bluuebunny/crossref_metadata_2025_split huggingface dataset:
X‐ray galaxy cluster studies for astro‐physics and cosmology
Authors: Böhringer H. , Schartel N. 
Published: October 2014

AbstractThe 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

AbstractWe 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

AbstractHere 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

AbstractLong‐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

AbstractSpherically 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

AbstractWhile 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

AbstractIn 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

AbstractIn 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

AbstractThe 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

AbstractSOFIA, 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

AbstractWe 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

AbstractThe 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

AbstractWe 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

AbstractThe 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

AbstractWe 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

AbstractWe 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

AbstractWe 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

AbstractWe 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

AbstractThe 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

AbstractA 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

AbstractI 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

AbstractThe 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)