bluuebunny/crossref_metadata_2025 huggingface dataset:
Fundamental properties of lower main‐sequence stars
Authors: Torres G.
Published: October 2014

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

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

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

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

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

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

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

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

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

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

Parameter regions in which stars can become pulsationally unstable are found throughout the Hertzsprung‐Russell diagram. Stars of high, intermediate, low, and very low masses may cross various instability regions along their paths of evolutionary sequences. In describing them, I give special consideration to hybrid pulsational characteristics that are particularly valuable for asteroseismic investigations, to $ \dot P $ measurements that allow us to directly follow the stellar evolutionary changes in some stars, and to new research results that stand out with respect to previous consensus (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Starspot simulations for Kepler
Authors: Nielsen M.B. , Karoff C.
Published: October 2014

The NASA Kepler mission yields an unprecedented amount of data in the form of photometric light curves. Apart from valuable information on exoplanets and stellar pulsations, the light curves contain rotation signals from starspots crossing the stellar disk. These modulations of the light curves are modeled and 105 simulations are carried out to analyze and understand a similar analysis of the Kepler light curves. The periodogram is calculated for each light curve. Under the assumption that the main source of variability at periods >1 day is due to spots, the simulations show that the rotation period can be easily determined for spot lifetimes of 30–60 days, but becomes more unreliable for spots lifetimes of 10–20 days. The amplitude of the periodogram peaks appear to be only weakly dependent on changes in the size of the spots, while the width of the peaks shows no clear change with increasing spot lifetimes (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ground‐based multi‐color photometry of the γ Doradus–δ Scuti hybrid star KIC 6761539
Authors: Herzberg W. , Uytterhoeven K. , Roth M.
Published: October 2014

We present a preliminary analysis of the first three nights of multi‐color photometric data for a γ Doradus‐δ Scuti hybrid star (KIC 6761539) that is also being observed with the Kepler space telescope. We find that up to four (depending on the filter) of the highest amplitude modes, whose frequencies could be determined from Kepler data, are visible from the ground. Our goal is to use the multi‐color information for mode identification, but this will only be possible with a longer time series. A multi‐color photometric multi‐site campaign is currently ongoing for this purpose (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Identification of pulsational modes in rotating slowly pulsating B stars
Authors: Szewczuk W. , Daszyńska‐Daszkiewicz J.
Published: October 2014

Mode identification for several slowly pulsating B‐type stars (SPB) including effects of rotation is presented. The effects of the Coriolis force are incorporated via the traditional approximation. We show that even for slow rotators amongst the SPB stars, rotation cannot be ignored when the angular numbers of pulsational modes are determined. Moreover, some constraints on the rotational velocity and inclination angle are derived (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Blazhko modulation of TV Boo in 2010
Authors: Hajdu G. , Jurcsik J. , Sódor Á. , Szeidl B. , Smitola P. , Belucz B. , Posztobányi K. , Vida K. , Kun E.
Published: October 2014

We present the analysis of the multicolour CCD observations in the 2010 season of the Blazhko RRc star TV Boo. TV Boo shows a complex Blazhko modulation dominated by two independent modulations with periods Pfm1 = 9.74 d and Pfm2 = 21.43 d. Both modulation components appear in the frequency spectra as multiplet structures around the harmonics of the pulsation. The positive value of the asymmetry parameter (Q = +0.51) of the primary modulation suggests that it is similar in its character to the Blazhko‐effect of most of the modulated RRab stars. Interestingly, the secondary, lower‐amplitude modulation exhibits a negative asymmetry parameter (Q = −0.22), which is an unusually low value when compared to the Blazhko‐modulated RRab stars. Apart from the two modulation frequencies, the spectra also show an additional frequency f’ and its linear combinations with the pulsation and the primary modulation f1 + f’ and f1 − f’ − fm1. We conclude that the additional frequency most probably belongs to a non‐radial mode (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Kappa‐effect and brightness oscillations of stars
Authors: Zhugzhda Y. D. , Roth M. , Herzberg W.
Published: October 2014

In this paper the theory of visibility and darkening functions for the brightness oscillations of stars is outlined. For this the non‐grey approximation is used and the effect of opacity disturbances on stellar brightness oscillations is explored for different types of stars. An explanation of the Procyon paradox is proposed. Special features of the brightness oscillations are discussed. The effect of opacity fluctuations on the damping of p‐mode oscillations is considered. Furthermore, the photospheric kappa‐mechanism is discussed (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low‐frequency heliographic observations of the quiet Sun corona
Authors: Stanislavsky A.A. , Koval A.A. , Konovalenko A.A.
Published: October 2014

We present new results of heliographic observations of quiet‐Sun radio emission fulfilled by the UTR‐2 radio telescope. The solar corona investigations have been made close to the last solar minimum (Cycle 23) in the late August and early September of 2010 by means of the two‐dimensional heliograph within 16.5–33 MHz. Moreover, the UTR‐2 radio telescope was used also as an 1‐D heliograph for one‐dimensional scanning of the Sun at the beginning of September 2010 as well as in short‐time observational campaigns in April and August of 2012. The average values of integral flux density of the undisturbed Sun continuum emission at different frequencies have been found. Using the data, we have determined the spectral index of quiet‐Sun radio emission in the range 16.5–200 MHz. It is equal to –2.1±0.1. The brightness distribution maps of outer solar corona at frequencies 20.0 MHz and 26.0 MHz have been obtained. The angular sizes of radio Sun were estimated. It is found that the solar corona at these frequencies is stretched‐out along equatorial direction. The coefficient of corona ellipticity varies slightly during above period. Its mean magnitudes are equal to ≈ 0.75 and ≈ 0.73 at 20.0 MHz and 26.0 MHz, respectively. The presented results for continuum emission of solar corona conform with being ones at higher frequencies. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
X‐ray luminosity functions of different morphological and X‐ray type AGN populations
Authors: Pović M. , Pérez García A.M. , Sánchez‐Portal M. , Bongiovanni A. , Cepa J. , Fernández Lorenzo M. , Lara‐López M.A. , Gallego J. , Ederoclite A. , Márquez I. , Masegosa J. , Alfaro E. , Castañeda H. , González‐Serrano J.I. , González J.J.
Published: October 2014

Luminosity functions are one of the most important observational clues when studying galaxy evolution over cosmic time. In this paper we present the X‐ray luminosity functions for X‐ray detected AGN in the SXDS and GWS fields. The limiting fluxes of our samples are 9.0 ×10–15 and 4.8 ×10–16 erg cm–2 s–1 in the 0.5–7.0 keV band in the two fields, respectively. We carried out analysis in three X‐ray bands and in two redshift intervals up to z ≤ 1.4. Moreover, we derive the luminosity functions for different optical morphologies and X‐ray types. We confirm strong luminosity evolution in all three bands, finding the most luminous objects at higher redshift. However, no signs of density evolution are found in any tested X‐ray band. We obtain similar results for compact and early‐type objects. Finally, we observe the “Steffen effect”, where X‐ray type‐1 sources are more numerous at higher luminosities in comparison with type‐2 sources. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bulk motion measurements in clusters of galaxies with ATHENA‐like missions
Authors: Nevalainen J.
Published: October 2014

The hierarchical formation of clusters of galaxies by accretion of material releases gravitational energy which dissipates into the intracluster gas. The process heats the material and generates gas turbulence and bulk motions and thus kinetic pressure. Mapping the velocity fields of the moving subunits would enable a new diagnostics tool for cluster formation studies and unbiased X‐ray mass estimates. The required spatially resolved high resolution spectroscopy is not currently available. I demonstrate here the feasibility of detecting and mapping the velocities of the bulk motions using the Doppler shift of the Fe XXV Kα line with the proposed ATHENA satellite. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
X‐ray observations of the merging cluster CIZA J2242.8+5301
Authors: Ogrean G. , Brüggen M. , Simionescu A. , Röttgering H. , van Weeren R.J. , Croston J.H. , Hoeft M.
Published: October 2014

Multiwavelength studies of radio relics at merger shocks set powerful constraints on the relics origin and formation mech‐anism. However, for X‐ray observations, a main difficulty is represented by the low X‐ray surface brightness far out in the cluster outskirts, where relics are typically found. Here, we present XMM‐Newton results from a 130‐ks observation of CIZA J2242.8+5301, a cluster at z = 0.19 that hosts a double radio relic. We focus on the well‐defined northern relic. There is a difference of ∼55% between the temperature we measure behind the relic, and the temperature measured with Suzaku. We analyse the reasons for this large discrepancy, and discuss the possibility of reliably measuring the temperature beyond the northern relic. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Merger shocks in Abell 3667 and the Cygnus A cluster
Authors: Sarazin C.L. , Finoguenov A. , Wik D.R.
Published: October 2014

We present new XMM‐Newton observations of the northwest (NW) radio relic region in the cluster Abell 3667. We detect a jump in the X‐ray surface brightness and X‐ray temperature at the sharp outer edge of the radio relic which indicate that this is the location of a merger shock with a Mach number of about 2. Comparing the radio emission to the shock properties implies that approximately 0.2% of the dissipated shock kinetic energy goes into accelerating relativistic electrons. This is an order of magnitude smaller than the efficiency of shock acceleration in many Galactic supernova remnants, which may be due to the lower Mach numbers of cluster merger shocks. The X‐ray and radio properties indicate that the magnetic field strength in the radio relic is ≳ 3 µG, which is a very large field at a projected distance of ∼ 2.2 Mpc from the center of a cluster. The radio spectrum is relatively flat at the shock, and steepens dramatically with distance behind the shock. This is consistent with radiative losses by the electrons and the post‐shock speed determined from the X‐ray properties. The Cygnus A radio source is located in a merging cluster of galaxies. This appears to be an early‐stage merger. Our recent Suzaku observation confirm the presence of a hot region between the two subclusters which agrees with the predicted shocked region. The high spectral resolution of the CCDs on Suzaku allowed us to measure the radial component of the merger velocity, Δvr ≈ 2650 km s–1. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cluster mass profiles from X‐ray observations: Present constraints and limitations
Authors: Ettori S.
Published: October 2014

The distribution of the gravitating and baryonic mass in galaxy clusters is the key ingredient to use these structures as astro‐physical laboratories and cosmological probes. I review the methods used to recover the gas and total mass profiles for galaxy clusters from X‐ray observations. I discuss some of the limitations affecting the X‐ray analysis. I illustrate how the estimates of the gas mass fraction and of the mass concentration can be used as robust cosmological tools. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
X‐ray emission from RX J1720.1+2638 and Abell 267: A comparison between a fossil and a non‐fossil system
Authors: Jiménez‐Bailón E. , Lozada‐Muñoz M. , Aguerri J.A.L.
Published: October 2014

We present the XMM‐Newton X‐ray analysis of RX J1720.1+2638 and Abell 267, a non‐fossil and a fossil system, respectively. The whole spectrum of both objects can be explained by thermal emission. The luminosities found for RX J1720.1+2638 and Abell 267 in the 2–10 keV band are 6.20+0.04 –0.02 × 1044 and 3.90+0.10 –0.11 ×1044 erg s–1, respectively. The radial profiles show a cool core nature for the non‐fossil system RX J1720.1+2638, while Abell 267 shows a constant behaviour of temperature with radius. Metallicity profiles have also been produced, but no evidence of any gradient was detected due to the large uncertainties in the determination of this parameter. Finally, density and mass profiles were also produced allowing to derive M500 for RX J1720.1+2638 and Abell 267. The masses obtained are high, in the range of (5–7)× 1014 M⊙. The X‐ray properties obtained for both systems are not always in good agreement with what is expected: cool cores are expected for fossil systems, as Abell 267, considering them as and relaxed systems. However, the decrement of the temperature in Abell 267 could start at lower radii. Also the presence of a recent merger in Abell 267, already suggested in the literature, could have increased the central temperature. The non‐fossil system RX J1720.1+2638 actually exhibits a cool core profile, but also evidence of a recent merger has been reported. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
X‐ray properties and scaling relations for Planck ESZ clusters
Authors: Jones C. , Forman W. , Fogarty K. , Murray S. , Vikhlinin A.
Published: October 2014

Clusters of galaxies were first recognized through overdensities of galaxies. With the advent of X‐ray telescopes, large numbers of clusters were by found by the spatially extended nature of their X‐ray emission. Today with the availability of millimeter wave telescopes capable of finding clusters through the Sunyaev‐Zeldovich effect, it is possible to compare the overall characteristics of clusters detected by different methods and the specific properties of individual clusters measured in different ways. Here we compare the X‐ray properties of relatively low redshift clusters measured with the Chandra Observatory with their SZ signal measured in the Planck mission. Based on a sample of 114 Planck detected clusters of galaxies, we show the SZ signal strengths are strongly correlated with X‐ray measured mass proxies, in particular those measured through the cluster X‐ray luminosities, so long as the cluster core is excluded, and those measured from YX, the product of the gas temperature and gas mass, which is an X‐ray analog of the SZ signal YSZ. A comparison of the hundred brightest X‐ray clusters and the hundred Planck clusters with the highest SZ signals shows that the Planck ESZ cluster sample is more X‐ray luminous and more massive than X‐ray cluster sample, due in part to the larger volume that Planck clusters are detected over, due to the nearly redshift independence of the SZ strength. As previously found, on average the SZ cluster samples show a larger fraction of clusters undergoing mergers than do X‐ray selected samples. For the Planck ESZ cluster PLCKESZ G189.84–37.24, we report the detection of extended X‐ray emission associated with an overdensity of distant galaxies located 6′.5 from the Planck ESZ position. Future X‐ray observations of the Planck low redshift (z < 0.35) cluster sample will better define the low redshift cluster mass function for comparison to high redshift SZ selected cluster samples to better constrain cosmological parameters, particularly the equation of state for dark energy. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On mass and shape of galaxy clusters by comparison of X‐ray, Sunyaev‐Zel'dovich effect, and gravitational lensing observations
Authors: Sereno M. , Umetsu K. , Ettori S. , Baldi A.
Published: October 2014

The accurate determination of the mass of galaxy clusters is crucial to precision astronomy. We have often to deal with either biased measurements or precise determinations of peculiar quantities. A better understanding of intrinsic shapes plays a major role. We consider how the shape of the intracluster medium (ICM) can be inferred by combining X‐ray photometry and spectroscopy with the measurement of the Sunyaev‐Zel'dovich effect (SZe). Together with gravitational lensing (GL), we can get unbiased estimates of mass and concentration and probe the hydrodynamical properties of the cluster. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Search for galaxy‐ICM interaction in rich clusters of galaxies
Authors: Gu L. , Gandhi P. , Inada N. , Kawaharada M. , Kodama T. , Konami S. , Nakazawa K. , Shimasaku K. , Xu Haiguang , Makishima K.
Published: October 2014

Based on optical and X‐ray data for a sample of 34 relaxed rich clusters with redshift of 0.1–0.9, we studied the relative spatial distribution of the two major baryon contents, the cluster galaxies and the hot plasmas. Using photometric data taken with the UH88 telescope, we determined the integrated radial light profiles of member galaxies in each cluster using two independent approaches, i.e., the field background subtraction and the color‐magnitude filtering. The ICM mass profile of each cluster in our sample was derived from a spatially‐resolved spectral analysis using XMM‐Newton and Chandra data. When the sample is divided into three subsamples with redshift intervals of z = 0.11–0.22, 0.22–0.45, and 0.45– 0.89, the galaxy light vs. ICM mass ratio profiles for the central 0.65R500 regions were found to steepen from the higher‐ to lower‐ redshift subsamples, meaning that the galaxies become more concentrated in the ICM sphere towards lower redshifts. Besides, the galaxy light vs. total mass ratio profiles also exhibit gradual concentration towards lower redshift. We interpret that the galaxies, the ICM, and the dark matter components followed a similar spatial distribution in the early phase (z > 0.5), while the galaxies have fallen towards the center relative to the ICM and dark matter. Such galaxy infall is likely tobe caused by ICM drag when galaxies move through the ICM, even though the dynamical friction can enhance the infall of the most massive galaxies. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Galaxy And Mass Assembly (GAMA): The M‐Z relation for galaxy groups
Authors: Lara‐López M.A. , Hopkins A.M. , Robotham A. , Owers M.S. , Colless M. , Brough S. , Norberg P. , Steele O. , Taylor E.N. , Thomas D.
Published: October 2014

The stellar mass and metallicity are among the fundamental parameters of galaxies. An understanding of the interplay between those properties as well as their environmental dependence will give us a general picture of the physics and feedback processes ongoing in groups of galaxies. We study the relationships and environmental dependencies between the stellar mass, and gas metallicity for more than 1900 galaxies in groups up to redshift 0.35 using the Galaxy And Mass Assembly (GAMA) survey. Using a control sample of more than 28000 star‐forming field galaxies, we find evidence for a decrement of the gas metallicity for galaxies in groups. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A spectral differential approach to characterizing low‐mass companions to late‐type stars
Authors: Kostogryz N.M. , Kürster M. , Yakobchuk T.M. , Lyubchik Y. , Kuznetsov M.K.
Published: October 2014

In this paper, we develop a spectral differential technique with which the dynamical mass of low‐mass companions can be found. This method aims at discovering close companions to late‐type stars by removing the stellar spectrum through a subtraction of spectra obtained at different orbital phases and discovering the companion spectrum in the difference spectrum in which the companion lines appear twice (positive and negative signal). The resulting radial velocity difference of these two signals provides the true mass of the companion, if the orbital solution for the radial velocities of the primary is known. We select the CO line region in the K band for our study, because it provides a favourable star‐to‐companion brightness ratio for our test case GJ 1046, an M2V dwarf with a low‐mass companion that most likely is a brown dwarf. Furthermore, these lines remain largely unblended in the difference spectrum so that the radial velocity amplitude of the companion can be measured directly. Only if the companion rotates rapidly and has a small radial velocity due to a high mass, does blending occur for all lines so that our approach fails. We also consider activity of the host star, and show that the companion difference flux can be expected to have larger amplitude than the residual signal from the active star so that stellar activity does not inhibit the determination of the companion mass. In addition to determining the companion mass, we restore the single companion spectrum from the difference spectrum using singular value decomposition. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic fields during high redshift structure formation
Authors: Schleicher D.R.G. , Latif M. , Schober J. , Schmidt W. , Bovino S. , Federrath C. , Niemeyer J. , Banerjee R. , Klessen R.S.
Published: October 2014

We explore the amplification of magnetic fields in the high‐redshift Universe. For this purpose, we perform high‐resolution cosmological simulations following the formation of primordial halos with ∼ ⊙ 107 M, revealing the presence of turbulent structures and complex morphologies at resolutions of at least 32 cells per Jeans length. Employing a turbulence subgrid‐scale model, we quantify the amount of unresolved turbulence and show that the resulting turbulent viscosity has a significant impact on the gas morphology, suppressing the formation of low‐mass clumps. We further demonstrate that such turbulence implies the efficient amplification of magnetic fields via the small‐scale dynamo. We discuss the properties of the dynamo in the kinematic and non‐linear regime, and explore the resulting magnetic field amplification during primordial star formation. We show that field strengths of ∼ 10–5 G can be expected at number densities of ∼ 5 cm–3. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Brightness fluctuations of the Sun and p‐mode oscillations: The inverse problem and nonadiabatic waves in the photosphere
Authors: Prokhorov A. , Zhugzhda Y.D. , Berdyugina S.
Published: October 2014

Using photometric observations of the Sun as a star (DIFOS, SoHO) we were able to solve the inverse heloiseismic problem and determine the global time‐dependent relative temperature fluctuations as functions of the geometric height. This was done under the adiabatic assumption. A mathematical tool was developed to solve the inverse problem, which is ill‐posed. The calculations were done using the numerical software Matlab 7. The adiabatic solution shows signs of temperature waves in the lower photosphere, which agrees with calculations done by Rodríguez Hidalgo et al. (2001) and Stodilka (2011). (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Probing the temporal and spatial variations of dust emission in the protoplanetary disk of DG Tau with VLTI/MIDI: Preliminary results
Authors: Gabányi K. É. , Mosoni L. , Juhász A. , Ábrahám P. , Ratzka Th. , Sipos N. , van Boekel R. , Jaffe W.
Published: October 2014

The signatures of dust processing and grain growth – related to the formation of rocky planets – are easily seen in midinfrared spectral features. One important diagnostic tool in this context is the silicate feature in the spectra of young stellar objects (YSO). The low‐mass YSO, DG Tau shows unique temporal variations in its silicate feature. We conducted multi‐epoch observations of DG Tau with the MID‐Infrared Interferometric instrument of the Very Large Telescope Interferometer to obtain the spectra of the inner and outer disk regions in order to investigate where the previously reported variations of the silicate feature originate from. Here we present the preliminary results of the first two epochs of observations. We found that on a time‐scale of two months, the source showed significant brightening. At the same time the mid‐infrared emitting region expanded. While the identification of the silicate feature is difficult, our results qualitatively agree with the scenario explaining the varying silicate feature with dust lifted up above the disk. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Fly's Eye Camera System: An instrument design for large étendue time‐domain survey
Authors: Pál A. , Mészáros L. , Csépány G. , Jaskó A. , Schlaffer F. , Vida K. , Mező Gy. , Döbrentei L. , Farkas E. , Kiss Cs. , Oláh K. , Regály Zs.
Published: October 2014

In this paper we briefly summarize the design concepts of the Fly's Eye Camera System, a proposed high resolution allsky monitoring device which intends to perform high cadence time domain astronomy in multiple optical passbands while still accomplish a high étendue. Fundings have already been accepted by the Hungarian Academy of Sciences in order to design and build a Fly's Eye device unit. Beyond the technical details and the actual scientific goals, this paper also discusses the possibilities and yields of a network operation involving ∼10 sites distributed geographically in a nearly homogeneous manner. Currently, we expect to finalize the mount assembly – that performs the sidereal tracking during the exposures – until the end of 2012 and to have a working prototype with a reduced number of individual cameras sometimes in the spring or summer of 2013. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The use of UV‐VIS‐NIR reflectance spectroscopy to identify iron minerals
Authors: Szalai Z. , Kiss K. , Jakab G. , Sipos P. , Belucz B. , Németh T.
Published: October 2014

Iron minerals – which behave as indicators in earthly and Martian environments – can be identified by UV‐VIS‐NIR reflectance spectroscopy. The aim of this study was to compare the spectra of various soils and sediments all of which contain iron minerals but developed under different environmental conditions. To identify the mineral of the sediments we used the first and second derivatives of the Kubelka‐Munk transformed spectra. According to their iron mineral composition, the analysed samples can be divided into three distinct groups. Goethite refers to the hydromorphic conditions, hematite suffers from the long and intense weathering in leaching environment. In the case of steppe climatic conditions the weathering is so weak that the appearance of pedogenic iron minerals is improbable in these soils. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Turbulent magnetic energy spectrum and the cancellation function of solar photospheric magnetic fields
Authors: Marschalkó G. , Petrovay K.
Published: October 2014

A simple analytical relation of form α = 2κ – 1 between the magnetic energy spectral exponent α of the turbulent magnetic field in the solar photosphere and its magnetic flux cancellation exponent κ, valid under certain restrictive assumptions, is tested and extended outside its range of validity in a series of Monte Carlo simulations. In these numerical tests artificial “magnetograms” are constructed in 1D and 2D by superposing a discrete set of Fourier modes of the magnetic field distribution with amplitudes following a power law spectrum and measuring the cancellation function on these simulated magnetograms. Our results confirm the validity of the analytical relation and extend it to the domain α < –1 where κ → 0 as α → –∞. The observationally derived upper limit of 0.38 on κ implies α < –0.24 in the granular size range, apparently at odds with a small scale dynamo driven in the inertial range. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Oscillator models of the solar cycle and the Waldmeier effect
Authors: Nagy M. , Petrovay K.
Published: October 2014

We study the behaviour of the van der Pol oscillator when either its damping parameter μ or its nonlinearity parameter ξ is subject to additive or multiplicative random noise. Assuming various power law exponents for the relation between the oscillating variable and the sunspot number, for each case we map the parameter plane defined by the amplitude and the correlation time of the perturbation and mark the parameter regime where the sunspot number displays solar‐like behaviour. Solar‐like behaviour is defined here as a good correlation between the rise rate and cycle amplitude and the lack of a good correlation between the decay rate and amplitude, together with significant (≳10%) r.m.s. variation in cycle lengths and cycle amplitudes. It is found that perturbing μ alone the perturbed van der Pol oscillator does not show solar‐like behaviour. When the perturbed variable is ξ, solar‐like behaviour is displayed for perturbations with a correlation time of about 3–4 years and significant amplitude. Such studies may provide useful constraints on solar dynamo models and their parameters. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A statistical analysis on the relationship between thunderstorms and the sporadic E Layer over Rome
Authors: Barta V. , Scotto C. , Pietrella M. , Sgrigna V. , Conti L. , Sátori G.
Published: October 2014

Meteorological processes (cold fronts, mesoscale convective complexes, thunderstorms) in the troposphere can generate upward propagating waves in the neutral atmosphere affecting the behaviour of the ionosphere. One type of these waves are the internal atmospheric gravity waves (AGWs) which are often generated by thunderstorms. Davis & Johnson (2005) found in low pressure systems that a localized intensification of the sporadic E layer (Es) can be attributed to lightnings. To confirm this result, we have performed two different statistical analysis using the time series of the critical frequency (foEs), the virtual height of the sporadic E layer (h'Es), and meteorological observations (lightnings, Infrared maps) over the ionospheric station of Rome (41.9° N, 12.5° E). In the first statistical analysis, we separated the days of 2009 into two groups: stormy days and fair‐weather days, then we studied the occurrence and the properties of the Es separately for the two different groups. No significant differences have been found. In the second case, a superposed epoch analysis (SEA) was used to study the behaviour of the critical frequency and virtual height 100 hours before and after the lightnings. The SEA shows a statistically significant decrease in the critical frequency after the time of the lightnings, which indicates a sudden decrease in the electron density of the sporadic E layer associated with lightnings. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Empirical formulae of temperature and luminosity as functions of mass for calculating the habitable zone
Authors: Dobos V. , Orgoványi J. , Nagy I.
Published: October 2014

The location of the habitable zone can be calculated from the stellar mass by theoretical expressions. In this work we compare different effective temperature and luminosity relations from which the habitable zone is calculated. It was found that for the effective temperature the theoretical models give acceptable results but for the luminosity the measured values are underestimated. Because of the experienced deviation we propose new empirical equations for F, G, K, M main sequence stars (0.3–1.4 M⊙) hosting known exoplanets. Using these equations the boundaries of the habitable zone fit well to the ones which were calculated from measured stellar parameters. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Refined position angle measurements for galaxies of the SDSS Stripe 82 co‐added dataset
Authors: Varga J. , Csabai I. , Dobos L.
Published: October 2014

Position angle measurements of Sloan Digital Sky Survey (SDSS) galaxies, as measured by the surface brightness profile fitting code of the SDSS photometric pipeline (Lupton et al. 2001), are known to be strongly biased, especially in the case of almost face‐on and highly inclined galaxies. To address this issue we developed a reliable algorithm which determines position angles by means of isophote fitting. In this paper we present our algorithm and a catalogue of position angles for 26397 SDSS galaxies taken from the deep co‐added Stripe 82 (equatorial stripe) images. Data are published on‐line at http://www.vo.elte.hu/galmorph. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constraints on supermassive black hole spins from observations of active galaxy jets
Authors: Kun E. , Wiita P.J. , Gergely L.Á. , Keresztes Z. , Gopal‐Krishna  , Biermann P.L.
Published: October 2014

We discuss the origin of the low‐energy cutoff, or LEC, seen in the radio spectra of many extragalactic jets and relate this to the spin of the supermassive black holes that presumably power them. Pion decay via proton‐proton collisions is a possible mechanism to supply a secondary positron population with a low energy limit. We expect that pion production would occur in advection dominated accretion flows or ADAFs. In radiatively inefficient ADAFs the heat energy of the accreting gas is unable to radiate in less than the accretion time and the particle temperature could be high enough so that thermal protons can yield such pion production. Strong starbursts are another option for the injection of a truncated particle population into the jet. The role of both mechanisms is discussed with respect to the black hole spin estimate. The energy demanded to produce the pion decay process involves a minimum threshold for kinetic energy of the interacting protons. Therefore the mean proton speed in the flow can determine whether a LEC is generated. In ADAFs the random velocity of the protons can exceed the minimum speed limit of pion production around the jet launching region in the innermost part of the flow. Finally we summarize the additional work needed to put the model assumptions on a more rigorous basis. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evolution of non‐linear dynamics using Graphical Processing Units
Authors: Nagy‐Egri M.F. , Rácz I. , Debreczeni G.
Published: October 2014

A new Graphical Processing Unit (GPU) accelerated general lattice PDE solver and real‐time visualisation framework, called Gripper, is presented. Besides its scientific goals, the purpose of this project is to provide a publicly available, general purpose GPU enabled framework with visualisation capabilities. One of the application of this newly developed software, is aimed to provide valuable insight into non‐linear evolution of relativistic dynamical systems, such, as for example, neutron stars or black holes. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Weak and strong field approximations and circular orbits of the Kehagias‐Sfetsos space‐time
Authors: Dwornik M. , Horváth Zs. , Gergely L. Á.
Published: October 2014

The Kehagias‐Sfetsos asymptotically flat black hole and naked singularity solutions of the Hořava‐Lifshitz gravity are investigated both in the weak‐field and strong‐field regimes. In the weak‐field limit the gravitational field generated by the Kehagias‐Sfetsos spherically symmetric solution is weaker then in the case of the Schwarzschild black hole of general relativity. In the strong‐field regime naked singularities with ω0 ≪ 1 display an unusual distance dependence: gravity becomes weaker when approaching the singularity. The stability of circular orbits is also analyzed. While in the black hole case the square of the angular momentum should be larger than a certain finite, non‐zero minimal value, in the naked singularity case there are stable circular orbits for any non‐zero value of the angular momentum. In this regime we prove the existence of an infimum of the allowed radii of circular orbits (corresponding to vanishing angular momentum). (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lambda matter in the effective density dependent mean‐field model
Authors: Petrik K. , Gmuca S.
Published: October 2014

The density dependent relativistic hadron field (DDRHF) theory is introduced with various forms of the density dependence of the nuclear interaction to study the A matter in the β ‐equilibrium. Several new parametrizations are extracted from the Dirac‐Brueckner‐Hartree‐Fock (DBHF) calculations. We have compared and analysed high density extrapolations of A matter properties and shown that the choice of the density dependence has important effects on the structure of compact stars. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)