bluuebunny/crossref_metadata_2025 huggingface dataset:
An X-ray Pulsar, Metal-rich Ejecta, and Shocked Ambient Medium in the Supernova Remnant G292.0+1.8
Authors: Hughes John P. , Friedman Robert B. , Slane Patrick , Park Sangwook
Published: July 2016

We report the discovery of pulsed X-ray emission from the compact object CXOU J112439.1-591620 within the Galactic supernova remnant G292.0+1.8 using the High Resolution Camera on the Chandra X-Ray Observatory. The X-ray period is consistent with the extrapolation of the radio period and spindown rate of PSR J1124−5916. The X-ray pulse is single peaked and broad. There is no optical counterpart to a limit of MV ∼ 26. The pressure in the pulsar wind nebula is considerably less than that in the reverse-shock-heated ejecta and circumstellar medium, indicating that the reverse shock has not yet begun to interact with the nebula.
LSI +61°303: A Pulsar Wind Nebula in a Binary?
Authors: Leahy D. A.
Published: July 2016

LSI +61°303 outbursts are modeled as a pulsar wind nebula expanding inside the environment provided by the Be companion star's stellar wind and photon flux. A set of equations describing the system is developed and solved numerically for representative sets of parameters. Emission in X-rays through gamma-rays is due to inverse Compton emission from relativistic electrons around the pulsar. The radio emission is due to synchrotron emission of varying optical depth, which yields a varying spectral index. The peak of X-ray emission is near periastron and the peak of the radio emission is near apastron, due to reduced confining pressure on the relativistic electron cloud and its subsequent rapid expansion.
Solid Bare Strange Quark Stars
Authors: Xu Renxin
Published: July 2016

The reason we need the terms “strange”, “bare” and“solid” before quark stars is presented concisely, although some fundamental issues are not certain. Observations favoring these stars are introduced.
Correlations Between X-ray and Radio Pulses in Vela
Authors: Donovan Jennifer , Lommen Andrea , Arzoumanian Zaven , Harding Alice , Strickman Mark , Gwinn Carl , Dodson Richard , McCulloch Peter , Moffett David
Published: July 2016

Pulse-shape changes correlating with flux have been shown to exist in the Vela pulsar's radio emission (Krishnamohan & Downs 1983). The aim of this work was to look for correlations between radio and X-ray flux in Vela on a pulse-by-pulse basis. We found that Vela emits significantly more X-rays during radio pulses with strong flux than during weak radio flux pulses, which indicates that the mechanisms creating the Vela pulsar's X-ray and radio emission must be related.
Reception of Radio Waves from Pulsars
Authors: Gangadhara R. T.
Published: July 2016

The beamed emission by relativistic sources moving along the magnetic dipolar field lines occurs in the direction of tangents to the field lines. To receive such a beamed radiation, the line of sight must align with the tangent within the beaming angle 1/γ, where γ is the particle Lorentz factor. By solving the viewing geometry, in an inclined and rotating dipole magnetic field, we show that at any given pulse phase the observer can receive the radiation only from specific altitudes. We find that the outer conal emission is received from higher altitudes than the inner conal components including the core. At any pulse phase, low frequency emission comes from the higher altitudes than higher-frequency emission. As an application of our model, we have used it to explain the emission heights of conal components in PSR B0329+54.
Electrodynamics of Pulsar Magnetospheres
Authors: Spitkovsky Anatoly
Published: July 2016

I review the theoretical understanding of the global structure of pulsar magnetospheres concentrating on recent progress in force-free electrodynamics and first-principles simulations of magnetospheres.
Long-term Radio Timing Observations of PSR B1509–58
Authors: Livingstone Margaret A. , Kaspi Victoria M. , Manchester Richard N.
Published: July 2016

We present an updated phase-coherent timing solution for the young, energetic pulsar B1509–58 from twenty years of data. Using a partially phase-coherent timing analysis, we show that the second frequency derivative is changing in time, implying a third frequency derivative of This value is consistent with the simple power law model of pulsar rotation.
Timing of Binary Pulsars at Kalyazin, Russia
Authors: Ilyasov Yu. P. , Oreshko V. V. , Potapov V. A. , Rodin A. E.
Published: July 2016

Regular high-precision timing of the binary pulsars J0613−0200, J1012+5307, J1022+1001, J1640+2224, J1643−1224, J1713+0747, J2145−0750 and the pulsar B1937+21 has been conducted at the Kalyazin (Russia) radio telescope RT-64 at 0.6 GHz over more than 6 years. Several of the pulsars monitored have been found to be good probes for gravitational wave background (GWB) tests, while others, having a shorter orbital period, can be used for establishing a dynamical binary pulsar timescale. Upper limits for the GWB energy density were estimated.
Flux Monitoring Using the Toruń 32-m Radio Telescope
Authors: Kijak J. , Gupta Y. , Lewandowski W. , Hrynek G. , Krzeszowski K.
Published: July 2016

We present flux density measurements for PSR B0329+54 at 4.8 GHz obtained during one year.
A New Population of X-ray Transients in the Galactic Center
Authors: Sakano Masaaki , Warwick Robert S. , Decourchelle Anne , Wang Q. Daniel
Published: July 2016

A comparison of the XMM-Newton and Chandra Galactic Center Surveys has revealed two faint X-ray transients with contrasting properties. The X-ray spectrum of XMM J174544−2913.0 shows a strong iron line with an equivalent width of ∼2 keV, whereas that of XMM J174457−2850.3 is characterized by a very hard continuum with photon index ∼1.0. The X-ray flux of both sources varied by more than two orders of magnitude over a period of months with a peak X-ray luminosity of 5 × 1034 ergs s−1. We discuss the nature of these peculiar sources.
The Solar-Stellar Connection and Disconnection
Authors: G. Strassmeier Klaus
Published: July 2016

The study of stellar activity is now an almost classical astronomical topic. The first Ca ii-H&K observations were made a hundred years ago by Eberhard & Schwarzschild1 and many thousand papers were published after its rediscovery some three decades ago by O. C. Wilson. The complexity of the atmospheric and interior magnetic activity as observed on the Sun is hard, if not impossible, to extrapolate to solar-type stars. So far there is no solar twin found, despite that it appears that just a single process acts as the driving mechanism for activity in all atmospheric layers and partially even in the convective envelope: the dynamodriven magnetic field. In this paper, I will try to give examples where the solar analogy holds and where it is clearly not appropriate, putting some emphases on differential surface rotation and meridional circulation. I stress the importance of mapping stellar surfaces as fingerprints of the underlying dynamo action and directly measure surface magnetic fields.
The Magnetic Corona: Magnetic Reconnection in Solar Flares
Authors: P. Warren Harry
Published: July 2016

The ability of the Transition Region and Coronal Explorer (TRACE) to image the Sun at high spatial resolution and high cadence over a very broad range of temperatures makes it a unique instrument for observing solar flare plasma. TRACE observations have confirmed the reconnection model for solar flares, at least qualitatively. TRACE flare observations show impulsive footpoint brightenings that are followed by the formation of high-temperature loops in the corona. These loops then cool to lower temperatures, forming post-flare loop arcades. Comparisons between TRACE and lower spatial resolution Yohkoh Soft X-Ray Telescope (SXT) observations have revealed that solar flares are composed of a multitude of fine coronal loops. Detailed hydrodynamic modeling of flare light curves shows that this fine scale structuring is crucial to understanding the evolution of the observed emission. Models based on single, isothermal loops are not consistent with the TRACE observations. Models based on the sequential heating of small-scale loops, in contrast, are able to reproduce many of the salient features of the observed light curves. We will discuss the implication of these results for more energetic stellar flares as well as smaller-scale events that may be responsible for the heating of solar active region loops.
Persistent Active Longitudes in Sunspot Activity: Sun-as-a-Star Approach
Authors: Berdyugina S. V. , Usoskin I. G.
Published: July 2016

Using a new Sun-as-a-star approach we analyze sunspot group data for the past 120 years and reveal that sunspots are formed preferably in two persistent migrating active longitudes 180° apart. Their migration is determined by changes of the mean latitude of sunspots and the surface differential rotation. The two active regions periodically alternate being the dominant region with a period of about 3.7 years similar to the “flip-flop” phenomenon known in starspot activity. The fact that the Sun shows the same pattern of magnetic activity as highly active stars strengthens the solar paradigm for magnetic activity on cool stars.
Magnetic Activity of Pre-main Sequence Stars
Authors: D. Feigelson Eric
Published: July 2016

I review here recent advances in our understanding of magnetic activity in pre-main sequence (PMS) protostars and T Tauri stars. Results are based on recent imaging, spectroscopic and temporal studies of nearby star forming regions from the Chandra X — ray Observatory and XMM — Newton, including a first look at an ultradeep Chandra exposure of the Orion Nebula Cluster.

Pre-main sequence stars exhibit a high level of X-ray emission dominated by a bewildering variety of magnetic reconnection flares. Activity is linked to bulk stellar properties — Lbol, mass, surface area or volume — rather than rotation. This suggests that dynamo processes in deeply convective PMS stars may fundamentally differ from the tachocline dynamo operating in main sequence stars.

X-rays and MeV particles from magnetic flares will affect the circumstellar environment in PMS systems, particularly the protoplanetary disk. X-ray emission may influence: disk ionization, turbulence and viscosity; Jovian planet formation and migration; the production of meteoritic isotopes and melting of meteoritic chondrules; the heating and chemistry of the disk. X-ray surveys are also effective in locating post-T Tauri stars for disk evolution studies.
Multi-Wavelength Observations of EV Lacertae
Authors: A. Osten Rachel , L. Hawley Suzanne , Allred Joel , Johns-Krull Christopher M. , Roark Christine , Ambruster Carol , Brown Alexander , R. Ayres Thomas , L. Linsky Jeffrey
Published: July 2016

We report on a large, multi-wavelength campaign to observe variability across the electromagnetic spectrum in the M dwarf flare star EV Lacertae, in 2001 September. The campaign involved X-ray (Chandra ACIS-S+HETG), UV (HST/STIS), and optical (McDonald) spectra, as well as optical photometry and multi-frequency radio (VLA) observations. EV Lac demonstrated both frequent and extreme variability during the course of the two day intensive recordings. Dispersed X-ray spectra confirm the metal underabundance seen in other active stars. The increase in continuum fluxes at short X-ray wavelengths during flare intervals compared to quiescent intervals signals the creation of high temperature plasma, a signature of the flare process. Multi-wavelength comparisons reveal interesting trends: X-ray flare frequencies are within the range predicted by optical observations, yet there is no correspondence between X-ray flares and optical flares in our data. Two UV flares occur during the rise stages of X-ray flares; a major radio flare is accompanied by a large optical flare, which has no apparent counterpart in the X-ray. The results give conflicting evidence for the applicability of the Neupert effect interpretation in stellar coronae.
Persistent Transition Region Emission in Very Low Mass Stars
Authors: L. Hawley Suzanne , Johns-Krull Christopher M.
Published: July 2016

We have obtained HST/STIS time series observations of active, very low mass stars of spectral types M7-M9. The observations comprise 15 consecutive exposures on each of the stars VB 8, VB 10, and LHS 2065. Emission is present in several transition region lines including Si IV, C IV and He II. The emission appears to be variable between exposures, but is always observed. A strong flare was observed in one exposure on VB 10. Our results suggest that active, very low-mass stars maintain a persistent quiescent chromosphere and transition region that is similar to those observed in active, earlier type M dwarfs. This contradicts the currently popular idea that very low mass stars exhibit only relatively strong flares and no quiescent emission.
Method for Spot-Detection on Solar-like Stars
Authors: R. Silva Adriana V.
Published: July 2016

As a planet eclipses its parent star, a dark starspot may be occulted, causing a detectable variation in the light curve. This work describes how features on the surface of a solar-like star can be studied by using planetary transits. Images of the Sun were used in order to simulate such transits, with the planet being modeled as a dark disk at various positions along its orbit. From modeling of these transits it might be possible to infer the physical properties of the spots, such as size, intensity, position, and temperature. Recent transits observations for HD 209458 were used as tests to the model. The results yield that the limb darkening of HD 209458 is not like that of the Sun, but rather follows a quadratic function. The dark features studied have radii varying between 3 — 6 104 km, and probably represent a group of spots, namely an active region. As for the temperature, these spots are hotter than sunspots with a temperature range of 4900-5500 K.
Active Region Loop Models and Observations
Authors: Landi E. , Landini M.
Published: July 2016

In the present work we compare CDS observations of active region loops and predictions from a steady-state theoretical model developed assuming different functional forms of steady-state loop heating. The present work shows that in no case agreement with observations is achieved, that filamentation is present, and that despite its limitation, CDS is a precious tool for loop physics.
SOHO/SUMER Results: Mass Flows
Authors: Peter Hardi
Published: July 2016

Hardly any part of the chromosphere and the low corona of the Sun is in a static state. Spectrographs reveal line shifts and nonthermal broadening indicating mass supply to the corona, draining of coronal material, syphon flows, wave propagation and more. Imaging instruments show apparent motions of bright or dark structures indicating the presence of flows and waves, too.

This paper will review recent observations of the EUV spectrometer SUMER onboard SOHO on Doppler shifts of lines from the transition region and low corona of the Sun. These results will be discussed with respect to the general picture(s) we have of the structure of the upper solar atmosphere.
Origin of the Solar Wind and Open Coronal Magnetic Structures
Authors: Habbal Shadia Rifai , Woo Richard
Published: July 2016

Identifying the regions of open magnetic structures in the corona, namely regions where field lines expand outwards into interplanetary space, is equivalent to establishing the origin of the solar wind at the Sun. A review of recent studies, based on the comparison of the distribution, as a function of latitude, of density and velocity in the inner corona and in interplanetary space, is presented. It is shown how, at solar minimum, this comparison leads to the unexpected result that the fast solar wind expands indiscriminately from a significant fraction of the solar surface, not limited to polar coronal holes, as has been believed for the past three decades. It is also shown how polarization measurements of coronal forbidden lines, which yield the direction of the coronal magnetic field, lend further support to this result. The implications of these findings are that a significant fraction of the solar magnetic field is primarily open, expanding almost radially into interplanetary space, carrying with it the imprint of the distribution of density in the corona, while the ‘closed’ structures contribute a small fraction to the overall filling factor of coronal density structures. Furthermore, the solar wind particle flux is found to be correlated with density, implying a higher mass loss rate from the higher density quiet Sun regions, and the likelihood of a solar cycle dependence in the mass loss rate, as the are of polar coronal holes decreases with increased solar activity.
Summary talk: How serious are the problems faced by CDM: cusps, thin disks, and halo substructure
Authors: Primack Joel R.
Published: July 2016

This is a summary of the discussion in Panel I of IAU Symposium 220 on Dark Matter in Galaxies. the panel topics and panellists were as follows – Cusps Theory: Julio Navarro; Cusps Observations: Erwin de Blok, Rob Swaters; Substructure Observations: Mario Mateo; Substructure Theory: James Taylor, Shude Mao. in addition to the talks by the panellists and the discussion among them, there was a good deal of discussion with the audience. Despite the differences of opinion expressed I think a consensus emerged, and I try to summarize it here.
The Kinematics in the Cores of Low Surface Brightness Galaxies
Authors: Swaters R. A. , Verheijen M. A. W. , Bershady M. A. , Andersen D. R.
Published: July 2016

Systematic effects on HI and Hα long-slit observations make a measurement of the inner slope of the dark matter density distribution difficult to determine. Halos with constant density cores and ones with r–1 profiles both appear consistent with the data, although constant density cores generally provide better fits. High-resolution, two-dimensional velocity fields remove most of the systematic effects, yet as a result of noncircular and random motions the inner slopes still cannot be accurately measured. Halo concentration parameters provide a more useful test of cosmological models because they are more tightly constrained by observations. the concentration parameters for LSB galaxies appear consistent with, but on the low end of the distribution predicted by CDM.
The dark matter content of lensing galaxies at 1.5 Re
Authors: Schechter Paul L. , Wambsganss Joachim
Published: July 2016

Many quasars that are gravitationally lensed exhibit flux ratio “anomalies” that cannot be explained under the hypothesis that the lensing potential is smooth on scales smaller than 1 kpc. Micro-lensing by stars is a natural source of granularity in the lens potential. the character of the expected fluctuations due to Micro-lensing depends sensitively on the relative surface densities of micro-lenses (stars) and smoothly distributed (dark) matter. Observations of flux ratios may therefore be used to infer the ratio of stellar to dark matter along the line of sight – typically at impact parameters 1.5 times the half light radius. Several recently discovered systems have anomalies that would seem to be explained by Micro-lensing only by demanding that 70-90% of the matter along the line of sight be smoothly distributed.
Early-type Galaxy Halo Dynamics inferred using the PN Spectrograph
Authors: Douglas N. G. , Romanowsky A. J. , Kuijken K. , Merrifield M. R. , Napolitano N. R. , Arnaboldi M. , Freeman K. C. , Capaccioli M. , Gerhard O.
Published: July 2016

A new instrument is providing crucial data with which to probe the structure of dark halos in elliptical galaxies
The Halo Mass Distribution of Field and Cluster Early-Type Galaxies
Authors: Bergmann Marcel P. , Forestell Amy , Gebhardt Karl , Jørgensen Inger
Published: July 2016

We describe an ongoing program to study the halo kinematics of a broad sample of early-type galaxies using integrated light measurements obtained with the Hobby-Eberly and Gemini Telescopes.
The dark halo in the elliptical galaxy NGC 3108
Authors: G. Józsa Gyula I. , Oosterloo Thomas A. , Morganti Raffaella , Vergani Daniela
Published: July 2016

We investigate the properties of the dark halo of the dust-lane elliptical galaxy NGC 3108. This galaxy contains a large massive gaseous disk, which shows rapid and regular rotation. That makes NGC 3108 a target for measurements usually feasible only for spriral galaxies. Combining spectroscopic measurements of the disk in the optical- and the radio regime, we provide a reliable rotation curve of the galaxy out to 3 Reff and show that the rotation curve does not decline up to a radius of 5.5 Reff corresponding to 28 kpc.
1.2 mm emission from Cen A
Authors: Banhidi Zita , Chini Rolf , Albrecht Marcus
Published: July 2016

Centaurus A is the closest active radio galaxy at a distance of around 3.5 Mpc. New 1.2 mm imaging performed with SIMBA at the Swedish ESO Submillimetre Telescope (SEST) in Chile gives an insight into the distribution of thermal and non-thermal emission. Apart from extended synchrotron emission in the radio lobes we have detected the unresolved AGN core and the characteristic dust lane.
Galaxy Formation and Baryonic Dark Matter
Authors: Combes Françoise
Published: July 2016

The ACDM scenario to form galaxies encounters many problems when confronted with observations, namely the prediction of dark matter cusps in all galaxies, and in particular in dwarf irregulars, dominated by dark matter, or the low angular momentum and consequent small size of galaxy disks, or the high predicted number of small systems. We will consider the hypothesis that the baryonic dark matter could be in the form of gas and could be continuously involved in the galaxy formation scenario. By accreting cold gas throughout a galaxy's life, angular momentum could be increased, galaxy disks could be more dominated by baryons than previously thought, and small systems could merge more frequently.
Cosmic Matter Distribution: Cosmic Baryon Budget Revisited
Authors: Fukugita Masataka
Published: July 2016

The cosmic baryon budget is revisited using modern observations that have become available since our first publication. I also present an estimate for the heavy element abundance. An increased accuracy in the accounting of the baryon budget reveals ‘missing baryons’, which amount to ≈ 35% of the total. This would provide an interesting test for models of the cosmic structure formation.
The Dark Matter Content of Barred Spiral Galaxies
Authors: Petitpas Glen , Das Mousumi , Teuben Peter , Vogel Stuart
Published: July 2016

Two-dimensional velocity fields have been used to determine the dark matter properties of a sample of barred galaxies taken from the BIMA Survey of Nearby Galaxies (SONG). Preliminary results indicate that the maximal disk model is not appropriate in several galaxies in our sample, but higher resolution results will be needed to confirm this.
Mass Determination in the Late-Type Spiral NGC 5457
Authors: Puerari Ivânio , Valdez-Gutiérrez Margarita , Rosado Margarita
Published: July 2016

We have performed a kinematical and dynamical analysis of the ionized gas content of the late–type spiral NGC 5457 (M101) by means of scanning Fabry–Perot interferometry. the purpose of this study is to gain insight into the dark matter content in this galaxy. A sample of 263 HII regions were catalogued. We calculated radial velocity and velocity dispersions. From the dynamics of the ionized gas we were able to infer a mass of 9.8 × 1010 M⊙ inside a radius of 4'8 (or 10 kpc).
Dust and the observed dark matter content of galaxies
Authors: Baes Maarten , Dejonghe Herwig , Davies Jonathan I.
Published: July 2016

Using detailed Monte Carlo radiative transfer modeling, we examine the effects of absorption and scattering by interstellar dust on the observed kinematics of galaxies. Our modeling results have a direct impact on the derivation of the properties of dark matter haloes around both elliptical and spiral galaxies. We find that interstellar dust has a very significant effect on the observed stellar kinematics of elliptical galaxies, in the way that it mimics the presence of a dark matter halo. Taking dust into account in kinematical modeling procedures can reduce or even eliminate the need for dark matter at a few effective radii. Dust profoundly affects the optical rotation curve and stellar kinematics of edge-on disc galaxies. This effect, however, is significantly reduced when the galaxy is more than a few degrees from strictly edge-on. These results demonstrate that dust attenuation cannot be invoked as a possible mechanism to reconcile the discrepancies between the observed shallow slopes of LSB galaxy rotation curves and the dark matter cusps found in CDM cosmological simulations.
A Radial Velocity Dispersion Profile for the Fornax Dwarf Spheroidal Galaxy
Authors: Walker Matthew G. , Mateo Mario , Olszewski Edward W. , Woodroofe Michael , Wang Xiao , Joyce James
Published: July 2016

We have measured precise (± 3 km/s) radial velocities for 180 stars in the Fornax dwarf spheroidal galaxy, spanning the region R=0 to just beyond the nominal tidal radius. We perform a “classical” analysis of the resulting velocity dispersion profile. A mass-follows-light King model is ruled out, while a constant velocity dispersion model remains a good fit out to the limits of our dataset. For the constant velocity dispersion case, we calculate a velocity dispersion of 11.1 ± 0.7 km/s, which implies a central M/L/[M/L]⊙ ratio of 7.6 ± 1.0.
The Relationship between Stellar and Halo Masses of Disk Galaxies at z = 0.2 − 1.2
Authors: Conselice Christopher J. , Bundy Kevin , Ellis Richard S. , Brinchmann Jarle , Vogt Nicole
Published: July 2016

We present the results of a study to determine the co-evolution of the virial and stellar masses for a sample of 83 disk galaxies between redshifts z = 0.2 − 1.2. the virial masses of these disks are computed using measured maximum rotational velocities from Keck spectroscopy and scale lengths from Hubble Space Telescope imaging. We compute stellar masses based on stellar population synthesis model fits to spectral energy distributions including K(2.2μm) band magnitudes. We find no apparent evolution with redshift from z = 0.2 − 1.2 in the relationship between stellar masses and maximum rotational velocities through the stellar mass Tully-Fisher relationship. We also find no evolution when comparing disk stellar and virial masses. Massive disk galaxies therefore appear to be already in place, in terms of their virial and stellar masses, out to the highest redshifts where they can be morphologically identified.
Study on Neutron-induced Background in the CRESST Experiment
Authors: Wulandari H. , Von Feilitzsch F. , Huber M. , Jagemann Th. , Jochum J. , Lachenmaier T. , Lanfranchi J.-C. , Potzel W. , Rau W. , Stark M. , Waller S.
Published: July 2016

CRESST II is an experiment for direct WIMP search, using cryogenic detectors. the ratio of the two signals (temperature rise and scintillation light) measured for each interaction is an excellent parameter for discrimination of the radioactive background. the main remaining background is the neutron flux present at the experimental site, since neutrons produce the same signals as WIMPs do. Based on Monte Carlo simulations the present work shows how neutrons from different origins affect CRESST and which measures have to be taken into account to reach the sensitivity goal.
Probing the Interstellar Magnetic Field by Polarization Observations of Supernova Remnants
Authors: Fürst Ernst , Reich Wolfgang
Published: July 2016

We present a comparison of the Galactic magnetic field and the magnetic field of three supernova remnants (SNRs) of bilateral symmetry derived from linear polarization measurements. These data are best explained if a quasi-perpendicular propagation of the SNR-shock wave is assumed.
Radio Polarimetry of Tycho's SNR
Authors: Dickel John R. , Van Breugel Wil J. M. , Strom Richard G.
Published: July 2016

The remnant of Tycho's supernova of 1572 has been polarimetrically imaged using the 4 configurations of the VLA at wavelengths of 22 and 6 cm. A few data were also obtained at wavelengths of 21, 19, and 18 cm in the B configuration to check for any ambiguities in the Faraday rotation measurements and to look for deviations from the λ2 dependence of the Faraday rotation which would indicate significant internal Faraday effects. Although the total intensity shows structure on a scale of about 1 arcsecond the polarized emission appears to be resolved into cells of perhaps 10-arcsec size (1 arcsec corresponds to 0.011 pc at the 2.2 kpc distance to Tycho's SNR). We have therefore convolved the map shown in Figure 1 to a resolution of 4 arcsec to improve the signal-to-noise ratio. The contours represent the total intensity at 6-cm wavelength and the vectors show the position angle of the magnetic field with a length corresponding to the polarized intensity at 6 cm. In order to be seen, the vectors have a separation of 6 arcsec but no significant information is lost on this spacing.
Swing Excitation of Galactic Magnetic Fields Induced by Spiral Density Waves
Authors: Chiba Masashi , Tosa Makoto
Published: July 2016

The generation and maintenance of galactic magnetic fields are considered when the dynamo-acted disk is perturbed by spiral density waves. The periodic change of gaseous density and shear is coupled with the field oscillation as a dynamo wave. We find the conditions for parametric resonance which increases the efficiency of dynamos. Special attention is paid to two-armed spiral galaxies, in which the BSS field structure is possibly the most effectively excited configuration owing to the present mechanism.
The Formation of Discontinuities in Gas Flows in the ISM and its Relation to the Galactic Synchrotron Radio Emission
Authors: Berman V.G. , Marochnik L.S. , Mishurov Yu.N. , Suchkov A.A.
Published: July 2016

We show that large–scale motions of the interstellar gas, such as those associated with galactic density waves, easily develop, over a wide range of scales, shocks and discontinuities which are expected to generate turbulence. The latter is supposed to evoke diffusion of magnetic fields and cosmic rays on scales down to a few parsecs. We suggest that these processes may be of major importance in discussions of interconnections between the observed radio emission of the disks of spiral galaxies and the gas density distribution within them. In particular, we predict that the density of cosmic rays and magnetic field energy must be much less contrasted (on scales of ~1 pc and up to the scales of galactic shocks) than the gas density, hence the synchrotron radio emission is not as contrasted as is predicted under the hypothesis of a fully frozen-in magnetic field.
Optical and Radio Surface Photometry of NGC 891
Authors: Allen R.J. , Sukumar S. , Hu F.X. , Van Der Kruit P. C.
Published: July 2016

A general correlation between the radio and optical continuum surface brightness has been found in the edge-on galaxy NGC 891. This suggests that the relativistic electrons are produced/accelerated in the vicinity of evolved stars or stellar remnants which have a spatial distribution similar to old disk stars. In this picture, the magnetic field required for the synchrotron emission is carried up from the disk to high Z through instabilities and star-forming activity in the plane.
Vertical Magnetic Fields in Spiral Galaxies
Authors: Sofue Yoshiaki
Published: July 2016

Evolution of a vertical magnetic field which may have existed in the primeval galaxy is discussed based on a primordial-origin hypothesis for the bisymmetric spiral configuration of magnetic fields in spiral galaxies. The vertical field is accumulated toward the nucleus and forms a strong poloidal field, which may trigger activities like jets. Quasar jets are suggested to be the result of such strong vertical fields in the cores of primeval galaxies.
Equipartition: Fact or Fiction?
Authors: Duric Nebojsa
Published: July 2016

The use of equipartition calculations in estimating magnetic field strengths and energetics of extragalactic radio sources is widespread and well known. Since it is one of the few ways in which to calculate radio source parameters, it is important to determine how reasonable the approach generally is. Since this assumption is approximately a minimum energy criterion one expects that deviations from equipartition are limited at some level by independently determined constraints on the total energy. In this regard we have analyzed radio images of nearby spiral galaxies in order to determine equipartition magnetic fields and relativistic gas energies and to explore their possible nonequipartition configurations.
Magnetic Field Strengths of Spiral Galaxies and the Far-Infrared/Radio Correlation
Authors: Fitt A. J. , Alexander P.
Published: July 2016

We have calculated equipartition magnetic fields for a complete, optically-selected sample of 165 spiral galaxies. The magnetic field distribution (fig. 1) is type independent, and shows remarkably little spread in values, around 1 decade in B. This is not due to selection effects because of the nature of the sample and the 95 percent detection rate.
A CCD Polarimeter with Focal Reducer
Authors: Huber A.
Published: July 2016

At the Landessternwarte a new CCD polarimeter was constructed to observe magnetic fields (Davis-Greenstein) of nearby galaxies. This program is performed in collaboration with the MPI für Radioastronomie Bonn. By means of a focal reducer, the instrument records a field of 14.4 × 9.6 arcminutes at the 1.23-m telescope of the MPI für Astronomie on Calar Alto. Hence galaxies with large angular diameter, which have already been observed with the 100-m radio telescope Effelsberg, can be observed.
Magnetic Braking of Interstellar Clouds
Authors: Dorfi E.A.
Published: July 2016

We summarize the results of 3-D MHD calculations for a rotating and self-gravitating interstellar cloud. The angle between the axis of rotation and the magnetic field direction varies between π/2 and 0, the corresponding braking time-scales differ by roughly a factor of 3.
Observational Aspects of Magnetic Fields in Molecular Clouds
Authors: Troland T. H.
Published: July 2016

A small but growing body of observational information now exists regarding magnetic field strengths in molecular regions. Most of these data come from study of the Zeeman effect in 18 cm OH lines. The field is strong enough in many such regions to be dynamically important.
Polarization Measurements of Some Herbig Ae/Be Stars
Authors: Jain S. K. , Bhatt H.C. , Sagar Ram
Published: July 2016

We have measured the linear polarization of 8 bright Herbig Ae/Be stars in UBVRI bands. No unique wavelength dependence of polarization magnitude as well as direction is found in these measurements.
Chemical Diagnostics of Turbulent Magnetic Boundary Layers
Authors: Charnley S. B.
Published: July 2016

Results from models of the chemical evolution at the interfaces between hot, highly-ionized, stellar winds and cool, weakly-ionized, molecular clumps are presented.
A Wide Field λ90cm Image Around the Galactic Centre - Evidence for a Poloidal Magnetic Field
Authors: Anantharamaiah K. R. , Pedlar A.
Published: July 2016

A number of unique non-thermal filamentary structures, which are all roughly perpendicular to the galactic plane have been discovered in the vicinity of the Galactic centre (see Yusef-Zadeh 1989 and references there in). On the basis of their uniformity, polarization angles, rigidity, and pressure balance with the surrounding medium, it has been hypothesized that a strong polodial field of milligauss strength pervades the inner 50 pc of the Galaxy (Morris and Yusef-Zadeh 1989 and Morris in this volume). We present here a single wide-field image, at λ90cm, which shows all the filamentary structures in this region and show that these observations are consistent with the above hypothesis.
Interaction Between Magnetic Fields and Molecular Clouds on the Radio Arc
Authors: Tsuboi M. , Handa+ T. , Inoue M. , Inatani J. , Ukita N.
Published: July 2016

We have made observations of the Galactic center region in the CS J=1–0 and J=2–1 lines with the 45-m telescope at Nobeyama Radio Observatory in order to depict the fine structure and the activity of this region. We propose that several expanding molecular structures in this region are originated by successive supernova explosions at least of 102–3 times within 106 years. These may be responsible for strong magnetic fields in the Galactic center region. The interaction between one of the expanding molecular structures and the “vertical” filaments is found. From the appearance of the interaction, the magnetic field in the “vertical” filaments is estimated to be about 3–5 mGauss.
Synchrotron Radiation from Energetic Electrons Emitted by AGN: A Probe for Magnetic Fields in External Galaxies
Authors: Baring Matthew G.
Published: July 2016

Shock acceleration of protons in the central region of active galaxies can energize them to Lorentz factors as high as 108 (Sikora et al., 1987), and these can subsequently produce a host of other relativistic particles including pions, e+e– pairs and neutrons. The luminosities of each species are expected to be of the same order of magnitude. Rapid decay of the pions leads to the secondary production of photons and pairs with energies of around 109 − 1011 MeV. The electrons and positrons can escape the compact central region and interact with the microwave background forming a pair cascade, and can also emit synchrotron radiation in the magnetic field. The neutrons do not interact with the field, and a significant fraction of them can escape the central region of a galaxy (Kirk and Mastichiadis, 1989). They can travel until they decay, producing protons and electrons in outer regions of the galaxy. Their decay time of γnτn gives a typical length for decay of about 1 kpc for the most energetic neutrons. The synchrotron radiation of these decay product electrons is examined in Baring (1989, in preparation), and it produces definite signatures of galactic magnetic fields. Magnetic fields of 1μG imply synchrotron emission in the X-ray and soft gamma-ray range for maximum Lorentz factors of γe = 1010, with a continuum extending down to much lower energies. It is observed that cooler neutrons deposit electrons at smaller radii, and these electrons are cooler (in a decay γe ~ γn). Hence the radiation would be cooler at smaller radii. This provides a diagnostic for the magnetic field: estimates of the field strength are possible from cut-offs that are expected in spectra from galactic halos. The injection of energetic electrons via neutron decay is found to yield a sharp cut-off in the injection distribution at γm = γe ~ r/τnc at radius r. Below this, no electrons are injected since they are produced in decays at smaller radii. This implies a low energy cutoff of ωm = γ2mBmec2 in the spectrum at given radius. Typically for r = 10 pc and a field of 1μG, the cutoff is at 10−8mec2 in the far infra-red. At larger radii, this low energy cutoff rapidly increases to X-ray energies. This cut-off provides a good way to measure the magnetic field strength and obtain its spatial dependence. In practice the situation is complicated by the superposition of different regions within the galaxy along the line of sight. Ways in which the observations could be deconvolved are discussed in Baring (1989, in preparation). A real possibility exists for detecting these signatures of energetic neutron emission from central regions of nearby galaxies and using the electron synchrotron spectra to spatially map galactic fields.
High Energy Physics in Magnetic Jets and Hot Spots
Authors: Biermann Peter L.
Published: July 2016

In this progress-report I wish to describe the work my scientific collaborators and I have done over the last six years.
Collimated Bipolar Outflow and the Formation of Nuclear Spirals; Possible Role of Magnetic Fields
Authors: Pismis P. , Moreno E. , Garcia-Barreto A.
Published: July 2016

The existence of non–steady phenomena, namely activity in the form of radial motions (outflow) of matter from the nuclei of galaxies is well established at present. Active Galactic Nuclei (AGN) constitute a topic of great interest and are intensively studied by all existing observational techniques. Conventionally objects classified as AGN span a range from quasars, radio galaxies to Seyferts 1 and 2. It appears, however, that there exist galaxies which exhibit somewhat milder activity which does not qualify their inclusion in the AGN group. The designation of MAGN (M for mildly) was suggested in the past (Pismis, 1986) to cover the less energetic nuclei. It may be reasonable to consider that active nuclei form a sequence, the difference along it being due to the energetics of the nuclei, from the most active quasars and radio galaxies down to the mildest ones like M31 or our Galaxy. The phenomenon underlying the activity may thus be universal, subject to the intrinsic energetics of the nuclei (Pismis, 1987).
Comparison of Radio and Optical Polarization in Extended Extragalactic Radio Sources: I. Observations
Authors: Röser H.-J. , Meisenheimer K.
Published: July 2016

We presented new observations in various wavebands of those extragalactic radio sources for which the emission of optical synchrotron light is established by polarimetric investigations (jets of M 87 and 3C 273, hot spots in the lobes of 3C 20, 3C 33 and Pictor A). In addition to optical spectral index and polarization maps, we collected flux measurements at radio, millimetre, and near-infrared frequencies. Our observations result in accurate synchrotron spectra between 109 and 1015 Hz. For some sources a detailed comparison between radio and optical polarization is possible.
Magnetic Fields & Ionized Gas in Elliptical Galaxy Halos
Authors: Strom Richard G.
Published: July 2016

Faraday depolarization estimates of thermal densities within the components of double radio sources agree well with estimates from X-ray observations of hot halos around early-type galaxies, provided magnetic field strengths are close to their equipartition values. Internal Faraday dispersion is the main cause of the depolarization observed.
Magnetic Fields in Cooling Flow Clusters
Authors: Perley R. A.
Published: July 2016

Faraday rotation measurements of the luminous radio galaxies 3C295, Cygnus A, and Hydra A, all of which are associated with cD galaxies located in massive cooling flow clusters, show very high rotation measures – typically a few thousand radm−2, exceeding 20,000 radm−2 for 3C295. The RMs vary over large ranges and with different scales. The RMs are both positive and negative, implying reversals of the magnetic field – the variations cannot be due to density changes alone. The RMs originate in magnetized cluster gas, but it is unclear what fraction is due to a coccoon surrounding the radio source. If from the cluster as a whole, the magnetic field is , where N is the number of cells along the line of sight. A good case can be made for an enhanced magnetic field localized at or near the surface of the radio source, accounting for a significant fraction of the observed RM.
Intracluster Magnetic Fields from X-ray and Radio Measurements
Authors: Schlickeiser R. , Rephaeli Y.
Published: July 2016

The combination of the observed diffuse radio and hard X-ray emission from clusters of galaxies is used to estimate lower limits on the intracluster magnetic field strength or upper limits on the energy density of the cosmic infrared background radiation.
Studying the Evolving Universe with XMM-Newton and Chandra
Authors: Hasinger Günther
Published: July 2016

Two X-ray observatories, the NASA observatory Chandra and the ESA mission XMM-Newton, provide powerful new diagnostics of the “hot universe”. In this article I review recent X–ray observations of the evolving universe. First indications of the warm/hot intergalactic medium, tracing out the large scale structure of the universe, have been obtained lately in sensitive Chandra and XMM-Newton high resolution absorption line spectroscopy of bright blazars. High resolution X–ray spectroscopy and imaging also provides important new constraints on the physical condition of the cooling matter in the centers of clusters, requiring major modifications to the standard cooling flow models. One possibility is, that the supermassive black hole in the giant central galaxies significantly energizes the gas in the cluster.

XMM-Newton and Chandra low resolution spectroscopy detected significant Fe Kα absorption features in the spectrum of the ultraluminous, high redshift lensed broad absorption line QSO APM 08279+5255, yielding new insights in the outflow geometry and in particular indicate a supersolar Fe/O ratio. Chandra high resolution imaging spectroscopy of the nearby ultraluminous infrared galaxy and obscured QSO NGC 6240 for the first time gave evidence of two active supermassive black holes in the same galaxy, likely bound to coalesce in the course of the ongoing major merger in this galaxy.

Deep X–ray surveys have shown that the cosmic X-ray background (XRB) is largely due to the accretion onto supermassive black holes, integrated over the cosmic time. These surveys have resolved more than 80 % of the 0.1–10 keV X-ray background into discrete sources. Optical spectroscopic identifications show that the sources producing the bulk of the X-ray background are a mixture of obscured (type–1) and unobscured (type–2) AGNs, as predicted by the XRB population synthesis models. A class of highly luminous type–2 AGN, so called QSO-2s, has been detected in the deepest Chandra and XMM-Newton surveys. The new Chandra AGN redshift distribution peaks at much lower redshifts (z ≈ 0.7) than that based on ROSAT data, indicating that the evolution of Seyfert galaxies occurs at significantly later cosmic time than that of QSOs.
Chandra Observations of the Guitar Nebula
Authors: Wong Diane S. , Cordes James M. , Chatterjee Shami , Zweibel Ellen G. , Finley John P. , Romani Roger W. , Ulmer Melville P.
Published: July 2016

As part of a multi-wavelength study, we report on a 50 ks Chandra/ACIS observation of the Guitar Nebula, a bow shock nebula associated with the radio pulsar B2224+65. We see a “hot spot” at the tip of the bow shock. We also notice a “jet” of X-ray emission at position angle (PA) −69°. However, the proper motion of the pulsar and the axis of optical emission is at PA 52°.1. We discuss the resulting interpretations of the relativistic pulsar wind and the surrounding ISM.
“Hypernova” Radio Remnants
Authors: Asvarov Abdul I.
Published: July 2016

If recently discovered hypernova events are intrinsically energetic explosions of stars with a kinetic energy output of EK ≳ 1052 ergs than they can produce very large diameter (up to 500 pc) nonthermal radio shells. The properties of such shells are modelled and compared with the observational data on the large diameter supernova remnants (SNRs). One real candidate for the hypernova remnant is found. This is the supernova remnant N7793-S26 in the galaxy NGC 7793 (Pannuti et al. 2002).
Matter and Radiation in Superstrong Magnetic Fields and Thermal Emission from Neutron Stars
Authors: Lai Dong , Ho Wynn C.G.
Published: July 2016

Thermal surface emissions have now been detected from more than a dozen isolated neutron stars, including radio pulsars, radio-quiet neutron stars and magnetars. These detections can potentially provide important information on the interior physics, magnetic fields, and surface composition neutron stars. Understanding the properties of matter and radiative transfer in strong magnetic fields is essential for the proper interpretation of the observations. We review current theoretical works on modeling magnetized neutron star atmospheres/surface layers, discussing some of the novel properties of matter and radiative transfer in strong magnetic fields. Of particular interest is the effect of the strong-field vacuum polarization, which dramatically changes the radiative transfer and the emergent X-ray spectra from magnetars.