bluuebunny/crossref_metadata_2025 huggingface dataset:
X‐ray galaxy cluster studies for astro‐physics and cosmology
Authors: Böhringer H. , Schartel N.
Published: October 2014

The field of research on galaxy clusters has received an enormous increase in attention in the last years, since galaxy clusters have been more and more recognized as very important laboratories for astro‐physical studies and observational probes for testing cosmological models. X‐ray observations of these largest clearly defined objects in our Universe have been by far the most fruitful approach that has provided us with rich astro‐physical and cosmological insights. ESA's XMM‐Newton and NASA's Chandra observatories have been the powerhorses of this research. In this article we therefore like to summarize the major advances made in the field of galaxy cluster research primarily by these two instruments. We will touch the progress in understanding the structure of galaxy clusters and its statistics, the AGN feedback processes in the center of clusters, cosmic evolution of clusters, cluster mass measurements, the thermodynamic structure of the intracluster medium and its chemistry, X‐ray surveys of clusters, and the use of galaxy clusters for cosmological tests. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The MultiDark Database: Release of the Bolshoi and MultiDark cosmological simulations
Authors: Riebe K. , Partl A. M. , Enke H. , Forero‐Romero J. , Gottlöber S. , Klypin A. , Lemson G. , Prada F. , Primack J. R. , Steinmetz M. , Turchaninov V.
Published: October 2014

We present the online MultiDark Database – a Virtual Observatory‐oriented, relational database for hosting various cos‐mological simulations. The data is accessible via an SQL (Structured Query Language) query interface, which also allows users to directly pose scientific questions, as shown in a number of examples in this paper. Further examples for the usage of the database are given in its extensive online documentation. The database is based on the same technology as the Millennium Database, a fact that will greatly facilitate the usage of both suites of cosmological simulations. The first release of the MultiDark Database hosts two 8.6 billion particle cosmological N‐body simulations: the Bolshoi (250 h–1 Mpc simulation box, 1 h–1 kpc resolution) and MultiDark Run1 simulation (MDR1, or BigBolshoi, 1000 h–1 Mpc simulation box, 7 h–1 kpc resolution). The extraction methods for halos/subhalos from the raw simulation data, and how this data is structured in the database are explained in this paper. With the first data release, users get full access to halo/subhalo catalogs, various profiles of the halos at redshifts z = 0–15, and raw dark matter data for one time‐step of the Bolshoi and four time‐steps of the MultiDark simulation. Later releases will also include galaxy mock catalogs and additional merger trees for both simulations as well as new large volume simulations with high resolution. This project is further proof of the viability to store and present complex data using relational database technology. We encourage other simulators to publish their results in a similar manner. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The P1/P2 period ratio for kink oscillations of an asymmetrical coronal loop
Authors: Orza B. , Ballai I.
Published: October 2014

Here we investigate the effect of asymmetry of coronal loops on the P1/P2 period ratio of kink transverse loop oscillations. The P1/P2 period ratio technique is used for the diagnostics of the longitudinal structuring of coronal loops as its deviation from the canonical value of 2 is related to the density scale‐height along coronal loops. The analysis is carried out by calculating the period of the fundamental and first overtone of magnetohydrodynamic (MHD) kink oscillations for loops with different asymmetry degrees and density stratification. Taking into account the stratification and the deviation of the loop from a semi‐circular shape, we derive the equation that describes the dynamics of transversal kink oscillations and we use a numerical method to estimate the ratio of periods of oscillations. Solving numerically the problem, we show that the P1/P2 period ratio can change under the influence of loop asymmetry, e.g. for an asymmetrical loop with the displacement parameter α = 0.6, the change can reach 5–8%, i.e. density scale‐height estimations are overestimated by this amount. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A quest for activity cycles in low‐mass stars
Authors: Vida K. , Kriskovics L. , Oláh K.
Published: October 2014

Long‐term photometric measurements in a sample of ultrashort‐period (P ≈ 0.5 days or less) single and binary stars of different interior structures are analysed. A loose correlation exists between the rotational rate and cycle lengths of active stars, regardless of their evolutionary state and the corresponding physical parameters. The shortest cycles are expected for the fastest rotators of the order of 1–2 years, which is reported in this paper. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Black hole tidal charge constrained by strong gravitational lensing
Authors: Horváth Zs. , Gergely L. Á.
Published: October 2014

Spherically symmetric brane black holes have tidal charge which modifies both weak and strong lensing characteristics. Even if lensing measurements are in agreement with a Schwarzschild lens, the margin of error of the detecting instrument allows for a certain tidal charge only. In this paper we derive the respective constraint on the tidal charge of the supermassive black hole (SMBH) in the center of our galaxy, based on the radius of the first relativistic Einstein ring due to strong lensing. We find that even if general relativistic predictions are confirmed by high precision strong lensing measurements, SMBHs could have a much larger tidal charge than the Sun or neutron stars. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic fields in galaxy clusters
Authors: Brüggen M.
Published: October 2014

While it is established that galaxy clusters host magnetic fields of the order of a few µ G, both, their origin as well as their role in the intracluster medium (ICM) remain unclear. I will review the observational evidence for magnetic fields in galaxy clusters and present various lines of research that study the effects of magnetic fields in the ICM. Magnetic fields affect the way in which galaxies interact with the ICM, they may render the ICM buoyantly unstable in the presence of anisotropic thermal conduction, and they affect the thermal structure of the gas in cluster cores. Finally, opportunities for future research in this field, in particular in light of new radio telescopes is highlighted. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Formation of (exo–)planets
Authors: Dullemond C.P.
Published: October 2014

In this small review I will address three recent topics in the field of theoretical planet formation studies. This review is not meant to be complete in any way. It is meant to give an idea where some of the recent developments are. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Habitability and Multistability in Earth‐like Planets
Authors: Lucarini V. , Pascale S. , Boschi R. , Kirk E. , Iro N.
Published: October 2014

In this paper we explore the potential multistability of the climate for a planet around the habitable zone. We focus on conditions reminiscent to those of the Earth system, but our investigation has more general relevance and aims at presenting a general methodology for dealing with exoplanets. We describe a formalism able to provide a thorough analysis of the non‐equilibrium thermodynamical properties of the climate system and explore, using a flexible climate model, how such properties depend on the energy input of the parent star, on the infrared atmospheric opacity, and on the rotation rate of the planet. We first show that it is possible to reproduce the multi‐stability properties reminiscent of the paleoclimatologically relevant snowball (SB)–warm (W) conditions. We then characterise the thermodynamics of the simulated Wand SB states, clarifying the central role of the hydrological cycle in shaping the irreversibility and the efficiency of the W states, and emphasizing the extreme diversity of the SB states, where dry conditions are realized. Thermodynamics provides the clue for studying the tipping points of the system and leads us to constructing empirical parametrizations allowing for expressing the main thermodynamic properties as functions of the emission temperature of the planet only. Such empirical functions are shown to be rather robust with respect to changing the rotation rate of the planet from the current terrestrial one to half of it. Furthermore, we explore the dynamical range where the length of the day and the length of the year are comparable. We clearly find that there is a critical rotation rate below which the multi‐stability properties are lost, and the ice‐albedo feedback responsible for the presence of SB and W conditions is damped. The bifurcation graph of the system suggests the presence of a phase transition in the planetary system. Such critical rotation rate corresponds roughly to the phase‐lock 2:1 condition. Therefore, if an Earth‐like planet is 1:1 phase‐locked with respect to the parent star, only one climatic state would be compatible with a given set of astronomical and astro‐physical parameters. These results have relevance for the general theory of planetary circulation and for the definition of necessary and sufficient conditions for habitability. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
STILT: System design and performance
Authors: Mawson N.R. , Steele I.A. , Smith R.J.
Published: October 2014

The Small Telescopes Installed at the Liverpool Telescope (STILT) have been in operation since March 2009, collecting wide field data from their position, mounted to the Liverpool Telescope. The two instruments; SkycamT and SkycamZ have been used to create a variability search of the skies visible at La Palma with the limits of 12th and 18th R‐band magnitude with fields of view of 21°×21° and 1°×1°. We provide here a description of the hardware and software setup and the performance of the system to date. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
SOFIA: first science highlights and future science potential
Authors: Zinnecker H.
Published: October 2014

SOFIA, the Stratospheric Observatory for Infrared Astronomy, is a joint project between NASA and the German Aerospace Agency (DLR) to develop and operate a 2.5 m airborne telescope in a highly modified Boeing 747SP aircraft that can fly as high as 45000 feet (13.7 km). This is above 99.8 % of the precipitable water vapor which blocks much of the midand far‐infrared radiation from reaching ground‐based telescopes. In this review, we briefly discuss the characteristics of the Observatory and present a number of early science highlights obtained with the FORCAST camera in 5–40 micron spectral region and with the GREAT heterodyne spectrometer in the 130–240 micron spectral region. The FORCAST images in Orion show the discovery of a new high‐mass protostar (IRc4), while GREAT observations at 1 km s–1 velocity resolution detected velocity‐resolved, redshifted ammonia spectra at 1.81 THz in absorption against several strong farinfrared dust continuum sources, clear evidence of substantial protostellar infall onto massive (non‐ionizing) protostars. These powerful new data allow us to determine how massive stars form in our Galaxy. Another highlight is the stunning image taken by FORCAST that reveals the transient circumnuclear 1.5 pc radius (dust) ring around our Galactic center, heated by hundreds of massive stars in the young nuclear star cluster. The GREAT heterodyne spectrometer also observed the circumnuclear ring in highly excited CO rotational lines, indicative of emission from warm dense molecular gas with broad velocity structure, perhaps due to local shock heating. GREAT also made superb mapping observations of the [C II] fine structure cooling line at 158 microns, for example in M17‐SW molecular cloud–star cluster interface, observations which disprove the simple canonical photodissociation models. The much better baseline stability of the GREAT receivers (compared to Herschel HIFI) allows efficient on‐the‐fly mapping of extended [C II] emission in our galaxy and also in other nearby spiral galaxies. Of particular note is the GREAT discovery of two new molecules outside the solar system: OD (the deuterated OH hydroxyl radical) as well as mercapto radical SH, both in absorption near 1.4 THz, a frequency gap where Herschel was blind. A special highlight was the 2011 June 23 UT stellar occultation by Pluto using the HIPO high speed photometer and the FDC fast diagnostic camera. This difficult but successful observation, which was both space‐critical (within 100 km) and time‐critical (within 1 min), proved that SOFIA can be in the right place at the right time, when important transient events occur. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The M 4 Core Project with HST: I. Overview and first epoch
Authors: Bedin L.R. , Anderson J. , Heggie D.C. , Piotto G. , Milone A.P. , Giersz M. , Nascimbeni V. , Bellini A. , Rich R.M. , van den Berg M. , Pooley D. , Brogaard K. , Ortolani S. , Malavolta L. , Ubeda L. , Marino A.F.
Published: October 2014

We present an overview of the ongoing Hubble Space Telescope large program GO‐12911. The program is focused on the core of M 4, the nearest Galactic globular cluster, and the observations are designed to constrain the number of binaries with massive companions (black holes, neutron stars, or white dwarfs) by measuring the “wobble” of the luminous (mainsequence) companion around the center of mass of the pair, with an astrometric precision of ∼50 µas. The high spatial resolution and stable medium‐band PSFs of WFC3/UVIS will make these measurements possible. In this work we describe (i) the motivation behind this study, (ii) our observing strategy, (iii) the many other investigations enabled by this unique data set, and which of those our team is conducting, and (iv) a preliminary reduction of the first‐epoch dataset collected on 2012 October 10. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The 40 cm Monitoring Telescope of the Universitätssternwarte Bochum
Authors: Ramolla M. , Drass H. , Lemke R. , Westhues C. , Pozo Nuñez F. , Barr Dominguez A. , Haas M. , Chini R. , Murphy M.
Published: October 2014

The new 40cm Bochum Monitoring Telescope (BMT) has started routine operation at the Universitätssternwarte Bochum (USB), located near Cerro Armazones in Chile. It has a 41′ × 27′ field of view (FoV) and is equipped with B and V broad band filters and three narrow band filters at 670, 680, and 690 nm. This makes the BMT ideally suited to perform photometric reverberation mapping of the Hα emission line of active galactic nuclei, where the line is redshifted into the narrow bands, and to monitor bright stars which would be saturated with large telescopes. As a complement to our Robotic Bochum Twin Telescope (RoBoTT) with 2°.7 FoV and 14 filters, the BMT is an efficient instrument to accurately study the variability of individual sources, provided that its smaller FoV covers a sufficient number of suitable comparison stars. Here we describe the telescope and its fully robotic operation, and present science verification data demonstrating the performance of the BMT. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the distance scale of open clusters
Authors: Loktin A.V.
Published: October 2014

We discuss the state of the distance scale of open clusters in view of various capabilities provided by optical and near‐IR observations of galactic objects. Various checks lead to the conclusion that open cluster distance scale requires no appreciable correction. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Metallicity field and selection effects in spatial distribution of the Galactic globular cluster system
Authors: Nikiforov I.I. , Smirnova O.V.
Published: October 2014

The prospects for using the present‐day data on metallicity of globular clusters (GCs) of the Galaxy to put constraints on the distance to the Galactic center, R0, are considered. We have found that the GCs of the metal‐rich and metal‐poor subsystems separately form a bar‐like structure in metallicity maps whose parameters are very close to those for the Galactic bar. The results indicate the existence of a bar component within both the metal‐rich and metal‐poor subsystems of GCs. The bar GCs could have formed within the already existing Galactic bar or could have later been locked in resonance with the bar. We conclude that substantial constraints on the R0 value can be obtained only with non‐axisymmetric models for the space distribution of GC metallicities with the allowance for the subdivision of GCs into subsystems. We found evidence for a bar extinction component that causes the observational incompleteness of GCs in the far side of the Galactic bar and in the “post‐central” region. This selection effect should be taken into account when determining R0 from the spatial distribution of GCs. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface photometry of dwarf irregular galaxies in different environments
Authors: Sharina M.E. , Il'ina E.A.
Published: October 2014

We present surface photometry and determination of structural parameters for 93 dwarf irregular (dIrr) galaxies located in different environments at distances ≤50 Mpc. This work was carried out using SDSS images. The luminosity‐surface density relation obtained for galaxies in small groups agrees with that found for the local volume dwarf galaxies. However, isolated objects in our sample objects appear to have, on average, lower surface brightnesses and larger scale lengths at a given luminosity than the galaxies in higher‐density environments. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two‐component outer ring and the observed galactic spiral structure
Authors: Mel'nik A.M. , Rautiainen P.
Published: October 2014

We show that a model of the Galaxy with a two‐component outer ring of class R1R2 can explain many large‐scale morphological features of the galactic spiral structure. The Carina‐Sagittarius arm may consist of two ascending segments of outer R1 and R2 rings, which almost touch each other near the Carina region. The Perseus and Crux arms can be partially identified with the descending segments of the R2 ring. A model of a two‐component outer ring can also explain the existence of some tangential directions. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interstellar reddening information system
Authors: Burnashev V.I. , Grigorieva E.A. , Malkov O.Yu.
Published: October 2014

We describe an electronic bibliographic information system, based on a card catalog, containing some 2500 references (publications of 1930–2009) on interstellar extinction. We have classified the articles according to their content. We present here a list of articles devoted to two categories: maps of total extinction and variation of interstellar extinction with the distance to the object. The catalog is tested using published data on open clusters, and conclusions on the applicability of different maps of interstellar extinctions for various distances are made. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Radii of LMC and SMC Cepheids
Authors: Kanev E.N.
Published: October 2014

We collected long sets of precise radial velocity observations of radial velocities for 8 SMC and 14 LMC Cepheids. Based on these series of radial velocity measurements and on multicolor photoelectric observations, we calculated radii of the program extragalactic Cepheids using a modification of Balona's method. Our main goal was to determine the long‐period branch of the period‐radius diagram and reveal a dependence on metallicity. We derived the following period‐radius relation: log R = 1.06(±0.03)+0.74(±0.02) log P. We did not find any significant difference between the period‐radius relation of extragalactic Cepheids and that of fundamental‐mode galactic Cepheids. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Apex and internal structure of the Praesepe open cluster
Authors: Vereshchagin S.V. , Chupina N.V.
Published: October 2014

The results of a study of the internal structure and kinematics of the Praesepe cluster are reported. The “AD‐diagram” method is used to determine the position of the cluster apex, which is found to be close to the apex positions of other clusters, in particular to the Hyades apex. The internal morphology of the cluster is also analyzed. The distribution of the Praesepe members in the XY ‐plane shows that the cluster consists of a homogeneous core and a non‐uniform corona. An analysis of stellar radial velocities and parallaxes reveals their weak correlation. This might be due to the axial rotation of the cluster. The inferred rotational velocity is comparable with that of the Hyades within the quoted errors. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the two‐dimensional maps of the distribution of interstellar extinction
Authors: Loktin A.V.
Published: October 2014

A modified version of the method for determining the mean interstellar extinction and constructing the maps of its distribution based on JHK s photometry is proposed. The extinction for each star of the sample is estimated from the Q ‐index by linearly approximating the line of unreddened stars on the QJHK – (J – H) diagram. The J ‐band extinction can be calculated by the equation AJ = 2.68 [(J – H) + 0.03 – 1.18 QJHK]. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A search for double‐mode pulsating variables
Authors: Khruslov A.V.
Published: October 2014

I report on the discovery of 46 double‐mode pulsating variable stars in publicly available data of sky surveys. Among these stars, there are 12 Galactic Cepheids pulsating in the first and second radial overtones. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spiral‐vortex structures generation in gaseous galactic disks with a two‐hump rotation curve
Authors: Torgashin Yu.M. , Omurkanov T.Z.
Published: October 2014

The hydrodynamic (HD) global modes of oscillations in thin gaseous disks of solitary flat galaxies are numerically investigated. The unstable HD modes are shown to be generated in the gaseous disk when the rotation curve has a velocity “kink” (velocity jump) in the inner disk region (as observed in many nearby spiral galaxies). These unstable HD modes show up as spiral‐vortex dynamical structures with special features, such as growth rates, shape of surface density perturbations, angular pattern speed, etc. Depending on the rotation curve parameters and on the gaseous disk temperature, the properties of unstable modes for the main azimuthal harmonics m = 1–4 are investigated. Along with the centrifugal branch of perturbations, unstable over‐reflection modes are investigated as well, showing a resonance dependence of the growth rate on the temperature of the gaseous disk. The main features of the banana‐like anticyclonic vortices, which form in the perturbed velocity field simultaneously with the spiral density wave, are also studied. The case of the model gaseous disk that approximates the observed one in the M 31 galaxy is studied as application. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New series of equilibrium figures based on the Roche model
Authors: Kondratyev B.P. , Trubitsina N.G.
Published: October 2014

A 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

We 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

We 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

We 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

The 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

High 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

The 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

HERMES, 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

The 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

Sunspot 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

Spectropolarimetric 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

At 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

We 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

The 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

Eclipsing 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

We 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

The 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

Developments 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)
eROSITA – Mapping the X‐ray universe
Authors: Predehl P.
Published: October 2014

eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the core instrument on the Russian/German Spektrum‐Roentgen‐Gamma (SRG) mission which is currently scheduled for launch late 2015/early 2016. eROSITA will perform a deep survey of the entire X‐ray sky. In the soft band (0.5–2 keV), it will be about 30 times more sensitive than ROSAT, while in the hard band (2–8 keV) it will provide the first ever true imaging survey of the sky. The design driving science is the detection of large samples of galaxy clusters to redshifts z > 1 in order to study the large scale structure in the universe and test cosmological models including dark energy. In addition, eROSITA is expected to yield a sample of a few million active galactic nuclei, including obscured objects, revolutionizing our view of the evolution of supermassive black holes. The survey will also provide new insights into a wide range of astro‐physical phenomena, including X‐ray binaries, active stars, and diffuse emission within the Galaxy. eROSITA is currently (Jan 2014) in its flight model and calibration phase. All seven flight mirror modules (plus one spare) have been delivered and measured in X‐rays. The first camera including the complete electronics has been extensively tested. So far, all subsystems and components are well within the expected performance. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)