bluuebunny/crossref_metadata_2025_split huggingface dataset:
N132D: a chemical and dynamic analysis
Authors: Sutherland Ralph S. , Dopita M. A. 
Published: July 2016

We have obtained 2D spectrophotometry of the LMC supernova remnant N132D, achieving a higher spatial resolution than previous studies (Lasker 1978, 1980). A model based on a simple expanding ring of oxygen rich material is shown to be inadequate. We find incomplete arcs of shocked material with individual components of differing compositions. Oxygen rich material appears as rapidly moving small knots in parts of these arcs and in a larger diffuse cloud, all in the central 6-10 pc region of the remnant. We propose a model for this remnant involving the interaction of the supernova blastwave with an incomplete ring of normal composition material to produce reflected shockwaves in the inner regions of the remnant, exciting oxygen rich material.In the knots of more normal composition a wide range of shock conditions prevail. Apart from 'normal' fully ionized radiative shocks with velocities 100-200 km/s the very steep Balmer decrements in the filaments of some spectra are consistent with partially ionized, slower, shocks. Other spectra show very strong emission lines for the higher ionization species, OIII and NeIII, which could be explained in terms of either strong shocks with long recombination timescales or as very young shocks that have not yet achieved steady flow.
OH/IR stars in the Large Magellanic Cloud: the observations
Authors: Wood P. R. , Bessell M. S. , Hughes S.M.G. , Hyland A. R. , Whiteoak J. B. , Gardner F. F. , Otrupcek R. E. 
Published: July 2016

In 1985 we began a search for OH/IR objects in the Magellanic Clouds. The first detection was reported by Wood, Bessell & Whiteoak (1986). Subsequent searches have yielded several of these objects and other highly-evolved stars obscured by thick circumstellar shells.The 1612-MHz OH observations were made using the Parkes 64-m radio telescope. Most of the observations utilized a dual-channel cryogenic receiver providing a system temperature of around 38 K on cold sky. The OH spectra were obtained with the Parkes digital correlator split into 512-channel segments. Bandwidths of 2 MHz provided a resolution of 7.8 kHz (equivalent to 1.5 km s−1 in radial velocity) after Hanning smoothing. The mode of observation has been described by Whiteoak and Gardner (1976). Typically, an integration period of 60 minutes was used; this yielded a detection limit (3a) of around 50 mJy for an OH feature. Detected emission was reobserved with a 1-MHz bandwidth. A search was also made for 1665-MHz OH emission.
Carbon stars in populations of different metallicity
Authors: Groenewegen M.A.T. 
Published: July 2016

Our current knowledge of carbon stars in the Local Group and beyond, is discussed. Although many carbon stars and late M-stars have been identified in external galaxies, a coherent understanding in terms of the chemical evolution- and star-formation-rate history of a galaxy is still largely lacking. Issues that need to be addressed are: 1) for some of the larger galaxies only a small fraction in area has been surveyed so far, 2) surveys have been conducted using different techniques, and may be incomplete in bolometric magnitude, 3) only for some galaxies is there information about the late M-star population, 4) not all galaxies in the Local Group have been surveyed, 5) only for a sub-set of stars are bolometric magnitudes available.From the existing observations one can derive the following: the formation of carbon stars is both a function of metallicity and star formation. In galaxies with a similar star-formation-rate history, there will be relatively more carbon stars formed in the system with the lower metallicity. On the other hand, the scarcity of AGB-type carbon stars in some systems with the lowest metallicity indicates that these galaxies have had a low, if any, star-formation-rate history over the last few Gyrs.
Recent and Future Studies of Circumstellar Matter – A Snapshot
Authors: Jura M. 
Published: July 2016

At this meeting, powerful new images and spectroscopy of AGB stars were presented. Theoretical models have advanced, and we are learning more from studies of the pre-solar grains isolated from meteorites.We suggest that several mass loss mechanisms may be operating in AGB stars: current images imply both spherical winds and highly flattened outflows. There are good arguments that in some cases, a companion may be critical in driving the final outflow. In the near future, a number of extremely powerful new instruments and techniques will be available that will lead to a much deeper understanding of these systems.
Young Stellar Populations in M31, M33, and NGC 6822
Authors: Hutchings J. B. , Cavanagh B. , Bianchi L. , Chandar R. , Scuderi S. 
Published: July 2016

We have been pursuing a program of hot star UV spectroscopy in local group galaxies over several years with HST. We have also obtained WFPC2 images in parallel and pointed exposures with several broad band filters.• The imaging data have been used to generate colour-magnitude plots of central fields, clusters and halo fields in M31, M33 and NGC 6822. We have compared these with high-mass model isochrones from recent models, to examine the stellar populations that are indicated. M33 contains a substantial young cluster population whose mass and age appear to be related. The western outer wisps of NGC 6822 contain a relatively young population of stars.• Most of the spectra have been reported and modelled in published papers: we note here the first comparison of stars in NGC 6822 with others from local group galaxies.• We have also discussed the interstellar extinction in M31 and find it is similar to the Galaxy after allowance for comparable amounts of halo extinction that resembles that of the Magellanic Clouds.
Visual and Near-Infrared Photometry of Nearby Dwarf Spheroidals
Authors: Kerschbaum F. , Nowotny W. , Hron J. , Schultheis M. 
Published: July 2016

This paper is based on photometry from two different observational approaches. Both are of an explorative character and act as feasibility studies. For the future we plan to use these methods to study Asymptotic Giant Branch (AGB) stars in nearby galaxies.First, we present results on broad-band photometry in BessellVandI, as well as narrow-band measurements in the Wing 778 nm and 812 nm filters of a galactic globular cluster using the new Austrian Oe-FOSC (Oesterreich Faint Object Spectrograph and Camera), a copy of the ESO Instrument EFOSC mounted on our 1.5 m-telescope.The second part of the contribution deals with the possibilities of using GunnI, JandKSmeasurements originating from the DENIS (DEep Near Infrared Survey of the Southern Sky) project on similar objects. A few southern dwarf spheroidals already observed within DENIS (covering now some 40% of the southern hemisphere) are selected.
Dynamics and variability of winds from single Wolf-Rayet stars
Authors: Owocki Stanley P. , Gayley Kenneth G. 
Published: July 2016

We review the dynamics of winds from single Wolf-Rayet stars, with emphasis on the following specific points:
(a)The classical “momentum problem” (to explain the large inferred ratio of wind to radiative momentum, η Mv∞/(L/c) ≫ 1) is in principle readily solved through multiple scattering of radiation by an opacity that is sufficiently “gray” in its spectral distribution. In this case, one simply obtains η ≃ τ, where τ is the wind optical depth;(b)Lines with a Poisson spectral distribution yield an “effectively gray” cumulative opacity, with multi-line scattering occuring when the velocity separation between thick lines Δv is less than the wind terminal speed v∞. In this case, one obtains η ≃ v∞/Δv;(c)However, realistic line lists are not gray, and leakage through gaps in the line spectral distribution tends to limit the effective scattering to η ≲ 1;(d)In WR winds, ionization stratification helps spread line-bunches and so fill in gaps, allowing for more effective global trapping of radiation, and thus η > 1;(e)However, photon thermalization can reduce the local effectiveness of line-driving near the stellar core, making it difficult for radiation alone to initiate the wind;(f)The relative complexity of WR wind initiation may be associated with the extensive turbulent structure inferred from observed variabililty in WR wind emission lines;(g)Overall, the understanding of WR winds is perhaps best viewed as an “opacity problem”, i.e., identifying the enhanced opacity that can adequately block the radiation flux throughout the wind, and thus drive a WR mass loss that is much greater than from OB stars of comparable luminosity.
New models of massive and Wolf-Rayet stars with mass loss and rotation
Authors: Maeder André 
Published: July 2016

We give results of models of massive stars which have a detailed physical treatment of rotation, including structural equations for shellular rotation, new treatments of shears in differentially rotating stars and of meridional circulation, together with mass loss rates depending on rotation. For a 20 M⊙ star, He- and N-enrichments at the stellar surface already occur during the MS phase for moderately low rotational velocities, thus most supergiants are enriched in helium and nitrogen. A long B- and A-supergiant phase results from rotational mixing, with some primary nitrogen formed at this stage. For the most massive stars, rotation makes the star to enter the WR stage during the MS phase thus avoiding the LBV and red supergiant stage.The WR life-times are considerably increased by rotation and the minimum mass for forming WR stars is lowered. Interestingly enough, the increase of the WN life-time is larger than for WC stars, so that rotation leads to a decrease of the WC/WN number ratio. Also, the fraction of transition WN/WC stars is much larger at higher rotation.Finally, on the basis of clusters in the SMC, in the LMC and towards the galactic interior and exterior, we show that for clusters with ages between about 1 and 3 x 107 yr the fraction of Be stars with respect to normal B stars is larger at lower metallicities. This may suggest a higher rotation at lower metallicities for massive stars, due to a different history of star formation.
Type Ia Supernovae and Planets in Star Clusters
Authors: Shara Michael M. , Hurley Jarrod R. 
Published: July 2016

Star clusters are remarkably efficient (relative to the field) at making type Ia supernovae candidates: very short period, massive double-white-dwarf stars and giant-white dwarf binaries. The high frequency of these systems is the result of dynamical encounters between (mostly) primordial binaries and other cluster stars. Orbital hardening rapidly drives the degenerate binaries to periods under ∼ 10 hours. Gravitational radiation emission and mergers then produce supra-Chandrasekhar objects in less than a Hubble time.We also find that free-floating planets can remain bound to a star cluster for much longer than was previously assumed: of the order of the cluster half-mass relaxation timescale as opposed to the crossing-time. The planets in our N-body study are of Jupiter mass and are initially placed in circular orbits of between 0.05 and 50 AU about a parent star whose mass is chosen from a realistic initial mass function. This result is important in the context of the preliminary detection of a population of free-floating sub-stellar objects in the globular cluster M22.
Upper Limit to the Deuterium Abundance in Planetary Nebulae
Authors: Hébrard G. , Péquignot D. , Walsh J. R. , Morisset C. , Vidal-Madjar A. , Ferlet R. 
Published: July 2016

We recently reported the first detection of the deuterium Balmer series in emission in H II regions, performed at the CFHT (Hébrard et al. 2000a) and at the VLT (Hébrard et al. 2000b). These narrow lines are excited by UV continuum fuorescence and arise at the atomic interface between H II regions and molecular clouds.Following this discovery, we used the CFHT with the Gecko spectrograph to observe Balmer lines in planetary nebulae. The non-detection of the deuterium Balmer lines in planetary nebulae represents the first observational evidence that this isotope was, as expected, destroyed in the parent stars.
HST Measurements of the Angular Expansion, Kinematics and Distance of the Planetary Nebula Bd+30°3639
Authors: Harrington J. Patrick , Li Jianyang , Borkowski Kazimierz J. 
Published: July 2016

The HST WFPC2 camera was used to obtain images of the planetary nebula BD+30°3639 at two epochs separated by 5.66 years. The expansion of the nebula in Hα and [N II] has been measured using several methods. Detailed expansion maps for both emission lines were constructed from nearly 200 almost independent features. There is good agreement between the (independent) Hα and [N II] proper motions. There are clear deviations from uniform radial expansion, with higher expansion rates in regions where the shell is faintest, such as the south-west quadrant.HST STIS echelle spectra obtained in the C II] λ2326 multiplet provide well-resolved expansion velocities at two position angles. We find that the central velocity split is ±36.3 km s-1 at a position angle of 99°.To determine the distance of BD+30°3639 by comparison of the angular expansion and the radial expansion, we must address the problem of the three dimensional shape of the nebula. We measured the angular expansion along the position of the 99° echelle slit, finding displacements of 4.25 mas yr-1 at the shell edge (2″.47 from the center). If the nebula were spherical, this would imply a distance of 1.80 kpc. But there is evidence that the nebula is elongated along the line of sight, which suggests that the actual distance is less. Radio continuum images from 5 and 15 GHz VLA observations provide information on the extent of the radial elongation. We fit the radio brightness variation and the echelle data by approximating the nebula as an ellipsoid. Our model has an axial ratio of 1.56, is inclined to the line of sight by 9°.7, and exhibits an expansion in the plane of the sky which is 2/3 that in the radial direction, leading to a distance of 1.2 kpc. Based on a recent model atmosphere (Crowther et al., these proceedings), this distance implies a stellar luminosity of 4250 L⊙.
Simulation and Modeling of Transit Eclipses by Planets
Authors: Milone E.F. , Williams M. D. , Stagg C. R. , McClure M.L. , Winmill B. Desnoyers , Brown T. , Charbonneau D. , Gilliland R. L. , Henry G. W. , Kallrath J. , Marcy G. W. , Terrell Dirk , VanHamme W. 
Published: July 2016

Light curve analysis by MDW of the photometry and RV data accumulated to date on HD 209458 has made use of a simulations database created for an 8-day HST observing project led by RLG to look for transits in 47 Tuc. We report progress in developing a consistent set of parameters obtained with our versions of the Wilson-Devinney program, WD98 and wd98k93, specially modified to treat large grid sizes, corresponding to objects with radii exceeding 0.7RJ and masses greater than 0.1 MJ.This work is supported in part by grants to EFM by Canadian NSERC and by the Univ. of Calgary Research Grants Committee.
Detection of a Far IR Excess with DIRBE at 60 and 100 Microns
Authors: Finkbeiner D. P. , Davis Marc , Schlegel David 
Published: July 2016

From analysis of the DIRBE weekly averaged sky maps, we have detected substantial flux in the 60 μm and 100 μm channels in excess of expected zodiacal and Galactic emission (Finkbeiner, D.P., et al. 2000, ApJ, to be published, astro-ph/0004175). Two methods are used to separate zodiacal light from more distant emission. Both methods give consistent results at 60 μm and 100 μm. The observed signal is consistent with an isotropic background of vIv = 28.1 ± 1.8 ± 7 (syst) nWm−2sr−1 at 60 μm and 24.6 ± 2.5 ± 8 (syst) nW m−2 sr−1 at 100 μm.The IR excess detected at 140 and 240 μm by these methods agrees with previous measurements, which are thought to be the cosmic infrared background (CIB). The detections at 60 and 100 μm are new. While this new excess is not necessarily the CIB, we have ruled out all known sources of emission in the solar system and Galaxy. We therefore tentatively interpret this signal as the CIB and consider the implications of such energy production from the viewpoint of star formation efficiency and black hole accretion efficiency. However, the IR excess exceeds limits on the CIB derived from the inferred opacity of the intergalactic medium to observed TeV photons, thus casting doubt on this interpretation. There is currently no satisfactory explanation for the 60 – 100 μm excess.
Far Infrared Extragalactic Background Radiation: Source Counts with ISOPHOT
Authors: Juvela M. , Mattila K. , Lemke D. 
Published: July 2016

We have searched for point-like sources in eight fields mapped at two or three wavelengths between 90 μm and 180 μm with the ISOPHOT instrument aboard the ISO satellite. Most of the 55 sources detected are suspected to be extragalactic and cannot be associated with previously known objects. It is probable, also from the far-infrared (FIR) spectral energy distributions, that dust-enshrouded, distant galaxies form a significant fraction of the sources.We present a tentative list of the detected extragalactic FIR-sources. Based on the analyzed data we estimate the number density of extragalactic sources at wavelengths 90 μm, 150 μm and 180 μm and at flux density levels down to 100 mJy to be 1 x 105 sr−1, 2x105 sr−1, and 3xl05 sr−1, respectively.Models of strong galaxy evolution are in best agreement with our results, although the number of detections exceeds predictions of most models. No-evolution models can be rejected at a high confidence level. Comparison with COBE results indicates that at 90 μm the detected sources correspond to >20% of the extragalactic background light. At longer wavelengths the corresponding fraction is ~ 10%.
Models for Infrared and Submillimetre Counts and Backgrounds
Authors: Rowan-Robinson Michael 
Published: July 2016

A simple and versatile parametrized approach to the star formation history allows a quantitative investigation of the constraints from far infrared and submillimetre counts and background intensity measurements.The models include four spectral components: infrared cirrus, an M 82-like starburst, an Arp 220-like starburst and an AGN dust torus. The 60 μm luminosity function is determined for each chosen rate of evolution using the PSCz redshift data for 15000 galaxies. The proportions of each spectral type as a function of 60 μm luminosity are chosen for consistency with IRAS and SCUBA colour-luminosity relations, and with the fraction of AGN as a function of luminosity found in 12 μm samples.A good fit to the observed counts at 0.44, 2.2, 15, 60, 90, 175 and 850 μm can be found with pure luminosity evolution in all 3 cosmological models investigated: Ω0 = 1, Ω0 = 0.3 (Λ = 0), and Ω0 = 0.3, Λ = 0.7. All 3 models also give an acceptable fit to the integrated background spectrum. The total mass-density of stars generated in all 3 cosmological models is consistent with that observed.
The Chemical Composition of the Wolf-Rayet Envelopes
Authors: Nugis T. 
Published: July 2016

Model-independent information on the chemical composition of WR stars is obtained from the lines of different ions arising at transitions between highly excited energy levels.The chemical composition of WR stars strongly differs from the mean cosmic composition. Nuclear processed CNO products of H-burning are revealed in WN envelopes and He-burning products in WC envelopes. The matter enriched with He and N is also present in some ring nebulae around WN stars.
Concluding Remarks (I)
Authors: Baschek B. 
Published: July 2016

After a week of highly interesting discussions on ‘stellar evolution and the photospheric abundance connection’ we now come to resume the contributions to this Symposium. This task has been divided up among three of us, arranged according to the course of stellar evolution, and in alphabetical order of the speakers (Baschek, Lambert, van Horn). I begin with the essentially unevolved stars, recalling some results and problems, not systematically but rather selected from my own interests.First I should like to briefly reconsider the accuracy of abundance determinations in view of the contributions following my review. Then some comments on stellar models are given, followed by a few remarks about peculiar A stars. Finally, the similarity of the oxygen abundance in Magellanic Cloud B stars and galactic population II stars is pointed out.
Measuring the Evolution of the M/L ratio from the Fundamental Plane in Cl 0024+16 atz=0.39
Authors: Franx Marijn , van Dokkum Pieter G. 
Published: July 2016

The existence of the Fundamental Plane of early-type galaxies implies that theM/Lratios of early-types are well behaved. It provides therefore an important tool to measure the evolution of theM/Lratio with redshift. These measurements, in combination with measurements of the evolution of the luminosity function, can be used to constrain the mass evolution of galaxies.We present the Fundamental Plane relation measured for galaxies in the rich cluster CL 0024+16 atz=0.391. The galaxies satisfy a tight Fundamental Plane, with relatively low scatter (15 %). TheM/Lis 31 ± 12 % lower than theM/Lmeasured in Coma, which is consistent with simple evolutionary models. Hence, galaxies with very similar dynamical properties existed at az=0.4.More, and deeper data are needed to measure the evolution of the slope and the scatter of the Fundamental Plane to higher accuracy. Furthermore, data on the richest nearby clusters would be valuable to test the hypothesis that the Fundamental Plane is independent of cluster environment.
The DN − σ and Fundamental Plane Relations as Distance Indicators of Early Type Galaxies in the Virgo and Fornax Clusters
Authors: D'Onofrio M. , Zaggia S. , Capaccioli M. , Longo G. , Caon N. 
Published: July 2016

We investigate the properties of early-type galaxies as distance indicators by applying the Dn – σ, Fundamental Plane (FP), and log(m) – log re relations to a complete and fairly homogeneous sample of galaxies members of the Virgo and Fornax clusters. The relative mean distance of the two clusters can be derived with an accuracy up to ∼ 3% provided that the internal kinematics of the galaxies is taken into account and a correct statistical approach is used.The residuals of the Dn – σ and FP relationships do not correlate with many structural and geometrical parameters of the galaxies: the mean effective surface brightness, the total luminosity, the average ellipticity and the Fourier coefficient a4 of the isophotes, and, the exponent m of the r1/m law which parametrizes the shape of the light profiles. On the other hand, the kinematics of the galaxies affect both relations producing residuals that correlate with the maximum rotation velocity Vmax and the (V/σ) ratio.Once confirmed by future more accurate observations, this effect would introduce a sistematic bias in the distance determination of the clusters; a problem difficult to manage if the internal kinematics of the cluster members is unknown.