@article{KamannHusserDreizleretal.2017, author = {Kamann, Sebastian and Husser, T. -O. and Dreizler, S. and Emsellem, E. and Weilbacher, Peter Michael and Martens, S. and Bacon, R. and den Brok, M. and Giesers, B. and Krajnovic, Davor and Roth, Martin M. and Wendt, Martin and Wisotzki, Lutz}, title = {A stellar census in globular clusters with MUSE}, series = {Monthly notices of the Royal Astronomical Society}, volume = {473}, journal = {Monthly notices of the Royal Astronomical Society}, number = {4}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stx2719}, pages = {5591 -- 5616}, year = {2017}, abstract = {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.}, language = {en} } @article{CamposPelisoliKamannetal.2018, author = {Campos, Fabiola and Pelisoli, Ingrid Domingos and Kamann, Sebastian and Husser, T. -O. and Dreizler, S. and Bellini, A. and Robinson, E. L. and Nardiello, Domenico and Piotto, G. and Kepler, S. O. and Istrate, A. G. and Winget, D. E. and Montgomery, M. H. and Dotter, A.}, title = {Outliers}, series = {Monthly notices of the Royal Astronomical Society}, volume = {481}, journal = {Monthly notices of the Royal Astronomical Society}, number = {4}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/sty2591}, pages = {4397 -- 4409}, year = {2018}, abstract = {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.}, language = {en} } @article{SchaffenrothBarlowGeieretal.2019, author = {Schaffenroth, Veronika and Barlow, Brad N. and Geier, Stephan Alfred and Vuckovic, Maja and Kilkenny, D. and Wolz, M. and Kupfer, Thomas and Heber, Ulrich and Drechsel, H. and Kimeswenger, S. and Marsh, T. and Wolf, M. and Pelisoli, Ingrid Domingos and Freudenthal, Joseph and Dreizler, S. and Kreuzer, S. and Ziegerer, E.}, title = {The EREBOS project: Investigating the effect of substellar and low-mass stellar companions on late stellar evolution Survey, target selection, and atmospheric parameters}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {630}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201936019}, pages = {29}, year = {2019}, abstract = {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.}, language = {en} } @article{KamannHusserBrinchmannetal.2016, author = {Kamann, S. and Husser, T. -O. and Brinchmann, Jarle and Emsellem, E. and Weilbacher, Peter Michael and Wisotzki, Lutz and Wendt, Martin and Krajnovic, D. and Roth, M. M. and Bacon, Roland and Dreizler, S.}, title = {MUSE crowded field 3D spectroscopy of over 12 000 stars in the globular cluster NGC 6397}, series = {Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth}, volume = {588}, journal = {Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201527065}, pages = {12}, year = {2016}, abstract = {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.}, language = {en} } @article{WernerDreizlerHeberetal.1995, author = {Werner, Klaus and Dreizler, S. and Heber, Ulrich and Rauch, Thomas}, title = {Triple-alpha burning products on the surface of peculiar post-AGB stars}, year = {1995}, language = {en} } @article{WernerDreizlerHeberetal.1995, author = {Werner, Klaus and Dreizler, S. and Heber, Ulrich and Rauch, Thomas}, title = {Confining the edges of the GW Vir instability strip}, year = {1995}, language = {en} } @article{WernerDreizlerHeberetal.1995, author = {Werner, Klaus and Dreizler, S. and Heber, Ulrich and Rauch, Thomas and Wisotzki, Lutz and Hagen, H.-J.}, title = {Discovery of two hot DO white dwarfs exhibiting ultrahigh-excitation absorption lines}, year = {1995}, language = {en} } @article{WernerRauchDreizleretal.1995, author = {Werner, Klaus and Rauch, Thomas and Dreizler, S. and Heber, Ulrich}, title = {Confining the edges of the GW Vir Instability Strip}, year = {1995}, language = {en} } @article{WernerDreizlerWolff1995, author = {Werner, Klaus and Dreizler, S. and Wolff, B.}, title = {Spectral analysis of the hot DO white dwarf PG 1034+001}, year = {1995}, language = {en} } @article{WernerDreizlerPakulletal.1996, author = {Werner, Klaus and Dreizler, S. and Pakull, M. W. and Cowley, A. P. and Schmidtke, P. C. and Hutchings, J. B. and Crampton, D.}, title = {Non-LTE model atmosphere analysis of the supersoft X-ray source RX J0122.9-7521}, year = {1996}, language = {en} } @article{WernerDreizlerHeberetal.1996, author = {Werner, Klaus and Dreizler, S. and Heber, Ulrich and Rauch, Thomas}, title = {PG 1159 stars}, year = {1996}, language = {en} } @article{WernerDreizlerHeberetal.1996, author = {Werner, Klaus and Dreizler, S. and Heber, Ulrich and Rauch, Thomas and Fleming, T. A. and Sion, E. M. and Vauclair, G.}, title = {High resolution spectroscopy of two hot (pre-) white dwarfs with the Hubble space telescope : KPD 0005+5106 and RXJ 2117+3412}, year = {1996}, language = {en} } @article{DreizlerWernerRauchetal.1997, author = {Dreizler, S. and Werner, Klaus and Rauch, Thomas and Koesterke, Lars and Heber, Ulrich}, title = {NLTE Analyses of PG 1159 stars : Contraints for the structure and evolutiuon of Post-AGB stars}, year = {1997}, language = {en} } @article{KoesterkeDreizlerRauch1998, author = {Koesterke, Lars and Dreizler, S. and Rauch, Thomas}, title = {On the mass-loss of PG 1159 stars}, year = {1998}, language = {en} } @article{WernerDreizlerRauchetal.1999, author = {Werner, Klaus and Dreizler, S. and Rauch, Thomas and Koesterke, Lars and Heber, Ulrich}, title = {Born-again AGB stars : staring point of the H-deficient post-AGB evolutionary sequence?}, year = {1999}, language = {en} } @article{WernerDreizlerRauchetal.1999, author = {Werner, Klaus and Dreizler, S. and Rauch, Thomas and Barnstedt, J{\"u}rgen and G{\"o}z, M. and Gringel, W. and Kappelmann, N. and Kr{\"a}mer, G. and Widmann, H. and Koesterke, Lars and Haas, S. and Heber, Ulrich and Appenzeller, Immo}, title = {FUV spectroscpy of DO an PG 1159 stars with ORFEUS}, year = {1999}, language = {en} }