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Browsing by Author "Napiwotzki, R."
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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 ... -
3D kinematics of white dwarfs from the SPY project
Pauli, E.M.; Napiwotzki, R.; Altmann, M.; Heber, U.; Odenkirchen, M.; Kerber, F. (2003-03)We present kinematics of a sample of 107 DA white dwarfs from the SPY project (ESO SN Ia Progenitor surveY) and discuss kinematic criteria for a distinction of thin disk, thick disk, and halo populations. This is the first ... -
3D kinematics of white dwarfs from the SPY project. II
Pauli, E.M.; Napiwotzki, R.; Heber, U.; Altmann, M.; Odenkirchen, M. (2006) -
3D-Kinematics of White Dwarfs from the SPY-Project
Richter, R.; Heber, U.; Napiwotzki, R. (Astronomical Society of the Pacific, 2007)We present a progress report on the kinematical analysis of the entire SPY (ESO SN Ia Progenitor surveY; see Napiwotzki et al. 2001) sample of about one thousand white dwarfs and hot subdwarfs. In a previous study (Pauli ... -
Abundances of UV bright stars in globular clusters. I. ROA 5701 in omega Centauri and Barnard 29 in M 13
Moehler, S.; Heber, U.; Lemke, M.; Napiwotzki, R. (1998)Two UV brights stars in globular clusters, ROA 5701 (ω Cen) and Barnard 29 (M 13) are analysed from high-resolution UV and optical spectra. The main aim is the measurement of iron abundances from UV spectra obtained with ... -
The AGB population in IC 1613 using JHK photometry
Sibbons, L. F.; Ryan, Sean G.; Irwin, M.; Napiwotzki, R. (2015-01-01)Context. A member of the Local Group, IC 1613 is a gas rich irregular dwarf galaxy that appears to have formed stars continuously over the last 10 Gyr and is relatively independent of external influences from other galaxies. ... -
The AGB population of NGC 6822 : Distribution and the C/M ratio from JHK photometry.
Sibbons, L. F.; Ryan, Sean G.; Cioni, M-R.L.; Irwin, M.; Napiwotzki, R. (2012-04)Context. NGC 6822 is an irregular dwarf galaxy and part of the Local Group. Its close proximity and apparent isolation provide a unique opportunity to study galactic evolution without any obvious strong external influences. ... -
The age of white dwarf companions
Weston, S.; Napiwotzki, R. (2009)We carried out a spectroscopic investigation of single lined white dwarfs (WDs) in double degenerate (DD) systems and discuss their binary evolution. Simulated spectra of the Hα region are used to derive upper limits on ... -
Anyone out there? Galactic halo post-AGB stars
Weston, S.; Napiwotzki, R.; Catalan, S. (American Institute of Physics (AIP), 2010)We present results of a survey of post-asymptotic giant branch stars (post-AGBs) at high galactic latitude. To date, few post-AGB stars are known throughout the Galaxy and the number of known members of the older populations ... -
Astronometry with the Hubble Space Telescope : trigonometric parallaxes of planetary nebula nuclei NGC 6853, NGC 7293, Abell 31 and DeHt 5
Benedict, G.F.; McArthur, B.E.; Napiwotzki, R.; Harrison, T.E.; Harris, H.C.; Nelan, E.; Bond, H.E.; Patterson, R.J.; Ciardullo, R. (2009)We present absolute parallaxes and relative proper motions for the central stars of the planetary nebulae NGC 6853 (The Dumbbell), NGC 7293 (The Helix), Abell 31, and DeHt 5. This paper details our reduction and analysis ... -
The B-type giant HD 271791 in the Galactic halo : Linking run-away stars to hyper-velocity stars
Heber, U.; Edelmann, H.; Napiwotzki, R.; Altmann, M.; Scholz, R.D. (2008-05-01)Context. Young, massive stars have been found in the distant Galactic halo. Dynamical ejection from the Galactic disc has been suggested as the origin of these "run-away stars". The so-called hyper-velocity stars have been ... -
Binaries discovered by the MUCHFUSS project SDSS J08205+0008 - An eclipsing subdwarf B binary with brown dwarf companion
Geier, S.; Schaffenroth, V.; Drechsel, H.; Heber, U.; Kupfer, T.; Tillich, A.; Ostensen, R.; Smolders, K.; Degroote, P.; Maxted, P.F.L.; Barlow, B.N.; Gansicke, B.T.; Marsh, T.R.; Napiwotzki, R. (2011)Hot subdwarf B stars (sdBs) are extreme horizontal branch stars believed to originate from close binary evolution. Indeed about half of the known sdB stars are found in close binaries with periods ranging from a few hours ... -
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. II. HE 1414-0848: A double degenerate with a mass close to the Chandrasekhar limit
Napiwotzki, R.; Koester, D.; Nelemans, G.; Yungelson, L.; Christlieb, N.; Renzini, A.; Reimers, D.; Drechsel, H.; Leibundgut, B. (2002-05)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 SNIa Progenitor surveY { SPY) we discovered that the white dwarf ... -
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 ... -
Binaries discovered by the SPY project: V. GD 687 – a massive double degenerate binary progenitor that will merge within a Hubble time
Geier, S.; Heber, U.; Kupfer, T.; Napiwotzki, R. (2010)The ESO SN Ia Progenitor Survey (SPY) aims at finding merging double degenerate binaries as candidates for supernova type Ia (SN Ia) explosions. A white dwarf merger has also been suggested to explain the formation of rare ... -
Binaries discovered by the SPY survey VI : Discovery of a low mass companion to the hot subluminous planetary nebula central star EGB5-a recently ejected common envelope?
Geier, S.; Napiwotzki, R.; Heber, U.; Nelemans, G. (2011)Hot subdwarf B stars (sdBs) in close binary systems are assumed to be formed via common envelope ejection. According to theoretical models, the amount of energy and angular momentum deposited in the common envelope scales ... -
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 ...