bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Bottom Magnetic Fields of Millisecond Pulsars
Authors: Zhang Chengmin
Published: July 2016

The magnetic field strengths of most millisecond pulsars (MSPs) are about 108–9 gauss. The accretion-induced magnetic field evolution scenario here concludes that field decay is related to the accreted mass, that the minimum or bottom field stops at about 108 gauss for Eddington-limited accretion, and scales with the accretion rate as M1/2. The possibility of low field (∼ 107 gauss) MSPs has been proposed for future radio observations.
Monitoring the Evolution of SNR 1987A with Chandra
Authors: Park Sangwook , Burrows David N. , Garmire Gordon P. , Zhekov Svetozar A. , McCray Dick
Published: July 2016

We report on the results of our monitoring program of SNR 1987A with the Chandra X-Ray Observatory. The high resolution images and the spectra from the latest Chandra data suggest that the blast wave has reached the dense inner ring on the western side of the SNR, as well as in the east. The observed soft X-ray flux is increasing more rapidly than ever, and the latest flux is four times brighter than three years ago.
The Environment of Tycho: Possible Interaction with Molecular Clouds
Authors: Lee Jae-Joon , Koo Bon-Chul , Tatemastu Keni'chi
Published: July 2016

We have conducted 12CO observations with the Nobeyama 45-m telescope in the area of Tycho's supernova remnant. These high-resolution (16″) data show that the molecular cloud surrounds the SNR along the northeastern boundary. We suggest that Tycho's SNR and the molecular cloud are located at comparable distances within the Perseus arm and that they are physically interacting. We also discuss the possible connection between the molecular cloud and the Balmer-dominated optical filaments and propose that the preshock gas may be accelerated within the cosmic-ray and/or fast neutral precursor.
X-ray Spectroscopy of the Southwest Cygnus Loop
Authors: Leahy D. A.
Published: July 2016

The Cygnus Loop is one of the nearest supernova remnants (440 pc) and has been studied extensively in radio through X-ray wavelengths. An unusual bright “V”-shaped region on the south-western limb (near RA 20h46m and Decl. +30°) was revealed in ROSAT PSPC observations of the Cygnus Loop. The left side of the “V” has one of the highest hardness ratios (0.9–2 keV / 0.1–0.4 keV) in the Cygnus Loop whereas the right side has one of the lowest. Images and spatially resolved spectra were obtained using Chandra ACIS observations. Some results of analysis of the images and spectra are presented here.
A Search for Radio Pulsars at High Galactic Latitude
Authors: Jacoby B. A.
Published: July 2016

We have completed a search for radio pulsars using the Parkes 64 m telescope, covering ∼4500 deg2 between 15° and 30° from the Galactic plane. Each pointing was observed for 265 s with the 13-beam multibeam system at a frequency of 1374 MHz. The signal from each beam was processed by a 96-channel filterbank and sampled every 125 μs, with a bandwidth of 288 MHz. This strategy affords rapid sky coverage and good sensitivity to pulsars with periods as short as 1 ms, whose existence would constrain the neutron star equation of state. Data were analyzed using the workstation cluster at the Swinburne Centre for Astrophysics and Supercomputing. This effort has yielded 26 new pulsars, including seven recycled pulsars. Taken together with the previous Swinburne Intermediate Latitude Pulsar Survey, a total of 95 new pulsars were found over nearly 7500 deg2 of sky between 5° and 30° from the plane of the Galaxy. This large sample of newly discovered objects contains no young pulsars.
Pulsar Searches at Effelsberg
Authors: Klein B. , Kramer M. , Müller P. , Wielebinski R.
Published: July 2016

We report on the progress of our search for highly dispersed pulsars near the Galactic Center at 5 GHz using the 100-m radio telescope in Effelsberg. We also present key aspects of our new survey for millisecond pulsars at 21 cm in parts of the northern sky. This survey will greatly benefit from the L-band multibeam receiver and a new FFT-based backend which are currently under construction at the MPIfR.
The ATNF Pulsar Catalog
Authors: Hobbs G. , Manchester R. , Teoh A. , Hobbs M.
Published: July 2016

The number of known pulsars has significantly increased over the past few years. We have searched the literature to find papers announcing the discovery of pulsars or giving improved parameters for them. Data from the papers have been entered into a new pulsar catalog that can be accessed via a web interface or from the command line (on Solaris or Linux machines). The user may request over 120 different parameters, select pulsars of interest, generate custom variables and choose between different ways of displaying or tabulating the datA. Full bibliographic references are available for all observed parameters.
Theory of Pulsar Winds
Authors: Melatos A.
Published: July 2016

Recent progress in the theory of pulsar wind electrodynamics is reviewed, with emphasis on the following open questions, (i) Is the bipolar, jet-torus geometry imprinted by collimation or injection? (ii) what is the magnetic field geometry as a function of latitude, and is it stable? (iii) How rapidly does the postshock flow fluctuate, e.g. in the near infrared? (iv) The σ paradox: is Poynting flux converted gradually to kinetic energy flux as the wind expands, as in a linear accelerator, or is the conversion lossy, due to reconnection or parametric instabilities in a wave-like outflow?
Acceleration and Dissipation in Relativistic Winds
Authors: Arons Jonathan
Published: July 2016

I argue that ideal MHD relativistic winds are always limited in practice to asymptotic 4-velocity γ∞ ≍ σ1/30 and asymptotic magnetization σ ∼ σ 2/30 ≫ 1, where σ0 is the wind magnetization with respect to the rest energy density, evaluated at the light cylinder of the rotating, magnetized compact object that drives the flow. This suggests that the observed low value of the asymptotic σ in the equatorial sectors of the winds driving pulsar wind nebulae and the associated high values of the asymptotic 4-velocity are a consequence of magnetic dissipation in the wind zone.
High Resolution X-ray Observations of 3C 58
Authors: Slane Patrick
Published: July 2016

As the presumed remnant of SN 1181, 3C 58 houses one of the youngest known neutron stars in the Galaxy. The properties of this young pulsar and its associated pulsar wind nebula (PWN) differ considerably from those of the Crab Nebula, and may well offer a more typical example of the endpoint of massive star collapse. High resolution X-ray studies reveal structures in the inner nebula that may be associated with the pulsar wind termination shock, a jet that may be aligned with the rotation axis, and other regions of enhanced emission. Spectral variations in the PWN are consistent with the expected evolution of the postshock flow, and complex loops of emission are seen in the nebula interior. Limits on the neutron star surface temperature fall below standard cooling models, indicating that some more rapid neutrino cooling process is required. The outer regions of 3C 58 show thermal emission with enhanced levels of neon, indicative of shocked ejecta bounding the PWN.
XMM-Newton and Geminga
Authors: Caraveo Patrizia , De Luca Andrea , Mereghetti Sandro , Pellizzoni Alberto , Bignami Giovanni , Tur Anatoly , Mignani Roberto , Becker Werner
Published: July 2016

A deep XMM-Newton/EPIC observation of the field of the Geminga pulsar unveiled the presence of two elongated parallel X-ray tails trailing the neutron star. They are aligned with the object's supersonic motion, extend for ∼ 2′, and have a nonthermal spectrum produced by electron-synchrotron emission in the bow shock between the pulsar wind and the surrounding medium. Such a first ever X-ray detection of a pulsar bow shock allows us to gauge the pulsar electron injection energy and the shock magnetic field while constraining the angle of Geminga's motion and the local matter density.
Quiescent Magnetar Emission: Resonant Compton Upscattering
Authors: Baring Matthew G.
Published: July 2016

A principal candidate for quiescent non-thermal gamma-ray emission from magnetars is resonant inverse Compton scattering in the strong fields of their magnetospheres. This paper outlines expectations for such emission, formed from non-thermal electrons accelerated in a pulsar-like polar cap potential upscattering thermal X-rays from the hot stellar surface. The resultant spectra are found to be strikingly flat, with fluxes and strong pulsation that could be detectable by GLAST.
A New Model of “Magnetar”
Authors: Malov I. F. , Machabeli G. Z. , Malofeev V. M.
Published: July 2016

A new model is proposed to explain the main properties of anomalous X-ray pulsars and soft gamma-ray repeaters, in terms of drift waves in the vicinity of the light cylinder of a neutron star with a surface magnetic field ∼ 1012 G.
X-ray Spectroscopy of Thermally Emitting Neutron Stars
Authors: van Kerkwijk M. H.
Published: July 2016

I describe recent high-resolution X-ray spectroscopy of surface emission from nearby, thermally emitting neutron stars. I focus on RX J0720.4−3125, RX J1308.6+2127 and RX J1605.3+3249, all of which have similar temperature, but differ in the presence and strength of absorption features in their spectrA. I discuss possible causes for the absorption we see in two sources, and conclude that it may be proton cyclotron line absorption, but weakened due to the strong-field quantum electrodynamics effect of vacuum resonance mode conversion.
Structure of Strange Quark Matter and Neutron Stars
Authors: Lattimer James M.
Published: July 2016

The properties of neutron and strange matter stars are discussed from global and observational perspectives. The global features, i.e., the mass-radius relation, the moment of inertia, and the binding energy, of these objects can be understood by examination of the few known relevant analytic solutions to Einstein's equations. A close connection exists between neutron star radii and the density dependence of the isospin dependence of strong interactions, i.e., the nuclear symmetry energy. Interestingly, a similar relation has been found to exist between the symmetry energy and the neutron skin thickness of neutron-rich nuclei, the object of a new generation of laboratory experiments, although these are 1018 times smaller. Recent observations of neutron star masses and radiation radii are summarized. The status of these observations as predictors of nuclear force properties is examined. The combination of observations, laboratory experiments, and theory is an extremely powerful tool for both nuclear physics and nuclear astrophysics.
RX J1856.5−3754: A Strange Star with a Solid Quark Surface?
Authors: Zhang X. L. , Xu R. X. , Zhang S. N.
Published: July 2016

Within the realms of possibility of solid quark matter, we fitted the 500 ks Chandra LETG/HRC data for RX J1856.5−3754 with a phenomenological spectral model, and found that the electric conductivity of quark matter on the stellar surface is about > 1.2 × 1018 s−1.
Radio Pulse Observations of Neutron Stars: A Review
Authors: Gupta Yashwant
Published: July 2016

This paper presents a review of recent advances in those observations of radio pulsars which are relevant to the understanding of “where” and “how” the radio signals are generated in the magnetosphere of the neutron star. These include (i) results from simultaneous multi-frequency observations, (ii) emission geometry studies of multi-component pulsars, (iii) results from drifting and nulling pulsars, (iv) constraints from single pulse statistics and (v) progress in giant pulse studies.
Phase-resolved Spectroscopy of the Crab Pulsar with XMM-Newton
Authors: Kirsch M. G. F. , Kendziorra E. , Staubert R.
Published: July 2016

The Crab pulsar (PSR B0531+21) has been observed with the EPIC-pn camera on board the ESA XMM-Newton satellite. The high time resolution of the EPIC camera (7 μs) in its special Burst mode in combination with the huge effective area and the high quantum efficiency of the pn-CCD allows phase resolved spectroscopy of good quality over the energy range 0.6–8.5 keV. We performed phase resolved spectroscopy of the modulated flux of the Crab pulsar and found a significant hardening of the photon index in the inter-pulse region. Also the second pulse is harder in index by 0.1 than the first pulse.
Thirteen Drift Bands in PSR B0826–34
Authors: Esamdin A. , Lyne A. G. , Kramer M. , Graham-Smith F. , Manchester R. N.
Published: July 2016

By developing a new technique, 13 drifting subpulses have been revealed across one period in PSR B0826–34. The variation of drift rate when drifting subpulses drift through different longitude regions are noticed. A weak emission mode was detected during its apparent null.
A Resonant-Mode Model of Pulsar Radio Emission
Authors: Young M. D. T.
Published: July 2016

It is argued that the polar gap and flux tube in the pulsar magnetosphere act as a resonant cavity/waveguide system which is excited by oscillations in the primary beam current and accelerating potential. The modes will be converted, probably scattered, to produce radio beams in the frequency range of those observed.
Two-pole Caustic Model for High-energy Radiation from Pulsars — Polarization
Authors: Dyks Jarosław , Harding Alice K. , Rudak Bronisław
Published: July 2016

We present high-energy light curves and polarization properties of pulsars calculated within the recently proposed two-pole caustic model. The results are compared with the optical data for the Crab pulsar and with predictions of other high-energy pulsar models: the polar cap model, and the outer gap model.
Particle Acceleration Above the Pulsar Polar Cap
Authors: Luo Qinghuan
Published: July 2016

The constraint on the formation of a polar gap by acceleration in the outer magnetospheric region is discussed.
On the Mechanism of X-ray Emission from Radio Pulsars
Authors: Malov I. F.
Published: July 2016

The correlations between the luminosities of radio pulsars in various wavebands and the magnetic fields at the light cylinder suggest that the observed emission is generated in outer layers of the pulsar magnetospheres by the synchrotron mechanism. The formula for calculating the X-ray luminosity LX of radio pulsars is derived in the framework of the synchrotron model. It is shown that LX depends strongly on the parameter This raises the possibility of predicting the detection of X-ray emission from more than a hundred known radio pulsars.
A Monte Carlo Study of Gamma-Ray Pulsars in the Gould Belt
Authors: Leung P. , Cheng K. S. , Zhang L. , Jiang Z. J.
Published: July 2016

We use Monte Carlo techniques to simulate the statistical properties of rotation-powered pulsars in the Gould Belt. The gamma-ray properties of these pulsars are calculated by using a self-consistent outer gap model and other pulsar properties, i.e., initial magnetic field and period, and velocity distribution of the neutrons stars at birth, are obtained from the statistics of radio pulsars. We obtain distributions of the magnetic inclination angle, period, distance and age for these gamma-ray pulsars in the Gould Belt.
The Young Binary Pulsar J1740–3052
Authors: Stairs I. H.
Published: July 2016

The young pulsar PSR J1740–3052, discovered in the Parkes Multibeam Pulsar Survey, is in a highly eccentric 8-month orbit with a companion of at least 11 solar masses. The up-to-date timing solution for this pulsar incorporates effects likely due to the spin mass quadrupole of the companion star; we discuss the implications for the geometry of the orbit. The pulsar signal displays increased dispersive delays as the pulsar passes behind its companion, indicating an interaction with the companion wind.
Timing of the Binary Pulsar B1259–63
Authors: Wang N. , Johnston S. , Manchester R. N.
Published: July 2016

This paper summarizes the results of 13 years of timing observations of a unique binary pulsar, B1259–63, which has a massive B2e star companion. A small glitch in the pulsar period apparently occurred in 1997 Aug, not long after the 1997 periastron. We found that spin-orbit coupling with secular changes in periastron longitude and projected semi-major axis cannot account for the observed period variations. A model in which step changes in pulsar orbital parameters occur at each periastron accounts best for the observed timing behavior.
Timing Observations of PSR B1937+21 at CRL
Authors: Hanado Y. , Shibuya Y. , Nakagawa F. , Sekido M. , Hosokawa M. , Imae M.
Published: July 2016

Pulsar parameters of PSR B1937+21 acquired from observations at the Kashima 34-m antenna over five years are consistent with published reports. The frequency stability is 2 × 10−14 over the data span of 6.5 years using Kashima data combined with Parkes data.
Accretion Onto the Neutron Star in Be/X-ray Binaries
Authors: Hayasaki Kimitake , Okazaki Atsuo T.
Published: July 2016

We study accretion onto the neutron star in Be/X-ray binaries, using a 3D SPH code and the data imported from a high resolution simulation by Okazaki et al. (2002) for a coplanar system with a short period (Porb = 24.3 d) and moderate eccentricity (e = 0.34). We find that a time-dependent accretion disk is formed around the neutron star in Be/X-ray binaries. The disk shrinks after the periastron passage of the Be star and restores its radius afterwards. Our simulations show that the truncated Be disk model for Be/X-ray binaries is consistent with the observed X-ray behavior.
The Sun as a Stellar Laboratory: Unsolved Problems
Authors: C. Brown John
Published: July 2016

A brief overview is given of some of the current outstanding problems in solar physics with greatest emphasis on high energy phenomena in the atmosphere. The importance of plasma kinetic effects, as well as MHD, in understanding the complex finely structured and dynamic solar atmospheric plasma is stressed. Key results from the RHESSI Mission on energetic flare particle acceleration, propagation, and flare energy budgets are presented as are recent findings concerning the solar and stellar flare Neupert effect and the possible role of energetic particles in micro-events in the ‘non-flaring’ sun. Finally, evidence showing that magnetic fields are also important in hot star phenomena is mentioned.
Dynamics and Heating of Chromospheres
Authors: Kalkofen Wolfgang
Published: July 2016

Heating and dynamics of the solar as well as stellar chromospheres are separate phenomena, judging by their spatial and temporal characteristics in the Sun. Simulations of chromospheric heating in late-type stars as well as simulations of the dynamics of the large-amplitude oscillations of internetwork calcium bright points in the solar atmosphere reproduce the main features of the respective phenomena. Differences between models and observations imply (1) that the Sun has a permanent, hot chromosphere and that its temperature structure cannot be obtained by averaging the time-dependent temperature profile of a model that describes only the oscillations, and (2) that the acoustic waves causing the dynamics and the heating propagate upward as spherical waves.
Abundances of Potassium, Argon, and Sulphur in Solar Flares
Authors: H. Phillips K. J. , Sylwester J. , Sylwester B. , Landi E.
Published: July 2016

Observations of the 3.3—6.1 Â X-ray line and continuous spectrum during four long-duration flares with the RESIK crystal spectrometer on the Coronas-F spacecraft have been analyzed to get the absolute abundances of potassium, argon, and sulphur. A differential emission measure of the form DEM ∝ exp(—Te/T0) was found to give the most consistent results of three models including an isothermal model. We obtained K/H = (3.7 ± 1.0) x 10—7, a factor 3 times photospheric; Ar/H = (2.8 ± 0.2) x 10—6, slightly lower than photospheric; and S/H = (2.2±0.4) x 10—5, approximately equal to photospheric. These measurements are consistent with a pattern in which elements with low (< 10 eV) first ionization potential are enriched in the corona by a factor of about 3 and elements of high first ionization potential have abundances approximately equal to photospheric.
X-ray Emission from Young Stars in Suburban Orion
Authors: Briggs K. , Güdel M. , Audard M. , Smith K. , Mewe R. , den Boggende T.
Published: July 2016

X-ray emission from > 100 pre-main sequence (PMS) stars in the Orion star-forming complex is studied in a 20-ks observation by XMM-Newton. No relation between the ratio of X-ray and bolometric luminosities, LX/Lbol, and rotation period or Rossby number is exhibited, though the action of a solar-like dynamo is not excluded because all stars would appear to be in the “saturated regime” of such a dynamo. Low-mass stars showing a strong U — V excess have lower median X-ray luminosity, suggesting that accretion suppresses magnetic activity.
The Photospheric Abundances of Active Binaries: First Results
Authors: Morel T. , Micela G. , Favata F. , Katz D. , Pillitteri I.
Published: July 2016

Photospheric parameters and abundances of 13 chemical species are presented for a sample of single-lined chromospherically active binaries from a differential LTE analysis of high-resolution spectra. Our results indicate that the X-ray active binaries studied are not as metal poor as previously claimed, but are at most mildly iron-depleted relative to the Sun (—0.41 ≲ [Fe/H] ≲ +0.11). A significant overabundance of several elements (e.g., Na, Mg, Al, Ca) is observed. The temperatures derived from the (V — R) and (V — I) colours are found to be significantly affected by activity processes.
Between Cool Stars and Hot Planets: Origins of Brown Dwarfs
Authors: Jayawardhana Ray
Published: July 2016

Brown dwarfs, which straddle the mass range between stars and planets, appear to be common both in the solar neighborhood and in star-forming regions. Their ubiquity makes the question of their origin an important one both for our understanding of brown dwarfs themselves as well as for theories on the formation of stars and planets. Studies of young sub-stellar objects could provide valuable insight into their formation and early evolution. Here I report on the latest results from our observational programs at Keck, VLT and Magellan on the disk and accretion properties of young brown dwarfs. We find compelling evidence that they undergo a T Tauri phase analogous to that of their stellar counterparts.
Using Chandra/LETG Spectra to Probe Stellar Coronae
Authors: J. Hussain Gaitee A. , Brickhouse Nancy , Dupree A. K. , van Ballegooijen Adriaan A. , Collier Cameron Andrew , Jardine Moira , Donati Jean-Francois
Published: July 2016

We probe the relationship between surface magnetic fields and the X-ray emitting corona in the rapidly rotating star, AB Dor. Circularly polarised spectra have been inverted to produce a surface (photospheric) magnetic field map. This surface map has been extrapolated to model AB Dor's coronal field topology and X-ray light curve. Chandra/LETG light curves of AB Dor from the same epoch show intrinsic variability at the 30% level. Period analysis indicates a fraction of this is due to rotational modulation. We measure velocity shifts in emission line centroids as a function of Prot and find evidence of rotational modulation (max. vel. ∼ 40 ± 13km s—1). This modulation may indicate the presence of a localised X-ray emitting region at mid-to-high latitudes.
Extra-solar Planets: Clues to Planetary Formation
Authors: Santos Nuno C. , Mayor Michel , Naef Dominique , Pepe Francesco , Queloz Didier , Udry Stéphane
Published: July 2016

Radial velocity surveys have revealed up to now about 115 extra-solar planets, among which a few multi-planetary systems. The discovered planets present a wide variety of orbital elements and masses, which are raising many problems and questions regarding the processes involved in their formation. The statistical analysis of the distributions of orbital elements, planetary masses, and relations between these, is however already giving some strong constraints on the formation of the planetary systems. Furthermore, the study of the planet host stars has revealed the crucial role of the stellar metallicity on the giant planet formation. In this paper we will review the current status of the research on this subject.
Abundances in Stars with Exoplanets
Authors: Israelian Garik
Published: July 2016

Extensive spectroscopic studies of stars with and without planets have concluded that stars hosting planets are significantly more metal-rich than those without planets. More subtle trends of different chemical elements begin to appear as the number of detected extrasolar planetary systems continues to grow. I review our current knowledge concerning the observed abundance trends of various chemical elements in stars with exoplanets and their possible implications.
Stellar Activity Enhancement by Planets: Theory and Observations
Authors: Saar S. H. , Cuntz M. , Shkolnik E.
Published: July 2016

Many of the newly discovered exoplanets are gas giants in close proximity to their parent stars. Therefore, they raise tides on their host stars, and (if similar to Jupiter) will likely have substantial magnetospheres which can interact with stellar magnetic field. Both tidal and magnetospheric interactions can enhance stellar activity levels. An initial search for such planet-induced activity using the Ca ii IR triplet found no clear signal, but recently a more sensitive study using the Ca ii H and K lines has uncovered evidence for planet-enhanced emission on HD 179949, and hints of it in other systems. The phase dependence of the enhanced emission for HD 179949 suggests a magnetospheric interaction. We discuss a simple model of this interaction, the implications of this possible detection for diagnosing exoplanetary magnetospheres, and future observations.
Radio Emissions from Terrestrial Planets around White Dwarfs
Authors: Willes Andrew , Wu Kinwah
Published: July 2016

Terrestrial planets in close orbits around magnetic white dwarf stars can be electron-cyclotron maser sources, by analogy to planetary radio emissions generated from the electrodynamic interaction between Jupiter and the Galilean moons. We present predictions of the radio flux densities from white-dwarf/terrestrial-planet systems and discuss a scenario for the formation of these systems.
Giant Planets and Variable Stars in 47 Tucanae - a Progress Report of a Comprehensive Ground-Based Search
Authors: F. Weldrake David T. , Sackett Penny D. , Bridges Terry J.
Published: July 2016

Here we present a short progress report of a comprehensive search for variability in the globular cluster 47 Tucanae. Using the MSSSO 40” telescope and a combined V+R filter, we are searching for variability across a 52×52' field centered on the cluster. The main aim is to search for transiting ‘Hot Jupiter’ planets in this cluster, the results of which are still being produced, but a natural side product is a deep catalogue of variable stars within the cluster field. The experiment samples the whole of the cluster (except the inner 5'), thus probing the uncrowded outer regions where the stellar densities are lower, increasing the prospects for the survivability of planetary systems. Half of the currently identified variable stars are new discoveries. We have data for 36,000 stars with masses similar to that of the Sun for the main transit search.
Loops: Twisting and Scaling
Authors: Walsh Robert W.
Published: July 2016

Loop-like structures are the fundamental magnetic building blocks of the solar atmosphere. Recent space-based EUV and X-ray satellite observations (from Yohkoh, SOHO and TRACE) have challenged the view that these features are simply static, gravitationally stratified plasma pipes. Rather, it is now surmised that each loop may consist of a bundle of fine plasma threads that are twisted around one another and can brighten independently. This invited paper will outline the latest developments in “untangling” the topology of these features through observational analysis and magnetohydrodynamic modelling. In particular, recent interest has centred on how the observed thermal profile along loops can be employed as a tool to diagnose any localised energy input to the structure and hence constrain the presence of a particular coronal heating mechanism. The implications of superior resolution plasma thread observations (whether spatial, temporal or spectral) from future space missions (SolarB, STEREO, Solar Dynamics Observatory and Solar Orbiter) will be discussed.
Large Scale Solar Magnetic Fields: Temporal Variations
Authors: Knaack R. , Stenflo J. O.
Published: July 2016

We have investigated the temporal evolution of the solar magnetic field during solar cycles 20, 21 and 22 by means of spherical harmonic decomposition and subsequent time series analysis. A 33 yr and a 25 yr time series of daily magnetic maps of the solar photosphere, recorded at the Mt. Wilson and NSO/Kitt Peak observatories respectively, were used to calculate the spherical coefficients of the radial magnetic field. Fourier and wavelet analysis were then applied to deduce the temporal variations. We compare the results of the two datasets and present examples of zonal modes which show significant variations, e. g. with a period of approx. 2.0—2.5 years. We provide evidence that this quasi-biennial oscillation originates mainly from the southern hemisphere. Furthermore, we show that low degree modes with odd l — m exhibit periods of 29.2 and 28.1 days while modes with even l — m show a dominant period of 26.9 days. A resonant modal structure of the solar magnetic field (apart from the 22 yr cycle) has not been found.
Dark Matter in Galaxies: Observational overview
Authors: Bosma A.
Published: July 2016

I review the observational side of the present state of the debate about the dark matter in galaxies, with emphasis on the core/cusp problem in low surface brightness galaxies, and the question of maximum/sub-maximum disks in spiral galaxies. Some remarks are made about the dwarf spheroidals around the Milky Way, and about elliptical galaxies.
Astrometric Microlensing by Finite-size Lenses
Authors: Takahashi Rohta
Published: July 2016

I have calculated astrometrical trajectories of microlensing phenomena caused by a spherical finite-size lens consisting of opaque material. For details, see Takahashi (2003).
Gravitational Lens Statistics as a Probe of Halo Profiles
Authors: Oguri Masamune
Published: July 2016

Recent development of the structure formation theory based on the cold dark matter scenario implies that a number of larger separation lensed quasars, for which a confirmed detection has not yet been achieved, will be observed in the ongoing large-scale surveys such as the 2dF survey and SDSS. We show that statistics of such large separation lenses can be a powerful probe of the density profile of dark halos. After we summarize the current status of the lens surveys in the 2dF and SDSS, we focus our discussion on what information can be extracted from these lens surveys. in addition, we also propose statistics of differential time delays between multiple images as an alternative probe of the density profile of dark halos.
X-Ray Constraints on Dark Matter in Galaxy Clusters and Elliptical Galaxies: A View from Chandra and XMM
Authors: Buote David A.
Published: July 2016

X-ray observations with Chandra and XMM are providing valuable new measurements of the dark matter content of elliptical galaxies and galaxy clusters. I review constraints on the radial density profiles and ellipticities of the dark matter in these systems (with an emphasis on clusters) obtained from recent X-ray observations and discuss their implications, especially for the self-interacting dark matter model.
Is there a dichotomy in the Dark Matter as well as in the Baryonic Matter properties of ellipticals?
Authors: Napolitano N. R. , Capaccioli M. , Arnaboldi M. , Merrifield M. R. , Douglas N. G. , Kuijken K. , Romanowsky A.J. , Freeman K.C.
Published: July 2016

We have found a correlation between the M / L global gradients and the structural parameters of the luminous components of a sample of 19 early-type galaxies. Such a correlation supports the hypothesis that there is a connection between the dark matter content and the evolution of the baryonic component in such systems.
Directions of cosmic anisotropies
Authors: Bajan Katarzyna , Flin Piotr , Pervushin Victor N.
Published: July 2016

We argue that the recently reported anisotropy of the local velocity field is in good agreement with other cosmic anisotropies and they are all explainable by the Great Attractor.
Molecular hydrogen as dark mass in dwarf galaxies
Authors: Williams P. R. , Marzok C. , Myers S. , Nelson A. H.
Published: July 2016

We report here an example of a series of computer simulations of the formation of disk galaxies, including a standard cold dark matter component, gas, and star formation, which result in objects which closely resemble observed giant galaxies, with a population of long-lived dwarf satellites which contain little or no non–baryonic dark matter.
Formation of inner rings in 3D potentials of barred galaxies
Authors: Patsis Panos A. , Skokos Charalampos , Athanassoula E.
Published: July 2016

In a 3D analytic potential we find the families of periodic orbits that support the formation of inner rings. These are families at high energies, between the inner radial ultraharmonic 4:1 (iUHR) resonance and corotation, influenced by the 4:1, 6:1 and 8:1 resonances. the inner rings they support are mainly ovals and polygons with ‘corners’ on the bar minor axis, on its sides, which correspond to morphologies often seen in real galaxies like NGC 6782 and IC 4290. We also investigate the conditions under which less probable shapes of rings may be supported by orbits at the region. Such rings include pentagonal features (NGC 3367) and hexagons with cusps on the major axis of the bar and two sides parallel to it (NGC 7020).
The mass distribution in early type disk galaxies
Authors: Noordermeer Edo , Van Der Hulst Thijs , Sancisi Renzo , Swaters Rob
Published: July 2016

We are studying the mass distribution in a sample of 50 early type spiral galaxies, with morphological type betweens SO and Sab and absolute magnitudes Mb between −18 and −22; they form the massive and high-surface brightness extreme of the disk galaxy population. Our study is designed to investigate the relation between dark and luminous matter in these systems, of which very little yet is known.

From a combination of WSRT Hi observations and long-slit optical spectra, we have obtained high-quality rotation curves. the rotation velocities always rise very fast in the center; in the outer regions, they are often declining, with the outermost measured velocity 10-25% lower than the maximum.

We decompose the rotation curves into contributions from the luminous (stellar and gaseous) and dark matter. the stellar disks and bulges always dominate the rotation curves within the inner few disk scale lengths, and are responsible for the decline in the outer parts. As an example, we present here the decompositions for UGC 9133. We are able to put tight upper and lower limits on the stellar mass-to-light ratios.
Cores vs. Cusps: Dark Matter Density Profiles in Spirals
Authors: Gentile Gianfranco , Klein Uli , Salucci Paolo , Vergani Daniela
Published: July 2016

We use photometric, Hα and Hi data to investigate the distribution of dark matter in spiral galaxies. A new technique for deriving the Hi rotation curve is presented. the final combined Hα+Hi rotation curves are symmetric, well resolved and extend to large radii. We perform the rotation curve decomposition into the luminous and dark matter contributions. the observations are confronted with different models of the dark matter distribution, including core-dominated and cusp-dominated halos as well as less conventional possibilities. the best agreement with the observations is found for the core-dominated halos.
Amplitude of Spiral Arms and Dark Matter
Authors: Grosbøl P.
Published: July 2016

Relative amplitudes and pitch angles for the main two-armed spiral structure in a sample of 54 non-barred spiral galaxies were estimated from K band photometry. A lack of strong, tight patterns was observed which may be caused by non-linear dynamic effects. Assuming that the upper envelope corresponds to a relative radial forcing of ⋐5%, one can estimate the perturbation of the total potential. This suggests that a maximum disk solution is adequate to account for the force perturbation and that no additional dark matter is required.
Nuclear Spirals and Supermassive Black Holes
Authors: Ann H. B. , Thakur Parijat
Published: July 2016

We have performed SPH simulations for the response of the gaseous disks to the imposed potentials including those from bars and SMBHs. Evolution of the nuclear regions of gaseous disks depends critically on the masses of SMBHs as well as the sound speed in the gas.
Central DM density cuspiness in LSB's: a stellar kinematics approach
Authors: Pizzella A. , Corsini E.M. , Bertola F. , Coccato L. , Magorrian J. , Sarzi M. , Funes J.G.
Published: July 2016

We present preliminary results from spectroscopic observations of a sample of 11 low surface brightness galaxies (LSB). We measured the stellar and gaseous kinematics along their major and minor axes. Such information will allow us to accurately investigate the dark matter (DM) content within their optical regions, providing further constraints on the predictions of standard CDM models. Although dynamical modeling is still in progress, our observations already show that the derived stellar kinematics is more regular than the ionized gas one, which often shows evidence for non-circular and asymmetric motions.
Inner Halo Shapes of Dwarf Galaxies: Resolving the Cusp/Core Problem
Authors: Spekkens Kristine , Giovanelli Riccardo
Published: July 2016

We derive inner dark matter halo density profile slopes for a sample of 200 dwarf galaxies by inverting rotation curves obtained from high-quality, long-slit optical spectra. Using simulations to assess the impact of long-slit observing and data processing errors on our measurements, we conclude that our observations are consistent with the cuspy halos predicted by the CDM paradigm.
Properties of galaxy dark matter halos from weak lensing
Authors: Hoekstra Henk , Yee Howard K.C. , Gladders Michael D.
Published: July 2016

We present the results of a study of the average mass profile around galaxies using weak gravitational lensing. We use 45.5 deg2 of RC band imaging data from the Red-Sequence Cluster Survey (RCS) and define a sample of ~ 1.2 × 105 lenses with 19.5 < RC < 21, and a sample of ~ 1.5 × 106 background galaxies with 21.5 < R < 24.

We constrain the power law scaling relations between the B-band luminosity and the mass and size of the halo, and find that the results are in excellent agreement with observed luminosity–line-width relations. Under the assumption that the luminosity does not evolve with redshift, the best fit NFW model yields a mass M200 = (8.8±0.7) × 1011h–1M⊙ and a scale radius rs = I6.7+3.7–3.0h–1 kpc for a galaxy with a fiducial luminosity of Lb = 1010h–2LB⊙. the latter result is in excellent agreement with predictions from numerical simulations for a halo of this mass. We also observe a signficant anisotropy of the lensing signal around the lenses, implying that the halos are flattened and aligned with the light distribution. We find an average (projected) halo ellipticity of 〈ehalo〉 = 0.20+0.04–0.05, in fair agreement with results from numerical simulations of CDM. Alternative theories of gravity (without dark matter) predict an isotropic lensing signal, which is excluded with 99.5% confidence. Hence, our results provide strong support for the existence of dark matter.
Observational Constraints on the Physical Parameters of Dark Matter Halos
Authors: Carignan Claude
Published: July 2016

After looking at the difference in the mass distribution between massive spiral and dwarf irregular (dIrr) and low surface brightness (LSB) galaxies, the central Dark Matter (DM) concentration (flat vs cuspy) in dwarf and LSB galaxies, derived from observations, will be examined. We will then present what kind of observational constraints can be put on the total mass and total extent of DM halos from the studies of individual galaxies, small groups, satellites' dynamics and tidal tails of interacting systems. Finally, we will discuss how limits on the physical parameters of DM halos could be set by deriving extended rotation curves beyond the HI radius (r > rHI), using either Lyα absorption or Hα emission observations.
Can quantum theory explain dark matter?
Authors: Ernest A. D.
Published: July 2016

Certain solutions to a gravitational form of Schrödinger's equation can yield stable, macroscopic eigenstate solutions having no classical analogue, with properties resembling those of dark matter. Some more tractable solutions show: (1) radiative lifetimes far exceeding the universe's age, implying negligible emission and inherent stability w.r.t. gravitational collapse, (2) negligible interaction with EMR and visible matter, (3) potential to give rise to flat rotation curves and (4) eigenstate energies and “sizes” consistent with that expected for the galactic halo. Traditional baryonic particles occupying such eigenstates will be invisible and weakly interacting, and may be assimilated into galactic evolution scenarios without significantly disturbing BBN ratios. It is proposed that such structures may explain the nature and origin of dark matter.
The Dynamics of Solar Coronal Magnetic Fields
Authors: Low B. C.
Published: July 2016

The solar corona is a hot (106K) highly ionized plasma structured by its magnetic field into open regions where the solar wind escapes and closed regions where relatively dense plasma is trapped in near static equilibrium. Observed in Thomson-scattered light at times of solar eclipse or by artificial occultation using a coronagraph, these closed regions show up conspicuously as helmet-shaped bright structures. The large scale corona evolves in time in response to the solar dynamo that continually injects new magnetic flux into the corona with the eventual reversal of the global magnetic polarity at the end of each half cycle of eleven years. It was discovered in the 1970s using spaceborne coronagraphs that in addition to its long-term evolution, the corona also undergoes dynamical reconfiguration with ejection of mass of the order of 1015g into interplanetary space (MacQueen 1980). These time dependent phenomena take place once every few days at solar activity minimum and as often three times a day at solar activity maximum. Since the 1970s, coronal mass ejections have been studied at the High Altitude Observatory by the use of the coronagraph on the NASA Solar Maximum Mission Satellite and groundbased instruments at Hawaii. This brief review presents three points of interest in the coronal mass ejection as a hydromagnetic process, emphasizing the unique opportunity offered by the corona to study hydromagnetic phenomena by direct observation (Hundhausen 1987, Kahler 1987, Low 1986).
Magnetized Langmuir Solitons Around Pulsars
Authors: Asseo E. , Pelletier G. , Sol H.
Published: July 2016

Most theoretical works, which aim to interpret the radio radiation observed from pulsars, are based on the idea that coherence of the pulsar emission process could result from the development of plasma instabilities in the magnetosphere of the star. In particular the Ruderman-Sutherland (1975) magnetic pole model reproduces in a satisfying manner several features of the emission. It is based on the development of the two-stream instability. This instability results from the interaction of a beam and a plasma, both in relativistic motion along the open and curved magnetic field lines issued from the magnetic poles of the star. The possibility to obtain radio radiation through this instability process is limited to part of the open cone of magnetic field lines which form an hollow-cone. We describe the linear and nonlinear evolution of the two-stream instability, in the presence of an extremely strong magnetic field. The linear description, including oblique wave propagation (and eventually curvature of the magnetic lines), shows the existence of a natural coupling between the electrostatic and electromagnetic features of the unstable plasma waves which provides the possibility for a direct electromagnetic emission mechanism. The nonlinear evolution of these waves into Langmuir solitons, with also both electrostatic and electromagnetic features, shows the possibility for a new type of radio radiation mechanism, induced by the presence of transverse perturbations of the solitons, which is of interest for the interpretation of pulsar radio observations.
A Faraday Rotation Survey in the First Quadrant of the Galaxy
Authors: Clegg Andrew , Cordes James
Published: July 2016

We have measured the degree of Faraday rotation towards 73 extra-galactic sources at low Galactic latitudes, predominantly within the first quadrant of longitude. The Faraday rotation towards extragalactic sources follows the trends of that towards pulsars, a fact which vindicates an initial assumption that the rotation arises mostly from within the Galaxy. When combined with the pulsar data, our data imply the existence of magnetic field reversals along several lines of sight. Extragalactic sources withl> 60° have rotation measures that are systematically larger than those for pulsars in the same region, which suggests that the structure responsible for the excess rotation must lie more distant than ~ 7 kpc.
Mean-Field Models of Galactic Dynamos Admitting Axisymmetric and Non-Axisymmetric Magnetic Field Structures
Authors: Rädler K.-H. , Wiedemann E.
Published: July 2016

A concept of mean-field models of galactic dynamos is explained in which α-effect and differential rotation act in an infinite slab of electrically conducting fluid surrounded by free space or by conducting matter at rest. Some results for α2 -dynamos are presented. In the limiting case in which the α-coefficient does not depend on the radius, axisymmetric and non-axisymmetric magnetic fields can be maintained with equal ease. For reasonable α-distributions a preference of axisymmetric fields is suggested as long as an isotropic α-effect is considered but it may disappear with anisotropic α-effect. The effect of differential rotation, which allows αω-dynamos, is briefly discussed.
Galactic Dynamo Theory Confronted with Observations
Authors: Krasheninnikova Yu.S. , Sokoloff D.D. , Ruzmaikin A.A. , Shukurov A.
Published: July 2016

Kinematic models of galactic dynamo in axisymmetric disk show remarkable agreement with observations. We argue that nonlinear effects are relatively weak in galactic dynamos and consider the properties of linear dynamo models inherited by global magnetic configurations in spiral galaxies as well as nonlinear distortions of the linear solutions.
Magnetic Viscosity as the Dominant Shear Force in Accretion Disks
Authors: Kundt W.
Published: July 2016

Matter in accretion disks spirals inward because of angular-momentum losses due to intrinsic shear torques. For galactic disks, the accretion rates can be as high as 1M⊙/yr, corresponding to a value larger than unity of the dimension-less viscosity parameter α. The required torques exceed turbulent ones by at least an order of magnitude; they can, however, be the result of magnetic tensions.

In fast-revolving, clumpy disks, magnetic pressures can exceed static gas pressures and approach ram pressures. Suggestive candidates for such magnetic dominance are the inner, near-rigidly rotating parts of galactic disks.
Regular and Stochastic Dynamics of Relativistic Particles in Alfvén Waves
Authors: Carioli S. M. , Fedorenko V. N.
Published: July 2016

We study the exact phase space dynamics of relativistic test particles propagating in static one-dimensional Alfvén waves, modelling cosmic ray propagation in the interplanetary medium and in the interstellar medium. The result shows that the conventional approach should not be considered adequate to explain important features of particle propagation in Alfvén waves.