bluuebunny/crossref_metadata_2025_split huggingface dataset:
New series of equilibrium figures based on the Roche model
Authors: Kondratyev B.P. , Trubitsina N.G. 
Published: October 2014

AbstractA sequence of equilibrium figures with the strongest possible mass concentration toward the centre is constructed. The bicubic equation is solved and the explicit equation is derived for the shape of the surface of any equilibrium figure consid‐ered. The new sequence of equilibrium figures is constructed proceeding from the assumption that angular rotation velocity of these figures varies as a function of normalized average density. A relation is derived between the normalized angular velocity $ \tilde \Omega ^2$ and the oblateness ε of the equilibrium figure. Oblateness values of figures lie in the range 0 < ε < 1/3. In the extreme case of the weakest possible potential (the largest ε) the figure has the shape of the limiting Roche lens. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Newly identified YSO candidates towards LDN 1188
Authors: Marton G. , Verebélyi E. , Kiss Cs. , Smidla J. 
Published: October 2014

AbstractWe present an analysis of young stellar object (YSO) candidates towards the LDN 1188 molecular cloud. The YSO candidates were selected from the WISE all‐sky catalogue, based on a statistical method. We found 601 candidates in the region, and classified them as Class I, Flat, and Class II YSOs. Groups were identified and described with the Minimal Spanning Tree (MST) method. Previously identified molecular cores show evidence of ongoing star formation at different stages throughout the cloud complex. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
SPH‐based simulation of multi‐material asteroid collisions
Authors: Maindl T.I. , Schäfer C. , Speith R. , Süli Á. , Forgács‐Dajka E. , Dvorak R. 
Published: October 2014

AbstractWe give a brief introduction to smoothed particle hydrodynamics methods for continuum mechanics. Specifically, we present our 3D SPH code to simulate and analyze collisions of asteroids consisting of two types of material: basaltic rock and ice. We consider effects like brittle failure, fragmentation, and merging in different impact scenarios. After validating our code against previously published results we present first collision results based on measured values for the Weibull flaw distribution parameters of basalt. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Statistical properties of twin kilohertz quasi‐periodic oscillations in neutron star low‐mass X‐ray binaries
Authors: Wang D. H. , Chen L. , Zhang C. M. , Lei Y. J. , Qu J. L. 
Published: October 2014

AbstractWe collect the data of twin kilohertz quasi‐periodic oscillations (kHz QPOs) published before 2012 from 26 neutron star (NS) low‐mass X‐ray binary (LMXB) sources, then we analyze the centroid frequency (ν) distribution of twin kHz QPOs (lower frequency ν1 and upper frequency ν2) both for Atoll and Z sources. For the data without shift‐and‐add, we find that Atoll and Z sources show different distributions of ν1, ν2 and ν2/ν1, but the same distribution of Δν (difference of twin kHz QPOs), which indicates that twin kHz QPOs may share the common properties of LXMBs and have the same physical origins. The distribution of Δν is quite different from a constant value, so is ν 2/ν1 from a constant ratio. The weighted mean values and maxima of ν1 and ν2 in Atoll sources are slightly higher than those in Z sources. We also find that shift‐and‐add technique can reconstruct the distributions of ν1 and Δν. The K‐S test results of ν1 and Δν between Atoll and Z sources from data with shift‐and‐add are quite different from those without it, and we think that this may be caused by the selection biases of the sample. We also study the properties of the quality factor (Q) and the root‐meansquared (rms) amplitude of 4U 0614+09 with data from the two observational methods, but the errors are too big to make a robust conclusion. The NS spin frequency (νs) distribution of 28 NS‐LMXBs show a bigger mean value (∼408 Hz) than that (∼281 Hz) of the radio binary millisecond pulsars (MSPs), which may be due to the lack of the spin detections from Z sources (systematically lower than 281 Hz). Furthermore, on the relations between the kHz QPOs and NS spin frequency νs, we find the approximate correlations of the mean values of Δν with NS spin and its half, respectively. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High resolution study of the abundance pattern of the heavy elements in very metal‐poor field stars
Authors: Spite M. , Spite F. 
Published: October 2014

AbstractThe abundances of heavy elements in EMP stars are not well explained by the simple view of an initial basic “rapid” process. In a careful and homogeneous analysis of the “First Stars” sample (eighty per cent of the stars have a metallicity [Fe/H] ≃ –3.1 ± 0.4), it has been shown that at this metallicity [Eu/Ba] is constant, and therefore the europium‐rich stars (generally called “r‐rich”) are also Ba‐rich. The very large variation of [Ba/Fe] (existence of “r‐poor” and “r‐rich” stars) induces that the early matter was not perfectly mixed. On the other hand, the distribution of the values of [Sr/Ba] vs. [Ba/Fe] appears with well defined upper and lower envelopes. No star was found with [Sr/Ba] < –0.5 and the scatter of [Sr/Ba] increases regularly when [Ba/Fe] decreases. To explain this behavior, we suggest that an early “additional” process forming mainly first peak elements would affect the initial composition of the matter. For a same quantity of accreted matter, this additional Sr production would barely affect the r‐rich matter (which already contains an important quantity of Sr) but would change significantly the composition of the r‐poor matter. The abundances found in the CEMP‐r+s stars reflect the transfer of heavy elements from a defunct AGB companion. But the abundances of the heavy elements in CEMP‐no stars present the same characteristics as the the abundances in the EMP stars. Direct stellar ages may be found from radioactive elements, the precision is limited by the precision in the measurements of abundances from faint lines in faint stars, and the uncertainty in the initial abundances of the radioactive elements. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Deep high spectral resolution spectroscopy and chemical composition of ionized nebulae
Authors: Esteban C. , García‐Rojas J. , Mesa‐Delgado A. , Toribio San Cipriano L. 
Published: October 2014

AbstractHigh spectral resolution spectroscopy has proved to be very useful for the advancement of chemical abundances studies in photoionized nebulae, such as H II regions and planetary nebulae (PNe). Classical analyses make use of the intensity of bright collisionally excited lines (CELs), which have a strong dependence on the electron temperature and density. By using high resolution spectrophotometric data, our group has led the determination of chemical abundances of some heavy element ions, mainly O++, O+, and C++ from faint recombination lines (RLs), allowing us to deblend them from other nearby emission lines or sky features. The importance of these lines is that their emissivity depends weakly on the temperature and density structure of the gas. The unresolved issue in this field is that recombination lines of heavy element ions give abundances that are about 2–3 times higher than those derived from CELs – in H II regions – for the same ion, and can even be a factor of 70 times higher in some PNe. This uncertainty puts into doubt the validity of face values of metallicity that we use as representative not only for ionized nebulae in the Local Universe, but also for star‐forming dwarf and spiral galaxies at different redshifts. Additionally, high‐resolution data can allow us to detect and deblend faint lines of neutron capture element ions in PNe. This information would introduce further restrictions to evolution models of AGBs and would help to quantify the chemical enrichment in s‐elements produced by low and intermediate mass stars. The availability of an échelle spectrograph at the E‐ELT will be of paramount interest to: (a) extend the studies of heavyelement recombination lines to low metallicity objects, (b) to extend abundance determinations of s‐elements to planetary nebulae in the extragalactic domain and to bright Galactic and extragalactic H II regions. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The chemical composition of the Small Magellanic Cloud
Authors: Mucciarelli A. 
Published: October 2014

AbstractThe Small Magellanic Cloud is a close, irregular galaxy that has experienced a complex star formation history due to the strong interactions occurred both with the Large Magellanic Cloud and the Galaxy. Despite its importance, the chemical composition of its stellar populations older than ∼ 1–2 Gyr is still poorly investigated. I present the first results of a spectroscopic survey of ∼ 200 Small Magellanic Cloud giant stars performed with FLAMES@VLT. The derived metallicity distribution peaks at [Fe/H] ∼ –0.9/–1.0 dex, with a secondary peak at [Fe/H] ∼ –0.6 dex. All these stars show [α /Fe] abundance ratios that are solar or mildly enhanced (∼+0.1 dex). Also, three metal‐poor stars (with [Fe/H] ∼ –2.5 dex and enhanced [α /Fe] ratios compatible with those of the Galactic Halo) have been detected in the outskirts of the SMC: These giants are the most metal‐poor stars discovered so far in the Magellanic Clouds. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
HERMES at Mercator, competitive high‐resolution spectroscopy with a small telescope
Authors: Raskin G. , Van Winckel H. 
Published: October 2014

AbstractHERMES, a fibre‐fed high‐resolution (R = 85000) échelle spectrograph with good stability and excellent throughput, is the work‐horse instrument of the 1.2‐m Mercator telescope on La Palma. HERMES targets building up time series of high‐quality data of variable stellar phenomena, mainly for asteroseismology and binary‐evolution research. In this paper we present the HERMES project and discuss the instrument design, performance, and a future upgrade. We also present some results of the first four years of HERMES observations. We illustrate the value of small telescopes, equipped with efficient instrumentation, for high‐resolution spectroscopy. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Isotope spectroscopy
Authors: Caffau E. , Steffen M. , Bonifacio P. , Ludwig H.‐G. , Monaco L. , Lo Curto G. , Kamp I. 
Published: October 2014

AbstractThe measurement of isotopic ratios provides a privileged insight both into nucleosynthesis and into the mechanisms operating in stellar envelopes, such as gravitational settling. In this article, we give a few examples of how isotopic ratios can be determined from high‐resolution, high‐quality stellar spectra. We consider examples of the lightest elements, H and He, for which the isotopic shifts are very large and easily measurable, and examples of heavier elements for which the determination of isotopic ratios is more difficult. The presence of 6Li in the stellar atmospheres causes a subtle extra depression in the red wing of the 7Li 670.7 nm doublet which can only be detected in spectra of the highest quality. But even with the best spectra, the derived 6Li abundance can only be as good as the synthetic spectra used for their interpretation. It is now known that 3D non‐LTE modelling of the lithium spectral line profiles is necessary to account properly for the intrinsic line asymmetry, which is produced by convective flows in the atmospheres of cool stars, and can mimic the presence of 6Li. We also discuss briefly the case of the carbon isotopic ratio in metal‐poor stars, and provide a new determination of the nickel isotopic ratios in the solar atmosphere. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
What do the solar activity indices represent?
Authors: Li K.J. , Kong D.F. , Liang H.F. , Feng W. 
Published: October 2014

AbstractSunspot number, sunspot area, and radio flux at 10.7 cm are the indices which are most frequently used to describe the long‐term solar activity. The data of the daily solar full‐disk magnetograms measured at Mount Wilson Observatory from 19 January 1970 to 31 December 2012 are utilized together with the daily observations of the three indices to probe the relationship of the full‐disk magnetic activity respectively with the indices. Cross correlation analyses of the daily magnetic field measurements at Mount Wilson observatory are taken with the daily observations of the three indices, and the statistical significance of the difference of the obtained correlation coefficients is investigated. The following results are obtained: (1) The sunspot number should be preferred to represent/reflect the full‐disk magnetic activity of the Sun to which the weak magnetic fields (outside of sunspots) mainly contribute, the sunspot area should be recommended to represent the strong magnetic activity of the Sun (in sunspots), and the 10.7 cm radio flux should be preferred to represent the full‐disk magnetic activity of the Sun (both the weak and strong magnetic fields) to which the weak magnetic fields mainly contribute. (2) On the other hand, the most recommendable index that could be used to represent/reflect the weak magnetic activity is the 10.7 cm radio flux, the most recommendable index that could be used to represent the strong magnetic activity is the sunspot area, and the most recommendable index that could be used to represent the full‐disk magnetic activity of the Sun is the 10.7cm radio flux. Additionally, the cycle characteristics of the magnetic field strengths on the solar disk are given. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The association between sunspot magnetic fields and superpenumbral fibrils
Authors: Louis R.E. , Balthasar H. , Kuckein C. , Gömöry P. , Puschmann K.G. , Denker C. 
Published: October 2014

AbstractSpectropolarimetric observations of a sunspot were carried out with the Tenerife Infrared Polarimeter at Observatorio del Teide, Tenerife, Spain. Maps of the physical parameters were obtained from an inversion of the Stokes profiles observed in the infrared Fe I line at 15648 Å The regular sunspot consisted of a light bridge which separated the two umbral cores of the same polarity. One of the arms of the light bridge formed an extension of a penumbral filament which comprised weak and highly inclined magnetic fields. In addition, the Stokes V profiles in this filament had an opposite sign as the sunspot and some resembled Stokes Q or U. This penumbral filament terminated abruptly into another at the edge of the sunspot, where the latter was relatively vertical by about 30°. Chromospheric Hα and He II 304 Å filtergrams revealed three superpenumbral fibrils on the limb‐side of the sunspot, in which one fibril extended into the sunspot and was oriented along the highly inclined penumbral counterpart of the light bridge. An intense, elongated brightening was observed along this fibril that was co‐spatial with the intersecting penumbral filaments in the photosphere. Our results suggest that the disruption in the sunspot magnetic field at the location of the light bridge could be the source of reconnection that led to the intense chromospheric brightening and facilitated the supply of cool material in maintaining the overlying superpenumbral fibrils. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Long‐slit échelle spectroscopy of galactic outflows: The case ofNGC 4449
Authors: Bomans D.J. , Weis K. 
Published: October 2014

AbstractAt high redshift the ubiquity of outflows and winds in strongly star‐forming galaxies has been demonstrated using rest frame UV absorption lines. In the cases with optical emission lines, the studies mostly had to rely on low and intermediate dispersion spectra. This implies that for detailed studies of galactic wind physics we have to use local objects. In particular, dwarf galaxies are well suited to extrapolation to high redshift protogalaxies. Several kinematic studies of strongly starforming dwarf galaxies using Fabry‐Pérot and IFU spectrographs exist. Unfortunately, similar as for high redshift galaxies the employed spectral resolution is often significantly higher that the thermal line width. As a result faint high velocity features and details of the turbulent motion are hidden or unresolved. Here we will present an analysis of the ionized gas kinematics of the prototypical star‐forming irregular galaxy NGC 4449 using long‐slit, high‐dispersion échelle spectra. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modulating magnetar emission by magneto‐elastic oscillations
Authors: Gabler M. , Cerdá‐Durán P. , Font J.A. , Stergioulas N. , Müller E. 
Published: October 2014

AbstractWe present a new numerical tool to calculate the emission of highly magnetized neutron stars (magnetars) and apply it to describe the quasi‐periodic oscillations (QPOs) observed in magnetar giant flares. In previous work we have developed a model of magneto‐elastic oscillations of magnetars that allows to reproduce the observed frequencies. These QPOs can couple to the star's exterior through the magnetic field and induce currents in the magnetosphere that provide scattering targets for resonant cyclotron scattering of the photons. The scattering is calculated with a Monte‐Carlo approach and it is coupled to a code that calculates the momentum distribution of the charge carriers as an one‐dimensional accelerator problem. As a first test of the method we calculate the modulation of the quiescent emission of the neutron star by the magneto‐elastic QPOs for a prescribed momentum distribution of the charge carriers. The necessary amplitudes of the QPOs at the surface of the star to modulate the emission significantly are ≲1km. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The loss‐limited electron energy in SN 1006: Effects of the shock velocity and of the diffusion process
Authors: Miceli M. , Bocchino F. , Decourchelle A. , Vink J. , Broersen S. , Orlando S. 
Published: October 2014

AbstractThe spectral shape of the synchrotron X‐ray emission from SN 1006 reveals the fundamental role played by radiative losses in shaping the high‐energy tail of the electron spectrum. We analyze data from the XMM‐Newton SN 1006 Large Program and confirm that in both nonthermal limbs the loss‐limited model correctly describes the observed spectra. We study the physical origin of the observed variations of the synchrotron cutoff energy across the shell. We investigate the role played by the shock velocity and by the electron gyrofactor. We found that the cutoff energy of the synchrotron X‐ray emission reaches its maximum value in regions where the shock has experienced its highest average speed. This result is consistent with the loss‐limited framework. We also find that the electron acceleration in both nonthermal limbs of SN 1006 proceeds close to the Bohm diffusion limit, the gyrofactor being in the range η ∼ 1.5–4. We finally investigate possible explanations for the low values of cutoff energy measured in thermal limbs. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Intrabinary shock emission from “black widows” and “redbacks”
Authors: Roberts M. S. E. , Mclaughlin M. A. , Gentile P. , Aliu E. , Hessels J. W. T. , Ransom S. M. , Ray P.S. 
Published: October 2014

AbstractEclipsing millisecond pulsars in close (Pb < 1 day) binary systems provide a different view of pulsar winds and shocks than do isolated pulsars. Since 2009, the numbers of these systems known in the Galactic field has increased enormously. We have been systematically studying many of these newly discovered systems at multiple wavelengths. Typically, the companion is nearly Roche‐lobe filling and heated by the pulsar which drives mass loss from the companion. The pulsar wind shocks with this material just above the surface of the companion. We discuss various observational properties of this shock, including radio eclipses, orbitally modulated X‐ray emission, and the potential for γ‐ray emission. Redbacks, whose companions are likely non‐degenerate and significantly more massive, generally have more luminous shocks than black widows which have very low mass companions. This is expected since the more massive redback companions intercept a greater fraction of the pulsar wind. We also compare these systems to accreting millisecond pulsars, which may be progenitors of black widows and in some cases can pass back and forth between redback and accretion phases. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The new period of the intermediate polar V709 Cas
Authors: Hric L. , Breus V. , Katysheva N. A. , Shugarov S. Yu. , Dubovský P. 
Published: October 2014

AbstractWe present the results of 10 years of photometric CCD observations of the intermediate polar V709 Cas obtained by using different instruments during 2003–2013. We detected a new variability with a period of Pnew = 0.d016449979(5) which seems to be real. The spin variability is not clearly seen in all our data, so we are unable to study any evolution of the white dwarf rotation. From the best night (in 2010) we obtained a spin period of Pspin = 311.s8(5). We analyzed the orbital variability using (O – C) analysis. We found no variations of the orbital period on a timescale of 10 years, but the linear fit to the (O – C) diagram shows that the value of the orbital period is Porb = 0.d2222123(6), which is close to the earlier published values. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FLECHAS – A new échelle spectrograph at the University Observatory Jena
Authors: Mugrauer M. , Avila G. , Guirao C. 
Published: October 2014

AbstractThe new échelle spectrograph FLECHAS (Fibre Linked ECHelle Astronomical Spectrograph) is in operation at the Nasmyth‐focus of the 0.9 m telescope of the University Observatory Jena. FLECHAS is equipped with a sensitive back‐illuminated and midband coated CCD‐detector, as well as with a calibration unit for flatfield and wavelength‐calibration. The spectrograph covers the spectral range between about 3900 and 8100 Å and exhibits a resolving power of R ∼ 9300. In this article all technical characteristics of FLECHAS are described and examples of the first astronomical observations obtained with the new instrument in July 2013 at the University Observatory Jena are presented, among them the first light spectra taken with FLECHAS, simultaneous imaging and spectroscopic observations, the determination of the detection limit of the instrument, the spectroscopy of stars of different spectral types and of faint extended objects, as well as the Li‐line detection in the spectra of young solar‐like stars. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The highest energy neutrinos: First evidence for cosmic origin
Authors: Halzen F. 
Published: October 2014

AbstractDevelopments in neutrino astronomy have been to a great extent motivated by the search for the sources of the cosmic rays, leading at a very early stage to the concept of a cubic kilometer neutrino detector. Almost four decades later such an instrument, IceCube, is taking data and has produced the first evidence for a flux of high‐energy neutrinos of cosmic origin. After a brief review of the history of the field, we will introduce IceCube and describe the first analysis of data taken with the completed instrument. The atmospheric neutrino flux cannot accommodate an excess of 28 neutrinos observed with energies above 60 TeV. We will briefly speculate on the origin of these events. Readers interested specifically in IceCube results may refer directly to Sect. 3. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)