bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Dwarf project: Eclipsing binaries – precise clocks to discover exoplanets
Authors: Pribulla T. , Vaňko M. , Ammler‐von Eiff M. , Andreev M. , Aslantürk A. , Awadalla N. , Baluďansky D. , Bonanno A. , Božić H. , Catanzaro G. , Çelik L. , Christopoulou P.E. , Covino E. , Cusano F. , Dimitrov D. , Dubovský P. , Eigmueller P. , Esmer E.M. , Frasca A. , Hambálek Ľ. , Hanna M. , Hanslmeier A. , Kalomeni B. , Kjurkchieva D.P. , Krushevska V. , Kudzej I. , Kundra E. , Kuznyetsova Yu. , Lee J.W. , Leitzinger M. , Maciejewski G. , Moldovan D. , Morais M.H.M. , Mugrauer M. , Neuhäuser R. , Niedzielski A. , Odert P. , Ohlert J. , Özavcı İ. , Papageorgiou A. , Parimucha Š. , Poddaný S. , Pop A. , Raetz M. , Raetz S. , Romanyuk Ya. , Ruždjak D. , Schulz J. , Şenavcı H.V. , Srdoc G. , Szalai T. , Székely P. , Sudar D. , Tezcan C.T. , Törün M.E. , Turcu V. , Vince O. , Zejda M. 
Published: October 2014

AbstractWe present a new observational campaign, Dwarf, aimed at detection of circumbinary extrasolar planets using the timing of the minima of low‐mass eclipsing binaries. The observations will be performed within an extensive network of relatively small to medium‐size telescopes with apertures of ∼20‐200 cm. The starting sample of the objects to be monitored contains (i) low‐mass eclipsing binaries with M and K components, (ii) short‐period binaries with a sdB or sdO component, and (iii) post‐common‐envelope systems containing a WD, which enable to determine minima with high precision. Since the amplitude of the timing signal increases with the orbital period of an invisible third component, the timescale of the project is long, at least 5‐10 years. The paper gives simple formulas to estimate the suitability of individual eclipsing binaries for the circumbinary planet detection. Intrinsic variability of the binaries (photospheric spots, flares, pulsation etc.) limiting the accuracy of the minima timing is also discussed. The manuscript also describes the best observing strategy and methods to detect cyclic timing variability in the minima times indicating the presence of circumbinary planets. First test observations of the selected targets are presented (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gregor@night: The future high‐resolution stellar spectrograph for the GREGOR solar telescope
Authors: Strassmeier K.G. , Ilyin I.V. , Woche M. , Granzer T. , Weber M. , Weingrill J. , Bauer S.‐M. , Popow E. , Denker C. , Schmidt W. , von der Lühe O. , Berdyugina S. , Collados M. , Koubsky P. , Hackman T. , Mantere M.J. 
Published: October 2014

AbstractWe describe the future night‐time spectrograph for the GREGOR solar telescope and present its science core projects. The spectrograph provides a 3‐pixel resolution of up to R = 87 000 in 45 échelle orders covering the wavelength range 390‐900 nm with three grating settings. An iodine cell can be used for high‐precision radial velocity work in the 500‐630 nm range. The operation of the spectrograph and the telescope will be fully automated without the presence of humans during night‐time and will be based on the successful STELLA control system. Future upgrades include a second optical camera for even higher spectral resolution, a Stokes‐V polarimeter and a link to the laser‐frequency comb at the Vacuum Tower Telescope. The night‐time core projects are a study of the angular‐momentum evolution of “The Sun in Time” and a continuation of our long‐term Doppler imaging of active stars (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A retrospective of the GREGOR solar telescope in scientific literature
Authors: Denker C. , von der Lühe O. , Feller A. , Arlt K. , Balthasar H. , Bauer S.‐M. , Bello González N. , Berkefeld Th. , Caligari P. , Collados M. , Fischer A. , Granzer T. , Hahn T. , Halbgewachs C. , Heidecke F. , Hofmann A. , Kentischer T. , Klvaňa M. , Kneer F. , Lagg A. , Nicklas H. , Popow E. , Puschmann K.G. , Rendtel J. , Schmidt D. , Schmidt W. , Sobotka M. , Solanki S.K. , Soltau D. , Staude J. , Strassmeier K.G. , Volkmer R. , Waldmann T. , Wiehr E. , Wittmann A.D. , Woche M. 
Published: October 2014

AbstractIn this review, we look back upon the literature, which had the GREGOR solar telescope project as its subject including science cases, telescope subsystems, and post‐focus instruments. The articles date back to the year 2000, when the initial concepts for a new solar telescope on Tenerife were first presented at scientific meetings. This comprehensive bibliography contains literature until the year 2012, i.e., the final stages of commissioning and science verification. Taking stock of the various publications in peer‐reviewed journals and conference proceedings also provides the “historical” context for the reference articles in this special issue of Astronomische Nachrichten/Astronomical Notes (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preparing the GREGOR solar telescope for night‐time use: Deriving a pointing model
Authors: Granzer T. , Halbgewachs C. , Volkmer R. , Soltau D. 
Published: October 2014

AbstractWe report on the results of a dedicated campaign to derive a pointing model for the GREGOR solar telescope which took place in December 2011. Two main goals were in the focus of this campaign: first to prove the aptness of the GREGOR solar telescope for night‐time, unattended operations and second to derive some qualitative measure of the amount of misalignment in the optical and mechanical parts of the telescope. In the final version, a root‐mean‐square deviation (RMSD) of 1.6″ for the azimuth model and an RMSD of 2.3″ in the elevation model could be achieved (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The GREGOR telescope control system
Authors: Halbgewachs C. , Caligari P. , Glogowski K. , Heidecke F. , Knobloch M. , Mustedanagic M. , Volkmer R. , Waldmann T.A. 
Published: October 2014

AbstractThis article describes the architecture of the new GREGOR telescope and its instrument control system. A short summary is given on the communication structure between instruments and other devices during observation. Because of its importance to all instruments the main functions of the telescope control system are described in detail (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The GREGOR Broad‐Band Imager
Authors: von der Lühe O. , Volkmer R. , Kentischer T.J. , Geißler R. 
Published: October 2014

AbstractThe design and characteristics of the Broad‐Band Imager (BBI) of GREGOR are described. BBI covers the visible spectral range with two cameras simultaneously for a large field and with critical sampling at 390 nm, and it includes a mode for observing the pupil in a Foucault configuration. Samples of first‐light observations are shown (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GRIS: The GREGOR Infrared Spectrograph
Authors: Collados M. , López R. , Páez E. , Hernández E. , Reyes M. , Calcines A. , Ballesteros E. , Díaz J.J. , Denker C. , Lagg A. , Schlichenmaier R. , Schmidt W. , Solanki S.K. , Strassmeier K.G. , von der Lühe O. , Volkmer R. 
Published: October 2014

AbstractThis paper describes the main characteristics of GRIS (GREGOR Infrared Spectrograph), the grating spectrograph installed in the recently inaugurated (May 2012) 1.5‐meter GREGOR telescope located at the Observatorio del Teide in Tenerife. The spectrograph has a standard Czerny‐Turner configuration with parabolic collimator and camera mirrors that belong to the same conic surface. Although nothing prevents its use at visible wavelengths, the spectrograph will be initially used in combination with the infrared detector of the Tenerife Infrared Polarimeter (TIP‐II) in standard spectroscopic mode as well as for spectropolarimetric measurements (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The GREGOR adaptive optics system
Authors: Berkefeld Th. , Schmidt D. , Soltau D. , von der Lühe O. , Heidecke F. 
Published: October 2014

AbstractThe new 1.5‐m German solar telescope GREGOR at the Observatorio del Teide, Tenerife, is equipped with an integrated adaptive optics system. Although partly still in the commissioning phase, the system is already being used used for most science observations. It is designed to provide diffraction‐limited observations in the visible‐light regime for seeing better than 1.2″. We describe the AO system including the optical design, software, wavefront reconstruction, and performance (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanical design of the solar telescope GREGOR
Authors: Volkmer R. , Eisenträger P. , Emde P. , Fischer A. , von der Lühe O. , Nicklas H. , Soltau D. , Schmidt W. , Weis U. 
Published: October 2014

AbstractThe mechanical structure of the GREGOR telescope was installed at the Observatorio del Teide, Tenerife, in 2004. New concepts for mounting and cooling of the 1.5‐meter primary mirror were introduced. GREGOR is an open telescope, therefore the dome is completely open during observations to allow for air flushing through the open, but stiff telescope structure. Backside cooling system of the primary mirror keeps the mirror surface close to ambient temperature to prevent mirror seeing. The large collecting area of the primary mirror results in high energy density at the field stop at the prime focus of the primary which needs to be removed. The optical elements are supported by precision alignment systems and should provide a stable solar image at the optical lab. The coudé train can be evacuated and serves as a natural barrier between the outer environmental conditions and the air‐conditioned optical laboratory with its sensitive scientific instrumentation. The telescope was successfully commissioned and will start its nominal operation during 2013 (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Three‐dimensional magnetohydrodynamic simulations of M‐dwarf chromospheres
Authors: Wedemeyer S. , Ludwig H.‐G. , Steiner O. 
Published: October 2014

AbstractWe present first results from three‐dimensional radiation magnetohydrodynamic simulations of M‐type dwarf stars with CO5BOLD. The local models include the top of the convection zone, the photosphere, and the chromosphere. The results are illustrated for models with an effective temperature of 3240 K and a gravitational acceleration of log g = 4.5, which represent analogues of AD Leo. The models have different initial magnetic field strengths and field topologies. This first generation of models demonstrates that the atmospheres of M dwarfs are highly dynamic and intermittent. Magnetic fields and propagating shock waves produce a complicated fine‐structure, which is clearly visible in synthetic intensity maps in the core of the Ca II K spectral line and also at millimeter wavelengths. The dynamic small‐scale pattern cannot be described by means of one‐dimensional models, which has important implications for the construction of semi‐empirical model atmospheres and thus for the interpretation of observations in general. Detailed three‐dimensional numerical simulations are valuable in this respect. Furthermore, such models facilitate the analysis of small‐scale processes, which cannot be observed on stars but nevertheless might be essential for understanding M‐dwarf atmospheres and their activity. An example are so‐called “magnetic tornadoes”, which have recently been found on the Sun and are presented here in M‐dwarf models for the first time. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fundamental properties of lower main‐sequence stars
Authors: Torres G. 
Published: October 2014

AbstractThe field of exoplanet research has revitalized interest in M dwarfs, which have become favorite targets of Doppler and transit surveys. Accurate measurements of their basic properties such as masses, radii, and effective temperatures have revealed significant disagreements with predictions from stellar evolution theory in the sense that stars are larger and cooler than expected. These anomalies are believed to be due to high levels of activity in these stars. The evidence for the radius discrepancies has grown over the years as more and more determinations have become available; however, fewer of these studies include accurate determinations of the temperatures. The ubiquitous mass‐radius diagrams featured in many new discovery papers are becoming more confusing due to increased scatter, which may be due in part to larger than realized systematic errors affecting many of the published measurements. A discussion of these and other issues is given here from an observer's perspective, along with a summary of theoretical efforts to explain the radius and temperature anomalies. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stellar differential rotation in theory and observation
Authors: Czesla S. , Arlt R. , Bonanno A. , Strassmeier K.G. , Huber K.F. 
Published: October 2014

AbstractStellar differential rotation is intimately related to the stellar magnetic dynamo and, thus, to stellar activity. In recent years, significant progress in the measurement of differential rotation on the basis of Doppler imaging techniques and the availability of space‐based long‐term photometry has been achieved. Similarly, simulations incorporate ever more details of the complexity of convective zones. While some aspects of solar and stellar differential rotation can be explained now, several important questions remain open or controversial. In this splinter session, we discussed the latest observational and theoretical progress in the field of differential rotation. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Results from HOPS: A multiwavelength census of Orion protostars
Authors: Fischer W.J. , Megeath S.T. , Stutz A.M. , Tobin J.J. , Ali B. , Stanke T. , Osorio M. , Furlan E. , the HOPS team  
Published: October 2014

AbstractSurveys with the Spitzer and Herschel space observatories are now enabling the discovery and characterization of large samples of protostars in nearby molecular clouds, providing the observational basis for a detailed understanding of star formation in diverse environments. We are pursuing this goal with the Herschel Orion Protostar Survey (HOPS), which targets 328 Spitzer ‐identified protostars in the Orion molecular clouds, the largest star‐forming region in the nearest 500 pc. The sample encompasses all phases of protostellar evolution and a wide range of formation environments, from dense clusters to relative isolation. With a grid of radiative transfer models, we fit the 1–870 µm spectral energy distributions (SEDs) of the protostars to estimate their envelope densities, cavity opening angles, inclinations, and total luminosities. After correcting the bolometric luminosities and temperatures of the sources for foreground extinction and inclination, we find a spread of several orders of magnitude in luminosity at all evolutionary states, a constant median luminosity over the more evolved stages, and a possible deficit of high‐inclination, rapidly infalling envelopes among the Spitzer ‐identified sample. We have detected over 100 new sources in the Herschel images; some of them may fill this deficit. We also report results from modeling the pre‐ and post‐outburst 1–870 µm SEDs of V2775 Ori (HOPS 223), a known FU Orionis outburster in the sample. It is the least luminous FU Ori star with a protostellar envelope. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The stellar activity‐rotation relationship
Authors: Wright N.J. , Drake J.J. , Mamajek E.E. , Henry G.W. 
Published: October 2014

AbstractUsing a new catalog of 824 solar and late‐type stars with measured X‐ray luminosities and rotation periods we have studied the relationship between rotation and stellar activity that is believed to be a probe of the underlying stellar dynamo. Using an unbiased subset of the sample we calculate the power law slope of the unsaturated regime of the activity‐rotation relationship as LX/Lbol α Roβ, where β = –2.70 ± 0.13. Notably this is inconsistent with the canonical β = –2 slope to a confidence of 5σ are argues for an interface‐type dynamo. Super‐saturation is observed for the fastest rotators in our sample and its parametric dependencies are explored. Significant correlations are found with both the corotation radius and the excess polar updraft, the latter theory being preferred as it is supported by other observations. We also present a new X‐ray population synthesis model of the mature stellar component of our Galaxy and use it to reproduce deep observations of a high Galactic latitude field. The model, XStar, can be used to test models of stellar spin‐down and dynamo decay, as well as for estimating stellar X‐ray contamination rates for non‐stellar studies. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Clouds in brown dwarfs and giant planets
Authors: Metchev S. , Apai D. , Radigan J. , Artigau É. , Heinze A. , Helling C. , Homeier D. , Littlefair S. , Morley C. , Skemer A. , Stark C. 
Published: October 2014

AbstractA growing body of observational and theoretical evidence points toward the importance of clouds in the atmospheres of ultra‐cool brown dwarfs and giant planets. Empirically, the presence of clouds is inferred from the red, likely dusty atmospheres of young substellar objects, and from detections of periodic variability in a fraction of brown dwarfs – as expected from rotation and a patchy cloud cover. Theoretical models have progressed alongside by including ever more comprehensive atomic and molecular opacity tables, incorporating the treatment of non‐equilibrium chemistry and clouds through vertical mixing and grain size/sedimentation parameters, and employing 3‐D hydrodynamical simulations. In this proceeding we summarize the key issues raised during the first gathering of observers and theorists to discuss clouds and atmospheric circulation in non‐irradiated ultra‐cool dwarfs and giant planets. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The CoRoT ground‐based asteroseismological programme
Authors: Rainer M. , Poretti E. , Mathias P. , Aerts C. , Amado P.J. , Uytterhoeven K. , the CoRoT SWG Ground‐based Observations Working Group  
Published: October 2014

AbstractA large ground‐based spectroscopic and photometric programme has accompanied the asteroseismological photometric observations of the satellite CoRoT since its launch. These simultaneously complementary observations allow to better characterize the targets, identify the modes and recover many other interesting physical information. In this paper, the spectroscopic ground‐based programme is described, particularly with regards of the HARPS data, and some scientific cases are presented (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the feasibility of employing solar‐like oscillators as detectors for the stochastic background of gravitational waves
Authors: Siegel D.M. , Roth M. 
Published: October 2014

AbstractWe present a hydrodynamic model that describes excitation of linear stellar oscillations by a stochastic background of gravitational waves (SBGW) of astro‐physical and cosmological origin. We find that this excitation mechanism is capable of generating solar g‐mode amplitudes close to or comparable with values expected from excitation by turbulent convection, which is considered to be the main driving force for solar‐like oscillations. A method is presented that places direct upper bounds on the SBGW in a frequency range, in which the SBGW is expected to contain rich astro‐physical information. Employing estimates for solar g‐mode amplitudes, the proposed method is demonstrated to have the potential to compete with sensitivities reached by gravitational wave experiments in other frequency ranges (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The noise wars in helio‐ and asteroseismology
Authors: García R. 
Published: October 2014

AbstractDuring this conference, latest results on helioseismology (both local and global) as well as in asteroseismology have been reviewed, the hottest questions discussed and the future prospects of our field fully debated. A conference so rich in the variety of topics addressed is impossible to be deeply reviewed in a paper. Therefore, I present here my particular view of the field as it is today, concentrating on the solar‐like stars and global helioseismology. The link I found to do so is the constant battle in which we are all engaged against the sources of noise that difficult our studies. The noise in the data, the noise in the inversions, the precision and accuracy of our inferred models, … (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Attempts to reproduce the rotation profile of the red giant KIC 7341231 observed by Kepler
Authors: Ceillier T. , Eggenberger P. , García R.A. , Mathis S. 
Published: October 2014

AbstractThanks to the asteroseimic study of the red giant star KIC 7341231 observed by Kepler, it has been possible to infer its radial differential rotation profile (Deheuvels et al. 2012). This opens new ways to constrain the physical mechanisms responsible of the angular momentum transport in stellar interiors by directly comparing this radial rotation profile with the ones computed using stellar evolution codes including dynamical processes. In this preliminary work, we computed different models of KIC 7341231 with the Geneva stellar evolution code that includes transport mechanisms due to a shellular rotation and the associated large‐scale meridional circulation and shear‐induced turbulence. Once the global parameters of the star had been established, we modified some of the model’s input parameters in order to understand their effects on the predicted rotation profile of the modeled star. As a result, we find a discrepancy between the rotation profile deduced from asteroseismic measurements and the profiles predicted from models including shellular rotation and related meridional flows and turbulence. This indicates that a most powerful mechanism is in action to extract angular momentum from the core of this star (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Seismology of active stars
Authors: Hekker S. , García R.A. 
Published: October 2014

AbstractIn this review we will discuss the current standing and open questions of seismology in active stars. With the longer photometric time series data that are, and will become, available from space‐missions such as Kepler we foresee significant progress in our understanding of stellar internal structures and processes, including interactions between them, taking place in active stars in the next few years (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Acoustic and buoyancy modes throughout stellar evolution: Seismic properties of stars at different stellar ages and masses
Authors: Schuh S. 
Published: October 2014

AbstractParameter regions in which stars can become pulsationally unstable are found throughout the Hertzsprung‐Russell diagram. Stars of high, intermediate, low, and very low masses may cross various instability regions along their paths of evolutionary sequences. In describing them, I give special consideration to hybrid pulsational characteristics that are particularly valuable for asteroseismic investigations, to $ \dot P $ measurements that allow us to directly follow the stellar evolutionary changes in some stars, and to new research results that stand out with respect to previous consensus (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)