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Browsing by Author "Ostensen, R."
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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 ... -
Discovery of seven ZZ Ceti stars using a new photometric selection method
Voss, B.; Koester, D.; Ostensen, R.; Kepler, S.O.; Napiwotzki, R.; Homeier, D.; Reimers, D. (2006) -
HS 0705 6700: A new eclipsing sdB binary
Drechsel, H.; Heber, U.; Napiwotzki, R.; Ostensen, R.; Solheim, J.E.; Johannessen, F.; Schuh, S.L.; Deetjen, J.; Zola, S. (2001-12) -
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) -
The Hyper-MUCHFUSS project : probing the Galactic halo with sdB stars
Tillich, A.; Heber, U.; Geier, S.; Hirsch, H.; Maxted, P.F.L.; Gansicke, B.T.; Marsh, T.R.; Napiwotzki, R.; Ostensen, R.; Scholz, R.D. (2011)Context. High-velocity stars in the Galactic halo, e. g. the so-called hyper-velocity stars (HVS), are important tracers of the properties of the dark matter halo, in particular its mass. Aims. A search for the fastest ... -
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 ... -
Massive unseen companions to hot faint underluminous stars from SDSS (MUCHFUSS) - Analysis of seven close subdwarf B binaries
Geier, S.; Maxted, P.F.L.; Napiwotzki, R.; Ostensen, R.; Heber, U.; Hirsch, H.; Kupfer, T.; Muller, S.; Tillich, A.; Barlow, B.N.; Oreiro, R.; Ottosen, T.A.; Copperwheat, C.; Gansicke, B.T.; Marsh, T.R. (2011)The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding hot subdwarf stars with massive compact companions like massive white dwarfs (M > 1.0 ), neutron stars or stellar ... -
The MUCHFUSS project - Searching for hot subdwarf binaries with massive unseen companions : survey, target selection and atmospheric parameters
Geier, S.; Hirsch, H.; Tillich, A.; Maxted, P.F.L.; Bentley, S.J.; Ostensen, R.; Heber, U.; Gansicke, B.T.; Marsh, T.R.; Napiwotzki, R.; Barlow, B.N.; O'Toole, S. (2011)The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding sdBs with compact companions like supermassive white dwarfs (M > 1.0M⊙), neutron stars or black holes. The existence ... -
Six New ZZ Ceti Stars from the SPY and the HQS Surveys
Voss, B.; Koester, D.; Ostensen, R.; Napiwotzki, R.; Homeier, D.; Reimers, D. (Astronomical Society of the Pacific, 2007)We report on the discovery of six new ZZCeti stars. They were selected as candidates based on preparatory photometric observations of ob- jects from the Hamburg Quasar Survey (HQS), and based on the spectra of the Supernova ...