bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution and explosion of Wolf-Rayet stars
Authors: Langer Norbert , Heger Alexander
Published: July 2016

We investigate the pre-supernova evolution of Wolf-Rayet stars. We discuss whether the separation of hydrogen-free, core collapse supernovae into Type Ic and Type Ib supernovae is related to the occurrence of ‘Case BB mass transfer’ in massive close binaries, especially since the new, smaller WR mass loss rates do not favor helium-poor progenitor models from massive single stars. We also discuss the influence of rotation on the formation, evolution and explosion of WR stars using new models for rotating massive stars that have been computed from zero age to core collapse. We compute the spin-down of (non-magnetic) WR stars due to their strong mass loss, and compare pulsar spin rates with our predictions. Finally, we discuss implications of our results for the rotation rate of Type Ib/c supernova progenitors in general, and for SN 1998bw and the ‘collapsar’ model for γ-ray bursts in particular.
Evolution of massive close binaries, compared to observations
Authors: Vanbeveren Dany
Published: July 2016

Since binaries can not be considered separately from single stars, we first present a brief summary of massive single star evolution. Next, we highlight massive close binary evolutionary facts that are important when massive close binaries are included in population (number) synthesis. Finally, we consider a few interesting test cases.
Chemical enrichment from Wolf-Rayet stellar winds
Authors: Meynet Georges
Published: July 2016

Stellar winds contribute together with supernovae explosions to the chemical enrichment of the interstellar medium. We recall how the metallicity dependence of the stellar winds implies a metallicity dependence of the stellar yields. We show that an increase of the initial angular velocity has different effects than an increase of the mass loss rates. Wolf-Rayet stars appear as important sources of 19F and 26Al. They are the favoured candidates for the 22Ne anomaly observed in the Galactic cosmic ray sources. They may also have injected into the proto-solar nebula short-lived radionuclides as 26Al, 36Cl, 41Ca, 107Pd and 205Pb.
γ2 Velorum, photon loss and the velocity field
Authors: De Marco Orsola , Schmutz Werner , de Koter Alex
Published: July 2016

The interception of 0.01% of photons (termed photon loss) from the He II Lyα line by Fe VI and Ca V line-opacity can alter substantially the ionization structure of the wind. This is shown to increase the stellar luminosity and hence the wind driving efficiency. Our classical models for WR11 (the WR component in the γ2 Vel binary) underestimate the stellar luminosity as compared to the luminosity derived from the mass-luminosity relation. Here we present a model for WR11 where photon-loss is included. This model succeeds in that it has a higher luminosity for the same spectral appearance and V brightness. Line-blanketing has not yet been added, so that the force-factors and the velocity-law cannot yet be calculated. However, a hydro-dynamical velocity-law derived from a photon-loss model of a WN5 star improves considerably the fit to the narrow He II λ4686 emission line over the use of a β-law.
The Baldwin-effect in Wolf-Rayet stars
Authors: van Gent Jeroen I.
Published: July 2016

Wolf-Rayet model stellar atmospheres are used to show the relation between He II line equivalent widths and continuum luminosity. It is shown that the Baldwin-effect is present in the models. A comparison made to observational data and model calculations by others stimulates further research into the physics of the effect.
Spectral analyses of WC stars in the LMC
Authors: Gräfener Götz , Hamann Wolf-Rainer , Koesterke Lars
Published: July 2016

Spectra of seven WC stars in the LMC are taken with the HST-FOS. They are analyzed by means of non-LTE models for spherically expanding atmospheres with complex model atoms of helium, carbon and oxygen taken into account. We find stellar luminosities in the range from 1051–56 L⊙. The stellar temperature T*, defined as the effective temperature related to the stellar core radius, is of the order of 100 kK. The atmospheric compositions show carbon mass fractions of about 0.4 and oxygen mass fractions in the range 0.1–0.5.
Inhomogeneities in Wolf-Rayet atmospheres
Authors: Koesterke Lars , Hamann Wolf-Rainer , Gräfener Götz
Published: July 2016

By progress in both computer-speed and the development of efficient solution algorithms (Accelerated Lambda Iteration, ALI) nowadays detailed models for Wolf-Rayet atmospheres can be calculated on a desktop computer. In recent years much work was focused on the correct treatment of all relevant opacities, with the success that now hundreds of atomic levels and thousands of spectral lines of light elements (e.g., He, C, N, O) and millions of Fe lines can be accounted for in non-LTE. With respect to the opacities, these new models are complete but they are all based on the standard assumptions for WR atmospheres, namely spherically-symmetric expansion and stationarity and homogeneity of the outflow (cf. Hamann et al. these Proceedings).
Inhomogeneous winds: the nature of emission-line profile variations in Wolf-Rayet spectra
Authors: Lépine Sébastien , Moffat Anthony F.J.
Published: July 2016

We present the results of simulations which show that stochastic line-profile variations (LPVS) of Wolf-Rayet emission lines can be reproduced with an inhomogeneous wind model, in which line-emission arises from a large number of discrete wind emission elements (DWEES). A comparison between simulations and LPVS from 9 WR stars provides useful information about the nature of the inhomogeneous and dynamical structure of the wind. Although the detailed spatial/fractal structure of the inhomogeneous wind is poorly constrained by analysis of LPVS, simulations suggest the wind to be highly fragmented, being composed of at least 104 DWEES in the line-emission region. Analysis of lpv patterns reaveal DWEES to be associated with large fluctuations in the velocity field. These fluctuations are locally anisotropic; the velocity dispersions of DWEES. are systematically larger in the radial direction (≈vr ≍ 200 km s−1) than in the transverse direction (σvθ ≈ 50 kms−1). lpv patterns also yield estimates of the wind acceleration, which can be used to test hypotheses about the wind velocity-law.
Is WR 103 (WC9) as violent as the WN8 stars?
Authors: Veen Pieter M. , van Genderen Arnout M. , van der Hucht Karel A. , Sterken Chris
Published: July 2016

We collected photometric data of WR 103 (HD 164270, WC9), both in the Walraven system and in the Strömgren system. Figure 1 presents one intense monitoring run, performed in 1990 by R. van Ojik. We suggest to describe the light-curve as a saw-tooth with a time-scale of roughly 0.5 day. Alhough we confirm a cyclic light-variation of the object with an amplitude of ∼ 0.05 mag, our data do not support the period of P = 0.88 d found by Isserstedt & Moffat (1981) (see also Moffat et al. 1986; Balona et al. 1989).
Long-term variation in the short-period binary system WR46 (WN3P+?)
Authors: Veen Pieter M. , van Genderen Arnout M. , Jones Albert F.
Published: July 2016

We studied the short-period (P ≈ 6–8 hr) binary system WR46 using simultaneous photometry and spectroscopy. We show that the long-term photometric variation is accompanied by changes in the equivalent width of the He II Λ5411 emission line and by an apparent period decrease on the rising branch. Furthermore, the brightening of the object is repeating.
The effect of micro-turbulence in O-type star analyses
Authors: Villamariz M.R. (Charo) , Herrero Artemio
Published: July 2016

We study here the influence of micro-turbulence in the synthesis of H and He lines, in order to quantify its effect on the determination of stellar parameters of O-type stars, in particular on the stellar He abundance. We find that only He I lines and He II λ 4686 are considerably affected, the effect being more relevant for models corresponding to supergiant stars. We also find that neglecting micro-turbulence in the analyses of O-type stars introduces deviations in the derived parameters that are within our standard error box. The He content is not or slightly reduced, thus micro-turbulence cannot be responsible for the He-discrepancy to all its extent.
Observations of colliding-wind effects at long wavelengths: IR to radio
Authors: Williams Peredur M.
Published: July 2016

The supersonic winds of the most luminous stars carry kinetic energy as well as mass. Where such stars are members of binary systems, some of this energy is released in strong shocks which form on both sides of the wind-collision boundary. Originally, the consequent heating of the gas in such systems was predicted to make the stars strong X-ray sources. However, the most conspicuous colliding-wind effects have been observed at longer wavelengths: synchrotron radiation from the shock-accelerated electrons and, most unexpectedly, infrared emission from dust condensing in the shock-compressed gas. Recent developments in observational techniques, especially increased spatial resolution, have led to delineation of these effects, and extensive observing campaigns have given a better idea of their incidence.
Colliding winds in Wolf-Rayet binaries: further developments within a complicated story
Authors: Walder Rolf , Folini Doris , Motamen Simin M.
Published: July 2016

We present large scale 3D simulations of colliding winds in the WR binary γ2 Velorum (WR 11). The O-star wind is confined by cold, high density shells and forms a spirally shaped region within the WR-wind. As a consequence of the elliptic orbit, the opening angle and the curvature of the spiral as well as the ratio of the volumes occupied by the WR- and the O-wind are functions of the orbital phase. Our model qualitatively reproduces the observed X-ray light-curve. The impact of magnetic fields and heat conduction on the physics of colliding winds is briefly discussed and some remarks on the important question of stability are made.
A high resolution H I study of the ISM local to WR 132 and WR 140
Authors: Arnal E. Marcelo
Published: July 2016

The neutral matter distribution from the interstellar medium located in the vicinity of the galactic WR stars WR 132 and WR 140 has been examined by means of the H I 21-cm line observations obtained with high angular resolution observations. The most interesting discoveries are the presence of huge ovoidal H I minimum spanning the velocity range +13 to +21kms−1 (WR132) and −18 to −7kms−1 (WR 140). These minima were created, very likely, by the joint action of the progenitor of both WR stars and the WR star itself. Inside each cavity, two minima are clearly discernible. The WR star is offset with respect to either the geometrical centre of the main H I void or the inner H I minima. The dual H I minimum geometry observed inside the main H I cavity, a feature also seen in the H I distribution of the ISM located close to other galactic WR stars, may be a consequence of the interaction process itself.
SN 1997ab and its progenitor's wind
Authors: Cid Fernandes Roberto , Salamanca Isabel , Tenorio-Tagle Guillermo , Terlevich Roberto J. , Telles Eduardo , Munõz-Tuñón Casiana
Published: July 2016

SN1997ab belongs to a class of luminous type II SNe which are thought to be powered by the interaction of the shock wave with a dense circumstellar medium. We report the discovery of narrow P-Cygni profiles atop broad Balmer emission lines, an unambiguous signature of a dense and slow circumstellar wind due to mass loss in the final stages of the progenitor's life.
Infrared spectroscopic variability of Cygnus X-3
Authors: Hanson Margaret M. , Fender Rob P. , Pooley G.G.
Published: July 2016

We present four epochs of high-resolution IR spectroscopy of the peculiar X-ray binary Cygnus X-3. The observations cover quiescent, small flaring and outburst states of the system as defined by radio and X-ray monitoring. The underlying IR spectrum of the source, as observed during radio and X-ray quiescence and small flaring states is one of broad, weak He II and N V emission. Spectral variability in this state is dominated by modulation at the 4.8 hr orbital period of the system. H-band spectra confirm the significant hydrogen depletion of the mass donor. In outburst, the infrared spectrum is dramatically different, with the appearance of very strong twin-peaked He I emission displaying both day-to-day variability and V (iolet) / R(ed) variations with orbital phase. We argue that the most likely explanation appears to be an enhanced stellar wind from the companion. Thus the X-ray and radio outbursts in this system are likely to originate in mass-transfer, and not disc instabilities. We suggest that the wind in Cyg X-3 is significantly flattened in the plane of the binary orbit. This may explain the observed twin-peaked He I features as well as reconcile the large infrared luminosity with the large optical depth to X-rays if Cyg X-3 is embedded in a spherically symmetric wind.
Modeling spectra of WR+O colliding wind systems
Authors: Hill Grant M. , Moffat Anthony F.J. , St-Louis Nicole , Bartzakos Peter
Published: July 2016

It is crucial to better understand the winds from massive stars. Not only does their mass loss affect their own evolution but it contributes an amount of energy and momentum to the ISM capable of affecting the chemical and dynamical evolution of their environments. Hot star binaries offer an opportunity to learn more. Colliding winds in such systems might be expected to lead to a bow shock which wraps around the star with the weaker wind. As material flows along the shock, it may give rise to extra line emission. Variations in these emission features may allow the characteristics of the shock region to be deduced thus providing a wealth of information about the winds.
Ejected nebulae as probe of Wolf-Rayet Lyman-continua
Authors: Pasquali Anna , Crowther Paul A. , Schmutz Werner , Hillier D. John
Published: July 2016

We present the first results from our analysis of WR model atmospheres in the UV domain. Specifically, we test the model atmospheres derived for WR 124 and WR 18 from the Hillier & Miller (1998) and Schmutz (1997) codes through photo-ionization modelling of the associated nebula or H II region. Both codes assume non-LTE and line-blanketing, while photon-loss is implemented only in Schmutz (1997) code. The comparison of the predicted nebular properties with observations indicates that: (i) line-blanketing is essential in reconciling the stellar and nebular properties of WR stars; and (ii) in the case of WR 18 the inclusion of photon-loss produces a slightly more ionized nebula than observed. However, the effect of different model properties such as mass-loss rate has still to be investigated.
3D hydrodynamic simulations of colliding winds in V444 Cygni
Authors: Pittard Julian M. , Stevens Ian R.
Published: July 2016

We report on recent developments in simulating colliding wind X-ray emission, and present a 3D model of the WR binary V444 Cyg (WN5+O6) which self-consistently includes radiative driving.
The stellar content of NGC 3603
Authors: Drissen Laurent
Published: July 2016

At the heart of the galactic giant H II region NGC 3603, low-mass (1–4 M⊙) stars slowly contract toward the main sequence, while peacefully cohabiting with the three most luminous, hydrogen-rich Wolf-Rayet stars in the Galaxy, a dozen hot O3–4 stars and their more modest but numerous O and B companions. This is the story of a very young and dense starburst cluster …
Initial conditions in the evolution of OB and Wolf-Rayet stars in N 105 of the LMC
Authors: Ambrocio-Cruz Patricia , Laval A. , Marcelin M. , Amram P. , Comerón F.
Published: July 2016

The detailed radial velocity field of the H II region N105, in the LMC, has been obtained for the Hα and [O III] 5007 lines with a spatial sampling of 9″ and a spectral sampling of 16 and 7kms−1. The peculiar velocity field and morphology indicate that N105 contains four bubble shaped nebulae and two bright distinct quasi-spherical H II regions, more or less coeval, embedded inside another large shell nebula. They are essentially formed by the action of stellar winds of a few exciting stars, born deep inside their parental cloud. This result is deduced from the energy input inside the ionized gas by the stellar winds of early type stars and from dynamical simulations combining the effects of stellar winds with those of high density gradients inside the neutral gas. The size and morphology of the H II region are conditioned by the depth inside the natal cloud; the observed dynamical time-scale of the H II region starts at the moment of blow-out of the molecular cloud.
Photo-ionization models of NGC 2363 and their implications
Authors: Luridiana Valentina , Peimbert Manuel , Leitherer Claus
Published: July 2016

We compute photo-ionization models for the giant extragalactic H II region NGC 2363, and compare them with optical observational data. We focus on the following observational constraints: F(Hβ), Ne, EW(Hβ), and the ratios of I(λ 5007), I(λ 4363), I(λ 3727), I(λ 6300), I(λ 6720) and I(λ 4686) relative to I(Hβ). We discuss the variations of the emission spectra obtained with different input parameters. We show that low metallicity models (Z = 0.10Z⊙) cannot reproduce the observed features of the spectrum, and that the disagreement can be satisfactorily overcome by allowing for spatial temperature fluctuations in the nebula. Accordingly, we show that the metallicity of NGC 2363 has most probably been underestimated, and that a value of Z ≃ 0.25 Z⊙ is in better agreement with the observational data than the usually adopted value Z≃0.10Z⊙. We also derive values for the slope and the high mass end of the IMF, as well as the age of the stellar cluster.
Study of the Wolf-Rayet population in NGC 604 using bi-dimensional spectroscopy
Authors: Maíz-Apellániz Jesús , Miguel Mas-Hesse José , Pérez Enrique
Published: July 2016

We study the properties of the young population of NGC 604 and find evidences for 1–2 Myr differences between different regions. Four of the eleven WR stars in NGC 604 are found to have wide Hα emission lines. None of the WR stars is located within knots of high density, high excitation gas, as opposed to some of the O-type stars.
The M31-WC6 star MLA 1159 and its ionized nebula BA1-642
Authors: Tovmassian Gaghik H. , Greiner Jochen , Komossa Stefanie , Rosado Margarita , Arrieta Anabel
Published: July 2016

Aimed at identifying supersoft X-ray sources in ionization nebulae, we have searched for extended optical emission within the X-ray error boxes of the 15 supersoft sources in M31 (Greiner et al. 1996). One optical nebula was found, of which we obtained spectroscopy, narrow-band imaging and FP-interferometry, to determine its relation to the positionally correlated supersoft X-ray source RX J0045.5+4206. M31 has been surveyed several times with different goals. Baade & Arp (1964) compiled a list of 688 emission nebula in M 31. One of these nebulae, BA1-642 (PAV 78915 in the catalog of Pellet et al. 1978), was found by cross-correlation with supersoft X-ray sources. The central object MLA 1159 of this nebula has been classified WR (Meyssonier et al. 1993). Here we confirm this new WR star and discuss the star as well the ring-like nebula around it. We did direct imaging of RX J0045.4+4206 with narrow-band nebular filters, spectroscopy of the central star and surrounding nebulae, and we observed the nebula with the FP-interferometer PUMA. All observations were carried out at OAN SPM, México.
The star formation histories of two Wolf-Rayet galaxies: NGC 1741 and He2-10. Two butterflies in a collection
Authors: Johnson Kelsey E.
Published: July 2016

In an effort to better understand how the properties of star formation in starburst galaxies depend on various environmental parameters, I present a comparison between two well-known WR galaxies: the interacting galaxy system NGC 1741 in the Hickson Compact Group 31, and the dwarf galaxy He2-10. The high spatial resolution of HST has allowed identification of a large number of starburst knots, or ‘super star clusters’ in these WR galaxies. Broad-band photometry and the latest stellar synthesis models are used to estimate the ages and masses of the super star clusters. The properties of the clusters are then used to compare and contrast the overall star-formation histories in the two WR galaxies.
The stellar content of the Wolf-Rayet galaxy NGC 5253 from ISO-SWS spectroscopy
Authors: Crowther Paul A. , Beck Sara C. , Willis Allan J. , Conti Peter S. , Morris Patrick W. , Sutherland Ralph S.
Published: July 2016

Wolf-Rayet galaxies are a subset of blue emission-line galaxies, whose spectra show the signature of large numbers of WR stars, with ages in the range 1-10 x 106 yr. Mid infra-red observations are well suited to the study of their hot, massive stars since this spectral region contains many fine-structure nebular lines which depend very sensitively on stellar content. The observations of ISO have opened-up this window, which we are exploiting through a Guest Observer program with the Short Wavelength Spectrometer (sws), that includes NGC 5253, a nearby (4 Mpc) WR galaxy. NGC 5253 contains several young super-star clusters, no older than a few million years and has been the focus of many recent studies which have shown that the extinction is very high and patchy in the UV and optical. ISO observations of NGC 5253 are particularly important since the interstellar extinction at mid-IR wavelengths is low and because of its remarkably hot and young stellar population.
Systematic search for Wolf-Rayet stars in young starbursts
Authors: Kovo Orly , Contini Thierry
Published: July 2016

Preliminary results from a systematic search for WR stars in starburst galaxies are presented. We report new detections of WR spectral features (the ‘WR bump’ around ∼ 4700 Å) in eight objects.
An unusual bubble in the tidal arm of NGC 7318B in Stephan's Quintet
Authors: Ohyama Y. , Nishiura S. , Murayama T. , Taniguchi Y.
Published: July 2016

We optically find an unusual emission-line bubble near the tip of the southeastern arm of NGC 7318B. A large number (∼ 106) of supernova remnants would be the most plausible agents.
Red supergiants in star-forming galaxies
Authors: Origlia Livia , Oliva Ernesto
Published: July 2016

We present some results on the burst properties in star forming galaxies, using near infrared stellar features typical of red supergiants and Brackett nebular lines which trace the presence of luminous H II regions.
Ultraviolet spectral libraries of massive stars at low metallicity
Authors: Robert Carmelle
Published: July 2016

Three new ultraviolet spectral libraries of massive, hot stars using high and medium resolution spectra of objects located in the solar neighbourhood and the Magellanic Clouds are presented. Massive stars display unique wind signatures which are relatively easy to study in the ultraviolet. These libraries are crucial tools when investigating the massive stellar population of distant star-forming galaxies.
The influence of close binary evolution on the age determination of starburst regions
Authors: Van Bever Joris , Belkus H. , Vanbeveren Dany , van Rensbergen Walter
Published: July 2016

Using a population number synthesis code and detailed massive star evolutionary calculations, we investigate the effect of close binary evolution on Hα and Hβ emission-line strength variation in starburst regions. The Hβ line strength especially, is considered as a good age indicator. We demonstrate that the formation of rejuvenated accretion stars (Blue Stragglers) through RLOF lengthens the life-time of the Hβ flux and makes the age determination of a starburst regions ambiguous. We separately calculate the effect of Wolf-Rayet stars and of X-ray binaries on Hα and Hβ and conclude that both are of minor importance.
Superwinds and the nature of starburst galaxies
Authors: Lehnert Matthew D.
Published: July 2016

I discuss the observational evidence that starburst galaxies are able to drive galactic-scale outflows ('superwinds') and then argue generally that superwinds must have had an important role in galaxy evolution. To explore the role of feedback from massive stars, I review results suggesting that starbursts seem to obey a limiting IR surface brightness of about 1011 L⊙ kpc−2, corresponding to a maximum star-formation rate of about 45M⊙ yr−1kpc−2 for a ‘normal’ initial mass function. I conclude by discussing the role of winds in determining this upper-limit and discuss recent results implying that winds might actually escape the galactic potentials in which they reside.
Photo-ionization models with Wolf-Rayet central stars
Authors: Stasińska Grażyna
Published: July 2016

We summarize the goals of photo-ionization modelling of nebulae ionized by Wolf-Rayet stars and discuss the methodology. We present some examples in different astrophysical contexts: ring nebulae around massive WR stars, planetary nebulae with [WR]-type central stars, and giant H II regions with WR stars. We discuss in more detail a work in progress (Stasińska & Schaerer 1999) on the galaxy I Zw 18.
Chemical enrichment from massive stars in starbursts
Authors: Kobulnicky Henry A.
Published: July 2016

The warm ionized gas in low-mass, metal-poor star forming galaxies is chemically homogeneous despite the prevalence of large H II regions which contain hundreds of evolved massive stars, supernovae, and Wolf-Rayet stars with chemically-enriched winds. Galaxies with large WR star content are chemically indistinguishable from other vigorously star-forming galaxies. Furthermore, no significant localized chemical fluctuations are present in the vicinity of young star clusters, despite large expected chemical yields of massive stars. An ad hoc fine-tuning of the release, dispersal and mixing of the massive star ejecta could give rise to the observed homogeneity, but a more probable explanation is that fresh ejecta from massive stars reside in a hard-to-observe hot or cold phase. In any case, the observed chemical homogeneity indicates that heavy elements which have already mixed with the warm interstellar medium (thus accessible to optical spectroscopy) are homogeneously dispersed over scales exceeding 1 kpc. Mixing of fresh ejecta with the surrounding warm ISM apparently requires longer than the lifetimes of typical H II regions (> 107 yr). The lack of observed localized chemical enrichments is consistent with a scenario whereby freshly-synthesized metals from massive stars are expelled into the halos of galaxies in a hot, 106 K phase by supernova-driven winds before they cool and ‘rain’ back down upon the galaxy, creating gradual enrichments on spatial scales >1 kpc.
The energetic role of massive stars in the AGN phenomenon
Authors: Heckman Timothy M.
Published: July 2016

I review the evidence for a possible connection between AGN and starbursts and assess the energetic role of massive stars in the AGN phenomenon. My particular focus is on UV spectroscopy, since this is the energetically dominant spectral regime for the hot high-mass stars that power starbursts, and contains a wealth of spectral features for diagnosing the presence of such stars. I also review the non-stellar sources of UV line and continuum emission in AGN, including scattered or reprocessed light from the ‘central engine’. Spectroscopy directly shows that hot stars provide most of the UV light in about half of the brightest type 2 Seyfert nuclei and UV-bright LINERS. The population of hot stars in these AGN is typically heavily extinct and reddened by dust with A(1600Å) ≃ 2–4 mag. The implied intrinsic UV luminosities of the starburst range from 108 to 109 L⊙ in the LINERS to 1010 to 1011 L⊙ in the type 2 Seyferts. Massive stars play an energetically significant role in many AGN, but the causal or evolution connection between starbursts and AGN is unclear. I also consider the energetics of massive stars and accreting supermassive black holes from a global, cosmic perspective. Recent inventories in the local universe of the cumulative effect of nuclear burning (metal production) and of AGN-fueling (compact dark objects in galactic nuclei) imply that accretion onto supermassive black holes may have produced as much radiant energy as massive stars over the history of the universe.
The stellar content of NGC 2363 and its surroundings
Authors: Drissen Laurent , Roy Jean-René , Robert Carmelle , Devost Daniel
Published: July 2016

A detailed study of the stellar content of the giant H II region NGC 2363 and its surroundings in the Magellanic galaxy NGC 2366 is undertaken to understand the starburst phenomenon.
The superwind Wolf-Rayet galaxy Markarian 1259
Authors: Ohyama Youichi , Taniguchi Y. , Terlevich Robert J.
Published: July 2016

We present results of our optical spectroscopic observations and 12CO (J = 1 - 0) mapping of the Wolf-Rayet starburst galaxy Markarian 1259 with a superwind activity. We find that both the ionized gas and the molecular gas are associated with the superwind.
Chimneys in the starburst galaxy M 82
Authors: Redman Matt P. , Wills K. A. , Muxlow T.W.B. , Pedlar A.
Published: July 2016

A new radio image of the core of the starburst galaxy M82 is presented. A pair of probable galactic chimneys are evident. Such structures have been conjectured to result when a giant shell of ionized gas breaks out of the dense plane of a galaxy and ejects hot gas into the halo. In M 82, the starburst activity drives a galactic superwind and theoretical models of this process require a knowledge of the kinematics of the hot gas in the core of the galaxy. The results presented here imply that the ejection of material into the base of the superwind does not occur smoothly over the starburst region; instead, very localised venting of the hot gas appears to be taking place.
The distance and reddening to IC 10 from preliminary JHK photometry
Authors: Georgiev Leonid N. , Kurtev Radostin , Rosado Margarita , Borissova Jordanka H.
Published: July 2016

By comparing the brightest red supergiants in IC 10 and IC 1613, we derive for IC 10 that EH-K = 0.24 ± 0.09mag (i.e., EB-v = 1.26 ± 0.19 mag) and a true distance modulus 24.0 ± 0.13 mag.
Special session on HD 5980
Authors: Moffat Anthony F.J.
Published: July 2016

On Monday before the regular meeting began, a group of 31 participants met for 5 hours to discuss HD 5980, a massive binary in which one of its components erupted in 1994 as a luminous blue variable (LBV). This made HD 5980 the most luminous star in all the SMC for about six months. The highlights of this session are presented here.
N-body Simulations of Planet Formation
Authors: Ida Shigeru , Kokubo Eiichiro , Kominami Junko
Published: July 2016

Accretion from many small planetesimals to planets is reviewed. Solid protoplanets accrete through runaway and oligarchic growth until they become isolated. The isolation mass of protoplanets in terrestrial planet region is about 0.1-0.2 Earth mass, which suggests giant impacts among the protoplanets in the final stage of terrestrial planet formation. On the other hand, the isolation mass in Jupiter's and Saturn's orbits is about a few to 5 Earth masses, which may be massive enough to trigger gas accretion onto the cores. The isolation mass in Uranus and Neptune's orbits is as large as their present cores. Extending the above arguments to extrasolar planetary systems that are formed from disks with various initial masses, we also discuss diversity of extrasolar planetary systems.
Modeling of the Saturnian Ring System
Authors: Griv Evgeny , Liverts Edward , Gedalin Michael , Yuan Chi
Published: July 2016

A self-consistent system of the Boltzmann equation and the Poisson equation is used to study the dynamical evolution of Saturn's main A, B, and C rings. The theory, as applied to the Saturnian ring system, predicts for several features, such as numerous irregular density wakes, with size and spacing between them of the order 4πρ ≈ 2πh, where ρ is the mean epicycle radius of the particle and h is the typical thickness of the system under study. In Saturn's rings, ρ ≲ 10 m. Computer N-body experiments are desribed which test the validities of the theory. Use of the 112-processor SGI Origin 2000 supercomputer is enabled us to make long runs using a large number of particles in the direct simulation code and thus simulate phenomena not previously studied numerically. We predict that forthcoming in 2004 Cassini spacecraft high-resolution images will reveal this recurrent fine-scale ∼ 100 m or so structure in low and moderately high optical depth regions of the rings.
A New Formalism for Studying Three-Body Interactions
Authors: Mardling Rosemary A.
Published: July 2016

A new formalism for studying three-body interactions is discussed. It introduces the concept of forced modes of oscillation of a binary, and relies on the chaos theory concept of resonance overlap. The treatment provides a powerful tool for studying stability and scattering in hierarchical systems, and is not restricted by mass ratios, eccentricities or orientations.
The formation of intermediate mass black holes
Authors: Portegies Zwart Simon F.
Published: July 2016

We study the growth rate of stars in dense star clusters by stellar collisions. Our analytic calculations are in good agreement with direct N-body simulations with up to 65536 stars performed on the GRAPE family of computers. We find that star clusters with a half mass relaxation time ≲ 20 Myr are dominated by stellar collisions. The first collision occurs at the moment of core collapse. The collision dominated phase last until the cluster dissolves in the tidal field of the Galaxy or mass loss by stellar evolution arrests core collapse. The majority of collisions occur with the same star resulting in the uncontrolled growth of a super massive object. This object can grow up to ∼ 0.08% of the mass of the entire star cluster. This mass ratio is comparable to the ratio of the mass of Galactic bulges to their central black hole. Star clusters which are older than about 4 Myr and with a half mass relaxation time ≲ 80 Myr are expected to contain the remnant of a phase of uncontrolled growth in their cores.
Regularization tools for binary interactions
Authors: Aarseth Sverre J.
Published: July 2016

We first discuss two-body and chain regularization methods for direct N-body simulations on HARP-2 and GRAPE-6. The former is used for accurate integration of perturbed binaries and hierarchies, whereas the latter deals with strong interactions involving binaries. Combined with a powerful stability criterion for hierarchical systems, this versatile treatment provides an efficient way of studying all dynamical processes in globular clusters containing a realistic population of primordial binaries. These algorithms are also ideal for modelling a variety of astrophysical effects, such as averaging over Kozai cycles, tidal circularization, spin-orbit coupling and stellar collisions, where well-defined elements are used to describe near-singular solutions. We also describe a new time-transformed leapfrog scheme which has been developed to deal with black-hole binaries in galactic centres. This formulation is valid for large mass ratios and dominant two-body motions in a compact subsystem can be treated accurately in the post-Newtonian approximation. This method has been combined with the existing regularization algorithms into a new simulation codeNBODY7. Some preliminary results of a test problem illustrating possible applications are presented.
Simulation Software: Then, Now and Virtual Observatory
Authors: Teuben Peter
Published: July 2016

Like hardware, evolution of software has had a major impact on the field of particle simulations. This paper illustrates how simulation software has evolved, and where it can go. In addition, with the various ongoing Virtual Observatory efforts, producers of data should think more about sharing their data! Some examples are given of what we can do with our data and how to share it with our colleagues and observers. In the Appendix we summarize the findings of an informal data and software usage survey that we took during this conference.
Evolution of star clusters moving on elliptic orbits
Authors: Baumgardt Holger
Published: July 2016

We describe results of N-body simulations of star clusters moving on elliptic orbits. Our aim is to follow the evolution of these clusters and study how their dissolution times depend on particle number and eccentricity.

We find that the scaling of the lifetimes is nearly independent of the eccentricity, despite the fact that the amount of tidal shocking changes with eccentricity. In addition, no leveling off of the lifetimes at the high-N end, which would indicate the influence of tidal shocking, is seen.
N-body Simulations of Planetary Rings
Authors: Daisaka Hiroshi
Published: July 2016

We present the formation and evolution of a structure in particles obtained from a local N-body simulation of a dense planetary ring like Saturn's ring. Our simulations show in a particle system the spontaneous formation of a spatial structure like wakes, clumps, and a structure which could be induced by the viscous overstability. Such a formation depends on parameters characterizing a ring system: the wake is likely to form in Saturn's ring and the existence of the wake is consistent with observations. The viscous overstability would be a good candidate for the explanation of subring structures in the ring.
The evolution of triaxial molecular cores
Authors: Goodwin Simon P. , Whitworth Anthony P. , Ward-Thompson Derek
Published: July 2016

We are using SPH to model the evolution of triaxial molecular cores to investigate the fragmentation of these cores and the possible production of multiple systems. Molecular cores appear to be triaxial in shape and this may have a significant effect on their evolution as they collapse to form filament-like structures which can then fragment into multiple 'protostars'.
Structural Evolution of Substructure
Authors: Hayashi Eric , Navarro Julio F.
Published: July 2016

The evolution of substructure in dark matter halos is investigated in a series of simulations of N = 105 satellite halos on elliptical orbits in the gravitational potential of a much larger host system. The bound mass of the satellite decreases with each pericentric passage and most of the mass is lost from the outer region of the satellite halo. We parameterize the change in its density profile by modifying the initial profile by a factor proportional to (1 + r-3), which results in reasonable fits to the mass profiles of tidally stripped subhalos.
Monopole Evolution in the Early Universe
Authors: Nagasawa Michiyasu
Published: July 2016

The formation and evolution of monopoles produced at TeV energy scales are considered. They can contribute to the generation of baryon number and may solve the cosmological problem. The dynamics of electroweak defects is completely different from that of conventional grand unification scale defects so that their number density should not be described by the scaling model.
SPH Simulations of Galaxy Cluster Mergers
Authors: Takizawa Motokazu
Published: July 2016

We present our results of SPH simulations of cluster mergers. We investigate the temperature evolution explicitly considering the relaxation process between ions and electrons. The electron temperature distributions are significantly different than those of ions in the later stages of mergers. We also investigate evolution of non-thermal emission from relativistic electrons accelerated around shock fronts. Hard X-ray is luminous only while signatures of merging events are clearly seen in the thermal intracluster medium. On the other hand, extreme ultraviolet emission is still luminous after the system has relaxed.
N-body Code with Adaptive Mesh Refinement
Authors: Yahagi Hideki , Yoshii Yuzuru
Published: July 2016

We have developed a simulation code with the techniques which enhance both spatial and time resolution of the PM method for which the spatial resolution is restricted by the spacing of the structured mesh. The adaptive mesh refinement (AMR) technique subdivides the cells which satisfy the refinement criterion recursively. On the other hand, the technique of hierarchical time steps (HTS) changes the time step, from particle to particle, depending on the size of the cell in which particles reside. Our N-body code with these AMR and HTS is fully vectorized including the operations of the mass assignment.
Refining the UKST Hα Survey's PN Database Using MSX
Authors: Cohen Martin , Parker Quentin A.
Published: July 2016

We are combining images in the mid-infrared (from MSX, the US Midcourse Space Experiment) with those from the high resolution UKST/AAO Hα survey of the Galactic Plane to investigate the relationship between the mid-infrared (MIR) and optical emission line properties of candidate Planetary Nebulae (PN) discovered by the Hα survey. Preliminary results indicate that only 10–20% of likely bona fide PN have a counterpart detected in the MIR. By sharp contrast one can readily recognize pre-main- sequence objects and HII regions emitting Hα and largely embedded in dust by the simultaneous presence of 8.3 and 21.3-μm emission suggestive of dust spanning a variety of temperatures. The sharpest criteria for recognizing true PN appear to be optical morphology and spectra (particularly the presence of [OIII]), and, where detected, MIR characteristics.
An Interactive Visualization of the Catalogue of Galactic Planetary Nebulae
Authors: Köppen J. , Acker A.
Published: July 2016

At http://astro.u-strasbg.fr/~koppen/png/png.html you'll find the first release of an interactive version of the Strasbourg-ESO Catalogue of Galactic Planetary Nebulae by Acker et al. (1992). The observational data of 1185 planetary nebulae can be inspected in detail numerically. Any two properties can be plotted against each other, with interactive zooming, graphical marking of groups of nebulae with certain properties, and identification and display of the data of any individually selected object. Maps of the sky – as well as of the space of any two parameters – can be displayed for any third parameter. Nebulae may be selected according to their names or observed parameters. This interactive catalogue is an application of the JAVA applet CatPlot which also permits the user to read in one's own catalogue file and also display images and x–y plots (a detailed description may be found in the explanatory pages at http://astro.u-strasbg.fr/~koppen/catplot/CatPlotHelp.html).
DENIS Survey Data Probing Different Types of PNe
Authors: Schmeja Stefan , Kimeswenger Stefan
Published: July 2016

We present near-infrared photometry of a large sample of PNe and show that the IJK colours are a good tool to distinguish different classes of PNe, like nebulae around symbiotic Miras or IR-[WC] PNe from genuine PNe.
A Comprehensive Study of Planetary Nebulae in the Galactic Bulge
Authors: Zijlstra Albert A. , Walsh J. R. , Gesicki Krzysztof
Published: July 2016

We describe an on-going observational study to characterize the PN population of the Galactic Bulge.
Diffraction-Limited Speckle Interferometry and Modeling of the Circumstellar Envelope of R CrB at Maximum and Minimum Light
Authors: Ohnaka K. , Blöcker T. , Hofmann K.-H. , Ikhsanov N. R. , Weigelt G. , Balega Y. , Shenavrin V. I. , Yudin B. F. , Efimov Y. S.
Published: July 2016

We present the first speckle interferometric observations of R CrB, the prototype of a class of peculiar stars which undergo irregular declines in their visible light curves. The observations were carried out with the 6 m telescope at the Special Astrophysical Observatory near maximum light (V = 7, 1996 Oct. 1) and at minimum light (V = 10.61, 1999 Sep. 28). A spatial resolution of 75 mas was achieved in the K-band. The dust shell around R CrB is partially resolved, and the visibility is approximately 0.8 at a spatial frequency of 10 cycles/arcsec. The two-dimensional power spectra obtained at both epochs do not show any significant deviation from circular symmetry. The visibility function and spectral energy distribution obtained near maximum light can be simultaneously fitted with a model consisting of the central star and an optically thin dust shell with density proportional to r−2 and amorphous carbon as its constituent. The inner boundary of the shell is found to be 82 R* (19 mas) with a temperature of 920 K near maximum light. However, this simple model fails to simultaneously reproduce the visibility and spectral energy distribution obtained at minimum light. We show that this discrepancy can be attributed to thermal emission from a newly formed optically thick dust cloud. Simultaneous fits of the observed SED and visibility with models including a thermally emitting dust cloud suggest the presence of a newly formed dust cloud as hot as 1200 K with a radius of 4 – 5R*, in addition to an optically thin dust shell whose inner boundary is ~ 170 R* with a temperature of ~ 690 K. Alternatively the discrepancy can be attributed to an unusual extinction curve of dust grains in the obscuring cloud which was present in front of the star at minimum light. The details of the observations and modeling are described in Ohnaka et al. (2001, A&A 380, 212).
The s-process in Rotating AGB Stars
Authors: Herwig Falk , Langer Norbert , Lugaro Maria
Published: July 2016

We discuss the occurrence of the s-process during the radiative interpulse phase of rotating AGB stars. Due to differential rotation, protons are mixed into 12C-rich layers after thermal pulses, in the course of the so called third dredge up episode. We follow the time evolution of key isotope abundances in the relevant layers with a post-processing code which includes time dependant mixing and nucleosynthesis. In rotating AGB models, the mixing persists during the entire interpulse phase due to the steep gradient of angular velocity at the envelope-core interface. As the layers containing protons and 12C, which are formed this way, become hotter, a 13C-pocket is formed in a natural way. However, in this situation also 14N is formed and spread over the entire 13C-pocket. We include the neutron consuming 14N(n,p) reaction in our network and determine to what extent it reduces the production of trans-iron elements. We propose that rotation may be responsible for the spread of efficiencies of the 13C neutron source as required by observations.
The Effects of Transition Time on the Populations of Post-AGB Stars, and on the Nebular Evolution
Authors: Villaver Eva , Stanghellini Letizia , Manchado Arturo , García-Segura Guillermo , Renzini Alvio
Published: July 2016

We show how the different assumptions on the transition time (the time lag between the superwind quenching at the AGB and the illumination of the Planetary Nebula [PN]) reflect into very different theoretical outcomes, both in the characteristics of the stellar remnants, and in the evolution of the nebular shells.

We use a Monte Carlo simulation of post-AGB stars with a set of assumptions on the transition time, to show the effect on the resulting location of the stars on the HR diagram, and on the derived core mass distributions.

We have also performed numerical simulations of the PN formation process, and investigated the effects of the transition time on the resulting PN structure. We found that the transition time determines not only the size of the PN shell, but also its dynamical evolution.

We show the important implications that the transition time has on the observable parameters during the PN stage.