Publications (23)
Hot subdwarf stars in close-up view IV. Helium abundances and the He isotopic anomaly of subdwarf B star
S. Geier, U. Heber, H. Edelmann +5
Atmospheric parameters and helium abundances of 44 bright subdwarf B stars have been determined. More than half of our sample consists of newly discovered stars from the Edinburgh…
Simultaneous time-series spectroscopy and multi-band photometry of the sdBV PG 1605+072
S. Falter, U. Heber, S. Dreizler +3
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 analysi…
Helium abundances and the helium isotope anomaly of sdB stars
S. Geier, U. Heber, H. Edelmann +5
Helium abundances and atmospheric parameters have been determined from high resolution spectra for a new sample of 46 bright hot subdwarf B (sdB) stars. The helium abundances have…
Binaries discovered by the SPY project I. HE 1047-0436: a subdwarf B + white dwarf system
R. Napiwotzki, H. Edelmann, U. Heber +4
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 - S…
Spectral analysis of sdB stars from the Hamburg Quasar Survey
H. Edelmann, U. Heber, H. -J. Hagen +4
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 p…
Orbital solutions of eight close sdB binaries and constraints on the nature of the unseen companions
S. Geier, R. H. Oestensen, U. Heber +9
The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding hot subdwarf stars (sdBs) with massive compact companions such as white…
Binary sdB Stars with Massive Compact Companions
S. Geier, C. Karl, H. Edelmann +2
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…
Rotational properties of single and wide binary subdwarf B stars
S. Geier, U. Heber, H. Edelmann +2
We measured projected rotational velocities of more than a hundred apparently single sdBs. A comparison is made with sdB stars in binary systems with orbits so wide, that tidal int…
Early type stars at high galactic latitudes II. Four evolved B-type stars of unusual chemical composition
M. Ramspeck, U. Heber, H. Edelmann
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…
Spectroscopic Analysis of subluminous B Stars in Binaries with compact Companions
S. Geier, C. Karl, H. Edelmann +2
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…
Two candidate brown dwarf companions around core helium-burning stars
V. Schaffenroth, L. Classen, K. Nagel +4
Hot subdwarf stars of spectral type B (sdBs) are evolved, core helium-burning objects. The formation of those objects is puzzling, because the progenitor star has to lose almost it…
KBS 13 -- a Rare Reflection Effect sdB Binary with an M Dwarf Secondary
B. -Q. For, H. Edelmann, E. M. Green +3
We report preliminary VRI differential photometric and spectroscopic results for KBS 13, a recently discovered non-eclipsing sdB+dM system. Radial velocity measurements indicate an…
Discovery of A New Class of Pulsating Stars: Gravity-mode Pulsators among Subdwarf B Stars
E. M. Green, G. Fontaine, M. D. Reed +15
During the course of an ongoing CCD monitoring program to investigate low-level light variations in subdwarf B (sdB) stars, we have serendipitously discovered a new class of low am…
NLTE analyses of sdB stars: progress and prospects
N. Przybilla, M. F. Nieva, H. Edelmann
We report on preliminary results of a hybrid non-LTE analysis of high-resolution, high-S/N spectra of the helium-rich subdwarf B star Feige49 and the helium-poor sdB HD205805. Non-…
The subdwarf B star SB 290 - A fast rotator on the extreme horizontal branch
S. Geier, U. Heber, C. Heuser +3
Hot subdwarf B stars (sdBs) are evolved core helium-burning stars with very thin hydrogen envelopes. In order to form an sdB, the progenitor has to lose almost all of its hydrogen…
Tidal synchronization of the subdwarf B binary PG 0101+039
S. Geier, S. Nesslinger, U. Heber +3
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…
Spectroscopic Analysis of Subluminous B Stars in Binaries - Four Candidate Systems with Neutron Star/Black Hole Companions Discovered
S. Geier, C. Karl, H. Edelmann +2
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…
Discovery of a close substellar companion to the hot subdwarf star HD 149382 - The decisive influence of substellar objects on late stellar evolution
S. Geier, H. Edelmann, U. Heber +1
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 t…
Hot subdwarf stars in close-up view I. Rotational properties of subdwarf B stars in close binary systems and nature of their unseen companions
S. Geier, U. Heber, Ph. Podsiadlowski +4
The origin of hot subdwarf B stars (sdBs) is still unclear. About half of the known sdBs are in close binary systems for which common envelope ejection is the most likely formation…
Low-mass stellar and substellar companions to sdB stars
S. Geier, L. Classen, P. Bruenner +9
It has been suggested that besides stellar companions, substellar objects in close orbits may be able to trigger mass loss in a common envelope phase and form hot subdwarfs. In an…
LMC origin of the hyper-velocity star HE 0437-5439. Beyond the supermassive black hole paradigm
N. Przybilla, M. F. Nieva, U. Heber +4
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…
Studying the populations of our Galaxy using the kinematics of sdB stars
M. Altmann, H. Edelmann, K. S. de Boer
We have analysed the kinematics of a sample of 114 hot subdwarf stars, for 2/3 of which we present new proper motions, spectroscopic and photometric data. The vast majority of the…
High resolution spectroscopy of bright subdwarf B stars - I. Radial velocity variables
H. Edelmann, U. Heber, M. Altmann +2
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. I…