bluuebunny/crossref_metadata_2025 huggingface dataset:
Model Planetaries with rapidly evolving central stars: A case for FG Sge
Authors: Kifonidis K. , Schönberner D.
Published: July 2016

Ever since the pioneering work of Schönberner (1979, A&A, 79, 108) and Iben (1984, ApJ, 277, 333) who showed that the evolution of post-AGB remnants might be affected by late thermal pulses of the helium-burning shell, resulting in a temporary growth of these objects to red giant dimensions, many attempts were made to explain a number of puzzling objects, among them the well-known variable central star FG Sge as well as the R CrB and PG 1159 stars, by this so-called “born-again AGB” scenario (Iben et al. 1983, ApJ, 264, 605; Iben & MacDonald 1995, in: White Dwarfs, Springer, p. 48). However, it is still not clear if the frequency of occurrence of such events is high enough as to be consistent with the number of born-again candidates. This is due to the very short evolutionary timescales during the pulse and the character of the post-pulse evolution which resembles the first post-AGB phase and makes it difficult for an observer to distinguish such objects from “normal” central stars.
Improved simulations of the Planetary Nebula luminosity function
Authors: Méndez R. H. , Soffner T.
Published: July 2016

We have developed a new procedure for the generation of a planetary nebula luminosity function (PNLF), improving on previous work (Mendez et al. 1993 A&A 275, 534). The procedure is based, as before, on an exponential central star mass distribution, on H-burning post-AGB evolutionary tracks, and on the avoidance of nebular models for the calculation of nebular fluxes. We have added new post-AGB evolutionary tracks (Blöcker 1995 A&A 299, 755) and introduced the following improvements:
An analysis of ultraviolet (IUE) and optical spectra of high latitude Planetary Nebulae Hb 7 and Sp 3
Authors: Parthasarathy M. , Acker A. , de Martino D. , Koeppen J. , Leindecker W.
Published: July 2016

Hb 7 (003.9 - 14.9) and Sp 3 (342.5 - 14.3) are high galactic latitude planetary nebulae. Ultraviolet spectra obtained with the IUE reveal UV stellar continuum and P - Cygni stellar wind profiles of NV and CIV indicating post-AGB mass loss from the central stars of these two PN. From an analysis of optical and ultraviolet spectra we have derived the parameters of the central stars and nebulae. The IUE ultaviolet continuum shows that the central stars of Hb 7 and Sp3 are 08 stars. The Si IV 1400A doublet in the spectra of both these stars is very weak or absent most likely due to underabundance of Si and due to also due to earlier spectral type (O 8). The Si IV lines in hot stars are sensitive to surface gravity, their weakness suggests that surface gravity the central stars of Hb7 and Sp3 is relatively higher. The terminal velocity of the stellar wind in Hb7 and Sp 3 are found to be −2460 km/sec and −3630 km/sec respectively.
UV fluxes in elliptical galaxies
Authors: Chiosi Cesare
Published: July 2016

The key properties of elliptical galaxies are compared to present-day models calling attention on several points of contradiction. The nature of the UV fluxes and their usefulness to cast light on the age-metallicity dilemma are discussed. Finally, preliminary results of an attempt aimed at reconciling theory with observations by means of an new IMF are presented.
Post-AGB stars as extragalactic candles
Authors: Bond Howard E.
Published: July 2016

The extragalactic distance scale depends heavily on one primary distance indicator: Cepheid variables. Given the conflict between stellar ages and the age of the Universe implied by H0, it is worth checking the zero point with as many independent methods as possible.
Correlation Functions of CMB Anisotropy and Polarization
Authors: Ng Kin-Wang
Published: July 2016

While the temperature anisotropy of the cosmic microwave background is proved to be a promising tool for probing the early Universe, the CMB polarization is another important clue for extracting more cosmic information. We give a full analysis of the auto- and cross-correlations between the CMB Stokes parameters. In particular, we derive the windowing function for an antenna with Gaussian response in polarization experiment, and construct correlation function estimators corrected for instrumental noise. They are applied to calculate the signal to noise ratios for future MAP and Planck anisotropy and polarization measurements.
Galaxy Formation: the Role of Gravitational Collisions
Authors: Balland C. , Silk J. , Schaeffer R.
Published: July 2016

Some aspect of a semi-empirical model of galaxy formation is presented. In this model, galaxy formation proceeds through a series of rapid non-merging collisions with surrounding objects. For a given galaxy, a collision at an epoch z is characterized in terms of the fractional rate of change of binding energy induced by the tidal field [1]. The total rate of change of binding energy during the lifetime of the galaxy is computed in an Einstein-de Sitter universe, assuming that collisions continuously occur from birth up to the present day against a set of background galaxies with various masses. Rules for the formation of morphological types are then derived along the following (phenomenological) line: substantial or efficient collisions – characterized by a high rate of energy exchange – drive the formation of elliptical galaxies, whereas little or inefficient collisions lead to the formation of disks. These rules are coupled to the Press & Schechter mass function for a Cold Dark Matter spectrum normalized to the present distribution of X-ray clusters, allowing one to predict the evolution, for each morphological type, of number densities as a function of redshift. The model reproduces the observed present-day morphology-density relation [2] and predicts the formation redshift of field ellipticals to be z ≥ 2, while spirals form at z ≤ 1.5. Predictions are made for the redshift evolution of morphological populations in the field as well as in clusters (see [3] for more details).
Structure of Dark Matter Halo
Authors: Fukushige Toshiyuki , Makino Junichiro
Published: July 2016

We performed N-body simulation on special-purpose computer, GRAPE-4, to investigate the structure of dark matter halos (Fukushige, T. and Makino, J. 1997, ApJL, 477, L9). Universal profile proposed by Navarro, Frenk, and White (1996, ApJ, 462, 563), which has cusp with density profiles ρ ∝r−1in density profile, cannot be reproduced in the standard Cold Dark Matter (CDM) picture of hierarchical clustering. Previous claims to the contrary were based on simulations with relatively few particles, and substantial softening. We performed simulations with particle numbers an order of magnitude higher, and essentially no softening, and found that typical central density profiles are clearly steeper than ρ ∝r−1, as shown in Figure 1. In addition, we confirm the presence of a temperature inversion in the inner 5 kpc of massive galactic halos, and give a natural explanation for formation of the temperature structure.
Wide Binaries and the Age of the Galaxy
Authors: Oswalt T.D. , Smith J.A. , Wood M.A.
Published: July 2016

Using B, V, R, I photometric parallaxes for components of wide binaries, new bolometric corrections by Bergeron et al. (1995) and cooling curves by Wood (1995), we have determined the white dwarf luminosity function (WDLF; Oswalt et al. 1996). A minimum age of 9.5+1.1−0.8 Gyr is implied for the Galactic disk; arbitrarily old models are consistent at the +2σ level. Smith (1997) confirms these results using a much larger sample and similar methodology. Using these same new models, Wood & Oswalt (1997) show that the WDLF of Liebert et al. (1988) yields an age of 7.5+0.5−0.5 Gyr, more than 20% younger than their original estimate.
Noncompact Objects as Microlenses
Authors: Zakharov A. F. , Sazhin M.V.
Published: July 2016

The first results of observations of microlensing have discovered a phenomenon, predicted in the papers of Byalko (1969) and Paczynsky (1986). A character of the gravitational microlens is unknown till now, although the most widespread hypothesis assumes that they are compact dark objects as brown dwarfs. Nevertheless, they could be presented by another objects, in particular, an existence of the dark objects consisting of the super symmetrical weakly interacting particles (neutralino) has been recently discussed in the papers of Gurevich et al. We consider microlensing by a neutralino star in framework of a rough model which is rather clear and we obtain analytical expressions for results. We approximate the density of distribution mass of a neutralino star in formwhere r is the current value of a distant from star's center, ρo is mass density of a neutralino star for distance a0 from a center, an is a “radius” neutralino star. The detailed analysis of the model is presented in the papers of Zakharov & Sazhin (1996a, 1996b). This research has been supported in part by Russian Foundation of Fundamental Research (grant N 96-02-17434).
The X-Ray Background and the AGN Luminosity Function
Authors: Hasinger G.
Published: July 2016

ROSAT deep and shallow surveys have provided an almost complete inventory of the constituents of the soft X-ray background which led to a population synthesis model for the whole X-ray background with interesting cosmological consequences. According to this model the X-ray background is the “echo” of mass accretion onto supermassive black holes, integrated over cosmic time. A new determination of the soft X-ray luminosity function of active galactic nuclei (AGN) is consistent with pure density evolution, and the comoving volume density of AGN at redshift 2–3 approaches that of local normal galaxies. This indicates that many larger galaxies contain black holes and it is likely that the bulk of the black holes was produced before most of the stars in the universe. However, only X-ray surveys in the harder energy bands, where the maximum of the energy density of the X-ray background resides, will provide the acid test of this picture.
The Mass Function of Cosmic Structures
Authors: Audit E. , Teyssier R. , Alimi J.-M.
Published: July 2016

We have investigated some modifications to the Press & Schechter (PS) (1974) prescription resulting from shear and tidal effects (Audit & al. 1997a). These modifications rely on more realistic treatments of the collapse process than the standard approach based on the spherical model.
Typical Scales in Distribution of IRAS Galaxies
Authors: Deng Z. G. , Xia X. Y. , Börner G.
Published: July 2016

Typical scales in the distribution of IRAS galaxies have been searched for with the unnormalized pair count method given by Mo et al.1. Samples consist of a) galaxies from QDOT with | b | ≥ 20°; b) galaxies from the IRAS faint source catalog(FSC) with f60 ≥ 0.3 Jy and | b | ≥ 30°. Galaxies with b ≥ 0 and b ≤ 0 were treated as independent samples in our analysis.
Formation Mechanism of Hierarchical Astronomical Objects in the Cosmic String Scheme
Authors: Hara Tetsuya , Miyoshi Sigeru , Mähönen Petri
Published: July 2016

Because of the angular deficit around cosmic string, cold dark matter(CDM) gets the velocity toward the plane of moving string and wake is formed there. It means that CDM body is cut by string, two blocks move each other, and the overlapped region becomes wake. The wake and/or block size is determined by the horizon size at zi when the wake is triggered by the string. The nonlinearity and/or thickness of the wake depends on the moving length of CDM toward the wake which depends on zi, the line density and velocity of string.
N-Body Simulation of Large Scale Structure in the Universe with Oscillating Scalar Field
Authors: Kawabata K. , Taguchi H. , Andoh Y.
Published: July 2016

Using the particle-mesh method with 1283 grids and 643 particles, we have carried out a number of N-body simulations of the large scale structure for the cosmological model proposed by Fukuyama et al.(1996): this model contains the matter(Ω0) as well as a scalar field(Φ) with a finite mass that couples non-minimally with the scalar curvature R through the form of 1/2ηΦ2R, where η(= −80) is the coupling constant.

For simplicity, we have adopted the same values as those employed by Fukuyama et al.(1996) for all the parameters other than Ω0, fo which we have varied from 0.001 to 0.15. In performing our simulation, we further assume that only the density of matter ρ spatially fluctuates. The initial condition is created by perturbing the homogeneous distribution of the particles by means of the random Gaussian Harrison-Zeldovich spectrum.

The two-point correlation function ξ(r) is then compputed for each of the resulting structures to compare with the observational data(Davis and Peebles, 1983). It is interesting to note that the structure formation appears to be achieved rather straightforwardly with the scalar field model. However, in order to yield an agreement between the theoretical and the observational two-point correlation functions, we seem to require the Ω0 value much larger than 0.01 adopted by Fukuyama et al.(1996).
Cosmological N-Body Simulations with Grape-4
Authors: Kawai A. , Fukushige T. , Taiji M. , Makino J. , Sugimoto D.
Published: July 2016

We compared the calculation performance of cosmological N-body simulations with and without GRAPE-4. A modified Barnes-Hut treecode was used for these simulations. GRAPE(GRAvity piPE) is a special-purpose computer for gravitational N-body simulations. The newest hardware GRAPE-4 achieved a quite high peak performance (1.08 Tflops). In cosmological N-body simulations, a large number of particles is required and fast algorithms such as Barnes-Hut treecode or P3M/PM are usually used. GRAPE-4 can accelearte such algorithms. In paticular, the PCI interface recently completed allows us to use fast host computer, thus it improved the performance of these fast algorithms. Figure 1 shows the CPU time per one timestep as functions of force calculation error for both systems with and without GRAPE-4.
Possible Supercluster at z ∼ 0.25 towards the South Galactic Pole
Authors: Kawasaki W. , Shimasaku K. , Kashikawa N. , Sekiguchi M. , Doi M. , Okamura S.
Published: July 2016

We have observed a 0.7×1.2deg2 field in the SGP region with the UT / NAOJ Mosaic CCD Camera attached to the 40-inch Swope Telescope at Las Campanas Observatory, and constructed a sample of 1150 galaxies in the region down to R=20.5. Then we applied to the sample a new, objective cluster-finding technique, which is an improved variant of the so-called “matched-filter technique” pioneered by Postman et al. (1996). Using projected positions and apparent magnitudes of galaxies simultaneously, this technique can, not only find cluster candidates, but also estimate their redshifts and richnesses. A number of Monte Carlo simulations demonstrated enough accuracies of the estimations and much lower spurious detection rate than that by conventional cluster-finding methods which use only surface density of galaxies.
A New Method to Estimate Cosmological Parameters Using the Baryon Fraction of Clusters of Galaxies
Authors: Sasaki Shin
Published: July 2016

We propose a new method to estimate cosmological parameters using the baryon fraction of clusters of galaxies for a range of redshifts. The basic assumption is that the baryon fraction of clusters is constant, which is a reasonable assumption when it is averaged within a Mpc scale. We find that the baryon fraction vs. redshift diagram can estimate the cosmological parameters, since the derived value of the baryon fraction from observations depends on the adopted value of cosmological parameters through the angular diameter distance (e.g. Sasaki, S. 1996, PASJ48. L119).
Subclusters in the Virgo Area
Authors: Shao Z.Y.
Published: July 2016

By using the data of the CfA redshift catalogue(1995.4), the structure, substructures and some astrophysical properties of the Virgo galaxy cluster are studied in depth (Shao 1996).
Radio Source Counts at 232 MHZ
Authors: Xizhen Zhang
Published: July 2016

About 30000 sources were cataloged by the Miyun 232 MHz survey1 covering sky area north of declination 30°. (Zhang et al., 1997). For source count purpose, subcounts for different ratio of signal to noise and galactic latitude of steep-spectrum and flatspectrum sources were carried out respectively.
Association of X-ray Quasars with Active Galaxies
Authors: Arp H.
Published: July 2016

Analysis of ROSAT observations demonstrate that X-ray sources are associated with bright Seyfert galaxies up to distances of about 40 arc min. These X-ray sources are predominantly identified with blue stellar objects (BSO's) some of which are already catalogued as quasars.

The X-ray sources tend to pair and align across the nucleus of the active Seyfert. Enough redshifts are now available to indicate the similarities of the redshifts in the quasar pairs and to enable computation of ejection velocities of about 0.1c.
A Few Things We Do Not Know About Stars and Model Atmospheres
Authors: Kurucz Robert L.
Published: July 2016

A similar presentation has been published in the volume New Quests in Stellar Astrophysics: The Link between Stars and Cosmology Astrophysics and Space Science Library, vol. 274 (eds. M. Chavez, A. Bressan, A. Buzzoni, and D. Mayya) Dordrecht: Kluwer, pp. 1-10, 2002. Here I quote the abstract and list only the section headings.
Dynamical Behavior of the Upper Solar Photosphere
Authors: Rutten Robert J.
Published: July 2016

The dynamical behavior of upper cool-star photospheres constitutes the next step in realistic atmosphere modeling after the successful numerical implementation of low-photosphere granulation. The solar example shows that this behavior is complex even when magnetism is ignored. Acoustic waves are a principal ingredient, but so are atmospheric gravity waves. Acoustic events provide less pistoning than expected. Correlation and Fourier analyses of image sequences from TRACE demonstrate the ubiquity of gravity waves.
Stellar Photospheres: Success, Failure, Ambiguity, & Ambition
Authors: Gray David F.
Published: July 2016

Models are compared with observations in several examples, including spectroscopic temperature measurement, irradiance variations, stellar rotation from line profiles, and velocity fields in stellar photospheres. A few key issues for investigations in the near future are suggested.
Round Table Summary: Winds and Pulsating Stars
Authors: Willson Lee Anne
Published: July 2016

Speakers for this session were selected according to our perceptions about the frontier areas in dynamical atmospheres, the atmospheres of very cool stars, and stellar winds. This summary of posters and topics raised in the round table discussion opens with a brief summary of current issues in modeling pulsating stars and winds. Observational constraints are emphasized in Section 3. on “peeling the onion” of the atmosphere/wind structure. Section 4. covers a variety of methods for detecting and measuring stellar winds. The concluding remarks include some questions facing theorists and observers working in this field.
Closing Remarks
Authors: Landstreet John D.
Published: July 2016

I offer some comments on the importance of our field (rather modestly, we could say that we are central to almost the entire enterprise of astrophysics) and on some of recent developments in our field (an impressive record of difficult problems attacked and – often – solved). Finally I consider some of the work still left to be done, which is assigned to the participants, their colleagues, friends, and students as homework to be done, as far as possible, for the next major stellar atmosphere meeting.
Two Southern Low Excitation Planetary Nebulae
Authors: Moreno H. , Gutiérrez-Moreno A. , Cortés G.
Published: July 2016

Within a spectroscopic study of some southern planetary nebulae, we have observed 32 objects. Some of them are symbiotic or suspected symbiotic stars, and one (He 2-61) is evidently not an emission object.
Planetary Nebula He 2-467 Turned out to be the Symbiotic Star with a Period about 500 Days
Authors: Arkhipova V. P. , Noskova R. I.
Published: July 2016

By means of broad and narrow-band photometry in UBV spectral diapason the variability of the object He 2-467 earlier classified as peculiar central star of planetary nebula has been revealed. The light amplitude significantly decreases with the wavelength, from 1m.7 in U-band to 0m.3 in V. The brightness variations were found to be periodic, with P ≈ 500 days. The observations of He 2-467 have been interpreted using the model of binary consisting of very hot subdwarf and G5 II giant. The parameters of both components have been derived. The hot star is probably the evolved low mass nucleus of planetary nebula already dissipated. The periodic variations in U-band may be the result of the reflection effect due to the presence of hot extended region on the side of cold star facing the subdwarf. The subdwarf UV-flux can heat and ionize the upper atmosphere of the giant giving birth to the emission lines and Balmer continuum. The yellow symbiotics to which He 2-467 belongs may be predecessors of red symbiotics with M-giants.
Infrared Energy Distribution of Selected Planetary Nebulae
Authors: Persi P. , Preite-Martinez A. , Ferrari-Toniolo M.
Published: July 2016

Using the IRAS and near-IR photometry obtained at the 1-m, 3.6-m ESO telescopes, and 1.5-m TIRGO telescope, we will discuss the 1 - 100 microns energy distribution of selected PNe.
Is NGC 2242 a New Planetary Nebula?
Authors: Jiying Liu , Yongwei Huang , Xingchun Feng
Published: July 2016

An interesting object was found on the IIIaJ objective prism plate SP1270, taken on Jan. 12.6 UT, 1983 with the Beijing Observatory 60/90-cm Schmidt telescope plus 5°.3 objective prism with a dispersion of 580 A/mm at Hγ. The emission lines [O III]λλ4959+5007 and Hβ were extremely strong. The lines Hγ—Hδ and [O II]λ3727, all in emission, were broad and conspicuous. Two prominent emissions were tentatively identified as He II λ4686 and He II λ4542. Of all these lines none showed any noticeable redshift. It belongs to the Galaxy. The overall spectrum looked like that of a planetary nebula. But on the POSS overlay this object was designated as RNGC 2242 and ZWG 204.005. It was listed as a galaxy either in ZWG, or in A Master List of Nonstellar Optical Astronomical Objects, but it was absent from any previous catalogues of the planetary nebula.
An Infrared Search for New Planetary Nebulae
Authors: Pottasch S. R. , Esteban C. , Manchado A. , Mampaso A.
Published: July 2016

We present the first results of a large scale infrared search for new planetary nebulae. More than 1000 unidentified sources were selected from the IRS PSC having infrared colours similar to those of known PN's. Subsequent near-infrared photometry and optical spectroscopy will be made to investigate their precise nature. We report here one to five microns photometry of 30 such sources obtained with the 1.5-m CSM telescope (Tenerife, Spain). The preliminary results indicate that many of the observed sources have near infrared colours of heavily reddened PN's (Av greater than 30 magnitudes in some cases), while a smaller fraction could represent obscured normal stars or giants surrounded by circumstellar envelopes.
Galactic Distribution, Radial Velocities and Masses of PN
Authors: Maciel Walter J.
Published: July 2016

Since the discovery in 1779 of the first planetary nebula in the Lyra constellation by Antoine Darquier, the total number of objects known as PN has been steadily increasing. About 1600 PN have been identified in the Galaxy, although 10–20% are probably misclassified objects, which include H II regions, reflection nebulae, symbiotic stars, etc. (see for example Kohoutek, 1987; Acker et al., 1987; Stenholm and Acker, 1987).
CCD Images of Southern Hemisphere Planetary Nebulae
Authors: Lutz Julie , Jo Lame Nancy
Published: July 2016

A large, long-term survey of southern hemisphere planetary nebulae is being undertaken with several narrow-band filters (primarily [N II], H-alpha, [O III] and He II) on the 0.9-m telescope at CTIO using a TI CCD chip. The purposes of this survey are to get sizes and morphological classifications for nebulae that are little-known (indeed, some do not have size measurements at all) and to search for multiple shells and other structures that are of interest for studies of nebular formation and evolution.
The Temperature Structure of NGC 7027
Authors: Daub C. T. , Basart J. P.
Published: July 2016

Radio maps of the free-free radio continuum flux (angular resolution ≅ 1.3 arcseconds) from NGC 7027 were made with the VLA operating at 20-cm, 6-cm, and 2-cm wavelengths which are near and straddle unit optical depth. Mean line-of-sight electron temperature and emission measure distributions were calculated by pairing the 2-cm and 6-cm maps, and the electron temperature distribution on the near side of the nebula was then obtained from the 20-cm map. The results suggest that the energy balance is complex in this planetary. For example, mean line-of-sight temperatures are higher than average in the direction of one of the bright lobes but not in the direction of the other. Especially noteworthy is an apparent “hot spot” on the near side of the nebula which has no apparent relation to either of the bright lobes, but it is approximately coincident with the brightest portion of the optical image.
Spatial Deconvolution of IRAS Observations of Planetaries
Authors: Hawkins George , Zuckerman B.
Published: July 2016

The sizes of fifty planetaries at the four IRAS wavelengths are presented as a result of performing spatial deconvolution of survey mode data. We obtain an increase in resolving of a factor of about 2 or 3 from the normal IRAS detector sizes of 45″, 45″, 90″, and 180″ at wavelengths 12, 25, 60 and 100 microns. Most of the planetaries deconvolve at 12 and 25 microns to sizes equal to or smaller than the optical size. Some of the nebulae such as NGC 6720 and NGC 6543 show full width at half maximum at all IRAS wavelengths that are about equal to the optical size, while others give an increasing size with wavelength. The profiles of a few interesting cases are shown. The method and results should allow comparison with models for infrared emission from dust from planetary nebulae.
Unusual Emission Line Profiles of M1-1
Authors: Shibata Katsunori , Tamura Shin'ichi
Published: July 2016

In order to seek out intrinsically compact PN, we have observed high-excitation and angularly small PN, M1-1, with the intensified Reticon system (one-dimensional 1024 pixel-array) at the Coude focus of the 188 cm telescope. We have obtained highly resolved emission line profiles of [NII]λ6583, Hα, [OIII]λ5007, and HeIIλ4686 at several slit position angles. These lines were analyzed with the aid of Multiple Gaussian Method. From the analysis of their radial velocities and decomposed profiles, we can summarize our observational results as follows, (a) HeII were fitted by three Gaussians, those are main blue and red-components and an extremely red-shifted sub-component. Hα and [OIII] were decomposed into blue and red components. [NII] were fitted by single Gaussian.
Expansion Velocities of [NII] and [OIII] from Compact Planetary Nebulae
Authors: Shibata Katsunori , Tamura Shin'ichi
Published: July 2016

We observed the expansion velocities, Vexp[NII] and Vexp[OIII] of angularly small planetary nebulae(PNe) and examined the relations between expansion velocities and distance free parameters like relative emission line intensities of HeIIλ4686, [OIII]A5007, and [NII]λ6583. The expansion velocities of PNe are usually obtained from the emission lines of [OIII]λ5007. But these quantities obtained from [NII]λ6583 are more suitable to investigate the evolution of PNe because 0++ region is confined within inner part for lower and intermediate excitation PNe.
High and Low Resolution Spectra of Selected Planetary Nebulae
Authors: Cristiani S. , Sabbadin F. , Ortolani S.
Published: July 2016

High (CES spectrograph + RETICON at the CAT telescope) and low (B&C spectrograph + CCD at the 2.2-m telescope) resolution spectra of selected, southern planetary nebulae allowed to obtain the Hα and [NII] emission line profiles and the nebular emission line intensities in the spectral range λλ3650-9400 A. The Hα and [N II] emission line parameters were derived following the procedure used by Sabbadin (Monthly Not. Roy. Astron. Soc., 209, 889, 1984) and Ortolani and Sabbadin (Astron. Astrophys. Suppl. Series, 62, 17, 1985). Table 1 contains the relevant data for eight nebulae of the sample.
Observations of CO and HCN (J = 1−0) in NGC 2346 and NGC 7293 with the Nobeyama 45-m Telescope
Authors: Walsh J. R. , Clegg R.E.S. , Ukita N.
Published: July 2016

Many positions in the planetary nebulae NGC 2346 and NGC 7293 have been searched for CO (J = 1-0) and HCN (J = 1-0) emission. The beam was 15 arcsec at 115 GHz.
Low Resolution Spectroscopy of 13 Low Surface Brightness PN's
Authors: Manchado A. , Pottasch S. R. , Mampaso A.
Published: July 2016

We have obtained long-slit low resolution spectra (7.5 A resolution) of a sample of 13 low surface brightness planetary nebulae using the 2.5-m Isaac Newton Telescope (La Palma) with the Image Photon Counting System (IPCS) covering a spectral range from 3300 A to 7300 A. From those spectra we calculated the ionic and total abundances of 0, N, Ne and Ar. Variations in the ionization structure between the inner and the outer part are found in some nebulae although the total abundances appear not to change significantly along the nebulae.
Stromgren Photometry of the Central Stars of Planetary Nebulae
Authors: Costero R. , Echevarría J.
Published: July 2016

An attempt is made to deconvolve the contribution of the central star from that of nebular emission, in small and large Planetary Nebulae. The use of medium-band Strömgren photometry is possibly a more powerful tool than that of broad-band photometries to achieve meaningful stellar parameters, specially by means of a four-channel photometer. The various methods used to subtract the nebular contribution are analysed and the results of the first ubvy and HΒ observations are presented.
HFG1: A Planetary Nebula with a Close-Binary Nucleus
Authors: Bond Howard E. , Ciardullo Robin , Fleming Thomas A. , Grauer Albert D.
Published: July 2016

HFG1 (136+5°1) is a large, low-surface-brightness planetary nebula that was discovered by Heckathorn, Fesen, and Gull (Astrpn. Astronphys., 114, 414, 1982). in the autumn of 1986, photoelectric photometry by A.D.G. and H.E.B. showed that the 14th-mag central star of HFG1 is a large-amplitude variable. Subsequent CCD photometry by R.C. and H.E.B. reveals a sinusoidal variation with a period of 13.96 hr and an amplitude of 1.1 mag in the B band.
V605 Aquilae - The Most Extreme Hydrogen-Poor Object
Authors: Seitter Waltraut C.
Published: July 2016

V605 Aquilae, whose novalike outburst was observed in 1919, is the central object of the old planetary nebula A58. It is the only ‘nova’ known with a hydrogen-deficient carbon-rich outburst spectrum and a remnant consisting of a WC-type star and a nebula which appears to be totally void of hydrogen. The star shows a red continuum of magnitude 22.3 and a prominent line of CIV 580.8 nm with a total width of 4400 km/sec Other lines are extremely weak. The remnant nebula shows only forbidden lines of heavy elements. The strongest ones are due to the nebular transitions of [OIII],[NII],[OI]. IR [OII] is present, other ions are suspected. The nebula is an IRAS point source of temperature 170 K.
Planetary Nebulae as Standard Candles for Extragalactic Distances
Authors: Jacoby G. , Ford H. , Ciardullo R.
Published: July 2016

Although distances to galactic planetary nebulae are typically uncertain by factors near 2, there appears to be an upper limit to the integrated [O III] λ5007 absolute flux for planetary nebulae. This flux, 1.34 × 10−8 ergs/cm2/sec for a maximally bright planetary nebula at a distance of 1 kpc, can be used as a distance indicator when a sufficient number of planetaries have been identified in an external galaxy. Or one may compute the upper limit to the distance for galactic planetary nebulae based on this calibration.
The Proto-Planetary Nebula Vy 2-2
Authors: Clegg R. E. S. , Hoare M. G. , Walsh J. R.
Published: July 2016

High and low-resolution optical and near-IR spectroscopy of the candidate proto-planetary (or very young PN) Vy 2-2 (P-K 45 - 2°1) is reported. This object has associated OH maser emission and an angular diameter of only 0.4 arcsec, found from VLA and optical speckle interferometry. Empirical analysis gives the values Ne ≈3 × 105 cm−3, Te=11000(±1500)K. The electron temperature is quite uncertain because of the high density. Abundances of He, C, N, O, Ne and Ar are reported; the carbon abundance is uncertain as it relies on the C II λ4267Å line, since the object is too highly-reddened (c=1.8 ± 0.2) to be observed with IUE. We find He/H=0.10, O/H=4 × 10−4 and C/O=0.8. The HI Zanstra temperature is 38 000 K (for black-body). The spectrum shows broad stellar lines of He II λ4686, C III λ4647 and N III λ4640; the central star may be of type Of.
Infrared Photometry of OH/IR Stars
Authors: Peña Miriam , Fierro Julieta
Published: July 2016

We have initiated a near infrared photometric study of OH/IR stars and proposed protoplanetary nebulae, using the 2.12 m telescope and the IR photometric system at the Observatorio Astronómico Nacional in Baja California, México.
Some Dependences for Long-Period Variables and a Possible Scheme of their Evolution
Authors: Andronov I. L. , Kudashkina L. S. , Rudnitskij G. M.
Published: July 2016

Some dependences between the parameters for approximately 150 stars, of which 81 are sources of maser emission in molecular lines, are constructed. The following parameters are considered: period P, asymmetry (M-m) of the visual light curve, visual amplitude A, color index (I-K). We use the data of the General Catalogue of Variable Stars. For the stars Z Cyg, R Tau, R Peg, RT Vir, RX Boo, PZ Cas, U Her, and R Cas, some parameters were determined by the authors.
The Distribution of Planetary Nebula Nuclei in the log L-log T Plane: Inferences from Theory
Authors: Shaw R. A.
Published: July 2016

The expected distribution of planetary nebula nuclei (PNNs) on the log L-log T plane is calculated based upon modern stellar evolutionary theory, the initial mass function (IMF), and various assumptions concerning mass loss during post-main sequence evolution. The distribution is found to be insensitive to the assumed range of main-sequence progenitor mass, and to reasonable variations in the age and the star forming history of the galactic disk. Rather, the distribution is determined primarily by the heavy dependence of the evolution rate upon core mass, and secondarily upon the steepness of the IMF and other factors. The distribution is rather different than any found from observations, and probably reveals strong observational selection effects.
Snapshots of Evolving Model Planetary Nebulae
Authors: Stasińska Grażyna
Published: July 2016

We have constructed a series of model planetary nebulae along a sequence of evolutionary models for the central star, taking into account the expansion of the nebula. The calculations have been performed using the computer code PHOTO, which calculates the intensities of the emission lines emitted by a nebula in ionization and thermal equilibrium.
Evolution of Planetary Nebulae: A comparison with Observed Central Stars
Authors: Schmidt-Voigt M.
Published: July 2016

The relation between nebular excitation E(He II λ4686/Hβ-ratio) and absolute visual magnitude of the central star (CS) is compared with hydrodynamical models of planetary nebulae (PNe) from Schmidt-Voigt and Köppen (Astron. Astrophys., 174, 211 and 223) (see figure below, data from D. Schönberner, Astron. Astrophys., 169, 189). Models marked by drawn lines have a 0.644 M⊙ CS following a Schönberner track, an initially expelled PN of 0.1 M⊙, and different mass loss rates of the precursor star on the AGB, described by the Reimers parameter η;η = 1 corresponds to a mass loss rate of 1.55 × 10−6M⊙ α−1 the dashed line model has a higher initially expelled mass (0.3 M⊙), the dash-dotted line model a CS of 0.6 M⊙ which evolves more slowly. Model numbers refer to the above cited studies. Since MV increases with evolutionary time, the MV axis represents a (highly) nonlinear time axis: for MV < 4 the CS heats up towards its temperature maximum and the PN is optically thin. Differences for high excitation nebulae are most probably due to different helium abundances. When the rate of ionizing photons decreases as the nuclear energy sources extinguish (MV > 4), the excitation may decline, depending on the density in the nebula. For the so called “accreting models” (M > 10−6M⊙ α−1) the mass accretion from the AGB wind determines the density hence nebular excitation. For an AGB mass loss rate M < 10−5M⊙α−1 the numerical results approximately fit an exponential law E= E0exp (-M⊙) with E0 ≊ 1.1 and M⊙ ≊ 6.1 × 10−6M⊙ α−1. From the spread of the observed E(MV = 4) we conclude a mean AGB mass loss rate of 6.+3.3−2.3 10−6M⊙ α−1 within 1σ error bars. Obviously the model 11 reproduces the data best since most of the observed objects are found in the dark shadowed regions of the histogram. This is totally consistent with our previous results (cited above). The colliding-wind models, having no initially PN, behave quite similar as model 11.
Summarizing Remarks on the Structure and Evolution of Planetary Nebulae and Properties of their Central Stars
Authors: Aller L. H.
Published: July 2016

To review or attempt to summarize a conference such as this recalls the request our department office once received from a little fourth-grade schoolgirl: “I'm doing a science project on the stars. Tell me all about them on two pages.” We can only try to look at the broad picture and attempt to identify problems that require special emphasis or attention.
The Evolution of Disk Galaxies
Authors: Strom S. E. , Strom K. M.
Published: July 2016

The past decade has witnessed dramatic changes both in our conceptual models of disk-system formation and evolution and in the power of new observational techniques to confront, challenge, and redefine these models. In this contribution, we would like to review recent optical wavelength studies of spiral and SO galaxies which appear to influence our understanding of disk-system evolution. Particular emphasis will be placed on the effects of environment on evolutionary processes, since it appears likely that the addition or removal of gas during the lifetime of a disk system may often be dominant in controlling its appearance.
Velocity Dispersion in the Bulge of M31; Dynamical Model
Authors: Monnet G. , Pellet A. , Simien F.
Published: July 2016

1) Photometry from de Vaucouleurs 1958 shows a bulge obeying the r1/4 law up to less than 5 pc from the center with an effective radius re = 17′5. In the region from 0.01 to 0.2 re, equal luminosity curves are well approximated by similar ellipses of axial ratio 0.68. The reduced spatial density υ* and the reduced gravitationnal potential φ* (i.e. for a mass to luminosity ratio f equal to 1) can then be easily computed (Monnet and Simien 1977).
Radio Properties of Active Nearby Spiral Galaxies
Authors: de Bruyn A. G.
Published: July 2016

Before reviewing the radio properties of active spiral galaxies it is appropriate, as well as instructive, to think about a working definition of an active galaxy. This may seem a trivial point when we consider classes of objects like Seyfert galaxies or radio galaxies but this is much less so when we inspect the nearby systems. In a sample of nearby galaxies one is likely to encounter much more milder forms of activity than that known from studies of more distant galaxies. This is, of course, due to the fact that the latter have beenselectivelytaken from a much larger reservoir of objects. (Although this may seem a disadvantage from an observational point of view, there are some clear advantages as well. Firstly, we can obtain a much better linear resolution once we have been able to isolate the active nearby galaxies and, secondly, we eventually may hope to learn more about the physical situation that existed prior to the onset of the active period and how the surrounding medium reacts to the activity.)
Emission from the Nuclei of Nearby Galaxies: Evidence for Massive Black Holes?
Authors: Rees M.J.
Published: July 2016

The non-stellar activity in the nuclei of nearby galaxies poses problems of its own. But it gains added interest insofar as it may provide clues to the nature of quasars and the unusually energetic nuclei of some more remote galaxies. The evident qualitative resemblance between these spectacular phenomena and some of the nearby galactic nuclei discussed at this symposium suggests that we may be witnessing a scaled-down or slow-motion version of the same physical mechanism; and the likelihood that dead quasars vastly outnumber living ones suggests that defunct remnants - perhaps displaying some low-level residual activity - may lurk in the centres of most large galaxies.
Velocity Dispersion in Small Systems of Galaxies
Authors: Karachentsev I. D.
Published: July 2016

During recent years the problem of the virial paradox has grown less acute for many galactic systems, especially for those having few members. As an example one can take the revision of virial mass-to-luminosity ratio, f = M/L, for de Vaucouleurs' groups performed by Materne and Tammann (1974). the reduction of the f-estimate is due to various reasons: an increase in accuracy in measuring radial velocities of galaxies, especially noticeable for 21-cm surveys of groups (Fisher and Tully 1975), regard for the sub-structure of systems of galaxies and improved exclusion of accidental members of groups (referred to here as “optical” members). Some very scattered systems proved to be low-contrast fluctuations of the expanding background, and not physical groups in their usual sense.
N-Body Simulations and the Value of ω
Authors: Gott J. Richard
Published: July 2016

We have recently completed a series of N-body simulations of galaxy clustering in an expanding universe (Aarseth, Gott and Turner 1977). the initial conditions and our results concerning galaxy clustering will be summarized by Sverre Aarseth at this meeting. in this paper I would like to tell about the implications of these models for the value of Ω = 8πGρO/3HO2 (where ρO is the present mean density of the universe and HO = 50 km s−1 Mpc−1 is Hubble's constant). in the standard Friedmann models with Λ = 0, Ω > 1 implies that the universe will eventually recollapse while Ω < 1 implies the expansion will continue forever. As discussed in Gott, Gunn, Schramm, and Tinsley (1974), there are a number of theoretical arguments to suggest that even the unseen matter in the universe is clustered the way the galaxies are so that virial mass determinations from groups and clusters and statistical virial theorem methods can provide good estimates of the mean mass density in the universe. We can utilize our N-body simulations to check the accuracy of these techniques.
The frequency of ring galaxies and the probability of their formation by collisions
Authors: Dostal V. , Metlov V.
Published: July 2016

A survey of ring galaxies which were discovered in 1960 by B. Vorontsov-Velyaminov has been carried out using the Morphological Catalogue of Galaxies. Clusters of galaxies were also included. Such galaxies without spiral arms constitute 0.7% of all galaxies down to 15m.0, and are 100 times less frequent than spiral galaxies. This percentage is the same for clusters, but there are fields where ring galaxies are 3–5 times more frequent than the average. the probability of nearly central chance collisions of galaxies as proposed by some theories has been calculated. It was assumed that a ring galaxy is formed from the encounter of a spiral galaxy with another galaxy if its mass or luminosity is not less than 1% of that of the principal galaxy. the minimum separation of their centres was taken to be less than 2.7 kpc, but the angles between the vectors of the relative velocity and the planes of galaxies were not restricted. the lifetime of the rings once they are formed was assumed to be 109 years and the distribution of the galactic velocities was calculated according to a Maxwellian distribution. the number of galaxies of given absolute magnitude per unit volume was taken from Holmberg (Stars and Stellar Systems, 9, 123). the curvature of the trajectories was taken into account. So conditions were chosen to be most favourable for nearly central collisions.
Radio Properties of Abell Clusters
Authors: Lari C. , Perola G.C.
Published: July 2016

Since the early 60's the association of some radio sources with rich clusters of galaxies was noted (Mills, 1960; van den Bergh, 1961) and subsequent investigations concentrated mostly on the radio properties of clusters in the Abell catalogue. This paper is confined to this subject, although one should bear in mind the importance of associations with other scales of clustering which do not appear as entries of that catalogue. in this paper we shall use HO = 100 km sec−1 and the radio power P in WHz−1 at 408 MHz.
Radio Observations of Clusters of Galaxies: The Tail Sources
Authors: Ekers R.D.
Published: July 2016

The “head-tail” class of radio galaxies (e.g. Ryle and Windram, 1968 and Miley et al., 1972) are of particular interest in the context of this symposium since they provide some of the clearest evidence for a diffuse medium.
Mathematical approach to the problem of clustering
Authors: Burczyk J. , Zieba A.
Published: July 2016

The mathematical theory of the description of the structure of point-sets in a plane or in space can be applied to the investigation of the distribution of different extragalactic objects. Mathematically we can define rigorously such ideas as cluster, nucleus of cluster, monoor polynuclear structure, background and so on. First we choose a critical distance that determines the scale on which we investigate the distribution of objects. the critical distance plays a similar role to the wavelength of radiation by means of which we investigate the internal structure of matter. It is obvious that the description is different for different critical distances. To obtain a complete picture we have to analyse the evolution of this description as the critical distance changes.
Extensions of the Wilson-Bappu Effect Among Very Luminous Stars
Authors: Stencel Robert E.
Published: July 2016

Twenty years ago, Wilson and Bappu (1957) published their observational correlation of MVand the logarithm of the full width at half maximum of the CaII K-line central emission for G, K and M stars. The technique was stated to have ± 0m.5 accuracy, while a tabulation of MV(K) by Wilson (1976) suggests the error may only be ± 0m.3. This accuracy makes the approach valuable for late-type supergiants since other methods suffer from comparable errors. However, for F through M supergiants (Ia, 0), circumstellar absorption obscures the chromospheric K-line core emission and excludes such objects from the Wilson-Bappu correlation. I report here on a new class of emission lines in late-type giant and supergiant spectra that exhibit MVcorrelated widths, yet are detectable among the brightest stars.
Ultraviolet Colors of Subdwarf O Stars
Authors: Wesselius Paul R.
Published: July 2016

The group of subdwarf O stars consisting of field stars and some central stars of old planetary nebulae does occupy an intresting place in the HR diagram. Greenstein and Sargent (1974) have tried to establish this place, and conclude that especially the hottest ones need ultraviolet data to improve the values of effective temperature and absolute luminosity.
Subluminous Stars in the HR Diagram
Authors: Dahn C. C. , Harrington R. S.
Published: July 2016

Eggen (1969) has defined a subluminous star “… as one that is fainter by at least a factor of 10 in visual luminosity than the main sequence stars of the same(U-V).” Implicit is the suggestion that single stars might exist in the region of the HR diagram between the subdwarfs and the normal degenerate sequence. While the evolutionary calculations of Chin and Stothers (1971) indicate that stars with masses <0.2 M⊙will pass through this region following the completion of nuclear burning, these models have not yet been confirmed. We summarize Naval Observatory astrometry and photometry as it pertains to the existence of such stars.