bluuebunny/crossref_metadata_2025 huggingface dataset:
The International Commission on Illumination - CIE: What It Is and How It Works
Authors: Hermann Christine
Published: July 2016

This paper explains the structure and organization of the International Commission on Illumination (CIE), shows how it works, and describes its objectives and achievements. It gives details on the technical work done in the CIE Divisions and Technical Committees, and mentions some examples of the work in progress, emphasising those in connection with the subject of this conference. Quality lighting is the key to reducing light pollution. CIE is aware of the problem and takes it very seriously. CIE Divisions are working on problems such as glare, quality lighting, light trespass, light pollution and energy efficiency. In this endeavour CIE is also co-sponsoring this conference.
Recent CIE Activities on Minimizing Interference to Optical Observations
Authors: Schreuder Duco A.
Published: July 2016

The paper describes the activities of CIE in the field of fighting sky glow. The most recent CIE publications are briefly discussed, as well as suggestions for further work. Modern developments in road lighting as well as alternatives to it are briefly discussed.
Guide on the Limitation of the Effects of Obtrusive Light from Outdoor Lighting Installations
Authors: Pollard Nigel
Published: July 2016

Division 5 of the CIE deals with the subject of “Exterior and other Lighting Applications” and has since 1991 had a Technical Committee (TC5.12) working on a “Guide on the limitation of the effects of obtrusive light from outdoor lighting installations”. This Committee did much of its work under the chairmanship of Dr. Alec Fisher of Australia, who has now retired and passed on the work to the current author. The present report outlines the content of the proposed Guide and details its relevance to help preserve the astronomical sky. It also highlights the close links with CIE Committee TC4.21, which works directly on the problems of sky glow.
Local and National Regulations on Light Pollution in Italy
Authors: Zitelli Valentina , Sora Mario Di , Ferrini Federico
Published: July 2016

The situation in terms of regulation of light pollution in Italy is here presented. The activity, started with the effort of amateur astronomers, lighting engineers and professional astronomers, is split into several actions oriented both to the local and national levels. One of the first goals was an ordinance of the city of Frosinone providing specific guidelines for lighting. The provinces of Valle d'Aosta and Veneto have followed up with local laws. The regional law of Valle d'Aosta includes a safeguard for nocturnal fauna from light pollution. The regional law of Veneto includes protection of the environment, observatories and astronomical sites. To avoid a proliferation of local laws, a national Italian bill was submitted and it is still under discussion. Bill No. 751 has been approved by the general assembly of the Italian Astronomical Society and provides more specific guidelines and standards concerning lighting in order to avoid unnecessary upward illumination and to reduce glare. At the same time a new technical standard, UNI 10819, has been settled after long debate among UNI (Italian National Standards Institute), the Italian Astronomical Society's Light Pollution Committee, lighting engineers and representatives of lighting manufacturers.
Observing Conditions from 1988 to 1999 at Huairou Solar Observing Station
Authors: Deng Yuanyong , Yan Yihua
Published: July 2016

This paper summarizes the change of astronomical observing conditions since 1986 at Huairou Solar Observing Station. Our results from 1988 to 1999 are as follows: quantitatively, stray light has increased and visibility has decreased; qualitatively, the seeing condition has become worse.
GPS Satellite Interference in Hungary
Authors: Borza T. , Fejes I.
Published: July 2016

Civil users of the NAVSTAR Global Positioning System (GPS) in Hungary occasionally experience interference at the 1575.42-MHz GPS signal frequency. As the application of the GPS technique spreads rapidly in our country, radio frequency interference (RFI) should be considered a serious threat. The new geodetic control network (OG-PSH) in Hungary is based on GPS measurements and incorporates more than 1100 sites. The paper reports the experiences gained during the establishment of the network. Interference sources were tracked to ground-based digital data transmissions for telecommunications, which operate mostly in the Western part of Hungary. Telecommunication regulations exceptionally allow such transmissions in specified countries. In order to warn potential GPS users, the interference sources are being mapped.
Astrochemistry: Historical Perspective and Future Challenges
Authors: Dalgarno A.
Published: July 2016

A review is presented of some of the developments in astrochemistry that have occurred in the past three years, ranging from the chemistry of the early Universe to the chemistry of planetary systems.
Chemistry in the Envelopes around Massive Young Stars
Authors: van Dishoeck Ewine F. , van der Tak Floris F. S.
Published: July 2016

Recent observational studies of intermediate- and high-mass star-forming regions at submillimeter and infrared wavelengths are reviewed, and chemical diagnostics of the different physical components associated with young stellar objects are summarized. Procedures for determining the temperature, density and abundance profiles in the envelopes are outlined. A detailed study of a set of infrared-bright massive young stars reveals systematic increases in the gas/solid ratios, the abundances of evaporated molecules, and the fraction of heated ices with increasing temperature. Since these diverse phenomena involve a range of temperatures from < 100 K to 1000 K, the enhanced temperatures must be communicated to both the inner and outer parts of the envelopes. This ‘global heating’ plausibly results from the gradual dispersion of the envelopes with time. Similarities and differences with low-mass YSOs are discussed. The availability of accurate physical models will allow chemical models of ice evaporation followed by ‘hot core’ chemistry to be tested in detail.
Interferometric Observations of Chemistry in High-Mass Star-Forming Regions
Authors: Schilke Peter , Menten Karl M. , Wyrowski Friedrich , Walmsley C. M.
Published: July 2016

Single dish spectral line surveys of high mass star-forming regions provide spectra with a very high line density, and reveal the presence of many complex molecules. Besides the prototypical Orion BN/KL region, more and more regions get surveyed and we start to get a better idea of the chemical similarities and differences. Yet, single dish studies miss an important aspect of hot cores, which is revealed by higher resolution studies with interferometers: the cores are not chemically homogeneous, but a pronounced chemical substructure exists. As an example of such an interferometric study, we will present one particular set of objects, the UC HII W3(OH) and its neighboring hot core W3(H2O) (otherwise known as the Turner-Welch object), and discuss their chemical properties.
First Results from the Submillimeter Wave Astronomy Satellite – H2O and O2 Discoveries
Authors: Melnick Gary J.
Published: July 2016

The Submillimeter Wave Astronomy Satellite (SWAS) was successfully launched on 5 December 1998 with the goals of studying: (1) the distribution of oxygen in the interstellar medium; (2) the role of H2O and O2 as gas coolants; and (3) the UV-illuminated surfaces of molecular clouds. To achieve these goals, SWAS is conducting pointed observations of dense (n(H2) > 103 cm–3) molecular clouds throughout our Galaxy in either the ground-state or a low-lying transition of five astrophysically important species: H2O, H218O, O2, CI, and 13CO. SWAS has made great strides in each of these areas of investigation. This paper will summarize our H2O and O2 findings one year into the mission.
Masers as Kinematic Signposts in Star Formation Regions
Authors: Norris Ray P.
Published: July 2016

Masers have been well studied as indicators of star formation regions for over three decades. Their small size, high brightness, and narrow velocity width mean that we can measure their position and velocity with enormous accuracy, and so they stand out as high-precision signposts amidst the swirling gas that they sample. Nevertheless, in most cases the complexity of their kinematics has defied attempts to use them to unravel the processes of star formation. However, the last two or three years have seen a resurgence of interest in these masers because of exciting new evidence that, in some cases, they are tracing with high precision the kinematics of material in circumstellar disks around massive stars. The very existence of circumstellar disks around these massive stars is puzzling, and yet the maser results have now been confirmed by other data at radio and infrared wavelengths. In this paper I will review the current status of high-resolution maser observations, discuss some of the puzzles that are now confronting us, and speculate on where our current tentative steps may lead us.
Dissociative Recombination of Polyatomic Molecular Ions: Branching Ratios and Isotopic Effects
Authors: Andersen L. H. , Heber O. , Zajfman D.
Published: July 2016

The branching ratios for the dissociative recombination of various vibrationally cold polyatomic molecular ions have been measured using the ASTRID ion storage ring. The results show that many particles are ejected during the recombination process, and that isotopic effects exist when hydrogen atoms are replaced by deuterium.
Organics in Space: From Interstellar Dust to Comets
Authors: Greenberg J. Mayo , Caro Guillermo M. Muñoz
Published: July 2016

A cyclic evolutionary picture is presented which follows the sources and nature of organics from interstellar space to comets. The three major organic components discussed are the grain mantles, the carbonaceous particles responsible for the 216 nm hump in the extinction, and the large molecules/small particles polycyclic aromatic hydrocarbons (PAHs). The variability in the oxygen and hydrogen abundances relative to carbon is followed.
Diffuse Interstellar Bands
Authors: Sarre P. J. , Kendall T. R.
Published: July 2016

The unidentified diffuse interstellar bands are observed in near-UV, visible and near-IR spectra recorded towards stars which are partially obscured by interstellar dust. Their origin is the longest standing problem in astronomical spectroscopy and dates back to the 1930s when systematic study of the bands first started. Proposals for the carriers range from molecular hydrogen to porphyrins and from colour centres to species adsorbed on grain surfaces. This paper contains a short review of the problem and a discussion of recent possible assignments of some of the bands to transitions of the H2, and molecules. Observations of ultra-high resolution spectra of diffuse absorption bands, optical diffuse emission bands from the Red Rectangle, and complementary studies of the 3.3 μm ‘unidentified’ infrared (UIR) emission band are described.
ISO's View of the Molecular Content of Evolved Stars
Authors: Cernicharo J.
Published: July 2016

The recent results of the ISO satellite in the field of molecular spectrocopy of AGB stars are reviewed. For the fist time, the two spectrometers onboard ISO have provided the opportunity to observe the pure rotational lines of several molecules in the far infrared and the ro-vibrational bands of the most abundant molecular species in the near and mid-infrared. These data allow to carry out a systematic study of the circumstellar envelopes of AGB stars and Planetary Nebulae. I analyze in this paper the role of resonant scatterring in the pumping of the ro-vibrational molecular levels in CSEs.
Sinks of Light Elements in Stars - Part III
Authors: Charbonnel Corinne , Deliyannis Constantine P. , Pinsonneault Marc H.
Published: July 2016

See the abstract given in Part I (Deliyannis, Pinsonneault, Charbonnel, hereafter DPC, this volume). In Part III, we first discuss the LiBeB observations in subgiant stars and the constraints they bring on the transport processes occuring on the main sequence. Evidence is then reviewed that suggests that in situ mixing occurs in evolved low mass Population I and Population II stars. Theoretical mechanisms that can create such mixing are discussed, as well as their implications for the evolution of the LiBeB and 3He.
Blue Compact Galaxies and the Primordial 4Helium Abundance
Authors: Xuan Thuan Trinh , Izotov Yuri I.
Published: July 2016

Blue compact galaxies (BCG) are ideal objects in which to derive the primordial 4He abundance because they are chemically young and have not had a significant stellar He contribution. We discuss a self-consistent method which makes use of all the brightest He I emission lines in the optical range and solves consistently for the electron density of the He II zone. We pay particular attention to electron collision and radiative transfer as well as underlying stellar absorption effects which may make the He I emission lines deviate from their recombination values. Using a large homogeneous sample of 45 low-metallicity H II regions in BCGs, and extrapolating the Y-O/H and Y-N/H linear regressions to O/H = N/H = 0, we obtain Yp = 0.2443±0.0015, in excellent agreement with the weighted mean value Yp = 0.2452±0.0015 obtained from the detailed analysis of the two most metal-deficient BCGs known, I Zw 18 and SBS 0335-052. The derived slope dY/dZ = 2.4±1.0 is in agreement with the value derived for the Milky Way and with simple chemical evolution models with homogeneous outflows. Adopting Yp = 0.2452±0.0015 leads to a baryon-to-photon ratio of (4.7+1.0-0.8) × 10−10 and to a baryon mass fraction in the Universe ωbh250 = 0-068+0.015-0.012, consistent with the value derived from the primordial D abundance of Burles &Tytler (1998).
Spatial Variations in the Atomic D/H Ratio in the ISM
Authors: Sonneborn G. , Jenkins E. B. , Tripp T. , Wozniak P. , Ferlet R. , Vidal-Madjar A. , Sofia U.J.
Published: July 2016

Observations with IMAPS demonstrate that interstellar atomic D/H abundance ratios differ by a factor of 3 on the sightlines toward Δ Ori A, ζ Pup, and γ2 Vel, early-type stars within ˜ 500 pc of the Sun. The observed D/H differences are not inversely correlated with N/H, as would be expected if injection of CNO-processed material was the primary mechanism for the D/H abundance variations in the ISM.
A Very Reduced Upper Limit on the Interstellar Abundance of Beryllium
Authors: Hébrard Guillaume , Lemoine Martin , Ferlet Roger , Vidal-Madjar Alfred
Published: July 2016

We present the results of observations of the λ3130Â interstellar absorption doublet of 9Be ii in the direction of ζ Per. The data were obtained at the Canada-France-Hawaii 3.6m telescope using the Gecko spectrograph at a resolving power ∼ 110000 and a signal-to-noise ratio ∼ 2000. The 9Be ii lines are not detected and we obtain an upper limit on the equivalent width W ≤ 30μÂ. This upper limit is 7 times below the lowest upper limit ever reported hitherto. The derived interstellar abundance is (9Be/H) ≤ 7 × 10—13; it corresponds to an upper limit δBe ≤ —1.5 dex on the depletion factor of 9Be.
Lithium in Post T Tauri Stars
Authors: Quast G. R. , Torres C. A. O. , de la Reza R. , da Silva L.
Published: July 2016

We analyze the Li depletion in the PTT-gap proposed by Martin (1997) using the young stars, with ages between 10 and 100 Myr, recently discovered by us during a survey around isolated T Tau stars.
Concluding Remarks II
Authors: Reeves Hubert
Published: July 2016

The symposium has shown that our subject is well and very alive. It is progressing rapidly, thanks to a large amount of new observational data, obtained in particular by a young generation of competent astronomers. It is encouraging, incidentally, to note the large fraction of women in this generation. When I started in this field, some forty years ago, the feminine contribution was much smaller. I plan to review the state of the situation for each of the three nucleosynthesis processes responsible for the light elements: Big Bang Nucleosynthesis (BBN), galactic cosmic ray spallation of interstellar nuclei (GCR) and stellar nucleosynthesis. I will point out their successes, their riddles and possible avenues by which these riddles could be solved. I plan first to review the observations.
A Low frequency Southern Sky Survey Using the Mauritius Radio Telescope
Authors: Udaya Shankar N.
Published: July 2016

The Mauritius Radio Telescope (MRT) is a Fourier synthesis instrument which has been built to fill the gap in the availability of deep sky surveys at low radio frequencies in the southern hemisphere. It is situated in the north-east of Mauritius at a southern latitude of 20°.14 and an eastern longitude of 57°.73. The aim of the survey with the MRT is to contribute to the database of southern sky sources in the declination range −70° ≤ δ ≤ −10°, covering the entire 24 hours of right ascension, with a resolution of 4' × 4'.6sec(δ + 20.14°) and a point source sensitivity of 200 mJy (3σ level) at 151.5 MHz.

MRT is a T-shaped non-coplanar array consisting of a 2048 m long East-West arm and a 880 m long South arm. In the East-West arm 1024 fixed helices are arranged in 32 groups and in the South arm 16 trolleys, with four helices on each, which move on a rail are used. A 512 channel, 2-bit 3-level complex correlation receiver is used to measure the visibility function. At least 60 days of observing are required for obtaining the visibilities up to the 880 m spacing. The calibrated visibilities are transformed taking care of the non-coplanarity of the array to produce an image of the area of the sky under observation.

This paper will describe the telescope, the observations carried out so far, a few interesting aspects of imaging with this non-coplanar array and present results of a low resolution survey (13' × 18') covering roughly 12 hours of right ascension, and also present an image with a resolution of 4' × 4'.6sec(δ + 20.14°) made using the telescope.
Radio Source Evolution Derived from Low Frequency Surveys
Authors: Jackson C.A. , Wall J.V.
Published: July 2016

We find simple parametric models to describe the space density evolution of radio-loud AGN, treating FRI and FRII radio galaxies separately as the two parent populations in our dual-population unified scheme. In this we use low frequency radio data (v < 500 MHz), where radio samples are unbiased by Doppler beaming. Incorporated into this latest analysis is a new determination of the local radio luminosity function at 1.4 GHz from galaxies common to both the 2dFGRS and NVSS surveys.
Cosmic Microwave Background at Low Frequencies
Authors: Subrahmanyan R.
Published: July 2016

The next generation low-frequency radio telescopes may probe cosmological models by means of observations of the cosmic microwave background (CMB). I discuss the prospects for observations of CMB imprints —- recombination lines from the epoch of recombination, μ distortions and angular temperature anisotropies —- at low frequencies. A future low-frequency radio telescope, like the proposed SKA, may be capable of attempting some difficult CMB measurements because of the large collecting area and large element numbers; however, this will require a telescope design that will allow specialized calibration strategies and will give emphasis to the control of spurious responses.
Search for Radio Recombination Lines towards the Gravitational Lens PKS1830-211
Authors: Mohan N.R. , Anantharamaiah K.R. , Goss W.M.
Published: July 2016

A search for radio recombination lines near 20 cm at z=0.193 and z=0.886 towards the gravitational lens system PKS1830-211 has yielded upper limits of |τL| ≤ 5 × 10−5 and ≤ 5 × 10−4 at the two redshifts respectively. Based on the non-detections, we derive upper limits to the emission measure of the ionized gas in the absorbing systems. We also present continuum flux density measurements over the frequency range 0.3—45 GHz made at a single epoch.
HI in Active Galactic Nuclei
Authors: Yu Z. , Jiang D.
Published: July 2016

Recent VLBA and VLA observations indicate the possibility of a circumnuclear disc or torus of HI in detected in absorption in NGC 3894. Strong absorption lines are detected toward both the aproaching and receding jets. Absorption profiles integrated over six regions across the source are shown. At lease two velocity components are present in all lines of sight except toward the southeast. The parameters are obtained from these fits(Peck and Taylor,1998,Ap.J.,502,L23). We use the bending model to explain the four prominent absorption features.
Theoretical Implications of Diffuse Non-Thermal Emission from Clusters of Galaxies
Authors: Enßlin T.A.
Published: July 2016

A short review on theoretical implications of non-thermal emission (radio, extreme ultraviolet, high energy X-ray) from the intra-cluster medium is given. The origin of cluster radio halos and cluster radio relics is discussed within the framework of a network of processes producing a non-thermal electron population. Emphasis is given to the role of old, remnant, presently invisible relativistic plasma released by former radio galaxies.
Radio Halos and Relics in Clusters of Galaxies and Detection Statistics
Authors: Giovannini Gabriele , Feretti Luigina , Govoni Federica
Published: July 2016

New sensitive VLA observations confirm the existence of halo and relic sources in 6 Abell clusters where a diffuse emission was found in the NVSS.

We find evidence that the frequency of clusters with halos and relics is larger in clusters with high X-ray luminosity. The evidence that the occurrence of a halo source is larger at high redshifts is marginal.
The Dual Radio Relics of A3667
Authors: Johnston-Hollitt M. , Clay R. W. , Ekers R. D. , Wieringa M. H. , Hunstead R. W.
Published: July 2016

A3667 is a remarkable cluster of galaxies possessing the two largest and brightest radio relics yet seen. It provides an important opportunity to examine the environments associated with relic production.
Spectral Mapping of Classical Double Radio Sources
Authors: Leahy J.P. , Muxlow T.W.B.
Published: July 2016

We review the evidence that spectral curvature in the extended emission of radio galaxies is caused by synchrotron losses, and that the spatial variation can be interpreted to yield ages and expansion speeds. One of the biggest worries has been the true value of the magnetic field, but X-ray detections of inverse-Compton radiation are beginning to suggest that “minimum energy” estimates are remarkably accurate. A critical test is to compare model and observed spectra over a broad frequency range; to date this has has only been done for Cygnus A, and the results proved controversial. Here we discuss several more cases and begin to draw some general conclusions.

Hotspots are usually well fitted by continuous injection models, as expected. In two cases the implied injection index is flatter than 0.5, too flat to be produced by standard Fermi acceleration in a non-relativistic shock. The bridge spectra are reasonably fitted by single-burst models, but in some objects the injection index is not constant across the lobes, showing instead a tendency to steepen in the inner bridge, where the break frequencies are lowest. The true spectral shape may be a more gradual curve than the standard models, possibly because of mixing of electron populations with different ages. Our results are limited by the inaccuracy of the absolute flux density scale, especially at low frequencies, and a fresh attack on the flux scale would be timely.
Giant Radio Sources: Evolution and GMRT Observations
Authors: Ishwara-Chandra C.H. , Saikia D.J.
Published: July 2016

We study the evolution of giant radio sources and show that they are less luminous than the smaller-sized sources, and are roughly consistent with the evolutionary scenarios where the smaller-sized sources evolve to giants undergoing radiative and expansion losses. Inverse-Compton radiation losses due to the microwave background radiation dominates over the synchrotron losses for giant sources, while for the smaller sources, the latter dominates. We show that giant radio galaxies and quasars are consistent with the unified scheme, and their large sizes are not due to stronger cores. We also present preliminary GMRT images of three giant sources.
The Problem of Identifying Decametric Sources
Authors: Verkhodanov O.V. , Andernach H. , Verkhodanova N.V.
Published: July 2016

We describe a method to cross-identify and construct continuum spectra for radio sources from decametric surveys with comparatively large positional errors. The 1822 sources from the UTR-2 catalogue (10—25 MHz, antenna beam of ∼40') were cross-identified with entries from other radio catalogues at higher frequencies. Using the CATS database we found accurate positions for 2314 counterparts to UTR sources, as well as a best-fit radio spectrum for most of these. About 350 (or 19%) of the UTR sources appear to be blends of two or more sources.
Study of Objects of Low Radio Frequency Catalogues and IRAS Data — Cross-Identification
Authors: Verkhodanov O.V. , Trushkin S.A.
Published: July 2016

We present results of cross—identifications of the objects from two large catalogues, IRAS and the low radio frequency Texas catalogue at 365 MHz in the database CATS. The resulting list consists of 715 pairs of sources within a circle of radius of 60 arcsec. It has been cross—identified with the GB6 4.85 GHz, NVSS 1.4 GHz, FIRST 1.4 GHz, WENSS 325 MHz radio catalogues, ROSAT catalogues and different optical data lists, including APM catalogue. We selected 3 subsamples: objects matching in 3″radius, ultra steep spectrum (USS) radio sources, inverse spectrum radio sources, galactic sources. Several objects have radio spectral index α < −2, some of them in Galactic plane.
Extended X-ray Emission from FRIIs and RL Quasars
Authors: Setti G. , Brunetti G. , Comastri A.
Published: July 2016

We review the evidence that detectable fluxes of X-rays are produced by inverse Compton scattering of nuclear photons with the relativistic electrons in the radio lobes of strong FRII radio galaxies within the FRII-RL quasar unification scheme. We report here on the possible detection of this effect in two steep spectrum RL quasars. This may have important implications on the physics and evolution of powerful radio galaxies.
The SEDs Database to Study Evolution of Radio Galaxies
Authors: Verkhodanov O.V. , Kopylov A.I. , Zhelenkova O.P. , Verkhodanova N.V. , Chernenkov V.N. , Parijskij Yu.N. , Soboleva N.S. , Temirova A.V.
Published: July 2016

The project of the informational system creation on the problem of evolution of radio galaxies is described. This system, being developed at present, will allow a user to operate with simulated curves of spectral energy distributions (SED) and to estimate ages and redshifts by photometrical data. Planned modes of access, formats of output result and additional functions are described.
The Molonglo Galactic Plane Survey: MGPS2
Authors: Green A. J.
Published: July 2016

A survey of the southern Galactic Plane is being made in the radio continuum at 843 MHz with the Molonglo Observatory Synthesis Telescope. The area to be covered is 240° ≤ l ≤ 365°, |b| ≤ 10° with a resolution of 43″ × 43″cosec|δ| and a 3σ rms noise of ≤ 5 mJy/beam. This survey (MGPS2) will be used to search for possible new supernova remnant candidates, to image other discrete sources such as HII regions and radio galaxies located behind the Galaxy, and to study the structure of the interstellar medium. Comparison with a first epoch survey (MGPS1) will also be made. Some of the first results from MGPS2 are presented.
The Galactic Center at 327 MHz
Authors: LaRosa T.N. , E. Kassim Namir , W. Lazio T. Joseph , Hyman S.D.
Published: July 2016

Figure 1 presents a wide-field, high dynamic-range, 327 MHz VLA2 image of the Galactic center (GC). This image was constructed from archival VLA data using new 3-D image restoration techniques which resolve the problem of non-coplanar baselines encountered at long wavelengths. In a recent paper (LaRosa et al. 2000) we presented a catalog of over a hundred sources from this image, 23 extended sources and 78 small-diameter sources. The catalog contains flux densities, positions, sizes, and, where possible, a 20/90 cm spectral index. We also present subimages of all the extended sources. We refer the reader to LaRosa et al. (2000) for the details. In this note we will concentrate on observations of the nonthermal filaments and briefly describe a new model for their formation.

The origin and evolution of the nonthermal filaments (NTFs) observed in the GC is an outstanding problem. All of the 7 classified NTFs are visible on Figure 1: Four of these are labeled threads, the other three are the “Snake,” the “Pelican,” and the Sgr C filament. The wide-field imaging at 327 MHz lead to the discovery of the “Pelican” (Lang et al. 1999). This filament has the distinction of being the farthest NTF in projection from Sgr A and the only NTF that is parallel to the Galactic plane. One critical issue for understanding the activity and overall structure of the GC is whether these filamentary sources trace a pervasive, large-scale magnetic field or are local independent structures (e.g., Yusef-Zadeh 1989; Morris 1994, 1996; Uchida & Gusten 1995; Yusef-Zadeh, Wardle & Parastaran 1997; Shore & LaRosa 1999; Lang et al. 1999; Lang, Morris & Echevarria 1999; LaRosa et al. 2000).
Pulsars and the ISM
Authors: Gupta Yashwant
Published: July 2016

Radio signals from pulsars are significantly affected by propagation effects such as dispersion, faraday rotation and scintillations in the interstellar medium (ISM). In this paper, I review some aspects of our understanding about pulsars and interstellar scintillations (ISS). The study of pulsar scintillation has dual benefits in that it allows us to learn about the properties of the ISM using pulsars as probes, as well as to infer some properties about pulsars, using the ISM as a tool. Both these aspects are addressed in this paper. The main emphasis is on recent developments in the following topics : (i) the shape of the spectrum of electron density fluctuations in the interstellar medium (ii) the distribution of scattering plasma in the local ISM and (iii) resolving pulsar emission regions using ISS.
Detection of New Emission Components in PSR B0329+54
Authors: Gangadhara R.T. , Gupta Y. , Lorimer D.R.
Published: July 2016

To study the structure of emission beam, we have analysed the single pulse data of PSR B0329+54 at 325 and 606 MHz. In order to unambiguously detect the weak emission components, we have developed a new data analysis technique, which we term “window—thresholding”. By applying this technique to the data, we have detected three new emission components, and also confirmed the presence of a component which was proposed earlier. Hence our analysis indicates that PSR B0329+54 has nine components, which is among the highest of all the known pulsars. The symmetric distribution of pulse components about the pulse centre, indicates that the emission beam is conal.
Giant Pulses from Two Pulsars
Authors: K. Singal Ashok , Manoharan P.K. , G. Strom Richard
Published: July 2016

We present observational results from long term monitoring of giant pulses from two pulsars. One of the pulsars (PSR 0950+08) has been observed simultaneously at three different observatories, at different radio frequencies. There is evidence to suggest that the giant pulse phenomenon is intrinsic to the pulsar.
Solar Radio Astronomy at Low Frequencies
Authors: Pick Monique
Published: July 2016

This review is concerned to study of sun at frequencies lower than 1.4 GHz. Emphasis is made on results which illustrate the topics in which GMRT could play a major role. Coordinated studies including spectral and imaging radio observations are important for research in solar physics. Joint observations between the Giant Meter Radio Telescope (GMRT) with radio instruments located in the same longitude range are encouraged. This review inludes three distinct topics: Electron beams and radio observations- Radio signatures of Coronal Mass Ejections- Radio signatures of coronal and interplanetary shocks.
Practical Lessons from Low Frequency Imaging with the VLA
Authors: K. Lacey Christina , E. Kassim Namir
Published: July 2016

Many lessons gained in imaging 74 and 330 MHz VLA data are of practical interest to future users of the GMRT and other low frequency observers. Three important issues are 1) radio frequency interference excision, 2) self-calibration, and 3) wide-field imaging. Recently developed tasks to address these and other problems encountered in low frequency VLA data reduction now exist or are being developed in both AIPS and AIPS++. We will describe how we use some of these new tools to routinely generate wide-field, low frequency images with sensitivities approaching thermal or classical confusion limits.
Low Frequency Radio Astronomy from Above the Ionosphere
Authors: Jones D. L.
Published: July 2016

The GMRT represents a dramatic improvement in ground-based observing capabilities for low frequency radio astronomy. At sufficiently low frequencies, however, no ground-based facility will be able to produce high resolution images while looking through the ionosphere. A space-based array will be needed to explore the objects and processes which dominate the sky at the lowest radio frequencies. An imaging radio interferometer based on a large number of small, inexpensive satellites would be able to track solar radio bursts associated with coronal mass ejections out to the distance of Earth, determine the frequency and duration of early epochs of nonthermal activity in galaxies, and provide unique information about the interstellar medium.
Turbulent Transport of Magnetic Fields and the Solar Dynamo
Authors: Kichatinov L.L.
Published: July 2016

The effect of anisotropic transport of the mean magnetic field by turbulence in a stratified rotating fluid is briefly discussed to find its qualitative correspondence to the observed field redistribution over a solar cycle. A kinematic model of a dynamo in a spherical shell is developed with the transport effect included to assess its importance in a more consistent way. The anisotropic transport brings the simulated field behavior closer to that observed on the Sun.
On the Stability of Magnetic Flux Tubes in the Equator of a Star
Authors: Ferriz-Mas A. , Schüssler M.
Published: July 2016

We consider the linear stability of a toroidal flux tube lying in the equatorial plane of a differentially rotating star and investigate its dependence on superadiabaticity, magnetic field strength, and gradient of angular velocity.
On the Fluctuations of the Total Solar Irradiance
Authors: Schröder W. , Treder H.J.
Published: July 2016

The fundamental quantity for the total solar irradiance is the solar constant J which is determined by the mean Sun-Earth distance and by the energy budget in the interior of the sun. The mean distance is the major semi-axis of the earth orbit and therefore a constant of celestial mechanics. The energy production and transport in the interior of the sun must be constant at least during a Helmholtz-Kelvin period. Actually, the heat budget of the sun is constant during some billion years.
The HeI λ10830 Å Observations of Two Rs Cvn Systems ζ and λ And
Authors: Shcherbakov A.G. , Fernandez-Figueroa M.J. , Martin-Parra F. , De Castro E. , Cornide M.
Published: July 2016

Magnetically active late-type stars have inhomogeneities on their surfaces that cause various observable effects in the spectral lines and light curves. Such inhomogeneities are magnetic starspots, plages etc. in active regions on the photospheric and chromospheric level. The variations of the spectral lines and light curves originating in these inhomogeneities undergo modulations following stellar rotation.
Dynamo and Fossil Magnetic Field in Young Stars
Authors: Dudorov A.E.
Published: July 2016

The theory of fossil magnetic fields shows that new born stars may have internal magnetic fields of more than 1 million gauss. Convection inside young solar type stars will tangle any strong fossil magnetic field. The small scale magnetic field rises to the surface and determines the young stars activity attenuating with their age. When a fossil field is diminished a turbulent dynamo may begin to work in the condition of nonlinear stabilization. The scaling relations for the turbulent αω dynamo show that the strength of the generated “fossil” magnetic field inside the main sequence stars is stabilized on the level one tenth — 10 millions gauss, depending on the mass of the stars.
Dynamo Driven by Weak Plasma Turbulence
Authors: Tong Y. , Chian A.C.-L.
Published: July 2016

We discuss a dynamo mechanism driven by weak plasma turbulence and show that turbulent plasma waves may generate and maintain cosmic magnetic field. A dynamo equation is derived from the magnetic induction equation based on mean field electrodynamics. In the usual α–ω dynamo theory, the source term in the dynamo equation arises from α–effect associated with the convective motion of the fluid. In contrast, in our theory the source term is determined by “P–effcct” associated with weakly turbulent waves (e.g. Alfvén waves) in the plasma. We suggest that “P–ω” dynamo may be operative either in the presence or absence of convection. The sole requirement for its operation is the existence of weak plasma turbulence in the source region of the cosmic magnetic field.
Calculation of the Electrical Conductivity of Plasmas by Fluctuations of the Electromagnetic Field
Authors: Meister C.-V.
Published: July 2016

A method to calculate the electrical conductivity of plasmas with electromagnetic waves with small wave number is discussed.
The Local Magnetic Field in Our Galaxy
Authors: Han J.-L. , Qiao G.-J.
Published: July 2016

The pitch angles of the local magnetic field in our Galaxy, previously derived from Rotation Measures (RMs) of pulsars by many authors, are not consistent with each other and with the pitch angles of the local spiral arms. That may be due to the fact that the used pulsar samples are located in different arms in which the directions of the magnetic fields are different. In this paper 2-D and 3-D models for the local magnetic field based on spiral arms are proposed for fitting the RMs of 129 nearby pulsars. In our models the amplitude of the uniform field changes sinusoidally to avoid abrupt reversals, and the directions are parallel or anti-parallel. The best-fitting 2-D model shows that in the Orion arm the strength of the regular field component is 2.4 ± 0.3μG,with its direction towardsl= 73° ± 3°. There is a direction reversal in Sagittarius-Carina arm beginning atDrev= 0.3Kpc.The half “wavelength” of the sinusoidal variation is about 1.7 ± 0.4Kpc.The best fitting 3-D model shows that the scale height is only about 0.16 Kpc, which means that the local uniform field is confined in the galactic plane. The strongest regular field in this 3-D model is about 2.8±0.3μG.The results from both, the 2-D model as well as the 3-D model, show that the orientation of the field is in excellent agreement with the spiral arms.
The Intrinsic Magnetic Field Orientation in NGC 4631: Dynamo or Outflow ?
Authors: Golla Götz , Hummel Edsko
Published: July 2016

The interacting galaxy NGC4631 is unique among edge-on galaxies in that it shows a prominent synchrotron radio halo. We derive the intrinsic magnetic field structure in this halo. The field lines are mainly radially outgoing from the central region. The possible mechanisms generating such magnetic fields in the halo, i.e. outflows and dynamo processes, are discussed.
Magnetic Fields in the Spiral Galaxy NGC 6946
Authors: Ehle Matthias , Beck Rainer
Published: July 2016

High frequency polarization observations reveal the existence of a large-scale ordered magnetic field in the disk of the spiral galaxy NGC 6946. At lower frequencies the disk is no longer transparent to polarized radio waves due to Faraday depolarization. The spiral pattern of the uniform magnetic field and the distribution of polarized intensities are fairly well simulated by a dynamo model. The model parameters indicate that the dynamo does not only operate in the disk, but also in the halo.
3D-Numerical Simulations of Magnetic Field Evolution in the Turbulent Interstellar Gas
Authors: Otmianowska-Mazur K. , Urbanik M.
Published: July 2016

A fully three-dimensional kinematic model is applied to simulate the evolution of the magnetic field in a small (120 pc in size) volume of the turbulent interstellar medium (ISM) in the presence of the field diffusion. The turbulent motions arc approximated by a sequence of non-overlapping in time vortices, which have the form of the rotating (with a non-zero hclicity) columns much longer than the parcel size. They moved vertically and at the inclination of ±30° to the galactic plane. The resulting magnetic field structure closely resembles a fragment of a classical twisted flux tube, well-ordered over the whole parcel of the ISM.
Particle Acceleration in Extragalactic Jets and Implications for the High-Energy Emission from Blazars
Authors: Schlickeiser R. , Dermer C. D.
Published: July 2016

We demonstrate that the prevalence of superluminal sources in the sample of γ-ray blazars and the peak of their luminosity spectra at γ-ray energies can be readily explained if the γ-rays result from the inverse Compton scattering of the accretion disk radiation by relativistic electrons in outflowing plasam jets. Compton scattering of external radiation by nonthermal particles in blazar jets is dominated by accretion disk photons rather than scattered radiation to distances of ∼ 0.01–0.1 pc from the central engine for standard parameters. The size of the γ-ray photosphere and the spectral evolution of the relativistic electron spectra constrain the location of the acceleration and emission sites in these objects.
EGRET High-Energy Gamma-ray Observations of AGN: Energy Spectra and Time Variability
Authors: Thompson D.J. , Bertsch D.L. , Dingus B.L. , Esposito J. A. , Fichtel C.E. , Hartman R.C. , Hunter S.D. , Sreekumar P. , Chiang J. , Fierro J. M. , Lin Y.C. , Michelson P.F. , Nolan P.L. , Kanbach G. , Mayer-Hasselwander H.A. , Montigny C.V. , Radecke H.-D , Kniffen D.A. , Mattox J.R. , Schneid E.J.
Published: July 2016

The Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory has detected more than 20 Active Galactic Nuclei (AGN) at photon energies above 30 MeV.
AGN Variability and VLBI
Authors: Bååth L. B.
Published: July 2016

This contribution discusses the connection between variability in radio and optical with structural variations observed with VLBI. Structural changes do not have to start in the core, and intensity variations may be caused by components in the jet outside the core. The scenario is probably more complicated than present day theories assume.
The Multiwavelength Spectra of CEN A, NGC 4151, 3C273, 3C279
Authors: Odenwald Sten , Gehrels Neil , Howard Sethanne
Published: July 2016

We present SEDs for Cen A, NGC 4151, 3C273 and 3C279 with new results from the CGRO. The spectra cover 16 orders of magnitude in v, radio to γ-ray, over 20 years of observations. These 4 galaxies represent a Seyfert, a FSRG and 2 blazars. The γ-ray data indicate two classes of AGN. At γ-ray energies Type 1 Seyferts and radio galaxies have quantitatively different properties from blazars.
Simultaneous Observations of Seyfert 1 Galaxies by IUE, ROSAT and GINGA
Authors: Orr A. , Walter R. , Courvoisier T. J.-L. , Fink H. H. , Makino F. , Otani C. , Wamsteker W.
Published: July 2016

Simultaneous observations of 8 Seyfert 1 type AGN (Fairall-9, Mrk 590, NGC 4051, 3C 273, NGC 5548, Mrk 841, Q 1821+643 and 3C 390.3) obtained with ROSAT and IUE (RIASS program), and for 5 sources (Fairall-9, NGC 4051, 3C 273, Mrk 841 and Q 1821+643) with Ginga, have been analysed with the aim of describing the UV to soft X-ray spectral component in these sources.
On the Correlation of the FIR and Radio Radiation of Spiral Galaxies
Authors: Tovmassian H. M.
Published: July 2016

The comparison of the Byurakan classification of central parts of galaxies with the results of their radio observations showed that there is a definite correlation: the radio emission is more often observed in those galaxies which were suggested to have active nuclei.
Radiative Signatures of Neutron Beams in AGN
Authors: Ekejiuba Ifeanyi E.
Published: July 2016

The escape of relativistic neutrons from their production region can have various consequencies for the morphology of active galaxies. The phenomena of luminosity gaps and radio jet lighting in extragalactic radio sources (EGRSs) fit into the model that employs relativistic neutrons as the vector for particle and energy transport out of the central engines of AGNs. The central radio gaps reveal themselves as regions of relativistic neutron beam transport. The relativistic neutrons, which decay in flight after traveling for ∼ 103 γn s, produce secondaries which are responsible for the radio jet lighting and the associated phenomena in EGRSs.
The Nucleus of Our Home Galaxy: A Remnant of an Active or a Starburst Galaxy?
Authors: Ozernoy Leonid M.
Published: July 2016

To resolve the above dilemma, two essentially different approaches are undertaken: First, a new, detailed analysis of the entire radiation spectrum of Sgr A∗, from radio band up to gamma-rays, is reviewed, which enables us to put substantial constraints on the mass of a putative black hole. The derived upper limit turns out to be too small to allow the black hole to serve as an ‘engine’ for a Seyfert galaxy. Second, analyses of recent data on the 10 KeV gas in the central 200 pc and on star formation history at the Galactic center both make a star burst the likely episode in a recent past. Taken together, the two approaches seem to indicate that the history of the central part of our Galaxy can be better described as that of a starburst, rather than a Seyfert, galaxy.
Electron Energy Distributions of AGNs in the Thin Synchrotron Limit. I. the Method
Authors: Salas Luis , Cruz-González Irene , Carrasco Luis
Published: July 2016

We develop a new method called “Inverse Synchrotron Transform” (IST) to study the spectral energy distributions of AGNs. We demonstrate that it is possible to use Bayes Theorem for conditional probabilities to derive a self-consistent solution for the electron energy distribution (EEDs), starting from the observed spectral energy distributions (SEDs) and the assumption that the only physical process involved is thin synchrotron radiation. We test the IST method and find that it allows to distinguish among different EEDs that produce SEDs which nevertheless seem very similar. We apply the method to multifrequency simultaneous observations of AGNs (paper II, this conference).
A Simple Mhd Model for One-Sided Jets
Authors: Bodo G. , Trussoni E. , Chagelishvili G.
Published: July 2016

The one-sideness observed in several extragalactic jets is usually explained by the Doppler boosting effect in a pair of relativistic beams, moving almost parallel to the line of sight. However jets could be intrinsically asymmetric if magnetically driven from the accretion disk surrounding the central black hole. Wang et al. (1992) have shown that a combination of odd and even magnetic structures could lead to different Poynting fluxes in the two hemispheres of the inner nucleus. However, without any peculiar assumption, it can be shown that intrinsic one-sideness can be simply related to the symmetry properties of the MHD equations.