Now showing items 1-16 of 16

    • The 72-h WEBT microvariability observation of blazar S5 0716+714 in 2009 

      Bhatta, G.; Webb, James R.; Hollingsworth, H.; Dhalla, S.; Khanuja, A.; Bachev, Rumen S.; Blinov, Dmitry A.; Böttcher, Markus; Bravo Calle, O. J A; Vennes, Stéphane (2013-10-10)
      Context. The international Whole Earth Blazar Telescope (WEBT) consortium planned and carried out three days of intensive micro-variability observations of S5 0716+714 from February 22, 2009 to February 25, 2009. This ...
    • Abundance of elements beyond the iron group in cool do white dwarfs 

      Chayer, Pierre; Vennes, Stéphane; Dupuis, Jean François; Kruk, Jeffrey W. (2005-09-10)
      We report the presence of elements beyond the iron group in the atmospheres of the cool DO white dwarfs HD 149499 B and HZ 21. Photospheric lines of germanium (Z = 32), arsenic (33), selenium (34), tin (50), tellurium (52), ...
    • CPD -20 1123 (ALBUS 1) is a bright he-b subdwarf 

      Vennes, Stéphane; Kawka, Adéla; Smith, Jonathan Allyn (2007-10-10)
      Based on photometric and astrometric data it has been proposed that Albus 1 (also known as CPD -20 1123) might be a hot white dwarf similar to G191-B2B or, alternatively, a hot subdwarf. We obtained a series of optical ...
    • Empirical determination of convection parameters in white dwarfs. I. Whole Earth Telescope observations of EC14012-1446 

      Provençal, Judith L.; Montgomery, Michael H.; Kanaan, Antonio; Thompson, Susan E.; Dalessio, James; Shipman, Harry L.; Childers, D.; Wood, Matt A.; Vennes, Stéphane; Németh, Péter (2012-06-01)
      We report on an analysis of 308.3 hr of high-speed photometry targeting the pulsating DA white dwarf EC14012-1446. The data were acquired with the Whole Earth Telescope during the 2008 international observing run XCOV26. ...
    • FUSE observations of intermediate temperature DA: Atmospheric parameters and metal abundances 

      Dupuis, Jean François; Hénault-Brunet, Vincent; Chayer, Pierre; Vennes, Stéphane; Kruk, Jeffrey W. (2009)
      We present results from our analysis of a sample of DA white dwarfs having effective temperature below 25,000 K observed with the FUSE satellite with the goals of better understanding the origin of metals detected in the ...
    • Iron in hot DA white dwarfs 

      Vennes, Stéphane; Chayer, Pierre; Dupuis, Jean François; Lanz, Thierry M. (2006-12-01)
      We present a study of the iron abundance pattern in hot, hydrogen-rich (DA) white dwarfs. The study is based on new and archival far-ultraviolet spectroscopy of a sample of white dwarfs in the temperature range 30,000 K ≲ ...
    • LP 133-373: A new chromospherically active eclipsing dMe binary with a distant, cool white dwarf companion 

      Vaccaro, Todd R.; Rudkin, Mark J.; Kawka, Adéla; Vennes, Stéphane; Oswalt, T. D.; Silver, Isaac M.; Wood, Matt A.; Smith, Jonathan Allyn (2007-06-01)
      We report the discovery of the partially eclipsing binary LP 133-373. Nearly identical eclipses along with observed photometric colors and spectroscopy indicate that it is a pair of chromospherically active dM4 stars in a ...
    • LP 400-22, a Very Low Mass and High-Velocity White Dwarf 

      Kawka, Adéla; Vennes, Stéphane; Oswalt, Terry D.; Smith, J. Allyn; Silvestri, Nicole M. (2006-03-08)
      We report the identification of LP 400-22 (WD 2234+222) as a very low mass and high-velocity white dwarf. The ultraviolet GALEX and optical photometric colors and a spectral line analysis of LP 400-22 show this star to ...
    • Orbital parameters and chemical composition of four white dwarfs in post-common-envelope binaries 

      Kawka, Adéla; Vennes, Stéphane; Dupuis, Jean François; Chayer, Pierre; Lanz, Thierry M. (2008-03-10)
      We present FUSE observations of the hot white dwarfs in the post-common-envelope binaries Feige 24, EUVE J0720-317, BPM 6502, and EUVE J2013+400. The spectra show numerous photospheric absorption lines, which trace the ...
    • Preliminary XCOV26 results for EC14012-1446 

      Provençal, Judith L.; Thompson, Susan E.; Montgomery, Michael H.; Kanaan, Antonio; Shipman, Harry L.; Dalessio, James; Childers, D.; Clémens, Christian; Vennes, Stéphane; Wood, Matt A. (2009)
      EC14012-1446 is a hydrogen atmosphere (DA) white dwarf pulsator. Its rich pulsation spectrum displays a range of excited modes with complex multiplet structure, in addition to numerous combination frequencies. In April ...
    • Pressure shifts and abundance gradients in the atmosphere of the DAZ white dwarf GALEX J193156.8+011745 

      Vennes, Stéphane; Kawka, Adéla; Németh, Péter (2011-06-01)
      We present a detailed model atmosphere analysis of high-dispersion and high signal-to-noise ratio spectra of the heavily polluted DAZ white dwarf GALEX J1931+0117. The spectra obtained with the Very Large Telescope ...
    • A selection of hot subluminous stars in the GALEX survey - I. Correlation with the Guide star catalog 

      Vennes, Stéphane; Kawka, Adéla; Németh, Péter (2011-01-21)
      We assembled a catalogue of bright, hot subdwarf and white dwarf stars extracted from a joint ultraviolet, optical and infrared source list. The selection is secured using colour criteria that correlate well with effective ...
    • Spectropolarimetric survey of hydrogen-rich white dwarf stars 

      Kawka, Adéla; Vennes, Stéphane; Schmidt, Gary D.; Wickramasinghe, Dayal T.; Koch, Rolf (2007-01-01)
      We have conducted a survey of 61 southern white dwarfs searching for magnetic fields using Zeeman spectropolarimetry. Our objective is to obtain a magnetic field distribution for these objects and, in particular, to find ...
    • Spectroscopic identification of cool white dwarfs in the solar neighborhood 

      Kawka, Adéla; Vennes, Stéphane (2006-05-20)
      The New Luyten Two-Tenths catalog contains a large number of high proper motion white dwarf candidates that remain to be spectroscopically confirmed. We present new spectroscopic observations, as well as SDSS archival ...
    • Two new hot subdwarf binaries in the GALEX survey 

      Kawka, Adéla; Vennes, Stéphane; Németh, Péter; Kraus, Michaela; Kubát, Jiří (2010)
      We report the discovery of two new hot, hydrogen-rich subdwarfs (sdB) in close binary systems. The hot subdwarfs, GALEX J0321+4727 and GALEX J2349+3844, were selected from a joint optical-ultraviolet catalogue of hot ...
    • The WEBT campaign on the blazar 3C 279 in 2006 

      Böttcher, Markus; Basu, Shantanu; Joshi, Manasvita; Villata, Massimo; Arai, Akira; Aryan, N.; Asfandiyarov, I. M.; Bach, Uwe; Robertson, Jeff W.; Vennes, Stéphane (2007-12-01)
      The quasar 3C 279 was the target of an extensive multiwavelength monitoring campaign from 2006 January through April. An optical-IR-radio monitoring campaign by the Whole Earth Blazar Telescope (WEBT) collaboration was ...