bluuebunny/crossref_metadata_2025 huggingface dataset:
The L dwarf/T dwarf transition: Multiplicity, magnetic activity and mineral meteorology across the hydrogen burning limit
Authors: Burgasser A.J.
Published: October 2014

The transition between the L dwarf and T dwarf spectral classes is one of the most remarkable along the stellar/brown dwarf main sequence, separating sources with photospheres containing mineral condensate clouds from those containing methane and ammonia gases. Unusual characteristics of this transition include a 1 µm brightening between late Land early T dwarfs observed in both parallax samples and coeval binaries; a spike in the multiplicity fraction; evidence of increased photometric variability, possibly arising from patchy cloud structures; and a delayed transition for young, planetary‐mass objects. All of these features can be explained if this transition is governed by the “rapid” (nonequlibrium) rainout of clouds from the photosphere, triggered by temperature, surface gravity, metallicity and (perhaps) rotational effects. While the underlying mechanism of this rainout remains under debate, the transition is now being exploited to discover and precisely characterize tight (<1 AU) very low‐mass binaries that can be used to test brown dwarf evolutionary and atmospheric theories, and resolved binaries that further constrain the properties of this remarkable transition. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Starspots and spin‐orbit alignment for Kepler cool host stars
Authors: Sanchis‐Ojeda R. , Winn J.N. , Fabrycky D.C.
Published: October 2014

The angle between the spin axis of the host star and the orbit of its planets (i.e., the stellar obliquity) is precious information about the formation and evolution of exoplanetary systems. Measurements of the Rossiter‐McLaughlin effect revealed that many stars that host a hot‐Jupiter have high obliquities, suggesting that hot‐Jupiter formation involves excitation of orbital inclinations. In this contribution we show how the passage of the planet over starspots can be used to measure the obliquity of exoplanetary systems. This technique is used to obtain – for the first time – the obliquity of a system with several planets that lie in a disk, Kepler‐30, with the result that the star has an obliquity smaller than 10 degrees. The implications for the formation of exoplanetary systems, in particular the hot‐Jupiter population, are also discussed. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determining distances using asteroseismic methods
Authors: Silva Aguirre V. , Casagrande L. , Basu S. , Campante T. L. , Chaplin W. J. , Huber D. , Miglio A. , Serenelli A. M. , KASC WG#1
Published: October 2014

Asteroseismology has been extremely successful in determining the properties of stars in different evolutionary stages with a remarkable level of precision. However, to fully exploit its potential, robust methods for estimating stellar parameters are required and independent verification of the results is needed. In this talk, I present a new technique developed to obtain stellar properties by coupling asteroseismic analysis with the infrared flux method. Using two global seismic observables and multi‐band photometry, the technique determines masses, radii, effective temperatures, bolometric fluxes, and thus distances for field stars in a self‐consistent manner. Applying our method to a sample of solar‐like oscillators in the Kepler field that have accurate Hipparcos parallaxes, we find agreement in our distance determinations to better than 5 %. Comparison with measurements of spectroscopic effective temperatures and interferometric radii also validate our results, and show that our technique can be applied to stars evolved beyond the main‐sequence phase. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Angular momentum evolution of cool stars: Toward a synthesis of observations and theory before and after the ZAMS
Authors: Meibom S. , Barnes S.A. , Covey K. , Jeffries R.D. , Matt S. , Morin J. , Palacios A. , Reiners A. , Sicilia‐Aguilar A. , Irwin J.
Published: October 2014

The coexistence of fast and slowly rotating cool stars in ZAMS clusters – forming distinct sequences in the color vs. rotation period plane – is providing clues to differences in their pre main‐sequence angular momentum evolution. This Cool Stars 17 splinter was dedicated to a discussion of new observational and theoretical results that may help discriminate between proposed mechanisms for early angular momentum regulation and help us explain the observed ZAMS dichotomy
Angular momentum evolution of low‐mass pre‐main sequence stars via extreme coronal mass ejections
Authors: Aarnio A.N. , Matt S.P. , Stassun K.G.
Published: October 2014

The angular momentum evolution of cool stars during the pre‐main sequence phase of stellar evolution remains a major outstanding problem. Multiple processes are likely involved in the transfer of mass and angular momentum within and out of the star+disk system. The role of coronal mass ejections (CMEs), energetic events which shed mass and magnetic flux in the Sun, has yet to be fully explored in the context of pre‐main sequence stars. It is well established that young, solar‐type stars exhibit X‐ray activity levels up to four orders of magnitude higher than the present‐day Sun, suggesting that CMEs associated with these extreme X‐ray flares could be an important process for expelling mass and angular momentum. We present a novel approach to modeling the CMEs of low‐mass pre‐main sequence stars that uses a solar‐calibrated CME model and observed X‐ray flare rates for young stars. We derive mass loss rates via stellar CMEs and calculate their attendant angular momentum losses during the pre‐main sequence phase. While we find the mass loss rates to be modest, ∼10 % of steady‐state stellar wind values from the literature, the angular momentum losses can be substantial, potentially counteracting the effects of initial stellar spin‐up due to contraction in tens of Myr. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Volatile and refractory abundances of F‐ and G‐type stars
Authors: González Hernández J.I. , Delgado‐Mena E. , Sousa S. G. , Israelian G. , Santos N.C. , Udry S.
Published: October 2014

We present a detailed chemical abundance analysis of a sample of F‐ and G‐type stars. We investigate the possibility that the presence of terrestrial planets could affect the volatile‐to‐refractory abundance ratios. Stars with and without planets exhibit very similar abundance behaviours, either for solar twins or even when considering the whole sample of 95 solar analogs, 33 with and 62 without detected planets, in the metallicity range –0.3 < [Fe/H] < 0.5. After removing the Galactic chemical evolution effects, the small differences in the abundance patterns of stars with and without planets practically disappear and the mean volatile‐to‐refractory abundance ratios of the two samples are very close to solar values. If the depletion signature depends on the size of the convective zone, then stars hotter than the Sun should, in principle, show enhanced volatile‐to‐refractory abundance differences. Thus, we have also selected a sample of late F‐ and early G‐type main‐sequence stars with high‐quality spectra. We have in total 29 planet‐host stars and 32 stars without planets in the Teff range 5950–6400 K. We find very accurate Galactic chemical trends of these hotter stars that match those of solar analogs. Finally, we compare the abundance ratios of volatile and refractory elements versus the condensation temperature of this sample of main‐sequence stars hotter than the Sun with respect to those of solar analogs, paying special attention to those stars containing super‐Earth‐like planets. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Radii and temperatures of cool stars with interferometry
Authors: Boyajian T.S.
Published: October 2014

This proceeding reviews the results of our survey to measure the fundamental properties of nearby, main‐sequence, K– and M–type stars, specifically reported in Boyajian et al. (2012a). The results presented double the number of precise measurements obtained for stars of this type. We use observations of the stellar angular diameter obtained through interferometry coupled with the distance and bolometric flux to determine the stellar linear radius, effective temperature, and luminosity. These data are used to derive empirical relations to the fundamental properties of stars. We highlight the challenges these data bring to current stellar atmospheric and evolutionary models. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constraining the core‐rotation rate in red‐giant stars from Kepler space photometry
Authors: Beck P.G. , De Ridder J. , Aerts C. , Kallinger T. , Hekker S. , García R.A. , Mosser B. , Davies G.R.
Published: October 2014

Rotation plays a key role in stellar structure and its evolution. Through transport processes which induce rotational mixing of chemical species and the redistribution of angular momentum, internal stellar rotation influences the evolutionary tracks in the Hertzsprung‐Russell diagram. In turn, evolution influences the rotational properties. Therefore, information on the rotational properties of the deep interior would help to better understand the stellar evolution. However, as the internal rotational profile cannot be measured directly, it remains a major unknown leaving this important aspect of models unconstrained. We can test for nonrigid rotation inside the stars with asteroseismology. Through the effect of rotational splitting of non‐radial oscillation modes, we investigate the internal rotation profile indirectly. Red giants have very slow rotation rates leading to a rotational splitting on the level of a few tenth of a μHz. Only from more than 1.5 years of consecutive data from the NASA Kepler space telescope, these tiny variations could be resolved. A qualitative comparison to theoretical models allowed constraining the core‐to‐surface rotation rate for some of these evolved stars. In this paper, we report on the first results of a large sample study of splitting of individual dipole modes (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the surface structure of sunspots
Authors: Franz M.
Published: October 2014

A precise knowledge of the surface structure of sunspots is essential to construct adequate input models for helioseismic inversion tools. We summarize our recent findings about the velocity and magnetic field in and around sunspots using HINODE observation. To this end we quantize the horizontal and vertical component of the penumbral velocity field at different levels of precision and study the moat flow around sunspot. Furthermore, we find that a significant amount of the penumbral magnetic fields return below the surface within the penumbra. Finally, we explain why the related opposite polarity signals remain hidden in magnetograms constructed from measurements with limited spectral resolution (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Brite‐Constellation: A status report
Authors: Kaiser A. , Kuschnig R. , Weiss W.W. , BRITE‐Constellation team
Published: October 2014

The BRITE‐Constellation, short for “BRIght Target Explorer” Constellation, is a group of six nanosatellites from Austria, Poland and Canada carrying thirty millimeter aperture optical telescopes with a CCD camera. The goal of the mission is to photometrically measure low‐level oscillations and temperature variations of the brightest stars in the sky down to a visual magnitude of 4.0, with unprecedented precision and time coverage not achievable from ground in two colors. The improved three‐axis pointing performance which is a critical element that makes this high precision photometry mission feasible is a recent development by the University of Toronto’s Space Flight Laboratory. The University of Vienna and the FFG/ALR (Austria’s space agency) are financing the development of two satellites. The Polish Academy of Sciences is funding two additional satellites as well as the Canadian Space Agency resulting in six components for the constellation (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
EXOTIME: Searching for planets and measuring $ \dot P $ in sdB pulsators
Authors: Lutz R. , Schuh S. , Silvotti R.
Published: October 2014

We review the status of the EXOTIME project (EXOplanet search with the TIming MEthod). The two main goals of EXOTIME are to search for sub‐stellar companions to sdB stars in wide orbits, and to measure the secular variation of the pulsation periods, which are related to the evolutionary change of the stellar structure. Now, after four years of dense monitoring, we start to see some results and present the brown dwarf and exoplanet candidates V1636 Ori b and DW Lynb (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Presentation of the reduction pipeline of the SONG échelle spectrograph
Authors: Triviño A. , Uytterhoeven K. , Grundahl F. , Pallé P.L. , the SONG team
Published: October 2014

We give an overview of the spectral reduction pipeline that will be used to process the data of the échelle spectrograph of the SONG‐OT telescope node of the SONG (Stellar Observations Network Group) network on Tenerife. In particular, we focus on the iodine absorption cell technique to derive precise radial velocity measurements. The telescope and dome of SONG‐OT were installed on 23 April 2012, and first light is foreseen this autumn. The reduction pipeline will be tested, optimized and improved when real stellar data will become available (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ground‐based photometric support for the CoRoT mission by the CoRoT‐Hungarian Asteroseismology Group
Authors: Bognár Zs. , Paparó M.
Published: October 2014

The CoRoT–Hungarian Asteroseismology Group was established in 2005 and joined the preparatory work of the CoRoT Mission via an ESA PECS project. After the successful launch of the telescope, we have continued our work of groundbased multi‐colour photometric observations and contributed to the analyses of CoRoT data. Our observations were focused on δ Scuti, γ Doradus, and RR Lyrae stars. The follow‐up of some selected targets’ pulsations in different wavelengths has provided valuable information for mode identification. We provided additional support by the confirmation of relatively faint variables’ spectral types. We proved that our ground‐based observations can help in the interpretation of a target with a contaminated CoRoT light curve. In this paper, we summarize our most important results of the photometric support for the CoRoT Mission (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
RR Lyrae stars seen from space
Authors: Guggenberger E.
Published: October 2014

RR Lyrae stars for a long time had the reputation of being rather simple pulsators, but the advent of high‐precision space photometry has meanwhile changed this picture dramatically. This article summarizes the results obtained for two remarkable Blazhko RR Lyrae stars and discusses how our view of RR Lyrae stars has changed since the availability of ultra‐precise satellite photometry as it is obtained by CoRoT and Kepler. Both stars, CoRoT 105288363 and V445 Lyrae, show a multitude of phenomena that were impossible to observe from the ground, either because of the small amplitude of the effect, or because uninterrupted long‐term monitoring was required for a detection. Not only was it found that strong and irregular cycle‐to‐cycle changes of the Blazhko effect can occur, and that seemingly chaotic phenomena need to be accounted for when modeling the Blazhko effect, but also a rich spectrum of low‐amplitude frequencies was detected in addition to the fundamental radial pulsation in RRab stars. The so‐called period doubling phenomenon, higher radial overtones and possibly also non‐radial modes make RR Lyrae stars more multifaceted than previously thought. This article presents the various aspects of irregularity of the Blazhko effect, questioning its long‐standing definition as a “periodic modulation”, and also discusses the low‐amplitude pulsation signatures that had been hidden in the noise of observations for centuries (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New results in RR Lyrae modeling: Convective cycles, additional modes and more
Authors: Molnár L. , Kolláth Z. , Szabó R. , Plachy E.
Published: October 2014

Recent theoretical and observational findings breathed new life into the field of RRLyrae stars. The ever more precise and complete measurements of the space asteroseismology missions revealed new details, such as the period doubling and the presence of the additional modes in the stars. Theoretical work also flourished: period doubling was explained and an additional mode has been detected in hydrodynamic models as well. Although the most intriguing mystery, the Blazhko‐effect has remained unsolved, new findings indicate that the convective cycle model can be effectively ruled out for short‐ and medium‐period modulations. On the other hand, the plausibility of the radial resonance model is increasing, as more and more resonances are detected both in models and stars (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Red giant oscillations: Stellar models and mode frequency calculations
Authors: Jendreieck A. , Weiss A. , Silva Aguirre V. , Christensen‐Dalsgaard J. , Handberg R. , Ruchti G. , Jiang C. , Thygesen A.
Published: October 2014

We present preliminary results on modelling KIC 7693833, the so far most metal‐poor red giant star observed by Kepler. From time series spanning several months, global oscillation parameters and individual frequencies were obtained and compared to theoretical calculations. Evolution models are calculated taking into account spectroscopic and asteroseismic constraints. The oscillation frequencies of the models were computed and compared to the Kepler data. In the range of mass computed, there is no preferred model, giving an uncertainty of about 30 K in Teff, 0.02 dex in log g, 0.7R⊙ in radius, and of about 2.5 Gyrs in age (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Seismic comparison of the 11‐ and 2‐year cycle signatures in the Sun
Authors: Simoniello R. , Jain K. , Tripathy S.C. , Turck‐Chiéze S. , Finsterle W. , Roth M.
Published: October 2014

The solar magnetic activity consists of two periodic components: the main cycle with a period of 11 yr and a shorter cycle with a period of ≈2 yr. The origin of this second periodicity is still not well understood. We use almost 15 years of long high‐quality resolved data provided by the Global Oscillation Network Group (GONG) to investigate the solar cycle changes in p‐mode oscillations with spherical degree Ł = 0–120 and in the range of 1600 µHz ≤ ν ≤ 3500 µHz. For both periodic components of solar magnetic activity our findings locate the origin of the frequency shift in the subsurface layers with a sudden enhancement in the amplitude of the shift in the last few hundred kilometers. We also show that the size of the shift increases towards equatorial latitudes and from minimum to maximum of solar activity. On the other hand, the signatures of the 2‐yr cycle differ from the one of the 11‐yr cycle in the magnitude of the shift, as the 2‐yr cycle causes a weaker shift in mode frequencies and a slower enhancement in the last few hundred kilometers. Based on these findings we speculate that a possible physical mechanism behind the quasi biennial periodicity (QBP) could be the beating between different dynamo modes (dipole and quadrupole mode) (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Measuring the solar meridional flow from perturbations of eigenfunctions of global oscillations
Authors: Schad A. , Timmer J. , Roth M.
Published: October 2014

We present a new concept to infer the meridional flow in the deep solar interior from global oscillation data. This concept is based on the estimation of the coupling strengths of p‐mode eigenfunctions mediated by the meridional flow. We illustrate the performance of the method using simulations and present first inversion results of a large‐scale flow component of the meridional flow obtained from MDI data (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hydrodynamical comparison test of solar models
Authors: Bach K. , Kim Y.‐C.
Published: October 2014

We present three dimensional radiation‐hydrodynamical (RHD) simulations for solar surface convection based on three most recent solar mixtures: Grevesse & Sauval (1998), Asplund, Grevesse & Sauval (2005), and Asplund, Grevesse, Sauval & Scott (2009). The outer convection zone of the Sun is an extremely turbulent region composed of partly ionized compressible gases at high temperature. The super‐adiabatic layer (SAL) is the transition region where the transport of energy changes drastically from convection to radiation. In order to describe physical processes accurately, a realistic treatment of radiation should be considered as well as convection. However, newly updated solar mixtures that are established from radiation‐hydrodynamics do not generate properly internal structures estimated by helioseismology. In order to address this fundamental problem, solar models are constructed consistently based on each mixture and used as initial configurations for radiation‐hydrodynamical simulations. From our simulations, we find that the turbulent flows in each model are statistically similar in the SAL (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asteroseismology and magnetic cycles
Authors: Santos A.R.G. , Cunha M.S. , Lima J.J.G.
Published: October 2014

Small cyclic variations in the frequencies of acoustic modes are expected to be a common phenomenon in solar‐like pulsators, as a result of stellar magnetic activity cycles. The frequency variations observed throughout the solar and stellar cycles contain information about structural changes that take place inside the stars as well as about variations in magnetic field structure and intensity. The task of inferring and disentangling that information is, however, not a trivial one. In the sun and solar‐like pulsators, the direct effect of the magnetic field on the oscillations might be significantly important in regions of strong magnetic field (such as solar/stellar spots), where the Lorentz force can be comparable to the gas‐pressure gradient. Our aim is to determine the sun‐/starspot effect on the oscillation frequencies and attempt to understand if this effect contributes strongly to the frequency changes observed along the magnetic cycle. The total contribution of the spots to the frequency shifts results from a combination of direct and indirect effects of the magnetic field on the oscillations. In this first work we considered only the indirect effect associated with changes in the stratification within the starspot. Based on the solution of the wave equation and the variational principal we estimated the impact of these stratification changes on the oscillation frequencies of global modes in the sun and found that the induced frequency shifts are about two orders of magnitude smaller than the frequency shifts observed over the solar cycle (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constraints on stellar parameters of the slowly pulsating B star HD 182255 from complex asteroseismology
Authors: Walczak P. , Szewczuk W. , Daszyńska‐Daszkiewicz J.
Published: October 2014

Seismic modeling of the slowly pulsating B‐type star HD182255 yields strong constraints on the radial orders of the two dominant modes. For these frequencies, we derive also the empirical values of the complex nonadiabatic parameter f. These two seismic tools, i.e., pulsational frequencies and the associated values of f, allow to test available opacity data, chemical composition, and overshooting effciency (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Solar rotation effect on the measurement of sub‐photospheric flows at high latitudes in a synoptic view using ring diagram analysis
Authors: Zaatri A.
Published: October 2014

The dense‐pack grid is commonly used to get a synoptic view of the sub‐photospheric dynamics when using ring diagram analysis (Haber et al 2002). This grid is based on a fixed distribution of patches in central meridian distance (cmd) at all latitudes. A shortcoming of the dense‐pack grid is that the true motion of tracked areas at slower rotating latitudes is not handled correctly. For instance, a 15° × 15° area, centered at a cmd of 0° and a latitude of 60°, that rotates only 12° in 1664 minutes (ring day), is considered tobe centered at cmd = 15° in the subsequent ring day. In order to avoid this issue, another distribution is suggested where the grid point in central meridian distance is latitude dependant (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The spectroscopic orbit of the K‐giant binary γ Canis Minoris
Authors: Fekel F. C. , Wiliamson M. H. , Weber M. , Strassmeier K. G. , Pourbaix D.
Published: October 2014

We have determined an improved orbit for the bright, evolved, double lined binary γ Canis Minoris. The system has an orbital period of 389.31 days and an eccentricity of 0.2586. We have revised the secondary to primary mass ratio to 0.987. The spectral types of the primary and secondary are K4 III and K1: III, respectively, and the components have a V magnitude difference of 2.2. Orbital fits to the Hipparcos astrometry are not definitive, but they suggest an orbital inclination of ∼ 66°, which produces masses of 1.88 and 1.85 M⊙ for the components. A comparison with evolutionary tracks results in an age of 1.3 Gyr. STELLA very low amplitude radial velocity residuals of the secondary indicate a period of 278 days. We interpret this as the rotation period of the secondary, detectable because of star spots rotating in and out of view. This period is nearly identical to the pseudosynchronous rotation period of the star. The primary is rotating more slowly than its pseudosynchronous rate. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homogenized effective temperatures for metal deficient stars from stellar catalogues
Authors: Malyuto V.
Published: October 2014

Homogeneous independent subsamples from selected catalogues and libraries of effective temperatures for metal deficient F–G stars are treated here by combining them in triples and pairs for the stars in common to determine their external errors from data intercomparisons. The effective temperatures are then averaged (with the weights inversely proportional to the squared errors) to produce mean homogenized catalogues which may be used for calibration of spectral and photometric data in large Galactic surveys. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Long‐term photometry of three active red giants in close binary systems: V2253 Oph, IT Com and IS Vir
Authors: Oláh K. , Moór A. , Strassmeier K.G. , Borkovits T. , Granzer T.
Published: October 2014

We present and analyze long‐term optical photometric measurements of the three active stars V2253 Oph, IT Com and IS Vir. All three systems are single‐lined spectroscopic binaries with an early K giant as primary component but in different stages of orbital‐rotational synchronization. Our photometry is supplemented by 2MASS and WISE near‐IR and mid‐IR magnitudes and then used to obtain more accurate effective temperatures and extinctions. For V2253 Oph and IT Com, we found their spectral energy distributions consistent with pure photospheric emission. For IS Vir, we detect a marginal mid‐IR excess which hints towards a dust disk. The orbital and rotational planes of IT Com appear tobe coplanar, contrary to previous findings in the literature. We apply a multiple frequency analysis technique to determine photometric periods, and possibly changes of periods, ranging from days to decades. New rotational periods of 21.55±0.03 d, 65.1±0.3 d, and 23.50±0.04 d were determined for V2253 Oph, IT Com, and IS Vir, respectively. Splitting of these periods led to tentative detections of differential surface rotations of δP/P ≈ 0.02 for V2253 Oph and 0.07 for IT Com. Using a time‐frequency technique based on short‐term Fourier transforms we present evidence of cyclic light variations of length ≈ 10 yr for V2253 Oph and 5–6 yr for IS Vir. A single flip‐flop event has been observed for IT Com of duration 2–3 yr. Its exchange of the dominant active longitude had happened close to a time of periastron passage, suggesting some response of the magnetic activity from the orbital dynamics. The 21.55‐d rotational modulation of V2253 Oph showed phase coherence also with the orbital period, which is 15 times longer than the rotational period, thus also indicating a tidal feedback with the stellar magnetic activity. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The “Sausage” and “Toothbrush” clusters of galaxies and the prospects of LOFAR observations of clusters of galaxies
Authors: Röttgering H. , van Weeren R. , Brüggen M. , Croston J. , Hoeft M. , Ogrean G. , Barthel P. , Best P. , Bonafede A. , Brunetti G. , Cassano R. , Chyży K. , Conway J. , De Gasperin F. , Ferrari C. , Heald G. , Jackson N. , Jarvis M. , Lehnert M. , Macario G. , Miley G. , Orrú E. , Pizzo R. , Rafferty D. , Stroe A. , Tasse C. , van der Tol S. , White G. , Wise M. , on behalf of the LOFAR collaboration
Published: October 2014

LOFAR, the Low Frequency Radio Array, is a new pan‐European radio telescope that is almost fully operational. One of its main drivers is to make deep images of the low frequency radio sky. To be able to do this a number of challenges need to be addressed. These include the high data rates, removal of radio frequency interference, calibration of the beams and correcting for the corrupting influence of the ionosphere. One of the key science goals is to study merger shocks, particle acceleration mechanisms and the structure of magnetic fields in nearby and distant merging clusters. Recent studies with the GMRT and WSRT radio telescopes of the “Sausage” and the “Toothbrush” clusters have given a very good demonstration of the power of radio observations to study merging clusters. Recently we discovered that both clusters contain relic and halo sources, large diffuse regions of radio emission not associated with individual galaxies. The 2 Mpc northern relic in the Sausage cluster displays highly aligned magnetic fields and and exhibits a strong spectral index gradient that is a consequence of cooling of the synchrotron emitting particles in the post‐shock region. We have argued that these observations provide strong evidence that shocks in merging clusters are capable of accelerating particles. For the Toothbrush cluster we observe a puzzling linear relic that extends over 2 Mpc. The proposed scenario is that a triplemerger can lead to such a structure. With LOFAR's sensitivity it will not only be possible to trace much weaker shocks, but also to study those shocks due to merging clusters up to redshifts of at least one. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Observing simulated galaxy clusters: The prospects of ICM velocity diagnostics
Authors: Biffi V. , Dolag K. , Böhringer H.
Published: October 2014

Non‐thermal motions in the intra‐cluster medium (ICM) are believed to play a non‐negligible role in the pressure support to the total gravitating mass of galaxy clusters. Future high‐precision X‐ray missions will allow us to directly detect the signature of these motions from highly resolved spectra of the ICM. With this perspective, we will present here a study on a set of clusters extracted from a cosmological hydrodynamical simulation, for which we simulated X‐ray observations and characterized them via the non‐thermal velocity amplitude of the ICM. We have applied the X‐ray virtual telescope PHOX to generate mock observations of the simulated clusters and estimated in an observational fashion global X‐ray properties. We included ICM non‐thermal motions as additional parameter to further identify non‐regular clusters. In particular, the influence of internal gas motions on the location of clusters in the LX‐T plane was investigated and was found that objects with the largest amount of non‐thermal velocity have on average higher X‐ray luminosities. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
X‐ray study of clusters at the outer edge and beyond
Authors: Ohashi T. , Akamatsu H. , Kawahara H. , Sekiya N. , Takei Y.
Published: October 2014

We report on recent Suzaku results on cluster outer regions. Relaxed clusters show a monotonous temperature decline to the virial radii, reaching 1/3 to 1/4 of the central levels. Significant temperature jumps have been confirmed for a number of radio relics, including A 3667, A 3376, and CIZA J2242.8+5301. This confirms that the radio relics generally correspond to shock fronts with the Mach numbers around 3. New filament junctions are identified by a new algorithm applied to the SDSS galaxy distribution and show significant X‐ray emission with Suzaku. The emission agrees with the LX‐kT relation for elliptical galaxies and galaxy groups, and the junctions can be a important baryon reservoir. We propose a small X‐ray mission DIOS (Diffuse Intergalactic Oxygen Surveyor), equipped with microcalorimeters with a wide field of view (∼50′), which will detect the emission from warm‐hot intergalactic medium (WHIM) and measure detailed thermal and dynamical properties of the gas accreting onto clusters from the filaments. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
X‐ray and optical substructures of the DAFT/FADA survey clusters
Authors: Guennou L. , Durret F. , Adami C. , Lima Neto G.B.
Published: October 2014

We have undertaken the DAFT/FADA survey with the double aim of setting constraints on dark energy based on weak lensing tomography and of obtaining homogeneous and high quality data for a sample of 91 massive clusters in the redshift range 0.4–0.9 for which there were HST archive data. We have analysed the XMM‐Newton data available for 42 of these clusters to derive their X‐ray temperatures and luminosities and search for substructures. Out of these, a spatial analysis was possible for 30 clusters, but only 23 had deep enough X‐ray data for a really robust analysis. This study was coupled with a dynamical analysis for the 26 clusters having at least 30 spectroscopic galaxy redshifts in the cluster range. Altogether, the X‐ray sample of 23 clusters and the optical sample of 26 clusters have 14 clusters in common. We present preliminary results on the coupled X‐ray and dynamical analyses of these 14 clusters. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Radio observations of Planck clusters
Authors: Kale R.
Published: October 2014

Recently, a number of new galaxy clusters have been detected by the ESA‐Planck satellite, the South Pole Telescope, and the Atacama Cosmology Telescope using the Sunyaev‐Zel'dovich effect. Several of the newly detected clusters are massive, merging systems with disturbed morphology in the X‐ray surface brightness. Diffuse radio sources in clusters, called giant radio halos and relics, are direct probes of cosmic rays and magnetic fields in the intra‐cluster medium. These radio sources are found to occur mainly in massive merging clusters. Thus, the new SZ‐discovered clusters are good candidates to search for new radio halos and relics. We have initiated radio observations of the clusters detected by Planck with the Giant Metrewave Radio Telescope. These observations have already led to the detection of a radio halo in PLCKG171.9–40.7, the first giant halo discovered in one of the new Planck clusters. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Scaling relations with a complete sample of galaxy groups
Authors: Lovisari L. , Reiprich T.H.
Published: October 2014

Galaxy clusters are an attractive tool to constrain cosmological parameters and well‐determined scaling relations between X‐ray observables and cluster mass give us a precious diagnostic to study the thermodynamical history of the intra‐cluster medium (ICM). We are in the process of improving the accuracy of scaling relations using a complete sample of galaxy groups to study if there is a systematic difference between clusters and groups and the influence of non‐gravitational physics on low‐mass systems. By combining this sample with the HIFLUGCS sample creates a master sample of 86 groups and clusters ranging over more than three orders of magnitude in luminosity. This large leverage will directly allow us to place tight constraints on cosmological parameters. We present here the results of an ongoing work in which we analyze a complete sample of galaxy groups from observations taken with XMM. The results are compared with the ones obtained using the HIFLUGCS sample. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The fundamental plane of clusters of galaxies
Authors: D'Onofrio M. , Bettoni D. , Bindoni D. , Cava A. , Fasano G. , Marziani P. , Moles M. , Moretti A. , Poggianti B.M. , Varela J.
Published: October 2014

We have analyzed the growth curves and the surface brightness light profiles of the clusters of the WINGS sample (Fasano et al. 2006) in the B and V bands, measuring the effective radii, the effective surface brightnesses and the total luminosities of our clusters. The similarly of the radial surface brightness profiles of early‐type galaxies (ETGs) and clusters indicate that within r200 almost all clusters are virialized structures. The total luminosities LB of clusters are found to correlate with the X‐ray luminosity LX, following approximately the same relation measured for galaxies by Eskridge et al. (1995). By coupling the photometric data with the central velocity dispersions, derived from the radial velocities of the galaxies measured by Cava et al. (2009), we were able to fit the fundamental plane (FP) of clusters of galaxies. We find that it has approximately the same slope of the FPs of early‐type galaxies (ETGs) and globular clusters (GCs), but differs from them in the zero‐point. This behavior can be easily explained in terms of a different contribution of dark matter (DM). (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
TheHerschel view of clusters of galaxies
Authors: Edge A.C. , Oonk J.B.R. , Mittal R.
Published: October 2014

Clusters of galaxies provide a rich variety of phenomena in the far‐infrared and the Herschel Space Observatory has performed a number of comprehensive imaging and spectroscopic observations of clusters over a wide redshift range. This talk gives an overview of the results available to date and the prospects for the observations yet to come. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The duty cycle of the radio mode feedback
Authors: Bîrzan L. , Rafferty D.A. , Nulsen P.E.J. , McNamara B.R. , Röttgering H.J.A. , Wise M.W.
Published: October 2014

The Chandra X‐ray Observatory has revealed X‐ray bubbles in the intracluster medium (ICM) of many nearby clusters, which are thought to be created by the central active galactic nucleus (AGN). However, the duty cycle of such AGN outbursts is not well understood. In order to further understand how cooling is balanced by bubble heating we studied complete samples of cooling flow clusters (from the Brightest 55 clusters of galaxies sample, B55, and the HIghest X‐ray FLUx Galaxy Cluster Sample, HIFLUGCS). We found that there is a radio luminosity cut‐off of 2.5×1030 erg s–1 Hz–1 for the cooling flow clusters. Furthermore, we find a duty cycle for radio mode feedback, the fraction of time that a system possesses bubbles inflated by its central radio source, of ≳ 69 % for the B55 sample and ≳ 63 % for the HIFLUGCS sample. These duty cycles are lower limits since some bubbles are likely missed in existing images. We used simulations to constrain the bubble power that might be present and remain undetected in the cooling flow systems without detected bubbles. Among theses systems, almost all could have significant bubble power. Therefore, our results imply that the duty cycle of AGN outbursts with the potential to heat the gas significantly in cooling flow clusters is at least 60% and could approach 100 %. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The origin of the chemical elements in cluster cores
Authors: de Plaa J.
Published: October 2014

Metals play a fundamental role in ICM cooling processes in cluster cores through the emission of spectral lines. But when and how were these metals formed and distributed through the ICM? The X‐ray band has the unique property of containing emission lines from all elements from carbon to zinc within the 0.1–10 keV band. Using XMM‐Newton, the abundances of about 11 elements are studied, which contain valuable information about their origin. Most elements were formed in type Ia and core‐collapse supernovae, which have very different chemical yields. Massive stars and AGB stars also contribute by providing most of the carbon and nitrogen in the ICM. Because feedback processes suppress star formation in the cluster centre, the element abundances allow us to directly probe the star formation history of the majority of stars that are thought to have formed between z = 2–3. The spatial distribution in the core and the evolution with redshift also provide information about how these elements are transported from the member galaxies to the ICM. I review the current progress in chemical enrichment studies of the ICM and give an outlook to the future opportunities provided by XMM‐Newton's successors, like Astro‐H. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Clusters of galaxies in the Planck survey
Authors: Pointecouteau E.
Published: October 2014

The Planck satellite has surveyed the whole sky more than four times. The nominal mission of two all‐sky surveys will be released to the public in 2013. From the first all‐sky survey, we have demonstrated the ability to detect clusters via the Sunyaev‐Zel'dovich effect with high reliability and out to large redshifts. We have released the first large sample of 189 high signal‐to‐noise SZ clusters. We also presented the detection of 45 new Planck clusters, confirmed in X‐ray with the XMM‐Newton satellite. The Planck collaboration is engaged in a massive identification and follow‐up programme of its SZ sources at X‐ray, optical, and SZ wavelengths. Dedicated cluster studies are also conducted by the consortium in order to better constrain the scaling and structural properties of the cluster population. We have thus provided high precision calibration of scaling relation between the SZ signal and the clusters physical quantities. The excellent agreement found between SZ and X‐ray measurements have demonstrated our good understanding of the hot intra‐cluster gas at least within R500. These results together with those from other operating SZ instruments are shading new light on our understanding of the most massive bound structure of the Universe. With its whole sky reach and unprecedented frequency coverage, the Planck mission is a crucial asset to these endeavours. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Detection and characterisation of the first Planck high‐z candidates
Authors: Flores‐Cacho I.
Published: October 2014

With its unprecedented ability to scrutinise the sub‐millimetre (sub‐mm) to centimetre full sky, the Planck satellite is uniquely suited to search for the progenitors of clusters of galaxies. The forming massive halos at z ≳1–2 are expected to host massive galaxies with high star formation rates. Clustered in the growing potential well that is being established, these galaxies are within Planck 's reach via their sub‐mm emission. We have applied a new colour‐based method combining Planck and IRAS data to detect the rarest and brightest sub‐mm cold sources on the sky. In this work, we describe the method and present the first confirmations of our high‐z candidates, particularly focusing on 17p732, a newly discovered high‐z (proto)cluster candidate at z ⋍ 1.7 for which we carried a multi‐wavelength follow‐up. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
CL0024+1652 as seen by the Galaxy Cluster Evolution survey (GLACE)
Authors: Pérez‐Martínez R. , ´Sanchez‐Portal M. , Pintos‐Castro I. , Pérez‐García A.M. , Cepa J. , the GLACE Team
Published: October 2014

The GaLAxy Cluster Evolution survey (GLACE) is aimed to study the evolution of emission line galaxies in clusters across the cosmic time. It takes advantage of the tunable filter mode of OSIRIS (first light instrument of GTC) to scan Hα /[N II], Hβ, [O II]3727 and [O III]5007 searching for star formation activity and AGNs in clusters in three different redshift windows (z ∼ 0.40, 0.63, and 0.86), providing a unique view of the evolution of cluster galaxies along such redshift range. Moreover, the OSIRIS large field of view (8×8 arcmin2) together with GTC large collective area (D ∼ 10 m) make it possible to detect SFR ∼ 2 M⊙ yr–1 in an angular area up to 2Rvir. We present here the first results of the program together with a brief description of this novel technique focusing in the cluster CL0024+1654 (z ∼ 0.39). (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The XMM Cluster Survey: Present status and latest results
Authors: Viana P.T.P. , Mehrtens N. , Harrison C.D. , Romer A.K. , Collins C.A. , Hilton M. , Hoyle B. , Kay S.T. , Liddle A.R. , Mayers J.A. , Miller C.J. , Rooney P.J. , Sahlén M. , Stott J.P.
Published: October 2014

The XMM Cluster Survey (XCS) is a serendipitous search for galaxy clusters using all publicly available data in the XMM‐Newton Science Archive. Our recent first data release (XCS‐DR1) contains 503 optically confirmed groups and clusters, among which 256 new to the literature and 357 whose X‐ray emission was detected for the first time. We discuss their properties and provide an update on the work being done. As examples of the applications of XCS‐DR1, we mention the 17 fossil groups/clusters identified with the help of the Sloan Digital Sky Survey. Their brightest galaxies have stellar populations and star‐formation histories which are similar to normal brightest cluster galaxies, but their stellar masses are significantly larger and correspond to a much bigger fraction of the total group/cluster optical luminosity. We also highlight the 15 clusters expected tobe also detected by the Planck satellite, and characterize the expected overlap between the final XCS and Planck cluster catalogues. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Distant clusters of galaxies in a deep XMM‐Newton observation
Authors: de Hoon A. , Lamer G. , Schwope A. , Mühlegger M. , Fassbender R. , Böhringer H. , Lerchster M. , Nastasi A. , Šuhada R. , Rosati P. , Pierini D. , Santos J.S. , Quintana H.
Published: October 2014

The XMM‐Newton Distant Cluster Project (XDCP) aims at the identification of a well defined sample of X‐ray selected clusters of galaxies at redshifts z ≥ 0.8. As part of this project, we analyse the deep archival XMM‐Newton exposure of LBQS 2212–1759 to quantify the cluster content. We validate the optical follow‐up strategy as well as the X‐ray selection function. We base the cluster identification of the extended X‐ray sources on deep imaging with the ESO‐VLT and on the CFHT‐LS. The confirmation of cluster candidates is done by VLT/FORS2 spectroscopy. Photometric redshifts from CFTH‐LS D4 are utilised to confirm the effectiveness of the X‐ray cluster selection method. The survey sensitivity is computed to have a flux limit of S0.5–2.0 keV ∼ 2.5×10–15 erg s–1 for 50% completeness in an area ∼0.13 deg2. We detect six clusters of galaxies above this level both in X‐rays and the optical. Two newly discovered X‐ray luminous clusters of galaxies in this work are at z ≥ 1.0 and one is at z = 0.41. The constructed log N ‐log S tends to favour a scenario where no evolution in the cluster X‐ray luminosity function takes place. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)