SDSS J013655.91+242546.0 - an A-type hyper-velocity star from the outskirts of the Galaxy (2009)
Tillich, A., Przybilla, N., Heber, U.
Hyper-velocity stars (HVS) are moving so fast that they are unbound to the Galaxy. Dynamical ejection by a supermassive black hole is favoured to explain their origin. Locating the place of birth of...
Koester, D., Voss, B., Napiwotzki, R., Christlieb, N., Homeier, D., Lisker, T., ...
The ESO Supernova Ia Progenitor Survey (SPY) took high-resolution spectra of more than 1000 white dwarfs and pre-white dwarfs. About two thirds of the stars observed are hydrogen-dominated DA white...
Geier, S., Edelmann, H., Heber, U., Morales-Rueda, L.
Substellar objects, like planets and brown dwarfs orbiting stars, are by-products of the star formation process. The evolution of their host stars may have an enourmous impact on these small...
The UV-Excess Survey of the Northern Galactic Plane (UVEX) (2009)
Groot, Paul J., Verbeek, K., Greimel, R., Irwin, M., Gonzalez-Solares, E., Gaensicke, B., ...
The UV-Excess Survey of the Northern Galactic Plane images a 10x185 degree wide band, centered on the Galactic Equator using the 2.5m Isaac Newton Telescope in four bands (U,g,r,HeI5875) down to...
Koester, D., Voss, B., Napiwotzki, R., Christlieb, N., Homeier, D., Lisker, T., ...
Original article can be found at: http://www.aanda.org/ Copyright The European Southern Observatory (ESO) DOI: 10.1051/0004-6361/200912531
Multi-wavelength photometric variation of PG1605+072 (2008)
Schuh, S., Dreizler, S., Heber, U., Jeffery, C. S., O'Toole, S. J., Cordes, O., ...
In a large coordinated attempt to further our understanding of the $p$-mode pulsating sdB star PG1605+072, the Multi-Site Spectroscopic Telescope (MSST) collaboration has obtained simultaneous...
New high resolution synthetic stellar libraries for the Gaia Mission (2008)
Sordo, R., Vallenari, A., Bouret, J. C., Brott, I., Edvardsson, B., Fremat, Y., ...
High resolution synthetic stellar libraries are of fundamental importance for the preparation of the Gaia Mission. We present new sets of spectral stellar libraries covering two spectral ranges: 300...
Time-series Spectroscopy and Photometry of the Pulsating Subdwarf B Star PG 1219+534 (KY UMa) (2008)
Reed, M. D., Eggen, J. R., Harms, S. L., Telting, J. H., Ostensen, R. H., O'Toole, S. J., ...
We present observations and analysis of time-series spectroscopy and photometry of the pulsating subdwarf B star PG 1219+534 (KY UMa). Subdwarf B stars are blue horizontal branch stars which have...
HVS7: a chemically peculiar hyper-velocity star (2008)
Przybilla, N., Nieva, M. F., Tillich, A., Heber, U., Butler, K., Brown, W. R.
Context: Hyper-velocity stars are suggested to originate from the dynamical interaction of binary stars with the supermassive black hole in the Galactic centre (GC), which accelerates one component...
Model Spectra of Hot Subdwarfs for the Gaia Mission (2008)
Hindson, L., Napiwotzki, R., Heber, U., Lemke, M.
The Gaia mission will provide an unprecedented 3D view of our galaxy, it will obtain astrometric, photometric and spectrographic data for roughly one billion stars. We are particularly interested in...
Subdwarf O Stars from SDSS and SPY (2008)
Hirsch, H. A., Heber, U., O'Toole, S. J.
We present the results of quantitative spectral analysis of sdOs from the SDSS database. Fitting the Balmer, HeI and HeII lines to non-LTE model spectra, we derived their effective temperatures,...
Geier, S., Heber, U., Napiwotzki, R.
We present new results from follow-up time-resolved spectroscopy of radial velocity variable hot subdwarfs from the SPY project. Medium resolution spectra were taken at the ESO NTT. Preliminary...
Binary sdB Stars with Massive Compact Companions (2008)
Geier, S., Karl, C., Edelmann, H., Heber, U., Napiwotzki, R.
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...
Metal Abundances of Subdwarf B Stars from SPY - a Pattern Emerges (2008)
Geier, S., Heber, U., Napiwotzki, R.
The formation of sdBs is still puzzling, as is the chemical composition of their atmospheres. While helium and other light elements are depleted relative to solar values, heavy elements are highly...
Searching for Hyper-Velocity Stars (2008)
Tillich, A., Heber, U., Hirsch, H.
We present our survey for subluminous hyper-velocity candidates, which has been successfully initiated at the ESO NTT and the Calar Alto 3.5 m telescope.
Towards Asteroseismology of PG1605+072 (2008)
Tillich, A., Heber, U., O'Toole, S. J., Østensen, R., Schuh, S.
We present our attempt to characterise the frequency spectrum of the bright V 361 Hya star PG1605$+$072 from atmospheric parameter and radial velocity variations through a spectroscopic approach....
Przybilla, N., Nieva, M. F., Heber, U., Firnstein, M., Butler, K., Napiwotzki, R., ...
Context: Hyper-velocity stars move so fast that only a supermassive black hole (SMBH) seems to be capable to accelerate them. Hence the Galactic centre (GC) is their only suggested place of origin....
Przybilla, N., Nieva, M.A., Heber, U., Firnstein, M., Butler, K., Napiwotzki, R., ...
Original article can be found at: http://www.aanda.org/ Copyright The European Southern Observatory DOI: 10.1051/0004-6361:200809391
Geier, S., Heber, U., Napiwotzki, R.
Original paper can be found at: http://astrosociety.org/pubs/cs/381.html Copyright ASP
Binary sdB Stars with Massive Compact Companions. (2008)
Geier, S., Karl, C., Edelmann, H., Heber, U., Napiwotzki, R.
Original paper can be found at: http://astrosociety.org/pubs/cs/381.html Copyright ASP
Metal Abundances of Subdwarf B Stars from SPY - a Pattern Emerges. (2008)
Geier, S., Heber, U., Napiwotzki, R.
Original paper can be found at: http://astrosociety.org/pubs/cs/381.html Copyright ASP
Model Spectra of Hot Subdwarfs for the Gaia Mission. (2008)
Hindson, L., Napiwotzki, R., Heber, U., Lemke, M.
Original paper can be found at: http://astrosociety.org/pubs/cs/381.html Copyright ASP
Hypervelocity Stars: Young and Heavy or Old and Light? (2008)
Heber, U., Hirsch, H., Edelmann, H., Napiwotzki, R., O'Toole, S., Brown, W., ...
Original paper can be found at: http://astrosociety.org/pubs/cs/381.html Copyright ASP
Tidal synchronization of the subdwarf B binary PG 0101+039 (2007)
Geier, S., Nesslinger, S., Heber, U., Randall, S. K., Edelmann, H., Green, E. M.
Tidally locked rotation is a frequently applied assumption that helps to measure masses of invisible compact companions in close binaries. The calculations of synchronization times are affected by...
Tillich, A., Heber, U., O'Toole, S. J., Østensen, R., Schuh, S.
Stellar oscillations are an important tool to probe the interior of a star. Subdwarf B stars are core helium burning objects, but their formation is poorly understood as neither single star nor...
Time resolved spectroscopy of the multiperiodic pulsating subdwarf B star PG1605+072 (2007)
Tillich, A., Heber, U., O'Toole, S. J.
We present results for the 2m spectroscopic part of the MultiSite Spectroscopic Telescope campaign, which took place in May/June 2002. In order to perform an asteroseismological analysis on the...
Binary White Dwarfs in the Supernova Ia Progenitor Survey. (2007)
Napiwotzki, R., Karl, C., Nelemans, G., Yungelson, L., Christlieb, N., Drechsel, H., ...
The Subdwarf B + White Dwarf Binary KPD 1930+2752, a Supernova Type Ia Progenitor Candidate. (2007)
Geier, S., Nesslinger, S., Heber, U., Przybilla, N., Napiwotzki, R.
Spectroscopic Analysis of Subluminous B Stars in Binaries with Compact Companions. (2007)
Geier, S., Karl, C., Edelmann, H., Heber, U., Napiwotzki, R.
Hot subluminous O stars from the SDSS (2006)
Hirsch, H. A., Heber, U., O'Toole, S. J.
We carried out a quantitative spectral analysis of 73 hot subluminous O-stars selected from the SDSS spectral database. While the helium deficient sdOs are scattered over a wide range of effective...
3D-Kinematics of White Dwarfs from the SPY-Project (2006)
Richter, R., Heber, U., Napiwotzki, R.
We present a progress report on the kinematical analysis of the entire SPY (ESO SN Ia Progenitor surveY) sample of about one thousand white dwarfs and hot subdwarfs. In a previous study (Pauli et al....
The subdwarf B + white dwarf binary KPD 1930+2752 - a Supernova Type Ia progenitor candidate (2006)
Geier, S., Nesslinger, S., Heber, U., Przybilla, N., Napiwotzki, R.
The nature of the progenitors of type Ia supernovae is still under controversial debate. KPD 1930+2752 is one of the best SN Ia progenitor candidates known today. The object is a double degenerate...
Spectroscopic Analysis of subluminous B Stars in Binaries with compact Companions (2006)
Geier, S., Karl, C., Edelmann, H., Heber, U., Napiwotzki, R.
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...
Heavy metals and lead isotopes in sdB stars (2006)
We present a detailed abundance analysis of high-resolution ultraviolet echelle spectra of five subdwarf B stars obtained with HST-STIS The goal of our observations was to test the hypothesis that...
Time resolved spectroscopy of the multiperiodic pulsating subdwarf B star PG1605+072 (2006)
Tillich, A., Heber, U., O'Toole, S. J.
We present results for the 2m spectroscopic part of the MultiSite Spectroscopic Telescope campaign, which took place in May/June 2002. In order to perform an asteroseismological analysis on the...
Geier, S., Karl, C., Edelmann, H., Heber, U., Napiwotzki, R.
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...
Geier, S., Nesslinger, S., Heber, U., Przybilla, N., Napiwotzki, R.
The nature of the progenitors of type Ia supernovae is still under controversial debate. KPD 1930+2752 is one of the best SN Ia progenitor candidates known today. The object is a double degenerate...
Stroeer, A., Heber, U., Lisker, T., Napiwotzki, R., Dreizler, S., Christlieb, N., ...
We address the origin and evolutionary status of hot subdwarf stars by studying the optical spectral properties of 58 subdwarf O (sdO) stars. Combining them with the results of our previously studied...
O'Toole, S. J., Napiwotzki, R., Heber, U., Drechsel, H., Frandsen, S., Grundahl, F., ...
The variable sdB known as V46 in the globular cluster M4 has remained enigmatic since its discovery almost 10 years ago. We present here radial velocity measurements obtained from medium-resolution...
Abundance studies of sdB stars using UV echelle HST/STIS spectroscopy (2006)
Aims: We test the hypothesis that the pulsations in sdB stars are correlated with the surface abundances of iron-group elements. Any correlation might explain why, when given two spectroscopically...
3D kinematics of white dwarfs from the SPY project. II. (2006)
Pauli, E.M., Napiwotzki, R., Heber, U., Altmann, M., Odenkirchen, M.
Spectroscopic Analysis of sdB Binaries from the SPY Project (2005)
Karl, C., Heber, U., Napiwotzki, R., Geier, S.
In the course of our search for double degenerate binaries as potential progenitors of type Ia supernovae with the ESO VLT (ESO SN Ia Progenitor SurveY SPY) several new subdwarf B (sdB) binaries with...
Improved helium line formation for EHe stars (2005)
Przybilla, N., Butler, K., Heber, U., Jeffery, C. S.
Quantitative analyses of extreme helium stars to date face the difficulty that theory fails to reproduce the observed helium lines in their entirety, wings and line cores. Here, we demonstrate how...
Non-LTE metal abundances in V652 Her and HD144941 (2005)
Przybilla, N., Nieva, M. F., Heber, U., Jeffery, C. S.
Two evolutionary scenarios are proposed for the formation of extreme helium stars: a post-AGB star suffering from a late thermal pulse, or the merger of two white dwarfs. An identification of the...
US 708 - An unbound hyper-velocity subluminous O star (2005)
Hirsch, H. A., Heber, U., O'Toole, S. J., Bresolin, F.
We report the discovery of an unbound hyper-velocity star, US 708, in the Milky Way halo, with a heliocentric radial velocity of +708+-15km/s. A quantitative NLTE model atmosphere analysis of optical...
HS0702+6043: A star showing both short-period p-mode and long-period g-mode oscillations (2005)
Schuh, S., Huber, J., Dreizler, S., Heber, U., O'Toole, S. J., Green, E. M., ...
[Context.] The hot subdwarf B star HS0702+6043 is known as a large-amplitude, short-period p-mode pulsator of the EC14026 type. Its atmospheric parameters place it at the common boundary between the...
Schuh, S., Huber, J., Dreizler, S., Green, E. M., Stahn, T., Randall, S., ...
The discovery of a long-period g-mode oscillation in the previously known short-period p-mode sdB pulsator HS0702+6043 makes this star an extraordinary object, unique as a member of the family of sdB...
Time resolved spectroscopy of KPD1930+2752 (2005)
Geier, S., Heber, U., Przybilla, N., Kudritzki, R. P.
We present the analysis of 200 high-resolution and 150 low-resolution spectra of the pulsating subdwarf close binary KPD 1930+2752 obtained with the Keck and the Calar Alto 2.2 m telescopes. Using...
3D kinematics of white dwarfs from the SPY project II (2005)
Napiwotzki, R., Heber, U., Altmann, M., Odenkirchen, M.
We present the kinematics of a sample of 398 DA white dwarfs from the SPY project (ESO SN Ia Progenitor surveY) and discuss kinematic criteria for distinguishing thin-disk, thick-disk, and halo...
Przybilla, N., Butler, K., Heber, U., Jeffery, C. S.
Quantitative analyses of low-mass hydrogen-deficient (super-)giant stars - so-called extreme helium stars - to date face two major difficulties. First, theory fails to reproduce the observed helium...
Aungwerojwit, A., Gaensicke, B. T., Rodriguez-Gil, P., Harlaftis, E. T., Papadimitriou, C., ...
We present time-resolved optical spectroscopy and photometry of four relatively bright (V~14.0-15.5) long-period cataclysmic variables (CVs) discovered in the Hamburg Quasar Survey: HS0139+0559,...
High resolution spectroscopy of bright subdwarf B stars - I. Radial velocity variables (2005)
Edelmann, H., Heber, U., Altmann, M., Karl, C., Lisker, T.
Radial velocity curves for 15 bright subdwarf B binary systems have been measured using high precision radial velocity measurements from high S/N optical high-resolution spectra. In addition, two...
O'Toole, S. J., Heber, U., Jeffery, C. S., Dreizler, S., Schuh, S. L., Woolf, V. M., ...
We present results and analysis for the 2m spectroscopic part of the MultiSite Spectroscopic Telescope (MSST) campaign undertaken in May/June 2002. The goal of the project was to observe the...
Rotation velocities of white dwarfs. III. DA stars with convective atmospheres (2005)
Karl, C., Napiwotzki, R., Heber, U., Dreizler, S., Koester, D., Reid, I.N.
Discovery of magnetic fields in hot subdwarfs (2005)
O'Toole, S. J., Jordan, S., Friedrich, S., Heber, U.
We present polarisation measurements of sdB and sdO stars using FORS1 on the VLT. The observations were made as part of a project to determine whether magnetic fields in two super-metal-rich stars...
O'Toole, S. J., Heber, U., Jeffery, C. S., Dreizler, S., Schuh, S. L., Woolf, V. M., ...
We present results and analysis for the 2 m spectroscopic part of the MultiSite Spectroscopic Telescope (MSST) campaign undertaken in May/June 2002. The goal of the project was to observe the...
Subluminous O Stars from the ESO Supernova Progenitor Survey - Observation versus Theory. (2005)
Stroeer, A., Heber, U., Lisker, T., Napiwotzki, R., Dreizler, S.
Subdwarf B Stars from the ESO Supernova Ia Progenitor Survey -- Observation versus Theory. (2005)
Lisker, T., Heber, U., Napiwotzki, R., Christlieb, N., Han, Z., Homeier, D., ...
The Mass of the sdB Primary of the Binary HS 2333+3927. (2005)
Heber, U., Drechsel, H., Karl, C., Ostensen, R., Folkes, S.L., Napiwotzki, R., ...
New Results from the Supernova Ia Progenitor Survey. (2005)
Napiwotzki, R., Karl, C., Nelemans, G., Yungelson, L., Christlieb, N., Drechsel, H., ...
Rotation Velocities of DA White Dwarfs with Convective Atmospheres. (2005)
Karl, C., Heber, U., Napiwotzki, R., Dreizler, S., Koester, D., Reid, I.N.
Rotation Velocities of DA White Dwarfs with Convective Atmospheres. (2005)
Karl, C., Heber, U., Napiwotzki, R., Dreizler, S., Koester, D., Reid, I.N.
HE 0437-5439: an unbound hypervelocity main-sequence B-type star. (2005)
Edelmann, H., Napiwotzki, R., Heber, U., Christlieb, N., Reimers, D.
Original article can be found at: http://www.iop.org/EJ/journal/apjl Copyright American Astronomical Society DOI: 10.1086/498940 [Full text of this article is not available in the UHRA]
Discovery of a Long-Period Photometric Variation in the V361 Hya Star HS 0702+6043 (2004)
Schuh, S., Huber, J., Green, E. M., O'Toole, S. J., Dreizler, S., Heber, U., ...
We report the discovery of a long-period g-mode oscillation in the previously known short-period p-mode sdB pulsator HS 0702+6043. This makes this star an extraordinary object, unique as a member of...
3D-Kinematics of White Dwarfs from the SPY-Project (2004)
Pauli, E-M., Heber, U., Napiwotzki, R., Altmann, M., Odenkirchen, M.
We present kinematics of a sample of 398 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...
Subluminous O stars from the ESO Supernova Progenitor Survey - Observation versus Theory (2004)
Stroeer, A., Heber, U., Lisker, T., Napiwotzki, R., Dreizler, S.
The ESO Supernova Progenitor Survey (SPY) has identified 58 (mostly helium-rich) subluminous O stars. We use the Balmer line strength to distinguish sdO from He-sdO (no Balmer lines) and present the...
Discovery of magnetic fields in hot subdwarfs (2004)
O'Toole, S. J., Jordan, S., Friedrich, S., Heber, U.
We present initial results of a project to measure mean longitudinal magnetic fields in a group of sdB/OB/O stars. The project was inspired by the discovery of three super-metal-rich sdOB stars, each...
Lisker, T., Heber, U., Napiwotzki, R., Christlieb, N., Han, Z., Homeier, D., ...
We present the analysis of a high-resolution, high-quality sample of optical spectra for 76 subdwarf B (sdB) stars from the ESO Supernova Ia Progenitor Survey (SPY). Effective temperature, surface...
HS 2333 3927: A new sdB dM binary with a large reflection effect (2004)
Heber, U., Drechsel, H., Ostensen, R., Karl, C., Napiwotzki, R., Altmann, M., ...
Close binary EHB stars from SPY (2004)
Napiwotzki, R., Karl, C., Lisker, T., Heber, U., Christlieb, N., Reimers, D., ...
Atmospheric parameters and abundances of sdB stars (2004)
We summarize recent results of quantitative spectral analyses using NLTE and metal line-blanketed LTE model atmospheres. Temperatures and gravities derived for hundreds of sdB stars are now available...
Detection of a companion to the pulsating sdB Feige 48 (2004)
O'Toole, S. J., Heber, U., Benjamin, R. A.
We present the discovery of a binary companion to the pulsating sdB Feige 48. Using HST/STIS and archival FUSE spectra, we measure a period of 0.376+/-0.003 d and a velocity semi-amplitude of...
Double degenerates and progenitors of supernovae type Ia (2004)
Napiwotzki, R., Yungelson, L., Nelemans, G., Marsh, T. R., Leibundgut, B., Renzini, A., ...
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....
Spectral Types and Masses of White Dwarfs in Globular Clusters (2004)
Moehler, S., Koester, D., Zoccali, M., Ferraro, F. R., Heber, U., Napiwotzki, R., ...
White dwarfs in globular clusters offer additional possibilities to determine distances and ages of globular clusters, provided their spectral types and masses are known. We therefore started a...
Close binary EHB stars from SPY (2004)
Napiwotzki, R., Karl, C. A., Lisker, T., Heber, U., Christlieb, N., Reimers, D., ...
We present the results of a radial velocity (RV) survey of 46 subdwarf B (sdB) and 23 helium-rich subdwarf O (He-sdO) stars. We detected 18 (39%) new sdB binary systems, but only one (4%) He-sdO...
Close binary white dwarfs and supernovae IA (2004)
Christlieb , N., Drechsel , H., Heber , U., Homeier , D., Karl , C., Koester , D., ...
Informamos sobre el estado actual de los surveys" de velocidades radiales para binarias de enanas blancas (degeneradas dobles - DDs) incluyendo SPY (Exploración ESO de progenitoras de supernovas Ia)...
Spectroscopic analysis of sdB stars from the ESO Supernova Ia Progenitor Survey (2004)
Lisker, T., Heber, U., Napiwotzki, R., Christlieb, N., Han, Z., Homeier, D., ...
Spectral types and masses of white dwarfs in globular clusters (2004)
Moehler, S., Koester, D., Zoccali, M., Ferraro, F.R., Heber, U., Napiwotzki, R., ...
Double Degenerate and Progenitors of Supernovae Type Ia. (2004)
Napiwotzki, R., Yungelson, L., Nelemans, G., Marsh, T.R., Leibundgut, B., Renzini, A., ...
HS 2333 + 3927: a new sdB binary with a large reflection effect. (2004)
Karl, C., Heber, U., Drechsel, H., Napiwotzki, R., Altmann, M., Ostensen, R., ...
“The original publication is available at www.springerlink.com”. Copyright Springer. DOI: 10.1023/B:ASTR.0000044334.98860.ab [Full text of this article is not available in the UHRA]
FUSE Observations of EC14026 Stars. (2004)
Chayer, P., Fontaine, G., Fontaine, M., Lamontagne, R., Wesemael, F., Dupuis, J., ...
“The original publication is available at www.springerlink.com”. Copyright Springer. DOI: 10.1023/B:ASTR.0000044344.92680.b8 [Full text of this article is not available in the UHRA]
Spectroscopic analysis of sdB stars from the ESO Supernova Ia Progenitor Survey (2003)
Lisker, T., Heber, U., Napiwotzki, R., Christlieb, N., Reimers, D., Homeier, D.
We report on the analysis of high-resolution optical spectra for 77 subdwarf B (sdB) stars from the ESO Supernova Ia Progenitor Survey. Effective temperature, surface gravity, and photospheric helium...
Karl, C. A., Napiwotzki, R., Nelemans, G., Christlieb, N., Koester, D., Heber, U., ...
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...
MSST observations of the pulsating sdB star PG1605+072 (2003)
O'Toole, S. J, Falter, S., Heber, U., Jeffery, C. S., Dreizler, S., Schuh, S. L., ...
We present the first results from the MultiSite Spectroscopic Telescope (MSST) observations of the sdBV star PG1605+072. Pulsating sdB stars (also known as EC14026 stars) offer the chance to gain new...
HST/STIS observations of sdBV stars: testing diffusion and pulsation theory (2003)
O'Toole, S. J., Heber, U., Chayer, P., Fontaine, G., O'Donoghue, D., Charpinet, S.
We present the initial results of an abundance analysis of echelle UV spectra of 5 hot subdwarf B (sdB) stars. These stars have been identified as core helium burning objects on the extreme...
Spectral analysis of sdB Stars from the Hamburg Quasar Survey (2003)
Edelmann, H., Heber, U., Hagen, H.J., Dreizler, S., Napiwotzki, R., Engels, D., ...
3D kinematics of white dwarfs from the SPY project (2003)
Pauli, E.M., Napiwotzki, R., Altmann, M., Heber, U., Odenkirchen, M., Kerber, F.
Spectral analysis of sdB stars from the Hamburg Quasar Survey (2003)
Edelmann, H., Heber, U., Lemke, M., Dreizler, S., Napiwotzki, R., ...
We present the results of a spectral analysis of a large sample of subdwarf B stars selected from follow-up observations of candidates from the Hamburg Quasar Survey. Fundamental parameters...
Simultaneous time-series spectroscopy and multi-band photometry of the sdBV PG 1605+072 (2003)
Falter, S., Heber, U., Dreizler, S., Schuh, S. L., Cordes, O., Edelmann, H.
We present time-series spectroscopy and multi-band photometry of the sdBV PG 1605+072 carried out simultaneously at the Calar Alto 2.2m and 3.5m telescopes. The periodogram analysis of the radial...
3D kinematics of white dwarfs from the SPY project (2003)
Napiwotzki, R., Altmann, M., Heber, U., Odenkirchen, M., Kerber, F.
We present kinematics of a sample of 107 DA white dwarfs from the SPY project and discuss kinematic criteria for a distinction of thin disk, thick disk, and halo populations. This is the first...
Stellar Wind Signatures in sdB Stars (2003)
Heber, U., Maxted, P.F.L., Marsh, T.R., Knigge, C., Drew, J.E.
NLTE Spectral Analysis of Iron Group Elements in the Hot Subluminous O-star BD+28 4211. (2003)
Ramspeck, M., Haas, S., Napiwotzki, R., Heber, U., Deetjen, J., Dreizler, S.
Subluminous B Stars and Progenitors of Helium Core White Dwarfs (2002)
Subluminous B (sdB) stars can result from stable Roche lobe overflow or common envelope ejection in close binary systems. The companions are either low mass main sequence stars or white dwarfs. We...
Stellar wind signatures in sdB stars? (2002)
Heber, U., Maxted, P. F. L., Marsh, T. R., Knigge, C., Drew, J E.
Subdwarf B (sdB) stars form the blue end of the horizonal branch (EHB). Their peculiar atmospheric abundance patterns are due to diffusion processes. However, diffusion models fail to explain these...
Towards asteroseismology of the non-radial pulsating sdB star PG 1605+072 (2002)
Falter, S., Heber, U., Dreizler, S., Schuh, S. L., Cordes, O.
The recently discovered new class of sdB pulsators (sdBV) offers a powerful possibility for the investigation of their interior and thus their evolutionary history. The first step towards applying...
Stellar wind signatures in sdB stars? (2002)
Heber, U., Maxted, P. F. L., Marsh, T. R., Knigge, C., Drew, J. E.
Subdwarf B (sdB) stars form the blue end of the horizonal branch. Their peculiar atmospheric abundance patterns are due to diffusion processes. However, diffusion models fail to explain these...
Heber, U., Dreizler, S., Schuh, S. L., O'Toole, S., Jeffery, C. S.
A small fraction of subluminous B stars show short-period, multiperiodic light variations and form the new class of pulsating star known as EC 14026 variables, after the prototype. The Multi-Site...
Time-series Spectroscopy of Pulsating sdB stars III: Line Indices of PG1605+072 (2002)
O'Toole, S. J., Kjeldsen, H., Bedding, T. R., Dall, T. H., Heber, U.
We present the detection and analysis of line index variations in the pulsating sdB star PG 1605+072. We have found a strong dependence of line index amplitude on Balmer line order, with high-order...
The Rotational Velocity of Helium-rich Pre-White Dwarfs (2002)
Rauch, T., Koeper, S., Dreizler, S., Werner, K., Heber, U., Reid, I. N.
Previous investigations on hydrogen-rich white dwarfs generally yield only very small rotational velocities (v_rot sin i). We have analyzed line profiles in high-resolution optical spectra of eight...
Search for double degenerate progenitors of supernovae type Ia with SPY (2002)
Napiwotzki, R., Christlieb, N., Drechsel, H., Heber, U., Homeier, D., ...
We report on a large survey for double degenerate (DD) binaries as potential progenitors of type Ia supernovae with the UVES spectrograph at the ESO VLT (SN Ia Progenitor surveY - SPY). About 560...
Search for double degenerate progenitors of supernovae type Ia with SPY (2002)
Napiwotzki, R., Drechsel, H., Heber, U., Karl, C., Christlieb, N., ...
We report on a large survey 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).
Double degenerates from the supernova Ia progenitor survey (SPY) (2002)
Karl, C., Napiwotzki, R., Heber, U., Lisker, T., Nelemans, G., Christlieb, N., ...
We report on follow-up observations of double degenerate (DD) white dwarfs from the Supernovae Ia Progenitor Survey (SPY). Orbital parameters of four systems, including a massive short period system,...
Orbital periods of twenty two subdwarf B stars (2002)
Morales-Rueda, L., Maxted, P. F. L., Marsh, T. R., North, R. C., Heber, U.
Subdwarf B (sdB) stars are thought to be core helium burning stars with low mass hydrogen envelopes. In recent years it has become clear that many sdB stars lose their hydrogen through interaction...
Search for progenitors of supnernovae type Ia with SPY (2002)
Napiwotzki, R., Christlieb, N., Drechsel, H., Heber, U., Homeier, D., ...
We have started a large survey 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). About...
Resolving subdwarf B stars in binaries by HST imaging (2002)
Heber, U., Moehler, S., Napiwotzki, R., Thejll, P., Green, E.
Photometry of four binary subdwarf B stars and the nature of their unseen companion stars (2002)
Maxted, P. F. L., Marsh, T. R., Heber, U., Morales-Rueda, L., North, R. C., Lawson, W. A.
We present lightcurves of four binary subdwarf B stars, Ton 245, Feige 11, PG1432+159 and PG1017-086. We also present new spectroscopic data for PG1017-086 from which we derive its orbital period,...
Resolving subdwarf B stars in binaries by HST imaging (2002)
Heber, U., Moehler, S., Napiwotzki, R., Thejll, P., Green, E. M.
The origin of subluminous B stars is still an unsolved problem in stellar evolution. Single star as well as close binary evolution scenarios have been invoked but until now have met with little...
HS 0705 6700: A new eclipsing sdB binary (2001)
Drechsel, H., Heber, U., Napiwotzki, R., Ostensen, R., Solheim, J.E., Johannessen, F., ...
Rauch, T., Heber, U., Werner, K.
We present a spectral analysis of the sdO central star K 648 based on medium-resolution optical and high-resolution UV spectra. The photospheric parameters are determined by means of state-of-the-art...
HS 0705+6700: a new eclipsing sdB binary (2001)
Drechsel, H., Heber, U., Napiwotzki, R., Ostensen, R., Johannessen, F., ...
We report the discovery of an eclipsing binary - HS 0705+6700 - being an sdB star with a faint companion. From its light curve the orbital period of 8263.87 s, the mass ratio of the system q = 0.28,...
Binaries discovered by the SPY project. I. HE 1047-0436: A subdwarf B white dwarf syste (2001)
Napiwotzki, R., Edelmann, H., Heber, U., Karl, C., Drechsel, H., Pauli, E.M., ...
Early type stars at high galactic latitudes I. Ten young massive B-type stars (2001)
Ramspeck, M., Heber, U., Moehler, S.
We present the results of quantitative spectral analyses of ten apparently normal B-type stars. These stars were found to be young massive B-type stars at distances of z=2.6 to 7.6 kpc from the...
Ramspeck, M., Heber, U., Edelmann, H.
We present the result of differential spectral analyses of a further four apparently normal B-type stars. Abundance anomalies (e.g. He, C, N enrichment), slow rotation and/or high gravities suggest...
Binaries discovered by the SPY project I. HE 1047-0436: a subdwarf B + white dwarf system (2001)
Napiwotzki, R., Edelmann, H., Heber, U., Karl, C., Drechsel, H., ...
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 SN Ia Progenitor surveY - SPY) we discovered...
The binary fraction of extreme horizontal branch stars (2001)
Maxted, P. F. L., Heber, U., Marsh, T. R., North, R. C.
(Abbreviated) We have used precise radial velocity measurements of subdwarf-B stars from the Palomar-Green catalogue to look for binary extreme horizontal branch (EHB) stars. We identify 36 EHB stars...
Search for progenitors of supernovae type Ia with SPY (2001)
Napiwotzki, R., Christlieb, N., Drechsel, H., Heber, U., Homeier, D., ...
Spectral Analysis of sdB Stars from the Hamburg ESO Survey. (2001)
Edelmann, H., Heber, U., Napiwotzki, R., Lemke, M., Christlieb, N.
Metal abundances of sdB stars. (2001)
Edelmann, H., Heber, U., Napiwotzki, R.
Original article can be found at: http://www3.interscience.wiley.com Copyright WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/1521-3994(200112)322:5/63.0.CO;2-M Full text of this article is...
Search for progenitors of supernovae type Ia with SPY. (2001)
Napiwotzki, R., Christlieb, N., Drechsel, H., Hagen, H.J., Heber, U., Homeier, D., ...
‘The definitive version is available at www3.interscience.wiley.com .' Copyright WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/1521-3994(200112)322:5/63.0.CO;2-I [Full text of this...
The stellar content of the Hamburg/ESO survey. I. Automated selection of DA white dwarfs (2000)
Christlieb, N., Wisotzki, L., Reimers, D., Homeier, D., Koester, D., Heber, U.
We describe automatic procedures for the selection of DA white dwarfs in the Hamburg/ESO objective-prism survey (HES). For this purpose, and the selection of other stellar objects (e.g., metal-poor...
Heber, U., Reid, I. N., Werner, K.
Three members of the new class of pulsating sdB stars (sdBV or EC 14026 stars) are analysed from Keck HIRES spectra using line blanketed NLTE and LTE model atmospheres. Atmospheric parameters (Teff,...
Moehler, S., Sweigart, A. V., Landsman, W. B., Heber, U.
Atmospheric parameters (effective temperature Teff, surface gravity log g), masses and helium abundances are derived for 42 hot horizontal branch (HB) stars in the globular cluster NGC 6752. For 19...
The Schweizer-Middleditch star revisited (2000)
Burleigh, M. R., Heber, U., O'Donoghue, D., Barstow, M. A.
We have re-observed and re-analysed the optical spectrum of the Schweizer-Middleditch star, a hot subdwarf which lies along almost the same line-of-sight as the centre of the historic SN1006...
First VLT spectra of white dwarfs in a globular cluster (2000)
Moehler, S., Heber, U., Napiwotzki, R., Koester, D., Renzini, A.
We present the first spectra obtained with the Very Large Telescope for white dwarfs in a globular cluster. Estimates of atmospheric parameters are obtained and compared to evolutionary tracks. We...
First VLT spectra of white dwarfs in a globular cluster. (2000)
Moehler, S., Heber, U., Napiwotzki, R., Koester, D., Renzini, A.
Spectral analysis of four multi mode pulsating sdB stars (1999)
Heber, U., Reid, I. N., Werner, K.
Four members of the new class of pulsating sdB stars are analysed from Keck HIRES spectra using NLTE and LTE model atmospheres. Atmospheric parameters (Teff, log g, log(He/H)), metal abundances and...
Spectral analysis of the multi mode pulsating subluminous B star PG1605+072 (1999)
Heber, U., Reid, I. N., Werner, K.
PG 1605+072 has unique pulsational properties amongst the members of the new class of pulsating sdB (EC 14026) stars. It has the longest periods and the richest, most puzzling frequency spectrum (55...
Moehler, S., Sweigart, A. V., Landsman, W. B., Heber, U., Catelan, M.
Atmospheric parameters (Teff, log g and log(He/H)) are derived for 42 hot horizontal branch (HB) stars in the globular cluster NGC 6752. For 19 stars MgII and FeII lines are detected indicating an...
BUSCA: A Telescope Instrumentation for Simultaneous Imaging in 4 Optical Bands (1999)
Reif, K., Bagschik, K., De Boer, K. S., Schmoll, J., Mueller, Ph., Poschmann, H, ...
The "Bonn University Simultaneous CAmera" (BUSCA) is a CCD camera system which allows simultaneous direct imaging of the same sky area in four colors. The optics are designed for an f/8 beam and four...
Spectral analysis of hot subluminous stars. (1999)
Heber, U., Edelmann, H., Lemke, M., Napiwotzki, R., Engels, D.
Spectral analysis of the binary sdB star Feige 36. (1999)
Edelmann, H., Heber, U., Napiwotzki, R., Reid, I.N., Saffer, R.
Moehler, S., Heber, U., Lemke, M., Napiwotzki, R.
Two UV brights stars in globular clusters, ROA 5701 (omega 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...
The UV bright star ZNG 1 in M 5 (1998)
We report the results of H_alpha imaging and UV spectroscopy with the Hubble Space Telescope of the hot post-AGB star ZNG 1 in M 5 and its suspected planetary nebula.
PG1323-086 and PG1704+222 - two post-AGB stars at high galactic latitudes (1998)
Two high galactic latitude B-type stars, PG1323-086 and PG1704+222, are analysed from low and medium resolution optical spectra and Stroemgren photometry. A differential abundance analysis for He, C,...
Masses and Gravities of Blue Horizontal Branch Stars Revisited (1997)
Heber, U., Moehler, S., Reid, I. N.
Previous spectroscopic analyses of Blue Horizontal Branch (BHB) stars in six globular clusters revealed too low masses in four clusters when compared to canonical evolutionary theory, while the...
NLTE spectral analysis of helium-rich sdO stars from the southern HK survey. (1996)
Drilling, J.S., Napiwotzki, R., Dreizler, S., Heber, U., Beers, T.C.
The Rate of Photosynthesis in Isolated Chloroplasts (1962)
Chloroplasts were isolated using aqueous and nonaqueous procedures. Aqueous chloroplasts lost approximately 50 per cent, of their soluble proteins during isolation. Nonaqueous chloroplasts retained...
Schönknecht, G, Neimanis, S, Katona, E, Gerst, U, Heber, U
Under conditions (0.2% CO2; 1% O2) that allow high rates of photosynthesis, chlorophyll fluorescence was measured simultaneously with carbon assimilation at various light intensities in spinach...
Hauser, M., Eichelmann, H., Oja, V., Heber, U., Laisk, A.
Leaves of Brassica oleracea, Helianthus annuus, and Nicotiana rustica were exposed for 20 s to high concentrations of CO2. CO2 uptake by the leaf, which was very fast, was measured as a transient...
Role of Ascorbate in Detoxifying Ozone in the Apoplast of Spinach (Spinacia oleracea L.) Leaves.
Luwe, MWF., Takahama, U., Heber, U.
Both reduced and oxidized ascorbate (AA and DHA) are present in the aqueous phase of the extracellular space, the apoplast, of spinach (Spinacia oleracea L.) leaves. Fumigation with 0.3 [mu]L L-1 of...
Effects of Anaerobiosis on Chlorophyll Fluorescence Yield in Spinach (Spinacia oleracea) Leaf Discs.
When spinach (Spinacia oleracea) leaf discs were incubated in a dark anaerobic environment, the chlorophyll fluorescence yield was much increased relative to the aerobic control. Occasionally, the...
Schönknecht, G, Neimanis, S, Katona, E, Gerst, U, Heber, U
Under conditions (0.2% CO2; 1% O2) that allow high rates of photosynthesis, chlorophyll fluorescence was measured simultaneously with carbon assimilation at various light intensities in spinach...
Hauser, M., Eichelmann, H., Oja, V., Heber, U., Laisk, A.
Leaves of Brassica oleracea, Helianthus annuus, and Nicotiana rustica were exposed for 20 s to high concentrations of CO2. CO2 uptake by the leaf, which was very fast, was measured as a transient...
Role of Ascorbate in Detoxifying Ozone in the Apoplast of Spinach (Spinacia oleracea L.) Leaves.
Luwe, MWF., Takahama, U., Heber, U.
Both reduced and oxidized ascorbate (AA and DHA) are present in the aqueous phase of the extracellular space, the apoplast, of spinach (Spinacia oleracea L.) leaves. Fumigation with 0.3 [mu]L L-1 of...
Effects of Anaerobiosis on Chlorophyll Fluorescence Yield in Spinach (Spinacia oleracea) Leaf Discs.
When spinach (Spinacia oleracea) leaf discs were incubated in a dark anaerobic environment, the chlorophyll fluorescence yield was much increased relative to the aerobic control. Occasionally, the...
MASSES AND GRAVITIES OF BLUE HORIZONTAL BRANCH (BHB) STARS REVISITED U. Heber
Moehler Reid Astronomisches, U. Heber, S. Moehler, I. N. Reid
Previous spectroscopic analyses of Blue Horizontal Branch (BHB) stars in six globular clusters revealed too low masses in four clusters when compared to canonical evolutionary theory, while the...