bluuebunny/crossref_metadata_2025_split huggingface dataset:
The magnetic field and its effects on the solar atmosphere in high resolution
Authors: Title Alan M. 
Published: December 2007

AbstractThe Sun's magnetic field is produced throughout the solar interior; it emerges and is dispersed by surface and subsurface flows, and then expands above the surface to dominate the structure of the corona. To resolve the effects of the magnetic field it is necessary to image the interior and measure its rotation and flow systems; track the responses of the magnetic fields to flows in the surface; and to follow the evolution of structures in the corona. Because the Sun is dynamic both high spatial and temporal resolution are essential. Because the Sun's magnetic field effects encompass the entire spherical exterior, the entire surface and outer atmosphere must be mapped. And because the magnetic field is cyclic high-resolution observations must be maintained over multiple cycles.
Evidence for solar shock production of heliospheric near-relativistic and relativistic electron events
Authors: Kahler Stephen W. 
Published: December 2007

AbstractProperties of near-relativistic (E ≳ 30 keV, NR) and relativistic (E ≳ 0.3 MeV) electron events produced near the Sun and observed within 1 AU are reviewed. Observations suggest the CME-driven shocks are the sources of many events, but flares are often sources for NR events.
Radio and X-ray diagnostics of electrons accelerated in solar flares
Authors: Bárta Miroslav , Karlický Marian 
Published: December 2007

AbstractStarting from 2.5D MHD modelling of solar flares on a global scale we calculate (using the PIC and test-particle simulations) the radio and X-ray emissions generated in solar flare reconnection. Our results – the radio and X-ray spectra and brightness distributions, and their dynamics – are directly comparable with observations providing thus a test of particle acceleration models as well as of the ‘standard’ global flare scenario.
Stochastic re-acceleration in the ICM
Authors: Brunetti Gianfranco , Lazarian Alex 
Published: December 2007

AbstractHere we suggest that efficient stochastic particle re–acceleration in galaxy clusters may be driven by compressible modes. The damping of these modes is severely dominated by the TTD–resonance with thermal electrons and protons in the ICM. However, a small energy flux of these modes may be channelled into particle re-acceleration and this gives re-acceleration times of the order of ∼ 108 yrs, sufficient to mantain GeV radiating electrons in the ICM.
Joint Discussion 3 Solar active regions and 3D magnetic structure
Authors: Choudhary Debi Prasad , Sobotka Michal 
Published: December 2007

AbstractKeeping in view of the modern powerful observing tools, among othersHinode(formerlySOLAR-B),STEREOand Frequency-Agile Solar Radiotelescope, and sophisticated modelling techniques, Joint Discussion 3 during the IAU General Assembly 2006 focused on the properties of magnetic field of solar active regions starting in deep interior of the Sun, from where they buoyantly rise to the coronal heights where the site of most explosive events are located. Intimately related with the active regions, the origin and evolution of the magnetic field of quiet Sun, the large scale chromospheric structures were also the focal point of the Joint Discussion. The theoretical modelling of the generation and dynamics of magnetic field in solar convective zone show that the interaction of the magnetic field with the Coriolis force and helical turbulent convection results in the tilts and twists in the emerging flux. In the photosphere, some of these fluxes appear in sunspots with field strengths up to about 6100 G. Spectro-polarimetric measurements reveal that the line of sight velocities and magnetic field of these locations are found to be uncombed and depend on depth in the atmosphere and exhibit gradients or discontinuities. The inclined magnetic fields beyond penumbra appear as moving magnetic features that do not rise above upper photospheric heights. As the flux rises, the solar chromosphere is the most immediate and intermediary layer where competitive magnetic forces begin to dominate their thermodynamic counterparts. The magnetic field at these heights is now measured using several diagnostic lines such as CaII854.2 nm, HI656.3 nm, and HeI1083.0 nm. The radio observations show that the coronal magnetic field of post flare loops are of the order of 30 G, which might represent the force-free magnetic state of active region in the corona. The temperatures at these coronal heights, derived from the line widths, are in the range from 2.4 to 3.7 million degree. The same line profile measurements indicate the existence of asymmetric flows in the corona. The theoretical extrapolation of photospheric field into coronal heights and their comparison with the observations show that there exists a complex topology with separatrices associated to coronal null points. The interaction of these structures often lead to flares and coronal mass ejections. The current MHD modelling of active region field shows that for coronal mass ejection both local active region magnetic field and global magnetic field due to the surrounding magnetic flux are important. Here, we present an extended summary of the papers presented in Joint Discussion 03 and open questions related to the solar magnetic field that are likely to be the prime issue with the modern observing facilities such asHinodeandSTEREOmissions.
Continuum-driven versus line-driven mass loss and the Eddington limit
Authors: Owocki Stanley P. 
Published: December 2007

AbstractBasic stellar structure dictates that stars of ∼ 100 M⊙ or more will be close to the Eddington limit, with luminosities in excess of 106 L⊙, and radiation pressure contributing prominently to the support against gravity. Although it is formally possible to generate static structure models of even more massive stars, recent studies of dense clusters show there is a sharp cutoff at masses above ∼ 150 M⊙. This talk examines the role of extreme mass loss is limiting the masses of stars, emphasizing in particular that continuum driving, possibly associated with structural instabilities of radiation dominated envelope, can lead to much stronger mass loss than is possible by the usual line-scattering mechanism of steady stellar winds.However, population studies of very young, dense stellar clusters now suggest quite strongly that there is a sharp cutoff at masses above ca. 150 M⊙ (see, e.g., the talk by Sally Oey, in this JD 05, p. 206). This is sometimes attributed to a mass limit on star formation by accretion processes, though there are competing formation scenarios by binary or cluster merging that would seem likely to lead to formation of even higher mass stars (see talks in JD14 and S237).So given the above rough coincidence of the observational upper mass limit with the Eddington-limit domain of radiation-pressure dominance, it seems associated instabilities in stellar structure might actually be a more important factor in this upper mass limit, leading to extreme mass loss in LBV and/or giant eruption events, much as inferred from circumstellar nebulae observed around high mass stars like eta Carinae and the Pistol star.
The end of the re-ionization epoch probed by Lyα emitters at z = 6.5
Authors: Kashikawa Nobunari 
Published: December 2007

AbstractWe report an extensive search for Lyα emitters (LAEs) at z = 6.5 in the Subaru Deep Field (SDF). We carried out spectroscopic observations with Subaru/Keck to identify LAEs at z = 6.5 that were selected by narrow-band excess at 920nm. We have identified eight new LAEs based on their significantly asymmetric Lyα emission profiles. This increases the sample of spectroscopically confirmed z = 6.5 LAEs in the SDF to 17. Based on this spectroscopic sample of 17, complemented by a photometric sample of 58 LAEs, we have derived a more accurate Lyα luminosity function (LF) of LAEs at z = 6.5, which reveals an apparent deficit at the bright end, of ∼0.75 mag fainter L*, compared with that observed at z = 5.7. The difference has 3σ significance, which is reduced to 2σ when cosmic variance is taken into account. Several LAEs with high Lyα luminosity have been actually identified by spectroscopy at z<5.7, while our LAE sample at z = 6.5 has no confirmed object having such a high Lyα luminosity. The LF of the rest UV continuum, which is not sensitive to neutral IGM, of our LAE sample has almost the same as those of LAEs at z = 5.7 and i-dropouts at z≃6, even at their bright ends. This result may imply that the reionization of the universe has not been completed at z = 6.5. The decline of the Lyα LF implies the cosmic neutral fraction xHI=0.45 based on a theoretical IGM model, although this predicted value is strongly model dependent. The spatial distribution of our LAE sample was found to be homogeneous over the field, based on three independent methods to quantify the clustering strength. The composite spectrum of our LAE sample clearly reveals an asymmetric Lyα profile with an extended red wing, which can be explained by either a galactic wind model composed of double Gaussian profiles, or by a reionization model expected from the damping wing profile. Although our result has uncertainties in LAE evolution and large cosmic variance, it can be interpreted that LAEs at z = 6.5 are at the end of the reionization epoch.
Metallicity and black hole masses of z≃6 quasars
Authors: Kurk Jaron D. , Walter Fabian , Riechers Dominik , Rix Hans-Walter , Wagner Stefan , Pentericci Laura , Fan Xiaohui 
Published: December 2007

AbstractWe present NIR spectroscopy of emission lines of a sample of five z≃6 quasars, including fainter objects than observed before. The measured FeII/MgII ratios are around solar and consistent with a lack of evolution of the metallicity of quasar BLRs up to z≃6, suggesting that stars in their hosts formed at z≫6. The BH masses, measured from both MgII and CIV line widths are within the range 2-16×108M⊙, the smallest found in such distant objects.
Constraints on Very Faint High-z Quasars
Authors: Dijkstra Mark 
Published: December 2007

AbstractI discuss the constraints that can be derived on the abundance of high redshift (z>6) (mini)quasars from the unresolved soft X-Ray background. Furthermore, I will show how existing Lyα surveys can be used to probe the very faint MB≳-21 mag (i.e., ≳7–8 mag fainter than the SDSS quasars) end of the z≥,4.5 quasar luminosity function.
The first galaxies at cm and mm wavelengths
Authors: Walter Fabian , Carilli Chris L. , Bertoldi Frank , Cox Pierre , Menten Karl M. 
Published: December 2007

AbstractObservations of the most distant (z≃6) QSOs in the centimetre and millimetre regime currently serve as the only direct probe of the host galaxies of these extreme systems in the Epoch of Re-ionization. Such observations reveal that about 1'3 of the hosts contain massive reservoirs of dust (>108M⊙) and molecular gas (>1010M⊙) – the fuel for galaxy formation, and also indicate coeval starbursts at a rate >103M⊙yr−1 adequate to form a large elliptical galaxy in a dynamical timescale. These data imply that a highly metal enriched, molecular ISM, can be generated in galaxies within 870 Myr of the Big Bang. High-resolution imaging of the gas also provide an estimate of the host galaxy dynamical mass. However, current observations are restricted to rare, hyper-luminous IR galaxies. I will close by considering the prospects of observing the gas, dust, and star formation in the first ‘normal’ galaxies (e.g., the Ly-α galaxies) into cosmic reionization (z>6), using ALMA and the EVLA.
Additional sources of ionization in the early universe and the 21cm line
Authors: Vasiliev Evgenii O. , Shchekinov Yuri A. 
Published: December 2007

AbstractWe consider the influence of decaying dark matter particles and ultra-high energy cosmic rays (UHECRs) on the ability of neutral gas at redshifts z = 10-50 to emit and absorb in the 21cm line. We show that the signal in 21 cm is sensitive to properties of decaying particles and UHECRs, and conclude that future radio telescopes (LOFAR, LWA and SKA) are able not only to detect 21cm signal originated from decaying particles and UHECRs, but discriminate between them as well.
Assessing the influence of metallicity on fragmentation of proto-galactic gas
Authors: Jappsen Anne-Katharina , Glover Simon C. O. , Klessen Ralf S. , Low Mordecai-Mark Mac 
Published: December 2007

AbstractIn cold dark matter cosmological models, the first stars to form are believed to do so within small protogalaxies. We study the influence of low levels of metal enrichment on the cooling and collapse of ionized gas in these protogalactic halos using three-dimensional, smoothed particle hydrodynamics simulations.
Large-scale patterns, complexes of solar activity and ‘active longitudes’
Authors: Ambrož Pavel 
Published: December 2007

AbstractTypical latitude zones and longitude sectors with a dominant occurrence of newly emerging magnetic flux were systematically detected during three last activity cycles. Two long time persistent longitude sectors with the preferred occurrence of a new strong magnetic flux are characteristic for magnetic flux distribution and their rotation rate is latitude dependent in the relationship with differential rotation rate. Recent new information about the large-scale flows in convection zone relates to a concept of the expected giant cells and jets and show a new relationship with different scales of the large-scale circulation. Non-axially symmetric horizontal flow in upper part of convection zone gives a good motivation for an extension of the existing axially symmetric 2D models into new 3D concept.
Cyclic fluctuations in the differential rotation of active stars
Authors: Petit Pascal 
Published: December 2007

AbstractDifferential rotation is described in stellar dynamo models as one of the fundamental phenomena governing the amplification of magnetic fields in active stars.Using indirect imaging methods, the measurement of photospheric differential rotation is now achieved on a growing number of very active stars, a fraction of which exhibit temporal fluctuations of potentially large amplitude in their latitudinal shear, on a time-scale of a few years. I first describe the modeling tools on which such analysis is based, then discuss the implications of this observational work on our understanding of stellar dynamos and of the impact stellar magnetic fields may have on the dynamics of convective envelopes.
Topology of stellar coronae
Authors: Jardine Moira M. 
Published: December 2007

AbstractWhile the existence of cycles in stellar chromospheric flux has been known for some time, the nature of the corresponding coronal response has been more elusive. We describe recent results on the relationship between cyclic variations in surface magnetic flux and coronal structure and re-assess the role of prominence observations in understanding the topology of stellar coronas. We present a new paradigm for prominence support which allows for extended prominences to co-exist with a compact corona. We discuss briefly the recent results on coronal structure in high- and low-mass stars and their implications for dynamo theory.
The impact of stellar activity on planets
Authors: Ribas Ignasi 
Published: December 2007

AbstractThe results of the Sun in Time program indicate that the X ray, far ultraviolet and ultraviolet fluxes of the young Sun were significantly higher than today. Similarly, the solar wind mayhave been much stronger in the past. Such environment of intense energy and particle emissions could have influenced the paleo-atmospheres of Solar System planets and, by extension, the habitability and stability of exoplanets.
Future facilities for solar and stellar activity research
Authors: Strassmeier Klaus G. 
Published: December 2007

AbstractI try to list the currently ongoing instrumental activities for solar and stellar activity research. Only projects that lead to operational ground-based facilities no later than 2013 and to operational space-based observatories no later than 2016 are considered. Any facility already in operation or any instrument under construction but with a very wide range of usage is excluded from this listing (like e.g. ALMA, Herschel or SOFIA). No details on science programs are given. The text is organized according to space, radio, and optical/IR projects.
SN 1006: a thousand-year perspective
Authors: Winkler P. Frank 
Published: December 2007

AbstractWe review some of the extensive historical observations of SN 1006, emphasizing estimates of its brightness at maximum. An estimate of Vmax ≈ −7.5 is consistent with what may be the most reasonable interpretation of these records and with an a posteriori calculation based on typical peak magnitudes for Type Ia supernovae together with the distance and extinction to SN 1006. We also give a brief overview of the discovery of the SN 1006 remnant in 1965, and contrast the earliest radio, optical, and X-ray observations of the remnant with recent ones, as reported in more detail by other papers in this JD09 review.
SN 1006 and other historical supernovae
Authors: Stephenson F. Richard 
Published: December 2007

AbstractThe supernova which appeared in AD 1006 is unique in history for its brilliance, duration of visibility, and the interest it aroused. Almost thirty separate records of the star are preserved from various parts of the world. This paper briefly summarizes historical records of SN 1006 and discusses the prospects of uncovering further historical records of supernovae.
On the road to consistent Type Ia supernova explosion models
Authors: Röpke Friedrich K. 
Published: December 2007

AbstractKeeping up with ever more detailed observations, Type Ia supernova (SN Ia) explosion models have seen a brisk development over the past years. The aim is to construct a self-consistent picture of the physical processes in order to gain the predictive power necessary to answer questions arising from the application of SNe Ia as cosmological distance indicators. We review recent developments in modeling these objects focusing on three-dimensional simulations.
Light echoes of SNe in the LMC
Authors: Rest Armin , Suntzeff Nicholas B. , Smith R. Chris , Olsen Knut , Zenteno Alfredo , Damke Guillermo J. , Prieto Jose L. , Stubbs Christopher , Garg Arti , Challis Peter , Becker Andrew C. , Miknaitis Gajus A. , Miceli Antonino , Welch Douglss L. , Clocchiatti Alejandro , Minniti Dante , Morelli Lorenzo , Cook Kem H. , Nikolaev Sergei , Huber Mark E. , Newman Andrew 
Published: December 2007

AbstractThe SuperMACHO project has discovered light echoes from 3 ancient SNe in the LMC. These SNRs are three of the six youngest in the LMC, and are classified as likely SN Ia based on X-ray data.
The Long Wavelength Array
Authors: Taylor Gregory B. 
Published: December 2007

AbstractThe Long Wavelength Array (LWA) will be a new, open, user-oriented astronomical instrument operating in the relatively unexplored window from 20–80 MHz near arcsecond angular resolution and milliJansky sensitivity. Operated by the University of New Mexico on behalf of the Southwest Consortium (SWC) the LWA will provide a unique training ground for the next generation of radio astronomers. Students may also put skills learned on the LWA to work in computer science, electrical engineering, and the communications industry, among others. The development of the LWA will follow a phased build which benefits from lessons learned at each phase. Four university-based Scientific Testing and Evaluation (ST&E) teams with different areas of concentration: (i) high-resolution imaging and particle acceleration; (ii) wide-field imaging and large scale structures; (iii) ionospheric physics; and (iv) radio frequency interference (RFI) suppression and transient detection will provide the feedback needed to assure that science objectives are met as the build develops. Currently in its first year of construction funding, the LWA team is working on the design for the first station (see also Ray et al. 2006).
N-body codes
Authors: Aarseth Sverre J. 
Published: December 2007

AbstractWe review some advances relating to direct N-body codes. In particular, there has been significant progress in dealing with large-N systems containing a few dominant members. The simulation of massive black holes also requires treatment of relativistic effects for strongly bound two-body orbits. Although somewhat costly, the addition of post-Newtonian terms is still straightforward when used in connection with regularization methods. Several versions of multiple regularization are especially well suited to studying black hole problems. We also report on a new stability criterion for the general three-body problem which will provide a robust test in systems where hierarchies are a troublesome feature, as in the case of star cluster simulations with primordial binaries.
Pulsar as barycenter coordinate clock
Authors: Ilyasov Yuri P. , Kopeikin S. M. , Sazhin Mikhail V. , Zharov Vladimir E. 
Published: December 2007

AbstractPulsars can be considered as very precise clocks if they are observed from the barycenter of the Solar system. Pulsar Timing Array (PTA) can be used to establish new astronomical reference frame which describes both space and time properties. Among these arrays most remarkable are the Parks Pulsar Timing Array (PPTA) and Kalyazin Pulsar Timing Array (KPTA).
Current and future status of gravitational wave astronomy - gravitational wave facilities
Authors: Rowan Sheila 
Published: December 2007

AbstractCurrently a network of interferometric gravitational wave detectors is in operation around the globe, in parallel with existing acoustic bar-type detectors. Searches are underway aimed at the first direct detection of gravitational radiation from astrophysical sources. This paper briefly summarizes the current status of operating gravitational wave facilities, plans for future detector upgrades, and the status of the planned space-based gravitational wave detectorLISA.
International Virtual Observatory Alliance
Authors: Ohishi Masatoshi 
Published: December 2007

AbstractThe International Virtual Observatory Alliance is briefly introduced as a concensus-based group to construct International Virtual Observatory – a new, planet-wide research infrastructure for the 21st century astronomy. Standardized protocols by the IVOA were used to interconnect more than 10 astronomical obsrvatories and data centers to provide astronomers with multiwavelength astronomical data. The priority areas for technical development and planned developments are described.
Special Session 7 Astronomy in Antartica
Authors: Burton Michael G. 
Published: December 2007

AbstractThe high, dry and stable climatic conditions on top of the Antarctic plateau offer exceptional conditions for a wide range of observational astronomy, from optical to millimetre wavelengths. This is principally on account of the greatly reduced thermal backgrounds, the improved atmospheric transmission and the supurb seeing, in comparison with conditions at temperate latitude sites. The polar plateaus in the Arctic may also offer excellent conditions for astronomy, though these have yet to be quantified. We briefly review the history of astronomy in Antarctica and outline some of the activities now taking place on the polar plateaus, and plans for the future.