bluuebunny/crossref_metadata_2025 huggingface dataset:
What do binaries teach us about mass-loss from late-type stars?
Authors: Reimers Dieter
Published: June 2019

It is shown that the binary technique - a B star companion is used as a light source which probes the wind of the red giant primary - has yielded accurate mass-loss rates and wind velocities for 8 G to M (super) giants and (in some cases) estimates of wind temperature.

Eclipsing binary systems have in addition revealed that G and K supergiants possess extended chromospheres which could be detected outwards to ∼ 1 R* stellar radius) above the photospheres. Electron temperatures Te and hydrogen ionization ne/nH seem to increase with height up to at least 0.5 R* (ne/nH= 10−2, Te = 104 K at 0.5 R*), and the winds start to be accelerated at heights above ∼ 0.5 R*.

Mass-loss rates appear to increase steeper than linearly with L/g · R. It is shown that the observed mass-loss rates are consistent with stellar evolution constraints for both Pop. II and Pop I stars.
CO molecule in transition region between chromosphere and cool stellar wind: A new probe on the outer atmospheres of cool luminous stars
Authors: Tsuji T.
Published: June 2019

Presence of CO layer well separated from photosphere is confirmed and this revealed a presence of quasi-static turbulent transition layer in normal red (super)giant stars. This layer may be related to an outer part of the extended chromosphere and/or a cool part of the chromospheric inhomogeneity, and will play major role in stellar mass-loss.
Slow variability and circumstellar shells of red variable stars
Authors: Evans T. Lloyd
Published: June 2019

Infrared photometry shows that while all RV Tauri stars have circumstellar dust shells, the RVb stars with slow cyclic variations in mean light as well as the 30–100 day variations common to all RV stars have more hot dust close to the star (Lloyd Evans 1985). Many M giant stars which are variables of semiregular type also show long-period variations in the mean light (O'Connell 1933; Payne-Gaposchkin 1954), with a roughly constant ratio between the two periods. Payne-Gaposchkin (1954) found P2/P1 ~9.4 for red variables of type M and P2/P1 ~19.4 for stars of type F-K, most of which are FV Tauri stars. Re-analysis using the more extensive data available now indicates P2/P1 ~10 for the M giants and P2/P1 ~15 for the FV Tauri stars. The nature of the long-period variability is unknown (Wood 1975).
The circumstellar environment of L2 Puppis
Authors: Magalhaes Antonio Mario , Coyne George Vincent
Published: June 2019

Polarimetric observations of the red semi-regular variable L2 Puppis, obtained over a period of several years, confirm significant variations across the CaI 4226 line and several TiO bands. Together with published infra-red data, the observations point to a fundamental symmetry plane to which all variations with wavelength and time are related. The data are also consistent with a combination of photospheric effects, including a non-uniform distribution of calcium across the stellar disk, and scattering from grains in a cloud in which there is a systematic variation in grain size with distance to the star. Grain growth and dissipation, as evidenced by the observations, occur on a time scale of several years, in contrast to the optical variability time scale of months.
On the Origin of Kepler's Supernova Remnant
Authors: Bandiera R.
Published: June 2019

Aim of my poster is to show that Kepler's supernova progenitor was a massive star, rather than an old population object, as commonly accepted. The star was subject to strong mass loss, and the present remnant is due to the interaction of the blast wave with dense circumstellar matter
Model Atmospheres for X-ray Bursting Neutron Stars
Authors: London Richard A. , Taam Ronald E. , Howard W. Michael
Published: June 2019

Self consistent neutron star atmospheric models have been constructed which include the effects of Comptonization, free-free and bound-free absorption. It has been demonstrated that for parameters relevant to x-ray bursting neutron stars the atmosphere does not radiate like a blackbody during any phase of an x-ray burst. In particular, during the initial rise and final decline of the burst the temperature structure of the atmosphere is affected by backwarming associated with the high opacity due to free-free processes at low frequencies to an extent that the radiation spectrum is shifted to higher energies than a blackbody of the same effective temperature. On the other hand, near the peak of the burst, the opacity is more gray-like as the electron scattering opacity dominates; however, in this case thermalizaton of the radiation field occurs at such large optical depths (τ ∼ 5) that the spectral temperature is higher than the effective temperature. This result is found despite the importance of Comptonization in the thermalization process. Thus, the super Eddington fluxes implied by the spectral data alone are misleading and result from the improper use of the spectral temperature for the effective temperature. For neutron stars characterized by a soft equation of state and radiating near the Eddington effective temperature, fluxes obtained in this way could be overestimated by a factor of about 5.
Timescale for the Decay of Magnetic Fields of Pulsars
Authors: Krishnamohan S.
Published: June 2019

It is generally agreed that the magnetic fields of pulsars decay with the time. The previous estimates for the decay timescale range from 2Myr to < 10Myr based on the evolutionary tracks in the (P,P) diagram and the kinematics of pulsars. We make a new estimate, by using the ‘measured fields’ themselves, to be about 20Myr and show that the z-distribution of pulsars is consistent with the new estimate if the known dependence of velocities of pulsars on the magnetic moment is taken into account.
Neutron Star Interiors
Authors: Alcock Charles
Published: June 2019

The current status of the theory of neutron star interiors is reviewed. The various phases of matter that might exist are discussed and their relation to other areas of astrophysics briefly noted. Observational distinction between the models is not simply obtained; analysis of pulsar post-glitch relation, of neutron star precession and neutron star cooling are promising in this regard.
Classification Criteria and Databases
Authors: Stenholm Björn
Published: June 2019

In this review lecture the increase of fundamental data for planetary nebulae is shortly reflected. Special attention is given to the new general catalogue of galactic planetary nebulae, and selection criteria for the entries are summarised. Some information on planetary nebula data in the Magellanic Clouds is also given.
Planetary and Proto-Planetary Nebulae Which are Strong 25μm Emitters
Authors: Wolstencroft R.D. , Read M.A. , Scarrott S.M. , Lonsdale C.J. , Parker Q.A.
Published: June 2019

The IRAS Point Source Catalogue containing about 250,000 sources has yielded a large number of previously unknown planetary nebulae (PNe) and a smaller number of proto-planetary nebulae (PPNe). The spectral energy distributions for many of these objects peak at or close to 25μm. A program to optically identify sources in the complete IRAS Faint Source Database, which comprises about 750,000 sources, is currently under way (Wolstencroft et al. 1991), and in a related study Wolstencroft, Parker & Lonsdale are carrying out a spectroscopic survey of a small sample of the approximately 106,000 sources which either peak or are detected only at 25μm. So far spectra of 150 sources have been obtained: 3 of these sources are PNe and 1 is a PPNe. This suggests that this sample of 25μm emitters may be a rich source of new PNe and PPNe. In this note we discuss two of these four sources.
Non-LTE Spectra of Iron Group Elements for CSPN
Authors: Becker S.R. , Butler K.
Published: June 2019

UV spectra of CSPN are dominated by lines from ions of iron group elements. Recently we have developed a non-LTE model of the Fe V spectrum putting particular emphasis on this spectral region (Becker and Butler, 1992a). Lines of Ni IV and Ni V are major contributors to blends with the dominating Fe V lines. Meanwhile, non-LTE models for Ni IV, Ni V and Ni VI have been developed (Becker and Butler, 1992b) and the non-LTE model spectra composed of lines from all four ions can be compared to the observations.
Optical Imagery of NGC 6302
Authors: Bohigas Joaquín
Published: June 2019

Images with narrow band filters centred at the most significant emission lines, such as Hβ, Hα, [SII] 6717 and [SII] 6731, were taken to explore the physical conditions of NGC 6302. Observations were secured on May 1991 with the 2.0m telescope of the Observatorio Astronómico Nacional at San Pedro Mártir, B.C., Mexico, the f/7.5 secondary, and a 384 × 576 CCD chip. The most significant results are:

1.

Excitation mechanism. The image of the Hα/[SII] lines ratio reveals that photoionization and shocks are equally important throughout most of the object. Photoionization is dominant in the central region and a few isolated patches. Elongated structures pointing towards the central region can be identified with a shock impinging the wall of a bipolar cavity.

2.

Extinction. The image of the Hα/Hβ lines ratio shows that extinction changes over all distance scales. C(Hα) is nearly equal to 1.7 in the central region. It falls off very rapidly away from it, and at a distance of 10 arcsec it is approximately equal to 1.3. In the mean, Hα/Hβ is 1.25 times larger in the western lobe than in the eastern.

3.

Excitation. Different lines ratios, such as [SII] 6724/[SIII] 9069, [OIII] 5007/[OI] 6300 and Hel 5876/Hβ, indicate that excitation is larger in the eastern lobe. For instance, Hel 5876/Hβ ≃ 0.15 in the eastern lobe and ≃ 0.13 in the western region.

4.

Electron density was calculated from the [SII] 6717 and [SII] 6731 images. The density structure is very complex. Within the central region the highest density is found at both sides of the dark lane. No clear correlation exists between density and shock excited regions. Wave-like patterns can be recognized in the density image. These can be attributed to instabilities, sporadic ejections events and/or multiple shocks.
Point Symmetry in Planetary Nebulae
Authors: Corradi Romano L.M. , Schwarz Hugo E. , Stanghellini Letizia
Published: June 2019

We present narrow band images and spectra illustrating the morphological and kinematical characteristics of a new class of planetary nebulae. It consists of all those objects in the catalogue by Schwarz et al. (1992) whose morphology shows no other symmetries than point–reflection about the central source. This peculiar shape is often determined by pairs of ansae or blobs separated from the central body of the nebula. The kinematical data show both low (e.g. IC 4634) and high (He 2–186; Vexp > 135 km s−1) velocity outflows.
Evolution from the AGB: Variability
Authors: Sasselov Dimitar D.
Published: June 2019

Luminous low-mass stars of intermediate Teff – candidates for post-AGB transition objects to PNNi, are all expected to be pulsationally variable. Different modes and their combinations may be involved, leading to a variety of observed behaviour.
Space Distribution of Short Period Mira Variables
Authors: Hron J.
Published: June 2019

The group of short period Mira variables (periods less than 200 days) is thought to be a mixture of metal poor stars and disk stars. We have compiled JHKL photometry for 159 stars in this period range, the great majority of the data coming from new observations. The photometry is used to separate metal poor from disk stars, following Hron (1991, A&A 252, 583), and to define volume limited subsamples. Distances were derived from the K-magnitudes and the period/K-luminosity relationship.
A New Evolutionary Interpretation of the IRAS Two-Colour Diagram
Authors: García-Lario P. , Manchado A. , Pottasch S.R.
Published: June 2019

A new evolutionary interpretation of the sequence of colours observed in the IRAS two-colour diagram by AGB and post-AGB stars is given, which is capable of explaining the observational properties of both kind of objects. It is useful to define a parameter λ to define the position of a given star in this “infrared main sequence” (IRMS). Adopting

and from the analysis of the expansion velocities, mass loss rates and luminosities observed in a selected sample of non-variable OH/IR stars with no optical counterpart in the Galactic bulge as a function of λ, we conclude that the position in the IRAS two-colour diagram at which a star leaves the IRMS (λmax) only depends on the initial mass Mz of the progenitor star, so that only massive objects can reach the upper end of this sequence. The relation found is:

Expansion velocities increase with the initial mass while every point in the IRMS is found to be associated to a certain value of the mass loss rate. This model also predicts the evolution with time of the mass loss rate during the AGB as a function of the initial mass of the progenitor star, and confirms that most known planetary nebulae are the result of the evolution of considerably massive stars (between 2–3 solar masses) which means that the contribution of processed material to the interstellar medium is considerably higher than what theoretical models predict. Type I PNe are the result of the evolution of 3 — 5 M⊙ progenitors while progenitors with Mi ≤ 1.2 M⊙ probably do not give PNe. The model is also in agreement with the narrow distribution of core masses found in central stars of PNe and white dwarfs and with the usual expansion velocities found in OH/IR stars.
A Modelling of Expansion Velocities of Planetary Nebulae
Authors: Gesicki K. , Szczerba R.
Published: June 2019

Recently written model of photoionization structure of planetary nebula has been used to calculate the emissivities of different nebular lines. With these values the line profiles have been modelled. The profiles can be obtained for different size and position of the spectrograph slit on the nebula image. The prepared computer code allows for estimation of the expansion velocities (Vexp) in the way consistent with the methods used by observers, i.e. defined as the half-width of the line profile (when nebula is not resolved, “whole neb.” in the Figure) or defined as the half of the emission peaks separation (when the nebula can be resolved — “rectangle” in the Figure — and the line can be observed in the central part of the nebula). The real matter velocity at the radius where the observed surface brightness of Hβ falls below 20 % of the maximal value is shown for comparison (“model” in the Figure).
Excitation Class of Nebulae as an Evolution Criterion
Authors: Gurzadyan G.A. , Egikyan A.G.
Published: June 2019

A principally new, quantitative system of the classification of spectra of planetary nebulae is proposed. The excitation class of a nebula, p, is determined according to the relative intensities of emission lines, N1+N2/4686 HeII and N1+N2/Hβ. The excitation classes are obtained for 177 PN with known distances and sizes of all classes – low (p=1–3), middle (p=4–8) and high (p=9–12+). An empirical relationship between the excitation class p and the mean radius of the nebulae Rn is discovered – the largest sizes occur for highly excited nebulae, and the smallest for low excitation ones. This relationship as well as excitation class p, as an independent parameter admit an evolutionary interpretation (Gurzadyan, Egikyan 1991).
The Present Status of Preparing the New Reduction of the Past Astrometric Observations to Obtain the Earth Orientation Parameters in the Hipparcos Reference System
Authors: Vondrák J. , Ron C.
Published: June 2019

The IAU Working group on Earth rotation in the Hipparcos reference frame, set up by IAU Commission 19 in 1988, is presently preparing the algorithms and collecting the data obtained by optical astrometry since the beginning of the century. The main idea is to use the observations of individual stars rather than group results, all recalculated in the unique system of astronomical constants and algorithms. The final solution will be referred to the celestial reference frame realized by the Hipparcos star catalog presently under preparation. All known geophysical influences (as e.g. solid and oceanic Earth tides or plate tectonic movements) will be included into the model. In addition to traditional Earth rotation parameters (polar motion, universal time), also the pole offset components in the celestial reference frame will be solved for, as well as other relevant parameters (systematic seasonal deviations of the individual stations, instrumental constants etc.). The present status of the solution and the time evolution of its expected accuracy are described.
On the Precision of Star Positions Observation Made with the Pulkovo HMC.
Authors: Kirian T. , Pinigin G.
Published: June 2019

After the automation of the Pulkovo HMC two catalogs of Positions of 1081 Stars from FK5B, FK4S, FKFS and RRS were observed. Every star was observed more than three times during the period from March 1988 to May 1990. The internal error of a single observation of FK5 stars was estimated as 0.S015(Sec-Z)0.6, 0″.16 (Sec-Z)0.9 in α and δ. A comparison of the declination of FK5B Stars observed with HMC with those of Bordeaux 86, CAMC 86 and PMC 86÷88 shows the Δδδ differences of the order of 0″.1 in the declination zone 40°÷60°.
The Sea Level Change of the Tropical Pacific and the Rotation of the Earth
Authors: Zheng Dawei , Chen Gang
Published: June 2019

About 30-year time series of the length of day (LOD) and the Pacific sea level are analysed in the paper. The close correlation between Earth rotation and sea level is discussed. Dynamical analysis of the angular momentum of tropical Pacific Ocean and solid Earth shows that the sea level changes of eastern and western Pacific lead the LOD interannual change in phases of 1 and 2 months respectively. The tropical Pacific effect accounts for about 31% in LOD change and is even more evident during El Nino events. Changes of the Earth rotation also cause changes in the oceanic mass distribution.
Influence of Ephemeris Uncertainties and Relativity Modeling on Lunar Laser Ranging Data Analysis
Authors: Jin Wenjing , Xu Huaguan , Nie Zhaoming , Li Jinling
Published: June 2019

In this paper authors pointed out that the root mean square of post-residual is two or three times larger than that of normal points. It is mainly due to the ephemeris uncertainties, i.e. the uncertainties of obliquity of the ecliptic and equinox and the inaccurary of lunar love numbers adopted. At present, with exception of the corrections of ocean tide and pole tide the theoretical modeling such as earth solid tide, lunar tide, plate motion and the relativity modeling, especially the space curvature caused by the earth, have been considered to match the present observing precision in the magnitude of centimeter. The equivalent of relativity modeling used in geocentric or barycentric reference frame is further described.
Completion of the FK5 Extension and a Preliminary Investigation of the FK5 System
Authors: Schwan H.
Published: June 2019

The construction of the Fifth Fundamental Catalogue (FK5) is shortly described with emphasis on the system of the Basic FK5 and on the completion of the FK5 Extension. New observations have revealed systematic errors mainly in the declination system of the FK5 and in the right ascensions south of −50°. Comparisons of the new observations with the Basic FK5 and the FK5 Extension (made separately for the bright and faint stars) have shown that the FK5 Extension is essentially on the system of the Basic FK5.
Sur la perte de masse et les processus de freinage de la rotation
Authors: Schatzman E.
Published: June 2019

Deux mécanismes importants de perte de masse s'accompagnent d'une grande perte de moment angulaire:

1°

une étoile en contraction et en rotation peut perdre de la matière le long de son équateur. Sa vitesse de rotation est alors telle qu'à l'équateur la gravité et la force centrifuge s'éuilibrent;

2°

l'étoile peut perdre de la matière par des processus éruptifs. La perte de moment angulaire est d'un ordre de grandeur très différent suivant que la matière éjectée est ou non guidée par les lignes de force d'un champ magnétique.
Boxy Isophotes and Dust Lanes in Bright Virgo Ellipticals
Authors: Möllenhoff C. , Bender R.
Published: June 2019

The CCD camera of the Landessternwarte Heidelberg was used at the 1.2 m Calar Alto Telescope for a V, R, I - survey of ~70 dusty and non-dusty elliptical galaxies. We report here about morphological studies of ten bright elliptical galacxies in the Virgo cluster. After the usual CCD data reduction the following procedures were carried through:

1. The CCD-frames were filtered and centered to an accuracy of ~ 0. 2 pixels. By division we obtained V-R, V-I, R-I color index images which allow to separate dust absorption and gaseous emission from the stellar distribution. Five of the 1 0 bright Virgo ellipticals evidently show dust/gas, two other objects have weak features. The dust lanes in NGC k26 (cf. Fig. l), NGC 4365 and NGC 4552 were detected for the first time. A dust lane must be visible in all three color index frames in order to avoid fake identifications.

2. The isophotes in all three colors were fitted by least square ellipses. From these fits we obtained in dependence from the radius: color profiles, color index profiles, ellipticity profiles, isophote twists (cf. Fig. 2). The deviations of the isophotes from ideal ellipses were studied by a Fourier series analysis. The fourth coefficient is the main indicator for such deviations. Six of ten galaxies show box-shaped isophotes of an amount between 0. 3 % and 1. 5 % of the semi major axis (cf. Fig. 3) 5 two galaxies show disc components (0. 8 1.5 %), only one galaxy is a perfect elliptical up to an error of ±0.2 %. The deviations are equal in all three colors and therefore are not produced by dust.
Are Cooling Flows Governing E-Galaxy Evolution?
Authors: Valentijn Edwin A.
Published: June 2019

Gas accretion of intra cluster gas into the potential well of giant elliptical or cD galaxies can provide the material for both nuclear non-thermal activity and continuous, probably low mass, star formation (Fabian et al. 1982, Valentijn and Bijleveld 1983). In a few dozen cases it has been observed in the nearby universe that the hydrostatic equilibrium of X-ray emitting gaseous atmospheres around cD galaxies is disturbed by the thermal bremsstrahlung cooling in the central high density area, leading to an inflow of gas into the centrally located gE or cD galaxy (“cooling flows”, Jones and Forman 1984). This thermal instability is different from those studied in models of early galaxy formation (Gunn and Gott 1972, Rees and Ostriker 1972) only because of the assumed self-gravitation of the collapsing gas in the galaxy formation scenarios. If however, during early galaxy formation the collapsing gas is accreted by a pre-existing dark potential well, then the processes of early galaxy formation and the observed present epoch cooling flows are likely to be intimately related to each other. The cooling accretion flows could then lead to the original formation of the visible object, and subsequently govern its evolution through the fuelling of star formation and nuclear non-thermal activity.
An Investigation of the Radial Dependence of the Galaxy Luminosity Function in Abell Clusters
Authors: Lugger Phyllis M
Published: June 2019

The luminosity functions of inner and outer regions of six Abell clusters (A569, A1656, A2147, A2151, A2199, and A2634) were compared. These clusters have a single, reasonably symmetric central concentration of galaxies within the central Mpc. For three other clusters with irregular spatial distributions of galaxies (A779, A1367, and A2197) luminosity functions for high and low density regions were compared. For three of the clusters in the first group (A1656, A2147, and A2199) there is a deficit of bright galaxies, according to the Kolmogorov-Smirnov and Wilcoxon rank-sum nonparametric tests, in a region of radius 0.5 Mpc about the cluster center compared to a concentric annular region with bounds of 0.5 and 1.0 Mpc.
On the Luminosity Function of Elliptical Galaxies
Authors: Popov V.S.
Published: June 2019

Originally the luminosity function of galaxies was derived by E. Hubble (1936). Later studies are by Holmberg (1950), Zwicky (1957, 1964), Kiang (1961), Neyman and Scott (1962), Van den Bergh (1961), Pskovsky (1965), Nezhinsky and Osipkov (1967, 1969), Genkina (1969), Popov (1980), Tammann (1984), and others.
Spectrophotometry of Shell Galaxies
Authors: Pence W.D.
Published: June 2019

Low dispersion spectra of two shell galaxies, NGC 3923 and NGC 3051, have been obtained covering the 5300Å to 10000Å spectral range. These long-slit spectra go through the nucleus of each galaxy and also through 12 shells in NGC 3923 and through 3 shells in NGC 3051. the main results are:

1) In NGC 3051 the surface brightness of the 2 inner shells is nearly constant with radius. These plateaus of luminosity have very abrupt outer cutoffs but have no detectable inner limits.
Self-consistent Oblate-Spheroid Models
Authors: Bishop J.L.
Published: June 2019

A method for the construction of models of axisymmetric galaxies is presented. in this formulation we determine the distribution function corresponding to a given gravitational potential and the associated mass density distribution. Although the realization of the model is numerical, the underlying theory is analytic and exact. This method allows us to construct a wide range of models without having to use linear programming and a large amount of computer time. Here we present the results from the application of this method to the “perfect” oblate-spheroid mass model. A large class of valid self-consistent distribution functions which depend on three isolating integrals of the motion is found. the kinematics of many models are consistent with those observed for elliptical galaxies. in particular, models generated by this formulation are in agreement with the observed values of the ratio of the maximum projected rotational velocity to the velocity dispersion along the line of sight versus ellipticity.
Box Models without Cylindrical Rotation
Authors: Petrou Maria
Published: June 2019

We describe here a way of constructing models for box–shaped dynamical systems without cylindrical rotation. We argue that such models may arise as a result of the external heating of a disk.
Solution of the Problem of Stability of a Stellar System With Emden's Density Law and a Spherical Distribution of Velocities
Authors: Antonov V. A.
Published: June 2019

Applying a criterion previously derived by the author, the stability of stellar systems with an isotropic distribution velocity distribution and Emden's polytropic density law is demonstrated for the exponent n = 3/2.
Molecular Line Observations of the Galactic Center Region
Authors: Stark A. A. , Bally J. , Wilson R. W. , Pound M. W.
Published: June 2019

A decade of galactic center observations at the Crawford Hill 7 m antenna is summarized. The galactic center region contains several hundred high-mass, high-density molecular clouds with physical properties very different from clouds in the outer galactic disk. There is also a considerable amount of molecular gas not bound into clouds, but sheared by differential rotation into a molecular inter-cloud medium not seen elsewhere in the Galaxy. These observations can be explained by a combination of the tidal density limit and the virial theorem. The distribution of emission on the sky and in velocity suggests that most of the dense gas is confined to a 500 pc long ridge of emission which may be a dust lane along the central bar.
Hat Creek HCO+ and HCN Observations of Sgr A
Authors: Wright M.C.H. , Marr J. M. , Backer D. C.
Published: June 2019

We report aperture synthesis observations of the HCO+ and HCN J=1–0 molecular lines towards the Galactic center. These data complement existing HCN data and trace a dense molecular ring surrounding the ionized central 2 pc of the Galaxy. The new data are consistent with the model of a clumpy, almost complete ring which is inclined to the line of sight at 50 to 75 degrees. The same structure is seen in HCO+ and in HCN with the exception of an HCN feature at 60 to 100 km/s in the western part of the ring, which is not detected in HCO+ emission. The HCN and HCO+ are collisionally excited in clumps with densities around 10 cm and volume filling factor 1/3 to 1/30. H13 CN emission from the ring was detected at about 1/7 of the intensity of the HCN; the latter is optically thick and is mapping a combination of surface density and excitation temperature. The HCO+ emission shows deep absorption features associated with galactic structure along the line of sight. Absorption features corresponding to the 3 kpc arm, the inner disk and an expanding ring at −195 km/s can be seen in absorption against the Sgr A radio continuum.
Annihilation Radiation and Gamma-Ray Continuum from the Galactic Center Region
Authors: Lingenfelter Richard E. , Ramaty Reuven
Published: June 2019

Observations of the time-dependent, electron-positron annihilation line radiation and gamma-ray continuum emission from the region of the Galactic Center show that there are two components to the annihilation line emission: a variable, compact source at or near the Galactic Center, and a steady, diffuse interstellar distribution. We suggest that the annihilating positrons in the compact source, observed from 1977 through 1979, result from photon-photon pair production, most likely around an accreting black hole, and that the annihilating, interstellar positrons result from the decay of radionuclei produced by thermonuclear burning in supernovae.
Search for slow light variations of red-dwarf stars
Authors: Bondar N.I.
Published: June 2019

The results of a search for slow light variations of 13 K2e-M4.5e dwarf stars using the Sternberg Institute plate collection are presented. These variations are discovered for PZ Mon and V577 Mon, confirmed for BY Dra and BD+26°730 and suspected for V639 Her and V654 Her.
Flare stars as age indicators in open clusters
Authors: Pigatto L.
Published: June 2019

A new set of isochrones derived from overshooting evolutionary models, allows one to give a homogeneous age determination for open clusters with solar chemical composition and in a range of age 4 107 ÷ 1.5 109 yr. In this context is derived an empirical new age calibration - absolute magnitude of the supposed brightest flare star in a cluster versus log age -. The evolutionary implication in finding or not finding flare stars in candidate open clusters is also examined.
Recent results on polarization of T Tauri stars and other young stellar objects
Authors: Bastien Pierre , Ménard François
Published: June 2019

Recent results on observations and models of polarization of T Tauri stars (TTS) and other young stellar objects (YSO's) are presented. In particular, the difference in polarization properties between the classical T Tauri stars (CTTS) and the weak-line T Tauri stars (WTTS) is made. A correlation between polarization and rotation period is searched for but not found. Observations of polarization maps for many young stars are considered. Two types of models have been proposed to explain these observations. Current evidence favors single and multiple scattering in flattened, optically thick, structures, i.e. disks, around many TTS. In particular, the size of the optically thick part of the disks, and their inclination to our line of sight can determined for published polarization maps.
Survey observations of emission line stars and Herbig-Haro objects at the kiso observatory
Authors: Ishida K.
Published: June 2019

Summary of the works on emission line stars and Herbig-Haro objects done by visiting astronomers at Kiso is presented.
Far Infrared emission from post-T-Tauri stars
Authors: Tsikoudi Vassiliki
Published: June 2019

We have investigated a large sample of faint Post-T-Tauri stars located far from dark cloud complexes, for far-infrared emission and infrared excess, using the IRAS data-base. ~12% of the stars studied here were detected by IRAS at 12 μm. Their 12 μm luminosities L12 are in the range of 4×1030 − 6×1033 erg/sec and correlate well with the stars, bolometric luminosities (Lbol).

IRAS has detected emission from the photospheres of the stars studied here and for a few of them it may have observed far-IR excess.
Searching for Biomolecules with the ATCA: First Results
Authors: Hunt-Cunningham Maria R. , Jones Paul A.
Published: June 2019

A search for biologically significant molecules in the interstellar medium (ISM) is currently being undertaken with the Australia Telescope Compact Array (ATCA) of the CSIRO Australia Telescope National Facility (ATNF) at millimetre wavelengths. The search includes several chiral molecules, and glycine, the simplest amino acid. Some first results from this search are presented here.
A Spectral Survey of Molecules in the Orion Nebula from 455 – 507 GHz: An Inventory of Prebiotic Chemistry
Authors: White Glenn J. , Araki M. , Greaves J. S. , Ohishi M.
Published: June 2019

The results of a submillimetre wavelength spectral line survey between 455.1 – 507.4 GHz of the Orion-KL hot cloud core are reported. 254 lines were detected, and are associated with 30 different molecular species or their isotopomeric variants. Apart from the abundant diatomic rotors such as CO and CS, the spectrum is dominated by SO, SO2 and CH3OH and large organic molecules such as (CH3)2O, CH3CN, C2H3CN, C2H5CN and HCOOCH3 which make up ∼ 72% of the total number of lines; unidentified lines ∼ 13%; and other lines the remaining ∼ 15% of the total. Rotational temperatures and column densities derived using standard rotation diagram analysis techniques were found to range from 70 – 600 K, and 1014 – 1017cm2 respectively.
Building Planets with Dusty Gas
Authors: Maddison S. T. , Humble R. J. , Murray J. R.
Published: June 2019

We have developed a new numerical technique for simulating dusty-gas flows. Our code incorporates gas hydrodynamics, self-gravity and dust drag to follow the dynamical evolution of a dusty-gas medium. We have incorporated several descriptions for the drag between gas and dust phases and can model flows with submillimetre, centimetre and metre size “dust”. We present calculations run on the APAC1 supercomputer following the evolution of the dust distribution in the pre-solar nebula.
Central Metabolic Pathways of Hyperthermophiles: Important Clues on how Metabolism Gives Rise to Life
Authors: Ronimus R. S. , Morgan H. W.
Published: June 2019

Vital clues on life's origins within the galaxy exist here on present day Earth. Life is currently divided into the three domains Bacteria, Archaea and Eukarya based on the phylogeny of small ribosomal subunit RNA (16S/18S) gene sequences. The domains are presumed to share a “last universal common ancestor” (LUCA). Hyperthermophilic bacteria and archaea, which are able to thrive at 80°C or higher, dominate the bottom of the tree of life and are thus suggested to be the least evolved, or most “ancient”. Geochemical data indicates that life first appeared on Earth approximately 3.8 billion years ago in a hot environment. Due to these considerations, hyperthermophiles represent the most appropriate microorganisms to investigate the origins of metabolism. The central biochemical pathway of gluconeogenesis/glycolysis (the Embden-Meyerhof pathway) which produces six carbon sugars from three carbon compounds is present in all organisms and can provide important hints concerning the early development of metabolism. Significantly, there are a number of striking deviations from the textbook canonical reaction sequence that are found, particularly in hyperthermophilic archaea. In this paper the phylogenetic istribution of enzymes of the pathway is detailed; overall, the distribution pattern provides strong evidence for the pathway to have developed from the bottom-up.
The Potential for Archaeology Within and Beyond the Habitable Zones (HZ) of the Milky Way
Authors: Campbell John B.
Published: June 2019

As archaeology is established on Earth and we are actively exploring the Solar System and beyond, there is the potential to develop a number of forms of exo-archaeology. The archaeology of the things intelligent species do in theory could be practised anywhere, provided one can detect the evidence. Sites are being created by us elsewhere within our star's habitable zone (HZ), namely on the Moon and Mars, and at least molecular traces of human-created probes are being left beyond the HZ (Venus, Jupiter etc.). The successful detection of extrasolar planets and the possible identification of HZs round other stars raise the possibility for the development of extrasolar archaeology, at least initially by remote sensing techniques. Within the Milky Way the main region to investigate is the galactic habitable zone (GHZ), though there could be archaeological traces of technological behaviours beyond it.
Philosophy of classification for WN stars
Authors: Smith Lindsey F. , Shara Michael M. , Moffat Anthony F.J.
Published: June 2019

The unsatisfactory present state of the classification system for WN stars is summarised and the three dimensions of a new system are presented and justified.
[Wolf-Rayet]-type central stars of planetary nebulae
Authors: Górny S.K. , Acker A. , Stasińska G. , Stenholm B. , Tylenda R.
Published: June 2019

A number of central stars of planetary nebulae (CSPN) show emission lines in their spectra. Among them about 50 have been classified as [Wolf-Rayet] type (Tylenda et al. 1993). In spite of the fact that these stars probably have masses below 1 M⊙ and luminosities < 104 L⊙ their spectra show emission bands very similar to those of much more massive and luminous Population I Wolf-Rayet stars. We present some preliminary results of an extensive investigation of the [WR]-type CSPN based on the spectroscopic survey described in the Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (Acker et al. 1992).
Wolf-Rayet star variability and wind inhomogeneities
Authors: Brown John C. , Richardson Lorna L.
Published: June 2019

The wind structure diagnostic possibilities offered by combined study of photo-, spectro-, and polari-metric variability are discussed using data from the Montreal group. These demand the presence in the wind of localised density inhomogeneities and in particular of large ‘blobs’ denser than the ‘mean’ wind and put bounds on the size, mass, and density of individual blobs and their distributions, with implications for theories of blob formation. Blobs responsible for polarimetric variability must be present at the stellar surface rather than forming in the wind, and the relation of this to spectrometric indications that blobs are only detectable at several stellar radii is discussed.
Spectroscopic observations of the long-period Wolf-Rayet binaries HD 193793 and HD 192641
Authors: Annuk K.
Published: June 2019

New medium—resolution spectroscopic observations of two long—period WR binaries have been obtained using the 1.5 m telescope at the Tartu Astrophysical Observatory. The binarity of these systems is confirmed and orbital parameters are determined.
Wind-wind collision effects in close massive WR+O binaries
Authors: Marchenko S.V.
Published: June 2019

A detailed description of the wind-wind collision (WWC) zones in the Wolf-Rayet binaries V444 Cyg (WN5+O6III-V, P = 4.21 d) and CX Cep (WN5+O5V, P = 2.13 d) is presented. In V444 Cyg, parameters of the WWC zone can be derived from variations of HeI line profiles. There is some evidence for a highly unstable character of the WWC zone. In CX Cep, the complicated dependence of equivalent widths for emission lines of different ionization potential on orbital phase can be explained by a combination of several factors, e.g., (a) additional ionization from the bow shock region; (b) reheating of the WR wind by the O-star companion; and (c) an emission component arising in the WWC region. Some preliminary indications of WWC are revealed in the WR+OB system CQ Cep (WN7+O9I-II?) with the shortest known orbital period: P = 1.64 d.
Simulations of colliding winds in 3 dimensions
Authors: Walder Rolf
Published: June 2019

The significance of 3D effects in simulating colliding winds in WR binaries is demonstrated for the examples V444 Cyg, HD 193793 and γ Vel. The effects decrease with increasing separation of the stars. A comparison with symbiotic systems is drawn and a simulation of the symbiotic system EG And is presented.
Spectropolarimetric monitoring of WR140
Authors: Schulte-Ladbeck R.E. , Nordsieck K. H. , Bjorkman K. S. , Meade M. R. , Babler B. L.
Published: June 2019

We report on eight years of spectropolarimetric monitoring of the WR140 binary. The broad-band linear polarization decreased systematically after the 1985 periastron passage. By 1991, it settled to a constant value at which it has remained through the 1993 periastron passage. We do not detect, in data taken after 1989, a line-effect in He II Λ4686. This suggests either that the continuum and the line emission scatter at the same region, or that any intrinsic polarization has been below our detection limit. We conclude that the presently observed polarization of WR140 is consistent with interstellar foreground polarization.
Line profile variations in WR + collapsed companion systems
Authors: Koenigsberger Gloria
Published: June 2019

The existence of Wolf-Rayet binary systems containing a collapsed companion is predicted on evolutionary grounds. However, because of the absence of strong X-ray emission and the difficulty in obtaining consistent periodicities from the observed variations, none of the “classical” WR stars has been shown to be a WR+cc system. A discussion is presented of the line-profile variations which are predicted to occur on orbital timescales due to the interaction of the WR wind with the cc. We note the importance of numerical simulations of the flow structure of the WR wind in the vicinity of a collapsed companion for deriving diagnostic tools for the presence of a cc in a WR system.
The Determination of Cosmological Parameters
Authors: Longair Malcolm S.
Published: June 2019

The case is made that the 21st century will be the epoch of precision cosmology. It is realistic to expect that many of the standard cosmological parameters will be determined with high precision. This will require detailed and convincing understanding of the astrophysics of the objects used in the determinations.
The Hubble Space Telescope H0 Key Project
Authors: Freedman Wendy L. , Kennicutt Robert C. , Mould Jeremy R. , Madore Barry F.
Published: June 2019

As this conference has attested to, cosmology is a rapidly maturing field, currently experiencing a very healthy and vigorous confrontation between theory and experiment. This rapid progress in many different areas of cosmology has not removed the longstanding interest in measuring many of the fundamental cosmological parameters - rather, the increasingly detailed predictions of current theory highlight the critical importance of independently, accurately measuring the cosmological parameters which define the basic model for the dynamical evolution of the Universe. I present here the final results of the Hubble Space Telescope (HST) Key Project to measure the Hubble constant, summarizing our method, the results and the uncertainties. The Key Project results are based on a Cepheid calibration of several secondary distance methods applied over the range of about 60 to 400 Mpc. Based on the Key Project Cepheid calibration and its application to five secondary methods (type Ia supernovae, the Tully-Fisher relation, surface brightness fluctuations, type II supernovae, and the fundamental plane for elliptical galaxies), a combined value of H0 = 72 ± 8 km/sec/Mpc is obtained. Comparing to current estimates of the ages of Galactic globular clusters, an age conflict is avoided for this high a value of H0 if we live in a Λ-dominated (or other form of dark energy) universe.
FRIIb Radio Galaxies, Cosmology, and Quintessence
Authors: Daly Ruth A. , Guerra Erick J.
Published: June 2019

FRIIb radio galaxies can be used as modified standard yardsticks to determine global cosmological parameters; the method is analogous to the use of supernovae type Ia as modified standard candles. FRIIb radio galaxies are observed to very high-redshift; the sources discussed here are fairly evenly distributed in redshift, with redshifts between zero and two. The sources can be used to determine the coordinate distance to high-redshift sources, and thus can constrain global cosmological parameters (just like the use of supernova type Ia to determine the coordinate distance, or luminosity distance, to high-redshift sources). Current constraints on global cosmological parameters and on quintessence obtained using FRIIb radio galaxies are presented.
The Large Scale Structure Peak as a Comoving Standard Ruler
Authors: Roukema Boudewijn F. , Mamon Gary A.
Published: June 2019

Estimates of the curvature parameters Ω0 (density parameter) and Δ0 (cosmological constant) can be made geometrically by use of either a standard candle or a standard ruler. Just as supernovae of Type Ia appear to provide a good empirical standard candle, it now appears observationally justified to use the peak in the power spectrum of density perturbations at L ≍ 130±10h-1 Mpc as an empirical standard rod. It will be shown that voids of this size are traced by quasars in a homogeneous catalogue near the South Galactic Pole at z ˜ 2 and that the large scale structure peak of the catalogue constrains the value of Ω0 to 0.1 < Ω0 < 0.45 (68% confidence), independently of Δ0. Combination with the supernovae Ia data is sufficient to show that the observable Universe is almost flat. In other words, the combination of a standard ruler and a standard candle detected in two presently available data sets is sufficient to show that the Universe is nearly flat, independently of any microwave background data or any other data analyses.
Beyond FIRST and Planck
Authors: Griffin Matt.
Published: June 2019

Prospects for future satellite missions, operating in the FIR-mm wavelength region, to study the polarisation of the cosmic background radiation (CBR) and to carry out imaging and spectroscopy of high-redshift galaxies, are discussed. Full characterisation of the CBR polarisation offers the possibility of determining the energy scale of inflation and constraining the form of the inflaton potential. Current technology in FIR imaging and spectroscopy falls well short of matching capabilities in the optical/UV and the mm regions. Filling this gap is important to allow detailed examination of the physics and evolution of high-redshift galaxies, and will be possible with future FIR observatories which are now being studied.
Polarization Signatures of Clusters in the Microwave Background
Authors: Challinor Anthony.
Published: June 2019

Compton scattering of photons from ionised gas in galaxy clusters along the line of sight leaves an imprint in the polarization of the cosmic microwave background. We investigate this process taking account of the effects of relativistic electron velocity dispersion and primordial anisotropy on the frequency spectrum of the generated polarization. We also discuss the prospects of detecting such effects with the Planck survey.
Two-point Correlation Function and Power Spectrum at Very Large Scales
Authors: Deng Z.-G. , Xia X.-Y.
Published: June 2019

Subsamples of galaxies with different morphological types have been sorted out from Stromlo-APM redshift survey. Two-point correlation function for each subsample has been calculated. The two-point correlation functions for all subsamples show very large scale fluctuation. We show that the two-point correlation function with fluctuation could be fitted by a modified power spectrum with power excess at wave number comparable to the scale of the fluctuation.