al. metallicity scale.

  12. Unmixing the Galactic halo with RR Lyrae tagging

    Science.gov (United States)

    Belokurov, V.; Deason, A. J.; Koposov, S. E.; Catelan, M.; Erkal, D.; Drake, A. J.; Evans, N. W.

    2018-06-01

    We show that tagging RR Lyrae stars according to their location in the period-amplitude diagram can be used to shed light on the genesis of the Galactic stellar halo. The mixture of RR Lyrae of ab type, separated into classes along the lines suggested by Oosterhoff, displays a strong and coherent evolution with Galactocentric radius. The change in the RR Lyrae composition appears to coincide with the break in the halo's radial density profile at ˜25 kpc. Using simple models of the stellar halo, we establish that at least three different types of accretion events are necessary to explain the observed RRab behaviour. Given that there exists a correlation between the RRab class fraction and the total stellar content of a dwarf satellite, we hypothesize that the field halo RRab composition is controlled by the mass of the progenitor contributing the bulk of the stellar debris at the given radius. This idea is tested against a suite of cosmological zoom-in simulations of Milky Way-like stellar halo formation. Finally, we study some of the most prominent stellar streams in the Milky Way halo and demonstrate that their RRab class fractions follow the trends established previously.

  13. A Data-driven Study of RR Lyrae Near-IR Light Curves: Principal Component Analysis, Robust Fits, and Metallicity Estimates

    Science.gov (United States)

    Hajdu, Gergely; Dékány, István; Catelan, Márcio; Grebel, Eva K.; Jurcsik, Johanna

    2018-04-01

    RR Lyrae variables are widely used tracers of Galactic halo structure and kinematics, but they can also serve to constrain the distribution of the old stellar population in the Galactic bulge. With the aim of improving their near-infrared photometric characterization, we investigate their near-infrared light curves, as well as the empirical relationships between their light curve and metallicities using machine learning methods. We introduce a new, robust method for the estimation of the light-curve shapes, hence the average magnitudes of RR Lyrae variables in the K S band, by utilizing the first few principal components (PCs) as basis vectors, obtained from the PC analysis of a training set of light curves. Furthermore, we use the amplitudes of these PCs to predict the light-curve shape of each star in the J-band, allowing us to precisely determine their average magnitudes (hence colors), even in cases where only one J measurement is available. Finally, we demonstrate that the K S-band light-curve parameters of RR Lyrae variables, together with the period, allow the estimation of the metallicity of individual stars with an accuracy of ∼0.2–0.25 dex, providing valuable chemical information about old stellar populations bearing RR Lyrae variables. The methods presented here can be straightforwardly adopted for other classes of variable stars, bands, or for the estimation of other physical quantities.

  14. VizieR Online Data Catalog: RR Lyrae stars from the PS1 3π survey (Sesar+, 2017)

    Science.gov (United States)

    Sesar, B.; Hernitschek, N.; Mitrovic, S.; Ivezic, Z.; Rix, H.-W.; Cohen, J. G.; Bernard, E. J.; Grebel, E. K.; Martin, N. F.; Schlafly, E. F.; Burgett, W. S.; Draper, P. W.; Flewelling, H.; Kaiser, N.; Kudritzki, R. P.; Magnier, E. A.; Metcalfe, N.; Tonry, J. L.; Waters, C.

    2018-04-01

    Building on the work by Hernitschek+ (2016, J/ApJ/817/73), in this paper, we use the final PS1 data release (PV3) to significantly increase the completeness and purity of the PS1 sample of RR Lyrae stars. Pan-STARRS1 (PS1; Kaiser+ 2010, see II/349) is a wide-field optical/near-IR survey telescope system located at the Haleakala Observatory on the island of Maui in Hawai'i. The largest survey undertaken by the telescope, the PS1 3π survey (Chambers K.C. 2011, BAAS, 43, 113.01), has observed the entire sky north of decl. -30° in five filter bands, reaching 5σ single-epoch depths of about 22.0, 22.0, 21.9, 21.0, and 19.8mag in gP1, rP1, iP1, zP1, and yP1 bands, respectively. The uncertainty in photometric calibration of the survey is <~0.01mag, and the astrometric precision of single-epoch detections is 10mas. (4 data files).

  15. The Milky Way's Circular Velocity Curve and Its Constraint on the Galactic Mass with RR Lyrae Stars

    Energy Technology Data Exchange (ETDEWEB)

    Ablimit, Iminhaji; Zhao, Gang, E-mail: iminhaji@nao.cas.cn, E-mail: gzhao@nao.cas.cn [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2017-09-01

    We present a sample of 1148 ab-type RR Lyrae (RRLab) variables identified from Catalina Surveys Data Release 1, combined with SDSS DR8 and LAMOST DR4 spectral data. We first use a large sample of 860 Galactic halo RRLab stars and derive the circular velocity distributions for the stellar halo. With the precise distances and carefully determined radial velocities (the center-of-mass radial velocities) and by considering the pulsation of the RRLab stars in our sample, we can obtain a reliable and comparable stellar halo circular velocity curve. We follow two different prescriptions for the velocity anisotropy parameter β in the Jeans equation to study the circular velocity curve and mass profile. Additionally, we test two different solar peculiar motions in our calculation. The best result we obtained with the adopted solar peculiar motion 1 of ( U , V , W ) = (11.1, 12, 7.2) km s{sup −1} is that the enclosed mass of the Milky Way within 50 kpc is (3.75 ± 1.33) × 10{sup 11} M {sub ⊙} based on β = 0 and the circular velocity 180 ± 31.92 (km s{sup −1}) at 50 kpc. This result is consistent with dynamical model results, and it is also comparable to the results of previous similar works.

  16. VARIABLE STARS IN LARGE MAGELLANIC CLOUD GLOBULAR CLUSTERS. II. NGC 1786

    International Nuclear Information System (INIS)

    Kuehn, Charles A.; Smith, Horace A.; De Lee, Nathan; Catelan, Márcio; Pritzl, Barton J.; Borissova, Jura

    2012-01-01

    This is the second in a series of papers studying the variable stars in Large Magellanic Cloud globular clusters. The primary goal of this series is to study how RR Lyrae stars in Oosterhoff-intermediate systems compare to their counterparts in Oosterhoff I/II systems. In this paper, we present the results of our new time-series B–V photometric study of the globular cluster NGC 1786. A total of 65 variable stars were identified in our field of view. These variables include 53 RR Lyraes (27 RRab, 18 RRc, and 8 RRd), 3 classical Cepheids, 1 Type II Cepheid, 1 Anomalous Cepheid, 2 eclipsing binaries, 3 Delta Scuti/SX Phoenicis variables, and 2 variables of undetermined type. Photometric parameters for these variables are presented. We present physical properties for some of the RR Lyrae stars, derived from Fourier analysis of their light curves. We discuss several different indicators of Oosterhoff type which indicate that the Oosterhoff classification of NGC 1786 is not as clear cut as what is seen in most globular clusters.

  17. The Distance to M54 using Infrared Photometry of RR Lyrae Variable Stars and the Implications of its Relation to the Sagittarius Dwarf Galaxy

    Science.gov (United States)

    Gupta, Arvind F.; Beaton, Rachael L.; Majewski, Steven R.; SMHASH Team

    2018-01-01

    CDM cosmological models predict that dark matter halo density profiles will have central cusps. Yet for many dwarf spheroidal galaxies (dSphs), this expectation is in contrast with observations of cored, rather than cusped, halos. This 'cusp-core problem' is apparent in the Sagittarius Dwarf Galaxy (Sgr), one of the largest satellites of the Milky Way. The globular cluster M54, one of several clusters associated with Sgr, coincides in on-sky position with the center of the main body of Sgr. While several studies find that M54 lies within the center of Sgr, other findings show that M54 is offset from the center by several kiloparsecs along our line of sight. The latter requires Sgr to have a cored dark matter distribution. In the presence of a cuspy halo, the orbit of M54 would have decayed via dynamical friction and the cluster would have fallen to the center of Sgr. A clear determination of the relation of the two bodies may help us better understand the distribution of dark matter in Sgr and other dSphs. Here we present a measurement of the distance modulus to M54 using a set of RR Lyrae variable stars in near-infrared Magellan data mid-infrared Spitzer data. The magnitudes of individual stars are measured using multi-epoch PSF photometry and light curve fitting. From precise RR Lyrae period-luminosity relations at these wavelengths, we then find the mean M54 distance modulus to be 17.126 ± 0.023 (ran) ± 0.080 (sys). Our result is consistent with a distance measurement to Sgr derived via nearly identical methods and thus also consistent with the expectation of a central cusp in the dark matter density profile of Sgr.

  18. ON A NEW THEORETICAL FRAMEWORK FOR RR LYRAE STARS. I. THE METALLICITY DEPENDENCE

    International Nuclear Information System (INIS)

    Marconi, M.; Coppola, G.; Musella, I.; Ripepi, V.; Bono, G.; Braga, V.; Buonanno, R.; Pietrinferni, A.; Castellani, M.; Stellingwerf, R. F.

    2015-01-01

    We present new nonlinear, time-dependent convective hydrodynamical models of RR Lyrae stars computed assuming a constant helium-to-metal enrichment ratio and a broad range in metal abundances (Z = 0.0001–0.02). The stellar masses and luminosities adopted to construct the pulsation models were fixed according to detailed central He-burning horizontal-branch evolutionary models. The pulsation models cover a broad range in stellar luminosity and effective temperatures and the modal stability is investigated for both fundamental (FU) and first overtone polsators (FOs). We predict the topology of the instability strip (IS) as a function of the metal content and new analytical relations for the edges of the IS in the observational plane. Moreover, a new analytical relation to constrain the pulsation mass of double pulsators as a function of the period ratio and the metal content is provided. We derive new Period–Radius–Metallicity relations for FU and FO pulsators. They agree quite well with similar empirical and theoretical relations in the literature. From the predicted bolometric light curves, transformed into optical (UBVRI) and near-infrared (NIR; JHK) bands, we compute the intensity-averaged mean magnitudes along the entire pulsation cycle and in turn new and homogenous metal-dependent (RIJHK) Period–Luminosity relations. Moreover, we compute new dual and triple-band optical, optical–NIR, and NIR Period–Wesenheit–Metallicity relations. Interestingly, we find that the optical Period-W(V, B–V) is independent of the metal content and that the accuracy of individual distances is a balance between the adopted diagnostics and the precision of photometric and spectroscopic data sets

  19. The occurrence of Binary Evolution Pulsators in the classical instability strip of RR Lyrae and Cepheid variables

    OpenAIRE

    Karczmarek, P.; Wiktorowicz, G.; Iłkiewicz, K.; Smolec, R.; Stępień, K.; Pietrzyński, G.; Gieren, W.; Belczynski, K.

    2016-01-01

    Single star evolution does not allow extremely low-mass stars to cross the classical instability strip (IS) during the Hubble time. However, within binary evolution framework low-mass stars can appear inside the IS once the mass transfer (MT) is taken into account. Triggered by a discovery of low-mass 0.26 Msun RR Lyrae-like variable in a binary system, OGLE-BLG-RRLYR-02792, we investigate the occurrence of similar binary components in the IS, which set up a new class of low-mass pulsators. T...

  20. THE IMPACT OF CONTAMINATED RR LYRAE/GLOBULAR CLUSTER PHOTOMETRY ON THE DISTANCE SCALE

    Energy Technology Data Exchange (ETDEWEB)

    Majaess, D.; Turner, D.; Lane, D. [Department of Astronomy and Physics, Saint Mary' s University, Halifax, NS B3H 3C3 (Canada); Gieren, W., E-mail: dmajaess@ap.smu.ca [Departamento de Astronomia, Universidad de Concepcion, Casilla 160-C, CL Concepcion (Chile)

    2012-06-10

    RR Lyrae variables and the stellar constituents of globular clusters are employed to establish the cosmic distance scale and age of the universe. However, photometry for RR Lyrae variables in the globular clusters M3, M15, M54, M92, NGC 2419, and NGC 6441 exhibit a dependence on the clustercentric distance. For example, variables and stars positioned near the crowded high-surface brightness cores of the clusters may suffer from photometric contamination, which invariably affects a suite of inferred parameters (e.g., distance, color excess, absolute magnitude, etc.). The impetus for this study is to mitigate the propagation of systematic uncertainties by increasing awareness of the pernicious impact of contaminated and radial-dependent photometry.

  1. Testing parallaxes with local Cepheids and RR Lyrae stars

    Czech Academy of Sciences Publication Activity Database

    Clementini, G.; Eyer, L.; Ripepi, V.; Marconi, M.; Muraveva, T.; Garofalo, A.; Sarro, L.M.; Palmer, M.; Luri, X.; Koubský, Pavel; Votruba, Viktor

    2017-01-01

    Roč. 605, September (2017), A79/1-A79/29 E-ISSN 1432-0746 R&D Projects: GA MŠk(CZ) LG15010 Grant - others:ESA(XE) ESA-PECS project no. 98058 Institutional support: RVO:67985815 Keywords : astrometry * parallaxes * stars Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 5.014, year: 2016

  2. THE BHB STARS IN THE SURVEY FIELDS OF RODGERS ET AL. (1993): NEW OBSERVATIONS AND COMPARISONS WITH OTHER RECENT SURVEYS

    International Nuclear Information System (INIS)

    Kinman, T. D.; Brown, Warren R.

    2011-01-01

    We study blue horizontal branch (BHB) and RR Lyrae stars in the Rodgers et al. fields and compare their velocity and density distributions with other surveys in the same part of the sky. Photometric data are given for 176 early-type stars in the northern field. We identify fourteen BHB stars and four possible BHB stars, and determine the selection efficiency of the Century survey, the HK survey, and the SDSS survey for BHB stars. We give light curves and γ radial velocities for three type ab RR Lyrae stars in the northern field; comparison with the nearby LONEOS survey shows that there is likely to be an equal number of lower-amplitude type ab RR Lyrae stars that we do not find. There are therefore at least twice as many BHB stars as type ab RR Lyrae stars in the northern field-similar to the ratio in the solar neighborhood. The velocity distribution of the southern field shows no evidence for an anomalous thick disk that was found by Gilmore et al.; the halo velocity peaks at a slightly prograde rotational velocity but there is also a significant retrograde halo component in this field. The velocity distribution in the northern field shows no evidence of Galactic rotation for |Z| ≥ 4 kpc and a slight prograde motion for |Z| < 4 kpc. The space densities of BHB stars in the northern field agree with an extrapolation of the power-law distribution recently derived by de Propris et al. For |Z| < 4 kpc, however, we observe an excess of BHB stars compared with this power law. We conclude that these BHB stars mostly belong to a spatially flattened, non-rotating inner halo component of the Milky Way in confirmation of the Kinman et al. analysis of Century survey BHB stars.

  3. Pulsating star research and the Gaia revolution

    Science.gov (United States)

    Eyer, Laurent; Clementini, Gisella; Guy, Leanne P.; Rimoldini, Lorenzo; Glass, Florian; Audard, Marc; Holl, Berry; Charnas, Jonathan; Cuypers, Jan; Ridder, Joris De; Evans, Dafydd W.; de Fombelle, Gregory Jevardat; Lanzafame, Alessandro; Lecoeur-Taibi, Isabelle; Mowlavi, Nami; Nienartowicz, Krzysztof; Riello, Marco; Ripepi, Vincenzo; Sarro, Luis; Süveges, Maria

    2017-09-01

    In this article we present an overview of the ESA Gaia mission and of the unprecedented impact that Gaia will have on the field of variable star research. We summarise the contents and impact of the first Gaia data release on the description of variability phenomena, with particular emphasis on pulsating star research. The Tycho-Gaia astrometric solution, although limited to 2.1 million stars, has been used in many studies related to pulsating stars. Furthermore a set of 3,194 Cepheids and RR Lyrae stars with their times series have been released. Finally we present the plans for the ongoing study of variable phenomena with Gaia and highlight some of the possible impacts of the second data release on variable, and specifically, pulsating stars.

  4. On a New Theoretical Framework for RR Lyrae Stars. II. Mid-infrared Period–Luminosity–Metallicity Relations

    Energy Technology Data Exchange (ETDEWEB)

    Neeley, Jillian R.; Marengo, Massimo; Trueba, Nicolas [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Bono, Giuseppe; Braga, Vittorio F.; Magurno, Davide [Department of Physics, Università di Roma Tor Vergara, via della Ricerca Scientifica 1, I-00133 Roma (Italy); Dall’Ora, Massimo; Marconi, Marcella [INAF-Osservatorio Astronomico di Capodimonte, Salita Moiarello 16, I-80131 Napoli (Italy); Tognelli, Emanuele; Moroni, Pier G. Prada [Dipartimento di Fisica, Università di Pisa, Lago Bruno Pontecorvo 3, I-56127, Pisa (Italy); Beaton, Rachael L.; Madore, Barry F.; Seibert, Mark [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Freedman, Wendy L. [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States); Monson, Andrew J. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Scowcroft, Victoria [Department of Physics, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Stetson, Peter B., E-mail: jrneeley@iastate.edu [NRC-Herzberg, Dominion Astrophysical Observatory, 5071 West Saanich Road, Victoria BC V9E 2E7 (Canada)

    2017-06-01

    We present new theoretical period–luminosity–metallicity (PLZ) relations for RR Lyræ stars (RRLs) at Spitzer and WISE wavelengths. The PLZ relations were derived using nonlinear, time-dependent convective hydrodynamical models for a broad range of metal abundances ( Z = 0.0001–0.0198). In deriving the light curves, we tested two sets of atmospheric models and found no significant difference between the resulting mean magnitudes. We also compare our theoretical relations to empirical relations derived from RRLs in both the field and in the globular cluster M4. Our theoretical PLZ relations were combined with multi-wavelength observations to simultaneously fit the distance modulus, μ {sub 0}, and extinction, A {sub V}, of both the individual Galactic RRL and of the cluster M4. The results for the Galactic RRL are consistent with trigonometric parallax measurements from Gaia ’ s first data release. For M4, we find a distance modulus of μ {sub 0} = 11.257 ± 0.035 mag with A {sub V}= 1.45 ± 0.12 mag, which is consistent with measurements from other distance indicators. This analysis has shown that, when considering a sample covering a range of iron abundances, the metallicity spread introduces a dispersion in the PL relation on the order of 0.13 mag. However, if this metallicity component is accounted for in a PLZ relation, the dispersion is reduced to ∼0.02 mag at mid-infrared wavelengths.

  5. Pulsating star research and the Gaia revolution

    Directory of Open Access Journals (Sweden)

    Eyer Laurent

    2017-01-01

    Full Text Available In this article we present an overview of the ESA Gaia mission and of the unprecedented impact that Gaia will have on the field of variable star research. We summarise the contents and impact of the first Gaia data release on the description of variability phenomena, with particular emphasis on pulsating star research. The Tycho-Gaia astrometric solution, although limited to 2.1 million stars, has been used in many studies related to pulsating stars. Furthermore a set of 3,194 Cepheids and RR Lyrae stars with their times series have been released. Finally we present the plans for the ongoing study of variable phenomena with Gaia and highlight some of the possible impacts of the second data release on variable, and specifically, pulsating stars.

  6. On the RR Lyrae Stars in Globulars. V. The Complete Near-infrared (JHK s ) Census of ω Centauri RR Lyrae Variables

    Science.gov (United States)

    Braga, V. F.; Stetson, P. B.; Bono, G.; Dall’Ora, M.; Ferraro, I.; Fiorentino, G.; Iannicola, G.; Marconi, M.; Marengo, M.; Monson, A. J.; Neeley, J.; Persson, S. E.; Beaton, R. L.; Buonanno, R.; Calamida, A.; Castellani, M.; Di Carlo, E.; Fabrizio, M.; Freedman, W. L.; Inno, L.; Madore, B. F.; Magurno, D.; Marchetti, E.; Marinoni, S.; Marrese, P.; Matsunaga, N.; Minniti, D.; Monelli, M.; Nonino, M.; Piersimoni, A. M.; Pietrinferni, A.; Prada-Moroni, P.; Pulone, L.; Stellingwerf, R.; Tognelli, E.; Walker, A. R.; Valenti, E.; Zoccali, M.

    2018-03-01

    We present a new complete near-infrared (NIR, JHK s ) census of RR Lyrae stars (RRLs) in the globular ω Cen (NGC 5139). We collected 15,472 JHK s images with 4–8 m class telescopes over 15 years (2000–2015) covering a sky area around the cluster center of 60 × 34 arcmin2. These images provided calibrated photometry for 182 out of the 198 cluster RRL candidates with 10 to 60 measurements per band. We also provide new homogeneous estimates of the photometric amplitude for 180 (J), 176 (H) and 174 (K s ) RRLs. These data were supplemented with single-epoch JK s magnitudes from VHS and with single-epoch H magnitudes from 2MASS. Using proprietary optical and NIR data together with new optical light curves (ASAS-SN) we also updated pulsation periods for 59 candidate RRLs. As a whole, we provide JHK s magnitudes for 90 RRab (fundamentals), 103 RRc (first overtones) and one RRd (mixed-mode pulsator). We found that NIR/optical photometric amplitude ratios increase when moving from first overtone to fundamental and to long-period (P > 0.7 days) fundamental RRLs. Using predicted period–luminosity–metallicity relations, we derive a true distance modulus of 13.674 ± 0.008 ± 0.038 mag (statistical error and standard deviation of the median) based on spectroscopic iron abundances, and of 13.698 ± 0.004 ± 0.048 mag based on photometric iron abundances. We also found evidence of possible systematics at the 5%–10% level in the zero-point of the period–luminosity relations based on the five calibrating RRLs whose parallaxes had been determined with the HST. This publication makes use of data gathered with the Magellan/Baade Telescope at Las Campanas Observatory, the Blanco Telescope at Cerro Tololo Inter-American Observatory, NTT at La Silla (ESO Program IDs: 64.N-0038(A), 66.D-0557(A), 68.D-0545(A), 073.D-0313(A), ID 073.D-0313(A) and 59.A-9004(D)), VISTA at Paranal (ESO Program ID: 179.A-2010) and VLT at Paranal (ESO Program ID: ID96406).

  7. The MACHO Project 9 Million Star Color-Magnitude Diagram of the Large Magellanic Cloud

    International Nuclear Information System (INIS)

    Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Basu, A.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C.

    2000-01-01

    We present a 9 million star color-magnitude diagram (9M CMD) of the Large Magellanic Cloud (LMC) bar. The 9M CMD reveals a complex superposition of different-age and -metallicity stellar populations, with important stellar evolutionary phases occurring over 3 orders of magnitude in number density. First, we count the nonvariable red and blue supergiants and the associated Cepheid variables and measure the stellar effective temperatures defining the Cepheid instability strip. Lifetime predictions of stellar evolution theory are tested, with implications for the origin of low-luminosity Cepheids. The highly evolved asymptotic giant branch (AGB) stars in the 9M CMD have a bimodal distribution in brightness, which we interpret as discrete old populations ((greater-or-similar sign)1 Gyr). The faint AGB sequence may be metal-poor and very old. Comparing the mean properties of giant branch and horizontal-branch (HB) stars in the 9M CMD with those of clusters, we identify NGC 411 and M3 as templates for the admixture of old stellar populations in the bar. However, there are several indications that the old and metal-poor field population has a red HB morphology: the RR Lyrae variables lie preferentially on the red edge of the instability strip, the AGB bump is very red, and the ratio of AGB bump stars to RR Lyrae variables is quite large. If the HB second parameter is age, the old and metal-poor field population in the bar likely formed after the oldest LMC clusters. Lifetime predictions of stellar evolution theory lead us to associate a significant fraction of the ∼1 million red HB clump giants in the 9M CMD with the same old and metal-poor population producing the RR Lyrae stars and the AGB bump. In this case, compared with the age-dependent luminosity predictions of stellar evolution theory, the red HB clump is too bright relative to the RR Lyrae stars and AGB bump. Last, we show that the surface density profile of RR Lyrae variables is fitted by an exponential

  8. The MACHO Project 9 Million Star Color-Magnitude Diagram of the Large Magellanic Cloud

    Energy Technology Data Exchange (ETDEWEB)

    Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Basu, A.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C. (and others)

    2000-05-01

    We present a 9 million star color-magnitude diagram (9M CMD) of the Large Magellanic Cloud (LMC) bar. The 9M CMD reveals a complex superposition of different-age and -metallicity stellar populations, with important stellar evolutionary phases occurring over 3 orders of magnitude in number density. First, we count the nonvariable red and blue supergiants and the associated Cepheid variables and measure the stellar effective temperatures defining the Cepheid instability strip. Lifetime predictions of stellar evolution theory are tested, with implications for the origin of low-luminosity Cepheids. The highly evolved asymptotic giant branch (AGB) stars in the 9M CMD have a bimodal distribution in brightness, which we interpret as discrete old populations ((greater-or-similar sign)1 Gyr). The faint AGB sequence may be metal-poor and very old. Comparing the mean properties of giant branch and horizontal-branch (HB) stars in the 9M CMD with those of clusters, we identify NGC 411 and M3 as templates for the admixture of old stellar populations in the bar. However, there are several indications that the old and metal-poor field population has a red HB morphology: the RR Lyrae variables lie preferentially on the red edge of the instability strip, the AGB bump is very red, and the ratio of AGB bump stars to RR Lyrae variables is quite large. If the HB second parameter is age, the old and metal-poor field population in the bar likely formed after the oldest LMC clusters. Lifetime predictions of stellar evolution theory lead us to associate a significant fraction of the {approx}1 million red HB clump giants in the 9M CMD with the same old and metal-poor population producing the RR Lyrae stars and the AGB bump. In this case, compared with the age-dependent luminosity predictions of stellar evolution theory, the red HB clump is too bright relative to the RR Lyrae stars and AGB bump. Last, we show that the surface density profile of RR Lyrae variables is fitted by an exponential

  9. Variable Stars in Large Magellanic Cloud Globular Clusters. III. Reticulum

    Science.gov (United States)

    Kuehn, Charles A.; Dame, Kyra; Smith, Horace A.; Catelan, Márcio; Jeon, Young-Beom; Nemec, James M.; Walker, Alistair R.; Kunder, Andrea; Pritzl, Barton J.; De Lee, Nathan; Borissova, Jura

    2013-06-01

    This is the third in a series of papers studying the variable stars in old globular clusters in the Large Magellanic Cloud. The primary goal of this series is to look at how the characteristics and behavior of RR Lyrae stars in Oosterhoff-intermediate systems compare to those of their counterparts in Oosterhoff-I/II systems. In this paper we present the results of our new time-series BVI photometric study of the globular cluster Reticulum. We found a total of 32 variables stars (22 RRab, 4 RRc, and 6 RRd stars) in our field of view. We present photometric parameters and light curves for these stars. We also present physical properties, derived from Fourier analysis of light curves, for some of the RR Lyrae stars. We discuss the Oosterhoff classification of Reticulum and use our results to re-derive the distance modulus and age of the cluster. Based on observations taken with the SMARTS 1.3 m telescope operated by the SMARTS Consortium and observations taken at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

  10. Weak Galactic halo-Fornax dSph connection from RR Lyrae stars

    NARCIS (Netherlands)

    Fiorentino, G.; Monelli, M.; Stetson, P. B.; Bono, G.; Gallart, C.; Martínez-Vázquez, C. E.; Bernard, E. J.; Massari, D.; Braga, V. F.; Dall'Ora, M.

    2017-01-01

    Aims: For the first time accurate pulsation properties of the ancient variable stars of the Fornax dwarf spheroidal galaxy (dSph) are discussed in the broad context of galaxy formation and evolution. Methods: Homogeneous multi-band BVI optical photometry of spanning twenty years has allowed us to

  11. Circumstellar H2O maser emission associated with four late-type stars

    International Nuclear Information System (INIS)

    Johnston, K.J.; Spencer, J.H.; Bowers, P.F.

    1985-01-01

    The positions and structure of H2O maser associated with four long-period stars were measured using the VLA, and the results are discussed. The four stars observed were: RX Boo; R Aq1; RR Aq1; and NML Cyg. The spatial resolution of the VLA measurements was 0.07 arcsec. The H2O maser emission features appear as unresolved knots distributed over an area of no more than 0.4 arcsec. The velocity and spatial characteristics of the maser regions in R Aq1 and RR Aq1 were found to change considerably over time. The estimated sizes of the H2O maser emission were 8 x 10 to the 14th for RX Boo, R Aq1, and RR Aq1. The supergiant star NML Cyg had the largest maser region (10 to the 16th) which is comparable to that of VY CMa. The positional accuracy for individual maser features ranged between 0.03 and 0.09 arcsec. However, the precise location of the maser emission relative to the stellar photocenter did not fit the velocity and spatial distributions of the emission and therefore may be inappropriate as a standard for comparisons of stellar reference frames. 20 references

  12. Variable Stars in (Not Only) Dwarf Galaxies : Key Tools to Constrain Distances and Stellar Content

    NARCIS (Netherlands)

    Fiorentino, G.; Koleva, M; Prugniel, P; Vauglin,

    2011-01-01

    The important role of Cepheid and RR Lyrae variable stars and what they teach us about dwarf galaxies is discussed. Despite ever improving star formation histories of Local Group dwarf galaxies uncertainties remain, in particular in the identification and characterisation of the oldest stellar

  13. Variable Stars in Large Magellanic Cloud Globular Clusters. II. NGC 1786

    Science.gov (United States)

    Kuehn, Charles A.; Smith, Horace A.; Catelan, Márcio; Pritzl, Barton J.; De Lee, Nathan; Borissova, Jura

    2012-12-01

    This is the second in a series of papers studying the variable stars in Large Magellanic Cloud globular clusters. The primary goal of this series is to study how RR Lyrae stars in Oosterhoff-intermediate systems compare to their counterparts in Oosterhoff I/II systems. In this paper, we present the results of our new time-series B-V photometric study of the globular cluster NGC 1786. A total of 65 variable stars were identified in our field of view. These variables include 53 RR Lyraes (27 RRab, 18 RRc, and 8 RRd), 3 classical Cepheids, 1 Type II Cepheid, 1 Anomalous Cepheid, 2 eclipsing binaries, 3 Delta Scuti/SX Phoenicis variables, and 2 variables of undetermined type. Photometric parameters for these variables are presented. We present physical properties for some of the RR Lyrae stars, derived from Fourier analysis of their light curves. We discuss several different indicators of Oosterhoff type which indicate that the Oosterhoff classification of NGC 1786 is not as clear cut as what is seen in most globular clusters. Based on observations taken with the SMARTS 1.3 m telescope operated by the SMARTS Consortium and observations taken at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

  14. A NEW CENSUS OF THE VARIABLE STAR POPULATION IN THE GLOBULAR CLUSTER NGC 2419

    International Nuclear Information System (INIS)

    Di Criscienzo, M.; Greco, C.; Ripepi, V.; Dall' Ora, M.; Marconi, M.; Musella, I.; Clementini, G.; Federici, L.; Di Fabrizio, L.

    2011-01-01

    We present B, V, and I CCD light curves for 101 variable stars belonging to the globular cluster NGC 2419, 60 of which are new discoveries, based on data sets obtained at the Telescopio Nazionale Galileo, the Subaru telescope, and the Hubble Space Telescope. The sample includes 75 RR Lyrae stars (38 RRab, 36 RRc, and one RRd), one Population II Cepheid, 12 SX Phoenicis variables, two δ Scuti stars, three binary systems, five long-period variables, and three variables of uncertain classification. The pulsation properties of the RR Lyrae variables are close to those of Oosterhoff type II clusters, consistent with the low metal abundance and the cluster horizontal branch morphology, disfavoring (but not totally ruling out) an extragalactic hypothesis for the origin of NGC 2419. The observed properties of RR Lyrae and SX Phoenicis stars are used to estimate the cluster reddening and distance, using a number of different methods. Our final value is μ 0 (NGC 2419) = 19.71 ± 0.08 mag (D = 87.5 ± 3.3 kpc), with E(B - V) = 0.08 ± 0.01 mag, [Fe/H] = -2.1 dex on the Zinn and West metallicity scale, and a value of M V that sets μ 0 (LMC) = 18.52 mag. This value is in good agreement with the most recent literature estimates of the distance to NGC 2419.

  15. The WFCAM multiwavelength Variable Star Catalog

    Science.gov (United States)

    Ferreira Lopes, C. E.; Dékány, I.; Catelan, M.; Cross, N. J. G.; Angeloni, R.; Leão, I. C.; De Medeiros, J. R.

    2015-01-01

    Context. Stellar variability in the near-infrared (NIR) remains largely unexplored. The exploitation of public science archives with data-mining methods offers a perspective for a time-domain exploration of the NIR sky. Aims: We perform a comprehensive search for stellar variability using the optical-NIR multiband photometric data in the public Calibration Database of the WFCAM Science Archive (WSA), with the aim of contributing to the general census of variable stars and of extending the current scarce inventory of accurate NIR light curves for a number of variable star classes. Methods: Standard data-mining methods were applied to extract and fine-tune time-series data from the WSA. We introduced new variability indices designed for multiband data with correlated sampling, and applied them for preselecting variable star candidates, i.e., light curves that are dominated by correlated variations, from noise-dominated ones. Preselection criteria were established by robust numerical tests for evaluating the response of variability indices to the colored noise characteristic of the data. We performed a period search using the string-length minimization method on an initial catalog of 6551 variable star candidates preselected by variability indices. Further frequency analysis was performed on positive candidates using three additional methods in combination, in order to cope with aliasing. Results: We find 275 periodic variable stars and an additional 44 objects with suspected variability with uncertain periods or apparently aperiodic variation. Only 44 of these objects had been previously known, including 11 RR Lyrae stars on the outskirts of the globular cluster M 3 (NGC 5272). We provide a preliminary classification of the new variable stars that have well-measured light curves, but the variability types of a large number of objects remain ambiguous. We classify most of the new variables as contact binary stars, but we also find several pulsating stars, among which

  16. Dwarf spheroidal satellites of M31. I. Variable stars and stellar populations in Andromeda XIX

    Energy Technology Data Exchange (ETDEWEB)

    Cusano, Felice; Clementini, Gisella; Garofalo, Alessia; Federici, Luciana, E-mail: felice.cusano@oabo.inaf.it, E-mail: gisella.clementini@oabo.inaf.it, E-mail: luciana.federici@oabo.inaf.it, E-mail: alessia.garofalo@studio.unibo.it [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); and others

    2013-12-10

    We present B, V time-series photometry of Andromeda XIX (And XIX), the most extended (half-light radius of 6.'2) of Andromeda's dwarf spheroidal companions, which we observed with the Large Binocular Cameras at the Large Binocular Telescope. We surveyed a 23' × 23' area centered on And XIX and present the deepest color-magnitude diagram (CMD) ever obtained for this galaxy, reaching, at V ∼ 26.3 mag, about one magnitude below the horizontal branch (HB). The CMD shows a prominent and slightly widened red giant branch, along with a predominantly red HB, which extends to the blue to significantly populate the classical instability strip. We have identified 39 pulsating variable stars, of which 31 are of RR Lyrae type and 8 are Anomalous Cepheids (ACs). Twelve of the RR Lyrae variables and three of the ACs are located within And XIX's half light radius. The average period of the fundamental mode RR Lyrae stars ((P {sub ab}) = 0.62 days, σ = 0.03 days) and the period-amplitude diagram qualify And XIX as an Oosterhoff-Intermediate system. From the average luminosity of the RR Lyrae stars ((V(RR)) = 25.34 mag, σ = 0.10 mag), we determine a distance modulus of (m – M){sub 0} = 24.52 ± 0.23 mag in a scale where the distance to the Large Magellanic Cloud (LMC) is 18.5 ± 0.1 mag. The ACs follow a well-defined Period-Wesenheit (PW) relation that appears to be in very good agreement with the PW relationship defined by the ACs in the LMC.

  17. The occurrence of binary evolution pulsators in classical instability strip of RR Lyrae and Cepheid variables

    Science.gov (United States)

    Karczmarek, P.; Wiktorowicz, G.; Iłkiewicz, K.; Smolec, R.; Stępień, K.; Pietrzyński, G.; Gieren, W.; Belczynski, K.

    2017-04-01

    Single star evolution does not allow extremely low-mass stars to cross the classical instability strip (IS) during the Hubble time. However, within binary evolution framework low-mass stars can appear inside the IS once the mass transfer (MT) is taken into account. Triggered by a discovery of low-mass (0.26 M⊙) RR Lyrae-like variable in a binary system, OGLE-BLG-RRLYR-02792, we investigate the occurrence of similar binary components in the IS, which set up a new class of low-mass pulsators. They are referred to as binary evolution pulsators (BEPs) to underline the interaction between components, which is crucial for substantial mass-loss prior to the IS entrance. We simulate a population of 500 000 metal-rich binaries and report that 28 143 components of binary systems experience severe MT (losing up to 90 per cent of mass), followed by at least one IS crossing in luminosity range of RR Lyrae (RRL) or Cepheid variables. A half of these systems enter the IS before the age of 4 Gyr. BEPs display a variety of physical and orbital parameters, with the most important being the BEP mass in range 0.2-0.8 M⊙, and the orbital period in range 10-2 500 d. Based on the light curve only, BEPs can be misclassified as genuine classical pulsators, and as such they would contaminate genuine RRL and classical Cepheid variables at levels of 0.8 and 5 per cent, respectively. We state that the majority of BEPs will remain undetected and we discuss relevant detection limitations.

  18. Faint (and bright variable stars in the satellites of the Milky Way

    Directory of Open Access Journals (Sweden)

    Vivas A. Katherina

    2017-01-01

    Full Text Available I describe two ongoing projects related with variable stars in the satellites of the MilkyWay. In the first project, we are searching for dwarf Cepheid stars (a.k.a δ Scuti and/or SX Phe in some of the classical dwarf spheroidal galaxies. Our goal is to characterize the population of these variable stars under different environments (age, metallicity in order to study their use as standard candles in systems for which the metallicity is not necessarily known. In the second project we search for RR Lyrae stars in the new ultra-faint satellite galaxies that have been discovered around the Milky Way in recent years.

  19. Variable stars in the VVV globular clusters. I. 2MASS-GC 02 and Terzan 10

    Energy Technology Data Exchange (ETDEWEB)

    Alonso-García, Javier; Dékány, István; Catelan, Márcio; Ramos, Rodrigo Contreras; Gran, Felipe; Leyton, Paul; Minniti, Dante [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago (Chile); Amigo, Pía, E-mail: jalonso@astro.puc.cl, E-mail: idekany@astro.puc.cl, E-mail: mcatelan@astro.puc.cl, E-mail: rcontrer@astro.puc.cl, E-mail: fgran@astro.puc.cl, E-mail: pia.amigo@uv.cl, E-mail: pleyton@astro.puc.cl, E-mail: dante@astrofisica.cl [Millennium Institute of Astrophysics, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago (Chile)

    2015-03-01

    The VISTA Variables in the Vía Láctea (VVV) ESO Public Survey is opening a new window to study inner Galactic globular clusters (GCs) using their variable stars. These GCs have been neglected in the past due to the difficulties caused by the presence of elevated extinction and high field stellar densities in their lines of sight. However, the discovery and study of any present variables in these clusters, especially RR Lyrae stars, can help to greatly improve the accuracy of their physical parameters. It can also help to shed some light on the questions raised by the intriguing Oosterhoff dichotomy in the Galactic GC system. In a series of papers we plan to explore variable stars in the GCs falling inside the field of the VVV survey. In this first paper, we search for and study the variables present in two highly reddened, moderately metal-poor, faint, inner Galactic GCs: 2MASS-GC 02 and Terzan 10. We report the discovery of sizable populations of RR Lyrae stars in both GCs. We use near-infrared period–luminosity relations to determine the color excess of each RR Lyrae star, from which we obtain both accurate distances to the GCs and the ratios of the selective-to-total extinction in their directions. We find the extinction toward both clusters to be elevated, non-standard, and highly differential. We also find both clusters to be closer to the Galactic center than previously thought, with Terzan 10 being on the far side of the Galactic bulge. Finally, we discuss their Oosterhoff properties, and conclude that both clusters stand out from the dichotomy followed by most Galactic GCs.

  20. Field #3 of the Palomar-Groningen Survey; 1, Variable stars at the edge of the Sagittarius dwarf galaxy

    NARCIS (Netherlands)

    Schultheis, M.

    1996-01-01

    Submitted to: Astron. Astrophys. Abstract: A catalogue is presented with variable (RR Lyrae, semiregular and Mira) stars located inside field #3 of the Palomar-Groningen Survey, at the outer edge of the Sagittarius dwarf galaxy. One of the semiregular variables is a carbon star, comparable with

  1. The Variable Stars of the Draco Dwarf Spheroidal Galaxy: Revisited

    Science.gov (United States)

    Kinemuchi, K.; Harris, H. C.; Smith, Horace A.; Silbermann, N. A.; Snyder, L. A.; La Cluyzé, A. P.; Clark, C. L.

    2008-11-01

    We present a CCD survey of variable stars in the Draco dwarf spheroidal galaxy. This survey, which has the largest areal coverage since the original variable star survey by Baade & Swope, includes photometry for 270 RR Lyrae (RRL) stars, 9 anomalous Cepheids (ACs), 2 eclipsing binaries, and 12 slow, irregular red variables, as well as 30 background QSOs. Twenty-six probable double-mode RRL stars were identified. Observed parameters, including mean V and I magnitudes, V amplitudes, and periods, have been derived. Photometric metallicities of the ab-type RRL stars were calculated according to the method of Jurcsik & Kovacs, yielding a mean metallicity of lang[Fe/H]rang = -2.19 ± 0.03. The well-known Oosterhoff intermediate nature of the RRL stars in Draco is reconfirmed, although the double-mode RRL stars, with one exception, have properties similar to those found in Oosterhoff type II globular clusters. The period-luminosity relation of the ACs is rediscussed with the addition of the new Draco ACs.

  2. A new method of measuring centre-of-mass velocities of radially pulsating stars from high-resolution spectroscopy

    Science.gov (United States)

    Britavskiy, N.; Pancino, E.; Tsymbal, V.; Romano, D.; Fossati, L.

    2018-03-01

    We present a radial velocity analysis of 20 solar neighbourhood RR Lyrae and three Population II Cepheid variables. We obtained high-resolution, moderate-to-high signal-to-noise ratio spectra for most stars; these spectra covered different pulsation phases for each star. To estimate the gamma (centre-of-mass) velocities of the programme stars, we use two independent methods. The first, `classic' method is based on RR Lyrae radial velocity curve templates. The second method is based on the analysis of absorption-line profile asymmetry to determine both pulsational and gamma velocities. This second method is based on the least-squares deconvolution (LSD) technique applied to analyse the line asymmetry that occurs in the spectra. We obtain measurements of the pulsation component of the radial velocity with an accuracy of ±3.5 km s-1. The gamma velocity was determined with an accuracy of ±10 km s-1, even for those stars having a small number of spectra. The main advantage of this method is the possibility of obtaining an estimation of gamma velocity even from one spectroscopic observation with uncertain pulsation phase. A detailed investigation of LSD profile asymmetry shows that the projection factor p varies as a function of the pulsation phase - this is a key parameter, which converts observed spectral line radial velocity variations into photospheric pulsation velocities. As a by-product of our study, we present 41 densely spaced synthetic grids of LSD profile bisectors based on atmospheric models of RR Lyr covering all pulsation phases.

  3. Method of LSD profile asymmetry for estimating the center of mass velocities of pulsating stars

    Science.gov (United States)

    Britavskiy, N.; Pancino, E.; Tsymbal, V.; Romano, D.; Cacciari, C.; Clementini, C.

    2016-05-01

    We present radial velocity analysis for 20 solar neighborhood RR Lyrae and 3 Population II Cepheids. High-resolution spectra were observed with either TNG/SARG or VLT/UVES over varying phases. To estimate the center of mass (barycentric) velocities of the program stars, we utilized two independent methods. First, the 'classic' method was employed, which is based on RR Lyrae radial velocity curve templates. Second, we provide the new method that used absorption line profile asymmetry to determine both the pulsation and the barycentric velocities even with a low number of high-resolution spectra and in cases where the phase of the observations is uncertain. This new method is based on a least squares deconvolution (LSD) of the line profiles in order to an- alyze line asymmetry that occurs in the spectra of pulsating stars. By applying this method to our sample stars we attain accurate measurements (+- 2 kms^-1) of the pulsation component of the radial velocity. This results in determination of the barycentric velocity to within 5 kms^-1 even with a low number of high- resolution spectra. A detailed investigation of LSD profile asymmetry shows the variable nature of the project factor at different pulsation phases, which should be taken into account in the detailed spectroscopic analysis of pulsating stars.

  4. Adsorção dos corantes RO16, RR2 e RR141 utilizando lodo residual da indústria têxtil Adsorption of dyes RO16, RR2 and RR141 using residual sludge of textile industry

    Directory of Open Access Journals (Sweden)

    Andressa Regina Vasques

    2011-09-01

    Full Text Available A adsorção é uma das técnicas empregadas com sucesso para remoção efetiva da cor presente em efluentes têxteis. Com o objetivo de avaliar os diferentes parâmetros adsortivos, bem como determinar a eficiência de um adsorvente alternativo desenvolvido a partir de lodo residual têxtil na remoção de corantes, foram determinadas curvas de cinética de adsorção e isotermas. Por meio dos dados cinéticos e de equilíbrio obtidos, verificou-se que a 25ºC a adsorção foi favorável para todos os corantes, sendo esta a melhor condição para os corantes RO16 e RR2 na ausência de sais. Para o corante RR141, a adição de NaCl aumentou a capacidade de adsorção do adsorvente no equilíbrio e a adição de Na2SO4 favoreceu a adsorção para o corante RO16, ao contrário do que se observou para os outros dois corantes. A quantidade máxima de corante adsorvida por unidade de massa de adsorvente (q max nas melhores condições adsortivas para os corantes RO16, RR2 e RR141 foi de 81,30, 53,48 e 78,74 mg.g-1, respectivamente.The adsorption is one of the techniques that have been successfully used for effective removal of the dyes present in textile effluents. With the objective to evaluate the different adsorptive parameters, as well as determining the efficiency of one alternative adsorbent in the removal of dyes, kinetics and equilibrium data of adsorption were determined. By the kinetic data and of equilibrium, it was verified that the adsorption was favorable for all the dyes in 25ºC, being the best condition for the dye RO16 and RR2 in the total absence of salt. For the dye RR141, the addition of NaCl increased the adsorption capacity of adsorbent in the equilibrium and the addition of Na2SO4 favored the adsorption for the dye RO16, in contrast to what was observed for the two other dyes. The maximum quantity of dye adsorbed per unit mass of adsorbent (q max in the best adsorptive conditions for the dyes RO16, RR2 and RR141 was of 81

  5. VizieR Online Data Catalog: Standard Galactic field RR Lyrae. I. Photometry (Monson+, 2017)

    Science.gov (United States)

    Monson, A. J.; Beaton, R. L.; Scowcroft, V.; Freedman, W. L.; Madore, B. F.; Rich, J. A.; Seibert, M.; Kollmeier, J. A.; Clementini, G.

    2017-06-01

    The Three-hundred MilliMeter Telescope (TMMT) is a fully robotic, 300mm telescope at Las Campanas Observatory (LCO), for which the nightly operation and data processing have been completely automated. Over the course of two years data were collected on 179 individual nights for our sample of the 55 RR Lyrae in the B, V, and IC broadband filters. Of these nights, 76 were under photometric conditions and calibrated directly. The 103 nonphotometric nights were roughly calibrated by using the default transformation equations, but only provide differential photometry relative to the calibrated frames. This resulted in 59698 final individual observations. Individual data points have a typical photometric precision of 0.02mag. The statistical error falls rapidly with hundreds of observations, with the zero-point uncertainties being the largest source of uncertainty in the final reported mean magnitude. To compare the results of our TMMT campaign to previous studies of these RR Lyrae (RRL) and to fill gaps in our TMMT phase coverage, we have compiled available broadband data from literature published over the past 30 years and spanning our full wavelength coverage (0.4 to 4.5μm) from the optical to mid-infrared. We have homogenized these diverse data sets to the following filter systems: Johnson UBV, Kron-Cousins RI, 2MASS J,H,Ks, and Spitzer [3.6], [4.5]. The All Sky Automated Survey (ASAS; http://www.astrouw.edu.pl/asas/) is a long-term project monitoring all stars brighter than V~14mag. The program covers both hemispheres, with telescopes at Las Campanas Observatory in Chile and Haleakala on Maui, both of which provide simultaneous I and V photometry. The GEOS RR Lyr Survey (http://www.ast.obs-mip.fr/users/leborgne/dbRR/grrs.html) is a long-term program utilizing TAROT (http://tarot.obs-hp.fr/) at Calern Observatory (Nice University, France). Annual data releases from this project add times for maximum light for program stars over the last year of observations. In

  6. Chemical Composition of RR Lyn - an Eclipsing Binary System with Am and λ Boo Type Components

    Science.gov (United States)

    Jeong, Yeuncheol; Yushchenko, Alexander V.; Doikov, Dmytry N.; Gopka, Vira F.; Yushchenko, Volodymyr O.

    2017-06-01

    High-resolution spectroscopic observations of the eclipsing binary system RR Lyn were made using the 1.8 m telescope at the Bohuynsan Optical Astronomical Observatory in Korea. The spectral resolving power was R = 82,000, with a signal to noise ratio of S/N > 150. We found the effective temperatures and surface gravities of the primary and secondary components to be equal to Teff = 7,920 & 7,210 K and log(g) = 3.80 & 4.16, respectively. The abundances of 34 and 17 different chemical elements were found in the atmospheric components. Correlations between the derived abundances with condensation temperatures and the second ionization potentials of these elements are discussed. The primary component is a typical metallic line star with the abundances of light and iron group elements close to solar values, while elements with atomic numbers Z > 30 are overabundant by 0.5-1.5 dex with respect to solar values. The secondary component is a λ Boo type star. In this type of stars, CNO abundances are close to solar values, while the abundance pattern shows a negative correlation with condensation temperatures.

  7. The first all-sky view of the Milky Way stellar halo with Gaia+2MASS RR Lyrae

    Science.gov (United States)

    Iorio, G.; Belokurov, V.; Erkal, D.; Koposov, S. E.; Nipoti, C.; Fraternali, F.

    2018-02-01

    We exploit the first Gaia data release to study the properties of the Galactic stellar halo as traced by RR Lyrae. We demonstrate that it is possible to select a pure sample of RR Lyrae using only photometric information available in the Gaia+2MASS catalogue. The final sample contains about 21 600 RR Lyrae covering an unprecedented fraction ( ˜ 60 per cent) of the volume of the Galactic inner halo (R < 28 kpc). We study the morphology of the stellar halo by analysing the RR Lyrae distribution with parametric and non-parametric techniques. Taking advantage of the uniform all-sky coverage, we test halo models more sophisticated than usually considered in the literature, such as those with varying flattening, tilts and/or offset of the halo with respect to the Galactic disc. A consistent picture emerges: the inner halo is well reproduced by a smooth distribution of stars settled on triaxial density ellipsoids. The shortest axis is perpendicular to the Milky Way's disc, while the longest axis forms an angle of ˜70° with the axis connecting the Sun and the Galactic Centre. The elongation along the major axis is mild (p = 1.27), and the vertical flattening is shown to evolve from a squashed state with q ≈ 0.57 in the centre to a more spherical q ≈ 0.75 at the outer edge of our data set. Within the radial range probed, the density profile of the stellar halo is well approximated by a single power law with exponent α = -2.96. We do not find evidence of tilt or offset of the halo with respect to the Galaxy's disc.

  8. Chemical Composition of RR Lyn – an Eclipsing Binary System with Am and λ Boo Type Components

    Directory of Open Access Journals (Sweden)

    Yeuncheol Jeong

    2017-06-01

    Full Text Available High-resolution spectroscopic observations of the eclipsing binary system RR Lyn were made using the 1.8 m telescope at the Bohuynsan Optical Astronomical Observatory in Korea. The spectral resolving power was R = 82,000, with a signal to noise ratio of S/N > 150. We found the effective temperatures and surface gravities of the primary and secondary components to be equal to Teff = 7,920 & 7,210 K and log(g = 3.80 & 4.16, respectively. The abundances of 34 and 17 different chemical elements were found in the atmospheric components. Correlations between the derived abundances with condensation temperatures and the second ionization potentials of these elements are discussed. The primary component is a typical metallic line star with the abundances of light and iron group elements close to solar values, while elements with atomic numbers Z > 30 are overabundant by 0.5–1.5 dex with respect to solar values. The secondary component is a λ Boo type star. In this type of stars, CNO abundances are close to solar values, while the abundance pattern shows a negative correlation with condensation temperatures.

  9. Variable Stars in the M31 Dwarf Spheroidal Companion Cassiopeia

    Science.gov (United States)

    Pritzl, Barton J.; Armandroff, T. E.; Jacoby, G. H.; Da Costa, G. S.

    2007-12-01

    Dwarf spheroidal galaxies show very diverse star formation histories. For the Galactic dwarf spheroidal galaxies, a correlation exists between Galactocentric distance and the prominence of intermediate-age ( 2 - 10 Gyr) populations. To test whether this correlation exists for the M31 dwarf spheroidal galaxies, we observed the Cassiopeia (And VII) dwarf galaxy, which is one of the most distant M31 dwarf spheroidal galaxies. We will present the results of a variable star search using HST/ACS data, along with a preliminary color-magnitude diagram. From the RR Lyrae stars we can obtain an independent distance and metallicity estimate for the dwarf galaxy. These results will be compared to those found for the other M31 dwarf spheroidal galaxies.This research is supported in part by NASA through grant number GO-11081.11 from the Space Telescope Science Institute.

  10. A RE-EVALUATION OF THE EVOLVED STARS IN THE GLOBULAR CLUSTER M13

    International Nuclear Information System (INIS)

    Sandquist, Eric L.; Gordon, Mark; Levine, Daniel; Bolte, Michael

    2010-01-01

    We have analyzed photometry from space- and ground-based cameras to identify all bright red giant branch (RGB), horizontal branch (HB), and asymptotic giant branch (AGB) stars within 10' of the center of the globular cluster M13. We identify a modest (7%) population of HB stars redder than the primary peak (including RR Lyrae variables at the blue end of the instability strip) that is somewhat more concentrated to the cluster core than the rest of the evolved stars. We find support for the idea that they are noticeably evolved and in the late stages of depleting helium in their cores. This resolves a disagreement between distance moduli derived from the tip of the RGB and from stars in or near the RR Lyrae instability strip. We identified disagreements between HB model sets on whether stars with T eff ∼ eff ∼ eff ∼ 22, 000 K) as previously suggested. These stars are brighter than other stars of similar color (either redder or bluer), and may be examples of 'early hot flashers' that ignite core helium fusion shortly after leaving the RGB. We used ultraviolet photometry to identify hot post-HB stars, and based on their numbers (relative to canonical AGB stars) we estimate the position on the HB where the morphology of the post-HB tracks change to I ∼ 17.3, between the two peaks in the HB distribution. Concerning the possibility of helium enrichment in M13, we revisited the helium-sensitive R ratio, applying a new method for correcting star counts for larger lifetimes of hot HB stars. We find that M13's R ratio is in agreement with theoretical values for primordial helium abundance Y P = 0.245 and inconsistent with a helium enhancement ΔY = 0.04. The brightness of the HB (both in comparison to the end of the canonical HB and to the tip of the RGB) also appears to rule out the idea that the envelopes of the reddest HB stars have been significantly enriched in helium. The absolute colors of the turnoffs of M3 and M13 potentially may be used to look for

  11. A COMPREHENSIVE, WIDE-FIELD STUDY OF PULSATING STARS IN THE CARINA DWARF SPHEROIDAL GALAXY

    Energy Technology Data Exchange (ETDEWEB)

    Vivas, A. Katherina [Centro de Investigaciones de Astronomía (CIDA), Apartado Postal 264, Mérida 5101-A (Venezuela, Bolivarian Republic of); Mateo, Mario, E-mail: akvivas@cida.ve, E-mail: mmateo@umich.edu [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States)

    2013-12-01

    We report the detection of 388 pulsating variable stars (and some additional miscellaneous variables) in the Carina dwarf spheroidal galaxy over an area covering the full visible extent of the galaxy and extending a few times beyond its photometric (King) tidal radius along the direction of its major axis. Included in this total are 340 newly discovered dwarf Cepheids (DCs), which are mostly located ∼2.5 mag below the horizontal branch and have very short periods (<0.1 days), typical of their class and consistent with their location on the upper part of the extended main sequence of the younger populations of the galaxy. Several extra-tidal DCs were found in our survey up to a distance of ∼1° from the center of Carina. Our sample also includes RR Lyrae stars and anomalous Cepheids, some of which were found outside the galaxy's tidal radius as well. This supports past works that suggest that Carina is undergoing tidal disruption. We use the period-luminosity relationship for DCs to estimate a distance modulus of μ{sub 0} = 20.17 ± 0.10 mag, in very good agreement with the estimate from RR Lyrae stars. We find some important differences in the properties of the DCs of Carina and those in Fornax and the LMC, the only extragalactic samples of DCs currently known. These differences may reflect a metallicity spread, depth along the line of sight, and/or different evolutionary paths of the DC stars.

  12. RR-Interval variance of electrocardiogram for atrial fibrillation detection

    Science.gov (United States)

    Nuryani, N.; Solikhah, M.; Nugoho, A. S.; Afdala, A.; Anzihory, E.

    2016-11-01

    Atrial fibrillation is a serious heart problem originated from the upper chamber of the heart. The common indication of atrial fibrillation is irregularity of R peak-to-R-peak time interval, which is shortly called RR interval. The irregularity could be represented using variance or spread of RR interval. This article presents a system to detect atrial fibrillation using variances. Using clinical data of patients with atrial fibrillation attack, it is shown that the variance of electrocardiographic RR interval are higher during atrial fibrillation, compared to the normal one. Utilizing a simple detection technique and variances of RR intervals, we find a good performance of atrial fibrillation detection.

  13. Type II Cepheids: evidence for Na-O anticorrelation for BL Her type stars?

    Science.gov (United States)

    Kovtyukh, V.; Yegorova, I.; Andrievsky, S.; Korotin, S.; Saviane, I.; Lemasle, B.; Chekhonadskikh, F.; Belik, S.

    2018-06-01

    The chemical composition of 28 Population II Cepheids and one RR Lyrae variable has been studied using high-resolution spectra. The chemical composition of W Vir variable stars (with periods longer than 8 d) is typical for the halo and thick disc stars. However, the chemical composition of BL Her variables (with periods of 0.8-4 d) is drastically different, although it does not differ essentially from that of the stars belonging to globular clusters. In particular, the sodium overabundance ([Na/Fe] ≈ 0.4) is reported for most of these stars, and the Na-O anticorrelation is also possible. The evolutionary tracks for BL Her variables (with a progenitor mass value of 0.8 solar masses) indicate that mostly helium-overabundant stars (Y = 0.30-0.35) can fall into the instability strip region. We suppose that it is the helium overabundance that accounts not only for the existence of BL Her variable stars but also for the observed abnormalities in the chemical composition of this small group of pulsating variables.

  14. The Taiwanese-American occultation survey project stellar variability. III. Detection of 58 new variable stars

    Energy Technology Data Exchange (ETDEWEB)

    Ishioka, R.; Wang, S.-Y.; Zhang, Z.-W.; Lehner, M. J.; Cook, K. H.; King, S.-K.; Lee, T.; Marshall, S. L.; Schwamb, M. E.; Wang, J.-H.; Wen, C.-Y. [Institute of Astronomy and Astrophysics, Academia Sinica, 11F of Astronomy-Mathematics Building, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan (China); Alcock, C.; Protopapas, P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Axelrod, T. [Steward Observatory, 933 North Cherry Avenue, Room N204, Tucson, AZ 85721 (United States); Bianco, F. B. [Center for Cosmology and Particle Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Byun, Y.-I. [Department of Astronomy and University Observatory, Yonsei University, 134 Shinchon, Seoul 120-749 (Korea, Republic of); Chen, W. P.; Ngeow, C.-C. [Institute of Astronomy, National Central University, No. 300, Jhongda Road, Jhongli City, Taoyuan County 320, Taiwan (China); Kim, D.-W. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Rice, J. A., E-mail: ishioka@asiaa.sinica.edu.tw [Department of Statistics, University of California Berkeley, 367 Evans Hall, Berkeley, CA 94720 (United States)

    2014-04-01

    The Taiwanese-American Occultation Survey project is designed for the detection of stellar occultations by small-size Kuiper Belt Objects, and it has monitored selected fields along the ecliptic plane by using four telescopes with a 3 deg{sup 2} field of view on the sky since 2005. We have analyzed data accumulated during 2005-2012 to detect variable stars. Sixteen fields with observations of more than 100 epochs were examined. We recovered 85 variables among a total of 158 known variable stars in these 16 fields. Most of the unrecovered variables are located in the fields observed less frequently. We also detected 58 variable stars which are not listed in the International Variable Star Index of the American Association of Variable Star Observers. These variable stars are classified as 3 RR Lyrae, 4 Cepheid, 1 δ Scuti, 5 Mira, 15 semi-regular, and 27 eclipsing binaries based on the periodicity and the profile of the light curves.

  15. IDAS-RR: an incident data base system for research reactors

    International Nuclear Information System (INIS)

    Matsumoto, Kiyoshi; Kohsaka, Atsuo; Kaminaga, Masanori; Murayama, Youji; Ohnishi, Nobuaki; Maniwa, Masaki.

    1990-03-01

    An Incident Data Base System for Research Reactors, IDAS-RR, has been developed. IDAS-RR has information about abnormal incidents (failures, transients, accidents, etc.) of research reactors in the world. Data reference, input, editing and other functions of IDAS-RR are menu driven. The routine processing and data base management functions are performed by the system software and hardware. PC-9801 equipment was selected as the hardware because of its portability and popularity. IDAS-RR provides effective reference information for the following activities. 1) Analysis of abnormal incident of research reactors, 2) Detail analysis of research reactor behavior in the abnormal incident for building the knowledge base of the reactor emergency diagnostic system for research reactor, 3) Planning counter-measure for emergency situation in the research reactor. This report is a user's manual of IDAS-RR. (author)

  16. Ventricular Cycle Length Characteristics Estimative of Prolonged RR Interval during Atrial Fibrillation

    Science.gov (United States)

    CIACCIO, EDWARD J.; BIVIANO, ANGELO B.; GAMBHIR, ALOK; EINSTEIN, ANDREW J.; GARAN, HASAN

    2014-01-01

    Background When atrial fibrillation (AF) is incessant, imaging during a prolonged ventricular RR interval may improve image quality. It was hypothesized that long RR intervals could be predicted from preceding RR values. Methods From the PhysioNet database, electrocardiogram RR intervals were obtained from 74 persistent AF patients. An RR interval lengthened by at least 250 ms beyond the immediately preceding RR interval (termed T0 and T1, respectively) was considered prolonged. A two-parameter scatterplot was used to predict the occurrence of a prolonged interval T0. The scatterplot parameters were: (1) RR variability (RRv) estimated as the average second derivative from 10 previous pairs of RR differences, T13–T2, and (2) Tm–T1, the difference between Tm, the mean from T13 to T2, and T1. For each patient, scatterplots were constructed using preliminary data from the first hour. The ranges of parameters 1 and 2 were adjusted to maximize the proportion of prolonged RR intervals within range. These constraints were used for prediction of prolonged RR in test data collected during the second hour. Results The mean prolonged event was 1.0 seconds in duration. Actual prolonged events were identified with a mean positive predictive value (PPV) of 80% in the test set. PPV was >80% in 36 of 74 patients. An average of 10.8 prolonged RR intervals per 60 minutes was correctly identified. Conclusions A method was developed to predict prolonged RR intervals using two parameters and prior statistical sampling for each patient. This or similar methodology may help improve cardiac imaging in many longstanding persistent AF patients. PMID:23998759

  17. Spectral of electrocardiographic RR intervals to indicate atrial fibrillation

    Science.gov (United States)

    Nuryani, Nuryani; Satrio Nugroho, Anto

    2017-11-01

    Atrial fibrillation is a serious heart diseases, which is associated on the risk of death, and thus an early detection of atrial fibrillation is necessary. We have investigated spectral pattern of electrocardiogram in relation to atrial fibrillation. The utilized feature of electrocardiogram is RR interval. RR interval is the time interval between a two-consecutive R peaks. A series of RR intervals in a time segment is converted to a signal with a frequency domain. The frequency components are investigated to find the components which significantly associate to atrial fibrillation. A segment is defined as atrial fibrillation or normal segments by considering a defined number of atrial fibrillation RR in the segment. Using clinical data of 23 patients with atrial fibrillation, we find that the frequency components could be used to indicate atrial fibrillation.

  18. Instabilities in Interacting Binary Stars

    Science.gov (United States)

    Andronov, I. L.; Andrych, K. D.; Antoniuk, K. A.; Baklanov, A. V.; Beringer, P.; Breus, V. V.; Burwitz, V.; Chinarova, L. L.; Chochol, D.; Cook, L. M.; Cook, M.; Dubovský, P.; Godlowski, W.; Hegedüs, T.; Hoňková, K.; Hric, L.; Jeon, Y.-B.; Juryšek, J.; Kim, C.-H.; Kim, Y.; Kim, Y.-H.; Kolesnikov, S. V.; Kudashkina, L. S.; Kusakin, A. V.; Marsakova, V. I.; Mason, P. A.; Mašek, M.; Mishevskiy, N.; Nelson, R. H.; Oksanen, A.; Parimucha, S.; Park, J.-W.; Petrík, K.; Quiñones, C.; Reinsch, K.; Robertson, J. W.; Sergey, I. M.; Szpanko, M.; Tkachenko, M. G.; Tkachuk, L. G.; Traulsen, I.; Tremko, J.; Tsehmeystrenko, V. S.; Yoon, J.-N.; Zola, S.; Shakhovskoy, N. M.

    2017-07-01

    parts of the ILA project are “Stellar Bell” (interesting pulsating variables of different types and periods - M, SR, RV Tau, RR Lyr, Delta Sct with changes of characteristics) and “Novice”(=“New Variable”) discoveries and classification based on special own observations and data mining with a subsequent monitoring for searching and studying possible multiple components of variability. Special mathematical methods have been developed to create a set of complementary software for statistically optimal modeling of variable stars of different types.

  19. PULSATION PERIOD VARIATIONS IN THE RRc LYRAE STAR KIC 5520878

    Energy Technology Data Exchange (ETDEWEB)

    Hippke, Michael [Institute for Data Analysis, Luiter Str. 21b, D-47506 Neukirchen-Vluyn (Germany); Learned, John G. [High Energy Physics Group, Department of Physics and Astronomy, University of Hawaii, Manoa 327 Watanabe Hall, 2505 Correa Road, Honolulu, HI 96822 (United States); Zee, A. [Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States); Edmondson, William H. [School of Computer Science, University of Birmingham, Birmingham B15 2TT (United Kingdom); Lindner, John F. [Physics Department, The College of Wooster, Wooster, OH 44691 (United States); Kia, Behnam; Ditto, William L. [Department of Physics and Astronomy, University of Hawai' i at Mānoa, Honolulu, HI 96822 (United States); Stevens, Ian R., E-mail: hippke@ifda.eu, E-mail: jgl@phys.hawaii.edu, E-mail: zee@kitp.ucsb.edu, E-mail: w.h.edmondson@bham.ac.uk, E-mail: jlindner@wooster.edu, E-mail: wditto@hawaii.edu, E-mail: behnam@hawaii.edu, E-mail: irs@star.sr.bham.ac.uk [School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT (United Kingdom)

    2015-01-01

    Learned et al. proposed that a sufficiently advanced extra-terrestrial civilization may tickle Cepheid and RR Lyrae variable stars with a neutrino beam at the right time, thus causing them to trigger early and jogging the otherwise very regular phase of their expansion and contraction. This would turn these stars into beacons to transmit information throughout the galaxy and beyond. The idea is to search for signs of phase modulation (in the regime of short pulse duration) and patterns, which could be indicative of intentional, omnidirectional signaling. We have performed such a search among variable stars using photometric data from the Kepler space telescope. In the RRc Lyrae star KIC 5520878, we have found two such regimes of long and short pulse durations. The sequence of period lengths, expressed as time series data, is strongly autocorrelated, with correlation coefficients of prime numbers being significantly higher (p = 99.8%). Our analysis of this candidate star shows that the prime number oddity originates from two simultaneous pulsation periods and is likely of natural origin. Simple physical models elucidate the frequency content and asymmetries of the KIC 5520878 light curve. Despite this SETI null result, we encourage testing of other archival and future time-series photometry for signs of modulated stars. This can be done as a by-product to the standard analysis, and can even be partly automated.

  20. An Application of Supervised Learning Methods to Search for Variable Stars in a Selected Field of the VVV Survey

    Science.gov (United States)

    Rodríguez-Feliciano, B.; García-Varela, A.; Pérez-Ortiz, M. F.; Sabogal, B. E.; Minniti, D.

    2017-07-01

    We characterize properties of time series of variable stars in the B278 field of the VVV survey, using robust statistics. Using random forest and support vector machines classifiers we propose 47 candidates to RR Lyraae, and 12 candidates to WU Ursae Majoris eclipsing binaries.

  1. Degradation of microcystin-RR using boron-doped diamond electrode

    International Nuclear Information System (INIS)

    Zhang Chunyong; Fu Degang; Gu Zhongze

    2009-01-01

    Microcystins (MCs), produced by blue-green algae, are one of the most common naturally occurring toxins found in natural environment. The presence of MCs in drinking water sources poses a great threat to people's health. In this study, the degradation behavior of microcystin-RR on boron-doped diamond (BDD) electrode was investigated under galvanostatic conditions. Such parameters as reaction time, supporting electrolyte and applied current density were varied in order to determine their effects on this oxidation process. The experimental results revealed the suitability of electrochemical processes employing BDD electrode for removing MC-RR from the solution. However, the efficient removal of MC-RR only occurred in the presence of sodium chloride that acted as redox mediators and the reaction was mainly affected by the chloride concentration (c NaCl ) and applied current density (I appl ). Full and quick removal of 0.50 μg/ml MC-RR in solution was achieved when the operating conditions of c NaCl and I appl were 20 mM and 46.3 mA/cm 2 , or 35 mM and 18.2 mA/cm 2 respectively. The kinetics for MC-RR degradation followed a pesudo-first order reaction in most cases, indicating the process was under mass transfer control. As a result of its excellent performance, the BDD technology could be considered as a promising alternative to promote the degradation of MC-RR than chlorination in drinking water supplies.

  2. Variable star research at Los Alamos

    International Nuclear Information System (INIS)

    Davis, C.G.; Cox, A.N.; Adams, T.F.

    1978-01-01

    Three major areas of variable star research at Los Alamos are carried out: (1) a study using improved Cepheid light curves in order to define more precisely the Hertzsprung sequence, in collaboration with John Castor and John Cox; (2) the suggestion by A. Cox that helium enrichment occurs in the stellar envelope, by a stellar wind, which may explain many of the mass anomalies, this work being with G. Michaud, D. King, R. Deupree, and S. Hodson; and (3) the study of Cepheid and RR Lyrae colors to compare directly to the observations. A brief discussion of the present status of each of these research programs will be given. 25 references

  3. QT/RR hysteresis as a function of RR excitation – implications for risk

    Czech Academy of Sciences Publication Activity Database

    Halámek, Josef; Jurák, Pavel; Somers, V. K.; Nykodým, J.; Leinveber, P.; Fráňa, P.; Eisenberger, M.; Kára, T.

    2005-01-01

    Roč. 4, č. 1 (2005), s. 98 [World Congress on Heart Disease - New Trends in Research, Diagnosis and Treatment /12./. 16.07.2005-19.07.2005, Vancouver] Institutional research plan: CEZ:AV0Z20650511 Keywords : ventricular repolarization * RR intervals Subject RIV: FA - Cardiovascular Disease s incl. Cardiotharic Surgery

  4. Near-IR period-luminosity relations for pulsating stars in ω Centauri (NGC 5139)

    Science.gov (United States)

    Navarrete, C.; Catelan, M.; Contreras Ramos, R.; Alonso-García, J.; Gran, F.; Dékány, I.; Minniti, D.

    2017-08-01

    Aims: The globular cluster ω Centauri (NGC 5139) hosts hundreds of pulsating variable stars of different types, thus representing a treasure trove for studies of their corresponding period-luminosity (PL) relations. Our goal in this study is to obtain the PL relations for RR Lyrae and SX Phoenicis stars in the field of the cluster, based on high-quality, well-sampled light curves in the near-infrared (IR). Methods: Observations were carried out using the VISTA InfraRed CAMera (VIRCAM) mounted on the Visible and Infrared Survey Telescope for Astronomy (VISTA). A total of 42 epochs in J and 100 epochs in KS were obtained, spanning 352 days. Point-spread function photometry was performed using DoPhot and DAOPHOT crowded-field photometry packages in the outer and inner regions of the cluster, respectively. Results: Based on the comprehensive catalog of near-IR light curves thus secured, PL relations were obtained for the different types of pulsators in the cluster, both in the J and KS bands. This includes the first PL relations in the near-IR for fundamental-mode SX Phoenicis stars. The near-IR magnitudes and periods of Type II Cepheids and RR Lyrae stars were used to derive an updated true distance modulus to the cluster, with a resulting value of (m - M)0 = 13.708 ± 0.035 ± 0.10 mag, where the error bars correspond to the adopted statistical and systematic errors, respectively. Adding the errors in quadrature, this is equivalent to a heliocentric distance of 5.52 ± 0.27 kpc. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, with the VISTA telescope (project ID 087.D-0472, PI R. Angeloni).

  5. Lignification of the plant and seed quality of RR soybeans sprayed with herbicide glyphosate Lignificação da planta e qualidade de sementes de soja RR pulverizadas com herbicida glifosato

    Directory of Open Access Journals (Sweden)

    Cristiane Fortes Gris

    2013-04-01

    Full Text Available Differences in levels of lignin in the plant between conventional and transgenic cultivars RR has been reported by several authors, however, there are few studies evaluating the influence of spraying of glyphosate on the lignin in the plant and RR soybean seeds. The aim of this study was to evaluate the physiological quality of RR transgenic soybean seeds and the lignin contents of plants sprayed with the herbicide glyphosate. The assays were conducted both in greenhouse and field in the municipality of Lavras, MG, in the agricultural year 2007/08. The experiment was arranged in a splitplot design with four replicates, considering the treatments hand weeding and herbicide glyphosate as plots, and five RR soybean cultivars (BRS 245 RR, BRS 247 RR, Valiosa RR, Silvânia RR and Baliza RR as splitplots. In the greenhouse, the cultivars tested were BRS 245 RR and Valiosa RR in a randomized block design with four replicates. The sprayings were carried out at stages V3, V7 and early R5 (3L/ha. The 1000 seed weight, mechanical injury, germination and germination velocity index, emergence velocity index, accelerated aging, electrical conductivity and water soaking seed test, lignin content in the seed coat, in the stem and legumes were determined. The spraying of glyphosate herbicide, in greenhouse and field, did not alter the physiological quality of seeds and the lignin contents in the plant.Diferenças nos teores de lignina na planta entre cultivares transgênicos RR e convencionais, tem sido relatadas, por vários autores, no entanto, são escassos os trabalhos avaliando a influência da aplicação do glifosato sobre os teores de lignina na planta e em sementes de soja RR. Neste sentido, objetivou-se, com este trabalho, avaliar a qualidade fisiológica de sementes de soja transgênica RR e os teores de lignina de plantas submetidas à pulverização com o herbicida glifosato. Os ensaios foram conduzidos em casa de vegetação e em campo, no munic

  6. Commissioning of the STAR test section for experimental simulation of loss of coolant accident using the EC-208 instrumented fuel assembly of the IEA-R1 reactor

    Energy Technology Data Exchange (ETDEWEB)

    Maprelian, Eduardo; Torres, Walmir M.; Prado, Adelk C.; Umbehaun, Pedro E.; Franca, Renato L.; Santos, Samuel C.; Macedo, Luiz A.; Sabundjian, Gaiane, E-mail: emaprel@ipen.br, E-mail: wmtorres@ipen.br, E-mail: acprado@ipen.br, E-mail: umbehaun@ipen.br, E-mail: rlfranca@ipen.br, E-mail: samuelcs@ipen.br, E-mail: lamacedo@ipen.br, E-mail: gdjian@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SO (Brazil)

    2015-07-01

    The three basic safety functions of Research Reactors (RR) are the safe shutdown of the reactor, the proper cooling of the decay heat of the fuel elements and the confinement of radioactive materials. Compared to Nuclear Power Reactors, RR power release is small, yet its three safety functions must be met to ensure the integrity of the reactor. During a loss of coolant accident (LOCA) in pool type RR, partial or complete loss of pool water may occur, with consequent partial or complete uncovering of the fuel assemblies. In such an accident, the decay heat removal safety function must not be compromised. The Test Section for Experimental Simulation of Loss of Coolant Accident (STAR) is in commissioning phase. This test section will provide experimental data on partial and total uncovering of the EC-208 instrumented fuel assembly (IFA) irradiated in the IEA-R1. Experimental results will be useful in validation of computer codes for RR safety analysis, particularly on heat removal efficiency aspects (safety function) in accident conditions. STAR comprises a base on which is installed the IFA, the cylindrical stainless steel hull, the compressed air system for the test section emptying and refilling, and the instrumentation for temperature and level measurements. The commissioning tests or pre-operational check, consist of several preliminary tests to verify experimental procedures, the difficulties during assembling of STAR in the pool, the difficulties in control the emptying and refilling velocities, as well as, the repeatability capacity, tests of equipment, valves and systems and tests of instrumentation and data acquisition system. Safety, accuracy and easiness of operation will be checked. (author)

  7. Variable Stars Observed in the Galactic Disk by AST3-1 from Dome A, Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lingzhi; Ma, Bin; Hu, Yi; Liu, Qiang; Shang, Zhaohui [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Li, Gang; Fu, Jianning [Department of Astronomy, Beijing Normal University, Beijing, 100875 (China); Wang, Lifan; Cui, Xiangqun; Du, Fujia; Gong, Xuefei; Li, Xiaoyan; Li, Zhengyang; Yuan, Xiangyan; Zhou, Jilin [Chinese Center for Antarctic Astronomy, Nanjing 210008 (China); Ashley, Michael C. B. [School of Physics, University of New South Wales, NSW 2052 (Australia); Pennypacker, Carl R. [Center for Astrophysics, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); York, Donald G., E-mail: wanglingzhi@bao.ac.cn [Department of Astronomy and Astrophysics and Enrico Fermi Institute, University of Chicago, Chicago, IL 60637 (United States)

    2017-03-01

    AST3-1 is the second-generation wide-field optical photometric telescope dedicated to time-domain astronomy at Dome A, Antarctica. Here, we present the results of an i -band images survey from AST3-1 toward one Galactic disk field. Based on time-series photometry of 92,583 stars, 560 variable stars were detected with i magnitude ≤16.5 mag during eight days of observations; 339 of these are previously unknown variables. We tentatively classify the 560 variables as 285 eclipsing binaries (EW, EB, and EA), 27 pulsating variable stars ( δ Scuti, γ Doradus, δ Cephei variable, and RR Lyrae stars), and 248 other types of variables (unclassified periodic, multiperiodic, and aperiodic variable stars). Of the eclipsing binaries, 34 show O’Connell effects. One of the aperiodic variables shows a plateau light curve and another variable shows a secondary maximum after peak brightness. We also detected a complex binary system with an RS CVn-like light-curve morphology; this object is being followed-up spectroscopically using the Gemini South telescope.

  8. Mid-Infrared Interferometric Monitoring of Evolved Stars: The Dust Shell Around the Mira Variable RR Aquilae at 13 Epochs

    Science.gov (United States)

    2011-01-01

    photometric and interferometric data. 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT Same as Report (SAR) 18. NUMBER OF...λ = 2.2 μm, Δλ = 0.4 μm) angular size with the Infrared Optical Telescope Array ( IOTA ). The uniform disk diameter (UD) of θUD = 10.73 ± 0.66 mas at...with IOTA in the H-band, and classified RR Aql as a target with no detectable asymmetries. The IRAS flux at 12 μm is 332 Jy. The light curve in the V

  9. RR Tel: Getting Under the Flux Limit: An Observation with FUSE

    Science.gov (United States)

    Sonnenborn, George (Technical Monitor); Kenyon, Scott J.

    2004-01-01

    The goal of this program is to acquire a FUSE spectrum of the symbiotic binary RR Tel. With these data, we plan to derive improved constraints on the hot component, the nebula, and perhaps the red giant wind. Based on results from AG Dra, we should also be able to use some line detections to improve atomic parameters for high ionization emission lines. This results would benefit the general FUSE community. As of this writing, the FUSE observation of RR Tel has not been made. Because RR Tel is a very bright UV source, the FUSE team is assessing the likelihood that RR Tel will have an adverse affect on the instrument.

  10. NESDIS Blended Rain Rate (RR) Products

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The blended Rain Rate (RR) product is derived from multiple sensors/satellites. The blended products were merged from polar-orbiting and geostationary satellite...

  11. Lignification of the plant and seed quality of RR soybeans sprayed with herbicide glyphosate

    Directory of Open Access Journals (Sweden)

    Cristiane Fortes Gris

    2013-04-01

    Full Text Available Differences in levels of lignin in the plant between conventional and transgenic cultivars RR has been reported by several authors, however, there are few studies evaluating the influence of spraying of glyphosate on the lignin in the plant and RR soybean seeds. The aim of this study was to evaluate the physiological quality of RR transgenic soybean seeds and the lignin contents of plants sprayed with the herbicide glyphosate. The assays were conducted both in greenhouse and field in the municipality of Lavras, MG, in the agricultural year 2007/08. The experiment was arranged in a splitplot design with four replicates, considering the treatments hand weeding and herbicide glyphosate as plots, and five RR soybean cultivars (BRS 245 RR, BRS 247 RR, Valiosa RR, Silvânia RR and Baliza RR as splitplots. In the greenhouse, the cultivars tested were BRS 245 RR and Valiosa RR in a randomized block design with four replicates. The sprayings were carried out at stages V3, V7 and early R5 (3L/ha. The 1000 seed weight, mechanical injury, germination and germination velocity index, emergence velocity index, accelerated aging, electrical conductivity and water soaking seed test, lignin content in the seed coat, in the stem and legumes were determined. The spraying of glyphosate herbicide, in greenhouse and field, did not alter the physiological quality of seeds and the lignin contents in the plant.

  12. A 4D spacetime embedded in a 5D pseudo-Euclidean space describing interior of compact stars

    Energy Technology Data Exchange (ETDEWEB)

    Singh, K.N. [National Defence Academy, Department of Physics, Khadakwasla (India); Murad, Mohammad Hassan [BRAC University, Department of Mathematics and Natural Sciences, Dhaka (Bangladesh); Pant, Neeraj [National Defence Academy, Department of Mathematics, Khadakwasla (India)

    2017-02-15

    The present paper provides a new model of compact stars satisfying the Karmarkar condition. The model is obtained by assuming a new type of metric potential for g{sub rr} from the condition of embedding class I. The model parameters are obtained accordingly by employing the metric potentials to Einstein's field equations. Our model is free from geometric singularity and satisfies all the physical conditions. The obtained mass and radius of the compact stars Cen X-3, EXO 1785-248 and SAX 1808.4-3658 obtained from the model are consistent with the observational data of T. Gangopadhyay et al. Detailed analyses of these neutron stars (Cen X-3, EXO 1785-248 and SAX 1808.4-3658) are also given with the help of graphical representations. (orig.)

  13. A NOVEL APPROACH TO ARRHYTHMIA CLASSIFICATION USING RR INTERVAL AND TEAGER ENERGY

    Directory of Open Access Journals (Sweden)

    CHANDRAKAR KAMATH

    2012-12-01

    Full Text Available It is hypothesized that a key characteristic of electrocardiogram (ECG signal is its nonlinear dynamic behaviour and that the nonlinear component changes more significantly between normal and arrhythmia conditions than the linear component. The usual statistical descriptors used in RR (R to R interval analysis do not capture the nonlinear disposition of RR interval variability. In this paper we explore a novel approach to extract the features from nonlinear component of the RR interval signal using Teager energy operator (TEO. The key feature of Teager energy is that it models the energy of the source that generated the signal rather than the energy of the signal itself. Hence any deviations in regular rhythmic activity of the heart get reflected in the Teager energy function. The classification evaluated on MIT-BIH database, with RR interval and mean of Teager energy computed over RR interval as features, exhibits an average accuracy that exceeds 99.79%.

  14. The coefficient of rolling resistance (CoRR) of some pharmaceutical tablets.

    Science.gov (United States)

    Ketterhagen, William R; Bharadwaj, Rahul; Hancock, Bruno C

    2010-06-15

    Experiments have been conducted to measure the coefficient of rolling resistance (CoRR) of some pharmaceutical tablets and several common materials, such as glass beads and steel ball bearings. CoRR values are required as inputs for discrete element method (DEM) models which can be used to model particulate flows and solid dosage form manufacturing processes. Until now there have been no CoRR data reported for pharmaceutical materials, and thus these new data will help to facilitate more accurate modeling of pharmaceutical systems. Copyright 2010 Elsevier B.V. All rights reserved.

  15. Two-color photographic photometry of variables in the globular cluster M28

    International Nuclear Information System (INIS)

    Wehlau, A.; Butterworth, S.

    1990-01-01

    Visual magnitudes have been measured for 20 variables on 32 plates of M28. These have been combined with previously published as well as newly determined blue magnitudes in order to obtain colors for the variables. Blue and visual light curves are presented for 15 of the the variables, including one W Virginis star V4, one RV Tauri star V17, one field Mira variable V7, nine cluster RR Lyrae stars, and three field RR Lyrae stars. It is shown that V14, previously thought to be a c type RR Lyrae star, is to the red of the instability strip. The visual light curve of V9 suggests that the star may be a member of a binary or a very close optical double. Possible evidence for differential reddening in the vicinity of M28 is presented. The bimodal distribution of the periods of the RR Lyrae stars in M28 may indicate a spread in metallicity among the RR Lyrae variables. 16 refs

  16. Infrared variability and nature of symbiotic stars

    Energy Technology Data Exchange (ETDEWEB)

    Feast, M W; Robertson, B S.C.; Catchpole, R M [Royal Observatory, Cape Town (South Africa)

    1977-05-01

    Most symbiotic stars may be placed in one of two classes according to their infrared colours. In one group the systems contain an M type giant. In the other there is evidence for a star plus infrared emission from dust. JHKL photometry is given for three members of each class. Photometry of the VV Cephei system FR Sct is also given. No evidence for variability was found for systems without dust. The three systems with dust (RX Pup, RR Tel and PK 280-2/sup 0/.1) each show large variations of the stellar component (..delta..J, 1sup(m).6 to 2sup(m).7). It is concluded that these dusty systems contain Mira variables. For the systems without dust the mass transfer in the system is presumably through the inner Lagrangian point. For systems containing Miras it is possible that the companion accretes matter from a general stellar wind. Symbiotic systems containing Mira variables have more dust than average Mira variables. Either an unusually dense stellar wind is needed to produce a symbiotic system or such a system produces dust, perhaps in a high-density region resulting from the interaction of the stellar wind with the companion.

  17. [Heart rate variability study based on a novel RdR RR Intervals Scatter Plot].

    Science.gov (United States)

    Lu, Hongwei; Lu, Xiuyun; Wang, Chunfang; Hua, Youyuan; Tian, Jiajia; Liu, Shihai

    2014-08-01

    On the basis of Poincare scatter plot and first order difference scatter plot, a novel heart rate variability (HRV) analysis method based on scatter plots of RR intervals and first order difference of RR intervals (namely, RdR) was proposed. The abscissa of the RdR scatter plot, the x-axis, is RR intervals and the ordinate, y-axis, is the difference between successive RR intervals. The RdR scatter plot includes the information of RR intervals and the difference between successive RR intervals, which captures more HRV information. By RdR scatter plot analysis of some records of MIT-BIH arrhythmias database, we found that the scatter plot of uncoupled premature ventricular contraction (PVC), coupled ventricular bigeminy and ventricular trigeminy PVC had specific graphic characteristics. The RdR scatter plot method has higher detecting performance than the Poincare scatter plot method, and simpler and more intuitive than the first order difference method.

  18. QT/RR Coupling and Gender Differences

    Czech Academy of Sciences Publication Activity Database

    Halámek, Josef; Jurák, Pavel; Lipoldová, J.; Leinveber, Pavel

    2010-01-01

    Roč. 37, - (2010), s. 365-368 ISSN 0276-6574 R&D Projects: GA ČR GA102/08/1129 Institutional research plan: CEZ:AV0Z20650511 Keywords : THEW * QT/RR model * EXPDC Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering http://cinc.mit.edu/archives/2010/pdf/0365.pdf

  19. New bound on neutrino dipole moments from globular-cluster stars

    Science.gov (United States)

    Raffelt, Georg G.

    1990-01-01

    Neutrino dipole moments mu(nu) would increase the core mass of red giants at the helium flash by delta(Mc) = 0.015 solar mass x mu(nu)/10 to the -12th muB (where muB is the Bohr magneton) because of enhanced neutrino losses. Existing measurements of the bolometric magnitudes of the brightest red giants in 26 globular clusters, number counts of horizontal-branch stars and red giants in 15 globular clusters, and statistical parallax determinations of field RR Lyr luminosities yield delta(Mc) = 0.009 + or - 0.012 solar mass, so that conservatively mu(nu) is less than 3 x 10 to the -12th muB.

  20. Identification of atrial fibrillation using electrocardiographic RR-interval difference

    Science.gov (United States)

    Eliana, M.; Nuryani, N.

    2017-11-01

    Automated detection of atrial fibrillation (AF) is an interesting topic. It is an account of very dangerous, not only as a trigger of embolic stroke, but it’s also related to some else chronical disease. In this study, we analyse the presence of AF by determining irregularities of RR-interval. We utilize the interval comparison to measure the degree of irregularities of RR-interval in a defined segment. The series of RR-interval is segmented with the length of 10 of them. In this study, we use interval comparison for the method. We were comparing all of the intervals there each other. Then we put the threshold to define the low difference and high difference (δ). A segment is defined as AF or Normal Sinus by the number of high δ, so we put the tolerance (β) of high δ there. We have used this method to test the 23 patients data from MIT-BIH. Using the approach and the clinical data we find accuracy, sensitivity, and specificity of 84.98%, 91.99%, and 77.85% respectively.

  1. 77 FR 27085 - R.R. Donnelley, Inc., Bloomsburg, PA; Notice of Negative Determination on Reconsideration

    Science.gov (United States)

    2012-05-08

    ... DEPARTMENT OF LABOR Employment and Training Administration [TA-W-80,485] R.R. Donnelley, Inc... workers of R.R. Donnelley, Inc., Bloomsburg, Pennsylvania (subject firm). The Department's Notice of... eligibility to apply for worker adjustment assistance for workers and former workers of R.R. Donnelley, Inc...

  2. Mechanism of blood pressure and R-R variability: insights from ganglion blockade in humans

    Science.gov (United States)

    Zhang, Rong; Iwasaki, Kenichi; Zuckerman, Julie H.; Behbehani, Khosrow; Crandall, Craig G.; Levine, Benjamin D.; Blomqvist, C. G. (Principal Investigator)

    2002-01-01

    Spontaneous blood pressure (BP) and R-R variability are used frequently as 'windows' into cardiovascular control mechanisms. However, the origin of these rhythmic fluctuations is not completely understood. In this study, with ganglion blockade, we evaluated the role of autonomic neural activity versus other 'non-neural' factors in the origin of BP and R-R variability in humans. Beat-to-beat BP, R-R interval and respiratory excursions were recorded in ten healthy subjects (aged 30 +/- 6 years) before and after ganglion blockade with trimethaphan. The spectral power of these variables was calculated in the very low (0.0078-0.05 Hz), low (0.05-0.15 Hz) and high (0.15-0.35 Hz) frequency ranges. The relationship between systolic BP and R-R variability was examined by cross-spectral analysis. After blockade, R-R variability was virtually abolished at all frequencies; however, respiration and high frequency BP variability remained unchanged. Very low and low frequency BP variability was reduced substantially by 84 and 69 %, respectively, but still persisted. Transfer function gain between systolic BP and R-R interval variability decreased by 92 and 88 % at low and high frequencies, respectively, while the phase changed from negative to positive values at the high frequencies. These data suggest that under supine resting conditions with spontaneous breathing: (1) R-R variability at all measured frequencies is predominantly controlled by autonomic neural activity; (2) BP variability at high frequencies (> 0.15 Hz) is mediated largely, if not exclusively, by mechanical effects of respiration on intrathoracic pressure and/or cardiac filling; (3) BP variability at very low and low frequencies (rhythmicity; and (4) the dynamic relationship between BP and R-R variability as quantified by transfer function analysis is determined predominantly by autonomic neural activity rather than other, non-neural factors.

  3. DNA aptamer selection and aptamer-based fluorometric displacement assay for the hepatotoxin microcystin-RR

    International Nuclear Information System (INIS)

    Wu, Shijia; Li, Qi; Duan, Nuo; Wang, Zhouping; Ma, Haile

    2016-01-01

    Microcystin-RR (MC-RR) is a highly acute hepatotoxin produced by cyanobacteria. It is harmful to both humans and the environment. A novel aptamer was identified by the systemic evolution of ligands by exponential enrichment (SELEX) method as a recognition element for determination of MC-RR in aquatic products. The graphene oxide (GO) SELEX strategy was adopted to generate aptamers with high affinity and specificity. Of the 50 aptamer candidates tested, sequence RR-33 was found to display high affinity and selectivity, with a dissociation constant of 45.7 ± 6.8 nM. Aptamer RR-33 therefore was used as the recognition element in a fluorometric assay that proceeds as follows: (1) Biotinylated aptamer RR-33 is immobilized on the streptavidinylated wells of a microtiterplate, and carboxyfluorescein (FAM) labelled complementary DNA is then allowed to hybridize. (2) After removal of excess (unbound) cDNA, sample containing MC-RR is added and incubated at 37 °C for 2 h. (3) Displaced free cDNA is washed away and fluorescence intensity measured at excitation/emission wavelengths of 490/515 nm. The calibration plot is linear in the 0.20 to 2.5 ng·mL −1 concentration range, and the limit of detection is 80 pg·mL −1 . The results indicate that the GO-SELEX technology is appropriate for the screening of aptamers against small-molecule toxins. The detection scheme was applied to the determination of MC-RR in (spiked) water, mussel and fish and gave recoveries between 91 and 98 %. The method compares favorably to a known ELISA. Conceivably, this kind of assay is applicable to other toxins for which appropriate aptamers are available. (author)

  4. IUE observations of W UMa-type stars

    International Nuclear Information System (INIS)

    Rucinski, S.M.; Vilhu, O.

    1983-01-01

    IUE (International Ultraviolet Explorer) low-resolution SWP images of the contract binaries 44i Boo, VW Cep, W UMa, V566 Oph, AW UMa, V502 Oph, epsilon CrA, RR Cen and the very close non-contact binary ER Vul have been studied. The results are compared with other UV and soft X-ray data and it is found that the stellar activity within this group is quite similar to solar activity but much more intense; the higher the general level of activity, the higher are the excitation energies that are seen, except that the soft X-ray emission of the W UMa stars does not conform to this picture. The ultraviolet chromospheric and transition-region normalized line fluxes (fsub(line)/fsub(bol)) are not very sensitive to spectral type and orbital period among W UMa stars. However, a small weakening towards earlier spectral types is evident. The far ultraviolet chromospheric and transition-region activity seems to level off towards short periods; for soft X-rays the coronal radiation of contact binaries is actually weaker than for detached binaries with somewhat longer periods. The C IV emission variations with phase in 44i Boo have also been analysed. (author)

  5. Ridge Regression and Other Kernels for Genomic Selection with R Package rrBLUP

    Directory of Open Access Journals (Sweden)

    Jeffrey B. Endelman

    2011-11-01

    Full Text Available Many important traits in plant breeding are polygenic and therefore recalcitrant to traditional marker-assisted selection. Genomic selection addresses this complexity by including all markers in the prediction model. A key method for the genomic prediction of breeding values is ridge regression (RR, which is equivalent to best linear unbiased prediction (BLUP when the genetic covariance between lines is proportional to their similarity in genotype space. This additive model can be broadened to include epistatic effects by using other kernels, such as the Gaussian, which represent inner products in a complex feature space. To facilitate the use of RR and nonadditive kernels in plant breeding, a new software package for R called rrBLUP has been developed. At its core is a fast maximum-likelihood algorithm for mixed models with a single variance component besides the residual error, which allows for efficient prediction with unreplicated training data. Use of the rrBLUP software is demonstrated through several examples, including the identification of optimal crosses based on superior progeny value. In cross-validation tests, the prediction accuracy with nonadditive kernels was significantly higher than RR for wheat ( L. grain yield but equivalent for several maize ( L. traits.

  6. Adipose tissue (P)RR regulates insulin sensitivity, fat mass and body weight.

    Science.gov (United States)

    Shamansurova, Zulaykho; Tan, Paul; Ahmed, Basma; Pepin, Emilie; Seda, Ondrej; Lavoie, Julie L

    2016-10-01

    We previously demonstrated that the handle-region peptide, a prorenin/renin receptor [(P)RR] blocker, reduces body weight and fat mass and may improve insulin sensitivity in high-fat fed mice. We hypothesized that knocking out the adipose tissue (P)RR gene would prevent weight gain and insulin resistance. An adipose tissue-specific (P)RR knockout (KO) mouse was created by Cre-loxP technology using AP2-Cre recombinase mice. Because the (P)RR gene is located on the X chromosome, hemizygous males were complete KO and had a more pronounced phenotype on a normal diet (ND) diet compared to heterozygous KO females. Therefore, we challenged the female mice with a high-fat diet (HFD) to uncover certain phenotypes. Mice were maintained on either diet for 9 weeks. KO mice had lower body weights compared to wild-types (WT). Only hemizygous male KO mice presented with lower total fat mass, higher total lean mass as well as smaller adipocytes compared to WT mice. Although food intake was similar between genotypes, locomotor activity during the active period was increased in both male and female KO mice. Interestingly, only male KO mice had increased O2 consumption and CO2 production during the entire 24-hour period, suggesting an increased basal metabolic rate. Although glycemia during a glucose tolerance test was similar, KO males as well as HFD-fed females had lower plasma insulin and C-peptide levels compared to WT mice, suggesting improved insulin sensitivity. Remarkably, all KO animals exhibited higher circulating adiponectin levels, suggesting that this phenotype can occur even in the absence of a significant reduction in adipose tissue weight, as observed in females and, thus, may be a specific effect related to the (P)RR. (P)RR may be an important therapeutic target for the treatment of obesity and its associated complications such as type 2 diabetes.

  7. Lignification of the plant and seed quality of RR soybeans sprayed with herbicide glyphosate

    OpenAIRE

    Gris,Cristiane Fortes; Pinho,Edila Vilela de Resende Von; Carvalho,Maria Laene de Moreira; Diniz,Rafael Parreira; Andrade,Thaís de

    2013-01-01

    Differences in levels of lignin in the plant between conventional and transgenic cultivars RR has been reported by several authors, however, there are few studies evaluating the influence of spraying of glyphosate on the lignin in the plant and RR soybean seeds. The aim of this study was to evaluate the physiological quality of RR transgenic soybean seeds and the lignin contents of plants sprayed with the herbicide glyphosate. The assays were conducted both in greenhouse and field in the muni...

  8. Genetic divergence of roundup ready (RR) soybean cultivars ...

    African Journals Online (AJOL)

    The aim of this study was to estimate the genetic diversity in 74 RR soybean cultivars from different Brazilian breeding programs. ... chosen SSR markers were effective in assessing the genetic diversity among genotypes, besides proving to be ...

  9. [The characteristics of RR-Lorenz plot in persistent atrial fibrillation patients complicating with escape beats and rhythm].

    Science.gov (United States)

    Pan, Yunping; Zhang, Fangfang; Liu, Ru; Jing, Yan; Shen, Jihong; Li, Zhongjian; Zhu, Huaijie

    2014-06-01

    To explore the characteristics of RR-Lorenz plot in persistent atrial fibrillation (AF) patients complicating with escape beats and rhythm though ambulatory electrocardiogram. The 24-hour ambulatory electrocardiogram of 291 persistent AF patients in second affiliated hospital of Zhengzhou university from July 2005 to April 2013 were retrospectively analyzed and the RR interval and the QRS wave were measured. Patients were divided into two groups according to the distribution of the RR-Lorenz point [AF without escape beats and rhythm group (Group A, n = 259) and AF with escape beats and rhythm group (Group B, n = 32)]. The characteristics of RR-Lorenz plot between the two groups were compared. (1) Fan-shaped RR-Lorenz plots were evidenced in Group A. (2)In Group B, 30 cases showed fan-shaped with L-shaped and a short dense rods along 45° line. The proportion of escape beats and rhythm was 0.28% (275/98 369) -14.06% (11 263/80 112) . The other 2 cases in group B showed no typical RR-Lorenz plots features. RR-Lorenz plot could help to quickly diagnose persistent AF complicating with escape beats and rhythm according to the typical RR-Lorenz plot characteristics in 24-hour ambulatory electrocardiogram.

  10. Neutron Stars and NuSTAR

    Science.gov (United States)

    Bhalerao, Varun

    2012-05-01

    My thesis centers around the study of neutron stars, especially those in massive binary systems. To this end, it has two distinct components: the observational study of neutron stars in massive binaries with a goal of measuring neutron star masses and participation in NuSTAR, the first imaging hard X-ray mission, one that is extremely well suited to the study of massive binaries and compact objects in our Galaxy. The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will carry the first focusing high energy X-ray telescope to orbit. NuSTAR has an order-of-magnitude better angular resolution and has two orders of magnitude higher sensitivity than any currently orbiting hard X-ray telescope. I worked to develop, calibrate, and test CdZnTe detectors for NuSTAR. I describe the CdZnTe detectors in comprehensive detail here - from readout procedures to data analysis. Detailed calibration of detectors is necessary for analyzing astrophysical source data obtained by the NuSTAR. I discuss the design and implementation of an automated setup for calibrating flight detectors, followed by calibration procedures and results. Neutron stars are an excellent probe of fundamental physics. The maximum mass of a neutron star can put stringent constraints on the equation of state of matter at extreme pressures and densities. From an astrophysical perspective, there are several open questions in our understanding of neutron stars. What are the birth masses of neutron stars? How do they change in binary evolution? Are there multiple mechanisms for the formation of neutron stars? Measuring masses of neutron stars helps answer these questions. Neutron stars in high-mass X-ray binaries have masses close to their birth mass, providing an opportunity to disentangle the role of "nature" and "nurture" in the observed mass distributions. In 2006, masses had been measured for only six such objects, but this small sample showed the greatest diversity in masses

  11. Mitochondrial electron transport chain is involved in microcystin-RR induced tobacco BY-2 cells apoptosis.

    Science.gov (United States)

    Huang, Wenmin; Li, Dunhai; Liu, Yongding

    2014-09-01

    Microcystin-RR (MC-RR) has been suggested to induce apoptosis in tobacco BY-2 cells through mitochondrial dysfunction including the loss of mitochondrial membrane potential (ΔΨm). To further elucidate the mechanisms involved in MC-RR induced apoptosis in tobacco BY-2 cells, we have investigated the role of mitochondrial electron transport chain (ETC) as a potential source for reactive oxygen species (ROS). Tobacco BY-2 cells after exposure to MC-RR (60mg/L) displayed apoptotic changes in association with an increased production of ROS and loss of ΔΨm. All of these adverse effects were significantly attenuated by ETC inhibitors including Rotenone (2μmol/L, complex I inhibitor) and antimycin A (0.01μmol/L, complex III inhibitor), but not by thenoyltrifluoroacetone (5μmol/L, complex II inhibitor). These results suggest that mitochondrial ETC plays a key role in mediating MC-RR induced apoptosis in tobacco BY-2 cells through an increased mitochondrial production of ROS. Copyright © 2014. Published by Elsevier B.V.

  12. QT-RR relationships and suitable QT correction formulas for halothane-anesthetized dogs.

    Science.gov (United States)

    Tabo, Mitsuyasu; Nakamura, Mikiko; Kimura, Kazuya; Ito, Shigeo

    2006-10-01

    Several QT correction (QTc) formulas have been used for assessing the QT liability of drugs. However, they are known to under- and over-correct the QT interval and tend to be specific to species and experimental conditions. The purpose of this study was to determine a suitable formula for halothane-anesthetized dogs highly sensitive to drug-induced QT interval prolongation. Twenty dogs were anesthetized with 1.5% halothane and the relationship between the QT and RR intervals were obtained by changing the heart rate under atrial pacing conditions. The QT interval was corrected for the RR interval by applying 4 published formulas (Bazett, Fridericia, Van de Water, and Matsunaga); Fridericia's formula (QTcF = QT/RR(0.33)) showed the least slope and lowest R(2) value for the linear regression of QTc intervals against RR intervals, indicating that it dissociated changes in heart rate most effectively. An optimized formula (QTcX = QT/RR(0.3879)) is defined by analysis of covariance and represents a correction algorithm superior to Fridericia's formula. For both Fridericia's and the optimized formula, QT-prolonging drugs (d,l-sotalol, astemizole) showed QTc interval prolongation. A non-QT-prolonging drug (d,l-propranolol) failed to prolong the QTc interval. In addition, drug-induced changes in QTcF and QTcX intervals were highly correlated with those of the QT interval paced at a cycle length of 500 msec. These findings suggest that Fridericia's and the optimized formula, although the optimized is a little bit better, are suitable for correcting the QT interval in halothane-anesthetized dogs and help to evaluate the potential QT prolongation of drugs with high accuracy.

  13. 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.

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

    Science.gov (United States)

    Theodorakis, P. E.; Avgeropoulos, A.; Freire, J. J.; Kosmas, M.; Vlahos, C.

    2007-11-01

    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.

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

    International Nuclear Information System (INIS)

    Theodorakis, P E; Avgeropoulos, A; Freire, J J; Kosmas, M; Vlahos, C

    2007-01-01

    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

  16. Annotation and analysis of a large cuticular protein family with the R&R Consensus in Anopheles gambiae

    Directory of Open Access Journals (Sweden)

    He Ningjia

    2008-01-01

    Full Text Available Abstract Background The most abundant family of insect cuticular proteins, the CPR family, is recognized by the R&R Consensus, a domain of about 64 amino acids that binds to chitin and is present throughout arthropods. Several species have now been shown to have more than 100 CPR genes, inviting speculation as to the functional importance of this large number and diversity. Results We have identified 156 genes in Anopheles gambiae that code for putative cuticular proteins in this CPR family, over 1% of the total number of predicted genes in this species. Annotation was verified using several criteria including identification of TATA boxes, INRs, and DPEs plus support from proteomic and gene expression analyses. Two previously recognized CPR classes, RR-1 and RR-2, form separate, well-supported clades with the exception of a small set of genes with long branches whose relationships are poorly resolved. Several of these outliers have clear orthologs in other species. Although both clades are under purifying selection, the RR-1 variant of the R&R Consensus is evolving at twice the rate of the RR-2 variant and is structurally more labile. In contrast, the regions flanking the R&R Consensus have diversified in amino-acid composition to a much greater extent in RR-2 genes compared with RR-1 genes. Many genes are found in compact tandem arrays that may include similar or dissimilar genes but always include just one of the two classes. Tandem arrays of RR-2 genes frequently contain subsets of genes coding for highly similar proteins (sequence clusters. Properties of the proteins indicated that each cluster may serve a distinct function in the cuticle. Conclusion The complete annotation of this large gene family provides insight on the mechanisms of gene family evolution and clues about the need for so many CPR genes. These data also should assist annotation of other Anopheles genes.

  17. Influence of Age and Aerobic Fitness on the Multifractal Characteristics of Electrocardiographic RR Time-Series

    Directory of Open Access Journals (Sweden)

    Michael James Lewis

    2013-05-01

    Full Text Available Multifractal properties of electrocardiographic inter-beat (RR time-series offer insight into its long-term correlation structure, independently of RR variability. Here we quantify multifractal characteristics of RR data during 24-hour diurnal-nocturnal activity in healthy participants. We tested the hypotheses that (1 age, gender and aerobic fitness influence RR multifractal properties, and that (2 these are influenced by circadian variation.Seventy adults (39 males aged 19-58 years and of various fitness levels were monitored using 24-hour ECG. Participants were dichotomised by median age and fitness for sub-group analysis. Gender and fitness were independent of age (p=0.1, p>0.5. Younger/older group ages were substantially different (p<0.0005 and were independent of gender and fitness. Multifractality was quantified using the probability spectrum of Hölder exponents (h, from which modal h (h* and the full-width and half-widths at half-maximum measures (FWHM, HWHM+ and HWHM- were derived. FWHM decreased (p=0.004 and h* increased (p=0.011 in older people, indicating diminished long-range RR correlations and weaker anti-persistent behavior. Anti-persistent correlation (h* was strongest in the youngest/fittest individuals and weakest in the oldest/least fit individuals (p=0.015. Long-range correlation (HWHM+/FWHM was strongest in the fittest males and weakest in the least fit females (p=0.007-0.033.Multifractal RR characteristics in our healthy participants showed strong age-dependence with diminished long-range anti-persistent correlation in older people. Circadian variation of these characteristics was influenced by fitness and gender: fitter males and females of all ages had the greatest degree of multifractality or long-range order. Multifractal characterisation appears to be a useful method for exploring the physiological basis of long-term correlation structure in RR time-series as well as the benefits thereon of physical fitness training.

  18. A precursive study of the time-domain survey of the Galactic Anti-center using the Nanshan 1-meter telescope with variable stars detected

    Science.gov (United States)

    Ma, Shu-Guo; Esamdin, Ali; Ma, Lu; Niu, Hu-Biao; Fu, Jian-Ning; Zhang, Yu; Liu, Jin-Zhong; Yang, Tao-Zhi; Song, Fang-Fang; Pu, Guang-Xin

    2018-04-01

    Following the LAMOST Spectroscopic Survey and the Xuyi's Photometric Survey of the Galactic Anti-center, we plan to carry out a time-domain survey of the Galactic Anti-center (TDS-GAC) to study variable stars by using the Nanshan 1-meter telescope. Before the beginning of TDS-GAC, a precursive sky survey (PSS) has been executed. The goal of the PSS is to optimize the observation strategy of TDS-GAC and to detect some strong transient events, as well as to find some short time-scale variable stars of different types. By observing a discontinuous sky area of 15.03 deg2 with the standard Johnson-Cousin-Bessel V filter, 48 variable stars are found and the time series are analyzed. Based on the behaviors of the light curves, 28 eclipsing binary stars, 10 RR Lyraes, 3 periodic pulsating variables of other types have been classified. The rest 7 variables stay unclassified with deficient data. In addition, the observation strategy of TD-GAC is described, and the pipeline of data reduction is tested.

  19. Neutron stars

    International Nuclear Information System (INIS)

    Irvine, J.M.

    1978-01-01

    The subject is covered in chapters entitled: introduction (resume of stellar evolution, gross characteristics of neutron stars); pulsars (pulsar characteristics, pulsars as neutron stars); neutron star temperatures (neutron star cooling, superfluidity and superconductivity in neutron stars); the exterior of neutron stars (the magnetosphere, the neutron star 'atmosphere', pulses); neutron star structure; neutron star equations of state. (U.K.)

  20. GAUGE R&R FOR AN OPTICAL MICROMETER INDUSTRIAL TYPE MACHINE

    Directory of Open Access Journals (Sweden)

    Georgia A. Louka

    2010-12-01

    Full Text Available The measurement of the uncertainty of a metric system, as 'Gauge R&R' and the collation of results between the Xbar & R and the ANOVA method, are extended in this essay. In an academic school laboratory we accomplished a sequence of measurements with the use of an Optical Micrometer Industrial Type Machine (MUL 300. This paper analyzes the measurement system that used in the laboratory and checks the reasons of the variability's provocation that observed in the machine, between the theoretical calculations and measurements. In order to find out this problem, we will use the 'Gage Repeatability and Reproducibility' technique of Measurement System Analysis (M.S.A.. This technique uses analysis of variance. In addition, will use Minitab program in order to find out the factors that we have in the whole experiment as enlarge the problem of measurements. In this paper, a statistical method using the correlation between Gage R&R and process capability indices is proposed for evaluating the adequacy of the acceptance criteria of P/T ratio. Finally, a comparative analysis has also been performed for evaluating the accuracy of Gage R&R between two methods (ANOVA and R- Xbar method. Hopefully, the results of this research can provide a useful reference for quality practitioners in various industries.

  1. Nahid Sırrı Örik’in Romanlarında Aile

    OpenAIRE

    Sayar, Feyza

    2013-01-01

    In this study, The six novels of Nahid Sırrı Örik Kıskanmak, Yıldız Olmak Kolay mı?, Tersine Giden Yol, Gece Olmadan, Sultan Hamid Düşerken, Kozmopolitler were examined in terms of family approach. In the first section of the study, Nahid Sırrı Örik's life, art and works were mentioned. In the second section, generally novels in Turkish Literature which are on the subject of family were mentioned. In the third section, the plot is studied. In the fourth section family and in the fifth sect...

  2. Qualidade fisiológica e teor de lignina no tegumento de sementes de soja convencional e transgênica RR submetidas a diferentes épocas de colheita Physiological quality and lignin content in the coat seeds of conventional and RR transgenic soybean submitted to different harvest periods

    Directory of Open Access Journals (Sweden)

    Cristiane Fortes Gris

    2010-04-01

    Full Text Available Têm-se levantado à hipótese de que cultivares de soja RR possuem teores de lignina superiores aos convencionais, o que proporciona maior resistência a danos mecânicos e maior impermeabilidade do tegumento das sementes. Objetivou-se avaliar a qualidade fisiológica e o teor de lignina no tegumento das sementes de soja convencional e RR colhidas em três épocas, em Lavras-MG. Para tanto, as sementes colhidas nos estádios R7, R8 e após 20 dias de retardamento da colheita (R8+20, foram submetidas aos testes para avaliação da qualidade fisiológica e teor de lignina. As cultivares convencionais e RR avaliadas foram: BRS 133 vs BRS 245 RR, BRS 134 vs BRS 247 RR, Conquista vs Valiosa RR, Celeste vs Baliza RR e Jataí vs Silvânia RR. Foram realizados os testes de peso de mil sementes, germinação, envelhecimento acelerado, condutividade elétrica, dano mecânico, índice de velocidade de emergência, germinação após a imersão das sementes em água e teor de lignina no tegumento de sementes. Com exceção do teor de lignina no tegumento de sementes para o contraste Jataí vs Silvânia RR, não foram observadas diferenças entre os materiais RR e convencional, tendo, neste caso, a cv Silvânia RR apresentado resultados superiores aos da convencional. No entanto, houve diferença de comportamento entre os cultivares quanto à tolerância ao retardamento da colheita. Observou-se redução significativa na porcentagem de germinação e vigor das sementes avaliadas com o retardamento da colheita.One has raised the hypothesis that the RR soybean cultivars posses lignin contents higher than those of the conventional ones. The present work was conducted with the purpose of evaluating the physiological quality and lignin content in the coat of the conventional and RR soybean seeds collected in three times in Lavras-MG. To that end, the seeds collected at stages R7, R8 and after 20 days of collection delay (R8+20 were submitted to the tests for

  3. Calcium abundance of RR Lyrae variables in ω Centaurri and M22

    International Nuclear Information System (INIS)

    Manduca, A.; Bell, R.A.

    1978-01-01

    Freeman and Rodgers observed 25 RR Lyrae variables in ω Cen and reported a range in calcium abundance from [Ca/H] = -0.4 to -1.6. This result, however, has been difficult to reconcile with other recent studies of the giant branch of ω Cen. with a model-atmosphere grid covering the physical parameters expected for RR Lyrae variables, Freeman and Rodgers's data were reanalyzed, by use of their basic method of theoretical relations among the equivalent widths of the K, H4b, and H delta lines and [Ca/H] but with an alternative, synthetic-spectrum approach to the calibration of these relations. When interpreted with the present calibration, the data yield a range in calcium abundance from [Ca/H] = -1.0 to -1.9 for the ω Cen RR Lyrae variables. This calibration applied to the M22 data of Butler et al gives [Ca/H] = -1.25 for M22. 2 figures, 1 table

  4. Biofuel and Biochemical Analysis of Amphora coffeaeformis RR03, a Novel Marine Diatom, Cultivated in an Open Raceway Pond

    Directory of Open Access Journals (Sweden)

    Muthu Ganesan Rajaram

    2018-05-01

    Full Text Available (1 Background: To increase the biochemical productivity and to reduce the production cost of microalgal biodiesel, this study aimed to investigate the effects of CO2 on biomass, fatty acids, carbon-hydrogen, and biochemical accumulation of the marine diatom, Amphora coffeaeformis RR03 (A. coffeaeformis RR03. (2 Methods: Fatty acid composition of the dry biomass of A. coffeaeformis RR03 was analysed using Gas chromatography-mass spectrometry (GC-MS. (3 Results: The results showed that A. coffeaeformis RR03 contained high biomass productivity and biochemical composition in different cultivation conditions. A. coffeaeformis RR03 showed maximum growth of 5.2 × 106/mL on 21st day cultivation under CO2 supply. The bio-crude oil production from A. coffeaeformis RR03 was 36.19 megajoule (MJ. GC-MS analysis found that the dry biomass of A. coffeaeformis RR03 contained maximum of 47.72% fatty acids of 16-octadecanoic acid methyl ester (10:12 and 19.58% pentadecanoic acid, 13-methyl-, and methyl ester (9.24. (4 Conclusion: The results of this study may suggest that a novel diatom of A. coffeaeformis RR03 could be a suitable candidate for biocrude production in order to meet the future demand of energy.

  5. Neutron Star Science with the NuSTAR

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, J. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-10-16

    The Nuclear Spectroscopic Telescope Array (NuSTAR), launched in June 2012, helped scientists obtain for the first time a sensitive high-­energy X-­ray map of the sky with extraordinary resolution. This pioneering telescope has aided in the understanding of how stars explode and neutron stars are born. LLNL is a founding member of the NuSTAR project, with key personnel on its optics and science team. We used NuSTAR to observe and analyze the observations of different neutron star classes identified in the last decade that are still poorly understood. These studies not only help to comprehend newly discovered astrophysical phenomena and emission processes for members of the neutron star family, but also expand the utility of such observations for addressing broader questions in astrophysics and other physics disciplines. For example, neutron stars provide an excellent laboratory to study exotic and extreme phenomena, such as the equation of state of the densest matter known, the behavior of matter in extreme magnetic fields, and the effects of general relativity. At the same time, knowing their accurate populations has profound implications for understanding the life cycle of massive stars, star collapse, and overall galactic evolution.

  6. Selections from 2017: Computers Help Us Map Our Home

    Science.gov (United States)

    Kohler, Susanna

    2017-12-01

    Editors note:In these last two weeks of 2017, well be looking at a few selections that we havent yet discussed on AAS Nova from among the most-downloaded paperspublished in AAS journals this year. The usual posting schedule will resume in January.Machine-Learned Identification of RR Lyrae Stars from Sparse, Multi-Band Data: The PS1 SamplePublished April2017Main takeaway:A sample of RR Lyrae variable stars was built from thePan-STARRS1 (PS1) survey by a team led byBranimir Sesar (Max Planck Institute for Astronomy, Germany). The sample of45,000 starsrepresentsthe widest (three-fourthsof the sky) and deepest (reaching 120 kpc) sample of RR Lyrae stars to date.Why its interesting:Its challengingto understand the overall shape and behaviorof our galaxy because were stuck on the inside of it. RR Lyrae stars are a useful tool for this purpose: they can be used as tracers to map out the Milky Ways halo. The authors large sample of RR Lyrae stars from PS1 combined withproper-motion measurements from Gaia and radial-velocity measurements from multi-object spectroscopic surveys could become thepremier source for studying the structure, kinematics, and the gravitational potential of our galaxys outskirts.How they were found:The black dots show the distribution of the 45,000 probable RR Lyrae stars in the authors sample. [Sesar et al. 2017]The 45,000 stars in this sample were selected not by humans, but by computer.The authors used machine-learning algorithms to examine the light curvesin the Pan-STARRS1 sample and identify the characteristic brightness variations of RR Lyrae stars lying in the galactic halo. These techniques resulted in a very pure and complete sample, and the authors suggest that this approachmay translate well to othersparse,multi-band data sets such asthat from the upcomingLarge Synoptic Survey Telescope (LSST) galactic plane sub-survey.CitationBranimir Sesar et al 2017 AJ 153 204. doi:10.3847/1538-3881/aa661b

  7. Response of Haloalkaliphilic Archaeon Natronococcus Jeotgali RR17 to Hypergravity

    Science.gov (United States)

    Thombre, Rebecca S.; Bhalerao, Aniruddha R.; Shinde, Vinaya D.; Dhar, Sunil Kumar; Shouche, Yogesh S.

    2017-06-01

    The survival of archaeabacteria in extreme inhabitable environments on earth that challenge organismic survival is ubiquitously known. However, the studies related to the effect of hypergravity on the growth and proliferation of archaea are unprecedented. The survival of organisms in hypergravity and rocks in addition to resistance to cosmic radiations, pressure and other extremities is imperative to study the possibilities of microbial travel between planets and endurance in hyperaccelerative forces faced during ejection of rocks from planets. The current investigation highlights the growth of an extremophilic archaeon isolated from a rocky substrate in hypergravity environment. The haloalkaliphilic archaeon, Natronococcus jeotgali RR17 was isolated from an Indian laterite rock, submerged in the Arabian sea lining Coastal Maharashtra, India. The endolithic haloarchaeon was subjected to hypergravity from 56 - 893 X gusing acceleration generated by centrifugal rotation. The cells of N. jeotgali RR17 proliferated and demonstrated good growth in hypergravity (223 X g). This is the first report on isolation of endolithic haloarchaeon N. jeotgali RR17 from an Indian laterite rock and its ability to proliferate in hypergravity. The present study demonstrates the ability of microbial life to survive and proliferate in hypergravity. Thus the inability of organismic growth in hypergravity may no longer be a limitation for astrobiology studies related to habitability of substellar objects, brown dwarfs and other planetary bodies in the universe besides planet earth.

  8. O stars and Wolf-Rayet stars

    International Nuclear Information System (INIS)

    Conti, P.S.; Underhill, A.B.; Jordan, S.; Thomas, R.

    1988-01-01

    Basic information is given about O and Wolf-Rayet stars indicating how these stars are defined and what their chief observable properties are. Part 2 of the volume discussed four related themes pertaining to the hottest and most luminous stars. Presented are: an observational overview of the spectroscopic classification and extrinsic properties of O and Wolf-Rayet stars; the intrinsic parameters of luminosity, effective temperature, mass, and composition of the stars, and a discussion of their viability; stellar wind properties; and the related issues concerning the efforts of stellar radiation and wind on the immediate interstellar environment are presented

  9. O stars and Wolf-Rayet stars

    Science.gov (United States)

    Conti, Peter S.; Underhill, Anne B.; Jordan, Stuart (Editor); Thomas, Richard (Editor)

    1988-01-01

    Basic information is given about O and Wolf-Rayet stars indicating how these stars are defined and what their chief observable properties are. Part 2 of the volume discussed four related themes pertaining to the hottest and most luminous stars. Presented are: an observational overview of the spectroscopic classification and extrinsic properties of O and Wolf-Rayet stars; the intrinsic parameters of luminosity, effective temperature, mass, and composition of the stars, and a discussion of their viability; stellar wind properties; and the related issues concerning the efforts of stellar radiation and wind on the immediate interstellar environment are presented.

  10. A robust star identification algorithm with star shortlisting

    Science.gov (United States)

    Mehta, Deval Samirbhai; Chen, Shoushun; Low, Kay Soon

    2018-05-01

    A star tracker provides the most accurate attitude solution in terms of arc seconds compared to the other existing attitude sensors. When no prior attitude information is available, it operates in "Lost-In-Space (LIS)" mode. Star pattern recognition, also known as star identification algorithm, forms the most crucial part of a star tracker in the LIS mode. Recognition reliability and speed are the two most important parameters of a star pattern recognition technique. In this paper, a novel star identification algorithm with star ID shortlisting is proposed. Firstly, the star IDs are shortlisted based on worst-case patch mismatch, and later stars are identified in the image by an initial match confirmed with a running sequential angular match technique. The proposed idea is tested on 16,200 simulated star images having magnitude uncertainty, noise stars, positional deviation, and varying size of the field of view. The proposed idea is also benchmarked with the state-of-the-art star pattern recognition techniques. Finally, the real-time performance of the proposed technique is tested on the 3104 real star images captured by a star tracker SST-20S currently mounted on a satellite. The proposed technique can achieve an identification accuracy of 98% and takes only 8.2 ms for identification on real images. Simulation and real-time results depict that the proposed technique is highly robust and achieves a high speed of identification suitable for actual space applications.

  11. 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.

  12. Statistical investigation of flare stars. III. Flare stars in the general galactic star field

    International Nuclear Information System (INIS)

    Mirzoyan, L.V.; Ambaryan, V.V.; Garibdzhanyan, A.T.; Mirzoyan, A.L.

    1989-01-01

    Some questions relating to the existence of a large number of flare stars in the general star field of the Galaxy are discussed. It is shown that only a small proportion of them can be found by photographic observations, and the fraction of field flare stars among such stars found in the regions of star clusters and associations does not exceed 10%. The ratio of the numbers of flare stars of the foreground and the background for a particular system depends on its distance, reaching zero at a distance of about 500 pc. The spatial density of flare stars in the Pleiades is at least two orders of magnitude greater than in the general galactic field. A lower limit for the number of flare stars in the Galaxy is estimated at 4.2 ·10 9 , and the number of nonflare red dwarfs at 2.1·10 10 . There are grounds for believing that they were all formed in star clusters and associations

  13. [Primary Study on Predicting the Termination of Paroxysmal Atrial Fibrillation Based on a Novel RdR RR Intervals Scatter Plot].

    Science.gov (United States)

    Lu, Hongwei; Zhang, Chenxi; Sun, Ying; Hao, Zhidong; Wang, Chunfang; Tian, Jiajia

    2015-08-01

    Predicting the termination of paroxysmal atrial fibrillation (AF) may provide a signal to decide whether there is a need to intervene the AF timely. We proposed a novel RdR RR intervals scatter plot in our study. The abscissa of the RdR scatter plot was set to RR intervals and the ordinate was set as the difference between successive RR intervals. The RdR scatter plot includes information of RR intervals and difference between successive RR intervals, which captures more heart rate variability (HRV) information. By RdR scatter plot analysis of one minute RR intervals for 50 segments with non-terminating AF and immediately terminating AF, it was found that the points in RdR scatter plot of non-terminating AF were more decentralized than the ones of immediately terminating AF. By dividing the RdR scatter plot into uniform grids and counting the number of non-empty grids, non-terminating AF and immediately terminating AF segments were differentiated. By utilizing 49 RR intervals, for 20 segments of learning set, 17 segments were correctly detected, and for 30 segments of test set, 20 segments were detected. While utilizing 66 RR intervals, for 18 segments of learning set, 16 segments were correctly detected, and for 28 segments of test set, 20 segments were detected. The results demonstrated that during the last one minute before the termination of paroxysmal AF, the variance of the RR intervals and the difference of the neighboring two RR intervals became smaller. The termination of paroxysmal AF could be successfully predicted by utilizing the RdR scatter plot, while the predicting accuracy should be further improved.

  14. Neutron star/red giant encounters in globular clusters

    International Nuclear Information System (INIS)

    Bailyn, C.D.

    1988-01-01

    The author presents a simple expression for the amount by which xsub(crit) is diminished as a star evolves xsub(crit) Rsub(crit)/R*, where Rsub(crit) is the maximum distance of closest approach between two stars for which the tidal energy is sufficient to bind the system, and R* is the radius of the star on which tides are being raised. Also it is concluded that tidal capture of giants by neutron stars resulting in binary systems is unlikely in globular clusters. However, collisions between neutron stars and red giants, or an alternative process involving tidal capture of a main-sequence star into an initially detached binary system, may result either in rapidly rotating neutron stars or in white dwarf/neutron star binaries. (author)

  15. Flow distribution in ET-RR-1 core

    International Nuclear Information System (INIS)

    Khattab, M.; Mina, A.R.

    1989-01-01

    In nuclear reactors the flow may be arranged through individual bundles by orifices to achieve better thermal performance. A model based on constant pressure drop across different core regions is developed to determine the flow distribution in reactor core. The friction and grids in the bundles as well as the orifices diameters have an influence on modifying the flow distribution. The application of the proposed model on ET-RR-1 gives reasonable prediction of flow distribution

  16. Symbiotic stars

    International Nuclear Information System (INIS)

    Boyarchuk, A.A.

    1975-01-01

    There are some arguments that the symbiotic stars are binary, where one component is a red giant and the other component is a small hot star which is exciting a nebula. The symbiotic stars belong to the old disc population. Probably, symbiotic stars are just such an evolutionary stage for double stars as planetary nebulae for single stars. (Auth.)

  17. Quark core stars, quark stars and strange stars

    International Nuclear Information System (INIS)

    Grassi, F.

    1988-01-01

    A recent one flavor quark matter equation of state is generalized to several flavors. It is shown that quarks undergo a first order phase transition. In addition, this equation of state depends on just one parameter in the two flavor case, two parameters in the three flavor case, and these parameters are constrained by phenomenology. This equation of state is then applied to the hadron-quark transition in neutron stars and the determination of quark star stability, the investigation of strange matter stability and possible strange star existence. 43 refs., 6 figs

  18. Kinematic and spatial distributions of barium stars - are the barium stars and Am stars related?

    International Nuclear Information System (INIS)

    Hakkila, J.

    1989-01-01

    The possibility of an evolutionary link between Am stars and barium stars is considered, and an examination of previous data suggests that barium star precursors are main-sequence stars of intermediate mass, are most likely A and/or F dwarfs, and are intermediate-mass binaries with close to intermediate orbital separations. The possible role of mass transfer in the later development of Am systems is explored. Mass transfer and loss from systems with a range of masses and orbital separations may explain such statistical peculiarities of barium stars as the large dispersion in absolute magnitude, the large range of elemental abundances from star to star, and the small number of stars with large peculiar velocities. 93 refs

  19. Double-mode pulsation

    International Nuclear Information System (INIS)

    Cox, A.N.

    1982-01-01

    Double mode pulsation is a very pervasive phenomenon in stars all over the Hertzsprung-Russell diagram. In order of increasing radius, examples are: ZZ Ceti stars, the sun, the delta Scuti stars, RR Lyrae variables, the β Cephei variables and those related to them, Cepheids, and maybe even the Mira stars. These many modes have been interpreted as both radial and nonradial modes, but in many cases the actual mode has not been clearly identified. Yellow giants seem to be the most simple pulsators with a large majority of the RR Lyrae variables and Cepheids showing only one pulsation period. We limit this review to those very few cases for classical Cepheids and RR Lyrae variables which display two modes. For these we know many facts about these stars, but the actual cause of the pulsation in two modes simultaneously remains unknown

  20. Measurement and theory of turbulence in RR Lyrae

    International Nuclear Information System (INIS)

    Benz, W.; Stellingwerf, R.F.

    1985-01-01

    CORAVEL observations of time-dependent turbulence in RR Lyrae are presented. Variation in the width of the mean velocity correlation function implies turbulent velocities that peak at 10 to 15 km/sec for a brief interval of phase near minimum radius. Comparison with a nonlinear pulsation model shows that these amplitudes of the turbulent velocity are expected near the hydrogen ionization zone, again only near minimum radius

  1. STAR FORMATION HISTORY OF THE MILKY WAY HALO TRACED BY THE OOSTERHOFF DICHOTOMY AMONG GLOBULAR CLUSTERS

    International Nuclear Information System (INIS)

    Jang, Sohee; Lee, Young-Wook

    2015-01-01

    In our recent investigation of the Oosterhoff dichotomy in the multiple population paradigm, we have suggested that the RR Lyrae variables in the globular clusters (GCs) of Oosterhoff groups I, II, and III are produced mostly by first, second, and third generation stars (G1, G2, and G3), respectively. Here we show, for the first time, that the observed dichotomies in the inner and outer halo GCs can be naturally reproduced when these models are extended to all metallicity regimes, while maintaining reasonable agreements in the horizontal-branch type versus [Fe/H] correlations. In order to achieve this, however, specific star formation histories are required for the inner and outer halos. In the inner halo GCs, the star formation commenced and ceased earlier with a relatively short formation timescale between the subpopulations (∼0.5 Gyr), while in the outer halo, the formation of G1 was delayed by ∼0.8 Gyr with a more extended timescale between G1 and G2 (∼1.4 Gyr). This is consistent with the dual origin of the Milky Way halo. Despite the difference in detail, our models show that the Oosterhoff period groups observed in both outer and inner halo GCs are all manifestations of the “population-shift” effect within the instability strip, for which the origin can be traced back to the two or three discrete episodes of star formation in GCs

  2. Build-up of actinides in irradiated fuel rods of the ET-RR-1 reactor

    Energy Technology Data Exchange (ETDEWEB)

    Adib, M.; Naguib, K.; Morcos, H.N

    2001-09-01

    The content concentrations of actinides are calculated as a function of operating reactor regime and cooling time at different percentage of fuel burn-up. The build-up transmutation equations of actinides content in an irradiated fuel are solved numerically .A computer code BAC was written to operate on a PC computer to provide the required calculations. The fuel element of 10% {sup 235}U enrichment of ET-RR-1 reactor was taken as an example for calculations using the BAC code. The results are compared with other calculations for the ET-RR-1 fuel rod. An estimation of fissile build-up content of a proposed new fuel of 20% {sup 235}U enrichment for ET-RR-1 reactor is given. The sensitivity coefficients of build-up plutonium concentrations as a function of cross-section data uncertainties are also calculated.

  3. Probabilistic safety analysis for control rod drive system of ET-RR-1

    International Nuclear Information System (INIS)

    Nasr, M.; Nasser, O.

    1988-01-01

    The International Atomic Energy Agency (IAEA) co-ordinated a Research programme on Probabilistic Safety Analysis (PSA) for research reactors; with the participation of several countries. In the framework of this project (Project Int. 9/063) the Egyptian Atomic Energy Authority decided to perform a PSA study on the ET-RR-1 (Egypt Thermal Research Reactor). The study is conducted in collaboration between the nuclear regulatory and safety centre (NRSC) and the reactor department of the nuclear research centre at Inchass. The present work is a part of the PSA study on ET-RR- it is concerning a probabilistic safety analysis of the control rod drive mechanism

  4. The ISLAnds Project. III. Variable Stars in Six Andromeda Dwarf Spheroidal Galaxies

    Science.gov (United States)

    Martínez-Vázquez, Clara E.; Monelli, Matteo; Bernard, Edouard J.; Gallart, Carme; Stetson, Peter B.; Skillman, Evan D.; Bono, Giuseppe; Cassisi, Santi; Fiorentino, Giuliana; McQuinn, Kristen B. W.; Cole, Andrew A.; McConnachie, Alan W.; Martin, Nicolas F.; Dolphin, Andrew E.; Boylan-Kolchin, Michael; Aparicio, Antonio; Hidalgo, Sebastian L.; Weisz, Daniel R.

    2017-12-01

    We present a census of variable stars in six M31 dwarf spheroidal satellites observed with the Hubble Space Telescope. We detect 870 RR Lyrae (RRL) stars in the fields of And I (296), II (251), III (111), XV (117), XVI (8), and XXVIII (87). We also detect a total of 15 Anomalous Cepheids, three eclipsing binaries, and seven field RRL stars compatible with being members of the M31 halo or the Giant Stellar Stream. We derive robust and homogeneous distances to the six galaxies using different methods based on the properties of the RRL stars. Working with the up-to-date set of Period-Wesenheit (I, B-I) relations published by Marconi et al., we obtain distance moduli of μ 0 = [24.49, 24.16, 24.36, 24.42, 23.70, 24.43] mag (respectively), with systematic uncertainties of 0.08 mag and statistical uncertainties <0.11 mag. We have considered an enlarged sample of 16 M31 satellites with published variability studies, and compared their pulsational observables (e.g., periods and amplitudes) with those of 15 Milky Way satellites for which similar data are available. The properties of the (strictly old) RRL in both satellite systems do not show any significant difference. In particular, we found a strikingly similar correlation between the mean period distribution of the fundamental RRL pulsators (RRab) and the mean metallicities of the galaxies. This indicates that the old RRL progenitors were similar at the early stage in the two environments, suggesting very similar characteristics for the earliest stages of evolution of both satellite systems. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs 13028 and 13739.

  5. A Brightness-Referenced Star Identification Algorithm for APS Star Trackers

    Science.gov (United States)

    Zhang, Peng; Zhao, Qile; Liu, Jingnan; Liu, Ning

    2014-01-01

    Star trackers are currently the most accurate spacecraft attitude sensors. As a result, they are widely used in remote sensing satellites. Since traditional charge-coupled device (CCD)-based star trackers have a limited sensitivity range and dynamic range, the matching process for a star tracker is typically not very sensitive to star brightness. For active pixel sensor (APS) star trackers, the intensity of an imaged star is valuable information that can be used in star identification process. In this paper an improved brightness referenced star identification algorithm is presented. This algorithm utilizes the k-vector search theory and adds imaged stars' intensities to narrow the search scope and therefore increase the efficiency of the matching process. Based on different imaging conditions (slew, bright bodies, etc.) the developed matching algorithm operates in one of two identification modes: a three-star mode, and a four-star mode. If the reference bright stars (the stars brighter than three magnitude) show up, the algorithm runs the three-star mode and efficiency is further improved. The proposed method was compared with other two distinctive methods the pyramid and geometric voting methods. All three methods were tested with simulation data and actual in orbit data from the APS star tracker of ZY-3. Using a catalog composed of 1500 stars, the results show that without false stars the efficiency of this new method is 4∼5 times that of the pyramid method and 35∼37 times that of the geometric method. PMID:25299950

  6. 76 FR 78805 - Airworthiness Directives; Rolls-Royce plc (RR) RB211-Trent 800 Series Turbofan Engines

    Science.gov (United States)

    2011-12-20

    ... Airworthiness Directives; Rolls-Royce plc (RR) RB211-Trent 800 Series Turbofan Engines AGENCY: Federal Aviation... all Rolls-Royce plc (RR) RB211-Trent 800 Series Turbofan Engines. This AD results from mandatory... inspection of the FOHE mounts. We did not change the AD based on this comment. Request To Add Requirement To...

  7. A Probabilistic Approach to Fitting Period–luminosity Relations and Validating Gaia Parallaxes

    Energy Technology Data Exchange (ETDEWEB)

    Sesar, Branimir; Fouesneau, Morgan; Bailer-Jones, Coryn A. L.; Gould, Andy; Rix, Hans-Walter [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Price-Whelan, Adrian M., E-mail: bsesar@mpia.de [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

    2017-04-01

    Pulsating stars, such as Cepheids, Miras, and RR Lyrae stars, are important distance indicators and calibrators of the “cosmic distance ladder,” and yet their period–luminosity–metallicity (PLZ) relations are still constrained using simple statistical methods that cannot take full advantage of available data. To enable optimal usage of data provided by the Gaia mission, we present a probabilistic approach that simultaneously constrains parameters of PLZ relations and uncertainties in Gaia parallax measurements. We demonstrate this approach by constraining PLZ relations of type ab RR Lyrae stars in near-infrared W 1 and W 2 bands, using Tycho- Gaia Astrometric Solution (TGAS) parallax measurements for a sample of ≈100 type ab RR Lyrae stars located within 2.5 kpc of the Sun. The fitted PLZ relations are consistent with previous studies, and in combination with other data, deliver distances precise to 6% (once various sources of uncertainty are taken into account). To a precision of 0.05 mas (1 σ ), we do not find a statistically significant offset in TGAS parallaxes for this sample of distant RR Lyrae stars (median parallax of 0.8 mas and distance of 1.4 kpc). With only minor modifications, our probabilistic approach can be used to constrain PLZ relations of other pulsating stars, and we intend to apply it to Cepheid and Mira stars in the near future.

  8. Menopause, hormone replacement and RR and QT modulation during sleep

    Czech Academy of Sciences Publication Activity Database

    Lanfranchi, P. A.; Gosselin, N.; Kára, T.; Jurák, Pavel; Somers, V. K.; Denesle, R.; Petit, D.; Carrier, J.; Nadeau, R.; Montplaisir, J.

    2005-01-01

    Roč. 6, č. 6 (2005), s. 561-566 ISSN 1389-9457 R&D Projects: GA ČR(CZ) GA102/05/0402 Keywords : Sleep * Menopause * RR interval * QT interval * Gender * Hormones Subject RIV: FS - Medical Facilities ; Equipment Impact factor: 2.711, year: 2005

  9. Design and application of star map simulation system for star sensors

    Science.gov (United States)

    Wu, Feng; Shen, Weimin; Zhu, Xifang; Chen, Yuheng; Xu, Qinquan

    2013-12-01

    Modern star sensors are powerful to measure attitude automatically which assure a perfect performance of spacecrafts. They achieve very accurate attitudes by applying algorithms to process star maps obtained by the star camera mounted on them. Therefore, star maps play an important role in designing star cameras and developing procession algorithms. Furthermore, star maps supply significant supports to exam the performance of star sensors completely before their launch. However, it is not always convenient to supply abundant star maps by taking pictures of the sky. Thus, star map simulation with the aid of computer attracts a lot of interests by virtue of its low price and good convenience. A method to simulate star maps by programming and extending the function of the optical design program ZEMAX is proposed. The star map simulation system is established. Firstly, based on analyzing the working procedures of star sensors to measure attitudes and the basic method to design optical system by ZEMAX, the principle of simulating star sensor imaging is given out in detail. The theory about adding false stars and noises, and outputting maps is discussed and the corresponding approaches are proposed. Then, by external programming, the star map simulation program is designed and produced. Its user interference and operation are introduced. Applications of star map simulation method in evaluating optical system, star image extraction algorithm and star identification algorithm, and calibrating system errors are presented completely. It was proved that the proposed simulation method provides magnificent supports to the study on star sensors, and improves the performance of star sensors efficiently.

  10. A Near-infrared RR Lyrae Census along the Southern Galactic Plane: The Milky Way’s Stellar Fossil Brought to Light

    Science.gov (United States)

    Dékány, István; Hajdu, Gergely; Grebel, Eva K.; Catelan, Márcio; Elorrieta, Felipe; Eyheramendy, Susana; Majaess, Daniel; Jordán, Andrés

    2018-04-01

    RR Lyrae stars (RRLs) are tracers of the Milky Way’s fossil record, holding valuable information on its formation and early evolution. Owing to the high interstellar extinction endemic to the Galactic plane, distant RRLs lying at low Galactic latitudes have been elusive. We attained a census of 1892 high-confidence RRLs by exploiting the near-infrared photometric database of the VVV survey’s disk footprint spanning ∼70° of Galactic longitude, using a machine-learned classifier. Novel data-driven methods were employed to accurately characterize their spatial distribution using sparsely sampled multi-band photometry. The RRL metallicity distribution function (MDF) was derived from their K s -band light-curve parameters using machine-learning methods. The MDF shows remarkable structural similarities to both the spectroscopic MDF of red clump giants and the MDF of bulge RRLs. We model the MDF with a multi-component density distribution and find that the number density of stars associated with the different model components systematically changes with both the Galactocentric radius and vertical distance from the Galactic plane, equivalent to weak metallicity gradients. Based on the consistency with results from the ARGOS survey, three MDF modes are attributed to the old disk populations, while the most metal-poor RRLs are probably halo interlopers. We propose that the dominant [Fe/H] component with a mean of ‑1 dex might correspond to the outskirts of an ancient Galactic spheroid or classical bulge component residing in the central Milky Way. The physical origins of the RRLs in this study need to be verified by kinematical information.

  11. Regular Generalized Star Star closed sets in Bitopological Spaces

    OpenAIRE

    K. Kannan; D. Narasimhan; K. Chandrasekhara Rao; R. Ravikumar

    2011-01-01

    The aim of this paper is to introduce the concepts of τ1τ2-regular generalized star star closed sets , τ1τ2-regular generalized star star open sets and study their basic properties in bitopological spaces.

  12. I-Love relations for incompressible stars and realistic stars

    Science.gov (United States)

    Chan, T. K.; Chan, AtMa P. O.; Leung, P. T.

    2015-02-01

    In spite of the diversity in the equations of state of nuclear matter, the recently discovered I-Love-Q relations [Yagi and Yunes, Science 341, 365 (2013), 10.1126/science.1236462], which relate the moment of inertia, tidal Love number (deformability), and the spin-induced quadrupole moment of compact stars, hold for various kinds of realistic neutron stars and quark stars. While the physical origin of such universality is still a current issue, the observation that the I-Love-Q relations of incompressible stars can well approximate those of realistic compact stars hints at a new direction to approach the problem. In this paper, by establishing recursive post-Minkowskian expansion for the moment of inertia and the tidal deformability of incompressible stars, we analytically derive the I-Love relation for incompressible stars and show that the so-obtained formula can be used to accurately predict the behavior of realistic compact stars from the Newtonian limit to the maximum mass limit.

  13. Occurrence and core-envelope structure of 1-4× Earth-size planets around Sun-like stars.

    Science.gov (United States)

    Marcy, Geoffrey W; Weiss, Lauren M; Petigura, Erik A; Isaacson, Howard; Howard, Andrew W; Buchhave, Lars A

    2014-09-02

    Small planets, 1-4× the size of Earth, are extremely common around Sun-like stars, and surprisingly so, as they are missing in our solar system. Recent detections have yielded enough information about this class of exoplanets to begin characterizing their occurrence rates, orbits, masses, densities, and internal structures. The Kepler mission finds the smallest planets to be most common, as 26% of Sun-like stars have small, 1-2 R⊕ planets with orbital periods under 100 d, and 11% have 1-2 R⊕ planets that receive 1-4× the incident stellar flux that warms our Earth. These Earth-size planets are sprinkled uniformly with orbital distance (logarithmically) out to 0.4 the Earth-Sun distance, and probably beyond. Mass measurements for 33 transiting planets of 1-4 R⊕ show that the smallest of them, R planets. Their densities increase with increasing radius, likely caused by gravitational compression. Including solar system planets yields a relation: ρ = 2:32 + 3:19 R=R ⊕ [g cm(-3)]. Larger planets, in the radius range 1.5-4.0 R⊕, have densities that decline with increasing radius, revealing increasing amounts of low-density material (H and He or ices) in an envelope surrounding a rocky core, befitting the appellation ''mini-Neptunes.'' The gas giant planets occur preferentially around stars that are rich in heavy elements, while rocky planets occur around stars having a range of heavy element abundances. Defining habitable zones remains difficult, without benefit of either detections of life elsewhere or an understanding of life's biochemical origins.

  14. Search for OB stars running away from young star clusters. II. The NGC 6357 star-forming region

    Science.gov (United States)

    Gvaramadze, V. V.; Kniazev, A. Y.; Kroupa, P.; Oh, S.

    2011-11-01

    Dynamical few-body encounters in the dense cores of young massive star clusters are responsible for the loss of a significant fraction of their massive stellar content. Some of the escaping (runaway) stars move through the ambient medium supersonically and can be revealed via detection of their bow shocks (visible in the infrared, optical or radio). In this paper, which is the second of a series of papers devoted to the search for OB stars running away from young ( ≲ several Myr) Galactic clusters and OB associations, we present the results of the search for bow shocks around the star-forming region NGC 6357. Using the archival data of the Midcourse Space Experiment (MSX) satellite and the Spitzer Space Telescope, and the preliminary data release of the Wide-Field Infrared Survey Explorer (WISE), we discovered seven bow shocks, whose geometry is consistent with the possibility that they are generated by stars expelled from the young (~1-2 Myr) star clusters, Pismis 24 and AH03 J1725-34.4, associated with NGC 6357. Two of the seven bow shocks are driven by the already known OB stars, HD 319881 and [N78] 34. Follow-up spectroscopy of three other bow-shock-producing stars showed that they are massive (O-type) stars as well, while the 2MASS photometry of the remaining two stars suggests that they could be B0 V stars, provided that both are located at the same distance as NGC 6357. Detection of numerous massive stars ejected from the very young clusters is consistent with the theoretical expectation that star clusters can effectively lose massive stars at the very beginning of their dynamical evolution (long before the second mechanism for production of runaway stars, based on a supernova explosion in a massive tight binary system, begins to operate) and lends strong support to the idea that probably all field OB stars have been dynamically ejected from their birth clusters. A by-product of our search for bow shocks around NGC 6357 is the detection of three circular

  15. Do All O Stars Form in Star Clusters?

    Science.gov (United States)

    Weidner, C.; Gvaramadze, V. V.; Kroupa, P.; Pflamm-Altenburg, J.

    The question whether or not massive stars can form in isolation or only in star clusters is of great importance for the theory of (massive) star formation as well as for the stellar initial mass function of whole galaxies (IGIMF-theory). While a seemingly easy question it is rather difficult to answer. Several physical processes (e.g. star-loss due to stellar dynamics or gas expulsion) and observational limitations (e.g. dust obscuration of young clusters, resolution) pose severe challenges to answer this question. In this contribution we will present the current arguments in favour and against the idea that all O stars form in clusters.

  16. Estimating the parameters of globular cluster M 30 (NGC 7099) from time-series photometry

    DEFF Research Database (Denmark)

    Kains, N.; Bramich, D.M.; Figuera Jaimes, R.

    2013-01-01

    Aims. We present the analysis of 26 nights of V and I time-series observations from 2011 and 2012 of the globular cluster M 30 (NGC 7099). We used our data to search for variable stars in this cluster and refine the periods of known variables; we then used our variable star light curves to derive...... values for the cluster's parameters. Methods. We used difference image analysis to reduce our data to obtain high-precision light curves of variable stars. We then estimated the cluster parameters by performing a Fourier decomposition of the light curves of RR Lyrae stars for which a good period estimate...... stars to derive cluster parameters using empirical relations. We find a cluster metallicity [Fe/H]ZW =-2.01 ± 0.04, or [Fe/H]UVES =-2.11 ± 0.06, and a distance of 8.32 ± 0.20 kpc (using RR0 variables), 8.10 kpc (using one RR1 variable), and 8.35 ± 0.42 kpc (using our SX Phoenicis star detection in M 30...

  17. Giant CP stars

    International Nuclear Information System (INIS)

    Loden, L.O.; Sundman, A.

    1989-01-01

    This study is part of an investigation of the possibility of using chemically peculiar (CP) stars to map local galactic structure. Correct luminosities of these stars are therefore crucial. CP stars are generally regarded as main-sequence or near-main-sequence objects. However, some CP stars have been classified as giants. A selection of stars, classified in literature as CP giants, are compared to normal stars in the same effective temperature interval and to ordinary 'non giant' CP stars. There is no clear confirmation of a higher luminosity for 'CP giants', than for CP stars in general. In addition, CP characteristics seem to be individual properties not repeated in a component star or other cluster members. (author). 50 refs., 5 tabs., 3 figs

  18. Bursting star formation and the overabundance of Wolf-Rayet stars

    International Nuclear Information System (INIS)

    Bodigfee, G.; Deloore, C.

    1985-01-01

    The ratio of the number of WR-stars to their OB progenitors appears to be significantly higher in some extragalactic systems than in our Galaxy. This overabundance of Wolf-Rayet-stars can be explained as a consequence of a recent burst of star formation. It is suggested that this burst is the manifestation of a long period nonlinear oscillation in the star formation process, produced by positive feedback effects between young stars and the interstellar medium. Star burst galaxies with large numbers of WR-stars must generate gamma fluxes but due to the distance, all of them are beyond the reach of present-day detectors, except probably 30 Dor

  19. Similar uptake profiles of microcystin-LR and -RR in an in vitro human intestinal model

    International Nuclear Information System (INIS)

    Zeller, P.; Clement, M.; Fessard, V.

    2011-01-01

    Highlights: → First description of in vitro cellular uptake of MCs into intestinal cells. → OATP 3A1 and OATP 4A1 are expressed in Caco-2 cell membranes. → MC-LR and MC-RR show similar uptake in Caco-2 cells. → MCs are probably excreted from Caco-2 cells by an active mechanism. -- Abstract: Microcystins (MCs) are cyclic hepatotoxins produced by various species of cyanobacteria. Their structure includes two variable amino acids (AA) leading to more than 80 MC variants. In this study, we focused on the most common variant, microcystin-LR (MC-LR), and microcystin-RR (MC-RR), a variant differing by only one AA. Despite their structural similarity, MC-LR elicits higher liver toxicity than MC-RR partly due to a discrepancy in their uptake by hepatic organic anion transporters (OATP 1B1 and 1B3). However, even though ingestion is the major pathway of human exposure to MCs, intestinal absorption of MCs has been poorly addressed. Consequently, we investigated the cellular uptake of the two MC variants in the human intestinal cell line Caco-2 by immunolocalization using an anti-MC antibody. Caco-2 cells were treated for 30 min to 24 h with several concentrations (1-50 μM) of both variants. We first confirmed the localization of OATP 3A1 and 4A1 at the cell membrane of Caco-2 cells. Our study also revealed a rapid uptake of both variants in less than 1 h. The uptake profiles of the two variants did not differ in our immunostaining study neither with respect to concentration nor the time of exposure. Furthermore, we have demonstrated for the first time the nuclear localization of MC-RR and confirmed that of MC-LR. Finally, our results suggest a facilitated uptake and an active excretion of MC-LR and MC-RR in Caco-2 cells. Further investigation on the role of OATP 3A1 and 4A1 in MC uptake should be useful to clarify the mechanism of intestinal absorption of MCs and contribute in risk assessment of cyanotoxin exposure.

  20. TRIGGERED STAR FORMATION SURROUNDING WOLF-RAYET STAR HD 211853

    Energy Technology Data Exchange (ETDEWEB)

    Liu Tie; Wu Yuefang; Zhang Huawei [Department of Astronomy, Peking University, 100871 Beijing (China); Qin Shengli, E-mail: liutiepku@gmail.com [I. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Str. 77, 50937 Koeln (Germany)

    2012-05-20

    The environment surrounding Wolf-Rayet (W-R) star HD 211853 is studied in molecular, infrared, as well as radio, and H I emission. The molecular ring consists of well-separated cores, which have a volume density of 10{sup 3} cm{sup -3} and kinematic temperature {approx}20 K. Most of the cores are under gravitational collapse due to external pressure from the surrounding ionized gas. From the spectral energy distribution modeling toward the young stellar objects, the sequential star formation is revealed on a large scale in space spreading from the W-R star to the molecular ring. A small-scale sequential star formation is revealed toward core 'A', which harbors a very young star cluster. Triggered star formations are thus suggested. The presence of the photodissociation region, the fragmentation of the molecular ring, the collapse of the cores, and the large-scale sequential star formation indicate that the 'collect and collapse' process functions in this region. The star-forming activities in core 'A' seem to be affected by the 'radiation-driven implosion' process.

  1. TRIGGERED STAR FORMATION SURROUNDING WOLF-RAYET STAR HD 211853

    International Nuclear Information System (INIS)

    Liu Tie; Wu Yuefang; Zhang Huawei; Qin Shengli

    2012-01-01

    The environment surrounding Wolf-Rayet (W-R) star HD 211853 is studied in molecular, infrared, as well as radio, and H I emission. The molecular ring consists of well-separated cores, which have a volume density of 10 3 cm –3 and kinematic temperature ∼20 K. Most of the cores are under gravitational collapse due to external pressure from the surrounding ionized gas. From the spectral energy distribution modeling toward the young stellar objects, the sequential star formation is revealed on a large scale in space spreading from the W-R star to the molecular ring. A small-scale sequential star formation is revealed toward core 'A', which harbors a very young star cluster. Triggered star formations are thus suggested. The presence of the photodissociation region, the fragmentation of the molecular ring, the collapse of the cores, and the large-scale sequential star formation indicate that the 'collect and collapse' process functions in this region. The star-forming activities in core 'A' seem to be affected by the 'radiation-driven implosion' process.

  2. 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.

  3. Wolf-Rayet stars

    Energy Technology Data Exchange (ETDEWEB)

    Sahade, J

    1981-12-01

    Aspects of the problems of the Wolf-Rayet stars related to their chemical composition, their evolutionary status, and their apparent dichotomy in two spectral sequences are discussed. Dogmas concerning WR stars are critically discussed, including the belief that WR stars lack hydrogen, that they are helium stars evolved from massive close binaries, and the existence of a second WR stage in which the star is a short-period single-lined binary. The relationship of WR stars with planetary nebulae is addressed, as is the membership of these stars in clusters and associations. The division of WR stars into WN and WC sequences is considered, questioning the reasonability of accounting for WR line formation in terms of abundance differences.

  4. StarDOM: From STAR format to XML

    International Nuclear Information System (INIS)

    Linge, Jens P.; Nilges, Michael; Ehrlich, Lutz

    1999-01-01

    StarDOM is a software package for the representation of STAR files as document object models and the conversion of STAR files into XML. This allows interactive navigation by using the Document Object Model representation of the data as well as easy access by XML query languages. As an example application, the entire BioMagResBank has been transformed into XML format. Using an XML query language, statistical queries on the collected NMR data sets can be constructed with very little effort. The BioMagResBank/XML data and the software can be obtained at http://www.nmr.embl-heidelberg.de/nmr/StarDOM/

  5. STARS no star on Kauai

    International Nuclear Information System (INIS)

    Jones, M.

    1993-01-01

    The island of Kuai, home to the Pacific Missile Range Facility, is preparing for the first of a series of Star Wars rocket launches expected to begin early this year. The Strategic Defense Initiative plans 40 launches of the Stategic Target System (STARS) over a 10-year period. The focus of the tests appears to be weapons and sensors designed to combat multiple-warhead ICBMs, which will be banned under the START II Treaty that was signed in January. The focus of this article is to express the dubious value of testing the STARS at a time when their application will not be an anticipated problem

  6. 76 FR 65136 - Airworthiness Directives; Rolls-Royce plc (RR) Turbofan Engines

    Science.gov (United States)

    2011-10-20

    ... Airworthiness Directives; Rolls-Royce plc (RR) Turbofan Engines AGENCY: Federal Aviation Administration (FAA... information identified in this AD, contact Rolls-Royce plc, Corporate Communications, P.O. Box 31, Derby... 8, 2011, to perform the inspection. Costs of Compliance Based on the service information, we...

  7. VizieR Online Data Catalog: Type II Cepheid and RR Lyrae variables (Feast+, 2008)

    Science.gov (United States)

    Feast, M. W.; Laney, C. D.; Kinman, T. D.; van Leeuwen, F.; Whitelock, P. A.

    2008-10-01

    Infrared and optical absolute magnitudes are derived for the type II Cepheids kappa Pav and VY Pyx using revised Hipparcos parallaxes and for kappa Pav, V553 Cen and SW Tau from pulsational parallaxes. Revised Hipparcos and HST parallaxes for RR Lyrae agree satisfactorily and are combined in deriving absolute magnitudes. Phase-corrected J, H and Ks mags are given for 142 Hipparcos RR Lyraes based on Two-Micron All-Sky Survey observations. Pulsation and trigonometrical parallaxes for classical Cepheids are compared to establish the best value for the projection factor (p) used in pulsational analyses. (3 data files).

  8. Research on the Solid State Fermentation of Jerusalem Artichoke Pomace for Producing R,R-2,3-Butanediol by Paenibacillus polymyxa ZJ-9.

    Science.gov (United States)

    Cao, Can; Zhang, Li; Gao, Jian; Xu, Hong; Xue, Feng; Huang, Weiwei; Li, Yan

    2017-06-01

    R,R-2,3-butanediol (R,R-2,3-BD) was produced by Paenibacillus polymyxa ZJ-9, which was capable of utilizing inulin without previous hydrolysis. The Jerusalem artichoke pomace (JAP) derived from the conversion of Jerusalem artichoke powder into inulin extract, which was usually used for biorefinery by submerged fermentation (SMF), was utilized in solid state fermentation (SSF) to produce R,R-2,3-BD. In this study, the fermentation parameters of SSF were optimized and determined in flasks. A novel bioreactor was designed and assembled for the laboratory scale-up of SSF, with a maximum yield of R,R-2,3-BD (67.90 g/kg (JAP)). This result is a 36.3% improvement compared with the flasks. Based on the same bath of Jerusalem artichoke powder, the total output of R,R-2,3-BD increased by 38.8% for the SSF of JAP combined with the SMF of inulin extraction. Overall, the utilization of JAP for R,R-2,3-BD production was beneficial to the comprehensive utilization of Jerusalem artichoke tuber.

  9. 78 FR 54149 - Airworthiness Directives; Rolls-Royce plc (RR) Turbofan Engines

    Science.gov (United States)

    2013-09-03

    ... Airworthiness Directives; Rolls-Royce plc (RR) Turbofan Engines AGENCY: Federal Aviation Administration (FAA... service information identified in this AD, contact Rolls-Royce plc, Corporate Communications, P.O. Box 31... per hour. Replacement parts are estimated to cost about $2,271 per engine. Based on these figures, we...

  10. Star-forming galaxy models: Blending star formation into TREESPH

    Science.gov (United States)

    Mihos, J. Christopher; Hernquist, Lars

    1994-01-01

    We have incorporated star-formation algorithms into a hybrid N-body/smoothed particle hydrodynamics code (TREESPH) in order to describe the star forming properties of disk galaxies over timescales of a few billion years. The models employ a Schmidt law of index n approximately 1.5 to calculate star-formation rates, and explicitly include the energy and metallicity feedback into the Interstellar Medium (ISM). Modeling the newly formed stellar population is achieved through the use of hybrid SPH/young star particles which gradually convert from gaseous to collisionless particles, avoiding the computational difficulties involved in creating new particles. The models are shown to reproduce well the star-forming properties of disk galaxies, such as the morphology, rate of star formation, and evolution of the global star-formation rate and disk gas content. As an example of the technique, we model an encounter between a disk galaxy and a small companion which gives rise to a ring galaxy reminiscent of the Cartwheel (AM 0035-35). The primary galaxy in this encounter experiences two phases of star forming activity: an initial period during the expansion of the ring, and a delayed phase as shocked material in the ring falls back into the central regions.

  11. EMACSS: Evolve Me A Cluster of StarS

    Science.gov (United States)

    Alexander, Poul E. R.; Gieles, Mark

    2012-03-01

    The star cluster evolution code Evolve Me A Cluster of StarS (EMACSS) is a simple yet physically motivated computational model that describes the evolution of some fundamental properties of star clusters in static tidal fields. The prescription is based upon the flow of energy within the cluster, which is a constant fraction of the total energy per half-mass relaxation time. According to Henon's predictions, this flow is independent of the precise mechanisms for energy production within the core, and therefore does not require a complete description of the many-body interactions therein. Dynamical theory and analytic descriptions of escape mechanisms is used to construct a series of coupled differential equations expressing the time evolution of cluster mass and radius for a cluster of equal-mass stars. These equations are numerically solved using a fourth-order Runge-Kutta integration kernel; the results were benchmarked against a data base of direct N-body simulations. EMACSS is publicly available and reproduces the N-body results to within 10 per cent accuracy for the entire post-collapse evolution of star clusters.

  12. The crystal structure of the AhRR-ARNT heterodimer reveals the structural basis of the repression of AhR-mediated transcription.

    Science.gov (United States)

    Sakurai, Shunya; Shimizu, Toshiyuki; Ohto, Umeharu

    2017-10-27

    2,3,7,8-Tetrachlorodibenzo- p -dioxin and related compounds are extraordinarily potent environmental toxic pollutants. Most of the 2,3,7,8-tetrachlorodibenzo- p -dioxin toxicities are mediated by aryl hydrocarbon receptor (AhR), a ligand-dependent transcription factor belonging to the basic helix-loop-helix (bHLH) Per-ARNT-Sim (PAS) family. Upon ligand binding, AhR forms a heterodimer with AhR nuclear translocator (ARNT) and induces the expression of genes involved in various biological responses. One of the genes induced by AhR encodes AhR repressor (AhRR), which also forms a heterodimer with ARNT and represses the activation of AhR-dependent transcription. The control of AhR activation is critical for managing AhR-mediated diseases, but the mechanisms by which AhRR represses AhR activation remain poorly understood, because of the lack of structural information. Here, we determined the structure of the AhRR-ARNT heterodimer by X-ray crystallography, which revealed an asymmetric intertwined domain organization presenting structural features that are both conserved and distinct among bHLH-PAS family members. The structures of AhRR-ARNT and AhR-ARNT were similar in the bHLH-PAS-A region, whereas the PAS-B of ARNT in the AhRR-ARNT complex exhibited a different domain arrangement in this family reported so far. The structure clearly disclosed that AhRR competitively represses AhR binding to ARNT and target DNA and further suggested the existence of an AhRR-ARNT-specific repression mechanism. This study provides a structural basis for understanding the mechanism by which AhRR represses AhR-mediated gene transcription. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  13. Those Crafty Cepheids: Surprises From Ground-Based Photometry and HST-COS FUV Spectra

    Science.gov (United States)

    Engle, Scott G.; Guinan, E. F.; Neilson, H.; Wasatonic, R. P.; Harper, G.

    2013-06-01

    Several years ago the Secret Lives of Cepheids (SLiC) program was initiated to look for unexpected or exotic behaviors from Cepheids. Regular photometric monitoring of Cepheids already possessing robust historical datasets was started to better understand long-term pulsation period changes, but to look for possible amplitude changes as well. At the time, only two “unusual” Cepheids were known to have undergone amplitude changes - Polaris and V473 Lyr. To date, however, the SLiC program has found evidence for amplitude changes in seven other Cepheids, raising the possibility that a "Blazhko effect" could be at work in certain Cepheids, as exists in a subset of RR Lyr stars. As the program expanded, we found that previous International Ultraviolet Exporer (IUE) studies showed certain Cepheids to have UV emissions from warm-to-hot stellar atmospheres. On top of that, the emissions were variable and well-phased to the stellar pulsation period, indicating that the mechanism heating the Cepheid atmosphere was influenced by these pulsations, if not linked to them. With the installation of the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope (HST), a modern, high-quality UV spectrograph was now operating that could efficiently obtain high-resolution spectra of the Cepheids. We have been fortunate to observe four Cepheids to date with COS, and the results are well beyond anything IUE had led us to expect. Here we will present the current optical and UV results of the SLiC program, the implications of the results, and the future direction and expansion of the program. We gratefully acknowledge support for this program from HST grants HST-GO-11726.01-A, HST-GO-12302.01-A and HST-GO-13019.01-A, as well as NSF/RUI grant AST-1009903.

  14. Comparative Studies on the pH Dependence of DOW of Microcystin-RR and -LR Using LC-MS

    Directory of Open Access Journals (Sweden)

    Gaodao Liang

    2011-01-01

    Full Text Available Microcystins (MCs are well known worldwide as hepatotoxins produced by cyanobacteria, but little is known about the physicochemical properties of these compounds. The dependence of the n-octanol/water distribution ratio (DOW of MC-RR and -LR to pH was measured by high-performance liquid chromatography combined with mass spectrometry (LC-MS. There was a remarkable difference in such relationships between MC-RR and -LR. The log DOW of MC-LR decreased from 1.63 at pH 1.0 to -1.26 at pH 6.5, and stabilized between -1.04 and -1.56 at a pH of 6.5~12.0; log DOW of MC-RR varied between -1.24 and -0.67 at a pH of 1.00~4.00, and stabilized between -1.20 and -1.54 at a pH of 4.00~12.00. The difference of hydrophobicity in acidic condition between MC-RR and -LR is important, not only for the analytical method of both toxins, but perhaps also for understanding the difference of toxicity to animals between the two toxins.

  15. Barium and Tc-poor S stars: Binary masqueraders among carbon stars

    OpenAIRE

    Jorissen, A.; Van Eck, S.

    1997-01-01

    The current understanding of the origin of barium and S stars is reviewed, based on new orbital elements and binary frequencies. The following questions are addressed: (i) Is binarity a necessary condition to produce a barium star? (ii) What is the mass transfer mode (wind accretion or RLOF?) responsible for their formation? (iii) Do barium stars form as dwarfs or as giants? (iv) Do barium stars evolve into Tc-poor S stars? (v) What is the relative frequency of Tc-rich and Tc-poor S stars?

  16. Radio stars

    International Nuclear Information System (INIS)

    Hjellming, R.M.

    1976-01-01

    Any discussion of the radio emission from stars should begin by emphasizing certain unique problems. First of all, one must clarify a semantic confusion introduced into radio astronomy in the late 1950's when most new radio sources were described as radio stars. All of these early 'radio stars' were eventually identified with other galactic and extra-galactic objects. The study of true radio stars, where the radio emission is produced in the atmosphere of a star, began only in the 1960's. Most of the work on the subject has, in fact, been carried out in only the last few years. Because the real information about radio stars is quite new, it is not surprising that major aspects of the subject are not at all understood. For this reason this paper is organized mainly around three questions: what is the available observational information; what physical processes seem to be involved; and what working hypotheses look potentially fruitful. (Auth.)

  17. TURBOVELOCITY STARS: KICKS RESULTING FROM THE TIDAL DISRUPTION OF SOLITARY STARS

    International Nuclear Information System (INIS)

    Manukian, Haik; Guillochon, James; Ramirez-Ruiz, Enrico; O'Leary, Ryan M.

    2013-01-01

    The centers of most known galaxies host supermassive black holes (SMBHs). In orbit around these black holes are a centrally concentrated distribution of stars, both in single and in binary systems. Occasionally, these stars are perturbed onto orbits that bring them close to the SMBH. If the star is in a binary system, the three-body interaction with the SMBH can lead to large changes in orbital energy, depositing one of the two stars on a tightly-bound orbit, and its companion into a hyperbolic orbit that may escape the galaxy. In this Letter, we show that the disruption of solitary stars can also lead to large positive increases in orbital energy. The kick velocity depends on the amount of mass the star loses at pericenter, but not on the ratio of black hole to stellar mass, and are at most the star's own escape velocity. We find that these kicks are usually too small to result in the ejection of stars from the Milky Way, but can eject the stars from the black hole's sphere of influence, reducing their probability of being disrupted again. We estimate that ∼ 10 5 stars, ∼ 1% of all stars within 10 pc of the galactic center, are likely to have had mass removed by the central black hole through tidal interaction, and speculate that these 'turbovelocity' stars will at first be redder, but eventually bluer, and always brighter than their unharassed peers.

  18. New Variable Stars Discovered by Data Mining Images Taken during Recent Asteroid Photometric Observations. II. Results from July 2015 through December 2016

    Science.gov (United States)

    Papini, R.; Marchini, A.; Salvaggio, F.; Agnetti, D.; Bacci, P.; Banfi, M.; Bianciardi, G.; Collina, M.; Franco, L.; Galli, G.; Milani, M. G. A.; Lopresti, C.; Marino, G.; Rizzuti, L.; Ruocco, N.; Quadri, U.

    2017-12-01

    This paper follows the previous publication of new variables discovered at Astronomical Observatory, DSFTA, University of Siena, while observing asteroids in order to determine their rotational periods. Usually, this task requires time series images acquisition on a single field for as long as possible on a few nights not necessarily consecutive. Checking continually this "goldmine" allowed us to discover 57 variable stars not yet listed in catalogues or databases. While most of the new variables are eclipsing binaries, a few belong to the RR Lyrae or delta Scuti class. Since asteroid work is definitely a time-consuming activity, coordinated campaigns of follow-up with other observatories have been fundamental in order to determine the elements of the ephemeris and sometimes the right subclass of variability. Further observations of these new variables are therefore strongly encouraged in order to better characterize these stars, especially pulsating ones whose data combined with those taken during professional surveys seem to suggest the presence of light curve amplitude and period variations.

  19. Radio stars

    International Nuclear Information System (INIS)

    Hjellming, R.M.; Gibson, D.M.

    1985-01-01

    Studies of stellar radio emission became an important field of research in the 1970's and have now expanded to become a major area of radio astronomy with the advent of new instruments such as the Very Large Array in New Mexico and transcontinental telescope arrays. This volume contains papers from the workshop on stellar continuum radio astronomy held in Boulder, Colorado, and is the first book on the rapidly expanding field of radio emission from stars and stellar systems. Subjects covered include the observational and theoretical aspects of stellar winds from both hot and cool stars, radio flares from active double star systems and red dwarf stars, bipolar flows from star-forming regions, and the radio emission from X-ray binaries. (orig.)

  20. A hybrid method for accurate star tracking using star sensor and gyros.

    Science.gov (United States)

    Lu, Jiazhen; Yang, Lie; Zhang, Hao

    2017-10-01

    Star tracking is the primary operating mode of star sensors. To improve tracking accuracy and efficiency, a hybrid method using a star sensor and gyroscopes is proposed in this study. In this method, the dynamic conditions of an aircraft are determined first by the estimated angular acceleration. Under low dynamic conditions, the star sensor is used to measure the star vector and the vector difference method is adopted to estimate the current angular velocity. Under high dynamic conditions, the angular velocity is obtained by the calibrated gyros. The star position is predicted based on the estimated angular velocity and calibrated gyros using the star vector measurements. The results of the semi-physical experiment show that this hybrid method is accurate and feasible. In contrast with the star vector difference and gyro-assisted methods, the star position prediction result of the hybrid method is verified to be more accurate in two different cases under the given random noise of the star centroid.

  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. Effective star tracking method based on optical flow analysis for star trackers.

    Science.gov (United States)

    Sun, Ting; Xing, Fei; Wang, Xiaochu; Li, Jin; Wei, Minsong; You, Zheng

    2016-12-20

    Benefiting from rapid development of imaging sensor technology, modern optical technology, and a high-speed computing chip, the star tracker's accuracy, dynamic performance, and update rate have been greatly improved with low power consumption and miniature size. The star tracker is currently one of the most competitive attitude measurement sensors. However, due to restrictions of the optical imaging system, difficulties still exist in moving star spot detection and star tracking when in special motion conditions. An effective star tracking method based on optical flow analysis for star trackers is proposed in this paper. Spot-based optical flow, based on a gray gradient between two adjacent star images, is analyzed to distinguish the star spot region and obtain an accurate star spot position so that the star tracking can keep continuous under high dynamic conditions. The obtained star vectors and extended Kalman filter (EKF) are then combined to conduct an angular velocity estimation to ensure region prediction of the star spot; this can be combined with the optical flow analysis result. Experiment results show that the method proposed in this paper has advantages in conditions of large angular velocity and large angular acceleration, despite the presence of noise. Higher functional density and better performance can be achieved; thus, the star tracker can be more widely applied in small satellites, remote sensing, and other complex space missions.

  3. On the building blocks of the M31 and Milky Way halos

    Directory of Open Access Journals (Sweden)

    Monelli Matteo

    2017-01-01

    Full Text Available We discuss the formation of the halo of M31 and the Milky Way as traced by the population of RR Lyrae stars, in comparison with the population of such stars preent in satellite dwarf galaxies. We find that both halos and the massive dwarf host a population of high amplitude short period RRab stars, absent in low-mass dwarfs. These stars are explained as the metal-rich tail of the RR Lyrae distribution ([Fe/H] ∼ - 1.5, and thus their existence imply fast chemical enrichment in the host system. Their presence in both halos implies that massive building blocks had an important role in their formation.

  4. Thermal performance of Egypt's research reactor core (ET-RR-1)

    International Nuclear Information System (INIS)

    Khattab, M.; Mariy, A.

    1986-01-01

    The steady state thermal performance of the ET-RR-1 core system is theoretically investigated by different models describing the heat flux and the coolant mass flow rate. The magnitude of the heat generated by a fuel element depends upon its position in the core. Normal and uniform distributions for heat flux and coolant mass flow rate are considered. The clad and coolant temperatures at different core positions are evaluated and compared with the experimental measurements at different operating conditions. The results indicated large discrepancy between the predicted and the experimental results. Therefore, the previous models and the experimental results are evaluated in order to develop the best model that describes the thermal performance of the ET-RR-1 core. The adapted model gives 99.5% significant confidence limit. The effect of increasing the heat flux or decreasing the mass flow rate by 20% from its maximum recommended operating condition is tested and discussed. Also, the thermal behaviour towards increasing the reactor power more than its maximum operating condition is discussed. The present work could also be used in extending the investigation to other PWR reactor operating conditions

  5. Formation of stars and star clusters in colliding galaxies

    International Nuclear Information System (INIS)

    Belles, Pierre-Emmanuel

    2012-01-01

    Mergers are known to be essential in the formation of large-scale structures and to have a significant role in the history of galaxy formation and evolution. Besides a morphological transformation, mergers induce important bursts of star formation. These starburst are characterised by high Star Formation Efficiencies (SFEs) and Specific Star Formation Rates, i.e., high Star Formation Rates (SFR) per unit of gas mass and high SFR per unit of stellar mass, respectively, compared to spiral galaxies. At all redshifts, starburst galaxies are outliers of the sequence of star-forming galaxies defined by spiral galaxies. We have investigated the origin of the starburst-mode of star formation, in three local interacting systems: Arp 245, Arp 105 and NGC 7252. We combined high-resolution JVLA observations of the 21-cm line, tracing the HI diffuse gas, with UV GALEX observations, tracing the young star-forming regions. We probe the local physical conditions of the Inter-Stellar Medium (ISM) for independent star-forming regions and explore the atomic-to-dense gas transformation in different environments. The SFR/HI ratio is found to be much higher in central regions, compared to outer regions, showing a higher dense gas fraction (or lower HI gas fraction) in these regions. In the outer regions of the systems, i.e., the tidal tails, where the gas phase is mostly atomic, we find SFR/HI ratios higher than in standard HI-dominated environments, i.e., outer discs of spiral galaxies and dwarf galaxies. Thus, our analysis reveals that the outer regions of mergers are characterised by high SFEs, compared to the standard mode of star formation. The observation of high dense gas fractions in interacting systems is consistent with the predictions of numerical simulations; it results from the increase of the gas turbulence during a merger. The merger is likely to affect the star-forming properties of the system at all spatial scales, from large scales, with a globally enhanced turbulence

  6. Stars Just Got Bigger - A 300 Solar Mass Star Uncovered

    Science.gov (United States)

    2010-07-01

    Using a combination of instruments on ESO's Very Large Telescope, astronomers have discovered the most massive stars to date, one weighing at birth more than 300 times the mass of the Sun, or twice as much as the currently accepted limit of 150 solar masses. The existence of these monsters - millions of times more luminous than the Sun, losing weight through very powerful winds - may provide an answer to the question "how massive can stars be?" A team of astronomers led by Paul Crowther, Professor of Astrophysics at the University of Sheffield, has used ESO's Very Large Telescope (VLT), as well as archival data from the NASA/ESA Hubble Space Telescope, to study two young clusters of stars, NGC 3603 and RMC 136a in detail. NGC 3603 is a cosmic factory where stars form frantically from the nebula's extended clouds of gas and dust, located 22 000 light-years away from the Sun (eso1005). RMC 136a (more often known as R136) is another cluster of young, massive and hot stars, which is located inside the Tarantula Nebula, in one of our neighbouring galaxies, the Large Magellanic Cloud, 165 000 light-years away (eso0613). The team found several stars with surface temperatures over 40 000 degrees, more than seven times hotter than our Sun, and a few tens of times larger and several million times brighter. Comparisons with models imply that several of these stars were born with masses in excess of 150 solar masses. The star R136a1, found in the R136 cluster, is the most massive star ever found, with a current mass of about 265 solar masses and with a birthweight of as much as 320 times that of the Sun. In NGC 3603, the astronomers could also directly measure the masses of two stars that belong to a double star system [1], as a validation of the models used. The stars A1, B and C in this cluster have estimated masses at birth above or close to 150 solar masses. Very massive stars produce very powerful outflows. "Unlike humans, these stars are born heavy and lose weight as

  7. The Destructive Birth of Massive Stars and Massive Star Clusters

    Science.gov (United States)

    Rosen, Anna; Krumholz, Mark; McKee, Christopher F.; Klein, Richard I.; Ramirez-Ruiz, Enrico

    2017-01-01

    Massive stars play an essential role in the Universe. They are rare, yet the energy and momentum they inject into the interstellar medium with their intense radiation fields dwarfs the contribution by their vastly more numerous low-mass cousins. Previous theoretical and observational studies have concluded that the feedback associated with massive stars' radiation fields is the dominant mechanism regulating massive star and massive star cluster (MSC) formation. Therefore detailed simulation of the formation of massive stars and MSCs, which host hundreds to thousands of massive stars, requires an accurate treatment of radiation. For this purpose, we have developed a new, highly accurate hybrid radiation algorithm that properly treats the absorption of the direct radiation field from stars and the re-emission and processing by interstellar dust. We use our new tool to perform a suite of three-dimensional radiation-hydrodynamic simulations of the formation of massive stars and MSCs. For individual massive stellar systems, we simulate the collapse of massive pre-stellar cores with laminar and turbulent initial conditions and properly resolve regions where we expect instabilities to grow. We find that mass is channeled to the massive stellar system via gravitational and Rayleigh-Taylor (RT) instabilities. For laminar initial conditions, proper treatment of the direct radiation field produces later onset of RT instability, but does not suppress it entirely provided the edges of the radiation-dominated bubbles are adequately resolved. RT instabilities arise immediately for turbulent pre-stellar cores because the initial turbulence seeds the instabilities. To model MSC formation, we simulate the collapse of a dense, turbulent, magnetized Mcl = 106 M⊙ molecular cloud. We find that the influence of the magnetic pressure and radiative feedback slows down star formation. Furthermore, we find that star formation is suppressed along dense filaments where the magnetic field is

  8. First stars X. The nature of three unevolved carbon-enhanced metal-poor stars

    DEFF Research Database (Denmark)

    Sivarani, T.; Beers, T.C.; Bonifacio, P.

    2006-01-01

    Stars: abundances, stars: population II, Galaxy: abundances, stars: AGB and post-AGB Udgivelsesdato: Nov.......Stars: abundances, stars: population II, Galaxy: abundances, stars: AGB and post-AGB Udgivelsesdato: Nov....

  9. STELLAR ARCHEOLOGY IN THE GALACTIC HALO WITH ULTRA-FAINT DWARFS. VII. HERCULES

    Energy Technology Data Exchange (ETDEWEB)

    Musella, Ilaria; Ripepi, Vincenzo; Marconi, Marcella, E-mail: ilaria@na.astro.it, E-mail: ripepi@na.astro.it, E-mail: marcella@na.astro.it [INAF, Osservatorio Astronomico di Capodimonte, I-8013 Napoli (Italy); and others

    2012-09-10

    We present the first time-series study of the ultra-faint dwarf galaxy Hercules. Using a variety of telescope/instrument facilities we secured about 50 V and 80 B epochs. These data allowed us to detect and characterize 10 pulsating variable stars in Hercules. Our final sample includes six fundamental-mode (ab-type) and three first-overtone (c-type) RR Lyrae stars, and one Anomalous Cepheid. The average period of the ab-type RR Lyrae stars, (P{sub ab}) = 0.68 days ({sigma} = 0.03 days), places Hercules in the Oosterhoff II group, as found for almost the totality of the ultra-faint dwarf galaxies investigated so far for variability. The RR Lyrae stars were used to obtain independent estimates of the metallicity, reddening, and distance to Hercules, for which we find [Fe/H] = -2.30 {+-} 0.15 dex, E(B - V) = 0.09 {+-} 0.02 mag, and (m - M){sub 0} = 20.6 {+-} 0.1 mag, in good agreement with the literature values. We have obtained a V, B - V color-magnitude diagram (CMD) of Hercules that reaches V {approx} 25 mag and extends beyond the galaxy's half-light radius over a total area of 40' Multiplication-Sign 36'. The CMD and the RR Lyrae stars indicate the presence of a population as old and metal-poor as (at least) the Galactic globular cluster M68.

  10. A Look at the Milky Way's Outskirts

    Science.gov (United States)

    Kohler, Susanna

    2017-11-01

    Studying the large-scale structure of the Milky Way is difficult given that were stuck in its interior which means we cant step back for a broad overview of our home. Instead, a recent study uses distant variable stars to map out a picture of whats happening in the outskirts of our galaxy.Mapping with TracersPhase-folded light curve for two of the RR Lyrae stars in the authors sample, each with hundreds of observations over 7 years. [Cohen et al. 2017]Since observing the Milky Way from the outside isnt an option, we have to take creative approaches to mapping its outer regions and measuring its total mass and dark matter content. One tool used by astronomers is tracers: easily identifiable stars that can be treated as massless markers moving only as a result of the galactic potential. Mapping the locations and motions of tracers allows us to measure the larger properties of the galaxy.RR Lyrae stars are low-mass, variable stars that make especially good tracers. They pulsate predictably on timescales of less than a day, creating distinctive light curves that can easily be distinguished and tracked in wide-field optical imaging surveys over long periods of time. Their brightness makes them detectable out to large distances, and their blue color helps to separate them from contaminating stars in the foreground.Best of all, RR Lyrae stars are very nearly standard candles: their distances can be determined precisely with only knowledge of their measured light curves.Locations on the sky of the several hundred outer-halo RR Lyrae stars in the authors original sample. The red curve shows the location of the Sagittarius stream, an ordered structure the authors avoided so as to only have unassociated stars in their sample. [Cohen et al. 2017]Distant VariablesIn a new study led by Judith Cohen (California Institute of Technology), the signals of hundreds of distant RR Lyrae stars were identified in observations of transient objects made with the Palomar Transient Factory

  11. False star detection and isolation during star tracking based on improved chi-square tests.

    Science.gov (United States)

    Zhang, Hao; Niu, Yanxiong; Lu, Jiazhen; Yang, Yanqiang; Su, Guohua

    2017-08-01

    The star sensor is a precise attitude measurement device for a spacecraft. Star tracking is the main and key working mode for a star sensor. However, during star tracking, false stars become an inevitable interference for star sensor applications, which may result in declined measurement accuracy. A false star detection and isolation algorithm in star tracking based on improved chi-square tests is proposed in this paper. Two estimations are established based on a Kalman filter and a priori information, respectively. The false star detection is operated through adopting the global state chi-square test in a Kalman filter. The false star isolation is achieved using a local state chi-square test. Semi-physical experiments under different trajectories with various false stars are designed for verification. Experiment results show that various false stars can be detected and isolated from navigation stars during star tracking, and the attitude measurement accuracy is hardly influenced by false stars. The proposed algorithm is proved to have an excellent performance in terms of speed, stability, and robustness.

  12. Entropy Analysis of RR and QT Interval Variability during Orthostatic and Mental Stress in Healthy Subjects

    Directory of Open Access Journals (Sweden)

    Mathias Baumert

    2014-12-01

    Full Text Available Autonomic activity affects beat-to-beat variability of heart rate and QT interval. The aim of this study was to explore whether entropy measures are suitable to detect changes in neural outflow to the heart elicited by two different stress paradigms. We recorded short-term ECG in 11 normal subjects during an experimental protocol that involved head-up tilt and mental arithmetic stress and computed sample entropy, cross-sample entropy and causal interactions based on conditional entropy from RR and QT interval time series. Head-up tilt resulted in a significant reduction in sample entropy of RR intervals and cross-sample entropy, while mental arithmetic stress resulted in a significant reduction in coupling directed from RR to QT. In conclusion, measures of entropy are suitable to detect changes in neural outflow to the heart and decoupling of repolarisation variability from heart rate variability elicited by orthostatic or mental arithmetic stress.

  13. White Dwarf Stars

    OpenAIRE

    Kepler, S. O.; Romero, Alejandra Daniela; Pelisoli, Ingrid; Ourique, Gustavo

    2017-01-01

    White dwarf stars are the final stage of most stars, born single or in multiple systems. We discuss the identification, magnetic fields, and mass distribution for white dwarfs detected from spectra obtained by the Sloan Digital Sky Survey up to Data Release 13 in 2016, which lead to the increase in the number of spectroscopically identified white dwarf stars from 5000 to 39000. This number includes only white dwarf stars with log g >= 6.5 stars, i.e., excluding the Extremely Low Mass white dw...

  14. THE PREVALENCE AND IMPACT OF WOLF–RAYET STARS IN EMERGING MASSIVE STAR CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Sokal, Kimberly R.; Johnson, Kelsey E.; Indebetouw, Rémy [Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903 (United States); Massey, Philip, E-mail: krs9tb@virginia.edu [Lowell Observatory, 1400 W Mars Hill Road, Flagstaff, AZ 86001 (United States)

    2016-08-01

    We investigate Wolf–Rayet (WR) stars as a source of feedback contributing to the removal of natal material in the early evolution of massive star clusters. Despite previous work suggesting that massive star clusters clear out their natal material before the massive stars evolve into the WR phase, WR stars have been detected in several emerging massive star clusters. These detections suggest that the timescale for clusters to emerge can be at least as long as the time required to produce WR stars (a few million years), and could also indicate that WR stars may be providing the tipping point in the combined feedback processes that drive a massive star cluster to emerge. We explore the potential overlap between the emerging phase and the WR phase with an observational survey to search for WR stars in emerging massive star clusters hosting WR stars. We select candidate emerging massive star clusters from known radio continuum sources with thermal emission and obtain optical spectra with the 4 m Mayall Telescope at Kitt Peak National Observatory and the 6.5 m MMT.{sup 4} We identify 21 sources with significantly detected WR signatures, which we term “emerging WR clusters.” WR features are detected in ∼50% of the radio-selected sample, and thus we find that WR stars are commonly present in currently emerging massive star clusters. The observed extinctions and ages suggest that clusters without WR detections remain embedded for longer periods of time, and may indicate that WR stars can aid, and therefore accelerate, the emergence process.

  15. 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.

  16. R-R interval variations influence the degree of mitral regurgitation in dogs with myxomatous mitral valve disease

    DEFF Research Database (Denmark)

    Reimann, M. J.; Moller, J. E.; Haggstrom, J.

    2014-01-01

    of congestive heart failure due to MMVD. The severity of MR was evaluated in apical four-chamber view using colour Doppler flow mapping (maximum % of the left atrium area) and colour Doppler M-mode (duration in ms). The influence of the ratio between present and preceding R-R interval on MR severity......Mitral regurgitation (MR) due to myxomatous mitral valve disease (MMVD) is a frequent finding in Cavalier King Charles Spaniels (CKCSs). Sinus arrhythmia and atrial premature complexes leading to R-R interval variations occur in dogs. The aim of the study was to evaluate whether the duration...... of the RR interval immediately influences the degree of MR assessed by echocardiography in dogs. Clinical examination including echocardiography was performed in 103 privately-owned dogs: 16 control Beagles, 70 CKCSs with different degree of MR and 17 dogs of different breeds with clinical signs...

  17. Symbiotic stars

    International Nuclear Information System (INIS)

    Kafatos, M.; Michalitsianos, A.G.

    1984-01-01

    Among the several hundred million binary systems estimated to lie within 3000 light years of the solar system, a tiny fraction, no more than a few hundred, belong to a curious subclass whose radiation has a wavelength distribution so peculiar that it long defied explanation. Such systems radiate strongly in the visible region of the spectrum, but some of them do so even more strongly at both shorter and longer wavelengths: in the ultraviolet region and in the infrared and radio regions. This odd distribution of radiation is best explained by the pairing of a cool red giant star and an intensely hot small star that is virtually in contact with its larger companion. Such objects have become known as symbiotic stars. On photographic plate only the giant star can be discerned, but evidence for the existence of the hot companion has been supplied by satellite-born instruments capable of detecting ultraviolet radiation. The spectra of symbiotic stars indicate that the cool red giant is surrounded by a very hot ionized gas. Symbiotic stars also flared up in outbursts indicating the ejection of material in the form of a shell or a ring. Symbiotic stars may therefore represent a transitory phase in the evolution of certain types of binary systems in which there is substantial transfer of matter from the larger partner to the smaller

  18. Star tracking method based on multiexposure imaging for intensified star trackers.

    Science.gov (United States)

    Yu, Wenbo; Jiang, Jie; Zhang, Guangjun

    2017-07-20

    The requirements for the dynamic performance of star trackers are rapidly increasing with the development of space exploration technologies. However, insufficient knowledge of the angular acceleration has largely decreased the performance of the existing star tracking methods, and star trackers may even fail to track under highly dynamic conditions. This study proposes a star tracking method based on multiexposure imaging for intensified star trackers. The accurate estimation model of the complete motion parameters, including the angular velocity and angular acceleration, is established according to the working characteristic of multiexposure imaging. The estimation of the complete motion parameters is utilized to generate the predictive star image accurately. Therefore, the correct matching and tracking between stars in the real and predictive star images can be reliably accomplished under highly dynamic conditions. Simulations with specific dynamic conditions are conducted to verify the feasibility and effectiveness of the proposed method. Experiments with real starry night sky observation are also conducted for further verification. Simulations and experiments demonstrate that the proposed method is effective and shows excellent performance under highly dynamic conditions.

  19. B- AND A-TYPE STARS IN THE TAURUS-AURIGA STAR-FORMING REGION

    International Nuclear Information System (INIS)

    Mooley, Kunal; Hillenbrand, Lynne; Rebull, Luisa; Padgett, Deborah; Knapp, Gillian

    2013-01-01

    We describe the results of a search for early-type stars associated with the Taurus-Auriga molecular cloud complex, a diffuse nearby star-forming region noted as lacking young stars of intermediate and high mass. We investigate several sets of possible O, B, and early A spectral class members. The first is a group of stars for which mid-infrared images show bright nebulae, all of which can be associated with stars of spectral-type B. The second group consists of early-type stars compiled from (1) literature listings in SIMBAD, (2) B stars with infrared excesses selected from the Spitzer Space Telescope survey of the Taurus cloud, (3) magnitude- and color-selected point sources from the Two Micron All Sky Survey, and (4) spectroscopically identified early-type stars from the Sloan Digital Sky Survey coverage of the Taurus region. We evaluated stars for membership in the Taurus-Auriga star formation region based on criteria involving: spectroscopic and parallactic distances, proper motions and radial velocities, and infrared excesses or line emission indicative of stellar youth. For selected objects, we also model the scattered and emitted radiation from reflection nebulosity and compare the results with the observed spectral energy distributions to further test the plausibility of physical association of the B stars with the Taurus cloud. This investigation newly identifies as probable Taurus members three B-type stars: HR 1445 (HD 28929), τ Tau (HD 29763), 72 Tau (HD 28149), and two A-type stars: HD 31305 and HD 26212, thus doubling the number of stars A5 or earlier associated with the Taurus clouds. Several additional early-type sources including HD 29659 and HD 283815 meet some, but not all, of the membership criteria and therefore are plausible, though not secure, members.

  20. Life of a star

    International Nuclear Information System (INIS)

    Henbest, Nigel.

    1988-01-01

    The paper concerns the theory of stellar evolution. A description is given of:- how a star is born, main sequence stars, red giants, white dwarfs, supernovae, neutron stars and black holes. A brief explanation is given of how the death of a star as a supernova can trigger off the birth of a new generation of stars. Classification of stars and the fate of our sun, are also described. (U.K.)

  1. Understand B-type stars

    Science.gov (United States)

    1982-01-01

    When observations of B stars made from space are added to observations made from the ground and the total body of observational information is confronted with theoretical expectations about B stars, it is clear that nonthermal phenomena occur in the atmospheres of B stars. The nature of these phenomena and what they imply about the physical state of a B star and how a B star evolves are examined using knowledge of the spectrum of a B star as a key to obtaining an understanding of what a B star is like. Three approaches to modeling stellar structure (atmospheres) are considered, the characteristic properties of a mantle, and B stars and evolution are discussed.

  2. Flare stars

    International Nuclear Information System (INIS)

    Nicastro, A.J.

    1981-01-01

    The least massive, but possibly most numerous, stars in a galaxy are the dwarf M stars. It has been observed that some of these dwarfs are characterized by a short increase in brightness. These stars are called flare stars. These flare stars release a lot of energy in a short amount of time. The process producing the eruption must be energetic. The increase in light intensity can be explained by a small area rising to a much higher temperature. Solar flares are looked at to help understand the phenomenon of stellar flares. Dwarfs that flare are observed to have strong magnetic fields. Those dwarf without the strong magnetic field do not seem to flare. It is believed that these regions of strong magnetic fields are associated with star spots. Theories on the energy that power the flares are given. Astrophysicists theorize that the driving force of a stellar flare is the detachment and collapse of a loop of magnetic flux. The mass loss due to stellar flares is discussed. It is believed that stellar flares are a significant contributor to the mass of interstellar medium in the Milky Way

  3. By Draconis Stars

    Science.gov (United States)

    Bopp, Bernard W.

    An optical spectroscopic survey of dK-M stars has resulted in the discovery of several new H-alpha emission objects. Available optical data suggest these stars have a level of chromospheric activity midway between active BY Dra stars and quiet dM's. These "marginal" BY Dra stars are single objects that have rotation velocities slightly higher than that of quiet field stars but below that of active flare/BY Dra objects. The marginal BY Dra stars provide us with a class of objects rotating very near a "trigger velocity" (believed to be 5 km/s) which appears to divide active flare/BY Dra stars from quiet dM's. UV data on Mg II emission fluxes and strength of transition region features such as C IV will serve to fix activity levels in the marginal objects and determine chromosphere and transition-region heating rates. Simultaneous optical magnetic field measures will be used to explore the connection between fieldstrength/filling-factor and atmospheric heating. Comparison of these data with published information on active and quiet dM stars will yield information on the character of the stellar dynamo as it makes a transition from "low" to "high" activity.

  4. The Half RR Rule: A Poor Rule of Thumb and Not a Risk Assessment Tool for QT Interval Prolongation.

    Science.gov (United States)

    Berling, Ingrid; Isbister, Geoffrey K

    2015-10-01

    Measuring the QT interval on an electrocardiogram (ECG) is integral to risk assessment of Torsade de Pointes (TdP). This study aimed to investigate the accuracy of the 1/2 RR rule as a risk assessment tool for drug-induced TdP, comparing it to the QT nomogram, Bazett's corrected QT (QTcB), and Fridericia's corrected QT (QTcF). The authors calculated sensitivity and specificity of the 1/2 RR rule using a published data set of 129 cases of drug-induced TdP and 316 controls (noncardiotoxic overdoses), compared to the QT nomogram, QTcB > 500 msec and QTcF > 500 msec. To further determine the value of the 1/2 RR rule, its observed positive, and negative agreement were calculated when compared to the QT nomogram for determining an abnormal QT in eight samples of different drugs in overdose. The sensitivity and specificity of the 1/2 RR rule were 88% (95% confidence interval [CI] = 80% to 93%) and 53% (95% CI = 47% to 58%), respectively, compared to the QT nomogram (sensitivity = 97%, 95% CI = 92% to 99%; specificity = 99%, 95% CI = 97% to 100%). It was also less sensitive than QTcB > 500 msec and had a lower specificity than QTcB > 500 msec and QTcF > 500 msec. In drug overdose patients, the 1/2 RR rule had poor observed agreement averaging 41%, which was mainly due to poor positive agreement, except for amisulpride where there was good agreement. The 1/2 RR rule was not as sensitive as the QT nomogram or QTcB > 500 msec for drug-induced TdP. It had poor positive agreement in almost all overdose patients, resulting in over half of patients receiving unnecessary cardiac monitoring and repeat ECGs. © 2015 by the Society for Academic Emergency Medicine.

  5. Shooting stars

    International Nuclear Information System (INIS)

    Maurette, M.; Hammer, C.

    1985-01-01

    A shooting star passage -even a star shower- can be sometimes easily seen during moonless black night. They represent the partial volatilization in earth atmosphere of meteorites or micrometeorites reduced in cosmic dusts. Everywhere on earth, these star dusts are searched to be gathered. This research made one year ago on the Greenland ice-cap is this article object; orbit gathering projects are also presented [fr

  6. The Vixen Star Book user guide how to use the star book ten and the original star book

    CERN Document Server

    Chen, James

    2016-01-01

    This book is for anyone who owns, or is thinking of owning, a Vixen Star Book Ten telescope mount or its predecessor. A revolution in amateur astronomy has occurred in the past decade with the wide availability of high tech, computer-driven, Go-To telescopes. Vixen Optics is leading the way by offering the Star Book Ten system, with its unique star map graphics software. The Star Book Ten is the latest version of computer telescope control using star map graphics as a user interface, first introduced in the original Star Book first offered in 2003. The increasingly complicated nature of this software means that learning to optimize this program is not straightforward, and yet the resulting views when all features are correctly deployed can be phenomenal. After a short history of computerized Go-To telescopes for the consumer amateur astronomer market, Chen offers a treasury of technical information. His advice, tips, and solutions aid the user in getting the most out of the Star Book Ten system in observing s...

  7. Dynamics of microcystins-LR and -RR in the phytoplanktivorous silver carp in a sub-chronic toxicity experiment

    International Nuclear Information System (INIS)

    Xie Liqiang; Xie Ping; Ozawa, Kazuhiko; Honma, Takamitsu; Yokoyama, Atsushi; Park, Ho-Dong

    2004-01-01

    A sub-chronic toxicity experiment was conducted to examine tissue distribution and depuration of two microcystins (microcystin-LR and microcystin -RR) in the phytoplanktivorous filter-feeding silver carp during a course of 80 days. Two large tanks (A, B) were used, and in Tank A, the fish were fed naturally with fresh Microcystis viridis cells (collected from a eutrophic pond) throughout the experiment, while in Tank B, the food of the fish were M. viridis cells for the first 40 days and then changed to artificial carp feed. High Performance Liquid Chromatography (HPLC) was used to measure MC-LR and MC-RR in the M. viridis cells, the seston, and the intestine, blood, liver and muscle tissue of silver carp at an interval of 20 days. MC-RR and MC-LR in the collected Microcystis cells varied between 268-580 and 110-292 μg g -1 DW, respectively. In Tank A, MC-RR and MC-LR varied between 41.5-99.5 and 6.9-15.8 μg g -1 DW in the seston, respectively. The maximum MC-RR in the blood, liver and muscle of the fish was 49.7, 17.8 and 1.77 μg g -1 DW, respectively. No MC-LR was detectable in the muscle and blood samples of the silver carp in spite of the abundant presence of this toxin in the intestines (for the liver, there was only one case when a relatively minor quantity was detected). These findings contrast with previous experimental results on rainbow trout. Perhaps silver carp has a mechanism to degrade MC-LR actively and to inhibit MC-LR transportation across the intestines. The depuration of MC-RR concentrations occurred slowly than uptakes in blood, liver and muscle, and the depuration rate was in the order of blood>liver>muscle. The grazing ability of silver carp on toxic cyanobacteria suggests an applicability of using phytoplanktivorous fish to counteract cyanotoxin contamination in eutrophic waters. - Silver carp are tolerant of cyanobacterial toxins, and might be used to control toxic algal blooms in highly eutrophic lakes

  8. STAR-TO-STAR IRON ABUNDANCE VARIATIONS IN RED GIANT BRANCH STARS IN THE GALACTIC GLOBULAR CLUSTER NGC 3201

    International Nuclear Information System (INIS)

    Simmerer, Jennifer; Ivans, Inese I.; Filler, Dan; Francois, Patrick; Charbonnel, Corinne; Monier, Richard; James, Gaël

    2013-01-01

    We present the metallicity as traced by the abundance of iron in the retrograde globular cluster NGC 3201, measured from high-resolution, high signal-to-noise spectra of 24 red giant branch stars. A spectroscopic analysis reveals a spread in [Fe/H] in the cluster stars at least as large as 0.4 dex. Star-to-star metallicity variations are supported both through photometry and through a detailed examination of spectra. We find no correlation between iron abundance and distance from the cluster core, as might be inferred from recent photometric studies. NGC 3201 is the lowest mass halo cluster to date to contain stars with significantly different [Fe/H] values.

  9. Star-to-star Iron Abundance Variations in Red Giant Branch Stars in the Galactic Globular Cluster NGC 3201

    Science.gov (United States)

    Simmerer, Jennifer; Ivans, Inese I.; Filler, Dan; Francois, Patrick; Charbonnel, Corinne; Monier, Richard; James, Gaël

    2013-02-01

    We present the metallicity as traced by the abundance of iron in the retrograde globular cluster NGC 3201, measured from high-resolution, high signal-to-noise spectra of 24 red giant branch stars. A spectroscopic analysis reveals a spread in [Fe/H] in the cluster stars at least as large as 0.4 dex. Star-to-star metallicity variations are supported both through photometry and through a detailed examination of spectra. We find no correlation between iron abundance and distance from the cluster core, as might be inferred from recent photometric studies. NGC 3201 is the lowest mass halo cluster to date to contain stars with significantly different [Fe/H] values.

  10. Uncertain Classification of Variable Stars: Handling Observational GAPS and Noise

    Science.gov (United States)

    Castro, Nicolás; Protopapas, Pavlos; Pichara, Karim

    2018-01-01

    Automatic classification methods applied to sky surveys have revolutionized the astronomical target selection process. Most surveys generate a vast amount of time series, or “lightcurves,” that represent the brightness variability of stellar objects in time. Unfortunately, lightcurves’ observations take several years to be completed, producing truncated time series that generally remain without the application of automatic classifiers until they are finished. This happens because state-of-the-art methods rely on a variety of statistical descriptors or features that present an increasing degree of dispersion when the number of observations decreases, which reduces their precision. In this paper, we propose a novel method that increases the performance of automatic classifiers of variable stars by incorporating the deviations that scarcity of observations produces. Our method uses Gaussian process regression to form a probabilistic model of each lightcurve’s observations. Then, based on this model, bootstrapped samples of the time series features are generated. Finally, a bagging approach is used to improve the overall performance of the classification. We perform tests on the MAssive Compact Halo Object (MACHO) and Optical Gravitational Lensing Experiment (OGLE) catalogs, results show that our method effectively classifies some variability classes using a small fraction of the original observations. For example, we found that RR Lyrae stars can be classified with ~80% accuracy just by observing the first 5% of the whole lightcurves’ observations in the MACHO and OGLE catalogs. We believe these results prove that, when studying lightcurves, it is important to consider the features’ error and how the measurement process impacts it.

  11. The first stars: CEMP-no stars and signatures of spinstars

    Science.gov (United States)

    Maeder, André; Meynet, Georges; Chiappini, Cristina

    2015-04-01

    Aims: The CEMP-no stars are "carbon-enhanced-metal-poor" stars that in principle show no evidence of s- and r-elements from neutron captures. We try to understand the origin and nucleosynthetic site of their peculiar CNO, Ne-Na, and Mg-Al abundances. Methods: We compare the observed abundances to the nucleosynthetic predictions of AGB models and of models of rotating massive stars with internal mixing and mass loss. We also analyze the different behaviors of α- and CNO-elements, as well the abundances of elements involved in the Ne-Na and Mg-Al cycles. Results: We show that CEMP-no stars exhibit products of He-burning that have gone through partial mixing and processing by the CNO cycle, producing low 12C/13C and a broad variety of [C/N] and [O/N] ratios. From a 12C/13C vs. [C/N] diagram, we conclude that neither the yields of AGB stars (in binaries or not) nor the yields of classic supernovae can fully account for the observed CNO abundances in CEMP-no stars. Better agreement is obtained once the chemical contribution by stellar winds of fast-rotating massive stars is taken into account, where partial mixing takes place, leading to various amounts of CNO being ejected. The [(C+N+O)/H] ratios of CEMP-no stars vary linearly with [Fe/H] above [Fe/H] = -4.0 indicating primary behavior by (C+N+O). Below [Fe/H] = -4.0, [(C+N+O)/H] is almost constant as a function of [Fe/H], implying very high [(C+N+O)/Fe] ratios up to 4 dex. In view of the timescales, such abundance ratios reflect more individual nucleosynthetic properties, rather than an average chemical evolution. The high [(C+N+O)/Fe] ratios (as well as the high [(C+N+O)/α-elements]) imply that stellar winds from partially mixed stars were the main source of these excesses of heavy elements now observed in CEMP-no stars. The ranges covered by the variations of [Na/Fe], [Mg/Fe], and [Al/Fe] are much broader than for the α-elements (with an atomic mass number above 24) and are comparable to the wide ranges covered

  12. Toothpick test: a methodology for the detection of RR soybean plants1

    Directory of Open Access Journals (Sweden)

    Fabiana Mota da Silva

    Full Text Available Due to the large increase in the area cultivated with genetically modified soybean in Brazil, it has become necessary to determine methods that are fast and efficient for detecting these cultivars. The aim of this work was to test the efficiency of the toothpick method in the detection of RR soybean plants, as well as to distinguish between cultivars, for sensitivity caused by herbicide. Ten transgenic soybean cultivars, resistant to the active ingredient glyphosate, and ten conventional soybean cultivars were used. Toothpicks soaked in glyphosate were applied to all the plants at stage V6 and evaluations were made at 2, 4, 6, 8 and 10 days after application (DAA. The effects of the glyphosate on the cultivars, and the symptoms of phytotoxicity caused in the transgenic plants were evaluated by means of grading scales. The toothpick test is effective in identifying RR soybean cultivars and also in separating them into groups by sensitivity to the symptoms caused by the glyphosate.

  13. Pressure drop in ET-RR-1

    International Nuclear Information System (INIS)

    Khattab, M.; Mina, A.R.

    1990-01-01

    Measurements of pressure drop through a bundle comprising 16 rods and their lower arrangement grid as well as orifices similar to those of ET-RR-1 core have been done. Experiments are carried out under adiabatic turbulent flow conditions at about 35 degree C. Bundle Reynolds number range is 4 x 10 -2 x 10. Orifices of diameters 4.5, 3.25 or 2.5 cm. are mounted underneath the bundle. The bundle and lower grid pressure drop coefficients are 3.75 and 1.8 respectively. Orifices pressure drop coefficients are 2.65, 19.67 and 53.55 respectively. The ratio of bundle pressure drop to that of 4.5 cm. Orifice diameter is 1.415. The pressure drop coefficients are utilizer to calculate flow through bundles. The flow rate per bundle is 39.1, 20.4 or 13.1 m 3 /hr. Depending on orifice diameter

  14. 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.

  15. Motion-blurred star acquisition method of the star tracker under high dynamic conditions.

    Science.gov (United States)

    Sun, Ting; Xing, Fei; You, Zheng; Wei, Minsong

    2013-08-26

    The star tracker is one of the most promising attitude measurement devices used in spacecraft due to its extremely high accuracy. However, high dynamic performance is still one of its constraints. Smearing appears, making it more difficult to distinguish the energy dispersive star point from the noise. An effective star acquisition approach for motion-blurred star image is proposed in this work. The correlation filter and mathematical morphology algorithm is combined to enhance the signal energy and evaluate slowly varying background noise. The star point can be separated from most types of noise in this manner, making extraction and recognition easier. Partial image differentiation is then utilized to obtain the motion parameters from only one image of the star tracker based on the above process. Considering the motion model, the reference window is adopted to perform centroid determination. Star acquisition results of real on-orbit star images and laboratory validation experiments demonstrate that the method described in this work is effective and the dynamic performance of the star tracker could be improved along with more identified stars and guaranteed position accuracy of the star point.

  16. Rodent Research-1 (RR1) NASA Validation Flight: Mouse eye transcriptomic and epigenomic data

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA s Rodent Research (RR) project is playing a critical role in advancing biomedical research on the physiological effects of space environments. Due to the...

  17. Energy production in stars

    International Nuclear Information System (INIS)

    Bethe, Hans.

    1977-01-01

    Energy in stars is released partly by gravitation, partly by nuclear reactions. For ordinary stars like our sun, nuclear reactions predominate. However, at the end of the life of a star very large amounts of energy are released by gravitational collapse; this can amount to as much as 10 times the total energy released nuclear reactions. The rotational energy of pulsars is a small remnant of the energy of gravitation. The end stage of small stars is generally a white dwarf, of heavy stars a neutron star of possibly a black hole

  18. 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.

  19. SECULAR STELLAR DYNAMICS NEAR A MASSIVE BLACK HOLE

    International Nuclear Information System (INIS)

    Madigan, Ann-Marie; Hopman, Clovis; Levin, Yuri

    2011-01-01

    The angular momentum evolution of stars close to massive black holes (MBHs) is driven by secular torques. In contrast to two-body relaxation, where interactions between stars are incoherent, the resulting resonant relaxation (RR) process is characterized by coherence times of hundreds of orbital periods. In this paper, we show that all the statistical properties of RR can be reproduced in an autoregressive moving average (ARMA) model. We use the ARMA model, calibrated with extensive N-body simulations, to analyze the long-term evolution of stellar systems around MBHs with Monte Carlo simulations. We show that for a single-mass system in steady state, a depression is carved out near an MBH as a result of tidal disruptions. Using Galactic center parameters, the extent of the depression is about 0.1 pc, of similar order to but less than the size of the observed 'hole' in the distribution of bright late-type stars. We also find that the velocity vectors of stars around an MBH are locally not isotropic. In a second application, we evolve the highly eccentric orbits that result from the tidal disruption of binary stars, which are considered to be plausible precursors of the 'S-stars' in the Galactic center. We find that RR predicts more highly eccentric (e > 0.9) S-star orbits than have been observed to date.

  20. Secular Stellar Dynamics near a Massive Black Hole

    Science.gov (United States)

    Madigan, Ann-Marie; Hopman, Clovis; Levin, Yuri

    2011-09-01

    The angular momentum evolution of stars close to massive black holes (MBHs) is driven by secular torques. In contrast to two-body relaxation, where interactions between stars are incoherent, the resulting resonant relaxation (RR) process is characterized by coherence times of hundreds of orbital periods. In this paper, we show that all the statistical properties of RR can be reproduced in an autoregressive moving average (ARMA) model. We use the ARMA model, calibrated with extensive N-body simulations, to analyze the long-term evolution of stellar systems around MBHs with Monte Carlo simulations. We show that for a single-mass system in steady state, a depression is carved out near an MBH as a result of tidal disruptions. Using Galactic center parameters, the extent of the depression is about 0.1 pc, of similar order to but less than the size of the observed "hole" in the distribution of bright late-type stars. We also find that the velocity vectors of stars around an MBH are locally not isotropic. In a second application, we evolve the highly eccentric orbits that result from the tidal disruption of binary stars, which are considered to be plausible precursors of the "S-stars" in the Galactic center. We find that RR predicts more highly eccentric (e > 0.9) S-star orbits than have been observed to date.

  1. [The influence of age and illness duration on cognitive impairment in aging patients with relapsing-remitting multiple sclerosis (RR-MS)].

    Science.gov (United States)

    Leclercq, Eugénie; Cabaret, Maryline; Guilbert, Alma; Jougleux, Caroline; Vermersch, Patrick; Moroni, Christine

    2014-09-01

    The aim of this study was to dissociate age and duration of illness effects on cognitive impairment of patients with relapsing-remitting multiple sclerosis. Cognitive impairment among patients with multiple sclerosis (MS) is well known. However, few studies were devoted to assess the respective role of disease duration and age on cognitive functions in MS patients. Therefore, two studies were carried out on relapsing-remitting MS (RR-MS) patients using some tests of the BCcogSEP--a French test battery evaluating cognitive functions in MS. The cognitive deficits of RR-MS patients aged 50 years and over and whose symptoms had been present for more than 20 years were more severe than those of MS patients with a shorter illness duration (less than 10 years) or matched-age control participants. The more impaired cognitive functions were information-processing speed, episodic memory, verbal fluency and attention. On the other hand, cognitive performances of young RR-MS patients were similar to those of older RR-MS patients when all patients had the same illness duration (8 years in this study). Older patients even achieved better performance than younger ones on verbal fluency. This can be partly explained by the theory of cognitive reserve, as reported in previous cognitive aging studies. In RR-MS patients, the influence of illness duration seems to be a predominant factor in the development of cognitive impairment.

  2. How bright planets became dim stars: planetary speculations in John Herschel's double star astronomy.

    Science.gov (United States)

    Case, Stephen

    2014-03-01

    Previous research on the origins of double star astronomy in the early nineteenth century emphasized the role mathematical methods and instrumentation played in motivating early observations of these objects. The work of the British astronomer John Herschel, however, shows that questions regarding the physical nature of double stars were also important. In particular, an analysis of John Herschel's early work on double stars illustrates the way in which speculations regarding these objects were shaped by assumptions of the properties of stars themselves. For Herschel, a major consideration in double star astronomy was distinguishing between types of double stars. Optical doubles were useful in determining parallax while binary doubles were not. In practice, classification of a specific double star pair into one of these categories was based on the assumption that stars were of approximately the same luminosity and thus differences in relative brightness between stars were caused by difference in distances. Such assumptions, though ultimately abandoned, would lead Herschel in the 1830s to advance the possibility that the dim companion stars in certain double star pairs were not stars at all but in fact planets. Copyright © 2014 Elsevier Ltd. All rights reserved.

  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. Spectrophotometry of peculiar B and A stars. II. Eleven mercury-manganese stars

    International Nuclear Information System (INIS)

    Adelman, S.J.; Pyper, D.M.

    1979-01-01

    Spectrophotometry of eleven HgMn stars is presented for the optical region. As found in Paper I, the HgMn stars have systematically larger Δiota* and Δa values than the normal main sequence stars due to differences with respect to the mean continuum particularly of the lambda4464 values and the lambda5200 region, respectively. The HgMn stars exhibit a continuous range in the behavior of both the lambda4200 and lambda5200 regions between those stars that have index values larger than the appropriate criterion of presence and present definite evidence for the features to those stars with only a slight possibility of such features. The strengths of the lambda4200 and lambda5200 features appear not to be correlated. In the HgMn stars, both features may be due to differential line blocking. In the energy distribution of all eleven stars, the Balmer jump regions best fit the predictions of slightly hotter solar composition, log g=4.0, fully line blanketed model atmospheres than do the corresponding Paschen continua

  5. Discriminating strange star mergers from neutron star mergers by gravitational-wave measurements

    International Nuclear Information System (INIS)

    Bauswein, A.; Oechslin, R.; Janka, H.-T.

    2010-01-01

    We perform three-dimensional relativistic hydrodynamical simulations of the coalescence of strange stars and explore the possibility to decide on the strange matter hypothesis by means of gravitational-wave measurements. Self-binding of strange quark matter and the generally more compact stars yield features that clearly distinguish strange star from neutron star mergers, e.g. hampering tidal disruption during the plunge of quark stars. Furthermore, instead of forming dilute halo structures around the remnant as in the case of neutron star mergers, the coalescence of strange stars results in a differentially rotating hypermassive object with a sharp surface layer surrounded by a geometrically thin, clumpy high-density strange quark matter disk. We also investigate the importance of including nonzero temperature equations of state in neutron star and strange star merger simulations. In both cases we find a crucial sensitivity of the dynamics and outcome of the coalescence to thermal effects, e.g. the outer remnant structure and the delay time of the dense remnant core to black hole collapse depend on the inclusion of nonzero temperature effects. For comparing and classifying the gravitational-wave signals, we use a number of characteristic quantities like the maximum frequency during inspiral or the dominant frequency of oscillations of the postmerger remnant. In general, these frequencies are higher for strange star mergers. Only for particular choices of the equation of state the frequencies of neutron star and strange star mergers are similar. In such cases additional features of the gravitational-wave luminosity spectrum like the ratio of energy emitted during the inspiral phase to the energy radiated away in the postmerger stage may help to discriminate coalescence events of the different types. If such characteristic quantities could be extracted from gravitational-wave signals, for instance with the upcoming gravitational-wave detectors, a decision on the

  6. X-ray sources in regions of star formation. I. The naked T Tauri stars

    International Nuclear Information System (INIS)

    Walter, F.M.

    1986-01-01

    Einstein X-ray observations of regions of active star formation in Taurus, Ophiuchus, and Corona Australis show a greatly enhanced surface density of stellar X-ray sources over that seen in other parts of the sky. Many of the X-ray sources are identified with low-mass, pre-main-sequence stars which are not classical T Tauri stars. The X-ray, photometric, and spectroscopic data for these stars are discussed. Seven early K stars in Oph and CrA are likely to be 1-solar-mass post-T Tauri stars with ages of 10-million yr. The late K stars in Taurus are not post-T Tauri, but naked T Tauri stars, which are coeval with the T Tauri stars, differing mainly in the lack of a circumstellar envelope. 72 references

  7. 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....

  8. RR Lyrae and BL Herculis variables

    International Nuclear Information System (INIS)

    Cox, A.N.

    1980-01-01

    The RR Lyrae variables are currently believed to have masses between about 0.5 and 0.8 M/sub solar mass/, effective surface temperatures between 6350 and 7500 0 K, radii from about 4.0 to 6.0 R/sub solar mass/ and luminosities between log L/L/sub solar mass/ of 1.5 and 2.0. Since they are found in population II locations, they generally have Y = 0.3 and Z = 10 -3 , but there are exceptions for both higher Z like the sun and lower Z like 0.0002. In globular clusters the periods range from 0.25 to 0.45 day for the first overtone pulsators and 0.40 to 0.80 day for those in the fundamental mode, depending on their luminosity. At transition lines, discussed in detail, the switch from fundamental to first overtone, or maybe vice versa, involves a period change factor of about 0.74 to 0.75

  9. Descendants of the first stars: the distinct chemical signature of second generation stars

    Science.gov (United States)

    Hartwig, Tilman; Yoshida, Naoki; Magg, Mattis; Frebel, Anna; Glover, Simon C. O.; Gómez, Facundo A.; Griffen, Brendan; Ishigaki, Miho N.; Ji, Alexander P.; Klessen, Ralf S.; O'Shea, Brian W.; Tominaga, Nozomu

    2018-05-01

    Extremely metal-poor (EMP) stars in the Milky Way (MW) allow us to infer the properties of their progenitors by comparing their chemical composition to the metal yields of the first supernovae. This method is most powerful when applied to mono-enriched stars, i.e. stars that formed from gas that was enriched by only one previous supernova. We present a novel diagnostic to identify this subclass of EMP stars. We model the first generations of star formation semi-analytically, based on dark matter halo merger trees that yield MW-like halos at the present day. Radiative and chemical feedback are included self-consistently and we trace all elements up to zinc. Mono-enriched stars account for only ˜1% of second generation stars in our fiducial model and we provide an analytical formula for this probability. We also present a novel analytical diagnostic to identify mono-enriched stars, based on the metal yields of the first supernovae. This new diagnostic allows us to derive our main results independently from the specific assumptions made regarding Pop III star formation, and we apply it to a set of observed EMP stars to demonstrate its strengths and limitations. Our results may provide selection criteria for current and future surveys and therefore contribute to a deeper understanding of EMP stars and their progenitors.

  10. Neutron star formation in theoretical supernovae. Low mass stars and white dwarfs

    International Nuclear Information System (INIS)

    Nomoto, K.

    1986-01-01

    The presupernova evolution of stars that form semi-degenerate or strongly degenerate O + Ne + Mg cores is discussed. For the 10 to 13 Msub solar stars, behavior of off-center neon flashes is crucial. The 8 to 10 m/sub solar stars do not ignite neon and eventually collapse due to electron captures. Properties of supernova explosions and neutron stars expected from these low mass progenitors are compared with the Crab nebula. The conditions for which neutron stars form from accretion-induced collapse of white dwarfs in clsoe binary systems is also examined

  11. 76 FR 20229 - Airworthiness Directives; Rolls-Royce plc (RR) RB211-Trent 768-60 and Trent 772-60 Turbofan Engines

    Science.gov (United States)

    2011-04-12

    ... inspections of the MCD. We are issuing this AD to prevent in-flight engine shutdowns caused by step aside... Airworthiness Directives; Rolls-Royce plc (RR) RB211-Trent 768-60 and Trent 772-60 Turbofan Engines AGENCY... superseding an existing airworthiness directive (AD) for RR RB211-Trent 700 series turbofan engines. That AD...

  12. General Relativity and Compact Stars

    International Nuclear Information System (INIS)

    Glendenning, Norman K.

    2005-01-01

    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 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

  13. Star formation

    International Nuclear Information System (INIS)

    Woodward, P.R.

    1978-01-01

    Theoretical models of star formation are discussed beginning with the earliest stages and ending in the formation of rotating, self-gravitating disks or rings. First a model of the implosion of very diffuse gas clouds is presented which relies upon a shock at the edge of a galactic spiral arm to drive the implosion. Second, models are presented for the formation of a second generation of massive stars in such a cloud once a first generation has formed. These models rely on the ionizing radiation from massive stars or on the supernova shocks produced when these stars explode. Finally, calculations of the gravitational collapse of rotating clouds are discussed with special focus on the question of whether rotating disks or rings are the result of such a collapse. 65 references

  14. Dark stars: a new study of the first stars in the Universe

    International Nuclear Information System (INIS)

    Freese, Katherine; Bodenheimer, Peter; Gondolo, Paolo; Spolyar, Douglas

    2009-01-01

    We have proposed that the first phase of stellar evolution in the history of the Universe may be dark stars (DSs), powered by dark matter (DM) heating rather than by nuclear fusion. Weakly interacting massive particles, which may be their own antipartners, collect inside the first stars and annihilate to produce a heat source that can power the stars. A new stellar phase results, a DS, powered by DM annihilation as long as there is DM fuel, with lifetimes from millions to billions of years. We find that the first stars are very bright (∼10 6 L o-dot ) and cool (T surf surf > 50 000 K); hence DS should be observationally distinct from standard Pop III stars. Once the DM fuel is exhausted, the DS becomes a heavy main sequence star; these stars eventually collapse to form massive black holes that may provide seeds for supermassive black holes observed at early times as well as explanations for recent ARCADE data and for intermediate black holes.

  15. Gated current integrator for the beam in the RR barrier buckets

    Energy Technology Data Exchange (ETDEWEB)

    A. Cadorn; C. Bhat; J. Crisp

    2003-06-10

    At the Fermilab Recycler Ring (RR), the antiproton (pbar) beam will be stored azimuthally in different segments created by barrier buckets. The beam in each segment may have widely varying intensities. They have developed a gated integrator system to measure the beam intensity in each of the barrier bucket. Here they discuss the design of the system and the results of beam measurements using the integrator.

  16. Introduction to neutron stars

    Energy Technology Data Exchange (ETDEWEB)

    Lattimer, James M. [Dept. of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)

    2015-02-24

    Neutron stars contain the densest form of matter in the present universe. General relativity and causality set important constraints to their compactness. In addition, analytic GR solutions are useful in understanding the relationships that exist among the maximum mass, radii, moments of inertia, and tidal Love numbers of neutron stars, all of which are accessible to observation. Some of these relations are independent of the underlying dense matter equation of state, while others are very sensitive to the equation of state. Recent observations of neutron stars from pulsar timing, quiescent X-ray emission from binaries, and Type I X-ray bursts can set important constraints on the structure of neutron stars and the underlying equation of state. In addition, measurements of thermal radiation from neutron stars has uncovered the possible existence of neutron and proton superfluidity/superconductivity in the core of a neutron star, as well as offering powerful evidence that typical neutron stars have significant crusts. These observations impose constraints on the existence of strange quark matter stars, and limit the possibility that abundant deconfined quark matter or hyperons exist in the cores of neutron stars.

  17. Polarization of Be stars

    International Nuclear Information System (INIS)

    Johns, M.W.

    1975-01-01

    Linear polarization of starlight may be produced by electron scattering in the extended atmospheres of early type stars. Techniques are investigated for the measurement and interpretation of this polarization. Polarimetric observations were made of twelve visual double star systems in which at least one member was a B type star as a means of separating the intrinsic stellar polarization from the polarization produced in the interstellar medium. Four of the double stars contained a Be star. Evidence for intrinsic polarization was found in five systems including two of the Be systems, one double star with a short period eclipsing binary, and two systems containing only normal early type stars for which emission lines have not been previously reported. The interpretation of these observations in terms of individual stellar polarizations and their wavelength dependence is discussed. The theoretical basis for the intrinsic polarization of early type stars is explored with a model for the disk-like extended atmospheres of Be stars. Details of a polarimeter for the measurement of the linear polarization of astronomical point sources are also presented with narrow band (Δ lambda = 100A) measurements of the polarization of γ Cas from lambda 4000 to lambda 5800

  18. Rates of star formation

    International Nuclear Information System (INIS)

    Larson, R.B.

    1977-01-01

    It is illustrated that a theoretical understanding of the formation and evolution of galaxies depends on an understanding of star formation, and especially of the factors influencing the rate of star formation. Some of the theoretical problems of star formation in galaxies, some approaches that have been considered in models of galaxy evolution, and some possible observational tests that may help to clarify which processes or models are most relevant are reviewed. The material is presented under the following headings: power-law models for star formation, star formation processes (conditions required, ways of achieving these conditions), observational indications and tests, and measures of star formation rates in galaxies. 49 references

  19. 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

  20. INFRARED TWO-COLOR DIAGRAMS FOR AGB STARS, POST-AGB STARS, AND PLANETARY NEBULAE

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Kyung-Won, E-mail: kwsuh@chungbuk.ac.kr [Department of Astronomy and Space Science, Chungbuk National University, Cheongju-City, 362-763 (Korea, Republic of)

    2015-08-01

    We present various infrared two-color diagrams (2CDs) for asymptotic giant branch (AGB) stars, post-AGB stars, and Planetary Nebulae (PNe) and investigate possible evolutionary tracks. We use catalogs from the available literature for the sample of 4903 AGB stars (3373 O-rich; 1168 C-rich; 362 S-type), 660 post-AGB stars (326 post-AGB; 334 pre-PN), and 1510 PNe in our Galaxy. For each object in the catalog, we cross-identify the IRAS, AKARI, Midcourse Space Experiment, and 2MASS counterparts. The IR 2CDs can provide useful information about the structure and evolution of the dust envelopes as well as the central stars. To find possible evolutionary tracks from AGB stars to PNe on the 2CDs, we investigate spectral evolution of post-AGB stars by making simple but reasonable assumptions on the evolution of the central star and dust shell. We perform radiative transfer model calculations for the detached dust shells around evolving central stars in the post-AGB phase. We find that the theoretical dust shell model tracks using dust opacity functions of amorphous silicate and amorphous carbon roughly coincide with the densely populated observed points of AGB stars, post-AGB stars, and PNe on various IR 2CDs. Even though some discrepancies are inevitable, the end points of the theoretical post-AGB model tracks generally converge in the region of the observed points of PNe on most 2CDs.

  1. 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

  2. Morphology and metallicity of the Small Magellanic Cloud using RRab stars

    Science.gov (United States)

    Deb, Sukanta; Singh, Harinder P.; Kumar, Subhash; Kanbur, Shashi M.

    2015-05-01

    We present a study of three-dimensional structure of the Small Magellanic Cloud (SMC). The V- and I-band light curves of the fundamental mode RR Lyrae (RRab) stars obtained by the Optical Gravitational Lensing Experiment-III project were utilized in order to comprehend the SMC structure. The [Fe/H]-P-φ31 relation of Jurcsik & Kovacs is exploited to obtain the metallicities. From the three-dimensional RRab distance distributions, north-east arm and main body of the galaxy are identified. Combining metallicities with spatial distribution of these tracers, no radial metallicity gradient in the SMC has been detected. Dividing the entire sample into three parts: north-eastern, central and south-western, we find that the central part has a significantly larger line of sight depth as compared to rest of the parts, indicating that the SMC may have a bulge. Results obtained from the I-band data seem to be reliable and were further substantiated using the Smolec relation. Distribution of SMC RRab stars was modelled as a triaxial ellipsoid. Errors in structural parameters of the SMC ellipsoid were obtained from Monte Carlo simulations. We estimated the axes ratios of the galaxy as 1.00 ± 0.000: 1.310 ± 0.029: 8.269 ± 0.934, the inclination of the longest axis with line of sight i = 2.265° ± 0.784° and the position angle of the line of nodes θlon = 74.307° ± 0.509° from the variance weighted I-band determinations.

  3. Wolf-Rayet stars and O-star runaways with HIPPARCOS - I. Kinematics

    NARCIS (Netherlands)

    Moffat, AFJ; Marchenko, SV; Seggewiss, W; van der Hucht, KA; Schrijver, H; Stenholm, B; Lundstrom, [No Value; Gunawan, DYAS; Sutantyo, W; van den Heuvel, EPJ; De Cuyper, JP; Gomez, AE

    Reliable systemic radial velocities are almost impossible to secure for Wolf-Rayet stars, difficult for O stars. Therefore, to study the motions - both systematic in the Galaxy and peculiar - of these two related types of hot, luminous star, we have examined the Hipparcos proper motions of some 70

  4. Evolution of variable stars

    International Nuclear Information System (INIS)

    Becker, S.A.

    1986-08-01

    Throughout the domain of the H R diagram lie groupings of stars whose luminosity varies with time. These variable stars can be classified based on their observed properties into distinct types such as β Cephei stars, δ Cephei stars, and Miras, as well as many other categories. The underlying mechanism for the variability is generally felt to be due to four different causes: geometric effects, rotation, eruptive processes, and pulsation. In this review the focus will be on pulsation variables and how the theory of stellar evolution can be used to explain how the various regions of variability on the H R diagram are populated. To this end a generalized discussion of the evolutionary behavior of a massive star, an intermediate mass star, and a low mass star will be presented. 19 refs., 1 fig., 1 tab

  5. A new method for determining which stars are near a star sensor field-of-view

    Science.gov (United States)

    Yates, Russell E., Jr.; Vedder, John D.

    1991-01-01

    A new method is described for determining which stars in a navigation star catalog are near a star sensor field of view (FOV). This method assumes that an estimate of spacecraft inertial attitude is known. Vector component ranges for the star sensor FOV are computed, so that stars whose vector components lie within these ranges are near the star sensor FOV. This method requires no presorting of the navigation star catalog, and is more efficient than tradition methods.

  6. Star identification methods, techniques and algorithms

    CERN Document Server

    Zhang, Guangjun

    2017-01-01

    This book summarizes the research advances in star identification that the author’s team has made over the past 10 years, systematically introducing the principles of star identification, general methods, key techniques and practicable algorithms. It also offers examples of hardware implementation and performance evaluation for the star identification algorithms. Star identification is the key step for celestial navigation and greatly improves the performance of star sensors, and as such the book include the fundamentals of star sensors and celestial navigation, the processing of the star catalog and star images, star identification using modified triangle algorithms, star identification using star patterns and using neural networks, rapid star tracking using star matching between adjacent frames, as well as implementation hardware and using performance tests for star identification. It is not only valuable as a reference book for star sensor designers and researchers working in pattern recognition and othe...

  7. On the evolution of stars

    International Nuclear Information System (INIS)

    Kippenhahn, R.

    1989-01-01

    A popular survey is given of the present knowledge on evolution and ageing of stars. Main sequence stars, white dwarf stars, and red giant stars are classified in the Hertzsprung-Russell (HR)-diagram by measurable quantities: surface temperature and luminosity. From the HR-diagram it can be concluded to star mass and age. Star-forming processes in interstellar clouds as well as stellar burning processes are illustrated. The changes occurring in a star due to the depletion of the nuclear energy reserve are described. In this frame the phenomena of planetary nebulae, supernovae, pulsars, neutron stars as well as of black holes are explained

  8. MAGNETIC FIELDS OF STARS

    OpenAIRE

    Bychkov, V. D.; Bychkova, L. V.; Madej, J.

    2008-01-01

    Now it is known about 1212 stars of the main sequence and giants (from them 610 stars - it is chemically peculiarity (CP) stars) for which direct measurements of magnetic fields were spent (Bychkov et al.,2008). Let's consider, what representations were generated about magnetic fields (MT) of stars on the basis of available observations data.

  9. 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

  10. Symbiotic stars

    Science.gov (United States)

    Kafatos, M.; Michalitsianos, A. G.

    1984-01-01

    The physical characteristics of symbiotic star systems are discussed, based on a review of recent observational data. A model of a symbiotic star system is presented which illustrates how a cool red-giant star is embedded in a nebula whose atoms are ionized by the energetic radiation from its hot compact companion. UV outbursts from symbiotic systems are explained by two principal models: an accretion-disk-outburst model which describes how material expelled from the tenuous envelope of the red giant forms an inwardly-spiralling disk around the hot companion, and a thermonuclear-outburst model in which the companion is specifically a white dwarf which superheats the material expelled from the red giant to the point where thermonuclear reactions occur and radiation is emitted. It is suspected that the evolutionary course of binary systems is predetermined by the initial mass and angular momentum of the gas cloud within which binary stars are born. Since red giants and Mira variables are thought to be stars with a mass of one or two solar mass, it is believed that the original cloud from which a symbiotic system is formed can consist of no more than a few solar masses of gas.

  11. Massive stars in galaxies

    International Nuclear Information System (INIS)

    Humphreys, R.M.

    1987-01-01

    The relationship between the morphologic type of a galaxy and the evolution of its massive stars is explored, reviewing observational results for nearby galaxies. The data are presented in diagrams, and it is found that the massive-star populations of most Sc spiral galaxies and irregular galaxies are similar, while those of Sb spirals such as M 31 and M 81 may be affected by morphology (via differences in the initial mass function or star-formation rate). Consideration is also given to the stability-related upper luminosity limit in the H-R diagram of hypergiant stars (attributed to radiation pressure in hot stars and turbulence in cool stars) and the goals of future observation campaigns. 88 references

  12. Um exemplo de análise contrastiva: o grafema r/rr em português e italiano

    Directory of Open Access Journals (Sweden)

    Lúcia Fulgêncio

    2011-10-01

    Full Text Available Neste trabalho é apresentado um exemplo de análise contrastiva entre a língua italiana e o português falado no Brasil, do ponto de vista fonético. Tomam-se os sons grafados ou <rr> e examinam-se as suas possibilidades re realização fonética em cada língua, individualmente, identificando o contexto de produção de cada realização fonológica. Posteriormente, comparam-se os sistemas fonológicos das duas línguas quanto a esse aspecto, indicando os ambientes de simetria ou dissimetria estrutural. A evidência dos ambientes onde ocorre dissimetria na realização de /<rr> pode ser útil para o professor de italiano para brasileiros (ou vice-versa, já que provavelmente esses ambientes constituirão pontos de maior dificuldade na aprendizagem da produção.In questo studio si presenta un essempio di analisi contrastiva a livello fonetico tra la ligua italiana e quella portoghese parlata in Brasile. Per ognuna delle due lingue vengono analizzate le possibilità di realizzazione fonetica dei grafemi o <rr> definendo il contesto di ogni realizzazione fonologica. In seguito sono comparati i sistemi fonologici dell’italiano e del portoghese per quanto concerne il tema proposto, e vengono indicati gli ambienti di simmetria e asimmetria strutturale. Mettere in risalto gli ambienti di asimmetria nella realizzazione di /<rr> può riverlarsi di grande utilità al professore di italiano a brasiliani o viceversa, dato che l’apprendimento dei suoni che ne risulta costituisce, probabilmente, non poca difficoltà.

  13. GMC Collisions as Triggers of Star Formation. III. Density and Magnetically Regulated Star Formation

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Benjamin [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Tan, Jonathan C. [Department of Physics, University of Florida, Gainesville, FL 32611 (United States); Christie, Duncan [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Nakamura, Fumitaka [National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan); Van Loo, Sven [School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom); Collins, David, E-mail: ben.wu@nao.ac.jp [Department of Physics, Florida State University, Tallahassee, FL 32306-4350 (United States)

    2017-06-01

    We study giant molecular cloud (GMC) collisions and their ability to trigger star cluster formation. We further develop our three-dimensional magnetized, turbulent, colliding GMC simulations by implementing star formation subgrid models. Two such models are explored: (1) “Density-Regulated,” i.e., fixed efficiency per free-fall time above a set density threshold and (2) “Magnetically Regulated,” i.e., fixed efficiency per free-fall time in regions that are magnetically supercritical. Variations of parameters associated with these models are also explored. In the non-colliding simulations, the overall level of star formation is sensitive to model parameter choices that relate to effective density thresholds. In the GMC collision simulations, the final star formation rates and efficiencies are relatively independent of these parameters. Between the non-colliding and colliding cases, we compare the morphologies of the resulting star clusters, properties of star-forming gas, time evolution of the star formation rate (SFR), spatial clustering of the stars, and resulting kinematics of the stars in comparison to the natal gas. We find that typical collisions, by creating larger amounts of dense gas, trigger earlier and enhanced star formation, resulting in 10 times higher SFRs and efficiencies. The star clusters formed from GMC collisions show greater spatial substructure and more disturbed kinematics.

  14. An Autonomous Star Identification Algorithm Based on One-Dimensional Vector Pattern for Star Sensors.

    Science.gov (United States)

    Luo, Liyan; Xu, Luping; Zhang, Hua

    2015-07-07

    In order to enhance the robustness and accelerate the recognition speed of star identification, an autonomous star identification algorithm for star sensors is proposed based on the one-dimensional vector pattern (one_DVP). In the proposed algorithm, the space geometry information of the observed stars is used to form the one-dimensional vector pattern of the observed star. The one-dimensional vector pattern of the same observed star remains unchanged when the stellar image rotates, so the problem of star identification is simplified as the comparison of the two feature vectors. The one-dimensional vector pattern is adopted to build the feature vector of the star pattern, which makes it possible to identify the observed stars robustly. The characteristics of the feature vector and the proposed search strategy for the matching pattern make it possible to achieve the recognition result as quickly as possible. The simulation results demonstrate that the proposed algorithm can effectively accelerate the star identification. Moreover, the recognition accuracy and robustness by the proposed algorithm are better than those by the pyramid algorithm, the modified grid algorithm, and the LPT algorithm. The theoretical analysis and experimental results show that the proposed algorithm outperforms the other three star identification algorithms.

  15. Subluminous Wolf-Rayet stars: Observations

    International Nuclear Information System (INIS)

    Heap, S.R.

    1982-01-01

    The author has used the fact that some central stars are WR stars and others are say, O stars, as a focal point for his presentation. In attempting to answer this question he has considered how the properties of WR-type central stars differ from those of O-type stars. The study begins with the classification and calibration of WR spectra, then goes on to the physical properties of WR-type central stars, and at the end returns to the question of what distinguishes a Wolf-Rayet star. The observational data for central stars are neither complete nor precise. Nevertheless, they suggest that what distinguishes a WR central star is not so much its present physical properties (e.g. temperature, gravity), but rather, its fundamental properties (initial and evolutionary history). (Auth.)

  16. 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…

  17. Observing Double Stars

    Science.gov (United States)

    Genet, Russell M.; Fulton, B. J.; Bianco, Federica B.; Martinez, John; Baxter, John; Brewer, Mark; Carro, Joseph; Collins, Sarah; Estrada, Chris; Johnson, Jolyon; Salam, Akash; Wallen, Vera; Warren, Naomi; Smith, Thomas C.; Armstrong, James D.; McGaughey, Steve; Pye, John; Mohanan, Kakkala; Church, Rebecca

    2012-05-01

    Double stars have been systematically observed since William Herschel initiated his program in 1779. In 1803 he reported that, to his surprise, many of the systems he had been observing for a quarter century were gravitationally bound binary stars. In 1830 the first binary orbital solution was obtained, leading eventually to the determination of stellar masses. Double star observations have been a prolific field, with observations and discoveries - often made by students and amateurs - routinely published in a number of specialized journals such as the Journal of Double Star Observations. All published double star observations from Herschel's to the present have been incorporated in the Washington Double Star Catalog. In addition to reviewing the history of visual double stars, we discuss four observational technologies and illustrate these with our own observational results from both California and Hawaii on telescopes ranging from small SCTs to the 2-meter Faulkes Telescope North on Haleakala. Two of these technologies are visual observations aimed primarily at published "hands-on" student science education, and CCD observations of both bright and very faint doubles. The other two are recent technologies that have launched a double star renaissance. These are lucky imaging and speckle interferometry, both of which can use electron-multiplying CCD cameras to allow short (30 ms or less) exposures that are read out at high speed with very low noise. Analysis of thousands of high speed exposures allows normal seeing limitations to be overcome so very close doubles can be accurately measured.

  18. Neutron star natal kicks and the long-term survival of star clusters

    Science.gov (United States)

    Contenta, Filippo; Varri, Anna Lisa; Heggie, Douglas C.

    2015-04-01

    We investigate the dynamical evolution of a star cluster in an external tidal field by using N-body simulations, with focus on the effects of the presence or absence of neutron star natal velocity kicks. We show that, even if neutron stars typically represent less than 2 per cent of the total bound mass of a star cluster, their primordial kinematic properties may affect the lifetime of the system by up to almost a factor of 4. We interpret this result in the light of two known modes of star cluster dissolution, dominated by either early stellar evolution mass-loss or two-body relaxation. The competition between these effects shapes the mass-loss profile of star clusters, which may either dissolve abruptly (`jumping'), in the pre-core-collapse phase, or gradually (`skiing'), after having reached core collapse.

  19. Hyperfast pulsars as the remnants of massive stars ejected from young star clusters

    Science.gov (United States)

    Gvaramadze, Vasilii V.; Gualandris, Alessia; Portegies Zwart, Simon

    2008-04-01

    Recent proper motion and parallax measurements for the pulsar PSR B1508+55 indicate a transverse velocity of ~1100kms-1, which exceeds earlier measurements for any neutron star. The spin-down characteristics of PSR B1508+55 are typical for a non-recycled pulsar, which implies that the velocity of the pulsar cannot have originated from the second supernova disruption of a massive binary system. The high velocity of PSR B1508+55 can be accounted for by assuming that it received a kick at birth or that the neutron star was accelerated after its formation in the supernova explosion. We propose an explanation for the origin of hyperfast neutron stars based on the hypothesis that they could be the remnants of a symmetric supernova explosion of a high-velocity massive star which attained its peculiar velocity (similar to that of the pulsar) in the course of a strong dynamical three- or four-body encounter in the core of dense young star cluster. To check this hypothesis, we investigated three dynamical processes involving close encounters between: (i) two hard massive binaries, (ii) a hard binary and an intermediate-mass black hole (IMBH) and (iii) a single stars and a hard binary IMBH. We find that main-sequence O-type stars cannot be ejected from young massive star clusters with peculiar velocities high enough to explain the origin of hyperfast neutron stars, but lower mass main-sequence stars or the stripped helium cores of massive stars could be accelerated to hypervelocities. Our explanation for the origin of hyperfast pulsars requires a very dense stellar environment of the order of 106- 107starspc-3. Although such high densities may exist during the core collapse of young massive star clusters, we caution that they have never been observed.

  20. 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

  1. A study for providing additional storage spaces to ET-RR-1 spent fuel

    International Nuclear Information System (INIS)

    El-Kady, A.; Ashoub, N.; Saleh, H.G.

    1995-01-01

    The ET-RR-1 reactor spent fuel storage pool is a trapezoidal aluminum tank concrete shield and of capacity 10 m 3 . It can hold up to 60 fuel assemblies. The long operation history of the ET-RR-1 reactor resulted in a partially filled spent fuel storage with the remaining spaces not enough to host a complete load from the reactor. This work have been initiated to evaluate possible alternative solutions for providing additional storage spaces to host the available EK-10 fuel elements after irradiation and any foreseen fuel in case of reactor upgrading. Several alternate solutions have been reviewed and decision on the most suitable one is under study. These studies include criticality calculation of some suggested alternatives like reracking the present spent fuel storage pool and double tiering by the addition of a second level storage rack above the existing rack. The two levels may have different factor. Criticality calculation of the double tiering possible accident was also studied. (author)

  2. Cepheid pulsation theory and multiperiodic cepheid variables

    International Nuclear Information System (INIS)

    Cox, A.N.; Cox, J.P.

    1975-01-01

    In this review of the multiperiodic Cepheid variables, the subject matter is divided into four parts. The first discusses general causes of pulsation of Cepheids and other variable stars, and their locations on the H-R diagram. In the second section, the linear adiabatic and nonadiabatic theory calculation of radial pulsation periods and their application to the problem of masses and double-mode Cepheids are reviewed. Periodic solutions, and their stability, of the nonlinear radial pulsation equations for Cepheids and RR Lyrae stars are considered in the third section. The last section provides the latest results on nonlinear, nonperiodic, radial pulsations for Cepheids and RR Lyrae stars. (BJG)

  3. Ultracompact X-ray binary stars

    NARCIS (Netherlands)

    Haaften, L.M. van

    2013-01-01

    Ultracompact X-ray binary stars usually consist of a neutron star and a white dwarf, two stars bound together by their strong gravity and orbiting each other very rapidly, completing one orbit in less than one hour. Neutron stars are extremely compact remnants of the collapsed cores of massive stars

  4. Star Masses and Star-Planet Distances for Earth-like Habitability.

    Science.gov (United States)

    Waltham, David

    2017-01-01

    This paper presents statistical estimates for the location and duration of habitable zones (HZs) around stars of different mass. The approach is based upon the assumption that Earth's location, and the Sun's mass, should not be highly atypical of inhabited planets. The results support climate-model-based estimates for the location of the Sun's HZ except models giving a present-day outer-edge beyond 1.64 AU. The statistical approach also demonstrates that there is a habitability issue for stars smaller than 0.65 solar masses since, otherwise, Earth would be an extremely atypical inhabited world. It is difficult to remove this anomaly using the assumption that poor habitability of planets orbiting low-mass stars results from unfavorable radiation regimes either before, or after, their stars enter the main sequence. However, the anomaly is well explained if poor habitability results from tidal locking of planets in the HZs of small stars. The expected host-star mass for planets with intelligent life then has a 95% confidence range of 0.78 M ⊙ planets with at least simple life is 0.57 M ⊙  < M < 1.64 M ⊙ . Key Words: Habitability-Habitable zone-Anthropic-Red dwarfs-Initial mass function. Astrobiology 17, 61-77.

  5. X-ray sources in stars formation areas: T Tauri stars and proto-stars in the rho Ophiuchi dark cloud

    International Nuclear Information System (INIS)

    Grosso, Nicolas

    1999-01-01

    This thesis studies from large to small scales, X-ray sources in the rho Ophiuchi dark cloud. After some background on the formation of the low-mass young stars (Chapter 1), Chapter 2 takes an interest in the T Tauri star population. Chapter 3 tackles the search of the magnetic activity at the younger stage of protostar, presenting a powerful X-ray emission from an IR protostar, called YLW15, during a flare, and a quasi-periodic flare of the same source; as well as a new detection of another IR protostar in the ROSAT archives. It ends with a review of protostar detections. Some IR protostar flares show a very long increasing phase. Chapter 4 links this behaviour with a modulation by the central star rotation. The standard model of jet emission assumes that the central star rotates at the same speed that the inner edge of its accretion disk. This chapter shows that the observation of the YLW15 quasi-periodic flare suggests rather that the forming star rotates faster than its accretion disk, at the break up limit. The synchronism with the accretion disk, observed on T Tauri stars, must be reach progressively by magnetic breaking during the IR protostar stage, and more or less rapidly depending on the forming star mass. Recent studies have shown that T Tauri star X-ray emission could ionize the circumstellar disk, and play a role in the instability development, as well as stimulate the accretion. The protostar X-ray emission might be higher than the T Tauri star one, Chapter 5 presents a millimetric interferometric observation dedicated to measure this effect on YLW15. Finally, Chapter 6 reassembles conclusions and perspectives of this work. (author) [fr

  6. THE GALACTIC O-STAR SPECTROSCOPIC SURVEY (GOSSS). II. BRIGHT SOUTHERN STARS

    International Nuclear Information System (INIS)

    Sota, A.; Apellániz, J. Maíz; Alfaro, E. J.; Morrell, N. I.; Barbá, R. H.; Arias, J. I.; Walborn, N. R.; Gamen, R. C.

    2014-01-01

    We present the second installment of GOSSS, a massive spectroscopic survey of Galactic O stars, based on new homogeneous, high signal-to-noise ratio, R ∼ 2500 digital observations from both hemispheres selected from the Galactic O-Star Catalog (GOSC). In this paper we include bright stars and other objects drawn mostly from the first version of GOSC, all of them south of δ = –20°, for a total number of 258 O stars. We also revise the northern sample of Paper I to provide the full list of spectroscopically classified Galactic O stars complete to B = 8, bringing the total number of published GOSSS stars to 448. Extensive sequences of exceptional objects are given, including the early Of/WN, O Iafpe, Ofc, ON/OC, Onfp, Of?p, and Oe types, as well as double/triple-lined spectroscopic binaries. The new spectral subtype O9.2 is also discussed. The magnitude and spatial distributions of the observed sample are analyzed. We also present new results from OWN, a multi-epoch high-resolution spectroscopic survey coordinated with GOSSS that is assembling the largest sample of Galactic spectroscopic massive binaries ever attained. The OWN data combined with additional information on spectroscopic and visual binaries from the literature indicate that only a very small fraction (if any) of the stars with masses above 15-20 M ☉ are born as single systems. In the future we will publish the rest of the GOSSS survey, which is expected to include over 1000 Galactic O stars

  7. Lithium in the barium stars

    International Nuclear Information System (INIS)

    Pinsonneault, M.H.; Sneden, C.

    1984-01-01

    New high-resolution spectra of the lithium resonance doublet have provided lithium abundances or upper limits for 26 classical and mild barium stars. The lithium lines always are present in the classical barium stars. Lithium abundances in these stars obey a trend with stellar masses consistent with that previously derived for ordinary K giants. This supports the notion that classical barium stars are post-core-He-flash or core-He-burning stars. Lithium contents in the mild barium stars, however, often are much smaller than those of the classical barium stars sometimes only upper limits may be determined. The cause for this difference is not easily understood, but may be related to more extensive mass loss by the mild barium stars. 45 references

  8. Rodent Research-1 (RR1) NASA Validation Flight: Mouse soleus muscle transcriptomic and epigenomic data

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA s Rodent Research (RR) project is playing a critical role in advancing biomedical research on the physiological effects of space environments. Due to the...

  9. Rodent Research-1 (RR1) NASA Validation Flight: Mouse kidney transcriptomic proteomic and epigenomic data

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA s Rodent Research (RR) project is playing a critical role in advancing biomedical research on the physiological effects of space environments. Due to the...

  10. Improved autonomous star identification algorithm

    International Nuclear Information System (INIS)

    Luo Li-Yan; Xu Lu-Ping; Zhang Hua; Sun Jing-Rong

    2015-01-01

    The log–polar transform (LPT) is introduced into the star identification because of its rotation invariance. An improved autonomous star identification algorithm is proposed in this paper to avoid the circular shift of the feature vector and to reduce the time consumed in the star identification algorithm using LPT. In the proposed algorithm, the star pattern of the same navigation star remains unchanged when the stellar image is rotated, which makes it able to reduce the star identification time. The logarithmic values of the plane distances between the navigation and its neighbor stars are adopted to structure the feature vector of the navigation star, which enhances the robustness of star identification. In addition, some efforts are made to make it able to find the identification result with fewer comparisons, instead of searching the whole feature database. The simulation results demonstrate that the proposed algorithm can effectively accelerate the star identification. Moreover, the recognition rate and robustness by the proposed algorithm are better than those by the LPT algorithm and the modified grid algorithm. (paper)

  11. 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....

  12. Relationship among RR interval, optimal reconstruction phase, temporal resolution, and image quality of end-systolic reconstruction of coronary CT angiography in patients with high heart rates. In search of the optimal acquisition protocol

    International Nuclear Information System (INIS)

    Sano, Tomonari; Matsutani, Hideyuki; Kondo, Takeshi; Fujimoto, Shinichiro; Sekine, Takako; Arai, Takehiro; Morita, Hitomi; Takase, Shinichi

    2011-01-01

    The purpose of this study is to elucidate the relationship among RR interval (RR), the optimal reconstruction phase, and adequate temporal resolution (TR) to obtain coronary CT angiography images of acceptable quality using 64-multi detector-row CT (MDCT) (Aquilion 64) of end-systolic reconstruction in 407 patients with high heart rates. Image quality was classified into 3 groups [rank A (excellent): 161, rank B (acceptable): 207, and rank C (unacceptable): 39 patients]. The optimal absolute phase (OAP) significantly correlated with RR [OAP (ms)=119-0.286 RR (ms), r=0.832, p<0.0001], and the optimal relative phase (ORP) also significantly correlated with RR [ORP (%)=62-0.023 RR (ms), r=0.656, p<0.0001], and the correlation coefficient of OAP was significantly (p<0.0001) higher than that of ORP. The OAP range (±2 standard deviation (SD)) in which it is highly possible to get a static image was from [119-0.286 RR (ms)-46] to [119-0.286 RR (ms)+46]. The TR was significantly different among ranks A (97±22 ms), B (111±31 ms) and C (135±34 ms). The TR significantly correlated with RR in ranks A (TR=-16+0.149 RR, r=0.767, p<0.0001), B (TR=-15+0.166 RR, r=0.646, p<0.0001), and C (TR=52+0.117 RR, r=0.425, p=0.0069). Rank C was distinguished from ranks A or B by linear discriminate analysis (TR=-46+0.21 RR), and the discriminate rate was 82.6%. In conclusion, both the OAP and adequate TR depend on RR, and the OAP range (±2 SD) can be calculated using the formula [119-0.286 RR (ms)-46] to [119-0.286 RR (ms) +46], and an adequate TR value would be less than (-46+0.21 RR). (author)

  13. Thermal neutron flux distribution in ET-RR-2 reactor thermal column

    Directory of Open Access Journals (Sweden)

    Imam Mahmoud M.

    2002-01-01

    Full Text Available The thermal column in the ET-RR-2 reactor is intended to promote a thermal neutron field of high intensity and purity to be used for following tasks: (a to provide a thermal neutron flux in the neutron transmutation silicon doping, (b to provide a thermal flux in the neutron activation analysis position, and (c to provide a thermal neutron flux of high intensity to the head of one of the beam tubes leading to the room specified for boron thermal neutron capture therapy. It was, therefore, necessary to determine the thermal neutron flux at above mentioned positions. In the present work, the neutron flux in the ET-RR-2 reactor system was calculated by applying the three dimensional diffusion depletion code TRITON. According to these calculations, the reactor system is composed of the core, surrounding external irradiation grid, beryllium block, thermal column and the water reflector in the reactor tank next to the tank wall. As a result of these calculations, the thermal neutron fluxes within the thermal column and at irradiation positions within the thermal column were obtained. Apart from this, the burn up results for the start up core calculated according to the TRITION code were compared with those given by the reactor designer.

  14. 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

  15. Multipurpose RTOF Fourier diffractometer at the ET-RR-1 reactor

    International Nuclear Information System (INIS)

    Maayouf, R.M.A.; Tiitta, A.T.

    1993-09-01

    The present work represents a further study of the basic RTOF Fourier multipurpose diffractometer, to start with, at the ET-RR-1 reactor. The functions of the suggested arrangement are thoroughly discussed and the possibilities if its expansion are also assessed. The flexibility of the arrangement allows its further expansion both for stress measurement at 90 deg. scattering angle with two detector banks at opposite sides of the incident beam and for operation in the transmission diffraction mode. (orig.). (19 refs., 10 figs., 1 tab.)

  16. How the First Stars Regulated Star Formation. II. Enrichment by Nearby Supernovae

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Ke-Jung [Division of Theoretical Astronomy, National Astronomical Observatory of Japan, Tokyo 181-8588 (Japan); Whalen, Daniel J. [Institute of Cosmology and Gravitation, Portsmouth University, Portsmouth (United Kingdom); Wollenberg, Katharina M. J.; Glover, Simon C. O.; Klessen, Ralf S., E-mail: ken.chen@nao.ac.jp [Zentrum für Astronomie, Institut für Theoretische Astrophysik, Universität Heidelberg (Germany)

    2017-08-01

    Metals from Population III (Pop III) supernovae led to the formation of less massive Pop II stars in the early universe, altering the course of evolution of primeval galaxies and cosmological reionization. There are a variety of scenarios in which heavy elements from the first supernovae were taken up into second-generation stars, but cosmological simulations only model them on the largest scales. We present small-scale, high-resolution simulations of the chemical enrichment of a primordial halo by a nearby supernova after partial evaporation by the progenitor star. We find that ejecta from the explosion crash into and mix violently with ablative flows driven off the halo by the star, creating dense, enriched clumps capable of collapsing into Pop II stars. Metals may mix less efficiently with the partially exposed core of the halo, so it might form either Pop III or Pop II stars. Both Pop II and III stars may thus form after the collision if the ejecta do not strip all the gas from the halo. The partial evaporation of the halo prior to the explosion is crucial to its later enrichment by the supernova.

  17. Stability of UV exposed RR-P3BT films by spectroscopic ellipsometry

    International Nuclear Information System (INIS)

    Diware, Mangesh S.; Byun, J. S.; Hwang, S. Y.; Kim, T. J.; Kim, Y. D.

    2013-01-01

    Stability of regioregular poly(3-butylthiophene) (RR-P3BT) films under irradiation of ultra-violet (UV) light has been studied by spectroscopic ellipsometry at room temperature. Consistent decrease in dielectric function with UV exposure time showed the degree of degradation of polymer. This work suggests that, protective methods are mandatory to use this kind of material in optical devices.

  18. Mechanism of mRNA-STAR domain interaction: Molecular dynamics simulations of Mammalian Quaking STAR protein.

    Science.gov (United States)

    Sharma, Monika; Anirudh, C R

    2017-10-03

    STAR proteins are evolutionary conserved mRNA-binding proteins that post-transcriptionally regulate gene expression at all stages of RNA metabolism. These proteins possess conserved STAR domain that recognizes identical RNA regulatory elements as YUAAY. Recently reported crystal structures show that STAR domain is composed of N-terminal QUA1, K-homology domain (KH) and C-terminal QUA2, and mRNA binding is mediated by KH-QUA2 domain. Here, we present simulation studies done to investigate binding of mRNA to STAR protein, mammalian Quaking protein (QKI). We carried out conventional MD simulations of STAR domain in presence and absence of mRNA, and studied the impact of mRNA on the stability, dynamics and underlying allosteric mechanism of STAR domain. Our unbiased simulations results show that presence of mRNA stabilizes the overall STAR domain by reducing the structural deviations, correlating the 'within-domain' motions, and maintaining the native contacts information. Absence of mRNA not only influenced the essential modes of motion of STAR domain, but also affected the connectivity of networks within STAR domain. We further explored the dissociation of mRNA from STAR domain using umbrella sampling simulations, and the results suggest that mRNA binding to STAR domain occurs in multi-step: first conformational selection of mRNA backbone conformations, followed by induced fit mechanism as nucleobases interact with STAR domain.

  19. Rodent Research-1 (RR1) NASA Validation Flight: Mouse liver transcriptomic proteomic and epigenomic data

    Data.gov (United States)

    National Aeronautics and Space Administration — RR-1 is a validation flight to evaluate the hardware operational and science capabilities of the Rodent Research Project on the ISS. RNA DNA and protein were...

  20. 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.

  1. Spectroscopic Comparison of Metal-rich RRab Stars of the Galactic Field with their Metal-poor Counterparts

    Energy Technology Data Exchange (ETDEWEB)

    Chadid, Merieme [Université Nice Sophia–Antipolis, Observatoire de la Côte dAzur, UMR 7293, Parc Valrose, F-06108, Nice Cedex 02 (France); Sneden, Christopher [Department of Astronomy and McDonald Observatory, The University of Texas, Austin, TX 78712 (United States); Preston, George W., E-mail: chadid@unice.fr, E-mail: chris@verdi.as.utexas.edu, E-mail: gwp@obs.carnegiescience.edu [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2017-02-01

    We investigate atmospheric properties of 35 stable RRab stars that possess the full ranges of period, light amplitude, and metal abundance found in Galactic RR Lyrae stars. Our results are derived from several thousand echelle spectra obtained over several years with the du Pont telescope of Las Campanas Observatory. Radial velocities of metal lines and the H α line were used to construct curves of radial velocity versus pulsation phase. From these we estimated radial velocity amplitudes for metal lines (formed near the photosphere) and H α Doppler cores (formed at small optical depths). We also measured H α emission fluxes when they appear during primary light rises. Spectra shifted to rest wavelengths, binned into small phase intervals, and co-added were used to perform model atmospheric and abundance analyses. The derived metallicities and those of some previous spectroscopic surveys were combined to produce a new calibration of the Layden abundance scale. We then divided our RRab sample into metal-rich (disk) and metal-poor (halo) groups at [Fe/H] = −1.0; the atmospheres of RRab families, so defined, differ with respect to (a) peak strength of H α emission flux, (b) H α radial velocity amplitude, (c) dynamical gravity, (d) stellar radius variation, (e) secondary acceleration during the photometric bump that precedes minimum light, and (f) duration of H α line-doubling. We also detected H α line-doubling during the “bump” in the metal-poor family, but not in the metal-rich one. Although all RRab probably are core helium-burning horizontal branch stars, the metal-rich group appears to be a species sui generis.

  2. Strangeon and Strangeon Star

    Science.gov (United States)

    Xiaoyu, Lai; Renxin, Xu

    2017-06-01

    The nature of pulsar-like compact stars is essentially a central question of the fundamental strong interaction (explained in quantum chromo-dynamics) at low energy scale, the solution of which still remains a challenge though tremendous efforts have been tried. This kind of compact objects could actually be strange quark stars if strange quark matter in bulk may constitute the true ground state of the strong-interaction matter rather than 56Fe (the so-called Witten’s conjecture). From astrophysical points of view, however, it is proposed that strange cluster matter could be absolutely stable and thus those compact stars could be strange cluster stars in fact. This proposal could be regarded as a general Witten’s conjecture: strange matter in bulk could be absolutely stable, in which quarks are either free (for strange quark matter) or localized (for strange cluster matter). Strange cluster with three-light-flavor symmetry is renamed strangeon, being coined by combining “strange nucleon” for the sake of simplicity. A strangeon star can then be thought as a 3-flavored gigantic nucleus, and strangeons are its constituent as an analogy of nucleons which are the constituent of a normal (micro) nucleus. The observational consequences of strangeon stars show that different manifestations of pulsarlike compact stars could be understood in the regime of strangeon stars, and we are expecting more evidence for strangeon star by advanced facilities (e.g., FAST, SKA, and eXTP).

  3. 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.

  4. 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....

  5. Four new Delta Scuti stars

    Science.gov (United States)

    Schutt, R. L.

    1991-01-01

    Four new Delta Scuti stars are reported. Power, modified into amplitude, spectra, and light curves are used to determine periodicities. A complete frequency analysis is not performed due to the lack of a sufficient time base in the data. These new variables help verify the many predictions that Delta Scuti stars probably exist in prolific numbers as small amplitude variables. Two of these stars, HR 4344 and HD 107513, are possibly Am stars. If so, they are among the minority of variable stars which are also Am stars.

  6. Design and DSP implementation of star image acquisition and star point fast acquiring and tracking

    Science.gov (United States)

    Zhou, Guohui; Wang, Xiaodong; Hao, Zhihang

    2006-02-01

    Star sensor is a special high accuracy photoelectric sensor. Attitude acquisition time is an important function index of star sensor. In this paper, the design target is to acquire 10 samples per second dynamic performance. On the basis of analyzing CCD signals timing and star image processing, a new design and a special parallel architecture for improving star image processing are presented in this paper. In the design, the operation moving the data in expanded windows including the star to the on-chip memory of DSP is arranged in the invalid period of CCD frame signal. During the CCD saving the star image to memory, DSP processes the data in the on-chip memory. This parallelism greatly improves the efficiency of processing. The scheme proposed here results in enormous savings of memory normally required. In the scheme, DSP HOLD mode and CPLD technology are used to make a shared memory between CCD and DSP. The efficiency of processing is discussed in numerical tests. Only in 3.5ms is acquired the five lightest stars in the star acquisition stage. In 43us, the data in five expanded windows including stars are moved into the internal memory of DSP, and in 1.6ms, five star coordinates are achieved in the star tracking stage.

  7. Orbiting radiation stars

    International Nuclear Information System (INIS)

    Foster, Dean P; Langford, John; Perez-Giz, Gabe

    2016-01-01

    We study a spherically symmetric solution to the Einstein equations in which the source, which we call an orbiting radiation star (OR-star), is a compact object consisting of freely falling null particles. The solution avoids quantum scale regimes and hence neither relies upon nor ignores the interaction of quantum mechanics and gravitation. The OR-star spacetime exhibits a deep gravitational well yet remains singularity free. In fact, it is geometrically flat in the vicinity of the origin, with the flat region being of any desirable scale. The solution is observationally distinct from a black hole because a photon from infinity aimed at an OR-star escapes to infinity with a time delay. (paper)

  8. Accreting neutron stars, black holes, and degenerate dwarf stars.

    Science.gov (United States)

    Pines, D

    1980-02-08

    During the past 8 years, extended temporal and broadband spectroscopic studies carried out by x-ray astronomical satellites have led to the identification of specific compact x-ray sources as accreting neutron stars, black holes, and degenerate dwarf stars in close binary systems. Such sources provide a unique opportunity to study matter under extreme conditions not accessible in the terrestrial laboratory. Quantitative theoretical models have been developed which demonstrate that detailed studies of these sources will lead to a greatly increased understanding of dense and superdense hadron matter, hadron superfluidity, high-temperature plasma in superstrong magnetic fields, and physical processes in strong gravitational fields. Through a combination of theory and observation such studies will make possible the determination of the mass, radius, magnetic field, and structure of neutron stars and degenerate dwarf stars and the identification of further candidate black holes, and will contribute appreciably to our understanding of the physics of accretion by compact astronomical objects.

  9. Ageing problems and renovation programme of ET-RR-1 reactor

    International Nuclear Information System (INIS)

    Khattab, M.S.; Sultan, M.A.

    1995-01-01

    Based on Practical Experience gained from interfacing ageing systems in addition to operating new systems, current problems could be deduced whenever in-service inspection are carried out. This paper summarizes the in-service inspection made, and the proposed programme of rehabilitation of mechanical system in the ET-RR-1 research reactor at Inshass. Exchangeable experience in solving common problems in similar reactors play an important role in the effectiveness of such rehabilitation programme. The paper summarizes also the modernization of control, measuring and radiation monitoring system already carried out at the reactor. (orig.)

  10. Search for OB stars running away from young star clusters. I. NGC 6611

    Science.gov (United States)

    Gvaramadze, V. V.; Bomans, D. J.

    2008-11-01

    N-body simulations have shown that the dynamical decay of the young (~1 Myr) Orion Nebula cluster could be responsible for the loss of at least half of its initial content of OB stars. This result suggests that other young stellar systems could also lose a significant fraction of their massive stars at the very beginning of their evolution. To confirm this expectation, we used the Mid-Infrared Galactic Plane Survey (completed by the Midcourse Space Experiment satellite) to search for bow shocks around a number of young (⪉several Myr) clusters and OB associations. We discovered dozens of bow shocks generated by OB stars running away from these stellar systems, supporting the idea of significant dynamical loss of OB stars. In this paper, we report the discovery of three bow shocks produced by O-type stars ejected from the open cluster NGC 6611 (M16). One of the bow shocks is associated with the O9.5Iab star HD165319, which was suggested to be one of “the best examples for isolated Galactic high-mass star formation” (de Wit et al. 2005, A&A, 437, 247). Possible implications of our results for the origin of field OB stars are discussed.

  11. Interval ridge regression (iRR) as a fast and robust method for quantitative prediction and variable selection applied to edible oil adulteration.

    Science.gov (United States)

    Jović, Ozren; Smrečki, Neven; Popović, Zora

    2016-04-01

    A novel quantitative prediction and variable selection method called interval ridge regression (iRR) is studied in this work. The method is performed on six data sets of FTIR, two data sets of UV-vis and one data set of DSC. The obtained results show that models built with ridge regression on optimal variables selected with iRR significantly outperfom models built with ridge regression on all variables in both calibration (6 out of 9 cases) and validation (2 out of 9 cases). In this study, iRR is also compared with interval partial least squares regression (iPLS). iRR outperfomed iPLS in validation (insignificantly in 6 out of 9 cases and significantly in one out of 9 cases for poil, a well known health beneficial nutrient, is studied in this work by mixing it with cheap and widely used oils such as soybean (So) oil, rapeseed (R) oil and sunflower (Su) oil. Binary mixture sets of hempseed oil with these three oils (HSo, HR and HSu) and a ternary mixture set of H oil, R oil and Su oil (HRSu) were considered. The obtained accuracy indicates that using iRR on FTIR and UV-vis data, each particular oil can be very successfully quantified (in all 8 cases RMSEPoil (R(2)>0.99). Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Spectrophotometry of Symbiotic Stars (Abstract)

    Science.gov (United States)

    Boyd, D.

    2017-12-01

    (Abstract only) 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 ionizes 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.

  13. BINARY DISRUPTION BY MASSIVE BLACK HOLES: HYPERVELOCITY STARS, S STARS, AND TIDAL DISRUPTION EVENTS

    Energy Technology Data Exchange (ETDEWEB)

    Bromley, Benjamin C. [Department of Physics and Astronomy, University of Utah, 115 S 1400 E, Rm 201, Salt Lake City, UT 84112 (United States); Kenyon, Scott J.; Geller, Margaret J.; Brown, Warren R., E-mail: bromley@physics.utah.edu, E-mail: skenyon@cfa.harvard.edu, E-mail: mgeller@cfa.harvard.edu, E-mail: wbrown@cfa.harvard.edu [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)

    2012-04-20

    We examine whether disrupted binary stars can fuel black hole growth. In this mechanism, tidal disruption produces a single hypervelocity star (HVS) ejected at high velocity and a former companion star bound to the black hole. After a cluster of bound stars forms, orbital diffusion allows the black hole to accrete stars by tidal disruption at a rate comparable to the capture rate. In the Milky Way, HVSs and the S star cluster imply similar rates of 10{sup -5} to 10{sup -3} yr{sup -1} for binary disruption. These rates are consistent with estimates for the tidal disruption rate in nearby galaxies and imply significant black hole growth from disrupted binaries on 10 Gyr timescales.

  14. Fast pulsars, strange stars

    International Nuclear Information System (INIS)

    Glendenning, N.K.

    1990-02-01

    The initial motivation for this work was the reported discovery in January 1989 of a 1/2 millisecond pulsar in the remnant of the spectacular supernova, 1987A. The status of this discovery has come into grave doubt as of data taken by the same group in February, 1990. At this time we must consider that the millisecond signal does not belong to the pulsar. The existence of a neutron star in remnant of the supernova is suspected because of recent observations on the light curve of the remnant, and of course by the neutrino burst that announced the supernova. However its frequency is unknown. I can make a strong case that a pulsar rotation period of about 1 ms divides those that can be understood quite comfortably as neutron stars, and those that cannot. What we will soon learn is whether there is an invisible boundary below which pulsar periods do not fall, in which case, all are presumable neutron stars, or whether there exist sub- millisecond pulsars, which almost certainly cannot be neutron stars. Their most plausible structure is that of a self-bound star, a strange-quark-matter star. The existence of such stars would imply that the ground state of the strong interaction is not, as we usually assume, hadronic matter, but rather strange quark matter. Let us look respectively at stars that are bound only by gravity, and hypothetical stars that are self-bound, for which gravity is so to speak, icing on the cake

  15. Bump masses for BL Her stars

    International Nuclear Information System (INIS)

    Davis, C.G.

    1982-01-01

    The masses of classical Cepheids can be determined by using the phase of the Hertzsprung bump on the light or velocity curve, Cox-Stewart opacities, and nonlinear pulsation theory. The fact that these bump masses are some 60% lower than the evolutionary masses raises some questions about this approach. In support of our method, we calculate the light curve for BL Her, a population II Cepheid, with an observed bump on the declining portion of its light curve. The nonlinear hydrodynamic model we use (Davis and Davison - 1978) resolves the light curve by dynamic zoning and allows us the opportunity to make a direct comparison of the calculated light curve to the observations, using a prescribed mass, luminosity and effective temperature. The parameters for BL Her are from a linear model (Hodson, Cox, and King - 1982) that has nearly the correct period (1./sup d/2) and the correct period ratio from resonance theory (π 2 /π 0 = 0.53) for a bump to appear on the declining portion of the light curve as observed. These parameters are: M = 0.55 M, L = 95.0 L, and T/sub eff/ = 6500 K. This mass is near the evolutionary mass as described by Schwartzschild and Haerm (1970). The model results agree well with the observations and the color-T/sub eff/ relation has the same slope as that observed for RR Lyrae stars by the Oke, Giver and Searle (1965) relationship

  16. Wolf-Rayet Stars

    Science.gov (United States)

    Hamann, Wolf-Rainer; Sander, Andreas; Todt, Helge

    Nearly 150 years ago, the French astronomers Charles Wolf and Georges Rayet described stars with very conspicuous spectra that are dominated by bright and broad emission lines. Meanwhile termed Wolf-Rayet Stars after their discoverers, those objects turned out to represent important stages in the life of massive stars. As the first conference in a long time that was specifically dedicated to Wolf-Rayet stars, an international workshop was held in Potsdam, Germany, from 1.-5. June 2015. About 100 participants, comprising most of the leading experts in the field as well as as many young scientists, gathered for one week of extensive scientific exchange and discussions. Considerable progress has been reported throughout, e.g. on finding such stars, modeling and analyzing their spectra, understanding their evolutionary context, and studying their circumstellar nebulae. While some major questions regarding Wolf-Rayet stars still remain open 150 years after their discovery, it is clear today that these objects are not just interesting stars as such, but also keystones in the evolution of galaxies. These proceedings summarize the talks and posters presented at the Potsdam Wolf-Rayet workshop. Moreover, they also include the questions, comments, and discussions emerging after each talk, thereby giving a rare overview not only about the research, but also about the current debates and unknowns in the field. The Scientific Organizing Committee (SOC) included Alceste Bonanos (Athens), Paul Crowther (Sheffield), John Eldridge (Auckland), Wolf-Rainer Hamann (Potsdam, Chair), John Hillier (Pittsburgh), Claus Leitherer (Baltimore), Philip Massey (Flagstaff), George Meynet (Geneva), Tony Moffat (Montreal), Nicole St-Louis (Montreal), and Dany Vanbeveren (Brussels).

  17. Low-mass stars with mass loss and low-luminosity carbon star formation

    International Nuclear Information System (INIS)

    Boothroyd, A.I.

    1987-01-01

    The effects of large carbon enrichments in static stellar envelopes were investigated, using new Los Alamos opacities (including low-temperature carbon and molecular opacities) and including carbon ionizations. To search for the production of low-mass,low-luminosity carbon stars, detailed stellar evolutionary computations were carried out for a grid of low-mass stars of two different metallicities. The stars were evolved from the main sequence through all intermediate stages and through helium-shell flashes on the asymptotic giant branch. The effects of the latest nuclear reaction rates, the new Los Alamos opacities, Reimers-type wind mass loss, and detailed treatment of convection and semi-convection were investigated. Two low-luminosity carbon stars were achieved, in excellent agreement with observations. Conditions favoring dredge-up (and thus carbon-star production) include a reasonably large convective mixing length, low metallicity, relatively large envelope mass, and high flash strength. Mass loss was of major importance, tending to oppose dredge-up; the total mass-loss amounts inferred from observations suffice to prevent formation of high-mass, high-luminosity carbon stars

  18. Spectroscopic survey of Kepler stars - II. FIES/NOT observations of A- and F-type stars

    Science.gov (United States)

    Niemczura, E.; Polińska, M.; Murphy, S. J.; Smalley, B.; Kołaczkowski, Z.; Jessen-Hansen, J.; Uytterhoeven, K.; Lykke, J. M.; Triviño Hage, A.; Michalska, G.

    2017-09-01

    We have analysed high-resolution spectra of 28 A and 22 F stars in the Kepler field, observed using the Fibre-Fed Échelle Spectrograph at the Nordic Optical Telescope. We provide spectral types, atmospheric parameters and chemical abundances for 50 stars. Balmer, Fe I and Fe II lines were used to derive effective temperatures, surface gravities and microturbulent velocities. We determined chemical abundances and projected rotational velocities using a spectrum synthesis technique. Effective temperatures calculated by spectral energy distribution fitting are in good agreement with those determined from the spectral line analysis. The stars analysed include chemically peculiar stars of the Am and λ Boo types, as well as stars with approximately solar chemical abundances. The wide distribution of projected rotational velocity, vsin I, is typical for A and F stars. The microturbulence velocities obtained are typical for stars in the observed temperature and surface gravity ranges. Moreover, we affirm the results of Niemczura et al. that Am stars do not have systematically higher microturbulent velocities than normal stars of the same temperature.

  19. Another Possibility for Boyajian's Star

    Science.gov (United States)

    Kohler, Susanna

    2017-07-01

    The unusual light curve of the star KIC 8462852, also known as Tabbys star or Boyajians star, has puzzled us since its discovery last year. A new study now explores whether the stars missing flux is due to internal blockage rather than something outside of the star.Mysterious DipsMost explanations for the flux dips of Boyajians star rely on external factors, like this illustrated swarm of comets. [NASA/JPL-Caltech]Boyajians star shows unusual episodes of dimming in its light curve by as much as 20%, each lasting a few to tens of days and separated by periods of typically hundreds of days. In addition, archival observations show that it has gradually faded by roughly 15% over the span of the last hundred years. What could be causing both the sporadic flux dips and the long-term fading of this odd star?Explanations thus far have varied from mundane to extreme. Alien megastructures, pieces of smashed planets or comets orbiting the star, and intervening interstellar medium have all been proposed as possible explanations but these require some object external to the star. A new study by researcher Peter Foukal proposes an alternative: what if the source of the flux obstruction is the star itself?Analogy to the SunDecades ago, researchers discovered that our own stars total flux isnt as constant as we thought. When magnetic dark spots on the Suns surface block the heat transport, the Suns luminosity dips slightly. The diverted heat is redistributed in the Suns interior, becoming stored as a very small global heating and expansion of the convective envelope. When the blocking starspot is removed, the Sun appears slightly brighter than it did originally. Its luminosity then gradually relaxes, decaying back to its original value.Model of a stars flux after a 1,000-km starspot is inserted at time t = 0 and removed at time t = ts at a depth of 10,000 km in the convective zone. The stars luminosity dips, then becomes brighter than originally, and then gradually decays. [Foukal

  20. Stability of boson stars

    International Nuclear Information System (INIS)

    Gleiser, M.

    1988-01-01

    Boson stars are gravitationally bound, spherically symmetric equilibrium configurations of cold, free, or interacting complex scalar fields phi. As these equilibrium configurations naturally present local anisotropy, it is sensible to expect departures from the well-known stability criteria for fluid stars. With this in mind, I investigate the dynamical instability of boson stars against charge-conserving, small radial perturbations. Following the method developed by Chandrasekhar, a variational base for determining the eigenfrequencies of the perturbations is found. This approach allows one to find numerically an upper bound for the central density where dynamical instability occurs. As applications of the formalism, I study the stability of equilibrium configurations obtained both for the free and for the self-interacting [with V(phi) = (λ/4)chemical bondphichemical bond 4 ] massive scalar field phi. Instabilities are found to occur not for the critical central density as in fluid stars but for central densities considerably higher. The departure from the results for fluid stars is sensitive to the coupling λ; the higher the value of λ, the more the stability properties of boson stars approach those of a fluid star. These results are linked to the fractional anisotropy at the radius of the configuration

  1. Strange-quark-matter stars

    International Nuclear Information System (INIS)

    Glendenning, N.K.

    1989-11-01

    We investigate the implications of rapid rotation corresponding to the frequency of the new pulsar reported in the supernovae remnant SN1987A. It places very stringent conditions on the equation of state if the star is assumed to be bound by gravity alone. We find that the central energy density of the star must be greater than 13 times that of nuclear density to be stable against the most optimistic estimate of general relativistic instabilities. This is too high for the matter to consist of individual hadrons. We conclude that it is implausible that the newly discovered pulsar, if its half-millisecond signals are attributable to rotation, is a neutron star. We show that it can be a strange quark star, and that the entire family of strange stars can sustain high rotation if strange matter is stable at an energy density exceeding about 5.4 times that of nuclear matter. We discuss the conversion of a neutron star to strange star, the possible existence of a crust of heavy ions held in suspension by centrifugal and electric forces, the cooling and other features. 34 refs., 10 figs., 1 tab

  2. VLA observations of dwarf M flare stars and magnetic stars

    Science.gov (United States)

    Willson, R. F.; Lang, K. R.; Foster, P.

    1988-01-01

    The VLA has been used to search for 6 cm emission from 16 nearby dwarf M stars, leading to the detection of only one of them - Gliese 735. The dwarf M flare stars AD Leonis and YZ Canis Minoris were also monitored at 6 cm and 20 cm wavelength in order to study variability. Successive oppositely circularly polarized bursts were detected from AD Leo at 6 cm, suggesting the presence of magnetic fields of both magnetic polarities. An impulsive 20-cm burst from YZ CMi preceded slowly varying 6-cm emission. The VLA was also used, unsuccessfully, to search for 6-cm emission from 13 magnetic Ap stars, all of which exhibit kG magnetic fields. Although the Ap magnetic stars have strong dipolar magnetic fields, the failure to detect gyroresonant radiation suggests that these stars do not have hot, dense coronae. The quiescent microwave emission from GL 735 is probably due to nonthermal radiation, since unusually high (H = 50 kG or greater) surface magnetic fields are inferred under the assumption that the 6-cm radiation is the gyroresonant radiation of thermal electrons.

  3. 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....

  4. Wolf-Rayet stars associated to giant regions of star formation

    International Nuclear Information System (INIS)

    D'Odorico, S.; Rosa, M.

    1982-01-01

    Data on Wolf-Rayet (WR) stars in extragalactic H II regions and emission line galaxies are presented and discussed. The sample is still limited and inhomogeneous but two important points appear to be already established: a) The WR stars are more numerous than the blue supergiants at least in same phase of the evolution of the stellar clusters which ionize the giant H II regions, b) When the WR stars are detected, two cases are apparently observed, one in which only WN, the other in which both WN and WC, are present. (Auth.)

  5. Asteroseismology of white dwarf stars

    OpenAIRE

    Córsico, A. H.

    2014-01-01

    Most of low- and intermediate-mass stars that populate the Universe will end their lives as white dwarf stars. These ancient stellar remnants have encrypted inside a precious record of the evolutionary history of the progenitor stars, providing a wealth of information about the evolution of stars, star formation, and the age of a variety of stellar populations, such as our Galaxy and open and globular clusters. While some information like surface chemical composition, temperature and gravity ...

  6. Metal-poor star formation triggered by the feedback effects from Pop III stars

    Science.gov (United States)

    Chiaki, Gen; Susa, Hajime; Hirano, Shingo

    2018-04-01

    Metal enrichment by first-generation (Pop III) stars is the very first step of the matter cycle in structure formation and it is followed by the formation of extremely metal-poor (EMP) stars. To investigate the enrichment process by Pop III stars, we carry out a series of numerical simulations including the feedback effects of photoionization and supernovae (SNe) of Pop III stars with a range of masses of minihaloes (MHs), Mhalo, and Pop III stars, MPopIII. We find that the metal-rich ejecta reach neighbouring haloes and external enrichment (EE) occurs when the H II region expands before the SN explosion. The neighbouring haloes are only superficially enriched, and the metallicity of the clouds is [Fe/H] < -5. Otherwise, the SN ejecta fall back and recollapse to form an enriched cloud, i.e. an internal-enrichment (IE) process takes place. In the case where a Pop III star explodes as a core-collapse SN (CCSN), the MH undergoes IE, and the metallicity in the recollapsing region is -5 ≲ [Fe/H] ≲ -3 in most cases. We conclude that IE from a single CCSN can explain the formation of EMP stars. For pair-instability SNe (PISNe), EE takes place for all relevant mass ranges of MHs, consistent with the lack of observational signs of PISNe among EMP stars.

  7. Variations in weed population densities, rate of change and community diversity in RR-soybeans and RR-maize strip crops under two herbicide strategies Ação de herbicidas sobre as plantas daninhas na soja e milho RR em plantio consorciado

    Directory of Open Access Journals (Sweden)

    E.S. Leguizamón

    2012-12-01

    Full Text Available Concerns about the sustainability of large-scale, direct-drilled RR-soybeans (Glycine max, and RR-maize (Zea mays under monoculture in central Argentina are growing steadily. An experiment was conducted during three consecutive years to determine the effects of crops and systems (monocultures and strips and herbicide strategy on weed density, population rate of change (l, b community diversity (H´, crop yields and Land Equivalent Ratio (LER. Not only crops but also crop systems differentially influenced weed densities along their growth and development. For crop harvests, weed densities increased in both maize crop systems as compared to in the one for soybeans, but the lowest increase occurred in soybean strips. Differences were leveled by both herbicide strategies, which achieved 73% efficacy during the critical periods in both crops. l of annual monocotyledonous increased, thus shifting the weed community composition. Species richness and H´ were not affected by crop systems, but both herbicide strategies, particularly POST, either in soybeans in monoculture or in maize strips, significantly enhanced H´. Crop yields significantly increased in the maize-strip system with POST (Year 1 or PRE (Years 2 and 3 strategies, thus increasing LER above 1. Herbicide Environmental Load treatments fall within very low or low field use rating.A preocupação com a sustentabilidade do plantio direto da monocultura e do consórcio de soja e milho RR plantados em grande escala na região central da Argentina cresce continuamente. Durante três anos consecutivos, foram determinados os efeitos das culturas de soja e de milho RR, dos sistemas de plantio (monoculturas e consorciado, e a ação de herbicidas sobre a densidade de plantas daninhas, a taxa de mudança da população, a diversidade da comunidade, as safras e a razão de área equivalente. Não apenas as culturas, mas também os sistemas de plantio, influenciaram as densidades de plantas daninhas ao

  8. Spectrophotometry of carbon stars

    Energy Technology Data Exchange (ETDEWEB)

    Oganesyan, R.K.; Karapetyan, M.S.; Nersisyan, S.E.

    1986-01-01

    The results are given of the spectrophotometric investigation of 56 carbon stars in the spectral range from 4000 to 6800 A with resolution 3 A. The observed energy distributions of these stars are determined relative to the flux at the wavelength /sub 0/ = 5556; they are presented in the form of graphs. The energy distributions have been obtained for the first time for 35 stars. Variation in the line Ba II 4554 A has been found in the spectra of St Cam, UU Aur, and RV Mon. Large changes have taken place in the spectra of RT UMa and SS Vir. It is noted that the spectra of carbon stars have a depression, this being situated in different spectral regions for individual groups of stars.

  9. The Search for New Luminous Blue Variable Stars: Near-Infrared Spectroscopy of Stars With 24 micron Shells

    Science.gov (United States)

    Stringfellow, Guy; Gvaramadze, Vasilii

    2010-02-01

    Luminous Blue Variable (LBV) stars represent an extremely rare class of very luminous and massive stars. Only about a dozen confirmed Galactic LBV stars are known to date, which precludes us from determining a solid evolutionary connection between LBV and other intermediate (e.g. Ofpe/WN9, WNL) phases in the life of very massive stars. The known LBV stars each have their own unique properties, so new discoveries add insight into the properties and evolutionary status of LBVs and massive stars; even one new discovery of objects of this type could provide break-through results in the understanding of the intermediate stages of massive star evolution. We have culled a prime sample of possible LBV candidates from the Spitzer 24 (micron) archival data. All have circumstellar nebulae, rings, and shells (typical of LBVs and related stars) surrounding reddened central stars. Spectroscopic followup of about two dozen optically visible central stars associated with the shells from this sample showed that they are either candidate LBVs, late WN-type Wolf-Rayet stars or blue supergiants. We propose infrared spectroscopic observations of the central stars for a large fraction (23 stars) of our northern sample to determine their nature and discover additional LBV candidates. These stars have no plausible optical counterparts, so infrared spectra are needed. This program requires two nights of Hale time using TripleSpec.

  10. The Stars behind the Curtain

    Science.gov (United States)

    2010-02-01

    ESO is releasing a magnificent VLT image of the giant stellar nursery surrounding NGC 3603, in which stars are continuously being born. Embedded in this scenic nebula is one of the most luminous and most compact clusters of young, massive stars in our Milky Way, which therefore serves as an excellent "local" analogue of very active star-forming regions in other galaxies. The cluster also hosts the most massive star to be "weighed" so far. NGC 3603 is a starburst region: a cosmic factory where stars form frantically from the nebula's extended clouds of gas and dust. Located 22 000 light-years away from the Sun, it is the closest region of this kind known in our galaxy, providing astronomers with a local test bed for studying intense star formation processes, very common in other galaxies, but hard to observe in detail because of their great distance from us. The nebula owes its shape to the intense light and winds coming from the young, massive stars which lift the curtains of gas and clouds revealing a multitude of glowing suns. The central cluster of stars inside NGC 3603 harbours thousands of stars of all sorts (eso9946): the majority have masses similar to or less than that of our Sun, but most spectacular are several of the very massive stars that are close to the end of their lives. Several blue supergiant stars crowd into a volume of less than a cubic light-year, along with three so-called Wolf-Rayet stars - extremely bright and massive stars that are ejecting vast amounts of material before finishing off in glorious explosions known as supernovae. Using another recent set of observations performed with the SINFONI instrument on ESO's Very Large Telescope (VLT), astronomers have confirmed that one of these stars is about 120 times more massive than our Sun, standing out as the most massive star known so far in the Milky Way [1]. The clouds of NGC 3603 provide us with a family picture of stars in different stages of their life, with gaseous structures that are

  11. Rodent Research-1 (RR1) NASA Validation Flight: Mouse quadriceps muscle transcriptomic proteomic and epigenomic data

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA s Rodent Research (RR) project is playing a critical role in advancing biomedical research on the physiological effects of space environments. Due to the...

  12. Rodent Research-1 (RR1) NASA Validation Flight: Mouse gastrocnemius muscle transcriptomic proteomic and epigenomic data

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA s Rodent Research (RR) project is playing a critical role in advancing biomedical research on the physiological effects of space environments. Due to the...

  13. Rodent Research-1 (RR1) NASA Validation Flight: Mouse adrenal gland transcriptomic proteomic and epigenomic data

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA s Rodent Research (RR) project is playing a critical role in advancing biomedical research on the physiological effects of space environments. Due to the...

  14. CHEMICAL AND KINEMATICAL PROPERTIES OF BLUE STRAGGLER STARS AND HORIZONTAL BRANCH STARS IN NGC 6397

    International Nuclear Information System (INIS)

    Lovisi, L.; Mucciarelli, A.; Lanzoni, B.; Ferraro, F. R.; Dalessandro, E.; Contreras Ramos, R.; Gratton, R.

    2012-01-01

    We used three sets of high-resolution spectra acquired with the multifiber facility FLAMES at the Very Large Telescope of the European Southern Observatory to investigate the chemical and kinematical properties of a sample of 42 horizontal branch (HB) stars, 18 blue straggler stars (BSSs), and 86 main-sequence (MS) turnoff (TO) and sub-giant branch stars in the nearby globular cluster NGC 6397. We measured rotational velocities and Fe, O, and Mg abundances. All of the unevolved stars in our sample have low rotational velocites (vsin i –1 ), while the HB stars and BSSs show a broad distribution, with values ranging from 0 to ∼70 km s –1 . For HB stars with T 8200 K and T > 10,500 K, respectively) also show significant deviations in their iron abundance with respect to the cluster metallicity (as traced by the unevolved stars, [Fe/H] = –2.12). While similar chemical patterns have already been observed in other hot HB stars, this is the first evidence ever collected for BSSs. We interpret these abundance anomalies as due to the metal radiative levitation, occurring in stars with shallow or no convective envelopes.

  15. Hierarchical Star Formation in Turbulent Media: Evidence from Young Star Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Grasha, K.; Calzetti, D. [Astronomy Department, University of Massachusetts, Amherst, MA 01003 (United States); Elmegreen, B. G. [IBM Research Division, T.J. Watson Research Center, Yorktown Heights, NY (United States); Adamo, A.; Messa, M. [Department of Astronomy, The Oskar Klein Centre, Stockholm University, Stockholm (Sweden); Aloisi, A.; Bright, S. N.; Lee, J. C.; Ryon, J. E.; Ubeda, L. [Space Telescope Science Institute, Baltimore, MD (United States); Cook, D. O. [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA (United States); Dale, D. A. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY (United States); Fumagalli, M. [Institute for Computational Cosmology and Centre for Extragalactic Astronomy, Department of Physics, Durham University, Durham (United Kingdom); Gallagher III, J. S. [Department of Astronomy, University of Wisconsin–Madison, Madison, WI (United States); Gouliermis, D. A. [Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Grebel, E. K. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, D-69120, Heidelberg (Germany); Kahre, L. [Department of Astronomy, New Mexico State University, Las Cruces, NM (United States); Kim, H. [Gemini Observatory, La Serena (Chile); Krumholz, M. R., E-mail: kgrasha@astro.umass.edu [Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia)

    2017-06-10

    We present an analysis of the positions and ages of young star clusters in eight local galaxies to investigate the connection between the age difference and separation of cluster pairs. We find that star clusters do not form uniformly but instead are distributed so that the age difference increases with the cluster pair separation to the 0.25–0.6 power, and that the maximum size over which star formation is physically correlated ranges from ∼200 pc to ∼1 kpc. The observed trends between age difference and separation suggest that cluster formation is hierarchical both in space and time: clusters that are close to each other are more similar in age than clusters born further apart. The temporal correlations between stellar aggregates have slopes that are consistent with predictions of turbulence acting as the primary driver of star formation. The velocity associated with the maximum size is proportional to the galaxy’s shear, suggesting that the galactic environment influences the maximum size of the star-forming structures.

  16. PROGRESSIVE STAR FORMATION IN THE YOUNG GALACTIC SUPER STAR CLUSTER NGC 3603

    International Nuclear Information System (INIS)

    Beccari, Giacomo; Spezzi, Loredana; De Marchi, Guido; Andersen, Morten; Paresce, Francesco; Young, Erick; Panagia, Nino; Bond, Howard; Balick, Bruce; Calzetti, Daniela; Carollo, C. Marcella; Disney, Michael J.; Dopita, Michael A.; Frogel, Jay A.; Hall, Donald N. B.; Holtzman, Jon A.; Kimble, Randy A.; McCarthy, Patrick J.; O'Connell, Robert W.; Saha, Abhijit

    2010-01-01

    Early Release Science observations of the cluster NGC 3603 with the WFC3 on the refurbished Hubble Space Telescope allow us to study its recent star formation history. Our analysis focuses on stars with Hα excess emission, a robust indicator of their pre-main sequence (PMS) accreting status. The comparison with theoretical PMS isochrones shows that 2/3 of the objects with Hα excess emission have ages from 1 to 10 Myr, with a median value of 3 Myr, while a surprising 1/3 of them are older than 10 Myr. The study of the spatial distribution of these PMS stars allows us to confirm their cluster membership and to statistically separate them from field stars. This result establishes unambiguously for the first time that star formation in and around the cluster has been ongoing for at least 10-20 Myr, at an apparently increasing rate.

  17. Carbon Stars T. Lloyd Evans

    Indian Academy of Sciences (India)

    that the features used in estimating luminosities of ordinary giant stars are just those whose abundance ... This difference between the spectral energy distributions (SEDs) of CH stars and the. J stars, which belong to .... that the first group was binaries, as for the CH stars of the solar vicinity, while those of the second group ...

  18. The Spacelab IPS Star Simulator

    Science.gov (United States)

    Wessling, Francis C., III

    The cost of doing business in space is very high. If errors occur while in orbit the costs grow and desired scientific data may be corrupted or even lost. The Spacelab Instrument Pointing System (IPS) Star Simulator is a unique test bed that allows star trackers to interface with simulated stars in a laboratory before going into orbit. This hardware-in-the loop testing of equipment on earth increases the probability of success while in space. The IPS Star Simulator provides three fields of view 2.55 x 2.55 degrees each for input into star trackers. The fields of view are produced on three separate monitors. Each monitor has 4096 x 4096 addressable points and can display 50 stars (pixels) maximum at a given time. The pixel refresh rate is 1000 Hz. The spectral output is approximately 550 nm. The available relative visual magnitude range is 2 to 8 visual magnitudes. The star size is less than 100 arc seconds. The minimum star movement is less than 5 arc seconds and the relative position accuracy is approximately 40 arc seconds. The purpose of this paper is to describe the LPS Star Simulator design and to provide an operational scenario so others may gain from the approach and possible use of the system.

  19. 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.

  20. Ecology of blue straggler stars

    CERN Document Server

    Carraro, Giovanni; Beccari, Giacomo

    2015-01-01

    The existence of blue straggler stars, which appear younger, hotter, and more massive than their siblings, is at odds with a simple picture of stellar evolution. Such stars should have exhausted their nuclear fuel and evolved long ago to become cooling white dwarfs. They are found to exist in globular clusters, open clusters, dwarf spheroidal galaxies of the Local Group, OB associations and as field stars. This book summarises the many advances in observational and theoretical work dedicated to blue straggler stars. Carefully edited extended contributions by well-known experts in the field cover all the relevant aspects of blue straggler stars research: Observations of blue straggler stars in their various environments; Binary stars and formation channels; Dynamics of globular clusters; Interpretation of observational data and comparison with models. The book also offers an introductory chapter on stellar evolution written by the editors of the book.

  1. What Determines Star Formation Rates?

    Science.gov (United States)

    Evans, Neal John

    2017-06-01

    The relations between star formation and gas have received renewed attention. We combine studies on scales ranging from local (within 0.5 kpc) to distant galaxies to assess what factors contribute to star formation. These include studies of star forming regions in the Milky Way, the LMC, nearby galaxies with spatially resolved star formation, and integrated galaxy studies. We test whether total molecular gas or dense gas provides the best predictor of star formation rate. The star formation ``efficiency," defined as star formation rate divided by mass, spreads over a large range when the mass refers to molecular gas; the standard deviation of the log of the efficiency decreases by a factor of three when the mass of relatively dense molecular gas is used rather than the mass of all the molecular gas. We suggest ways to further develop the concept of "dense gas" to incorporate other factors, such as turbulence.

  2. Mass loss from S stars

    International Nuclear Information System (INIS)

    Jura, M.

    1988-01-01

    The mass-loss process in S stars is studied using 65 S stars from the listing of Wing and Yorka (1977). The role of pulsations in the mass-loss process is examined. It is detected that stars with larger mass-loss rates have a greater amplitude of pulsations. The dust-to-gas ratio for the S stars is estimated as 0.002 and the average mass-loss rate is about 6 x 10 to the -8th solar masses/yr. Some of the properties of the S stars, such as scale height, surface density, and lifetime, are measured. It is determined that scale height is 200 pc; the total duration of the S star phase is greater than or equal to 30,000 yr; and the stars inject 3 x 10 to the -6th solar masses/sq kpc yr into the interstellar medium. 46 references

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

    NARCIS (Netherlands)

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

  4. 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....

  5. 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 ...

  6. OBSERVATIONAL CONSTRAINTS ON FIRST-STAR NUCLEOSYNTHESIS. I. EVIDENCE FOR MULTIPLE PROGENITORS OF CEMP-NO STARS

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Jinmi; Beers, Timothy C.; Placco, Vinicius M.; Rasmussen, Kaitlin C.; Carollo, Daniela [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); He, Siyu [Department of Physics, Xi’an Jiaotong University, Shaanxi, 710049 (China); Hansen, Terese T. [Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Roederer, Ian U. [Joint Institute for Nuclear Astrophysics-Center for the Evolution of the Elements (JINA-CEE) (United States); Zeanah, Jeff, E-mail: jinmi.yoon@nd.edu [Z Solutions, Inc., 9430 Huntcliff Trace, Atlanta, GA 30350 (United States)

    2016-12-10

    We investigate anew the distribution of absolute carbon abundance, A (C) = log ϵ (C), for carbon-enhanced metal-poor (CEMP) stars in the halo of the Milky Way, based on high-resolution spectroscopic data for a total sample of 305 CEMP stars. The sample includes 147 CEMP- s (and CEMP- r / s ) stars, 127 CEMP-no stars, and 31 CEMP stars that are unclassified, based on the currently employed [Ba/Fe] criterion. We confirm previous claims that the distribution of A (C) for CEMP stars is (at least) bimodal, with newly determined peaks centered on A (C) = 7.96 (the high-C region) and A (C) = 6.28 (the low-C region). A very high fraction of CEMP- s (and CEMP- r / s ) stars belongs to the high-C region, while the great majority of CEMP-no stars resides in the low-C region. However, there exists complexity in the morphology of the A (C)-[Fe/H] space for the CEMP-no stars, a first indication that more than one class of first-generation stellar progenitors may be required to account for their observed abundances. The two groups of CEMP-no stars we identify exhibit clearly different locations in the A (Na)- A (C) and A (Mg)- A (C) spaces, also suggesting multiple progenitors. The clear distinction in A (C) between the CEMP- s (and CEMP- r / s ) stars and the CEMP-no stars appears to be as successful, and likely more astrophysically fundamental, for the separation of these sub-classes as the previously recommended criterion based on [Ba/Fe] (and [Ba/Eu]) abundance ratios. This result opens the window for its application to present and future large-scale low- and medium-resolution spectroscopic surveys.

  7. Close binary star type x-ray star and its mechanism of radiation

    Energy Technology Data Exchange (ETDEWEB)

    Hoshi, R [Rikkyo Univ., Tokyo (Japan). Dept. of Physics

    1975-09-01

    Recent progress of the study of an X-ray star is described. In 1970, the periodical emission of pulsed X-rays from Cen X-3 and Her X-1 was observed. An optically corresponding celestial object for the Cen X-3 was reported in 1973, and the mass of Cen X-3 was revised. The optical object was named after Krzeminsky. From the observed variation of luminosity, it is said that the Krzeminsky's star is deformed. This fact gave new data on the mass of the Cen X-3, and the mass is several times as large as the previously estimated value. The behavior of the Her X-1 shows four kinds of clear time variation, and indicates the characteristics of an X-ray star. The Her X-1 is an X-ray pulser the same as Cen X-3, and is a close binary star. The opposite star is known as HZ-Her, and shows weaker luminosity than the intensity of X-ray from the Her X-1. Thirty-five day period was seen in the intensity variation of X-ray. The mechanism of X-ray pulsing can be explained by material flow into a neutron star. The energy spectrum from Her X-1 is different from that from the Cen X-3. Another X-ray star, Cyg X-1, is considered to be a black hole from its X-ray spectrum.

  8. Destruction of a Magnetized Star

    Science.gov (United States)

    Kohler, Susanna

    2017-01-01

    What happens when a magnetized star is torn apart by the tidal forces of a supermassive black hole, in a violent process known as a tidal disruption event? Two scientists have broken new ground by simulating the disruption of stars with magnetic fields for the first time.The magnetic field configuration during a simulation of the partial disruption of a star. Top left: pre-disruption star. Bottom left: matter begins to re-accrete onto the surviving core after the partial disruption. Right: vortices form in the core as high-angular-momentum debris continues to accrete, winding up and amplifying the field. [Adapted from Guillochon McCourt 2017]What About Magnetic Fields?Magnetic fields are expected to exist in the majority of stars. Though these fields dont dominate the energy budget of a star the magnetic pressure is a million times weaker than the gas pressure in the Suns interior, for example they are the drivers of interesting activity, like the prominences and flares of our Sun.Given this, we can wonder what role stars magnetic fields might play when the stars are torn apart in tidal disruption events. Do the fields change what we observe? Are they dispersed during the disruption, or can they be amplified? Might they even be responsible for launching jets of matter from the black hole after the disruption?Star vs. Black HoleIn a recent study, James Guillochon (Harvard-Smithsonian Center for Astrophysics) and Michael McCourt (Hubble Fellow at UC Santa Barbara) have tackled these questions by performing the first simulations of tidal disruptions of stars that include magnetic fields.In their simulations, Guillochon and McCourt evolve a solar-mass star that passes close to a million-solar-mass black hole. Their simulations explore different magnetic field configurations for the star, and they consider both what happens when the star barely grazes the black hole and is only partially disrupted, as well as what happens when the black hole tears the star apart

  9. 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.

  10. Numerical study of rotating relativistic stars

    International Nuclear Information System (INIS)

    Wilson, J.R.

    1975-01-01

    The equations of structure for rotating stars in general relativity are presented and put in a form suitable for computer calculations. The results of equilibrium calculations for supermassive stars, neutron stars, and magnetically supported stars are reported, as are calculations of collapsing, rotating, and magnetized stars in the slowly changing gravitational field approximation. (auth)

  11. FASHIONABLY LATE? BUILDING UP THE MILKY WAY'S INNER HALO

    International Nuclear Information System (INIS)

    Morrison, Heather L.; Harding, Paul; Helmi, Amina

    2009-01-01

    Using a sample of 246 metal-poor stars (RR Lyraes, red giants, and red horizontal branch stars) which is remarkable for the accuracy of its six-dimensional kinematical data, we find, by examining the distribution of stellar orbital angular momenta, a new component for the local halo which has an axial ratio c/a ∼ 0.2, a similar flattening to the thick disk. It has a small prograde rotation but is supported by velocity anisotropy, and contains more intermediate-metallicity stars (with -1.5 < [Fe/H] < -1.0) than the rest of our sample. We suggest that this component was formed quite late, during or after the formation of the disk. It formed either from the gas that was accreted by the last major mergers experienced by the Galaxy, or by dynamical friction of massive infalling satellite(s) with the halo and possibly the stellar disk or thick disk. The remainder of the halo stars in our sample, which are less closely confined to the disk plane, exhibit a clumpy distribution in energy and angular momentum, suggesting that the early, chaotic conditions under which the inner halo formed were not violent enough to erase the record of their origins. The clumpy structure suggests that a relatively small number of progenitors were responsible for building up the inner halo, in line with theoretical expectations. We find a difference in mean binding energy between the RR Lyrae variables and the red giants in our sample, suggesting that more of the RR Lyraes in the sample belong to the outer halo, and that the outer halo may be somewhat younger, as first suggested by Searle and Zinn. We also find that the RR Lyrae mean rotation is more negative than the red giants, which is consistent with the recent result of Carollo et al. that the outer halo has a retrograde rotation and with the difference in kinematics seen between RR Lyraes and blue horizontal branch stars by Kinman et al. (2007).

  12. NEW OPTICAL REDDENING MAPS OF THE LARGE AND SMALL MAGELLANIC CLOUDS

    International Nuclear Information System (INIS)

    Haschke, Raoul; Grebel, Eva K.; Duffau, Sonia

    2011-01-01

    We present new reddening maps of the Small Magellanic Cloud (SMC) and Large Magellanic Cloud (LMC) based on the data of the third phase of the Optical Gravitational Lensing Experiment (OGLE III). We have used two different methods to derive optical reddening maps. We adopt a theoretical mean unreddened color for the red clump (RC) in the SMC and LMC, respectively. We subdivide the photometric data for both Clouds into subfields and calculate the difference between the observed RC position and the theoretical value for each field, which provides us with the reddening value in (V - I). Furthermore, reddening values are obtained for 13490 LMC RR Lyrae ab and 1529 SMC RR Lyrae ab stars covering the whole OGLE III region of the Magellanic Clouds (MCs). The observed colors (V - I) of the RR Lyrae stars are compared with the color from the absolute magnitudes. The absolute magnitude of each RR Lyrae star is computed using its period and metallicity derived from Fourier decomposition of its light curve. In general, we find a low and uniform reddening distribution in both MCs. The RC method indicates a mean reddening of the LMC of E(V - I) = 0.09 ± 0.07 mag, while for the SMC E(V - I) = 0.04 ± 0.06 mag is obtained. With RR Lyrae stars a median value of E(V - I) = 0.11 ± 0.06 mag for the LMC and E(V - I) = 0.07 ± 0.06 mag for the SMC is found. The LMC shows very low reddening in the bar region, whereas the reddening in the star-forming leading edge and 30 Doradus is considerably higher. In the SMC, three pronounced regions with higher reddening are visible. Two are located along the bar, while the highest reddening is found in the star-forming wing of the SMC. In general, the regions with higher reddening are in good spatial agreement with infrared reddening maps as well as with reddening estimations of other studies. The position-dependent reddening values from the RC method are available via the German Astrophysical Virtual Observatory interface.

  13. Statistical properties of barium stars

    International Nuclear Information System (INIS)

    Hakkila, J.E.

    1986-01-01

    Barium stars are G- and K-giant stars with atmospheric excesses of s-process elements, and a broadband spectral depression in the blue portion of the spectrum. The strength of the λ4554 Ball line is used as a classification parameter known as the Barium Intensity. They have a mean absolute magnitude of 1.0 and a dispersion of 1.2 magnitudes (assuming a Gaussian distribution in absolute magnitude) as measured from secular and statistical parallaxes. These stars apparently belong to a young-disk population from analyses of both the solar reflex motion and their residual velocity distribution, which implies that they have an upper mass limit of around three solar masses. There is no apparent correlation of barium intensity with either luminosity or kinematic properties. The barium stars appear to be preferentially distributed in the direction of the local spiral arm, but show no preference to associate with or avoid the direction of the galactic center. They do not appear related to either the carbon or S-stars because of these tendencies and because of the stellar population to which each type of star belongs. The distribution in absolute magnitude combined with star count analyses implies that these stars are slightly less numerous than previously believed. Barium stars show infrared excesses that correlate with their barium intensities

  14. Retired A Stars and Their Companions. III. Comparing the Mass-Period Distributions of Planets Around A-Type Stars and Sun-Like Stars

    Science.gov (United States)

    Bowler, Brendan P.; Johnson, John Asher; Marcy, Geoffrey W.; Henry, Gregory W.; Peek, Kathryn M. G.; Fischer, Debra A.; Clubb, Kelsey I.; Liu, Michael C.; Reffert, Sabine; Schwab, Christian; Lowe, Thomas B.

    2010-01-01

    We present an analysis of ~5 years of Lick Observatory radial velocity measurements targeting a uniform sample of 31 intermediate-mass (IM) subgiants (1.5 lsim M */M sunlsim 2.0) with the goal of measuring the occurrence rate of Jovian planets around (evolved) A-type stars and comparing the distributions of their orbital and physical characteristics to those of planets around Sun-like stars. We provide updated orbital solutions incorporating new radial velocity measurements for five known planet-hosting stars in our sample; uncertainties in the fitted parameters are assessed using a Markov-Chain Monte Carlo method. The frequency of Jovian planets interior to 3 AU is 26+9 -8%, which is significantly higher than the 5%-10% frequency observed around solar-mass stars. The median detection threshold for our sample includes minimum masses down to {0.2, 0.3, 0.5, 0.6, 1.3} M Jup within {0.1, 0.3, 0.6, 1.0, 3.0} AU. To compare the properties of planets around IM stars to those around solar-mass stars we synthesize a population of planets based on the parametric relationship dN vprop M α P β dlnMdlnP, the observed planet frequency, and the detection limits we derived. We find that the values of α and β for planets around solar-type stars from Cumming et al. fail to reproduce the observed properties of planets in our sample at the 4σ level, even when accounting for the different planet occurrence rates. Thus, the properties of planets around A stars are markedly different than those around Sun-like stars, suggesting that only a small (~50%) increase in stellar mass has a large influence on the formation and orbital evolution of planets. Based on observations obtained at the Lick Observatory, which is operated by the University of California.

  15. Star-forming Filament Models

    International Nuclear Information System (INIS)

    Myers, Philip C.

    2017-01-01

    New models of star-forming filamentary clouds are presented in order to quantify their properties and to predict their evolution. These 2D axisymmetric models describe filaments that have no core, one low-mass core, and one cluster-forming core. They are based on Plummer-like cylinders and spheroids that are bounded by a constant-density surface of finite extent. In contrast to 1D Plummer-like models, they have specific values of length and mass, they approximate observed column density maps, and their distributions of column density ( N -pdfs) are pole-free. Each model can estimate the star-forming potential of a core-filament system by identifying the zone of gas dense enough to form low-mass stars and by counting the number of enclosed thermal Jeans masses. This analysis suggests that the Musca central filament may be near the start of its star-forming life, with enough dense gas to make its first ∼3 protostars, while the Coronet filament is near the midpoint of its star formation, with enough dense gas to add ∼8 protostars to its ∼20 known stars. In contrast, L43 appears to be near the end of its star-forming life, since it lacks enough dense gas to add any new protostars to the two young stellar objectsalready known.

  16. Star-forming Filament Models

    Energy Technology Data Exchange (ETDEWEB)

    Myers, Philip C., E-mail: pmyers@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2017-03-20

    New models of star-forming filamentary clouds are presented in order to quantify their properties and to predict their evolution. These 2D axisymmetric models describe filaments that have no core, one low-mass core, and one cluster-forming core. They are based on Plummer-like cylinders and spheroids that are bounded by a constant-density surface of finite extent. In contrast to 1D Plummer-like models, they have specific values of length and mass, they approximate observed column density maps, and their distributions of column density ( N -pdfs) are pole-free. Each model can estimate the star-forming potential of a core-filament system by identifying the zone of gas dense enough to form low-mass stars and by counting the number of enclosed thermal Jeans masses. This analysis suggests that the Musca central filament may be near the start of its star-forming life, with enough dense gas to make its first ∼3 protostars, while the Coronet filament is near the midpoint of its star formation, with enough dense gas to add ∼8 protostars to its ∼20 known stars. In contrast, L43 appears to be near the end of its star-forming life, since it lacks enough dense gas to add any new protostars to the two young stellar objectsalready known.

  17. 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....

  18. X-ray sources in regions of star formation. II. The pre-main-sequence G star HDE 283572

    International Nuclear Information System (INIS)

    Walter, F.M.; Brown, A.; Linsky, J.L.; Rydgren, A.E.; Vrba, F.; Joint Institute for Laboratory Astrophysics, Boulder, CO; Computer Sciences Corp., El Segundo, CA; Naval Observatory, Flagstaff, AZ)

    1987-01-01

    This paper reports the detection of HDE 283572, a ninth-magnitude G star 8 arcmin south of RY Tau, as a bright X-ray source. The observations reveal this object to be a fairly massive (about 2 solar masses) pre-main-sequence star associated with the Taurus-Auriga star formation complex. It exhibits few of the characteristics of the classical T Tauri stars and is a good example of a naked T Tauri star. The star is a mid-G subgiant, of about three solar radii and rotates with a period of 1.5 d. The coronal and chromospheric surface fluxes are similar to those of the most active late type stars (excluding T Tauri stars). The X-ray and UV lines most likely arise in different atmospheric structures. Radiative losses are some 1000 times the quiet solar value and compare favorably with those of T Tauri stars. 49 references

  19. Turbulent flow heat transfer in ET-RR-1

    International Nuclear Information System (INIS)

    Khattab, M.; Mina, A.R.

    1990-01-01

    In nuclear reactors the effect of heat transfer coefficient, which depends on the constant C. Is primordial in calculating the clad surface temperatures. To determine the constant C of ET-RR-1 fuel bundles based on in-pile measurements different well known and recommended values of C are verified. A computer program is written to calculate steady thermal core characteristics at different operating conditions. The total flow rate is distributed considering same pressure drop across the core irrespective of bundle location. The total reactor power is readily distributed as Bessel function. The flow and power per bundle are equally distributed among the fuel rods irrespective of their positions inside the bundle. It is found that the constant C equals 0.047 gives acceptable compatibility between measurements and calculations. The maximum clad surface temperature is shifted from the core center

  20. 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

  1. MMT HYPERVELOCITY STAR SURVEY. II. FIVE NEW UNBOUND STARS

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Warren R.; Geller, Margaret J.; Kenyon, Scott J., E-mail: wbrown@cfa.harvard.edu, E-mail: mgeller@cfa.harvard.edu, E-mail: skenyon@cfa.harvard.edu [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)

    2012-05-20

    We present the discovery of five new unbound hypervelocity stars (HVSs) in the outer Milky Way halo. Using a conservative estimate of Galactic escape velocity, our targeted spectroscopic survey has now identified 16 unbound HVSs as well as a comparable number of HVSs ejected on bound trajectories. A Galactic center origin for the HVSs is supported by their unbound velocities, the observed number of unbound stars, their stellar nature, their ejection time distribution, and their Galactic latitude and longitude distribution. Other proposed origins for the unbound HVSs, such as runaway ejections from the disk or dwarf galaxy tidal debris, cannot be reconciled with the observations. An intriguing result is the spatial anisotropy of HVSs on the sky, which possibly reflects an anisotropic potential in the central 10-100 pc region of the Galaxy. Further progress requires measurement of the spatial distribution of HVSs over the southern sky. Our survey also identifies seven B supergiants associated with known star-forming galaxies; the absence of B supergiants elsewhere in the survey implies there are no new star-forming galaxies in our survey footprint to a depth of 1-2 Mpc.

  2. Measure of the QT-RR Dynamic Coupling in Patients with the Long QT Syndrome

    Czech Academy of Sciences Publication Activity Database

    Halámek, Josef; Couderc, J. P.; Jurák, Pavel; Vondra, Vlastimil; Zareba, W.; Viščor, Ivo; Leinveber, P.

    2012-01-01

    Roč. 17, č. 4 (2012), s. 323-330 ISSN 1082-720X R&D Projects: GA MŠk ME09050 Institutional support: RVO:68081731 Keywords : Long QT syndrome * Dynamic QT-RR coupling * Holter recording * QT adaptation * QT parameters Subject RIV: FA - Cardiovascular Diseases incl. Cardiotharic Surgery Impact factor: 1.084, year: 2012

  3. Production of R,R-2,3-butanediol of ultra-high optical purity from Paenibacillus polymyxa ZJ-9 using homologous recombination.

    Science.gov (United States)

    Zhang, Li; Cao, Can; Jiang, Ruifan; Xu, Hong; Xue, Feng; Huang, Weiwei; Ni, Hao; Gao, Jian

    2018-08-01

    The present study describes the use of metabolic engineering to achieve the production of R,R-2,3-butanediol (R,R-2,3-BD) of ultra-high optical purity (>99.99%). To this end, the diacetyl reductase (DAR) gene (dud A) of Paenibacillus polymyxa ZJ-9 was knocked out via homologous recombination between the genome and the previously constructed targeting vector pRN5101-L'C in a process based on homologous single-crossover. PCR verification confirmed the successful isolation of the dud A gene disruption mutant P. polymyxa ZJ-9-△dud A. Moreover, fermentation results indicated that the optical purity of R,R-2,3-BD increased from about 98% to over 99.99%, with a titer of 21.62 g/L in Erlenmeyer flasks. The latter was further increased to 25.88 g/L by fed-batch fermentation in a 5-L bioreactor. Copyright © 2018 Elsevier Ltd. All rights reserved.

  4. THE CHANDRA VARIABLE GUIDE STAR CATALOG

    International Nuclear Information System (INIS)

    Nichols, Joy S.; Lauer, Jennifer L.; Morgan, Douglas L.; Sundheim, Beth A.; Henden, Arne A.; Huenemoerder, David P.; Martin, Eric

    2010-01-01

    Variable stars have been identified among the optical-wavelength light curves of guide stars used for pointing control of the Chandra X-ray Observatory. We present a catalog of these variable stars along with their light curves and ancillary data. Variability was detected to a lower limit of 0.02 mag amplitude in the 4000-10000 A range using the photometrically stable Aspect Camera on board the Chandra spacecraft. The Chandra Variable Guide Star Catalog (VGUIDE) contains 827 stars, of which 586 are classified as definitely variable and 241 are identified as possibly variable. Of the 586 definite variable stars, we believe 319 are new variable star identifications. Types of variables in the catalog include eclipsing binaries, pulsating stars, and rotating stars. The variability was detected during the course of normal verification of each Chandra pointing and results from analysis of over 75,000 guide star light curves from the Chandra mission. The VGUIDE catalog represents data from only about 9 years of the Chandra mission. Future releases of VGUIDE will include newly identified variable guide stars as the mission proceeds. An important advantage of the use of space data to identify and analyze variable stars is the relatively long observations that are available. The Chandra orbit allows for observations up to 2 days in length. Also, guide stars were often used multiple times for Chandra observations, so many of the stars in the VGUIDE catalog have multiple light curves available from various times in the mission. The catalog is presented as both online data associated with this paper and as a public Web interface. Light curves with data at the instrumental time resolution of about 2 s, overplotted with the data binned at 1 ks, can be viewed on the public Web interface and downloaded for further analysis. VGUIDE is a unique project using data collected during the mission that would otherwise be ignored. The stars available for use as Chandra guide stars are

  5. Spectrophotometry of carbon stars

    International Nuclear Information System (INIS)

    Gow, C.E.

    1975-01-01

    Observations of over one hundred carbon stars have been made with the Indiana rapid spectral scanner in the red and, when possible, in the visual and blue regions of the spectrum. Five distinct subtypes of carbon stars (Barium, CH, R, N, and hydrogen deficient) are represented in the list of observed stars, although the emphasis was placed on the N stars when the observations were made. The rapid scanner was operated in the continuous sweep mode with the exit slit set at twenty angstroms, however, seeing fluctuations and guiding errors smear the spectrum to an effective resolution of approximately thirty angstroms. Nightly observations of Hayes standard stars yielded corrections for atmospheric extinction and instrumental response. The reduction scheme rests on two assumptions, that thin clouds are gray absorbers and the wavelength dependence of the sky transparency does not change during the course of the night. Several stars have been observed in the blue region of the spectrum with the Indiana SIT vidicon spectrometer at two angstroms resolution. It is possible to derive a color temperature for the yellow--red spectral region by fitting a black-body curve through two chosen continuum points. Photometric indices were calculated relative to the blackbody curve to measure the C 2 Swan band strength, the shape of the CN red (6,1) band to provide a measure of the 12 C/ 13 C isotope ratio, and in the hot carbon stars (Barium, CH, and R stars) the strength of an unidentified feature centered at 400 angstroms. An extensive abundance grid of model atmospheres was calculated using a modified version of the computer code ATLAS

  6. Stacked Star Formation Rate Profiles of Bursty Galaxies Exhibit “Coherent” Star Formation

    Science.gov (United States)

    Orr, Matthew E.; Hayward, Christopher C.; Nelson, Erica J.; Hopkins, Philip F.; Faucher-Giguère, Claude-André; Kereš, Dušan; Chan, T. K.; Schmitz, Denise M.; Miller, Tim B.

    2017-11-01

    In a recent work based on 3200 stacked Hα maps of galaxies at z˜ 1, Nelson et al. find evidence for “coherent star formation”: the stacked star formation rate (SFR) profiles of galaxies above (below) the “star formation main sequence” (MS) are above (below) that of galaxies on the MS at all radii. One might interpret this result as inconsistent with highly bursty star formation and evidence that galaxies evolve smoothly along the MS rather than crossing it many times. We analyze six simulated galaxies at z˜ 1 from the Feedback in Realistic Environments (FIRE) project in a manner analogous to the observations to test whether the above interpretations are correct. The trends in stacked SFR profiles are qualitatively consistent with those observed. However, SFR profiles of individual galaxies are much more complex than the stacked profiles: the former can be flat or even peak at large radii because of the highly clustered nature of star formation in the simulations. Moreover, the SFR profiles of individual galaxies above (below) the MS are not systematically above (below) those of MS galaxies at all radii. We conclude that the time-averaged coherent star formation evident stacks of observed galaxies is consistent with highly bursty, clumpy star formation of individual galaxies and is not evidence that galaxies evolve smoothly along the MS.

  7. STAR facility tritium accountancy

    International Nuclear Information System (INIS)

    Pawelko, R. J.; Sharpe, J. P.; Denny, B. J.

    2008-01-01

    The Safety and Tritium Applied Research (STAR) facility has been established to provide a laboratory infrastructure for the fusion community to study tritium science associated with the development of safe fusion energy and other technologies. STAR is a radiological facility with an administrative total tritium inventory limit of 1.5 g (14,429 Ci) [1]. Research studies with moderate tritium quantities and various radionuclides are performed in STAR. Successful operation of the STAR facility requires the ability to receive, inventory, store, dispense tritium to experiments, and to dispose of tritiated waste while accurately monitoring the tritium inventory in the facility. This paper describes tritium accountancy in the STAR facility. A primary accountancy instrument is the tritium Storage and Assay System (SAS): a system designed to receive, assay, store, and dispense tritium to experiments. Presented are the methods used to calibrate and operate the SAS. Accountancy processes utilizing the Tritium Cleanup System (TCS), and the Stack Tritium Monitoring System (STMS) are also discussed. Also presented are the equations used to quantify the amount of tritium being received into the facility, transferred to experiments, and removed from the facility. Finally, the STAR tritium accountability database is discussed. (authors)

  8. Young Stars with SALT

    Energy Technology Data Exchange (ETDEWEB)

    Riedel, Adric R. [Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Alam, Munazza K.; Rice, Emily L.; Cruz, Kelle L. [Department of Astrophysics, The American Museum of Natural History, New York, NY 10024 (United States); Henry, Todd J., E-mail: arr@caltech.edu [RECONS Institute, Chambersburg, PA (United States)

    2017-05-10

    We present a spectroscopic and kinematic analysis of 79 nearby M dwarfs in 77 systems. All of these dwarfs are low-proper-motion southern hemisphere objects and were identified in a nearby star survey with a demonstrated sensitivity to young stars. Using low-resolution optical spectroscopy from the Red Side Spectrograph on the South African Large Telescope, we have determined radial velocities, H-alpha, lithium 6708 Å, and potassium 7699 Å equivalent widths linked to age and activity, and spectral types for all of our targets. Combined with astrometric information from literature sources, we identify 44 young stars. Eighteen are previously known members of moving groups within 100 pc of the Sun. Twelve are new members, including one member of the TW Hydra moving group, one member of the 32 Orionis moving group, 9 members of Tucana-Horologium, one member of Argus, and two new members of AB Doradus. We also find 14 young star systems that are not members of any known groups. The remaining 33 star systems do not appear to be young. This appears to be evidence of a new population of nearby young stars not related to the known nearby young moving groups.

  9. Cataclysmic Variable Stars

    Science.gov (United States)

    Hellier, Coel

    2001-01-01

    Cataclysmic variable stars are the most variable stars in the night sky, fluctuating in brightness continually on timescales from seconds to hours to weeks to years. The changes can be recorded using amateur telescopes, yet are also the subject of intensive study by professional astronomers. That study has led to an understanding of cataclysmic variables as binary stars, orbiting so closely that material transfers from one star to the other. The resulting process of accretion is one of the most important in astrophysics. This book presents the first account of cataclysmic variables at an introductory level. Assuming no previous knowledge of the field, it explains the basic principles underlying the variability, while providing an extensive compilation of cataclysmic variable light curves. Aimed at amateur astronomers, undergraduates, and researchers, the main text is accessible to those with no mathematical background, while supplementary boxes present technical details and equations.

  10. Post-giant evolution of helium stars

    International Nuclear Information System (INIS)

    Schoenberner, D.

    1977-01-01

    Extremely hydrogen deficient stars (helium stars and R Coronae Borealis variables) are considered to be remnants of double shell source stars (of the asymptotic giant branch). The evolution of stars with a condensed C/O-core and a helium envelope is followed numerically from the red giant stage to the white dwarf domain, crossing the regions of R CrB- and helium stars (so far analyzed). They have typically masses M/M(sun) = 0.7 and luminosities log L/L(sun) = 4.1. The time for crossing the helium star domain is some 10 3 years. The corresponding times in the R CrB-region amounts up to several 10 4 years. The lower limit of the death rate of helium stars is estimated to be 4 x 10 -14 pc -3 yr -1 . This value is only a factor of ten lower than the birth rate of all non-DA white dwarfs. It is therefore possible that the helium stars are the precursors of helium rich white dwarfs. As a consequence, a significant fraction of all stars which end their lives as white dwarfs should pass through the helium star phase. (orig.) [de

  11. Dysregulated Homeostasis of Acetylcholine Levels in Immune Cells of RR-Multiple Sclerosis Patients

    Directory of Open Access Journals (Sweden)

    Maria Di Bari

    2016-11-01

    Full Text Available Multiple sclerosis (MS is characterized by pro-inflammatory cytokine production. Acetylcholine (ACh contributes to the modulation of central and peripheral inflammation. We studied the homeostasis of the cholinergic system in relation to cytokine levels in immune cells and sera of relapsing remitting-MS (RR-MS patients. We demonstrated that lower ACh levels in serum of RR-MS patients were inversely correlated with the increased activity of the hydrolyzing enzymes acetylcholinesterase (AChE and butyrylcholinesterase (BuChE. Interestingly, the expression of the ACh biosynthetic enzyme and the protein carriers involved in non-vesicular ACh release were found overexpressed in peripheral blood mononuclear cells of MS patients. The inflammatory state of the MS patients was confirmed by increased levels of TNFα, IL-12/IL-23p40, IL-18. The lower circulating ACh levels in sera of MS patients are dependent on the higher activity of cholinergic hydrolyzing enzymes. The smaller ratio of ACh to TNFα, IL-12/IL-23p40 and IL-18 in MS patients, with respect to healthy donors (HD, is indicative of an inflammatory environment probably related to the alteration of cholinergic system homeostasis.

  12. Properties of Asymmetric Detrended Fluctuation Analysis in the time series of RR intervals

    Science.gov (United States)

    Piskorski, J.; Kosmider, M.; Mieszkowski, D.; Krauze, T.; Wykretowicz, A.; Guzik, P.

    2018-02-01

    Heart rate asymmetry is a phenomenon by which the accelerations and decelerations of heart rate behave differently, and this difference is consistent and unidirectional, i.e. in most of the analyzed recordings the inequalities have the same directions. So far, it has been established for variance and runs based types of descriptors of RR intervals time series. In this paper we apply the newly developed method of Asymmetric Detrended Fluctuation Analysis, which so far has mainly been used with economic time series, to the set of 420 stationary 30 min time series of RR intervals from young, healthy individuals aged between 20 and 40. This asymmetric approach introduces separate scaling exponents for rising and falling trends. We systematically study the presence of asymmetry in both global and local versions of this method. In this study global means "applying to the whole time series" and local means "applying to windows jumping along the recording". It is found that the correlation structure of the fluctuations left over after detrending in physiological time series shows strong asymmetric features in both magnitude, with α+ physiological data after shuffling or with a group of symmetric synthetic time series.

  13. 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...

  14. Energy star compliant voice over internet protocol (VoIP) telecommunications network including energy star compliant VoIP devices

    Science.gov (United States)

    Kouchri, Farrokh Mohammadzadeh

    2012-11-06

    A Voice over Internet Protocol (VoIP) communications system, a method of managing a communications network in such a system and a program product therefore. The system/network includes an ENERGY STAR (E-star) aware softswitch and E-star compliant communications devices at system endpoints. The E-star aware softswitch allows E-star compliant communications devices to enter and remain in power saving mode. The E-star aware softswitch spools messages and forwards only selected messages (e.g., calls) to the devices in power saving mode. When the E-star compliant communications devices exit power saving mode, the E-star aware softswitch forwards spooled messages.

  15. AGB [asymptotic giant branch]: Star evolution

    International Nuclear Information System (INIS)

    Becker, S.A.

    1987-01-01

    Asymptotic giant branch stars are red supergiant stars of low-to-intermediate mass. This class of stars is of particular interest because many of these stars can have nuclear processed material brought up repeatedly from the deep interior to the surface where it can be observed. A review of recent theoretical and observational work on stars undergoing the asymptotic giant branch phase is presented. 41 refs

  16. Star-Branched Polymers (Star Polymers)

    KAUST Repository

    Hirao, Akira; Hayashi, Mayumi; Ito, Shotaro; Goseki, Raita; Higashihara, Tomoya; Hadjichristidis, Nikolaos

    2015-01-01

    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

  17. The Diversity of Neutron Stars

    Science.gov (United States)

    Kaplan, David L.

    2004-12-01

    Neutron stars are invaluable tools for exploring stellar death, the physics of ultra-dense matter, and the effects of extremely strong magnetic fields. The observed population of neutron stars is dominated by the >1000 radio pulsars, but there are distinct sub-populations that, while fewer in number, can have significant impact on our understanding of the issues mentioned above. These populations are the nearby, isolated neutron stars discovered by ROSAT, and the central compact objects in supernova remnants. The studies of both of these populations have been greatly accelerated in recent years through observations with the Chandra X-ray Observatory and the XMM-Newton telescope. First, we discuss radio, optical, and X-ray observations of the nearby neutron stars aimed at determining their relation to the Galactic neutron star population and at unraveling their complex physical processes by determining the basic astronomical parameters that define the population---distances, ages, and magnetic fields---the uncertainties in which limit any attempt to derive basic physical parameters for these objects. We conclude that these sources are 1e6 year-old cooling neutron stars with magnetic fields above 1e13 Gauss. Second, we describe the hollow supernova remnant problem: why many of the supernova remnants in the Galaxy have no indication of central neutron stars. We have undertaken an X-ray census of neutron stars in a volume-limited sample of Galactic supernova remnants, and from it conclude that either many supernovae do not produce neutron stars contrary to expectation, or that neutron stars can have a wide range in cooling behavior that makes many sources disappear from the X-ray sky.

  18. RADIAL STABILITY IN STRATIFIED STARS

    International Nuclear Information System (INIS)

    Pereira, Jonas P.; Rueda, Jorge A.

    2015-01-01

    We formulate within a generalized distributional approach the treatment of the stability against radial perturbations for both neutral and charged stratified stars in Newtonian and Einstein's gravity. We obtain from this approach the boundary conditions connecting any two phases within a star and underline its relevance for realistic models of compact stars with phase transitions, owing to the modification of the star's set of eigenmodes with respect to the continuous case

  19. From clouds to stars

    International Nuclear Information System (INIS)

    Elmegreen, B.G.

    1982-01-01

    At the present time, the theory of star formation must be limited to what we know about the lowest density gas, or about the pre-main sequence stars themselves. We would like to understand two basic processes: 1) how star-forming clouds are created from the ambient interstellar gas in the first place, and 2) how small parts of these clouds condense to form individual stars. We are interested also in knowing what pre-main sequence stars are like, and how they can interact with their environment. These topics are reviewed in what follows. In this series of lectures, what we know about the formation of stars is tentatively described. The lectures begin with a description of the interstellar medium, and then they proceed along the same direction that a young star would follow during its creation, namely from clouds through the collapse phase and onto the proto-stellar phase. The evolution of viscous disks and two models for the formation of the solar system are described in the last lectures. The longest lectures, and the topics that are covered in most detail, are not necessarily the ones for which we have the most information. Physically intuitive explanations for the various processes are emphasized, rather then mathematical explanations. In some cases, the mathematical aspects are developed as well, but only when the equations can be used to give important numerical values for comparison with the observations

  20. Quark phases in neutron stars and a third family of compact stars as signature for phase transitions

    International Nuclear Information System (INIS)

    Schertler, K.; Greiner, C.; Schaffner-Bielich, J.; Thoma, M.H.

    2000-01-01

    The appearance of quark phases in the dense interior of neutron stars provides one possibility to soften the equation of state (EOS) of neutron star matter at high densities. This softening leads to more compact equilibrium configurations of neutron stars compared to pure hadronic stars of the same mass. We investigate the question to which amount the compactness of a neutron star can be attributed to the presence of a quark phase. For this purpose we employ several hadronic EOS in the framework of the relativistic mean-field (RMF) model and an extended MIT bag model to describe the quark phase. We find that -- almost independent of the model parameters -- the radius of a pure hadronic neutron star gets typically reduced by 20-30% if a pure quark phase in the center of the star does exist. For some EOS we furthermore find the possibility of a third family of compact stars which may exist besides the two known families of white dwarfs and neutron stars. We show how an experimental proof of the existence of a third family by mass and radius measurements may provide a unique signature for a phase transition inside neutron stars

  1. Star Formation Activity Beyond the Outer Arm. I. WISE -selected Candidate Star-forming Regions

    Energy Technology Data Exchange (ETDEWEB)

    Izumi, Natsuko; Yasui, Chikako; Saito, Masao [National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588 (Japan); Kobayashi, Naoto; Hamano, Satoshi, E-mail: natsuko.izumi@nao.ac.jp [Laboratory of Infrared High-resolution spectroscopy (LIH), Koyama Astronomical Observatory, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555 (Japan)

    2017-10-01

    The outer Galaxy beyond the Outer Arm provides a good opportunity to study star formation in an environment significantly different from that in the solar neighborhood. However, star-forming regions in the outer Galaxy have never been comprehensively studied or cataloged because of the difficulties in detecting them at such large distances. We studied 33 known young star-forming regions associated with 13 molecular clouds at R {sub G} ≥ 13.5 kpc in the outer Galaxy with data from the Wide-field Infrared Survey Explorer ( WISE ) mid-infrared all-sky survey. From their color distribution, we developed a simple identification criterion of star-forming regions in the outer Galaxy with the WISE color. We applied the criterion to all the WISE sources in the molecular clouds in the outer Galaxy at R {sub G} ≥ 13.5 kpc detected with the Five College Radio Astronomy Observatory (FCRAO) {sup 12}CO survey of the outer Galaxy, of which the survey region is 102.°49 ≤  l  ≤ 141.°54, −3.°03 ≤  b  ≤ 5.°41, and successfully identified 711 new candidate star-forming regions in 240 molecular clouds. The large number of samples enables us to perform the statistical study of star formation properties in the outer Galaxy for the first time. This study is crucial to investigate the fundamental star formation properties, including star formation rate, star formation efficiency, and initial mass function, in a primordial environment such as the early phase of the Galaxy formation.

  2. Fallen star legends and traditional religion of Japan: an aspect of star lore

    Science.gov (United States)

    Goto, Akira

    2015-08-01

    Japanese star lore is a complex mixture of animism, Buddhism, Shinto-ism, Confucianism and folk beliefs. Although some studies have been done on rituals concerning constellation developed in esoteric Buddhism (e.g. Journal Culture and Cosmos, Vol. 10 no 1 and 2), studies on other aspects of Japanese star lore are limited, in particular, to the English audience.In historic literatures, there often mentioned abnormal astronomical phenomena, such as, eclipse, meteors and comets. In this paper, I will discuss the possibility of reference to these astronomical phenomena in order to talk about some historical facts.In western part of Japan, there are Shinto shrines and Buddhistic temples that are said to be built as monuments of fallen stars. Usually fallen stars were divided into three, and a trio of shrines/temples are said to be the remnants of this phenomenon. Similar legends are found in Kudamatsu (that means "fallen pine=pine where stars fallen") of Yamaguchi Prefecture, Bisei-cho (that means "beautiful star") of Okayama Prefecture, Hoshida (that means "rice field or village of star") shrine of Osaka, and also Hoshida shrine of Nagoya.The purpose of this presentation is not to argue whether fallen star legend was truly astronomical phenomenon, such as, meteor or not. Instead, I will discuss why similar legends have been talked concerning the origin of particular shrines or temples. Citing Eliade who related gorge and alchemy producing spark to astronomical phenomena, I will disclose the possibility to relate these astronomical legends to the coming of the naturalized Japanese from Korean Peninsula who introducd forge to Japan abound 5 to 6 centuries.

  3. Wolf-Rayet stars and galactic structure

    International Nuclear Information System (INIS)

    Stenholm, B.

    1975-01-01

    A 15 0 wide strip along the galactic equator between longitudes 250 0 and 360 0 has been searched for Wolf-Rayet stars. Six new WR stars and four new planetary nebulae have been found. Seven stars earlier listed as WR stars have been rejected as such. The new WR stars in the 'Luminous Stars in the Southern Milky Way' are discussed. A sample of 154 WR stars has been treated statistically. For the distribution in longitude, comparisons are made with OB stars and classical cepheids. The differences in distribution are thought to be an age effect. An effort to explain the empty interval towards the anticentre is made. The distribution in latitude is compared with young clusters and long-period cepheids. The physical plane formed by these objects is tilted about one degree to the galactic plane and the tilt is upwards in the Cygnus direction. This result is also received by a least squares solution of the objects when given in rectangular coordinates. The WR star sample is regarded as fairly complete up to a distance of 5 kpc. (orig.) [de

  4. Life and death of the stars

    CERN Document Server

    Srinivasan, Ganesan

    2014-01-01

    This volume is devoted to one of the fascinating things about stars: how they evolve as they age. This evolution is different for stars of different masses. How stars end their lives when their supply of energy is exhausted also depends on their masses. Interestingly, astronomers conjectured about the ultimate fate of the stars even before the details of their evolution became clear. Part I of this book gives an account of the remarkable predictions made during the 1920s and 1930s concerning the ultimate fate of stars. Since much of this development hinged on quantum physics that emerged during this time, a detailed introduction to the relevant physics is included in the book. Part II is a summary of the life history of stars. This discussion is divided into three parts: low-mass stars, like our Sun, intermediate-mass stars, and massive stars. Many of the concepts of contemporary astrophysics were built on the foundation erected by Subrahmanyan Chandrasekhar in the 1930s. This book, written during his birth c...

  5. 76 FR 52288 - Airworthiness Directives; Rolls-Royce plc (RR) Trent 800 Series Turbofan Engines

    Science.gov (United States)

    2011-08-22

    ...-0836; Directorate Identifier 2010-NE-38-AD] RIN 2120-AA64 Airworthiness Directives; Rolls-Royce plc (RR... plc, P.O. Box 31, Derby, DE24 8BJ, United Kingdom: telephone 44 (0) 1332 242424; fax 44 (0) 1332... based on those comments. We will post all comments we receive, without change, to http://www.regulations...

  6. STAR FORMATION IN THE TAURUS FILAMENT L 1495: FROM DENSE CORES TO STARS

    International Nuclear Information System (INIS)

    Schmalzl, Markus; Kainulainen, Jouni; Henning, Thomas; Launhardt, Ralf; Quanz, Sascha P.; Alves, Joao; Goodman, Alyssa A.; Pineda, Jaime E.; Roman-Zuniga, Carlos G.

    2010-01-01

    We present a study of dense structures in the L 1495 filament in the Taurus Molecular Cloud and examine its star-forming properties. In particular, we construct a dust extinction map of the filament using deep near-infrared observations, exposing its small-scale structure in unprecedented detail. The filament shows highly fragmented substructures and a high mass-per-length value of M line = 17 M sun pc -1 , reflecting star-forming potential in all parts of it. However, a part of the filament, namely B 211, is remarkably devoid of young stellar objects. We argue that in this region the initial filament collapse and fragmentation is still taking place and star formation is yet to occur. In the star-forming part of the filament, we identify 39 cores with masses from 0.4 to 10 M sun and preferred separations in agreement with the local Jeans length. Most of these cores exceed the Bonnor-Ebert critical mass, and are therefore likely to collapse and form stars. The dense core mass function follows a power law with exponent Γ = 1.2 ± 0.2, a form commonly observed in star-forming regions.

  7. PHOTOMETRIC VARIABILITY IN KEPLER TARGET STARS: THE SUN AMONG STARS-A FIRST LOOK

    International Nuclear Information System (INIS)

    Basri, Gibor; Walkowicz, Lucianne M.; Batalha, Natalie; Jenkins, Jon; Borucki, William J.; Koch, David; Caldwell, Doug; Gilliland, Ronald L.; Dupree, Andrea K.; Latham, David W.; Meibom, Soeren; Howell, Steve; Brown, Tim

    2010-01-01

    The Kepler mission provides an exciting opportunity to study the light curves of stars with unprecedented precision and continuity of coverage. This is the first look at a large sample of stars with photometric data of a quality that has heretofore been only available for our Sun. It provides the first opportunity to compare the irradiance variations of our Sun to a large cohort of stars ranging from very similar to rather different stellar properties, at a wide variety of ages. Although Kepler data are in an early phase of maturity, and we only analyze the first month of coverage, it is sufficient to garner the first meaningful measurements of our Sun's variability in the context of a large cohort of main-sequence stars in the solar neighborhood. We find that nearly half of the full sample is more active than the active Sun, although most of them are not more than twice as active. The active fraction is closer to a third for the stars most similar to the Sun, and rises to well more than half for stars cooler than mid-K spectral types.

  8. The origin of Wolf-Rayet stars

    International Nuclear Information System (INIS)

    Doom, C.

    1987-01-01

    The paper reviews the origin of Wolf-Rayet (WR) stars, with emphasis on the so-called Population I WR stars which are associated with the young and luminous stellar population. A description is given of the observational characteristics i.e. classification, luminosities composition, etc. of WR stars. The origin and evolution of WR stars is described, including the single, binary, subtypes and ratio WR/O. The interaction of the WR stars with their environment is discussed with respect to the energy deposition and composition anomalies. A brief account of the discovery of WR stars in other galaxies is given. Finally, some of the main issues in the research into the structure and evolution of WR stars are outlined. (U.K.)

  9. 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...

  10. Connecting the Cosmic Star Formation Rate with the Local Star Formation

    Science.gov (United States)

    Gribel, Carolina; Miranda, Oswaldo D.; Williams Vilas-Boas, José

    2017-11-01

    We present a model that unifies the cosmic star formation rate (CSFR), obtained through the hierarchical structure formation scenario, with the (Galactic) local star formation rate (SFR). It is possible to use the SFR to generate a CSFR mapping through the density probability distribution functions commonly used to study the role of turbulence in the star-forming regions of the Galaxy. We obtain a consistent mapping from redshift z˜ 20 up to the present (z = 0). Our results show that the turbulence exhibits a dual character, providing high values for the star formation efficiency ( ˜ 0.32) in the redshift interval z˜ 3.5{--}20 and reducing its value to =0.021 at z = 0. The value of the Mach number ({{ M }}{crit}), from which rapidly decreases, is dependent on both the polytropic index (Γ) and the minimum density contrast of the gas. We also derive Larson’s first law associated with the velocity dispersion ( ) in the local star formation regions. Our model shows good agreement with Larson’s law in the ˜ 10{--}50 {pc} range, providing typical temperatures {T}0˜ 10{--}80 {{K}} for the gas associated with star formation. As a consequence, dark matter halos of great mass could contain a number of halos of much smaller mass, and be able to form structures similar to globular clusters. Thus, Larson’s law emerges as a result of the very formation of large-scale structures, which in turn would allow the formation of galactic systems, including our Galaxy.

  11. Dark stars

    DEFF Research Database (Denmark)

    Maselli, Andrea; Pnigouras, Pantelis; Nielsen, Niklas Grønlund

    2017-01-01

    to the formation of compact objects predominantly made of dark matter. Considering both fermionic and bosonic (scalar φ4) equations of state, we construct the equilibrium structure of rotating dark stars, focusing on their bulk properties and comparing them with baryonic neutron stars. We also show that these dark......Theoretical models of self-interacting dark matter represent a promising answer to a series of open problems within the so-called collisionless cold dark matter paradigm. In case of asymmetric dark matter, self-interactions might facilitate gravitational collapse and potentially lead...... objects admit the I-Love-Q universal relations, which link their moments of inertia, tidal deformabilities, and quadrupole moments. Finally, we prove that stars built with a dark matter equation of state are not compact enough to mimic black holes in general relativity, thus making them distinguishable...

  12. Analysis of R-R intervals in patients with atrial fibrillation at rest and during exercise

    NARCIS (Netherlands)

    Bootsma, B.K.; Hoelen, A.J.; Strackee, J.; Meijler, F.L.

    Serial autocorrelation functions and histograms of R-R intervals in patients with atrial fibrillation, with and without digitalis, at rest and during exercise, were produced by a computer. At rest with and without digitalis the first and higher order coefficients did not differ from zero. During

  13. Rodent Research-1 (RR1) NASA Validation Flight: Mouse extensor digitorum longus muscle transcriptomic and epigenomic data

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA s Rodent Research (RR) project is playing a critical role in advancing biomedical research on the physiological effects of space environments. Due to the...

  14. Rodent Research-1 (RR1) NASA Validation Flight: Mouse tibialis anterior muscle transcriptomic proteomic and epigenomic data

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA s Rodent Research (RR) project is playing a critical role in advancing biomedical research on the physiological effects of space environments. Due to the...

  15. SX Phoenicis stars

    International Nuclear Information System (INIS)

    Nemec, J.; Mateo, M.

    1990-01-01

    The purpose of this paper is to review the basic observational information concerning SX Phe stars, including recent findings such as the discovery of about 40 low-luminosity variable stars in the Carina dwarf galaxy and identification of at least one SX Phe star in the metal-rich globular cluster M71. Direct evidence supporting the hypothesis that at least some BSs are binary systems comes from the discovery of two contact binaries and a semidetached binary among the 50 BSs in the globular cluster NGC 5466. Since these systems will coalesce on a time scale 500 Myr, it stands to reason that many (if not most) BSs are coalesced binaries. The merger hypothesis also explains the relatively-large masses (1.0-1.2 solar masses) that have been derived for SX Phe stars and halo BSs, and may also account for the nonvariable BSs in the 'SX Phe instability strip'. 132 refs

  16. Distances of Dwarf Carbon Stars

    Science.gov (United States)

    Harris, Hugh C.; Dahn, Conard C.; Subasavage, John P.; Munn, Jeffrey A.; Canzian, Blaise J.; Levine, Stephen E.; Monet, Alice B.; Pier, Jeffrey R.; Stone, Ronald C.; Tilleman, Trudy M.; Hartkopf, William I.

    2018-06-01

    Parallaxes are presented for a sample of 20 nearby dwarf carbon stars. The inferred luminosities cover almost two orders of magnitude. Their absolute magnitudes and tangential velocities confirm prior expectations that some originate in the Galactic disk, although more than half of this sample are halo stars. Three stars are found to be astrometric binaries, and orbital elements are determined; their semimajor axes are 1–3 au, consistent with the size of an AGB mass-transfer donor star.

  17. Discovery of a New Nearby Star

    Science.gov (United States)

    Teegarden, B. J.; Pravdo, S. H.; Covey, K.; Frazier, O.; Hawley, S. L.; Hicks, M.; Lawrence, K.; McGlynn, T.; Reid, I. N.; Shaklan, S. B.

    2003-01-01

    We report the discovery of a nearby star with a very large proper motion of 5.06 +/- 0.03 arcsec/yr. The star is called SO025300.5+165258 and referred to herein as HPMS (high proper motion star). The discovery came as a result of a search of the SkyMorph database, a sensitive and persistent survey that is well suited for finding stars with high proper motions. There are currently only 7 known stars with proper motions greater than 5 arcsec/yr. We have determined a preliminary value for the parallax of pi = 0.43 +/- 0.13 arcsec. If this value holds our new star ranks behind only the Alpha Centauri system (including Proxima Centauri) and Barnard's star in the list of our nearest stellar neighbours. The spectrum and measured tangential velocity indicate that HPMS is a main-sequence star with spectral type M6.5. However, if our distance measurement is correct, the HPMS is underluminous by 1.2 +/- 0.7 mag.

  18. Star trackers for attitude determination

    DEFF Research Database (Denmark)

    Liebe, Carl Christian

    1995-01-01

    One problem comes to all spacecrafts using vector information. That is the problem of determining the attitude. This paper describes how the area of attitude determination instruments has evolved from simple pointing devices into the latest technology, which determines the attitude by utilizing...... a CCD camera and a powerful microcomputer. The instruments are called star trackers and they are capable of determining the attitude with an accuracy better than 1 arcsecond. The concept of the star tracker is explained. The obtainable accuracy is calculated, the numbers of stars to be included...... in the star catalogue are discussed and the acquisition of the initial attitude is explained. Finally the commercial market for star trackers is discussed...

  19. THE CLASSIFICATION OF KEPLER B-STAR VARIABLES

    International Nuclear Information System (INIS)

    McNamara, Bernard J.; Jackiewicz, Jason; McKeever, Jean

    2012-01-01

    The light curves of 252 B-star candidates in the Kepler database are analyzed in a similar fashion to that done by Balona et al. to further characterize B-star variability, increase the sample of variable B stars for future study, and to identify stars whose power spectra include particularly interesting features such as frequency groupings. Stars are classified as either constant light emitters, β Cep stars, slowly pulsating B stars (SPBs), hybrid pulsators, binaries or stars whose light curves are dominated by rotation (Bin/Rot), hot subdwarfs, or white dwarfs. One-hundred stars in our sample were found to be either light constants or to be variable at a level of less than 0.02 mmag. We increase the number of candidate B-star variables found in the Kepler database by Balona et al. in the following fashion: β Cep stars from 0 to 10, SPBs from eight to 54, hybrid pulsators from seven to 21, and Bin/Rot stars from 23 to 82. For comparison purposes, approximately 51 SPBs and six hybrids had been known prior to 2007. The number of β Cep stars known prior to 2004 was 93. A secondary result of this study is the identification of an additional 11 pulsating white dwarf candidates, four of which possess frequency groupings.

  20. Stars get dizzy after lunch

    International Nuclear Information System (INIS)

    Zhang, Michael; Penev, Kaloyan

    2014-01-01

    Exoplanet searches have discovered a large number of h ot Jupiters — high-mass planets orbiting very close to their parent stars in nearly circular orbits. A number of these planets are sufficiently massive and close-in to be significantly affected by tidal dissipation in the parent star, to a degree parameterized by the tidal quality factor Q * . This process speeds up their star's rotation rate while reducing the planet's semimajor axis. In this paper, we investigate the tidal destruction of hot Jupiters. Because the orbital angular momenta of these planets are a significant fraction of their star's rotational angular momenta, they spin up their stars significantly while spiraling to their deaths. Using the Monte Carlo simulation, we predict that for Q * = 10 6 , 3.9 × 10 –6 of stars with the Kepler Target Catalog's mass distribution should have a rotation period shorter than 1/3 day (8 hr) due to accreting a planet. Exoplanet surveys such as SuperWASP, HATnet, HATsouth, and KELT have already produced light curves of millions of stars. These two facts suggest that it may be possible to search for tidally destroyed planets by looking for stars with extremely short rotational periods, then looking for remnant planet cores around those candidates, anomalies in the metal distribution, or other signatures of the recent accretion of the planet.

  1. Insights from simulations of star formation

    International Nuclear Information System (INIS)

    Larson, Richard B

    2007-01-01

    Although the basic physics of star formation is classical, numerical simulations have yielded essential insights into how stars form. They show that star formation is a highly nonuniform runaway process characterized by the emergence of nearly singular peaks in density, followed by the accretional growth of embryo stars that form at these density peaks. Circumstellar discs often form from the gas being accreted by the forming stars, and accretion from these discs may be episodic, driven by gravitational instabilities or by protostellar interactions. Star-forming clouds typically develop filamentary structures, which may, along with the thermal physics, play an important role in the origin of stellar masses because of the sensitivity of filament fragmentation to temperature variations. Simulations of the formation of star clusters show that the most massive stars form by continuing accretion in the dense cluster cores, and this again is a runaway process that couples star formation and cluster formation. Star-forming clouds also tend to develop hierarchical structures, and smaller groups of forming objects tend to merge into progressively larger ones, a generic feature of self-gravitating systems that is common to star formation and galaxy formation. Because of the large range of scales and the complex dynamics involved, analytic models cannot adequately describe many aspects of star formation, and detailed numerical simulations are needed to advance our understanding of the subject. 'The purpose of computing is insight, not numbers.' Richard W Hamming, in Numerical Methods for Scientists and Engineers (1962) 'There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy.' William Shakespeare, in Hamlet, Prince of Denmark (1604) (key issues review)

  2. Insights from simulations of star formation

    Energy Technology Data Exchange (ETDEWEB)

    Larson, Richard B [Department of Astronomy, Yale University, Box 208101, New Haven, CT 06520-8101 (United States)

    2007-03-15

    Although the basic physics of star formation is classical, numerical simulations have yielded essential insights into how stars form. They show that star formation is a highly nonuniform runaway process characterized by the emergence of nearly singular peaks in density, followed by the accretional growth of embryo stars that form at these density peaks. Circumstellar discs often form from the gas being accreted by the forming stars, and accretion from these discs may be episodic, driven by gravitational instabilities or by protostellar interactions. Star-forming clouds typically develop filamentary structures, which may, along with the thermal physics, play an important role in the origin of stellar masses because of the sensitivity of filament fragmentation to temperature variations. Simulations of the formation of star clusters show that the most massive stars form by continuing accretion in the dense cluster cores, and this again is a runaway process that couples star formation and cluster formation. Star-forming clouds also tend to develop hierarchical structures, and smaller groups of forming objects tend to merge into progressively larger ones, a generic feature of self-gravitating systems that is common to star formation and galaxy formation. Because of the large range of scales and the complex dynamics involved, analytic models cannot adequately describe many aspects of star formation, and detailed numerical simulations are needed to advance our understanding of the subject. 'The purpose of computing is insight, not numbers.' Richard W Hamming, in Numerical Methods for Scientists and Engineers (1962) 'There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy.' William Shakespeare, in Hamlet, Prince of Denmark (1604) (key issues review)

  3. Evolution of massive close binary stars

    International Nuclear Information System (INIS)

    Masevich, A.G.; Tutukov, A.V.

    1982-01-01

    Some problems of the evolution of massive close binary stars are discussed. Most of them are nonevolutionized stars with close masses of components. After filling the Roche cavity and exchange of matter between the components the Wolf-Rayet star is formed. As a result of the supernovae explosion a neutron star or a black hole is formed in the system. The system does not disintegrate but obtains high space velocity owing to the loss of the supernovae envelope. The satellite of the neutron star or black hole - the star of the O or B spectral class loses about 10 -6 of the solar mass for a year. Around the neighbouring component a disc of this matter is formed the incidence of which on a compact star leads to X radiation appearance. The neutron star cannot absorb the whole matter of the widening component and the binary system submerges into the common envelope. As a result of the evolution of massive close binary systems single neutron stars can appear which after the lapse of some time become radiopulsars. Radiopulsars with such high space velocities have been found in our Galaxy [ru

  4. Wolf-Rayet Stars in Starburst Galaxies

    OpenAIRE

    Mas-Hesse, J. Miguel; Kunth, Daniel; Cervino, Miguel

    1999-01-01

    Wolf-Rayet stars have been detected in a large number of galaxies experiencing intense bursts of star formation. All stars initially more massive than a certain, metallicity-dependent, value are believed to experience the Wolf-Rayet phase at the end of their evolution, just before collapsing in supernova explosion. The detection of Wolf-Rayet stars puts therefore important constraints on the evolutionary status of starbursts, the properties of their Initial Mass Functions and their star forma...

  5. Carbon stars in lmc clusters revisited

    OpenAIRE

    Marigo, Paola; Girardi, Leo Alberto; Chiosi, Cesare

    1996-01-01

    Examining the available data for AGB stars in the Large Magellanic Cloud (LMC) clusters, we address the question about the mass interval of low- and intermediate-mass stars which eventually evolve into carbon stars (C stars) during the TP-AGB phase. We combine the data compiled by Frogel, Mould & Blanco (1990) - near infrared photometry and spectral classification for luminous AGB stars in clusters - with the ages for individual clusters derived from independent methods. The resulting distrib...

  6. Comparing the asteroseismic properties of pulsating extremely low-mass pre-white dwarf stars and δ Scuti stars

    Directory of Open Access Journals (Sweden)

    Arias J.P.Sánchez

    2017-01-01

    Full Text Available We present the first results of a detailed comparison between the pulsation properties of pulsating Extremely Low-Mass pre-white dwarf stars (the pre-ELMV variable stars and δ Scuti stars. The instability domains of these very different kinds of stars nearly overlap in the log Teff vs. log g diagram, leading to a degeneracy in the classification of the stars. Our aim is to provide asteroseismic tools for their correct classification.

  7. CCD Photometry Using Multiple Comparison Stars

    Directory of Open Access Journals (Sweden)

    Yonggi Kim

    2004-09-01

    Full Text Available The accuracy of CCD observations obtained at the Korean 1.8 m telescope has been studied. Seventeen comparison stars in the vicinity of the cataclysmic variable BG CMi have been measured. The ``artificial" star has been used instead of the ``control" star, what made possible to increase accuracy estimates by a factor of 1.3-2.1 times for ``good" and ``cloudy" nights, respectively. The algorithm of iterative determination of accuracy and weights of few comparison stars contributing to the artificial star, has been presented. The accuracy estimates for 13-mag stars are around 0.002 m mag for exposure times of 30 sec.

  8. Hyperon-mixed neutron stars

    International Nuclear Information System (INIS)

    Takatsuka, Tatsuyuki

    2004-01-01

    Hyperon mixing in neutron star matter is investigated by the G-matrix-based effective interaction approach under the attention to use the YN and the YY potentials compatible with hypernuclear data and is shown to occur at densities relevant to neutron star cores, together with discussions to clarify the mechanism of hyperon contamination. It is remarked that developed Y-mixed phase causes a dramatic softening of the neutron star equation of state and leads to the serious problem that the resulting maximum mass M max for neutron star model contradicts the observed neutron star mass (M max obs = 1.44 M Θ ), suggesting the necessity of some extra repulsion'' in hypernuclear system. It is shown that the introduction of three-body repulsion similar to that in nuclear system can resolve the serious situation and under the consistency with observation (M max > M obs ) the threshold densities for Λ and Σ - are pushed to higher density side, from 2ρ 0 to ∼ 4ρ 0 (ρ 0 being the nuclear density). On the basis of a realistic Y-mixed neutron star model, occurrence of Y-superfluidity essential for ''hyperon cooling'' scenario is studied and both of Λ- and Σ - -superfluids are shown to be realized with their critical temperatures 10 8-9 K, meaning that the hyperon cooling'' is a promising candidate for a fast non-standard cooling demanded for some neutron stars with low surface temperature. A comment is given as to the consequence of less attractive ΛΛ interaction suggested by the ''NAGARA event'' ΛΛ 6 He. (author)

  9. Terminal velocities for a large sample of O stars, B supergiants, and Wolf-Rayet stars

    International Nuclear Information System (INIS)

    Prinja, R.K.; Barlow, M.J.; Howarth, I.D.

    1990-01-01

    It is argued that easily measured, reliable estimates of terminal velocities for early-type stars are provided by the central velocity asymptotically approached by narrow absorption features and by the violet limit of zero residual intensity in saturated P Cygni profiles. These estimators are used to determine terminal velocities, v(infinity), for 181 O stars, 70 early B supergiants, and 35 Wolf-Rayet stars. For OB stars, the values are typically 15-20 percent smaller than the extreme violet edge velocities, v(edge), while for WR stars v(infinity) = 0.76 v(edge) on average. New mass-loss rates for WR stars which are thermal radio emitters are given, taking into account the new terminal velocities and recent revisions to estimates of distances and to the mean nuclear mass per electron. The relationships between v(infinity), the surface escape velocities, and effective temperatures are examined. 67 refs

  10. Astronomy of binary and multiple stars

    International Nuclear Information System (INIS)

    Tokovinin, A.A.

    1984-01-01

    Various types of binary stars and methods for their observation are described in a popular form. Some models of formation and evolution of binary and multiple star systems are presented. It is concluded that formation of binary and multiple stars is a regular stage in the process of star production

  11. The WO Wolf-Rayet stars

    International Nuclear Information System (INIS)

    Barlow, M.J.

    1982-01-01

    Sanduleak (1971) has listed five stars, not apparently associated with planetary nebulae, which show very strong O VI 3811.34 A emission. He pointed out that two of them are in the Magellanic Clouds and have absolute magnitudes comparable to those of classical (Population I) Wolf-Rayet stars. O VI emission is known to occur in some classical Wolf-Rayet stars, but not with the extreme strength shown by the Sanduleak stars. The authors have obtained absolute optical spectrophotometry (3100 - 7400 A) of all five of these stars, using the UCL Image Photon Counting System and RGO Spectrograph on the Anglo-Australian Telescope. Their relative flux distributions are shown. Inspection shows that Sand 1 is very lightly reddened, Sand 2 and 3 have intermediate reddening, and Sand 4 and 5 are heavily reddened. IUE ultraviolet spectrophotometry has been obtained of the first three stars; Sand 4 and 5 are too heavily reddened for IUE spectra to be feasible. (Auth.)

  12. Neutron star pulsations and instabilities

    International Nuclear Information System (INIS)

    Lindblom, L.

    2001-01-01

    Gravitational radiation (GR) drives an instability in certain modes of rotating stars. This instability is strong enough in the case of the r-modes to cause their amplitudes to grow on a timescale of tens of seconds in rapidly rotating neutron stars. GR emitted by these modes removes angular momentum from the star at a rate which would spin it down to a relatively small angular velocity within about one year, if the dimensionless amplitude of the mode grows to order unity. A pedagogical level discussion is given here on the mechanism of GR instability in rotating stars, on the relevant properties of the r-modes, and on our present understanding of the dissipation mechanisms that tend to suppress this instability in neutron stars. The astrophysical implications of this GR driven instability are discussed for young neutron stars, and for older systems such as low mass x-ray binaries. Recent work on the non-linear evolution of the r-modes is also presented. (author)

  13. Prediction of paroxysmal atrial fibrillation using recurrence plot-based features of the RR-interval signal

    International Nuclear Information System (INIS)

    Mohebbi, Maryam; Ghassemian, Hassan

    2011-01-01

    Atrial fibrillation (AF) is the most common cardiac arrhythmia and increases the risk of stroke. Predicting the onset of paroxysmal AF (PAF), based on noninvasive techniques, is clinically important and can be invaluable in order to avoid useless therapeutic intervention and to minimize risks for the patients. In this paper, we propose an effective PAF predictor which is based on the analysis of the RR-interval signal. This method consists of three steps: preprocessing, feature extraction and classification. In the first step, the QRS complexes are detected from the electrocardiogram (ECG) signal and then the RR-interval signal is extracted. In the next step, the recurrence plot (RP) of the RR-interval signal is obtained and five statistically significant features are extracted to characterize the basic patterns of the RP. These features consist of the recurrence rate, length of longest diagonal segments (L max  ), average length of the diagonal lines (L mean ), entropy, and trapping time. Recurrence quantification analysis can reveal subtle aspects of dynamics not easily appreciated by other methods and exhibits characteristic patterns which are caused by the typical dynamical behavior. In the final step, a support vector machine (SVM)-based classifier is used for PAF prediction. The performance of the proposed method in prediction of PAF episodes was evaluated using the Atrial Fibrillation Prediction Database (AFPDB) which consists of both 30 min ECG recordings that end just prior to the onset of PAF and segments at least 45 min distant from any PAF events. The obtained sensitivity, specificity, positive predictivity and negative predictivity were 97%, 100%, 100%, and 96%, respectively. The proposed methodology presents better results than other existing approaches

  14. Comparison of spontaneous vs. metronome-guided breathing on assessment of vagal modulation using RR variability.

    Science.gov (United States)

    Bloomfield, D M; Magnano, A; Bigger, J T; Rivadeneira, H; Parides, M; Steinman, R C

    2001-03-01

    R-R interval variability (RR variability) is increasingly being used as an index of autonomic activity. High-frequency (HF) power reflects vagal modulation of the sinus node. Since vagal modulation occurs at the respiratory frequency, some investigators have suggested that HF power cannot be interpreted unless the breathing rate is controlled. We hypothesized that HF power during spontaneous breathing would not differ significantly from HF power during metronome-guided breathing. We measured HF power during spontaneous breathing in 20 healthy subjects and 19 patients with heart disease. Each subject's spontaneous breathing rate was determined, and the calculation of HF power was repeated with a metronome set to his or her average spontaneous breathing rate. There was no significant difference between the logarithm of HF power measured during spontaneous and metronome-guided breathing [4.88 +/- 0.29 vs. 5.29 +/- 0.30 ln(ms(2)), P = 0.32] in the group as a whole and when patients and healthy subjects were examined separately. We did observe a small (9.9%) decrease in HF power with increasing metronome-guided breathing rates (from 9 to 20 breaths/min). These data indicate that HF power during spontaneous and metronome-guided breathing differs at most by very small amounts. This variability is several logarithmic units less than the wide discrepancies observed between healthy subjects and cardiac patients with a heterogeneous group of cardiovascular disorders. In addition, HF power is relatively constant across the range of typical breathing rates. These data indicate that there is no need to control breathing rate to interpret HF power when RR variability (and specifically HF power) is used to identify high-risk cardiac patients.

  15. How massive the Wolf-Rayet stars are

    International Nuclear Information System (INIS)

    Niemela, V.S.

    1981-01-01

    If the Wolf-Rayet stars are produced by the evolution of massive stars with mass loss (Paczynski 1967, Conti 1976) from O stars to WN stars and thereafter to WC stars, then we may expect to observe a correlation of decreasing mean masses in the same sense as the evolution. Information about the masses of WR stars are obtained from studies of binary systems with WR components. (Auth.)

  16. RETIRED A STARS AND THEIR COMPANIONS. III. COMPARING THE MASS-PERIOD DISTRIBUTIONS OF PLANETS AROUND A-TYPE STARS AND SUN-LIKE STARS

    International Nuclear Information System (INIS)

    Bowler, Brendan P.; Johnson, John Asher; Liu, Michael C.; Marcy, Geoffrey W.; Peek, Kathryn M. G.; Henry, Gregory W.; Fischer, Debra A.; Clubb, Kelsey I.; Reffert, Sabine; Schwab, Christian; Lowe, Thomas B.

    2010-01-01

    We present an analysis of ∼5 years of Lick Observatory radial velocity measurements targeting a uniform sample of 31 intermediate-mass (IM) subgiants (1.5 ∼ * /M sun ∼ +9 -8 %, which is significantly higher than the 5%-10% frequency observed around solar-mass stars. The median detection threshold for our sample includes minimum masses down to {0.2, 0.3, 0.5, 0.6, 1.3} M Jup within {0.1, 0.3, 0.6, 1.0, 3.0} AU. To compare the properties of planets around IM stars to those around solar-mass stars we synthesize a population of planets based on the parametric relationship dN ∝ M α P β dlnMdlnP, the observed planet frequency, and the detection limits we derived. We find that the values of α and β for planets around solar-type stars from Cumming et al. fail to reproduce the observed properties of planets in our sample at the 4σ level, even when accounting for the different planet occurrence rates. Thus, the properties of planets around A stars are markedly different than those around Sun-like stars, suggesting that only a small (∼50%) increase in stellar mass has a large influence on the formation and orbital evolution of planets.

  17. Flares on a Bp Star

    Science.gov (United States)

    Mullan, D. J.

    2009-09-01

    Two large X-ray flares have been reported from the direction of a magnetic B2p star (σ Ori E). Sanz-Forcada et al. have suggested that the flares did not occur on the B2p star but on a companion of late spectral type. A star which is a candidate for a late-type flare star near σ Ori E has recently been identified by Bouy et al. However, based on the properties of the flares, and based on a recent model of rotating magnetospheres, we argue that, rather than attributing the two flares to a late-type dwarf, it is a viable hypothesis that the flares were magnetic phenomena associated with the rotating magnetosphere of the B2p star itself.

  18. FLARES ON A Bp STAR

    International Nuclear Information System (INIS)

    Mullan, D. J.

    2009-01-01

    Two large X-ray flares have been reported from the direction of a magnetic B2p star (σ Ori E). Sanz-Forcada et al. have suggested that the flares did not occur on the B2p star but on a companion of late spectral type. A star which is a candidate for a late-type flare star near σ Ori E has recently been identified by Bouy et al. However, based on the properties of the flares, and based on a recent model of rotating magnetospheres, we argue that, rather than attributing the two flares to a late-type dwarf, it is a viable hypothesis that the flares were magnetic phenomena associated with the rotating magnetosphere of the B2p star itself.

  19. Evolution of star systems supplied by external stars: a model for Galaxy nuclei

    International Nuclear Information System (INIS)

    Dokuchaev, V.I.; Ozernoj, L.M.; AN SSSR, Moscow. Inst. Yadernykh Issledovanij)

    1985-01-01

    Extended rarefied environments around the core of a non-isothermic galaxy nucleus can supply the core by both energies and masses of external stars due to relaxation mechanisms. These factors can influence considerably the secular evolution of the core when competing with usual star evaporation from it. Conditions are found under which external environments influence the core evolution much more than star evaporation. This results in expansion of the core instead of its collapse

  20. Evolution of massive stars

    International Nuclear Information System (INIS)

    Loore, C. de

    1984-01-01

    The evolution of stars with masses larger than 15 sun masses is reviewed. These stars have large convective cores and lose a substantial fraction of their matter by stellar wind. The treatment of convection and the parameterisation of the stellar wind mass loss are analysed within the context of existing disagreements between theory and observation. The evolution of massive close binaries and the origin of Wolf-Rayet Stars and X-ray binaries is also sketched. (author)

  1. ENERGY STAR Certified Telephones

    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 Telephony (cordless telephones and VoIP...

  2. Luminosity Variations in Post-AGB Stars

    Science.gov (United States)

    Mesler, Robert; Henson, G.

    2007-12-01

    Although much is known about AGB stars and planetary nebulae, relatively little is known about the phase of a star's life in which it transitions between those two states. We have measured the variations in luminosity of a sample of known Post-AGB stars (as well as several candidates) relative to nearby, non-variable stars in order to compare them with theoretical models. The typical behavior of the observed variations is described and an attempt is made to discern whether any periodicity might be present. Luminosity variations were found to be on the order of a few hundredths to a few tenths of a magnitude for the stars that were surveyed, with occasional fluctuations of up to a magnitude. This agrees with current models of Post-AGB stars. Each star fell into one of three categories, which were termed groups 1, 2, and 3. Group 1 stars showed long term, non-periodic luminosity variations on the scale of weeks or longer and were most likely to display some sort of short term, coherent luminosity oscillation (each of which lasted for only a few cycles). Group 2 stars showed erratic, short-term magnitude variations occurring on scales of several days. Group 3 stars showed little or no variation in magnitude. Of the 27 Post-AGB stars that were sampled, five fell into group 1, fifteen fell into group 2, and seven fell into group 3. The luminosity variations tended to be color-independent, and occurred on timescales ranging nearly continuously from a few days to more than a year. No clear periodic behavior was found in any star in our sample. This project was funded by a partnership between the National Science Foundation (NSF AST-0552798), Research Experiences for Undergraduates (REU), and the Department of Defense (DoD) ASSURE (Awards to Stimulate and Support Undergraduate Research Experiences) programs.

  3. Classification of O Stars in the Yellow-Green: The Exciting Star VES 735

    Science.gov (United States)

    Kerton, C. R.; Ballantyne, D. R.; Martin, P. G.

    1999-05-01

    Acquiring data for spectral classification of heavily reddened stars using traditional criteria in the blue-violet region of the spectrum can be prohibitively time consuming using small to medium sized telescopes. One such star is the Vatican Observatory emission-line star VES 735, which we have found excites the H II region KR 140. In order to classify VES 735, we have constructed an atlas of stellar spectra of O stars in the yellow-green (4800-5420 Å). We calibrate spectral type versus the line ratio He I lambda4922:He II lambda5411, showing that this ratio should be useful for the classification of heavily reddened O stars associated with H II regions. Application to VES 735 shows that the spectral type is O8.5. The absolute magnitude suggests luminosity class V. Comparison of the rate of emission of ionizing photons and the bolometric luminosity of VES 735, inferred from radio and infrared measurements of the KR 140 region, to recent stellar models gives consistent evidence for a main-sequence star of mass 25 M_solar and age less than a few million years with a covering factor 0.4-0.5 by the nebular material. Spectra taken in the red (6500-6700 Å) show that the stellar Hα emission is double-peaked about the systemic velocity and slightly variable. Hβ is in absorption, so that the emission-line classification is ``(e)''. However, unlike the case of the more well-known O(e) star zeta Oph, the emission from VES 735 appears to be long-lived rather than episodic.

  4. Rotational velocities of low-mass stars

    International Nuclear Information System (INIS)

    Stauffer, J.B.; Hartmann, L.W.; Harvard-Smithsonian Center for Astrophysics, Cambridge, MA)

    1986-01-01

    The rotational velocities of stars provide important clues to how stars form and evolve. Yet until recently, studies of stellar rotation were limited to stars more massive than the sun. This is beginning to change, and an observational outline of the rotational velocity evolution of stars less massive than the sun can now be provided. Low-mass stars rotate slowly during the early stages of premain-sequence evolution, and spin up as they contract to the main sequence. This spin-up culminates in a brief period of very rapid rotation at an age of order 50 million years. Physical interpretation of this increase in rotation and the subsequent main-sequence spin-down are complicated by the possibility of differential internal rotation. The observed rapidity of spin-down among G dwarfs suggests that initially only the outer convective envelopes of these stars are slowed. The data suggest an intrinsic spread in angular momentum among young stars of the same mass and age, a spread which is apparently minimized by the angular-momentum loss mechanism in old low-mass stars. 83 references

  5. Moments of inertia of neutron stars

    Energy Technology Data Exchange (ETDEWEB)

    Greif, Svenja Kim; Hebeler, Kai; Schwenk, Achim [Institut fuer Kernphysik, Technische Universitaet Darmstadt (Germany); ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum fuer Schwerionenforschung GmbH (Germany)

    2016-07-01

    Neutron stars are unique laboratories for matter at extreme conditions. While nuclear forces provide systematic constraints on properties of neutron-rich matter up to around nuclear saturation density, the composition of matter at high densities is still unknown. Recent precise observations of 2 M {sub CircleDot} neutron stars made it possible to derive systematic constraints on the equation of state at high densities and also neutron star radii. Further improvements of these constraints require the observation of even heavier neutron stars or a simultaneous measurement of mass and radius of a single neutron star. Since the precise measurement of neutron star radii is an inherently difficult problem, the observation of moment of inertia of neutron stars provides a promising alternative, since they can be measured by pulsar timing experiments. We present a theoretical framework that allows to calculate moments of inertia microscopically, we show results based on state of the art equations of state and illustrate how future measurements of moments of inertia allow to constrain the equation of state and other properties of neutron stars.

  6. Supernovae from massive AGB stars

    NARCIS (Netherlands)

    Poelarends, A.J.T.; Izzard, R.G.; Herwig, F.; Langer, N.; Heger, A.

    2006-01-01

    We present new computations of the final fate of massive AGB-stars. These stars form ONeMg cores after a phase of carbon burning and are called Super AGB stars (SAGB). Detailed stellar evolutionary models until the thermally pulsing AGB were computed using three di erent stellar evolution codes. The

  7. Qualidade fisiológica de sementes de soja convencional e transgênica RR produzidas sob aplicação foliar de manganês

    Directory of Open Access Journals (Sweden)

    Everson Reis Carvalho

    2014-09-01

    Full Text Available Sementes de soja com alta qualidade fisiológica são essenciais à obtenção de produtividade elevada e um dos fatores que afetam a produção de sementes é a nutrição mineral. O objetivo neste trabalho foi avaliar o efeito da aplicação foliar de manganês, em diferentes doses e estádios de aplicação, na qualidade fisiológica de sementes de soja, em cultivares convencionais e em suas derivadas transgênicas RR, com distintos teores de lignina do tegumento. O ensaio foi conduzido em blocos casualizados, com três repetições e esquema fatorial 4 x 4 x 2, sendo quatro cultivares de soja, duas convencionais e suas derivadas transgênicas RR (BRS Celeste e BRS Baliza RR; BRSGO Jataí e BRS Silvânia RR, quatro doses de Mn via foliar (0; 200; 400 e 600 g Mn ha-1 e dois estádios de aplicação (R1 e R3. A qualidade fisiológica das sementes foi estimada, antes e após seis meses de armazenamento, por meio dos testes: Germinação, Envelhecimento acelerado, Emergência de plântulas, Condutividade elétrica e Tetrazólio (Viabilidade, vigor e danos mecânicos. Realizou-se também a quantificação de lignina no tegumento das sementes. A aplicação foliar de Mn proporciona incrementos na qualidade fisiológica nas sementes de soja produzidas. Sementes das cultivares de soja Celeste e Baliza RR apresentam melhor qualidade fisiológica quando comparadas às de Jataí e Silvânia RR. Sementes de cultivares de soja com maior teor de lignina no tegumento não apresentam necessariamente melhor qualidade fisiológica, sendo a qualidade das sementes relacionada a outros fatores intrínsecos ao genótipo.

  8. Unusual Metals in Galactic Center Stars

    Science.gov (United States)

    Hensley, Kerry

    2018-03-01

    Far from the galactic suburbs where the Sun resides, a cluster of stars in the nucleus of the Milky Way orbits a supermassive black hole. Can chemical abundance measurements help us understand the formation history of the galactic center nuclear star cluster?Studying Stellar PopulationsMetallicity distributions for stars in the inner two degrees of the Milky Way (blue) and the central parsec (orange). [Do et al. 2018]While many galaxies host nuclear star clusters, most are too distant for us to study in detail; only in the Milky Way can we resolve individual stars within one parsec of a supermassive black hole. The nucleus of our galaxy is an exotic and dangerous place, and its not yet clear how these stars came to be where they are were they siphoned off from other parts of the galaxy, or did they form in place, in an environment rocked by tidal forces?Studying the chemical abundances of stars provides a way to separate distinct stellar populations and discern when and where these stars formed. Previous studies using medium-resolution spectroscopy have revealed that many stars within the central parsec of our galaxy have very high metallicities possibly higher than any other region of the Milky Way. Can high-resolution spectroscopy tell us more about this unusual population of stars?Spectral Lines on DisplayTuan Do (University of California, Los Angeles, Galactic Center Group) and collaborators performed high-resolution spectroscopic observations of two late-type giant starslocated half a parsec from the Milky Ways supermassive black hole.Comparison of the observed spectra of the two galactic center stars (black) with synthetic spectra with low (blue) and high (orange) [Sc/Fe] values. Click to enlarge. [Do et al. 2018]In order to constrain the metallicities of these stars, Do and collaborators compared the observed spectra to a grid of synthetic spectra and used a spectral synthesis technique to determine the abundances of individual elements. They found that

  9. 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 4.0 ENERGY STAR Program Requirements for Dehumidifiers that are effective as of October...

  10. The dance of the double stars

    International Nuclear Information System (INIS)

    Theokas, A.

    1985-01-01

    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. (U.K.)

  11. Environmental effects on star formation in dwarf galaxies and star clusters

    Science.gov (United States)

    Pasetto, Stefano; Cropper, Mark; fujita, Yutaka; Chiosi, Cesare; Grebel, Eva K.

    2015-08-01

    We investigate the competitive role of the different dissipative phenomena acting on the onset of star formation history of gravitationally bound system in an external environment.Ram pressure, Kelvin-Helmholtz instability, Rayleigh-Taylor, and tidal forces are accounted separately in an analytical framework and compared in their role in influencing the star forming regions. The two-fluids instability at the interface between a stellar system and its surrounding hotter and less dense environment is related to the star formation processes through a set of differential equations. We present an analytical criterion to elucidate the dependence of star formation in a spherical stellar system on its surrounding environment useful in theoretical interpretations of numerical results as well as observational applications. We show how spherical coordinates naturally enlighten the interpretation of the two-fluids instability in a geometry that directly applies to astrophysical case. Finally, we consider the different signatures of these phenomena in synthetically realized colour-magnitude diagrams of the orbiting system thus investigating the detectability limits of these different effects for future observational projects and their relevance.The theoretical framework developed has direct applications to the cases of dwarf galaxies in galaxy clusters and dwarf galaxies orbiting our Milky Way system, as well as any primordial gas-rich cluster of stars orbiting within its host galaxy.

  12. Massive stars on the verge of exploding: the properties of oxygen sequence Wolf-Rayet stars

    NARCIS (Netherlands)

    Tramper, F.; Straal, S.M.; Sanyal, D.; Sana, H.; de Koter, A.; Gräfener, G.; Langer, N.; Vink, J.S.; de Mink, S.E.; Kaper, L.

    2015-01-01

    Context. Oxygen sequence Wolf-Rayet (WO) stars are a very rare stage in the evolution of massive stars. Their spectra show strong emission lines of helium-burning products, in particular highly ionized carbon and oxygen. The properties of WO stars can be used to provide unique constraints on the

  13. StarLogo TNG

    Science.gov (United States)

    Klopfer, Eric; Scheintaub, Hal; Huang, Wendy; Wendel, Daniel

    Computational approaches to science are radically altering the nature of scientific investigatiogn. Yet these computer programs and simulations are sparsely used in science education, and when they are used, they are typically “canned” simulations which are black boxes to students. StarLogo The Next Generation (TNG) was developed to make programming of simulations more accessible for students and teachers. StarLogo TNG builds on the StarLogo tradition of agent-based modeling for students and teachers, with the added features of a graphical programming environment and a three-dimensional (3D) world. The graphical programming environment reduces the learning curve of programming, especially syntax. The 3D graphics make for a more immersive and engaging experience for students, including making it easy to design and program their own video games. Another change to StarLogo TNG is a fundamental restructuring of the virtual machine to make it more transparent. As a result of these changes, classroom use of TNG is expanding to new areas. This chapter is concluded with a description of field tests conducted in middle and high school science classes.

  14. ENERGY STAR Certified Televisions

    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 Televisions that are effective as of October 30,...

  15. 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,...

  16. Weighing the Smallest Stars

    Science.gov (United States)

    2005-01-01

    VLT Finds Young, Very Low Mass Objects Are Twice As Heavy As Predicted Summary Thanks to the powerful new high-contrast camera installed at the Very Large Telescope, photos have been obtained of a low-mass companion very close to a star. This has allowed astronomers to measure directly the mass of a young, very low mass object for the first time. The object, more than 100 times fainter than its host star, is still 93 times as massive as Jupiter. And it appears to be almost twice as heavy as theory predicts it to be. This discovery therefore suggests that, due to errors in the models, astronomers may have overestimated the number of young "brown dwarfs" and "free floating" extrasolar planets. PR Photo 03/05: Near-infrared image of AB Doradus A and its companion (NACO SDI/VLT) A winning combination A star can be characterised by many parameters. But one is of uttermost importance: its mass. It is the mass of a star that will decide its fate. It is thus no surprise that astronomers are keen to obtain a precise measure of this parameter. This is however not an easy task, especially for the least massive ones, those at the border between stars and brown dwarf objects. Brown dwarfs, or "failed stars", are objects which are up to 75 times more massive than Jupiter, too small for major nuclear fusion processes to have ignited in its interior. To determine the mass of a star, astronomers generally look at the motion of stars in a binary system. And then apply the same method that allows determining the mass of the Earth, knowing the distance of the Moon and the time it takes for its satellite to complete one full orbit (the so-called "Kepler's Third Law"). In the same way, they have also measured the mass of the Sun by knowing the Earth-Sun distance and the time - one year - it takes our planet to make a tour around the Sun. The problem with low-mass objects is that they are very faint and will often be hidden in the glare of the brighter star they orbit, also when viewed

  17. MASSIVE INFANT STARS ROCK THEIR CRADLE

    Science.gov (United States)

    2002-01-01

    Extremely intense radiation from newly born, ultra-bright stars has blown a glowing spherical bubble in the nebula N83B, also known as NGC 1748. A new NASA Hubble Space Telescope image has helped to decipher the complex interplay of gas and radiation of a star-forming region in a nearby galaxy. The image graphically illustrates just how these massive stars sculpt their environment by generating powerful winds that alter the shape of the parent gaseous nebula. These processes are also seen in our Milky Way in regions like the Orion Nebula. The Hubble telescope is famous for its contribution to our knowledge about star formation in very distant galaxies. Although most of the stars in the Universe were born several billions of years ago, when the Universe was young, star formation still continues today. This new Hubble image shows a very compact star-forming region in a small part of one of our neighboring galaxies - the Large Magellanic Cloud. This galaxy lies only 165,000 light-years from our Milky Way and can easily be seen with the naked eye from the Southern Hemisphere. Young, massive, ultra-bright stars are seen here just as they are born and emerge from the shelter of their pre-natal molecular cloud. Catching these hefty stars at their birthplace is not as easy as it may seem. Their high mass means that the young stars evolve very rapidly and are hard to find at this critical stage. Furthermore, they spend a good fraction of their youth hidden from view, shrouded by large quantities of dust in a molecular cloud. The only chance is to observe them just as they start to emerge from their cocoon - and then only with very high-resolution telescopes. Astronomers from France, the U.S., and Germany have used Hubble to study the fascinating interplay between gas, dust, and radiation from the newly born stars in this nebula. Its peculiar and turbulent structure has been revealed for the first time. This high-resolution study has also uncovered several individual stars

  18. 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…

  19. Energy spectrum of flares of the UV Cet stars and physical measunings of several statistical characteristics of these stars

    International Nuclear Information System (INIS)

    Gershberg, R.E.

    1985-01-01

    Accounting the observed power character of the energy spectrum of flares of the UV Cet-type stars, several statistical characterisitics of there stars are considered. It is shown that a mean amplitude of flares is mainly determined with an amplitude of the faintest flare that can be registered at the star under consideration and therefore - contrary to tradition - the mean flare amplitude cannot be used as a measure of a flare activity of the star. Mean frequencuy of flares registered at a flare star dependes statisticaally certainly ona an absolute magneitude of the star - contary to wide spread belief, true mean frequencies are higher at brighter stars. On the basis of the Cataloque of flare stars in Pleiades by Haro, Chavira and Gonzalez a luminosity function of therese stars is constructed. Using this function and the revealed dependence of flare mean frequencies on stellar absolute magnitudes, a distribution of flare stars in Pleiades along flare mean frequencies is constructed. This shows that the cluster contains flare stars with mean frequencies of photographically registered flares from 10 -4 to 10 -2 hour -1 or within even narrower interval of frequencies and the total number of such stars in the cluster exceeds 1100

  20. Mass loss from Wolf-Rayet stars

    International Nuclear Information System (INIS)

    Willis, A.J.

    1982-01-01

    Recent results relating to the stellar winds and mass loss rates of the WR stars are reviewed, emphasising new data and their interpretation acquired at UV, IR and Radio wavelengths. The subject is discussed under the headings: physical and chemical properties of WR stars (effective temperatures and radiative luminosities; masses; chemical abundances); velocity, ionisation and excitation structure of WR winds; mass loss rates of WR stars; mass loss properties of WR stars in the LMC; comparisons with theoretical models of mass loss; ring nebulae around WR stars; conclusions. (author)

  1. The Dark Side of Neutron Stars

    DEFF Research Database (Denmark)

    Kouvaris, Christoforos

    2013-01-01

    We review severe constraints on asymmetric bosonic dark matter based on observations of old neutron stars. Under certain conditions, dark matter particles in the form of asymmetric bosonic WIMPs can be eectively trapped onto nearby neutron stars, where they can rapidly thermalize and concentrate...... in the core of the star. If some conditions are met, the WIMP population can collapse gravitationally and form a black hole that can eventually destroy the star. Based on the existence of old nearby neutron stars, we can exclude certain classes of dark matter candidates....

  2. 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....

  3. Observations of central stars

    International Nuclear Information System (INIS)

    Lutz, J.H.

    1978-01-01

    Difficulties occurring in the observation of central stars of planetary nebulae are reviewed with emphasis on spectral classifications and population types, and temperature determination. Binary and peculiar central stars are discussed. (U.M.G.)

  4. DO HYDROGEN-DEFICIENT CARBON STARS HAVE WINDS?

    International Nuclear Information System (INIS)

    Geballe, T. R.; Rao, N. Kameswara; Clayton, Geoffrey C.

    2009-01-01

    We present high resolution spectra of the five known hydrogen-deficient carbon (HdC) stars in the vicinity of the 10830 A line of neutral helium. In R Coronae Borealis (RCB) stars the He I line is known to be strong and broad, often with a P Cygni profile, and must be formed in the powerful winds of those stars. RCB stars have similar chemical abundances as HdC stars and also share greatly enhanced 18 O abundances with them, indicating a common origin for these two classes of stars, which has been suggested to be white dwarf mergers. A narrow He I absorption line may be present in the hotter HdC stars, but no line is seen in the cooler stars, and no evidence for a wind is found in any of them. The presence of wind lines in the RCB stars is strongly correlated with dust formation episodes so the absence of wind lines in the HdC stars, which do not make dust, is as expected.

  5. Monitoring pulsating giant stars in M33: star formation history and chemical enrichment

    Science.gov (United States)

    Javadi, A.; van Loon, J. Th

    2017-06-01

    We have conducted a near-infrared monitoring campaign at the UK InfraRed Telescope (UKIRT), of the Local Group spiral galaxy M33 (Triangulum). A new method has been developed by us to use pulsating giant stars to reconstruct the star formation history of galaxies over cosmological time as well as using them to map the dust production across their host galaxies. In first Instance the central square kiloparsec of M33 was monitored and long period variable stars (LPVs) were identified. We give evidence of two epochs of a star formation rate enhanced by a factor of a few. These stars are also important dust factories, we measure their dust production rates from a combination of our data with Spitzer Space Telescope mid-IR photometry. Then the monitoring survey was expanded to cover a much larger part of M33 including spiral arms. Here we present our methodology and describe results for the central square kiloparsec of M33 [1-4] and disc of M33 [5-8].

  6. Monitoring pulsating giant stars in M33: star formation history and chemical enrichment

    International Nuclear Information System (INIS)

    Javadi, A; Van Loon, J Th

    2017-01-01

    We have conducted a near-infrared monitoring campaign at the UK InfraRed Telescope (UKIRT), of the Local Group spiral galaxy M33 (Triangulum). A new method has been developed by us to use pulsating giant stars to reconstruct the star formation history of galaxies over cosmological time as well as using them to map the dust production across their host galaxies. In first Instance the central square kiloparsec of M33 was monitored and long period variable stars (LPVs) were identified. We give evidence of two epochs of a star formation rate enhanced by a factor of a few. These stars are also important dust factories, we measure their dust production rates from a combination of our data with Spitzer Space Telescope mid-IR photometry. Then the monitoring survey was expanded to cover a much larger part of M33 including spiral arms. Here we present our methodology and describe results for the central square kiloparsec of M33 [1–4] and disc of M33 [5–8]. (paper)

  7. THE Be STAR SPECTRA (BeSS) DATABASE

    International Nuclear Information System (INIS)

    Neiner, C.; De Batz, B.; Cochard, F.; Floquet, M.; Mekkas, A.; Desnoux, V.

    2011-01-01

    Be stars vary on many timescales, from hours to decades. A long time base of observations to analyze certain phenomena in these stars is therefore necessary. Collecting all existing and future Be star spectra into one database has thus emerged as an important tool for the Be star community. Moreover, for statistical studies, it is useful to have centralized information on all known Be stars via an up-to-date catalog. These two goals are what the Be Star Spectra (BeSS, http://basebe.obspm.fr) database proposes to achieve. The database contains an as-complete-as-possible catalog of known Be stars with stellar parameters, as well as spectra of Be stars from all origins (any wavelength, any epoch, any resolution, etc.). It currently contains over 54,000 spectra of more than 600 different Be stars among the ∼2000 Be stars in the catalog. A user can access and query this database to retrieve information on Be stars or spectra. Registered members can also upload spectra to enrich the database. Spectra obtained by professional as well as amateur astronomers are individually validated in terms of format and science before being included in BeSS. In this paper, we present the database itself as well as examples of the use of BeSS data in terms of statistics and the study of individual stars.

  8. A Heavy Flavor Tracker for STAR

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Z.; Chen, Y.; Kleinfelder, S.; Koohi, A.; Li, S.; Huang, H.; Tai, A.; Kushpil, V.; Sumbera, M.; Colledani, C.; Dulinski, W.; Himmi,A.; Hu, C.; Shabetai, A.; Szelezniak, M.; Valin, I.; Winter, M.; Miller,M.; Surrow, B.; Van Nieuwenhuizen G.; Bieser, F.; Gareus, R.; Greiner,L.; Lesser, F.; Matis, H.S.; Oldenburg, M.; Ritter, H.G.; Pierpoint, L.; Retiere, F.; Rose, A.; Schweda, K.; Sichtermann, E.; Thomas, J.H.; Wieman, H.; Yamamoto, E.; Kotov, I.

    2005-03-14

    We propose to construct a Heavy Flavor Tracker (HFT) for theSTAR experiment at RHIC. The HFT will bring new physics capabilities toSTAR and it will significantly enhance the physics capabilities of theSTAR detector at central rapidities. The HFT will ensure that STAR willbe able to take heavy flavor data at all luminosities attainablethroughout the proposed RHIC II era.

  9. A Heavy Flavor Tracker for STAR

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Z.; Chen, Y.; Kleinfelder, S.; Koohi, A.; Li, S.; Huang, H.; Tai, A.; Kushpil, V.; Sumbera, M.; Colledani, C.; Dulinski, W.; Himmi,A.; Hu, C.; Shabetai, A.; Szelezniak, M.; Valin, I.; Winter, M.; Surrow,B.; Van Nieuwenhuizen, G.; Bieser, F.; Gareus, R.; Greiner, L.; Lesser,F.; Matis, H.S.; Oldenburg, M.; Ritter, H.G.; Pierpoint, L.; Retiere, F.; Rose, A.; Schweda, K.; Sichtermann, E.; Thomas, J.H.; Wieman, H.; Yamamoto, E.; Kotov, I.

    2005-03-14

    We propose to construct a Heavy Flavor Tracker (HFT) for the STAR experiment at RHIC. The HFT will bring new physics capabilities to STAR and it will significantly enhance the physics capabilities of the STAR detector at central rapidities. The HFT will ensure that STAR will be able to take heavy flavor data at all luminosities attainable throughout the proposed RHIC II era.

  10. A Heavy Flavor Tracker for STAR

    International Nuclear Information System (INIS)

    Xu, Z.; Chen, Y.; Kleinfelder, S.; Koohi, A.; Li, S.; Huang, H.; Tai, A.; Kushpil, V.; Sumbera, M.; Colledani, C.; Dulinski, W.; Himmi, A.; Hu, C.; Shabetai, A.; Szelezniak, M.; Valin, I.; Winter, M.; Surrow, B.; Van Nieuwenhuizen, G.; Bieser, F.; Gareus, R.; Greiner, L.; Lesser, F.; Matis, H.S.; Oldenburg, M.; Ritter, H.G.; Pierpoint, L.; Retiere, F.; Rose, A.; Schweda, K.; Sichtermann, E.; Thomas, J.H.; Wieman, H.; Yamamoto, E.; Kotov, I.

    2005-01-01

    We propose to construct a Heavy Flavor Tracker (HFT) for the STAR experiment at RHIC. The HFT will bring new physics capabilities to STAR and it will significantly enhance the physics capabilities of the STAR detector at central rapidities. The HFT will ensure that STAR will be able to take heavy flavor data at all luminosities attainable throughout the proposed RHIC II era

  11. Studies for the radiation levels and shielding in RR73, RR77 and UJ76 in IR7 for collimation phase 1 - 035

    CERN Document Server

    Tsoulou, A; Ferrari, A; CERN. Geneva. AB Department

    2005-01-01

    The Collimation project is one of the most crucial for the LHC performance. 54 movable, two-sided collimators will be placed in two insertions, i.e. IR3 and IR7, which will be among the most radioactive in the LHC. For a normal machine operation, it is essential that the electronics do not degrade or fail â€" at least very often â€" due to irradiation. The radiation levels initially estimated in IR7 (RR73/77 and UJ76) were too high for the electronics to tolerate. A shielding study was necessary to be done, in parallel with the study for the absorber positions. This article summarizes the shielding proposed and the radiation levels calculated for the final collimator and absorber positions as indicated by the FLUKA team.

  12. Studies for the radiation levels and shielding in RR73, RR77 and UJ76 in IR7 for collimation phase 1 - 372

    CERN Document Server

    Tsoulou, A; Ferrari, A

    2005-01-01

    The Collimation project is one of the most crucial for the LHC performance. 54 movable, two-sided collimators will be placed in two insertions, i.e. IR3 and IR7, which will be among the most radioactive in the LHC. For a normal machine operation, it is essential that the electronics do not degrade or fail â€" at least very often â€" due to irradiation. The radiation levels initially estimated in IR7 (RR73/77 and UJ76) were too high for the electronics to tolerate. A shielding study was necessary to be done, in parallel with the study for the absorber positions. This article summarizes the shielding proposed and the radiation levels calculated for the final collimator and absorber positions as indicated by the FLUKA team.

  13. CHAPTER 1. Miktoarm Star (µ-Star) Polymers: A Successful Story

    KAUST Repository

    Iatrou, Hermis; Avgeropoulos, Apostolos; Sakellariou, Georgios; Pitsikalis, Marinos; Hadjichristidis, Nikolaos

    2017-01-01

    The term miktoarm stars (coming from the Greek word μιτσ meaning mixed) was adopted in 1992 by our group for star polymers with either chemical (e.g., AB), molecular weight (e.g., AA′), topological (e.g., (AB)-junction-(BA)), or functional group (e.g., AA) asymmetry. The first μ-stars synthesized by anionic polymerization, on the one hand, guided polymer chemists working with other types of polymerization techniques towards this direction and, on the other hand, helped polymer physicists to carry out experiments and develop theories on the influence of the architecture on the morphology of block copolymers. Synthetic strategies based on anionic polymerization, as well as a few examples showing the influence of the miktoarm structure on the morphology of block copolymers, are reviewed in this chapter.

  14. CHAPTER 1. Miktoarm Star (µ-Star) Polymers: A Successful Story

    KAUST Repository

    Iatrou, Hermis

    2017-04-13

    The term miktoarm stars (coming from the Greek word μιτσ meaning mixed) was adopted in 1992 by our group for star polymers with either chemical (e.g., AB), molecular weight (e.g., AA′), topological (e.g., (AB)-junction-(BA)), or functional group (e.g., AA) asymmetry. The first μ-stars synthesized by anionic polymerization, on the one hand, guided polymer chemists working with other types of polymerization techniques towards this direction and, on the other hand, helped polymer physicists to carry out experiments and develop theories on the influence of the architecture on the morphology of block copolymers. Synthetic strategies based on anionic polymerization, as well as a few examples showing the influence of the miktoarm structure on the morphology of block copolymers, are reviewed in this chapter.

  15. Flare stars in Pleiades. 6

    International Nuclear Information System (INIS)

    Mirzoyan, L.V.; Chavushyan, O.S.; Oganyan, G.B.; Ambaryan, V.V.; Garibdzhanyan, A.T.; Melikyan, N.D.; Natsvlishvili, R.Sh.; AN Gruzinskoj SSR, Abastumani. Abastumanskaya Astrofizicheskaya Observatoriya)

    1981-01-01

    The results of photographic observations of stellar flares in the Pleiades region carried out at the Byurakan and Abastumani astrophysical observatories during 1976-1979 are given. On the basis of these observations 17 new flare stars have been found. Total number of all known flare stars in the Pleiades region on 1 June 1980 reached 524, and the number of all flares-1244. The observational data on distribution of flare stars according to the observed flares is satisfactorily represented by the average frequency function introduced by V.A.Ambartsumian. The total number of the flare stars in the Pleiades is of the order of 1100. Using three telescopes, synchronous photographic observations of stellar flares in Pleiades in U, B, V, system are carried out. The colour indices U-B and B-V of stellar flares in periods including the maximum of the flare slightly differ from that of photoelectrically defined for flares of UV Ceti type stars, which testifies the physical relationship of flare stars in Pleiades and in the vicinity of the Sun [ru

  16. 77 FR 1009 - Airworthiness Directives; Rolls-Royce plc (RR) RB211-524 Series Turbofan Engines

    Science.gov (United States)

    2012-01-09

    ... Airworthiness Directives; Rolls-Royce plc (RR) RB211-524 Series Turbofan Engines AGENCY: Federal Aviation... 5, 2005). ADDRESSES: For service information identified in this AD, contact Rolls-Royce plc, P.O...,000. Based on these figures, we estimate the total cost of the AD to U.S. operators to be $4,206,960...

  17. Research performed at the ET-RR-1 reactor using the neutron scattering equipment

    International Nuclear Information System (INIS)

    Adib, M.; Maayouf, R.M.A.; Abdel-Kawy, A.

    1990-02-01

    This report represents the results of studies and measurements, performed at the ET-RR-1 reactor, using the neutron scattering equipment supplied by the IAEA according to the technical assistance project EGY/1/11/10. The results of these studies, starting in 1980 and continuing to date, are discussed; the use of the equipment, both as a neutron monochromator and fixed scattering angle spectrometer, is also assessed. (author). 19 refs, 17 figs

  18. Super-solar Metallicity Stars in the Galactic Center Nuclear Star Cluster: Unusual Sc, V, and Y Abundances

    Science.gov (United States)

    Do, Tuan; Kerzendorf, Wolfgang; Konopacky, Quinn; Marcinik, Joseph M.; Ghez, Andrea; Lu, Jessica R.; Morris, Mark R.

    2018-03-01

    We present adaptive-optics assisted near-infrared high-spectral-resolution observations of late-type giants in the nuclear star cluster of the Milky Way. The metallicity and elemental abundance measurements of these stars offer us an opportunity to understand the formation and evolution of the nuclear star cluster. In addition, their proximity to the supermassive black hole (∼0.5 pc) offers a unique probe of the star formation and chemical enrichment in this extreme environment. We observed two stars identified by medium spectral-resolution observations as potentially having very high metallicities. We use spectral-template fitting with the PHOENIX grid and Bayesian inference to simultaneously constrain the overall metallicity, [M/H], alpha-element abundance [α/Fe], effective temperature, and surface gravity of these stars. We find that one of the stars has very high metallicity ([M/H] > 0.6) and the other is slightly above solar metallicity. Both Galactic center stars have lines from scandium (Sc), vanadium (V), and yttrium (Y) that are much stronger than allowed by the PHOENIX grid. We find, using the spectral synthesis code Spectroscopy Made Easy, that [Sc/Fe] may be an order of magnitude above solar. For comparison, we also observed an empirical calibrator in NGC 6791, the highest metallicity cluster known ([M/H] ∼ 0.4). Most lines are well matched between the calibrator and the Galactic center stars, except for Sc, V, and Y, which confirms that their abundances must be anomalously high in these stars. These unusual abundances, which may be a unique signature of nuclear star clusters, offer an opportunity to test models of chemical enrichment in this region.

  19. The formation of galaxies from pregalactic stars

    International Nuclear Information System (INIS)

    Jones, Janet

    1982-01-01

    A knowledge of how and when the first stars formed is vital for our understanding of the formation and early evolution of galaxies. Evidence is given that the first stars were pregalactic: indeed, that at least two generations of stars had formed before galaxies collapsed. A model is presented describing the effects of pregalactic stars on galaxy evolution. The first generation -primordial stars- were massive and few in number. A brief description is given for the formation of such a star. The second generation included stars of all masses and involved widespread star formation. Gas ejected from these stars on timescales of 6 x 10 7 to 6 x 10 8 years induced a qualitative change into the dynamics of collapsing perturbations, leading to a characteristic mass of galaxies of 10 10 - 10 12 M 0 . Variations in the rate of gas ejection were responsible for different morphological structures - elliptical and spirals. A few comments are made on some other implications of the model

  20. Quark Deconfinement in Rotating Neutron Stars

    Directory of Open Access Journals (Sweden)

    Richard D. Mellinger

    2017-01-01

    Full Text Available In this paper, we use a three flavor non-local Nambu–Jona-Lasinio (NJL model, an improved effective model of Quantum Chromodynamics (QCD at low energies, to investigate the existence of deconfined quarks in the cores of neutron stars. Particular emphasis is put on the possible existence of quark matter in the cores of rotating neutron stars (pulsars. In contrast to non-rotating neutron stars, whose particle compositions do not change with time (are frozen in, the type and structure of the matter in the cores of rotating neutron stars depends on the spin frequencies of these stars, which opens up a possible new window on the nature of matter deep in the cores of neutron stars. Our study shows that, depending on mass and rotational frequency, up to around 8% of the mass of a massive neutron star may be in the mixed quark-hadron phase, if the phase transition is treated as a Gibbs transition. We also find that the gravitational mass at which quark deconfinement occurs in rotating neutron stars varies quadratically with spin frequency, which can be fitted by a simple formula.