bluuebunny/crossref_metadata_2025 huggingface dataset:
HST Observations of Active Galactic Nuclei
Authors: Macchetto F. Duccio
Published: July 2016

The HST has made many contributions to all areas of research in the field of AGN, and I have selected three topics where major progress in our understanding has been made over the last two years. The study of the NLR is key to understanding to what extent the unified model for AGN is applicable. In particular, understanding how the NLR is ionized and how its morphology is defined makes an important contribution to clarify the differences between Seyfert 1 and Seyfert 2. Work by Macchetto et al., Capetti et al., Axon et al., and Wilson et al. has helped clarify the picture. Our work on NGC 1068, Mrk 3, Mrk 7, Mrk 348, Mrk 6, and Mrk 573 has shown the following important properties: a) all AGN with a linear radio jet show emission-line morphology ([O III], [O II], Hα) which is aligned along the jet in a surrounding cocoon; b) those AGN with radio lobes show emission-line morphology which is filamentary and coincident with the position of the lobes; and c) in NGC 1068 and in Mrk 3 we have measured transverse velocities to the radio-jet as large as 1700 km s−1. These velocities measured at different positions across the radio-jet show an almost perfect velocity ellipsoid, indicating that the cocoon around the jet is expanding, compresses the ISM and shocks and ionizes the region.
AGN Variability
Authors: Kawaguchi Toshihiro , Mineshige Shin
Published: July 2016

A number of monitoring observations of continuum emission from Active Galactic Nuclei (AGNs) have been made in optical-X-ray bands. The results obtained so far show (i) random up and down on timescales longer than decades, (ii) no typical timescales of variability on shorter timescales and (iii) decreasing amplitudes as timescales become shorter. The second feature indicates that any successful model must produce a wide variety of shot-amplitudes and -durations over a few orders in their light curves. In this sense, we conclude that the disk instability model is favored over the starburst model, since fluctuations on days are hard to produce by the latter model.

Inter-band correlations and time lags also impose great constraints on models. Thus, constructing wavelength and time dependent models remains as future work.
Recent Observations of X-ray Emission from Galactic Binary Neutron Stars
Authors: Swank J.
Published: July 2016

Recent measurements of young, accreting binary neutron stars are determining more precise magnetic field and accretion parameters. A low magnetic field, accreting, millisecond pulsar has finally been found in a binary burster. At least 20 low-mass binaries have exhibited high frequency oscillations, 300–1200 hertz. The majority have, for some range of luminosity, the pair of quasiperiodic oscillations that have never been seen in a black hole candidate. Recent evidence from burst oscillations strengthens the case that the difference frequency of this pair is close to the spin frequency of the neutron star. These oscillations are correlated with the spectra, luminosity, and low frequency oscillations. Quasiperiodic oscillations are also seen sometimes in strong magnetic field pulsars, where their origin can be closely examined.
Observation of Black Holes in X-ray Binaries
Authors: Tanaka Y.
Published: July 2016

Recent results of X-ray observations of Galactic X-ray binaries containing black holes are reviewed. So far, eleven X-ray binaries are confirmed to contain a black hole based on the mass determined from the optical mass functions. Study of these X-ray binaries shows that accreting black holes exhibit a characteristic X-ray spectrum that is distinct from that of accreting neutron stars. In total, about two dozen X-ray binaries show this characteristic spectrum and are believed to contain a black hole. Most of them are low-mass X-ray binaries and are transients. The statistics indicate the presence of several hundred or more black holes in quiescent X-ray binaries in our galaxy. The observed properties of accreting black holes are discussed, and other, related subjects are also presented.
Radiative Processes and Geometry of Spectral States of Black-hole Binaries
Authors: Zdziarski A. A.
Published: July 2016

I review radiative processes responsible for X-ray emission in the hard (low) and soft (high) spectral states of black-hole binaries. The main process in the hard state appears to be thermal Comptonization (in a hot plasma) of blackbody photons emitted by a cold disk. This is supported by correlations between the spectral index, the strength of Compton reflection, and the peak frequencies in the power-density spectrum, as well as by the frequency-dependence of Fourier-resolved spectra. Spectral variability may then be driven by the variable truncation radius of the disk. The soft state appears to correspond to the smallest truncation radii. However, the lack of high-energy cutoffs observed in the soft state implies that its main radiative process is Compton scattering of disk photons by nonthermal electrons. The bulk-motion Comptonization model for the soft state is shown to be ruled out by the data.
Gamma-ray Emission from Pulsar Outer Magnetospheres
Authors: Hirotani K.
Published: July 2016

We study the γ-ray emission from an outer-gap accelerator around a rotating neutron star. Assuming the existence of global currents in the magnetosphere, the charge depletion causes a large electric field along the magnetic field lines. This electric field accelerates migratory electrons and positrons which radiate gamma-rays via curvature radiation. These gamma-rays, in turn, produce yet more radiating particles by colliding with the X-rays, leading to a pair-production cascade. Imposing a gap-closure condition that a single pair produces one pair in the gap, on average, we explicitly solve the strength of the acceleration field and demonstrate how the peak energy and the luminosity of the curvature-radiated GeV photons and the cutoff energy and luminosity of Compton-scattered TeV photons depend on such parameters as the surface temperature, the rotational frequency, and the magnetic moment. It is demonstrated that both the GeV and TeV emissions of Geminga will be harder than those of B1055-52, B0656+14, and Vela, and that the TeV fluxes are too small to be observed by current ground-based telescopes.
Observations of the Chemistry in Circumstellar Disks
Authors: Dutrey A. , Guilloteau S. , Guélin M.
Published: July 2016

Circumstellar disks around classical T Tauri stars have still large amounts of primary molecular gas and dust, which may evolve to form planetary systems. Although it is the remnant of the parental cloud, the gas component shows significant chemical evolution. Fundamental disk properties (kinematics, size, temperature profile) can be derived from observations of CO lines with mm arrays. Less abundant molecules have been discovered with the IRAM 30-m telescope, in the DM Tau and GG Tau disks. Despite the high depletion factors which are measured with respect to the nearby Taurus cloud, these molecules allow independent measurements of the disk density. These observations provide an overview of the properties of young (a few Myr) proto-planetary disks around low-mass stars as seen by current mm instruments.
The Atmospheric Composition of the Giant Planets: Recent Discoveries from ISO and Galileo
Authors: Lellouch Emmanuel
Published: July 2016

The recent, concommitant, operation of the Galileo mission to the Jovian system and of the Infrared Space Observatory has provided a wealth of new results on the atmospheric composition of the Giant Planets. These results include (i) first or improved measurements of several elemental and isotope ratios, particularly in Jupiter; (ii) new insights into Jupiter's (and Saturn's) condensible species and tropospheric cloud structure; (iii) a much enriched view of stratospheric hydrocarbon chemistry; and (iv) the discovery of an external source of oxygen into the Giant Planets. These discoveries address key issues such as the origin of Giant Planets, their tropospheric meteorology and stratospheric physico–chemistry and dynamics, and their interaction with the interplanetary medium.
The Galactic Evolution of Boron
Authors: Primas Francesca
Published: July 2016

Boron, together with lithium and beryllium, belongs to the group of the so-called light elements, the importance of which ranges from providing important tests to Big Bang nucleosynthesis scenarios to being useful probes of stellar interiors and useful tools to further constrain the chemical evolution of the Galaxy.

Since it became operative in the late eighties, the Hubble Space Telescope (HST) and its high- and medium-resolution spectrographs have played a key role in analyzing boron. Boron has now been observed in several stars and in the interstellar medium (ISM), providing important information in different fields of astrophysical research (nucleosynthesis, cosmic-ray spallation, stellar structure). In particular, determinations of boron in unevolved stars of different metallicity have allowed to study how boron evolves with iron.

After a general review of the current status of boron observations and of the major uncertainties affecting the measurements of its abundance, I will mainly concentrate on unevolved stars and discuss the ‘evolutionary’ picture emerging from the most recent analyses and how its interpretation compares with theoretical expectations. A brief discussion on future prospects will conclude this contribution, showing how the field may evolve and improve.
IR Boron Lines in Stellar Spectra
Authors: Meléndez J , Castilho B. V. , Barbuy B
Published: July 2016

We have computed synthetic spectra of the infrared B I transitions at 1.166 and 1.624 μm in order to examine the possibility of abundance determination by using these lines. We found that the IR boron lines are better observed in cool giants and supergiants. S/N > 150 and R ≈ 60000 are required in order to determine the boron abundances.
The Nuclear Structure of the Giant Radio Galaxy 3C236
Authors: Tian W.W. , Schilizzi R.T. , Nan R.
Published: July 2016

We present the nuclear structure of the radio galaxy 3C236 obtained by VLBI and MERLIN observations at both 1.663 and 5 GHz. Comparison with an HST WFPC-2 image of 3C236 suggests that the radio axis is at an angle of ∼ 30° to the plane of the sky, and 3C236 has an overall size of 4.5 Mpc and contains the longest jet known in the universe.
Complete Alpha-Tensor for Solar Dynamo
Authors: Krivodubskij V.N. , Schultz M.
Published: July 2016

We applied the results of recent derivations of the α-effect to the solar convection zone model by Stix (1989) to find the depth and latitude dependences of the α-tensor. Pronounced inhomogeneity and anisotropy are revealed: the α-coefficients for different directions are quite different and strongly latitude-dependent.
Enhancement of Magnetic Fields in High-Gravity Stars Due to an Intrinsic Dynamo Effect
Authors: Engelhardt Dieter , Bues Irmela
Published: July 2016

A model of a local magnetic field within a white dwarf is constructed by the use of quantum statistics. The polarized Fermi, Bose and Maxwell statistics is calculated within a Heisenberg magnetism model by the use of Jones calculus. With a mesoscopic description the quantum mechanical dynamo can be discussed. The result is an efficient excitation mechanism, based on Lorentz time transformations and magnetic interactions. An Ap star as progenitor of a polarized white dwarf may loose its field and can generate a stronger one due to an intrinsic dynamo on a time scale of 107 years.
Hydromagnetic Dynamo in Astrophysical Jets
Authors: Shukurov A. , Sokoloff D.D.
Published: July 2016

The origin of a regular magnetic field in astrophysical jets is discussed. It is shown that jet plasma flow can generate a magnetic field provided the streamlines are helical. The dynamo of this type, known as the screw dynamo, generates magnetic fields with the dominant azimuthal wave number m = 1 whose field lines also have a helical shape. The field concentrates into a relatively thin cylindrical shell and its configuration is favorable for the collimation and confinement of the jet plasma.
Simultaneous Observations of the Continuum Emission of the Quasar 3C 273 from Radio to γ-Ray Energies
Authors: Lichti G. G. , Balonek T. , Courvoisier T. J.-L , Johnson N. , McConnell M. , von Montigny C. , Paciesas W. , Robson E. I. , Sadun A. , Schalinski C. , Smith A. G. , Staubert R. , Steppe H. , Swanenburg B. N. , Turner M. J. L. , Ulrich M.-H , Williams O. R.
Published: July 2016

From June 15 to 28, 1991 the Compton Gamma-Ray Observatory (CGRO) observed the radio-loud quasar 3C 273. All four CGRO instruments detected radiation from this quasar in their relevant energy range (from 20 keV to 5 GeV). Simultaneous and quasi-simultaneous observations (spanning the time period May 27 – July 25, 1991) by instruments sensitive at other wavelengths have also been obtained. The data from all these observations spanning the frequency range from ∼ 109 Hz to ∼ 1026 Hz were collected and analysed. The resulting energy-density spectrum is shown in the figure below. It shows two maxima, one in the UV, another one at low-energy γ-rays which have nearly the same strength (the corresponding luminosities per decade of frequency for H0 = 60(km/s)/Mpc are 3.2·1046 erg/s and 2.7·1046 erg/s, respectively). A break of the spectrum at low-energy γ-rays is evident. From a detailed analysis a break energy of (2±1.5) MeV could be derived corresponding to a frequency of (4.8±3.6)·1020 Hz. The observed spectral break between X- and γ-rays is ∼ 0.8, much higher than the value of 0.5 predicted by some models. A more detailed paper on this topic is in preparation (Lichti et al.).
X-ray Loud AGN with Optical Starburst or Seyfert 2 Properties
Authors: Bade N. , Schaeidt S.
Published: July 2016

The Hamburg Sternwarte is conducting a large area identification program of ROSAT All Sky Survey (RASS) sources on objective prism plates taken with the Schmidt telescopes on Calar Alto and La Silla (Bade et al., 1992, MPE-Report 235, 377). With follow-up observations redshifts and a more detailed classification of the emission line spectrum of 284 AGN were derived until August 1992.
The Recent Lightcurve of 3C 345
Authors: Schramm K.J. , Borgeest U. , Linde J. V. , Wagner S.J. , Heidt J.
Published: July 2016

We present the lightcurve of 3C 345 (1641+399, z = 0.595) in Johnson R. The data until summer 1992 are analysed and discussed in detail in Schramm et al. (A&A, Nov. 1993). The more recent lightcurve is almost flat (R ≃ 16.9), giving new constraints on variability models, see Camenzind, this proceedings.
MERLIN Observations of Seyfert Nuclei
Authors: Pedlar A. , Kukula M.J.
Published: July 2016

Radio emission from Seyfert nuclei appears to be intimately related to narrow line region (NLR) of ionised gas. Both regions have an extent of a few hundred parsecs corresponding to typically a few arcsec, and are only marginally resolved by ground based observations. HST and adaptive optics are giving optical images of the ionised gas with angular resolutions of order 0.1″. It is essential that high quality radio images are available with similar resolution so that models relating the two regions can be tested. The extended MERLIN is ideally suited for this task. It has angular resolutions of 0.05″ at 5GHz and 0.13″ at 1.5GHz and sensitivities of a few 10s of μJy. In this contribution we shall summarise the results on two objects.
Do Luminous QSOs Have Softer UV Spectra?
Authors: Köhler Thorsten
Published: July 2016

We present a comparison of well defined continuum slope distributions for QSOs found in the LBQS (Chaffee, F.H. et al. 1991, Astron. J., 102, 461 and references therein) and in the Hamburg–ESO–survey (hereafter HES) (Reimers, D. 1990, The messenger 60, 13).
II. The Galaxy
Authors: Larsson-Leander G.
Published: July 2016

The nuclear region may be explored by means of both radio and optical data. Optical methods include surveys of variable stars and various other objects, but of special interest are measurements in the far infra-red, which may provide a connexion between optical and radio observations.
A Study of the Angle of Repose of Some Loose Materials and its Bearing on the Hypothesis of a Dust Layer on the Lunar Surface
Authors: Orlova N. S.
Published: July 2016

Among the numerous hypotheses to explain the observed peculiarities of the outer layer of the lunar surface, some consider this layer to consist of loose material of volcanic ashes or dust. The basic objection to this view is the fact that such a layer of loose material cannot give a microstructure of the surface that would correspond to the law of the reflection of light from the lunar surface which follows from the observations. The scattering diagram of illuminating rays for a given area of the lunar surface, at all angles of incidence, is known to be very elongated in the direction of the light source. This is illustrated in Fig. 1, where the average scattering diagrams for the lunar maria are plotted for the angles of incidence of lighti= 0°, 30°, 60°. Experiments show that such diagrams can be reproduced only by those formations the surfaces of which are thickly covered by deep depressions with steep walls and sharp edges. Loose material cannot be maintained on surfaces with great angles of repose and, consequently, is capable of producing unevenness only on the slopes.
Thermal Radio Emission of the Moon and Certain Characteristics of its Surface Layer
Authors: Salomonovich A. E.
Published: July 2016

In order to use the data on the radio emission of the Moon as a basis for conclusions regarding the characteristics of the surface layer of the lunar crust, additional data or assumptions about the properties of this layer are necessary. The use of high-resolution radio telescopes reduces to a certain extent the unavoidable arbitrariness in the selection of parameters. Observations with the 22-m radio telescope of the Physics Institute, Academy of Sciences, made it possible to evaluate certain characteristics of the surface layer without relying entirely on optical data.
Intensity variations in the solar extreme ultraviolet spectrum observed by OSO-I
Authors: Neupert Werner M.
Published: July 2016

This paper reviews solar extreme ultraviolet observations made in the spectral region λ170 — λ400 by the first Orbiting Solar Observatory during March, April, and May, 1962. Application of the data to the identification of emission lines in this spectral region is discussed. The observations are compared with concurrent 2800 MHz radio emission and other measurements of solar activity.
Spotty appearance of the solar disk as inferred from the comparaison between EUV and radio intensities
Authors: Suemoto Z. , Moriyama F.
Published: July 2016

This is a revised version of the work reported to the COSPAR Symposium of 1962. In the first place, the basic components of the radio intensities ranging from 1000 MHz to 9400 MHz derived by H. Tanaka were used to establish the relation between the electron temperature and integrated number of electrons for 1960 and 1961 flights. The result justifies our former assumption that the radio intensities with which the EUV line intensities from the transition layer are to be compared should, as a first approximation, be very close to those at sunspot minimum.

In the second place, the integrated numbers of electrons from the EUV line intensities were derived based on the same data as were used by Pottasch. This is to eliminate any arbitrariness in adopting parameters which are still uncertain.

The result is that we still have a large amount of disagreement between the two sets of intensities in the sense that EUV line intensities are at least ten times stronger as might be inferred from the radio intensities. If one assumes an inhomogeneous model in which the solar disk is bright only in patches covering about 0.15 of its total area, the discrepancy would be eliminated.
Observational results of X-Ray astronomy
Authors: Bowyer Par S. , Byram E. T. , Chubb T. A. , Friedman H.
Published: July 2016

Ten discrete sources of X-rays have been identified from observations made with Geiger counters aboard unstabilized Aerobee rockets. The distribution of sources is flattened toward the galactic plane. Tau XR-1 is an X-ray source within one arc minute of the center of the Crab Nebula and of angular diameter one arc minute as determined from observation of a lunar occultation. The position of the strongest source, Sco XR-1, is known to about 0.5 degree and the remaining eight sources to about 1.5 degree. Three X-ray sources, Sco XR-1, Cyg XR-1, and Cyg XR-2, are not accompanied by any known optical or radio objects at their positions. Oph XR-1 matches the position of the Kepler SN 1604 and Sgr XR-1 is within 2.3 degrees of Sgr A. The remaining five sources are not sufficiently well resolved or positioned to permit identifications with optical or radio sources. The X-ray flux from the Crab Nebula is compatible with synchrotron spectrum with index — 1.1 and the flux of 1.8 × 10-8 erg cm-2 s-1 (1.5-8 Å) fits the extrapolated optical synchrotron spectrum with the same index.
Origin of Giant Radio Pulses
Authors: Istomin Ya. N.
Published: July 2016

A model for the origin of giant radio pulses is suggested. Radio emission is generated by the electric discharge taking place due to the magnetic reconnection of field lines connecting the opposite magnetic poles. The reconnection occurs in the region of the light cylinder near the zero line of the magnetic field. The coherent mechanism of radiation is pure maser amplification of Alfvén waves. The radiated frequencies are found.
Chromospheric Heating and CO Simulations
Authors: Uitenbroek Han
Published: July 2016

The solar chromosphere is a very dynamic and highly structured environment. In contrast to the higher density hydrodynamically controlled photosphere, this environment is controlled by magnetohydrodynamic forces. The lower density chromosphere encompasses the transition from optically thick to thin so that Non-LTE radiative transfer applies. While the omni-presence of emission in UV lines indicates that a chromospheric rise in temperature from the cool photosphere to the hot corona should occur everywhere on the solar surface, the presence of cool material at chromospheric heights observed in infrared CO lines has made us reconsider the validity of using this interpretation of the observed spectrum based on average one-dimensional models for chromospheric thermal structure. It can be shown that the mean thermal properties of spatially inhomogeneous and/or time-dependent atmospheres in fact are not well represented by an average one-dimensional semi-empirical model based on the mean spectrum. Observations of CO lines show that the coolest locations in the upper photosphere/lower chromosphere are associated with the strong adiabatic expansion that occurs over granules. Simulations that try to model chromospheric dynamics should therefore probably include the effects of solar convection, wave dynamics, as well as the effect of radiative cooling in the multitude of infrared CO lines on the thermal balance of the atmosphere.
Radio Emission from the Sun and Stars: New Insights into Energetic Phenomena
Authors: Bastian T. S.
Published: July 2016

Energetic phenomena on the Sun and late-type stars pose a number of fascinating puzzles. These include coronal heating, flares, and coronal mass ejections, all believed to be manifestations of magnetic energy release. Radio radiation is a sensitive tracer of energetic phenomena on both the Sun and stars. Radio observations of the Sun over the past decade have produced new insights into the physics of magnetic energy release in flares and coronal mass ejections. Radio observations of late-type stars have exploited sensitive imaging and spectroscopic techniques to further constrain the nature of the relevant emission mechanisms. A surprise has been the recent discovery of radio emission from brown dwarf stars, implying the existence of substantial magnetic fields and a means of dissipating magnetic energy, neither of which are understood.
The Solar Tachocline: Limiting Magneto-Tipping Instabilities
Authors: Cally P. S. , Dikpati M. , Gilman P. A.
Published: July 2016

Two dimensional magneto-shear instabilities in the solar tachocline have been extensively explored in recent years. One of their most notable traits over a wide range of shear and magnetic profiles is a propensity for the magnetic field to tip substantially from its initial axisymmetric configuration, with possible implications for patterns of flux emergence. However, it is found that modifications of the standard models to include either kinetic and magnetic drag, or prograde toroidal velocity jets associated with magnetic bands, can suppress the instabilities, or considerably reduce their nonlinear development. In the case of tip reduction by jets, for a toroidal field of around 100kG in the tachocline (required for sunspots to emerge in sunspot latitudes), simulations indicate that jets capable of reducing tipping below the limits of detection from sunspot patterns at the surface are potentially detectable by helioseismic methods, and should be looked for. Establishing an upper limit to the jet may result in a lower limit for the amount of tipping to be expected.
Evidence for Halo Microlensing from a Survey of M31
Authors: Crotts Arlin P. S. , Uglesich Robert R. , Baltz Edward A. , de Jong Jelte , Boyle Richard P. , Corbally Christopher J.
Published: July 2016

We report on the final microlensing result from one survey (VATT/Columbia) monitoring stars in M31, and the initial results of a larger study (MEGA), which together seem to indicate the presence of a microlensing halo component comprising a significant fraction of the dark matter in M31.
Cold Molecular Gas as a Possible Component of Dark Matter in the Outer Parts of Disk Galaxies
Authors: Allen Ronald J. , Diaz-Miller Rosa
Published: July 2016

In the last few years new evidence has been presented for the presence of ongoing massive star formation in the outer HI disks of galaxies. These discoveries strongly suggest that precursor molecular gas must also be present in some physical state which is escaping detection by the usual means (CO(1-0), IR, etc.). We present a model for such a gas in a framework which views the HI as the result of an ongoing “photodissociation ↔ dust grain reformation” equilibrium in a cold, clumpy molecular medium with a small area filling factor.
A Survey of Recent Magnetic Field Measurements in HI Features of the Galaxy
Authors: Heiles Carl
Published: July 2016

More than 300 measurements of magnetic field strengths in H I regions now exist. Interpretation of about 100 shows that magnetic pressure either is comparable with or dominates other pressures near at least some dark clouds and in at least some H I shells. There appears to be direct evidence for Alfvén waves, but this needs to be confirmed by additional examples. In many regions the field is highly uniform, but in other regions it varies considerably over 30 arcminutes or less. The field directions derived from Zeeman splitting and from Faraday rotation do not correlate well.
Spontaneous Discontinuities in Galactic Magnetic Fields and the Creation of Galactic X-ray Halos
Authors: Parker E. N.
Published: July 2016

The magnetic field in the gaseous disk of the galaxy is dynamically unstable to undulations with wavelengths of the order of 1 kpc. The elevated portions of the field are subject to rapid inflation (~ 50 km/sec) by the cosmic rays produced within the gaseous disk. The result is a magnetic halo of 1–3 × 10−6 gauss, composed of close packed bipolar lobes of field extending outward from the surface of the disk to distances of several kpc. The inflation is presumably irregular, producing tangential discontinuities (current sheets) throughout the extended bipolar fields. A major portion of the magnetic energy is dissipated by rapid reconnection at these current sheets, heating the tenuous halo gas to temperatures of 106 − 107 °K and producing the X-ray emission observed from the halos of many spiral galaxies.
Magnetic Production of Extragalactic Jets
Authors: Camenzind M.
Published: July 2016

Relativistic jets are formed by plasma injected into the rapidly rotating magnetosphere of accretion disks. The accretion disk generates a dipolar or a quadrupolar magnetosphere which also immerses the black hole. We present self-consistent solutions for the structure of this magnetosphere based on the Grad-Schlüter-Shafranov equation for the poloidal magnetic flux. The resulting supermagnetosonic jets consist of a nested family of magnetic surfaces filled with normal plasma flowing along the rotational axis of the central object.
Comparison of Radio and Optical Polarization in Extended Extragalactic Radio Sources: II. Implications for the Magnetic Fields
Authors: Meisenheimer K. , Röser H.-J.
Published: July 2016

Although optical synchrotron light from an extragalactic source - the jet in M 87 - has been discovered more than 30 years ago (Baade 1956) there are still only a handful extended radio sources with established optical synchrotron emission (see Röser 1989 and references therein, also Meisenheimer et al. 1989b). We outline the relevance of optical studies and summarize some results concerning the magnetic fields in extragalactic radio sources.
The Strength and Structure of the Intracluster Magnetic Field in the Coma Cluster of Galaxies
Authors: Kim K.-T. , Kronberg P. P.
Published: July 2016

A new series of detailed observations of the Coma cluster of galaxies has been undertaken with the aim of better specifying the intracluster gas component throgh high dynamic range, combined-telescope observations of the radio halo emission from the cluster which detect both the cluster-scale and galaxy-scale emission. By combining these multi-frequency maps with a Faraday rotation probe experiment using cluster and background sources, and the published X-ray data, we have been able to estimate the intracluster magnetic field strength independently of the unusal assumption of equipartition. The result is approximately 2 microgauss and the tangling of the rms field occurs on an optical galaxy scale.
Phase Offset of Rotation-Powered X-ray Pulsars
Authors: Wang H. G. , Qiao G. J. , Xu R. X.
Published: July 2016

Combing the data of all the 10 rotation-powered pulsars that have measurements of relative phase of radio and X-ray pulses, we report here the behavior of radio/X-ray phase offset. We find that the radio/X-ray offset of normal pulsars does not show the trend of increase with increasing pulsar period as the radio/gamma-ray offset exhibits. The offset of millisecond pulsars is generally much less than that of the normal pulsars. Such phenomenon should also be taken into account by the high energy models for pulsars.
Physics and Results from the AMANDA-II High Energy Neutrino Telescope
Authors: Barwick Steven W. ,   the AMANDA Collaboration, Ahrens J. , Bai X. , Barwick S. W. , Becka T. , Becker K.-H. , Bernardini E. , Bertrand D. , Binon F. , Biron A. , Böser S. , Botner O. , Bouhali O. , Burgess T. , Carius S. , Castermans T. , Chirkin D. , Conrad J. , Cooley J. , Cowen D. F. , Davour A. , De Clercq C. , DeYoung T. , Desiati P. , Dewulf J.-P. , Doksus P. , Ekström P. , Feser T. , Gaisser T. K. , Ganupati R. , Gaug M. , Geenen H. , Gerhardt L. , Goldschmidt A. , Hallgren A. , Halzen F. , Hanson K. , Hardtke R. , Hauschildt T. , Hellwig M. , Herquet P. , Hill G. C. , Hulth P. O. , Hultqvist K. , Hundertmark S. , Jacobsen J. , Karle A. , Köpke L. , Kowalski M. , Kuehn K. , Lamoureux J. I. , Leich H. , Leuthold M. , Lindahl P. , Madsen J. , Mandli K. , Marciniewski P. , Matis H. S. , McParland C. P. , Messarius T. , Minaeva Y. , Miočinović P. , Morse R. , Nahnhauer R. , Neunhöffer T. , Niessen P. , Nygren D. R. , Ogelman H. , Olbrechts Ph. , de Los Heros C. Pérez , Pohl A. C. , Price P. B. , Przybylski G. T. , Rawlins K. , Resconi E. , Rhode W. , Ribordy M. , Richter S. , Martino J. Rodríguez , Ross D. , Sander H.-G. , Schinarakis K. , Schmidt T. , Schneider D. , Schwarz R. , Silvestri A. , Solarz M. , Spiczak G. M. , Spiering C. , Steele D. , Steffen P. , Stokstad R. G. , Sudhoff P. , Sulanke K.-H. , Taboada I. , Thollander L. , Tilav S. , Wagner W. , Walck C. , Wiebusch C. H. , Wiedemann C. , Wischnewski R. , Wissing H. , Woschnagg K. , Yodh G. , Young S.
Published: July 2016

This paper briefly describes the principle of operation and science goals of the AMANDA high energy neutrino telescope located at the South Pole, Antarctica. Results from an earlier phase of the telescope, called AMANDA-BIO, demonstrate both reliable operation and the broad astrophysical reach of this device, which includes searches for a variety of sources of ultrahigh energy neutrinos: generic point sources, Gamma-Ray Bursts and diffuse sources. The predicted sensitivity and angular resolution of the telescope were confirmed by studies of atmospheric muon and neutrino backgrounds. We also report on the status of the analysis from AMANDA-II, a larger version with far greater capabilities. At this stage of analysis, details of the ice properties and other systematic uncertainties of the AMANDA-II telescope are under study, but we have made progress toward critical science objectives. In particular, we present the first preliminary flux limits from AMANDA-II on the search for continuous emission from astrophysical point sources, and report on the search for correlated neutrino emission from Gamma Ray Bursts detected by BATSE before decommissioning in May 2000. During the next two years, we expect to exploit the full potential of AMANDA-II with the installation of a new data acquisition system that records full waveforms from the in-ice optical sensors.
Rotational Velocities of S-Type Symbiotic Stars
Authors: Fekel Francis C. , Hinkle Kenneth H. , Joyce Richard R.
Published: July 2016

We obtained high-resolution spectroscopic observations at 2.226 μm of 13 S-type symbiotic binaries using the Phoenix infrared spectrograph on Kitt Peak telescopes. from an empirical calibration we determined v sin i values for the giant components. Combined with information from a program to determine orbits, the rotational velocities have been used to estimate the sizes of these stars and the fraction of their Roche lobes that they fill.
Winds and Outflows in Starburst Galaxies and AGN
Authors: Komossa Stefanie , Hasinger Günther , Schulz Hartmut
Published: July 2016

Winds and outflows in starburst galaxies and AGN provide important information on the physics of the ‘central engine’, the presence and evolution of (nuclear) starbursts, and the metal enrichment of the nuclear environment and the intergalactic medium. Here, we concentrate on two examples, X-ray observations of the (U)LIRG NGC 6240 and the BAL quasar APM 08279+5255.
Spiral Galaxy - ICM Interactions in the Virgo Cluster
Authors: Kenney Jeffrey D. P. , Crowl Hugh , van Gorkom Jacqueline , Vollmer Bernd
Published: July 2016

We discuss HI and optical evidence for ongoing ICM-ISM interactions in 6 Hi-deficient Virgo cluster spiral galaxies. One of the clearest cases is the highly inclined Virgo galaxy NGC 4522, which has a normal stellar disk but a truncated gas disk, and lots of extraplanar gas right next to the gas truncation radius in the disk. Unusually strong HI, Hα and radio continuum emission are all detected from the extraplanar gas. The radio continuum polarized flux and spectral index peak on the side opposite the extraplanar gas, suggesting ongoing pressure by the ICM. Four other HI-deficient edge-on Virgo spirals show evidence of extraplanar ISM gas or exhibit asymmetries in their disk HI distributions, but contain much less extraplanar HI than NGC 4522. Comparison with recent simulations suggests this difference may be evolutionary, with large surface densities of extraplanar gas observed only in early phases of an ICM-ISM interaction. In NGC 4569, the Hα image shows 2 effects of ICM pressure on the galaxy ISM. An anomalous arm of HII regions, possibly extraplanar, emerges from the edge of a truncated Hα disk. This resembles the arms seen in simulations which are formed by the combined effects of wind pressure plus rotation. An extended nebulosity near the minor axis, also in the NW, is interpreted as a starburst outflow bubble disturbed by ICM wind pressure.
CONFERENCE SUMMARY
Authors: Mould J. R.
Published: July 2016

It is traditional to begin a review on the subject of the Magellanic Clouds with a discussion of the distance of the Clouds. Feast did this in his introductory remarks to the meeting, and I shall not resist the temptation to reflect a little on this subject. At the Tubingen meeting we gave some thought to a new controversy between a (short) distance modulus of 18.2 for the LMC and the more traditional (Long) distance of 18.7. The short distance was primarily the result of main sequence fitting to LMC clusters resulting from new CCD photometry. A consensus has arisen since that time, and is represented at this meeting by results presented by Walker and Caldwell, and earlier by Reid and Strugnell (1986) and recently by Jacoby et al. (1990), that the best value of (m-M)o is 18.45±0.15 for the LMC (which is also the average of the short and long values). This is obtained, however, by given low weight to (firstly) recent work on the absolute magnitude of RR Lyrae stars based on the Baade-Wesselink technique and (secondly) the aforementioned main sequence fitting results
The starburst region 30 Doradus
Authors: Walborn Nolan R.
Published: July 2016

The 30 Doradus region of the LMC is a Rosetta Stone for the interpretation of similar, more distant regions, since it is accessible to spatially resolved investigation of its components with modern instrumentation. Following an introductory review of the various scales and populations relevant to the region, several current programs which promise improved understanding will be reviewed. They include extensive new optical spectroscopy and photometry of the central cluster, which will provide substantial new information about the stellar content and initial mass function (IMF); infrared surveys which will clarify questions about continuing star formation and the lower main sequence; and high-resolution nebular spectroscopy and X-ray observations which will reveal the high-energy phenomena in the surrounding interstellar medium.
CO observations of the 30-Doradus region using SEST
Authors: Booth R. S. , Johansson L.E.B.
Published: July 2016

Using the Swedish-ESO Submillimetre Telescope, we have mapped the CO (1-0) emission in two small areas of the LMC near 30 Dor. Some 20 molecular clouds have been identified and analysed. Cloud masses are calculated assuming virial equilibrium and the relationship between mass and CO luminosity is discussed.
Observations of two different cluster types in the LMC
Authors: Linde P. , Lyngå G. , Westerlund B. E.
Published: July 2016

The aim of our project is to study the star-formation history in open clusters and field stars in two regions on either side of the bar of the Large Magellanic Cloud (LMC). In a forthcoming paper we shall describe the observations and the characteristics of the clusters. Here, we summarise the results of the BV photometry of three of the cluster fields: LW 55 (4h46.m6, −73°30'), HS 96 (5h03.m4, −65°57') and SL 196 (5h03.m6, −65°54', epoch 1950). They were all observed with an RCA CCD at the 2.2-m telescope at La Silla.
Shapes of Magellanic Cloud star clusters
Authors: Kontizas E. , Kontizas M. , Sedmak G. , Smareglia R.
Published: July 2016

The ellipticities of the most populous MC star clusters (87) have been derived for studying a) ellipticity variations within individual clusters, b) variations of ellipticity distributions for various galaxies, and c) variations of ellipticity of star clusters relative to their dynamical parameters.

From the studied clusters it is found that radial ellipticity variations within individual clusters seem to be a common phenomenon for the MC clusters where the inner parts are more elliptical than the outer. The SMC clusters are more elliptical than LMC clusters where ellipticities are measured at rh.

The dynamical masses of the clusters seem to correlate with ellipticities where the most massive are the most elliptical.
Monitoring SN1987A at 45 MHz
Authors: Alvarez H. , Aparici J. , May J. , Olmos F.
Published: July 2016

Encouraged by a theoretical model we are monitoring supernova 1987A at 45 MHz in an attempt to detect its scintillation. So far the result is negative, but the program will continue.
Abundances and nebular and central star masses for Magellanic Cloud planetary nebulae
Authors: Walton N. A. , Barlow M. J. , Monk D. J. , Clegg R.E.S.
Published: July 2016

We present the results of a spectroscopic study of planetary nebulae (PN) in the Magellanic Clouds. The optical survey of He, N, O, and Ne abundances by Monk et al. (1988) has been updated by higher S/N AAT optical data. In addition, carbon and other elemental abundances have been derived from the IUE spectra of 38 PN. Ionized nebular masses have been derived for 80 PN. The ionised mass versus nebular electron density plot shows that planetary nebulae become optically thin when their electron densities drop below 4500 cm--3. Below this density, the mean nebular hydrogen mass found for non-Type I PN is 0.22±0.08 M⊙. Using Zanstra and energy-balance methods, the mean central star mass found for 14 SMC and LMC PN is 0.59±0.02 M⊙.
Australia Telescope observations of the supernova remnant N49 in the LMC
Authors: Junkes Norbert
Published: July 2016

We present the first high-resolution radio image of the supernova remnant N49 near the northern edge of the LMC. These observations with the Australia Telescope at 6cm wavelength (4 arcsec resolution) show a distinct radio shell. The shell structure of N49 is similar in radio and X-ray emission, with the maximum of the emission found in the southeastern part of the SNR.
Enhanced galactic star formation as caused by the Milky Way - Large Magellanic Cloud interaction: an experience from density wave studies
Authors: Marochnik L. S. , Suchkov A. A.
Published: July 2016

Star formation in interacting galaxies is usually strongly enhanced. The star formation rate in the Milky Way is substantially greater than, for example, in the Andromeda Nebula. A plausible cause for this difference may be the interaction of the Milky Way with the Large Magellanic Cloud. We suggest that one of the possibilities for this may be the enhanced formation of cold gas clouds as the gas flows through the gravitational potential well of a tidal wave caused by the interaction; another contribution may come from compression of pre-existing clouds when they pass this way. This scenario is obviously quite similar to that envisioned in “frames” of the density-wave theory.
Optical surveys of the Magellanic Bridge, Stream and outer halos
Authors: Irwin M. J.
Published: July 2016

The HI envelope of the Magellanic System extends well beyond the obvious visible regions of each of the Clouds. Modern optical surveys based on UK Schmidt telescope plates and fast measuring machines are now starting to reveal the complex optical counterparts of some of these HI features.
Theoretical pulsation models for Long Period Variables
Authors: Tuchman Y.
Published: July 2016

Three issues, which are to my opinion the main obstacles in modeling the variability of Miras and Long Period Variables (LPVs), are presented and discussed:

a.

The initial static models - Possible influences of the evolutionary details, the helium shell flashes and the use of the core-mass luminosity relation.

b.

Modeling the convective energy transport - The mixing-length theory, its limitations and validity. First attempts for two-dimensional calculations of the convective flow in AGB stars.

c.

The surface conditions - Introduction to the main difficulties and uncertainties. What should be done in the future.

Finally, the ancient problem, concerning the mode of pulsation, in Miras, is discussed using the recent radii observations confronted with the results of our full non-linear calculations.
ISOCAM and DENIS Survey of 0.5 square degrees in the Bar of the LMC. Detection of the whole TP-AGB Star Population
Authors: Loup C. , Josselin E. , Cioni M.-R. , Habing H.J. , Blommaert J.A.D.L. , Trams N.R. , Groenewegen M.A.T. , Alard C. , Fouqué P. , Kerschbaum F. , Waters L.B.F.M. , van Loon J.Th. , Zijlstra A.A. ,   the DENIS consortium
Published: July 2016

We surveyed 0.5 square degrees in the Bar of the LMC with ISOCAM at 4.5 and 12 μm, and with DENIS in the I, J, and Ks bands. Our goal was to build a complete sample of Thermally-Pulsing AGB stars. Here we present the first analysis of 0.14 square degrees. In total we find about 300 TP-AGB stars. Among these TP-AGB stars, 9% are obscured AGB stars (high mass-loss rates); 9 of them were detected by IRAS, and only 1 was previously identified. Their luminosities range from 2 500 to 14 000 L⊙, with a distribution very similar to the one of optical TP-AGB stars (i.e. those with low mass-loss rates). Such a luminosity distribution, as well as the percentage of obscured stars among TP-AGB stars, is in very good agreement with the evolutionary models of Vassiliadis & Wood (1993) if most of the TP-AGB stars that we find have initial masses smaller than 1.5 to 2 M⊙.
The Relative Source-Lens Proper Motion in MACHO 98-SMC-1 from Observations by the PLANET Collaboration
Authors: Menzies J. ,   PLANET Collaboration
Published: July 2016

Following an alert by the MACHO group, the PLANET collaboration has made detailed follow-up observations of the microlensing event in the SMC, MACHO 98-SMC-l. The lens is a binary and in consequence it is possible to obtain the relative source-lens proper motion as the source crosses a caustic. Two acceptable models have been found to describe the source-lens configuration, both of which suggest that the lens cannot be in the halo of the Galaxy, but is most likely in the SMC itself.
Properties of Wolf-Rayet stars from X-ray to radio data
Authors: Willis Allan J.
Published: July 2016

This review outlines the impact of observations across the spectrum (X-rays to radio) on our understanding of the basic physical, chemical, wind and mass loss properties of Wolf-Rayet stars. Optical spectropolarimetry indicates that ∼ 15% of the WR stars have anisotropic winds, whilst the majority have globally spherically symmetric outflows. All WR stars probably have winds structured (clumped) on the smaller scale as evidenced from: thermal radio spectral indices, optical-UV continuum/line/polarisation variablity and time-series spectroscopy, and the ubiquity of wind X-ray emission. ROSAT results indicate LX(WR) = 1031–33 ergs−1 with kT ≃ 0.3keV. WR mass loss rates may be lower than previously thought: mean, clumping-corrected rates from radio data yield M(WN) ≃ 3 × 10−5 M⊙ yr−1 and M(WC) ≃ 2 × 10−5 M⊙ yr−1. Analyses of UV-optical-IR spectra lead to good constraints on Teff and L/L⊙ and confirm the chemical separation of the WN and WC classes: WN stars show H-He-C-N abundances reflecting CNO-burning products, and WC(WO) stars show He-burning products. ISO data are confirming the H-deficiency of WC winds, and reveal a substantially enhanced Neon abundance in WC stars.
The neon abundance in WC stars. II. ISO-SWS spectroscopy of WR 90 (HD 156385)
Authors: Dessart Luc , Willis Allan J. , Crowther Paul A. , Morris Patrick W. , Hillier D. John
Published: July 2016

In general, observationally derived wind compositions of WR stars are in reasonable agreement with predictions from stellar evolution models for massive stars. However, Barlow et al. (1988) identified a major discrepancy for neon in γ2 Vel (WC8+O) using ground-based observations. The advent of the ESA Infrared Space Observatory (ISO) has allowed the study of neon in many more WC stars, using mid-IR fine structure lines ([Ne II] 12.81 μm, [NeIII] 15.55μm and [NEV] 14.32 μm). Willis et al. (1998) used ISO-SWS observations of WR 146 (WC5+O) to derive a neon abundance that was within the range expected theoretically. Here we undertake a study of WR 90 (HD 156385), the only (apparently) single WC7 star in our Galaxy, using ISO-SWS spectroscopy. The only spectroscopic neon feature in the mid-IR of WR 90 is [Ne III] 15.55 μm, in addition to numerous C IV and He II transitions (see Figure 1).