Browsing by Author "Karl, C."

Now showing items 1-20 of 22

    • 2MASS J0516288+260738: Discovery of the first eclipsing late K + Brown dwarf binary system 

      Schuh, S.L.; Handler, G.; Drechsel, H.; Hauschildt, P.; Dreizler, S.; Medupe, R.; Karl, C.; Napiwotzki, R.; Kim, S.; Park, B.G.; Wood, M.; Paparo, M.; Szeidl, B.; Viraghalmy, G.; Zsuffa, D.; Hashimoto, O.; Kinugasa, K.; Taguchi, H.; Kambe, E.; Leibowitz, E.; Ibbetson, P.; Lipkin, Y.; Nagel, T.; Gohler, E.; Pretorius, M.L. (2003-11)
      We report the discovery of a new eclipsing system less than one arcminute south of the pulsating DB white dwarf KUV05134+2605. The object could be identified with the point source 2MASSJ0516288+260738 published by the Two ...

    • Binaries discovered by the SPY project IV. Five single-lined DA double white dwarfs 

      Nelemans, G.; Napiwotzki, R.; Karl, C.; Marsh, T.R.; Voss, B.; Roelofs, G.; Izzard, R.G.; Montgomery, M.; Reerink, T.; Christlieb, N.; Reimers, D. (2005)
      We present results from our ongoing follow-up observations of double white dwarf binaries detected in the ESO SN Ia Progenitor SurveY (SPY). We discuss our observing strategy and data analysis and present the orbital ...

    • Binaries discovered by the SPY project. I. HE 1047-0436: A subdwarf B white dwarf syste 

      Napiwotzki, R.; Edelmann, H.; Heber, U.; Karl, C.; Drechsel, H.; Pauli, E.M.; Christlieb, N. (2001-10)
      In the course of our search for double degenerate binaries as potential progenitors of type Ia supernovae with the UVES spectrograph at the ESO VLT (ESO SNIa Progenitor surveY { SPY) we discovered that the sdB star HE1047−0436 ...

    • Binaries discovered by the SPY project. III. HE 2209-1444: A massive, short period double degenerate 

      Karl, C.; Napiwotzki, R.; Nelemans, G.; Christlieb, N.; Koester, D.; Heber, U.; Reimers, D. (2003-11)
      In the course of our search for double degenerate (DD) binaries as potential progenitors of type Ia supernovae with the UVES spectrograph at the ESO VLT (ESO SN Ia Progenitor surveY – SPY) we discovered HE2209−1444 to be ...

    • Binary sdB Stars with Massive Compact Companions 

      Geier, S.; Karl, C.; Edelmann, H.; Heber, U.; Napiwotzki, R. (Astronomical Society of the Pacific, 2008)
      The masses of compact objects like white dwarfs, neutron stars and black holes are fundamental to astrophysics, but very difficult to measure. We present the results of an analysis of subluminous B (sdB) stars in close ...

    • Binary White Dwarfs in the Supernova Ia Progenitor Survey 

      Napiwotzki, R.; Karl, C.; Nelemans, G.; Yungelson, L.; Christlieb, N.; Drechsel, H.; Heber, U.; Homeier, D.; Koester, D.; Leibundgut, B.; Marsh, T.R.; Moehler, S.; Renzini, A.; Reimers, D. (Astronomical Society of the Pacific, 2007)
      We report results of a systematic radial velocity survey for double degenerate (DD) binaries as potential progenitors of type Ia supernovae: SPY (ESO Supernovae Ia Progenitor surveY). More than 1000 white dwarfs (WDs) and ...

    • Close binary EHB stars from SPY 

      Napiwotzki, R.; Karl, C.; Lisker, T.; Heber, U.; Christlieb, N.; Reimers, D.; Nelemans, G.; Homeier, D. (2004-06)

    • Double Degenerate and Progenitors of Supernovae Type Ia 

      Napiwotzki, R.; Yungelson, L.; Nelemans, G.; Marsh, T.R.; Leibundgut, B.; Renzini, A.; Homeier, D.; Koester, D.; Moehler, S.; Christlieb, N.; Reimers, D.; Drechsel, H.; Heber, U.; Karl, C.; Pauli, E.M. (Astronomical Society of the Pacific, 2004)
      We report on systematic radial velocity surveys for white dwarf { white dwarf binaries (double degenerates { DDs) including SPY (ESO Supernovae Ia progenitor survey) recently carried out at the VLT. A large sample of DD ...

    • High-resolution UVES/VLT spectra of white dwarfs observed for the ESO SN Ia progenitor survey (SPY). I 

      Koester, D.; Napiwotzki, R.; Christlieb, N.; Drechsel, H.; Hagen, H.J.; Heber, U.; Homeier, D.; Karl, C.; Leibundgut, B.; Moehler, S.; Nelemans, G.; Reimers, D.; Pauli, E.M.; Renzini, A.; Yungelson, L. (2001-11)

    • HS 2333 + 3927: a new sdB binary with a large reflection effect 

      Karl, C.; Heber, U.; Drechsel, H.; Napiwotzki, R.; Altmann, M.; Ostensen, R.; Folkes, S.; Solheim, J.E.; Cordes, O.; Voss, B.; Koester, D. (2004)
      We report the discovery of a binary, HS 2233 + 3927, consisting of an sdB star with a faint companion. From its lightcurve the orbital period of 14,844 s, the mass ratio, the inclination, and other system parameters are ...

    • HS 2333 3927: A new sdB dM binary with a large reflection effect 

      Heber, U.; Drechsel, H.; Ostensen, R.; Karl, C.; Napiwotzki, R.; Altmann, M.; Cordes, O.; Solheim, J.E.; Voss, B.; Koester, D.; Folkes, S. (2004-06)

    • Identification of a DO white dwarf and a PG 1159 star in the ESO SN Ia progenitor survey (SPY) 

      Werner, K.; Rauch, T.; Napiwotzki, R.; Christlieb, N.; Reimers, D.; Karl, C. (2004-09)

    • Identification of a DO White Dwarf and a PG1159 Star in the ESO SN Ia Progenitor Survey (SPY) 

      Werner, K.; Rauch, T.; Napiwotzki, R.; Christlieb, N.; Reimers, D.; Karl, C. (Astronomical Society of the Pacific, 2005)
      We present high-resolution VLT spectra of a new DO white dwarf and a new PG1159 star, which we identified in the ESO SPY survey. The PG1159 star is a low-gravity, extremely hot (Te® = 160 000 K, log g = 6) star, having a ...

    • The Mass of the sdB Primary of the Binary HS 2333+3927 

      Heber, U.; Drechsel, H.; Karl, C.; Ostensen, R.; Folkes, S.; Napiwotzki, R.; Altmann, M.; Cordes, O.; Solheim, J.E.; Voss, B.; Koester, D. (Astronomical Society of the Pacific, 2005)
      Short period sdB binaries with cool companions are crucial to understand pre-CV evolution, because they will evolve into cataclysmic variables, when the sdB will have left the extended horizontal branch. Recently we ...

    • New Results from the Supernova Ia Progenitor Survey 

      Napiwotzki, R.; Karl, C.; Nelemans, G.; Yungelson, L.; Christlieb, N.; Drechsel, H.; Heber, U.; Homeier, D.; Koester, D.; Kruk, J.; Leibundgut, B.; Marsh, T.R.; Moehler, S.; Renzini, A.; Reimers, D. (Astronomical Society of the Pacific, 2005)
      We report on a systematic radial velocity survey for double degenerate (DD) binaries as potential progenitors of type Ia supernovae: SPY (ESO Supernovae Ia Progenitor surveY). More than 1000 white dwarfs and pre-white ...

    • Rotation Velocities of DA White Dwarfs with Convective Atmospheres 

      Karl, C.; Heber, U.; Napiwotzki, R.; Dreizler, S.; Koester, D.; Reid, I.N. (Astronomical Society of the Pacific, 2005)
      The sharp H® NLTE line cores of hydrogen rich (DA) white dwarfs allow their projected rotational velocities to be determined. High resolution optical spectra of 22 stars obtained with the Keck I telescope are matched by ...

    • Rotation velocities of white dwarfs. III. DA stars with convective atmospheres 

      Karl, C.; Napiwotzki, R.; Heber, U.; Dreizler, S.; Koester, D.; Reid, I.N. (2005-05)

    • Search for progenitors of supernovae type Ia with SPY 

      Napiwotzki, R.; Christlieb, N.; Drechsel, H.; Hagen, H.J.; Heber, U.; Homeier, D.; Karl, C.; Koester, D.; Leibundgut, B.; Marsh, T.R.; Moehler, S.; Nelemans, G.; Pauli, E.M.; Reimers, D.; Renzini, A.; Yungelson, L. (2001)

    • Six detached white-dwarf close binaries 

      Morales-Rueda, L.; Maxted, P.F.L.; Nelemans, G.; Karl, C.; Napiwotzki, R.; Moran, C.; Marsh, T.R. (2005-05)

    • Spectroscopic Analysis of Subluminous B Stars in Binaries with Compact Companions 

      Geier, S.; Karl, C.; Edelmann, H.; Heber, U.; Napiwotzki, R. (Astronomical Society of the Pacific, 2007)
      The masses of compact objects like white dwarfs, neutron stars and black holes are fundamental to astrophysics, but very difficult to measure. We present the results of an analysis of subluminous B (sdB) stars in close ...