bluuebunny/crossref_metadata_2025 huggingface dataset:
The IUE orbit of γ2 Velorum
Authors: Lloyd Chris , Stickland David J.
Published: July 2016

Using IUE-SWP spectra, an orbital solution is derived for both components in the γ2 Velorum, which supports the lower mass of the O star found previously.
Simulating a White Dwarf dominated Halo
Authors: Brook C.B. , Kawata D. , Gibson B.K.
Published: July 2016

Halo initial mass functions (IMFs) heavily biased toward white dwarf (WD) precursors (∼ 1 - 8M⊙) have been suggested as a suitable mechanism for explaining MACHO events. However, by simple chemical evolution argument, Gibson & Mould (1997; GM97) pointed out that such WD-heavy IMFs (wdIMF) cause the overproduction of carbon and nitrogen. We re-examine this problem using numerical simulations.
MSX Sources in the LMC: Dust-Enshrouded AGB Stars, Post-AGB Stars and PN
Authors: Wood P. R. , Cohen M.
Published: July 2016

The Midcourse Space (MSX) Experiment (Price 1995) detected large numbers of point sources in the LMC at 8.28 μm (Egan et al. 2001). Near-infrared J H K L imaging and monitoring of the 504 MSX sources in a region of size 3° x 3.5° covering most of the LMC bar has been carried out. Spectra have been taken for most of the post-AGB stars and a selection of the AGB stars and red supergiants.
Measuring Angular Diameters of Planetary Nebulae
Authors: Siódmiak Natasza
Published: July 2016

We have analysed about 350 Hα CCD images of PNe in order to measure their angular diameters. 3 different methods were used for calculations. Results and comments on each method are presented.
Westbrook's Molecular Gun: Discovery of Near-Infrared Microstructures and Molecular Bullets in AFGL 618
Authors: Ueta Toshiya , Fong David , Meixner Margaret
Published: July 2016

We present high-sensitivity near-IR images of a carbon-rich proto-planetary nebula, AFGL 618, obtained with the Infrared Camera and Spectrograph (IRCS) mounted on the 8.2m Subaru Telescope. The deep near-IR images have revealed “bullets” and “horns” extending farther out from the edges of the previously known bipolar nebulosities that consist of dust-scattered star light component and shock-excited line emission component. That these bullets and horns represent the positions from which [Fe II] IR lines arise is strongly suggested from the spatial coincidence between these near-IR microstructures and the optical collimated outflow structure observed by the recent HST/WFPC2 imaging, together with the previous detection of shock-excited, forbidden IR lines of atomic species at those locations. At these positions of the near-IR mincrostructures, we have also discovered CO clumps moving at > 200 km s-1 from our re-analysis of the existing 12CO J = 1 – 0 data obtained with the Berkeley-Illinois-Maryland Association (BIMA) interferometer array. These findings indicate that fast-moving CO clumps seem to be impinging upon the surrounding ambient circumstellar shell, thereby causing shocked emission regions which manifest themselves as the near-IR microstructures at the shock interface. To deepen our understanding of the connection between the near-IR microstructures and the CO outflow structure, we are currently conducting higher resolution observation in CO lines with the BIMA array.
2.5 Dimensional Radiative Transfer Modeling of Proto-Planetary Nebula Dust Shells with 2-DUST
Authors: Ueta Toshiya , Meixner Margaret
Published: July 2016

Our observing campaign of proto-planetary nebula (PPN) dust shells has shown that the structure formation in planetary nebulae (PNs) begins as early as the late asymptotic giant branch (AGB) phase due to intrinsically axisymmetric superwind. We describe our latest numerical efforts with a multi-dimensional dust radiative transfer code, 2-DUST, in order to explain the apparent dichotomy of the PPN morphology at the mid-IR and optical, which originates most likely from the optical depth of the shell combined with the effect of inclination angle.
Near-Infrared Spectroscopy of H2 in Proto-Planetary Nebulae
Authors: Kelly Douglas M. , Hrivnak Bruce J.
Published: July 2016

We measured 2.1 – 2.3 μm spectra for a fairly complete sample of known proto-planetary nebulae (PPN) at declinations greater than -30°. This spectral range includes the H2 emission lines 1-0 S(1), 1-0 S(0), 2-1 S(1), 2-1 S(2), and 3-2 S(3). We detected H2 emission from 16 of the 51 nebulae in our survey, including radiatively-excited H2 from several non-bipolar PPN.
Molecular Line Emission from the Young Planetary Nebula NGC 7027
Authors: Hasegawa Tatsuhiko I. , Kwok Sun
Published: July 2016

NGC 7027 has been observed in eleven molecular species (in seventeen transitions) in the 200 and 300 GHz bands with the James Clarke Maxwell Telescope (Hasegawa & Kwok 2001). The results include a first detection of C2H in this source. The observed spectra of HCO+, H13CO+, HCN, CN, C2H, and CO+ show line widths larger than that of bulk CO emission but coincident with the full width at detection limit of weak wings in CO spectra. The sizes of the HCO+, HCN, and CN emitting regions are 13″ in diameter at half-peak level, significantly smaller than that (60″) of the CO emitting region. The emission of all the observed molecules other than CO and 13CO must originate from a very small volume compared with the entire CO envelope of NGC 7027. Since the central 10″ region is an ionized region, the molecular emission region (except CO) must be geometrically thin (ΔR = 1″ – 2″) and must be close to the ionization front.
Abundances in Planetary Nebulae: Including ISO Results
Authors: Pottasch S. R. , Beintema D. A. , Salas J. Bernard , Feibelman W. A.
Published: July 2016

The far infrared nebular spectrum provides a valuable complement to the observed lines in other spectral regions. There are several reasons for this, the most important being the large increase in the number of ions observed, and the fact that the abundances found from these lines are relatively insensitive to the electron temperature. This leads to a more accurate determination of the abundances. To date, twelve PN have had abundances determined in this way. These results are summarized. The evolution of the central star is discussed in the light of these results.
Study of He II Raman Scattering Profiles in NGC 7027
Authors: Péquignot D. , Walsh J. R. , Morisset C.
Published: July 2016

Péquignot et al. (1997) reported the discovery of a broad spectral feature to the blueward of Hβ, centred at a wavelength of 4852Å, in NGC 7027. This was conclusively shown to arise from the Raman scattering of He++ (2–8) UV photons by neutral H, and was the first detection in a planetary nebula. Raman scattering features had previously been observed in symbiotic stars: Raman scattering of O VI by neutral H was discovered by Schmid (1992) and also found for He II by van Groningen (1993). The large width of the resulting feature is mainly due to the conservation of the line width in frequency during the scattering process.
Multi-polar Structures in Young Planetary and Protoplanetary Nebulae
Authors: Sahai Raghvendra
Published: July 2016

The imaging of young planetary and proto-planetary nebulae (PNe and PPNe) with unprecedented high angular resolution and dynamic range, using the Hubble Space Telescope, has led to the realisation that almost all of these objects are highly aspherical, with complex multipolar morphologies. The complexity, organization and symmetry of the morphological structures we find is forcing radical changes in, and inspiring fresh theoretical efforts to advance, our understanding of the mass-loss processes during late stellar evolution. In this paper, we review the HST data, and show some of the highlights of our imaging studies. Although the origins of many of the morphological features remains puzzling, we find that the general presence of multipolar structures support a model for PN formation in which the primary agent for shaping PNe are high-speed collimated outflows or jets which operate during the late AGB and/or early post-AGB evolutionary phase, and undergo episodic changes in their orientation (or collimated outflows operate quasi-simultaneously with different orientations).
A Search for Planetary Nebulae in M 33 and M 81
Authors: Magrini Laura , Perinotto Mario , Corradi Romano L.M. , Mampaso Antonio
Published: July 2016

We present a study of the PNe systems of two nearby galaxies: the spirals M 33 and M 81. The luminosity functions (PNLFs) for the two PNe systems were built and the distances to both galaxies were given (0.84 ± 0.09 Mpc to M 33 and 3.84 ± 0.41 Mpc to M 81). The behavior of PNe excitation was examined across both galaxies, finding no evidence for substantial differences in excitation between bulge and disk PNe, nor for variations along the galaxian disks.
Chemical Composition of Galactic Planetary Nebulae and HII Regions in Blue Compact Dwarf Galaxies: New Determination
Authors: Holovatyy V.V. , Havrylova N.V. , Melekh B.Ya.
Published: July 2016

The expressions of new ionization-correction factors (ICF) (see these Proceedings) are employed for the determination of chemical composition of the 200 galactic planetary nebulae(PN) and 43 HII regions in blue compact dwarf galaxies (BCDG). We have used PN spectra from different papers published previously (> 100) and HII region spectra from (Izotov, Thuan, & Lipovetsky 1.994, Izotov, Thuan, & Lipovetsky 1997, Thuan, Izotov, & Lipovetsky hys. J. 1995). Code DIAGN (Holovatyy et al. 1999) developed at Astronomical Observatory of Lviv National University is also used. Atomic data for determination of ne, Te and the ionic abundances (A+i/H+) were modified to be compatible with the CLOUDY94 code (Ferland G.J. 1999).
Discovery of Three Very Low Mass Binary Systems: An Adaptive Optics Survey of M6.0–M7.5 Stars
Authors: Siegler Nick , M. Close Laird , E. Mamajek Eric , Freed Melanie
Published: July 2016

We have used the adaptive optics system Hōkūpa'a at Gemini North to search for companions from a flux-limited (Ks > 12) survey of 30 nearby M6.0–M7.5 dwarfs. Our observations, which are sensitive to companions with separations > 0.1″ (~ 2.8 AU), detect 3 new binary systems. This implies an overall binary fraction of 9±4% for M6.0–M7.5 binaries. This binary frequency is somewhat less than the 19±7% measured for late M stars and ~ 20% for L stars, but is still statistically consistent. However, the result is significantly lower than the binary fractions observed amongst solar mass main sequence stars (~60%) and early M stars (~35%).
Companions to Young Stars
Authors: Lowrance Patrick J. ,   the NICMOS Environments of Nearby Stars team & STIS 8176 team
Published: July 2016

Brown dwarfs occupy the important region in the mass range between stars and planets. Their existence, ambiguous until only recently, and their properties give insight into stellar and planetary formation. We present statistical results of an infrared, coronagraphic survey of young, nearby stars that includes probable companions to three young G-type stars, G1 503.2 (G2V), HD 102982 (G3V), and G1 577 (G5V). The companion to G1 577 is a possible binary brown dwarf, according to evolutionary models. A dynamical determination of the components' masses will be achievable in the near future and will provide an excellent test of the predictive ability of the evolutionary models.
X-ray Emission from Old and Intermediate Age Brown Dwarfs
Authors: Stelzer Beate , Neuhäuser Ralph
Published: July 2016

We report on two recent XMM-Newton observations of Brown Dwarfs in the Pleiades cluster and in the field aiming to constrain the age dependence of X-ray emission from substellar objects.
Binaries among the WN population in the Magellanic Clouds
Authors: Foellmi Cédric , Moffat Anthony F.J. , Guerrero Roncel Martín A.
Published: July 2016

We have undertaken a large and extensive spectroscopic survey of WNE stars both in the SMC and LMC with various 2m and 4m telescopes, reaching a total of 78 nights, spread over three years, and obtaining over 1500 long-slit spectra of medium resolution. The first goal is a systematic search for binaries via periodic radial-velocity variations. We enlarged our dataset with photometric data from the ogle and macho databases, and with archival X-ray data from the ROSAT and Chandra satellites.
The ejecta of η Carinae
Authors: Gull Theodore R. , Davidson Kris , Ishibashi Kazunori ,   the η Carinae HST-stis Team
Published: July 2016

Since New Year's Eve 1998, we have been studying η Carinae and the surrounding complex ejecta with the HST-stis instrument. Angular resolution of 0.1″ and spectral resolving power R = 5000-118000 have revealed a multitude of emission and absorption lines identified from many heavy elements. Some data was obtained during the 1998.0 spectral minimum and now we have an HST Treasury proposal accepted to follow the star and ejecta changes across the 2003.5 minimum. To date, we identify the Homunculus as an outer reflection nebula, an internal ionized Little Homunculus, a very small shell (0″.74 in diameter), the Weigelt-blobs, and a peculiar structure called the strontium emission filament. More recently an even smaller extended structure (0″.14 diameter) has been found to surround the Central Source as seen in the ultraviolet.
Post-outburst polarimetry of the binary HD 5980 (O4-6/LBV+WN3): rapid density enhancements along the polar axis and equatorial plane
Authors: Villar-Sbaffi Alfredo , Moffat Anthony F.J. , St-Louis Nicole
Published: July 2016

In 2001, we carried out a series of polarimetric observations of the SMC Wolf-Rayet binary HD 5980 near secondary eclipse, in order to study the mass-outflow of the system. Our observations revealed the presence of intense density enhancements along the poles and equatorial plane, that fluctuate on a very short timescale.
Distinction between distribution of masses of Wolf-Rayet stars and that of relativistic objects
Authors: Cherepashchuk Anatol M.
Published: July 2016

The final masses MCO,f for the CO-cores of WR stars with known masses are calculated taking into account mass-dependent mass loss of WR stars and clumping structure of the WR wind which allows the mass loss rate to be decreased by a factor of 3. The masses of MCO,f lie in the range (1-2) - (20-44)M⊙ and have continuous distribution in contrast with distribution of masses Mx of relativistic objects. The distribution of Mx seems to be bimodal with a gap in the range Mx = 2-4 M⊙. A mean CO-core mass <MCO,f = 7.4-10.3 M⊙ is close to that of black holes: <MBH = 8-10 M⊙. Difference between distributions of MCO,f and Mx allows us to suggest that the nature of a formed relativistic object (neutron star, black hole) is determined not only by the mass of a progenitor but also by some other parameters: rotation, magnetic field, etc.
The very rich massive post-main-sequence star population of the open cluster Westerlund 1
Authors: Negueruela Ignacio , Clark J. Simon
Published: July 2016

We report the discovery of a population of Wolf-Rayet stars in the young Galactic open cluster Westerlund 1. In an incomplete shallow spectroscopic survey, we find six nitrogen-rich (WN) and five carbon-rich (WC) WR stars. We also confirm the presence of a large population of yellow supergiants, some of which are candidate hypergiants. Given this population, Westerlund 1 is likely to be one of the most massive young clusters in the Local Group.
The impact of close binary evolution on the properties of the WR-bump emission lines of Wolf-Rayet galaxies
Authors: Van Bever Joris , Vanbeveren Dany
Published: July 2016

We present the results of a study on the behaviour of the blue and red WR emission bumps (around 4650Å and 5808Å) and of the nebular contribution to He ii λ4686 in evolving young starburst regions (such as Wolf-Rayet galaxies), containing a non-negligible binary population. Calculations were made for solar metallicity and 1/20 solar. The population synthesis program uses an extended library of stellar evolutionary tracks of single stars and binaries, computed using the most recent stellar wind mass loss rates during RSG, LBV and WR stages. In the case of binaries, we account in detail for the effects of Roche lobe overflow, mass transfer and mass accretion, common envelope evolution, the spiral-in process, asymmetric kicks to neutron stars as a result of their supernova explosion, etc. This research is part of a more extensive project to explore every possible impact of massive binaries on stellar populations.
Radio observations of interstellar bubbles surrounding massive stars
Authors: Cappa Cristina E. , Arnal E. Marcelo , Cichowolski Silvina , Goss W. Miller , Pineault Serge
Published: July 2016

We show radio continuum observations of the WR ring nebulae around WR 101 and WR 113 obtained using the VLA and H i 21 cm line data of the interstellar bubble around the O type stars BD +24° 3866 and BD+25° 3952 obtained with the DRAO Synthesis Telescope. We review previous radio continuum and H i line results toward WR and O-type stars.
New line-blanketed model atmospheres and their impact on synthesis models
Authors: Smith Linda J. , Norris Richard P.F. , Crowther Paul A.
Published: July 2016

A new grid of ionizing fluxes for O-type and Wolf-Rayet stars is presented for use with evolutionary synthesis codes and analyses of single star H ii regions. A total of 230 expanding, non-LTE, line-blanketed model atmospheres have been calculated for five metallicities (0.05, 0.2, 0.4, 1 and 2 Z⊙). We have used the wm-basic code of Pauldrach et al. (2001) for O-type stars and the cmfgen code of Hillier & Miller (1998) for WR stars. The stellar wind parameters are scaled with metallicity for both O-type and WR stars. The ionizing fluxes of the new models, incorporated into the evolutionary synthesis code STARBURST99 (Leitherer et al. 1999), are compared with the predictions of the original starburst99 and Schaerer & Vacca (1998) for an instantaneous burst. We find large changes in the output ionizing fluxes as a function of age, especially below the He+ edge. In contrast to previous studies, nebular He ii λ4686 will be at, or just below, the detection limit in low metallicity starbursts during the WR phase. The new models have lower fluxes in the He i continuum for Z ≥ 0.4 Z⊙ and ages ≤ 7 Myr because of the increased line-blanketing. The accuracy of the new model atmosphere grid is tested by constructing photo-ionization models for an H ii region where the ionizing flux is provided by an instantaneous burst. The new models occupy the same region in nebular diagnostic diagrams as the observational data of Bresolin et al. (1999), particularly during the WR phase. The new model grid and updated starburst99 code can be downloaded from http://www.star.ucl.ac.uk/starburst.
Modeling the strings in the outer regions of η Carinae
Authors: Redman Matt P. , Meaburn John , Holloway Anthony J.
Published: July 2016

The narrow high-speed optical filaments emerging from the Homunculus of η Carinae are modelled as resulting from the passage of ballistic ‘bullets’ of material through the dense circumstellar environment. In this explanation, the string is the decelerating flow of ablated gas from the bullet. Many of the observed properties of the strings are accounted for in this simple model.
MUSICOS 92 observations of Θ2 Tauri
Authors: Kennelly E.J. , Walker G.A.H. ,   The Musicos Team
Published: July 2016

MUSICOS (MUlti-SIte COntinous Spectroscopy) is an international collaboration interested in areas of astronomical research requiring continuous, high-resolution spectroscopy. The MUSICOS stategy has been 1) to organize international campaigns (Catala et al 1993), 2) to build a prototype fibre-fed, high-resolution, echelle spectrograph (Baudrand & Böhm 1992), and 3) to install duplicates of the MUSICOS spectrograph on 2m class telescopes around the world. Stages 1 and 2 have been completed. Preliminary results on θ2 Tau from the second MUSICOS campaign are presented here.
Radiation-accellerated ions in hot star winds: heating and “turbulence” effects
Authors: Vilkoviskij E. Ya
Published: July 2016

In the papers by Vilkoviskij (1981), Vilkoviskij and Tambovtzeva (1988) and Springmann and Pauldrach (1992) it was shown that ions can reach velocities relative to the wind plasma when the radiation pressure force exceeds the protons frictional force.
The McDonald Observatory Planetary Search Program: Past, Present, and Future
Authors: Cochran William D. , Hatzes Artie P.
Published: July 2016

We present a summary of the McDonald Observatory Planetary Search program. We first summarize results on the star ∊ Eridani, in which we combine McDonald Observatory data with data from CFHT, Lick, and ESO, to detect a planet in orbit around this very nearby star. We then concentrate on results from the first 4 years of the Texas Hyades survey using the HIRES spectrograph on Keck 1. The Hyades constitute a very homogeneous sample of stars, in which the major independent variable is the stellar mass. In this survey, we have achieved 3 m s−1 internal error on a sample of about 100 Hyades dwarfs. We discuss the rms radial velocity jitter of the sample stars, and its relationship to spectral type, stellar rotation, and chromospheric activity.
Supportive Evidence for a Brown Dwarf Solar Companion
Authors: Matese John J.
Published: July 2016

We have previously given evidence based on Oort cloud comet orbital elements which suggested that there may be a Jovian-mass brown dwarf in our solar system. An extended cometary database is now available. The analyses have been repeated and we find that the set of statistically significant correlated anomalies is enhanced. We also respond to unsupported objections that have been raised to this conjecture. If real, the wide-binary object would constitute a natural dynamical intermediary between gas giant planetary objects and isolated objects.
Frequency Map and Global Dynamics in Planetary systems: Short Period Dynamics
Authors: Robutel Philippe , Laskar Jacques
Published: July 2016

Frequency Map Analysis (FMA) (Laskar, 1990, 1999) is a refined numerical method based on Fourier techniques which provide a clear representation of the global dynamics of multi-dimensional systems, which is very effective for systems of 3 degrees of freedom and more, and was applied to a large class of dynamical systems. FMA requires only a very short integration time to obtain a measure of the diffusion of the trajectories, and allows to identify easily the location of the main resonances. Using this method, we have performed a complete analysis of massless particles in the Solar System (Robutel & Laskar 2001), from Mercury to the outer parts of the Kuiper belt (90 AU), for all values of the eccentricities, and several values for the inclinations. This provides a complete dynamical map of the Solar System, which is, in this first step, restricted to mean motion resonances. The dynamics of a planetary system which all the bodies have no zero mass can be studied with the same methods: an application to the JupiterSaturn system can be fined in (Robutel & Laskar 2002). We present here the application of this method to the understanding of the dynamics of the newly discovered v-Andromedae system.
Ground interferometric searches
Authors: Glindemann A. , Delplancke F. , Kervella P. , Paresce F. , Richichi A. , Schöller M.
Published: July 2016

In this article, we discuss the instrumental requirements for planet searches from the ground. We review several methods and their fundamental limitations comparing the direct measurement of the visibility function (both modulus and phase) to astrometry and nulling interferometry. In particular, we will take the Very Large Telescope Interferometer (VLTI) as an example. The VLTI is an excellent facility for planet searches from the ground since it has both large apertures and long baselines, providing high SNR and milli-arcsecond resolution.
The IDV Source BL Lac 0716+714, is it Fast or Slow?
Authors: Tian W.W. , Krichbaum T.P. , Witzel A. , Zensus J.A. , Kraus A. , Britzen S.
Published: July 2016

We investigate the structural evolution of the IDV source BL Lac 0716+714 from 10 epochs of global VLBI and VLBA observations. Our study reveals two possible component identification schemes, in which the jet components move either slow or fast. Although the fast motion would fit better to the observed IDV, the quality of our data does not allow a final decision between the slow and the fast picture.
The Quasar 3C 345 at the Highest Resolution with mm-and Space-VLBI
Authors: Klare J. , Zensus J.A. , Krichbaum T.P. , Lobanov A.P. , Ros E.
Published: July 2016

The quasar 3C345 is one of the best examples of extra-galactic jet with superluminal components moving on helical paths. To get better constraints on the jet physics, we have imaged the source at the highest possible resolution, using mm-VLBI and space-VLBI observations. We observed 3C 345 at 5 different epochs so far (1 epoch with 3-mm ground VLBI, and 4 epochs with space VLBI at 6cm and 18 cm). These measurements expand significantly our ongoing monitoring of 3C 345. In this contribution, we discuss the properties of the jet and its moving components in the immediate vicinity of the core (< 3 mas).
Mapping the Dynamics of the Quasar 3C 48
Authors: Chatzichristou Eleni T.
Published: July 2016

The archetypical, nearby (z=0.37) quasar 3C 48 is an unusual CSS radio source with excess far-IR emission, whose one-sided radio jet is aligned with the extended ionized emission and a putative second nucleus. Because of its high AGN luminosity and proximity, 3C 48 is a good candidate to search for kinematic signatures of the radio jet-gas coupling and/or of a recent interaction. The radio morphology and our ground-based integral field spectroscopy suggest that the jet is interacting with its immediate environment. Using STIS aboard HST in several slit positions within the central 1”, we map the kinematics and physical conditions of the extended emission line gas and their relations to near-nuclear star forming regions found in existing HST images.
The Central Radio Gap and the Equatorial Emission Region in SS433
Authors: Paragi Z. , Fejes I. , Vermeulen R.C. , Schilizzi R.T. , Spencer R.E. , Stirling A.M.
Published: July 2016

The radio-jet X-ray binary SS433 was observed at five epochs in 1998 by the very long baseline interferometry (VLBI) technique at five frequencies ranging from 1.6 to 22 GHz. The innermost region of the source on milliarcsecond scales (1 mas = 5 AU) is resolved into an eastern and a western core-jet component, well separated by the Central Radio Gap (25-30 AU projected size), where the binary stellar system is located. We suggest that the radio gap is caused by local synchrotron self-absorption and external free-free absorption in an ionized medium, which has a disk-like geometry. On 100 AU scales we observe the Equatorial Emission Region, oriented roughly perpendicularly to the jets, with variable morphology at different epochs. Both of these phenomena could be interpreted with a mass outflow from the system, concentrated in the orbital plane of the binary.
Accretion and Outflow Traced by H2O Masers in the Circinus AGN
Authors: Greenhill L.J. , Moran J.M. , Booth R.S. , Ellingsen S.P. , McCulloch P.M. , Jauncey D.L. , Norris R.P. , Reynolds J.E. , Tzioumis A.K. , Herrnstein J.R.
Published: July 2016

The first VLBI images of H2O maser emission in the Circinus Galaxy AGN show both a warped, edge-on accretion disk and an outflow 0.1 to 1 pc from the central engine. The inferred central mass is 1.3 × 106 M⊙, while the disk mass may be on the order of 105 M⊙, based on a nearly Keplerian rotation curve. The bipolar, wide-angle outflow appears to contain “bullets” ejected from within < 0.1 pc of the central mass. The positions of filaments and bullets observed in the AGN ionization cone on kpc-scales suggest that the disk channels the flow to a radius of ∼ 0.4 pc, at which the flow appears to disrupt the disk.
Statistics of Large Diameter Radio SNRs
Authors: Asvarov Abdul I.
Published: July 2016

It is shown that if the recently discovered hypernova events are intrinsically energetic spherically symmetric explosions of massive stars than they can leave after themselves very large diameter (up to 500 pc) nonthermal radio shells with spectral properties like ordinary shell type radio supernova remnants (SNRs). The properties of such shells are modeled and compared with the statistics of large diameter SNRs.
Current Status of the VSOP-2 Mission
Authors: Hirabayashi H. , Murata Y. , Edwards P.G. , Murphy D.W. , Inoue M. , Kobayashi H. , Kameno S.
Published: July 2016

The VLBI Space Observatory Programme (VSOP) is the first dedicated Space-VLBI mission. We report here on the planning for a second generation mission which builds on and extends the successful collaborations established for the VSOP mission, and which aims to improve both resolution and sensitivity by a factor of ∼10.
A Spectroscopic and Photometric Survey for Pre-Main Sequence Binaries
Authors: Guenther Eike W. , Joergens Viki , Neuhäuser Ralph , Torres Guillermo , Stout Batalha Natalie , Vijapurkar Jyotsna , Fernández Matilde , Mundt Reinhard
Published: July 2016

We give here an overview of the current state of our survey for pre-main sequence spectroscopic binaries. Up to now we have taken 739 spectra of 250 pre-main sequence stars. We find that 8% of the stars show significant radial velocity variations, and are thus most likely spectroscopic binaries. In addition to the targets showing radial velocity variations, 6% of the targets are double-lined spectroscopic binaries i.e., the total fraction of spectroscopic binaries is expected to be about 14%. All short-period SB2s are monitored photometrically in order to search for eclipses. An eclipsing SB2 would allow the direct measurement of the masses of both stellar components. Measurements of the stellar masses together with determinations of the stellar radii are a crucial test of evolutionary tracks of pre-main sequence stars.
Fragmentation and Star Formation in Turbulent Cores
Authors: Klein Richard I. , Fisher Robert , McKee Christopher F.
Published: July 2016

We examine the conditions under which binary and multiple stars may form out of turbulent molecular cloud cores using high resolution 3-D, adaptive mesh refinement (AMR) hydrodynamics (Truelove et al., 1997, 1998; Klein, 1999). We argue that previous conclusions on the conditions for cloud fragmentation have limited applicability, since they did not allow for the nonlinear density and velocity perturbations that are ubiquitous in molecular cloud cores. Over the past year, we have begun to simulate the evolution of marginally stable, turbulent cores. These models have radii, masses, density contrasts, turbulent linewidths, and projected velocity gradients consistent with observations of low-mass molecular cloud cores. Our models are evolved in time under self-gravitational hydrodynamics with AMR using a barotropic equation of state that models the transition from an isothermal to an adiabatic equation of state. We examine several properties of the resulting proto-stellar fragments and discuss the qualitative nature of the fragmentation process in realistic cloud cores: the transition from single to binary and multiple stars; the formation of misaligned binary systems; and the role played by filament formation in the formation of stars.
Accretion onto Pre-Main Sequence Binary Stars: The Circumstellar Environment
Authors: Mathieu Robert D.
Published: July 2016

Observations show that mass accretion can occur at the surfaces of stars in young binaries of all separations. Given that resonant torques have been expected to clear gaps and dam the inward flow of material from circumbinary disks, this result begs the question of how mass accretion is supplied in binary systems. In this paper we address this question in the context of close binaries. Spectral energy distributions indicate that dynamical clearing is not complete for close binaries having massive circumbinary disks. High-resolution infrared spectra of CO rotational and ro-vibrational lines have also detected small amounts of gas which can be located in the region of dynamical clearing. Thus we have signatures of matter from the circumbinary environment through the predicted gap region to the stellar surfaces. We suggest that accretion streams may supply both dynamically cleared regions and circumstellar disks.
Pre-Main Sequence Models for Low-Mass Stars and Brown Dwarfs
Authors: Baraffe Isabelle , Chabrier Gilles , Allard France , Hauschildt Peter
Published: July 2016

We present evolutionary models for young low mass stars (m ≤ 1M⊙) based on recent improvement of the theory: equation of state, atmosphere models, etc. We concentrate on early evolutionary phases from the initial deuterium burning phase to the zero-age Main Sequence. Evolutionary models for young brown dwarfs are also presented. We discuss the uncertainties of the present models. We analyse the difficulties arising when comparing models with observations for very young objects, in particular concerning the problem of reddening.
The MAP Mission
Authors: Wright Edward L.
Published: July 2016

The Microwave Anisotropy Probe (MAP) is scheduled for launch in 2001. This mission will measure the anisotropy of the cosmic microwave background in five frequency bands from 22 to 90 GHz. The angular resolution varies with frequency from 0.93° to < 0.23°. The sensitivity should reach a standard deviation of 20 μK in each 0.3° pixel on the sky. MAP will observe from the Earth-Sun L2 point using a four-fold modulation scheme to minimize systematic errors. The 2-year planned duration will allow for 4 complete coverages of the sky. By observing the CMB angular power spectrum, MAP will tell us the initial conditions for the galaxy formation that produced the extragalactic infrared background.
The Extragalactic Infrared Background and its Cosmological Implications – Impressions and Reflections
Authors: Longair Malcolm S.
Published: July 2016

Many of the key issues facing astrophysicists and cosmologists can be uniquely addressed by observations in near and far infrared, millimetre and submillimetre wavebands. Some highlights of IAU Symposium No. 204 are reviewed and likely future directions of observation, interpretation and theory are discussed.
Stellar Mixing from Galactic and Magellanic Cloud Planetary Nebulae Abundances
Authors: Clegg R. E. S.
Published: July 2016

The mixing and nucleosynthetic processes which occur in the main-sequence and red giant stages of evolution and which can affect measured PN abundances are discussed. It is suggested that samples of planetary nebulae contain a sufficient range of progenitor stars' initial metallicities, angular momenta, binarity, etc. so as to explain the large scatter always seen in abundance diagrams for PN samples. CNO abundances in the Galactic disk and in the Magellanic Clouds are reviewed. New results for nebular abundances and central star properties in the Clouds are given. The current red giant population in the Clouds mix out more 12C per star than their Galactic disk counterparts.
Statistics Of Quasar Lensing Caused By Clusters Of Galaxies
Authors: Tomita K.
Published: July 2016

Cosmological lens statistics was studied first by Turner, Ostriker, & Gott (1984), and developed by Hinshaw & Krauss (1987), Gott, Park, & Lee (1989), Turner (1990), Krauss & White (1992), and Wallington & Narayan (1993). The expected number of lensed quasars in general quasar catalogs was examined by Fukugita & Turner (1991), Kochanek (1991), and Fukugita et al. (1992), and the number expected in the HST Snapshot Survey (Bahcall et al. 1992, Maoz et al. 1992, 1993) was examined by Maoz & Rix (1939) and Kochanek (1993). In most of these studies, galaxies were assumed to be the lenses, and clusters of galaxies played only auxiliary roles. As a result, the expected number of lensed quasars with separations larger than 3 arcsec is negligibly small compared to the total number of lenses. However, about 33% of observed lensed quasars have image separations larger than 3 arcsec (Maoz et al. 1993, Refsdal & Surdej 1994). This observational fact is very important.
Mapping Dark Matter Near Galaxy Clusters
Authors: Tyson J.A.
Published: July 2016

Weak gravitational lensing can provide a direct measure of mass overdensity on scales of kpc to several Mpc. The total mass and light distribution in a survey of 32 clusters of galaxies is reviewed. The mass is derived from apodized inversion of thousands of weak lensing arclets in deep CCD shift-and-stare exposures to uniform faint surface brightness in two colors. Rest frame V band mass-to-light ratios of several hundred h solar are found.
Real-Time Detection Of Gravitational Microlensing
Authors: Pratt M.R. , Alcock C. , Allsman R.A. , Alves D. , Axelrod T.S. , Becker A. , Bennett D.P. , Cook K.H. , Freeman K.C. , Griest K. , Guern J. , Lehner M. , Marshall S.L. , Peterson B.A. , Quinn P.J. , Reiss D. , Rodgers A.W. , Stubbs C. , Sutherland W. , Welch D.L. ,   (The MACHO Collaboration)
Published: July 2016

Real-time detection of microlensing has moved from proof of concept in 1994 (Udalski et al. 1994a, Alcock et al. 1994) to a steady stream of events this year. Global dissemination of these events by the MACHO and OGLE collaborations has made possible intensive photometric and spectroscopic follow up from widely dispersed sites confirming the microlensing hypothesis (Benetti 1995). Improved photometry and increased temporal resolution from follow up observations greatly increases the possibility of detecting deviations from the standard point-source, point-lens, inertial motion microlensing model. These deviations are crucial in understanding individual lensing systems by breaking the degeneracy between lens mass, position and velocity. We report here on GMAN (Global Microlensing Alert Network), the coordinated follow up of MACHO alerts.
Population Synthesis Models
Authors: Bruzual A. Gustavo
Published: July 2016

Increasingly complex population synthesis models have been developed during the last few years. Among the different authors working in the field, these groups have been particularly active: Arimoto & Yoshii (1987), Guiderdoni & Rocca-Volmerange (1987), Buzzoni (1989), Fritze-v. Alvensleben & Gerhard (1994), Bressan, Chiosi, & Fagotto (1994), Bruzual & Chariot (1993, 1995). The basic astrophysical ingredients used in these models are the stellar evolutionary tracks and the stellar spectral libraries (either empirical or theoretical). The computational algorithms are different in each set of models, but, one way or the other, these models depend on the same adjustable parametric functions: (1) the stellar initial mass function (IMF); (2) the star formation rate (SFR); and (3) the rate of chemical enrichment (in some models Z = Z⊙ = constant). Most of the recent codes use the isochrone synthesis algorithm, which allows to compute the evolution of a simple stellar population (SSP), and from it, by a convolution integral, the properties of more complex composite stellar populations (CSP).
Baryonic Dark Halos: a model with MACHOS and cold gas globules
Authors: Gerhard Ortwin , Silk Joseph
Published: July 2016

The dark matter in the halos of galaxies may well be baryonic, and much of the mass within them could be in the form of clusters of substellar objects within which are embedded cold gas globules. Such halos might play an active role in galaxy formation and evolution.
Statistics of HI Extents of Irregular Galaxies
Authors: Hoffman G. Lyle
Published: July 2016

Using the 3.′2 Arecibo beam, we have mapped the HI envelopes of a sample of 70 irregular galaxies (Sdm, Sm, Im and BCD), including 45 from the Virgo Cluster Catalog, 14 Field galaxies at similar redshifts, and 11 Nearby dwarfs chosen to give a complete sample out to 6 Mpc, within the Arecibo declination range. To explore correlations among variables characterizing the size and dynamics of these galaxies, we have combined this sample with all other mappings (multiple single beams and synthesis array) of irregulars and of spiral galaxies spanning the same redshift range (out to about 20 Mpc) available in the literature. In all, there are 128 mapped dwarfs and 119 mapped spirals in this dataset. We obtain the following correlations: rH,max = (2.75 ± .15)r25(0.890±.034) where both HI and optical radii are in kpc; LB = (3.59±.80) × 106rgm(2.70±.11) where LB is in solar luminosities and rgm is the geometric mean of rH,max and r25; LB = (125±36) Vc(3.62±.19) where the rotation speed is in km s−1; MH = (9.3 ± 1.1) × 106rgm(1.977±.056) where the HI mass is in solar units; and LB = (1.9+2.7−1.1) × 10−3Mndyn(1.164±.043) where Mdyn = Vc2rgm/G.
The Tilt of the Fundamental Plane of Elliptical Galaxies: Dynamical and Structural Effects
Authors: Lanzoni B. , Ciotti L. , Renzini A.
Published: July 2016

We explore several structural and dynamical effects on the projected velocity dispersion as possible causes of the fundamental plane (FP) tilt of elliptical galaxies (Ciotti, Lanzoni & Renzini, 1995). Specifically, we determine the size of the systematic trend along the FP in the orbital radial anisotropy, in the dark matter (DM) content and distribution relative to the bright matter, and in the shape of the light profile that would be needed to produce the tilt, under the assumption of a constant stellar mass to light ratio. Spherical, non rotating, two-components models are constructed, where the light profiles resemble the R1/4 law. For these we can exclude orbital anisotropy as the origin of the tilt, while a systematic increase in the DM content and/or concentration may formally produce it. Also a suitable variation of the light profile can produce the desired effect, and there may be some observational hints supporting this possibility. However, fine tuning is always required in order to reproduce the tilt, while preserving the tightness of the galaxies distribution about the FP.
Impulsive (Flash) Phase of Solar Flares: Hard X-Ray, Microwave, EUV and Optical Observations
Authors: Kane S. R.
Published: July 2016

Recent observations of impulsive hard X-ray, microwave, EUV and optical emissions during solar flares are briefly reviewed in order to deduce the characteristics of the impulsive (flash) phase phenomenon in small solar flares particularly from the point of view of the acceleration of electrons and their role in producing the various impulsive phase emissions. Observed and deduced characteristics of the various electromagnetic emission sources are summarized (Table II). The deduced characteristics of the electron acceleration process (Table III) indicate a process with high acceleration efficiency. The observations are found to be consistent with a model in which electrons are accelerated in a series of short pulses each lasting for ≲ 1 s and the accelerated electrons provide the energy necessary for all the observed electromagnetic emissions produced during the flash phase of small solar flares. Models of the impulsive phase emissions in which energetic electrons play a prominant role are examined and crucial tests to check the accuracy of these models are indicated (Table IV).
Observations of Split-Band Harmonic Type II Bursts with the Culgoora Radioheliograph at 80 and 160 MHz
Authors: Nelson G. J. , Sheridan K. V.
Published: July 2016

(Solar Phys.) When the Culgoora radioheliograph started operating at both 80 MHz (the initial frequency) and 160 MHz (from May 1972) it became possible for the first time to make simultaneous observations of the fundamental and second harmonic sources in type II bursts. Three such bursts, each having harmonically related split-bands, have been observed so far. The new 80 and 160 MHz heliograph observations are illustrated in Figure 1. Since all three events had split-band structure the results are presented separately for the lower- (l) and upper- (u) frequency components and differences between the source positions in the two components will be highlighted. For the burst of 1973 May 19, which was observed at large zenith angles, calculated corrections for ionospheric refraction – approximately 1′ to 2′ for the 80 MHz sources – have been applied; the remaining two events are presented as observed since the refraction effects are thought to be small.
Acceleration, Containment and Emission of High Energy Flare Particles: Radio Evidence
Authors: Boischot A.
Published: July 2016

The existence of non thermal radio bursts provide evidences for the acceleration of electrons in the solar atmosphere.

It is shown, from the characteristics of the bursts, that the electrons are accelerated in at least four different phases:

(1)

An impulsive phase which gives μib and III bursts.

(2)

A gradual phase which gives μIV and S1IV bursts.

(3)

A quasi-continuous phase which gives S2IV bursts and noise storms.

(4)

An acceleration by shock waves gives type II bursts.

(5)

Eventually, another shock-wave acceleration giving the moIV burst.
22. On the magnetic fields of novae and super-novae
Authors: Mustel E. R.
Published: July 2016

This paper is a development of the hypothesis, suggested earlier by the author, namely that novae possess a large general magnetic field. This hypothesis explains the following facts: (a) effects of the retardation of matter in novae before light maximum, (b) a preferential ejection of matter from novae in two diametrically opposite directions during an outburst, and (c) formation of rings and equatorial belts after light maximum, observed in N Aql 1918 and N Her 1934. These rings and belts are formed due to the fact that the general magnetic field of new stars deflects condensations of continuous ejection (the diffuse-enhanced and Orion spectra) towards the equator.

Magnetic fields inside novae must be ‘tangled’. This explains (a), as well as the difference between cases (b) and (c).

The structure of envelopes, ejected by novae, must reflect the presence of tangled magnetic fields. According to G. A. Shajn this is confirmed for super-novae, the envelopes of which may be studied in detail.
Revival, Recognition, Restitution: Indigenous Rights in the Eastern Caribbean
Authors: Strecker Amy
Published: July 2016

The idea that the indigenous peoples of the Caribbean islands became extinct has until recently dominated scholarly discourse and popular awareness. This “extinction” narrative served to justify the appropriation of indigenous lands during the colonial period, and its legacy continued into post-independence. In recent years, these misconceptions have been put under increasing scrutiny, not only by archaeological, historical, and ethnographic research but also, more importantly, by communities themselves. In Dominica, Saint Vincent, and Trinidad, communities are contesting negative stereotypes, reasserting their presence, and agitating for their human rights in the post-colonial islands states. This article discusses the acquisition of indigenous rights by descendant communities in the eastern Caribbean. It reveals the various degrees to which communities have gained state recognition and illustrates that while progress has been made in relation to recognition and cultural rights for communities in the islands, issues remain in relation to land security.
Listeria monocytogenescross-contamination of cheese: risk throughout the food supply chain
Authors: SAUDERS B. D. , D'AMICO D. J.
Published: July 2016

Listeria monocytogeneshas been the most common microbial cause of cheese-related recalls in both the United States and Canada in recent years. SinceL. monocytogenesis inactivated by pasteurization, the majority of these cases have been linked to environmental and cross-contamination of fresh-soft, soft-ripened, and semi-soft cheeses. Cross-contamination of foods withL. monocytogenesis a continuous risk throughout the food supply chain and presents unique challenges for subsequent illness and outbreak investigations. Reports on outbreaks of listeriosis attributed to cross-contamination downstream from primary processing help highlight the critical role of epidemiological investigation coupled with coordinated molecular subtyping and surveillance in the recognition and investigation of complex foodborne outbreaks. Despite their complexity, environmental sampling throughout the supply chain coupled with improved genotyping approaches and concomitant analysis of foodborne illness epidemiological exposure data are needed to help resolve these and similar cases more rapidly and with greater confidence.