TY  - JOUR
A1  - Schaffenroth, Veronika
A1  - Barlow, Brad N.
A1  - Geier, Stephan Alfred
A1  - Vuckovic, Maja
A1  - Kilkenny, D.
A1  - Wolz, M.
A1  - Kupfer, Thomas
A1  - Heber, Ulrich
A1  - Drechsel, H.
A1  - Kimeswenger, S.
A1  - Marsh, T.
A1  - Wolf, M.
A1  - Pelisoli, Ingrid Domingos
A1  - Freudenthal, Joseph
A1  - Dreizler, S.
A1  - Kreuzer, S.
A1  - Ziegerer, E.
T1  - The EREBOS project: Investigating the effect of substellar and low-mass stellar companions on late stellar evolution Survey, target selection, and atmospheric parameters
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Eclipsing post-common-envelope binaries are highly important for resolving the poorly understood, very short-lived common-envelope phase of stellar evolution. Most hot subdwarfs (sdO/Bs) are the bare helium-burning cores of red giants that have lost almost all of their hydrogen envelope. This mass loss is often triggered by common-envelope interactions with close stellar or even substellar companions. Cool companions to hot subdwarf stars such as late-type stars and brown dwarfs are detectable from characteristic light-curve variations - reflection effects and often eclipses. In the recently published catalog of eclipsing binaries in the Galactic Bulge and in the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey, we discovered 125 new eclipsing systems showing a reflection effect seen by visual inspection of the light curves and using a machine-learning algorithm, in addition to the 36 systems previously discovered by the Optical Gravitational Lesing Experiment (OGLE) team. The Eclipsing Reflection Effect Binaries from Optical Surveys (EREBOS) project aims at analyzing all newly discovered eclipsing binaries of the HW Vir type (hot subdwarf + close, cool companion) based on a spectroscopic and photometric follow up to derive the mass distribution of the companions, constrain the fraction of substellar companions, and determine the minimum mass needed to strip off the red-giant envelope. To constrain the nature of the primary we derived the absolute magnitude and the reduced proper motion of all our targets with the help of the parallaxes and proper motions measured by the Gaia mission and compared those to the Gaia white-dwarf candidate catalog. It was possible to derive the nature of a subset of our targets, for which observed spectra are available, by measuring the atmospheric parameter of the primary, confirming that less than 10% of our systems are not sdO/Bs with cool companions but are white dwarfs or central stars of planetary nebula. This large sample of eclipsing hot subdwarfs with cool companions allowed us to derive a significant period distribution for hot subdwarfs with cool companions for the first time showing that the period distribution is much broader than previously thought and is ideally suited to finding the lowest-mass companions to hot subdwarf stars. The comparison with related binary populations shows that the period distribution of HW Vir systems is very similar to WD+dM systems and central stars of planetary nebula with cool companions. In the future, several new photometric surveys will be carried out, which will further increase the sample of this project, providing the potential to test many aspects of common-envelope theory and binary evolution.
KW  - binaries: eclipsing
KW  - brown dwarfs
KW  - binaries: spectroscopic
KW  - binaries: close
KW  - subdwarfs
KW  - surveys
Y1  - 2019
U6  - https://doi.org/10.1051/0004-6361/201936019
SN  - 1432-0746
VL  - 630
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Campos, Fabiola
A1  - Pelisoli, Ingrid Domingos
A1  - Kamann, Sebastian
A1  - Husser, T. -O.
A1  - Dreizler, S.
A1  - Bellini, A.
A1  - Robinson, E. L.
A1  - Nardiello, Domenico
A1  - Piotto, G.
A1  - Kepler, S. O.
A1  - Istrate, A. G.
A1  - Winget, D. E.
A1  - Montgomery, M. H.
A1  - Dotter, A.
T1  - Outliers
BT  - multicolour photometry guiding the search for evolved binary systems in the globular cluster 47 Tucanae
JF  - Monthly notices of the Royal Astronomical Society
N2  - We use Hubble Space Telescope multicolour photometry of the globular cluster 47 Tucanae to uncover a population of 24 objects with no previous classification that are outliers from the single-star model tracks in the colour-magnitude diagram and yet are likely cluster members. By comparing those sources with evolutionary models and X-ray source catalogues, we were able to show that the majority of those sources are likely binary systems that do not have any X-ray source detected nearby, most possibly formed by a white dwarf and a main-sequence star and a small number of possible double-degenerate systems.
KW  - binaries: general
KW  - Hertzsprung-Russell and colour-magnitude diagrams
KW  - white dwarfs
KW  - globular clusters: individual: 47 Tuc
Y1  - 2018
U6  - https://doi.org/10.1093/mnras/sty2591
SN  - 0035-8711
SN  - 1365-2966
VL  - 481
IS  - 4
SP  - 4397
EP  - 4409
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Kamann, Sebastian
A1  - Husser, T. -O.
A1  - Dreizler, S.
A1  - Emsellem, E.
A1  - Weilbacher, Peter Michael
A1  - Martens, S.
A1  - Bacon, R.
A1  - den Brok, M.
A1  - Giesers, B.
A1  - Krajnovic, Davor
A1  - Roth, Martin M.
A1  - Wendt, Martin
A1  - Wisotzki, Lutz
T1  - A stellar census in globular clusters with MUSE
BT  - the contribution of rotation to cluster dynamics studied with 200 000 stars
JF  - Monthly notices of the Royal Astronomical Society
N2  - This is the first of a series of papers presenting the results from our survey of 25 Galactic globular clusters with the MUSE integral-field spectrograph. In combination with our dedicated algorithm for source deblending, MUSE provides unique multiplex capabilities in crowded stellar fields and allows us to acquire samples of up to 20 000 stars within the half-light radius of each cluster. The present paper focuses on the analysis of the internal dynamics of 22 out of the 25 clusters, using about 500 000 spectra of 200 000 individual stars. Thanks to the large stellar samples per cluster, we are able to perform a detailed analysis of the central rotation and dispersion fields using both radial profiles and two-dimensional maps. The velocity dispersion profiles we derive show a good general agreement with existing radial velocity studies but typically reach closer to the cluster centres. By comparison with proper motion data, we derive or update the dynamical distance estimates to 14 clusters. Compared to previous dynamical distance estimates for 47 Tuc, our value is in much better agreement with other methods. We further find significant (>3 sigma) rotation in the majority (13/22) of our clusters. Our analysis seems to confirm earlier findings of a link between rotation and the ellipticities of globular clusters. In addition, we find a correlation between the strengths of internal rotation and the relaxation times of the clusters, suggesting that the central rotation fields are relics of the cluster formation that are gradually dissipated via two-body relaxation.
KW  - techniques: imaging spectroscopy
KW  - stars: kinematics and dynamics
KW  - globular clusters: general
Y1  - 2017
U6  - https://doi.org/10.1093/mnras/stx2719
SN  - 0035-8711
SN  - 1365-2966
VL  - 473
IS  - 4
SP  - 5591
EP  - 5616
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Kamann, S.
A1  - Husser, T. -O.
A1  - Brinchmann, Jarle
A1  - Emsellem, E.
A1  - Weilbacher, Peter Michael
A1  - Wisotzki, Lutz
A1  - Wendt, Martin
A1  - Krajnovic, D.
A1  - Roth, M. M.
A1  - Bacon, Roland
A1  - Dreizler, S.
T1  - MUSE crowded field 3D spectroscopy of over 12 000 stars in the globular cluster NGC 6397
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - We present a detailed analysis of the kinematics of the Galactic globular cluster NGC 6397 based on more than similar to 18 000 spectra obtained with the novel integral field spectrograph MUSE. While NGC 6397 is often considered a core collapse cluster, our analysis suggests a flattening of the surface brightness profile at the smallest radii. Although it is among the nearest globular clusters, the low velocity dispersion of NGC 6397 of < 5 km s(-1) imposes heavy demands on the quality of the kinematical data. We show that despite its limited spectral resolution, MUSE reaches an accuracy of 1 km s(-1) in the analysis of stellar spectra. We find slight evidence for a rotational component in the cluster and the velocity dispersion profile that we obtain shows a mild central cusp. To investigate the nature of this feature, we calculate spherical Jeans models and compare these models to our kinematical data. This comparison shows that if a constant mass-to-light ratio is assumed, the addition of an intermediate-mass black hole with a mass of 600 M-circle dot brings the model predictions into agreement with our data, and therefore could be at the origin of the velocity dispersion profile. We further investigate cases with varying mass-to-light ratios and find that a compact dark stellar component can also explain our observations. However, such a component would closely resemble the black hole from the constant mass-to-light ratio models as this component must be confined to the central similar to 5 ' of the cluster and must have a similar mass. Independent constraints on the distribution of stellar remnants in the cluster or kinematic measurements at the highest possible spatial resolution should be able to distinguish the two alternatives.
KW  - globular clusters: individual: NGC 6397
KW  - stars: kinematics and dynamics
KW  - techniques: radial velocities
KW  - techniques: imaging spectroscopy
KW  - black hole physics
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201527065
SN  - 1432-0746
VL  - 588
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Werner, Klaus
A1  - Dreizler, S.
A1  - Rauch, Thomas
A1  - Koesterke, Lars
A1  - Heber, Ulrich
T1  - Born-again AGB stars : staring point of the H-deficient post-AGB evolutionary sequence?
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Werner, Klaus
A1  - Dreizler, S.
A1  - Rauch, Thomas
A1  - Barnstedt, Jürgen
A1  - Göz, M.
A1  - Gringel, W.
A1  - Kappelmann, N.
A1  - Krämer, G.
A1  - Widmann, H.
A1  - Koesterke, Lars
A1  - Haas, S.
A1  - Heber, Ulrich
A1  - Appenzeller, Immo
T1  - FUV spectroscpy of DO an PG 1159 stars with ORFEUS
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Koesterke, Lars
A1  - Dreizler, S.
A1  - Rauch, Thomas
T1  - On the mass-loss of PG 1159 stars
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Dreizler, S.
A1  - Werner, Klaus
A1  - Rauch, Thomas
A1  - Koesterke, Lars
A1  - Heber, Ulrich
T1  - NLTE Analyses of PG 1159 stars : Contraints for the structure and evolutiuon of Post-AGB stars
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Werner, Klaus
A1  - Dreizler, S.
A1  - Pakull, M. W.
A1  - Cowley, A. P.
A1  - Schmidtke, P. C.
A1  - Hutchings, J. B.
A1  - Crampton, D.
T1  - Non-LTE model atmosphere analysis of the supersoft X-ray source RX J0122.9-7521
Y1  - 1996
ER  - 
TY  - JOUR
A1  - Werner, Klaus
A1  - Dreizler, S.
A1  - Heber, Ulrich
A1  - Rauch, Thomas
A1  - Fleming, T. A.
A1  - Sion, E. M.
A1  - Vauclair, G.
T1  - High resolution spectroscopy of two hot (pre-) white dwarfs with the Hubble space telescope : KPD 0005+5106 and RXJ 2117+3412
Y1  - 1996
ER  -