bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preliminary results on γ Dor and δ Sct‐γ Dor hybrids in the CoRoT exo‐field of LRa01
Authors: Hareter M. 
Published: October 2014

AbstractThe 131 days long, high‐precision light curves observed in the CoRoT exo‐field during LRa01 were investigated for γ Dor and δ Sct‐γ Dor hybrid stars. In total 418 γ Dor and 274 δ Sct‐γ Dor hybrid candidates were identified. For a fraction of these candidates spectra are available obtained at the Anglo‐Australian Observatory. Effective temperatures and surface gravity were derived by fitting synthetic spectra of three Balmer lines, i.e. Hα, Hβ, and Hγ, as well as of the Ca K line at 3933 °A. The bona fide γ Dor and hybrid stars were plotted in an Teff‐ log g diagram that shows the expected concentration of γ Dor stars at the cool border of the δ Sct strip. In contrast, the hybrids fill the whole δ Sct instability strip without a noticeable concentration. Remarkably, the fraction of constant stars, with no signal above 3 times the noise level, is smallest in the same temperature regime (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectroscopic frequencies of 4 CVn in 2010 and 2011
Authors: Schmid V.S. , Themessl N. , Breger M. , Aerts C. , Beck P.G. , Castanheira B.G. , Fritz V. , Papics P.I. , Debosscher J. , Falcon R.E. 
Published: October 2014

AbstractNumerous high‐resolution spectra of the δ Scuti star 4 CVn were gathered at McDonald Observatory in Texas, USA. They were prepared for interpretation using standard IRAF routines for a subsequent frequency analysis and mode identification with the software FAMIAS. After the reduction process a clear trend in the first moment of the line profile (radial velocity) remained, indicating the signature of binary motion. This was corrected for by fitting a Keplerian orbit, followed by a detailed analysis of the data in the reference frame of the primary. The results of the frequency analysis are in good agreement with previous photometric studies. This paper presents thirteen pulsation modes that were detected in the data sets for the years 2010 and/or 2011. Future work involves spectroscopic mode identification and subsequent seismic modeling (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Do we see the simultaneous occurrence of stellar rotational effects and short‐period pulsations in some A‐type Kepler stars?
Authors: Lampens P. , Tkachenko A. , Lehmann H. , Debosscher J. , Aerts C. , Beck P.G. , Bloemen S. , Kochiashvili N. , Derekas A. 
Published: October 2014

AbstractWe used high‐quality Kepler photometry and recent spectroscopic data to investigate the Kepler target KIC 005988140 considering three possible scenario’s: (1) binarity, (2) co‐existence of δ Scuti‐ and γ Doradus‐type oscillations, and (3) rotational modulation with spots over the stellar surface. Using spectrum synthesis, we derived improved atmospheric parameters from high‐resolution, high signal‐to‐noise spectra. The star is of spectral type A7.5 IV–III with a metallicity slightly lower than that of the Sun. The Fourier analyses of both the photometric and the spectroscopic data reveal two dominant frequencies – with an integer ratio equal to two – in the low frequency regime. Nine more frequencies located in the typical δ Scuti range were also detected. The mean light and radial velocity curves which are not exactly in antiphase, show a similar double‐wave shape. We therefore suggest on a preliminary basis that the physical cause of the observed light and radial velocity variations is the simultaneous occurrence of (δ Sct‐type) pressure modes and stellar rotation coupled to inhomogeneities on the surface of this late A‐type star (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The current state‐of‐the‐art in active region seismology
Authors: Moradi H. 
Published: October 2014

AbstractHelioseismology is the study of the variations in the internal structure and properties of the dynamics of the Sun from measurements of its surface oscillations. With the 2010 launch of the Solar Dynamics Observatory (SDO) we are undoubtedly approaching a new dawn for local helioseismology, as the extent and quality of raw surface oscillation data has never been better. However, advances in theory and modelling are still required to fully utilise these data, especially in magnetic active regions and sunspots, where the physics is poorly understood (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Kepler Fourier concepts: The performance of the Kepler data pipeline
Authors: Murphy S.J. 
Published: October 2014

AbstractGiven the extreme precision attainable with the Kepler Space Telescope, the mitigation of instrumental artefacts is very important. In an earlier paper (Murphy 2012), the characteristics of Kepler data were discussed in light of their effect on asteroseismology. We continue this discussion now that data processed with the new PDC‐MAP pipeline are publicly available; users should use the latest data reductions available at the Mikulski Archive for Space Telescopes (MAST), not just for PDC, but also for improvements in the attached meta‐data. We discuss the injection of noise in the frequency range 0–24 d−1 (up to ∼277 µHz) by the PDC‐LS pipeline into ∼15% of light‐curves (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The puzzle of combination frequencies found in heat‐driven pulsators
Authors: Pápics P.I. 
Published: October 2014

AbstractSearching for combinations in the frequency spectra of variable stars is a commonly used method within the asteroseismological community, as harmonics and linear combinations of individual frequencies are expected to appear not only by chance, but also as a characteristic signature linked to different physical phenomena, e.g., nonlinear oscillations, binarity, and rotation. Furthermore it is very important to identify independent frequencies for modelling purposes. We show that using high precision data sets delivered by recent space missions, the distinction between combinations having a real physical meaning and spurious combinations which only appear by chance gets more and more difficult. We demonstrate how careful one should be with the interpretation of such combination frequencies by presenting the statistical distributions derived from artificial data sets. Based on comparisons to observations, we find that, despite the high statistical probability of finding combinations in random data sets (having similar properties to the ones of real stars), there is a significant difference in the number of the lowest order combinations between stars with and starts without real combination frequencies. This way, a search for frequency combinations is very useful when interpreted properly, and when results are compared to simulations (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Velocity and abundance precisions for future high‐resolution spectroscopic surveys: A study for 4MOST
Authors: Caffau E. , Koch A. , Sbordone L. , Sartoretti P. , Hansen C.J. , Royer F. , Leclerc N. , Bonifacio P. , Christlieb N. , Ludwig H.‐G. , Grebel E.K. , de Jong R.S. , Chiappini C. , Walcher J. , Mignot S. , Feltzing S. , Cohen M. , Minchev I. , Helmi A. , Piffl T. , Depagne E. , Schnurr O. 
Published: October 2014

AbstractIn preparation for future, large‐scale, multi‐object, high‐resolution spectroscopic surveys of the Galaxy, we present a series of tests of the precision in radial velocity and chemical abundances that any such project can achieve at a 4 m class telescope. We briefly discuss a number of science cases that aim at studying the chemo‐dynamical history of the major Galactic components (bulge, thin and thick disks, and halo) – either as a follow‐up to the Gaia mission or on their own merits. Based on a large grid of synthetic spectra that cover the full range in stellar parameters of typical survey targets, we devise an optimal wavelength range and argue for a moderately high‐resolution spectrograph. As a result, the kinematic precision is not limited by any of these factors, but will practically only suffer from systematic effects, easily reaching uncertainties <1km s–1. Under realistic survey conditions (namely, considering stars brighter than r = 16 mag with reasonable exposure times) we prefer an ideal resolving power of R ∼20 000 on average, for an overall wavelength range (with a common two‐arm spectrograph design) of [395;456.5] nm and [587;673] nm. We show for the first time on a general basis that it is possible to measure chemical abundance ratios to better than 0.1 dex for many species (Fe, Mg, Si, Ca, Ti, Na, Al, V, Cr, Mn, Co, Ni, Y, Ba, Nd, Eu) and to an accuracy of about 0.2 dex for other species such as Zr, La, and Sr. While our feasibility study was explicitly carried out for the 4MOST facility, the results can be readily applied to and used for any other conceptual design study for high‐resolution spectrographs. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Helioseismic analysis of active regions using HMI and AIA data
Authors: Tripathy S.C. , Jain K. , Howe R. , Bogart R.S. , Hill F. 
Published: October 2014

AbstractWe apply the ring‐diagram technique to analyze three active regions located near the central meridian. Using Doppler, continuum intensity, and line depth images from the Helioseismic Magnetic Imager (HMI), we investigate the variation in the high‐degree mode asymmetry, frequencies, and horizontal flows. We find that the sub‐surface zonal and meridional flows do not change significantly with the choice of different observables representing different heights in the solar photosphere, while the mode frequencies differ. We also examine the 2‐d acoustic power distribution using data from HMI and the Atmospheric Imaging Assembly (AIA) 1600 and 1700 Å bands (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New pulsating variable stars in the Stock 14 open cluster and surrounding fields
Authors: Drobek D. 
Published: October 2014

AbstractThis paper presents the preliminary results of a multicolour photometric study of the young open cluster Stock 14 and adjacent ßelds. The reddening, distance and age of the cluster were determined from colour‐colour and colour‐magnitude diagrams by means of isochrone ßtting. Fourier analysis of the acquired time‐series data was performed, which resulted in the discovery of new pulsating variable stars and candidates for such objects (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Properties of extrasolar planets and their host stars: A case study of HAT‐P‐7
Authors: Van Eylen V. , Kjeldsen H. , Christensen‐Dalsgaard J. , Aerts C. 
Published: October 2014

AbstractData from the Kepler satellite (Q0‐Q11) are used to study HAT‐P‐7. The satellite's data are extremely valuable for asteroseismic studies of stars and for observing planetary transits; in this work we do both. An asteroseismic study of the host star improves the accuracy of the stellar parameters derived by Christensen‐Dalsgaard et al. (2010), who followed largely the same procedure but based the analysis on only one month of Kepler data. The stellar information is combined with transit observations, phase variations and occultations to derive planetary parameters. In particular, we confirm the presence of ellipsoidal variations as discovered by Welsh et al. (2010), but revise their magnitude, and we revise the occultation depth (Borucki et al. 2009), which leads to different planetary temperature estimates. All other stellar and planetary parameters are now more accurately determined (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photometric study in the young open cluster NGC 6823
Authors: Zahajkiewicz E. 
Published: October 2014

AbstractThe preliminary results of the variability survey in the Þeld of the very young open cluster NGC 6823 are reported. Several dozen variables were found, including the fourteen already known. The new variable stars comprise eight SPB candidates, a δ Sct star, three eclipsing binaries, and a large sample of stars with mostly irregular light variations. The latter group contains over thirty stars that are likely pre‐main sequence members of the cluster (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stellar model fits and inversions
Authors: Christensen‐Dalsgaard J. 
Published: October 2014

AbstractThe recent asteroseismic data from the CoRoT and Kepler missions have provided an entirely new basis for investigating stellar properties. This has led to a rapid development in techniques for analysing such data, although it is probably fair to say that we are still far from having the tools required for the full use of the potential of the observations. Here I provide a brief overview of some of the issues related to the interpretation of asteroseismic data (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A new orbit for comet C/1858 L1 (Donati)
Authors: Branham R.L. 
Published: October 2014

AbstractA new orbit for comet C/1858 L1 (Donati), based on 1036 observations in α and 971 in σ made between 7 June 1858 and 5 March 1859, is calculated using iteratively reweighted least squares. Residuals were weighted by the Welsch weighting function. The orbit represents a high eccentricity ellipse, e = 0.996265, with large semi‐major axis, a = 154.8612 AU, and long period, P = 1927.22 yr. The residuals are relatively random, a 10.7% chance of being random, but with a slight indication of possible nongravitational forces influencing the motion. The comet will not return until the year 3759, when it will pass 0.8442 AU from the Earth. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hα emission objects in Circinus
Authors: Noroozi S. , Haas M. , Chen Z. , Chini R. 
Published: October 2014

AbstractWe present a new survey for Hα emission objects in the Circinus cloud complex and introduce an efficient photometric method for detecting Hα emission via observations in a narrow‐band filter. The observed flux is compared to a blackbody fit of the continuum. Our search strategy reveals 20 stars with strong Hα emission (EW > 10 Å), eight of them being new detections. All Hα stars display infrared excess corroborating their youth. On the other hand, the region contains a number of infrared excess objects that do not show Hα emission. Our results support the picture that accretion – as witnessed by Hα emission – is a highly variable phenomenon. Therefore, Hα surveys can only trace the temporarily active objects. In contrast, infrared excess is a more robust tracer that reveals most of the population of young stellar objects in a star forming region. Our analysis of the general stellar content of the region yields a reliable distance of 450 pc for the Circinus cloud. Moreover, we find a ratio of total‐to‐selective extinction of RV = 2.8 suggesting that smaller‐than‐normal dust grains may be present. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic fields of accretion disks and outflows in prograde and retrograde black holes
Authors: Gnedin Yu.N. , Piotrovich M.Yu. , Buliga S.D. , Natsvlishvili T.M. 
Published: October 2014

AbstractWe show that for the accretion disk with equipartition between magnetic and radiative pressures, prograde black holes generate outflowing energy in jets more efficiently than retrograde black holes do. Both viscous radiative and irradiative disks provide more efficient outflow jets in the case of a prograde black hole than in the case of a retrograde black hole. Our results confirm the conclusion of Tchekhovskoy & McKinney (2012) that, for the same absolute value of the spin, prograde black holes with geometrically thick accretion disks generate outflows several times more efficiently than retrograde black holes do. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A simple recipe for estimating masses of elliptical galaxies and clusters of galaxies
Authors: Lyskova L. 
Published: October 2014

AbstractWe discuss a simple and robust procedure to evaluate the mass/circular velocity of massive elliptical galaxies and clusters of galaxies. It relies only on the surface density and the projected velocity dispersion profiles of tracer particles and therefore can be applied even in case of poor or noisy observational data. Stars, globular clusters or planetary nebulae can be used as tracers for mass determination of elliptical galaxies. For clusters the galaxies themselves can be used as tracer particles. The key element of the proposed procedure is the selection of a “sweet” radius Rsweet, where the sensitivity to the unknown anisotropy of the tracers' orbits is minimal. At this radius the surface density of tracers declines approximately as I(R) α R–2, thus placing Rsweet not far from the half‐light radius of the tracers Reff. The procedure was tested on a sample of cosmological simulations of individual galaxies and galaxy clusters and then applied to real observational data. Independently the total mass profile was derived from the hydrostatic equilibrium equation for the gaseous atmosphere. Mismatch in mass profiles obtained from optical and X‐ray data is used to estimate the non‐thermal contribution to the gas pressure and/or to constrain the distribution of tracers' orbits. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Clustering algorithms: Sensitivity of mass determination using A 3581
Authors: Wilson S. , Oozeer N. , Loubser S.I. 
Published: October 2014

AbstractIn this paper we discuss various methods for clustering in order to determine estimates of the cluster mass, focusing on the cluster A3581. Using virtual observatory (VO) tools, possible galaxy cluster candidates are selected. Using the Kayes Mixture Model (KMM) algorithm and the Gaussian Mixing Model (GMM), we determine the most likely cluster member candidates. We then compare the results obtained to SIMBADs method of hierarchy. The mass of A 3581 was calculated and checked with literature values. We discuss the sensitivity of the mass determination and show that the GMM provides a very robust method to determine member candidates for cluster A 3581. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AGN feedback in clusters: Shock and sound heating
Authors: Nulsen P.E.J. , McNamara PB.R. 
Published: October 2014

AbstractObservations support the view that feedback, in the form of radio outbursts from active nuclei in central galaxies, prevents catastro‐phic cooling of gas and rapid star formation in many groups and clusters of galaxies. Variations in jet power drive a succession of weak shocks that can heat regions close to the active galactic nuclei (AGN). On larger scales, shocks fade into sound waves. The Braginskii viscosity determines a well‐defined sound damping rate in the weakly magnetised intracluster medium (ICM) that can provide sufficient heating on larger scales. It is argued that weak shocks and sound dissipation are the main means by which radio AGN heat the ICM, in which case, the power spectrum of AGN outbursts plays a central role in AGN feedback. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Solving the cooling flow problem through mechanical AGN feedback
Authors: Gaspari M. , Brighenti F. , Ruszkowski M. 
Published: October 2014

AbstractUnopposed radiative cooling of plasma would lead to the cooling catastro‐phe, a massive inflow of condensing gas, manifest in the core of galaxies, groups and clusters. The last generation X‐ray telescopes, Chandra and XMM, have radically changed our view on baryons, indicating AGN heating as the balancing counterpart of cooling. This work reviews our extensive investigation on self‐regulated heating. We argue that the mechanical feedback, based on massive subrelativistic outflows, is the key to solving the cooling flow problem, i.e. dramatically quenching the cooling rates for several Gyr without destroying the cool‐core structure. Using a modified version of the 3D hydrocode FLASH, we show that bipolar AGN outflows can further reproduce fundamental observed features, such as buoyant bubbles, weak shocks, metals dredgeup, and turbulence. The latter is an essential ingredient to drive nonlinear thermal instabilities, which cause the formation of extended cold gas, a residual of the quenched cooling flow and, later, fuel for the feedback engine. Compared to clusters, groups and galaxies require a gentler mechanical feedback, in order to avoid catastro‐phic overheating. We highlight the essential characteristics for a realistic AGN feedback, with emphasis on observational consistency. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The influence of cooling and feedback on cluster pressure profiles
Authors: Pike S.R. , Kay S.T. , Newton R.D.A. 
Published: October 2014

AbstractIn this paper, a new set of 30 high resolution cosmological simulations of galaxy clusters, run with increasingly realistic physics, are presented and compared to observations of the Sunyaev‐Zel'dovich (SZ) effect. It is found that the best fit to the Y500‐M500 relation is from the model without gas cooling, and that supernova feedback is insufficient to counteract the effect of cooling on the gas pressure. Clearly another more powerful source of feedback is required, suggesting that including the effects of active galactic nuclei (AGN) is vital if we are to replicate the SZ properties of the clusters accurately. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The jet feedback mechanism (JFM): From supernovae to clusters of galaxies
Authors: Soker N. , Akashi M. , Gilkis A. , Hillel S. , Papish O. , Refaelovich M. , Tsebrenko D. 
Published: October 2014

AbstractWe study the similarities of jet‐medium interactions in several quite different astro‐physical systems using 2D and 3D hydrodynamical numerical simulations, and find many similarities. The systems include cooling flow (CF) clusters of galaxies, core collapse supernovae (CCSNe), planetary nebulae (PNe), and common envelope (CE) evolution. The similarities include hot bubbles inflated by jets in a bipolar structure, vortices on the sides of the jets, vortices inside the inflated bubbles, fragmentation of bubbles to two and more bubbles, and buoyancy of bubbles. The activity in many cases is regulated by a negative feedback mechanism. In CF clusters we find that heating of the intra‐cluster medium (ICM) is done by mixing hot shocked jet gas with the ICM, and not by shocks. Our results strengthen the jet feedback mechanism (JFM) as a common process in many astro‐physical objects. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Active and star‐forming galactic nuclei in WINGS: A preliminary report
Authors: Marziani P. , D' Onofrio M. , Bettoni D. , Fasano G. , Fritz J. , Poggianti B.M. , Cava A. 
Published: October 2014

AbstractWe analyzed the spectra collected under the wide‐field nearby galaxy clusters survey (WINGS) to reveal emission lines in cluster galaxies. After removing stellar emission with dedicated population synthesis models we found evidence of faint emission line activity in a sizable number of sources. Diagnostic diagrams were used to define or at least constrain the origin of the emission line activity. Cross‐correlation with radio surveys is also being used for the identification of “true” active nuclei. We report the discovery of a previously unknown Seyfert 1 nucleus, WINGS J230945.81+072431.0, and preliminary results on prevalence and basic properties of the active and star forming galaxies we identified. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)