bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature Fluctuations in PN
Authors: Gruenwald Ruth , Viegas Sueli M.
Published: June 2019

For planetary nebulae, empirical abundances can be obtained from the observed emission-lines as long as the electron density, the electron temperature, and the ionization corrections factor are determined. However, due to temperature fluctuations in the emitting gas, the evaluation of the temperature from the observational data is strongly dependent on the method used. The temperature fluctuation is usually characterized by the mean square temperature fluctuation, t2 (Peimbert and Costero, 1969 — PC).
M4—18: The Low Excitation PN Around a WC11 Star
Authors: Surendiranath R. , Rao N. Kameswara
Published: June 2019

A photoionization model is presented for M4–18. The model includes the presence of dust mixed with gas. The model shows sulphur and nitrogen are underabundant (relative to solar) and partially succeeds in explaining the observed IR excess.
A Symmetric Jet-Like Structure in the Planetary Nebula FG 1
Authors: López J.A. , Tapia M. , Roth M.
Published: June 2019

Fg 1 (He 2–66) is a southern planetary nebula that presents an elliptical shape. Deep CCD imaging and long-slit spectroscopy have been obtained at Las Campanas Observatory of this object. The images were obtained in the light of Hα+[NII], [SII] λλ6716,6731, HeII λ4686 and in the broad-band Rgunn filter. The spectra were obtained oriented N-S, P.A. 90°, and P.A. 85°. The instrumental combination yields a spectral resolution of ∼ 2 Å FWHM, covering a spectral range ≃ λλ 6290–6805 Å.
CCD Imaging of Planetary Nebula Halos
Authors: Kwitter K.B. , Chu Y.-H. , Downes R.A.
Published: June 2019

We have obtained deep CCD images of 14 PN to search for and examine faint halos. These images were obtained with Hβ, [OIII], Hα, and [NII] narrowband interference filters on the Burrell Schmidt at Kitt Peak. Table 1 summarizes the observations. We have found interesting features around NGC 1360, NGC 3587 (The Owl), and NGC 6853 (The Dumbbell), and we have obtained new images of the very faint outer halo of NGC 7293 (The Helix). Two CCDs were used: TI6, an 800×800 chip, with 1.45″ /pix and a 19.3 arcmin square field., and ST2K, a 2048×2048 chip, of which only 1200×1200 pixels were read out, yielding 2.07″ /pix and a 40 arcmin square field.
History of the Light Curves and Molecular Maser Emission of the Miras U Ori and R Leo
Authors: Andronov I. L. , Kudashkina L. S. , Rudnitskij G. M.
Published: June 2019

We have collected all the available data on light curves, OH, H2O and SiO maser observations for a sample of Mira-type variables. We consider in detail the data on two stars, U Ori and R Leo. There is a net correlation between optical and radio line variations for all the three molecular species in these stars. More pronounced maser flares seem to follow brighter-than-average visual maxima of the stars. We discuss also the drastic changes in the type of the OH maser radio emission which happened in these stars some years ago. Implications for the mechanisms of maser pumping and the evolutionary status of these stars (probably undergoing the helium flash) are discussed.
Complex Motions in Planetary Nebulae
Authors: Icke Vincent
Published: June 2019

I have made an extensive series of numerical simulations of aspherical PNs. This interacting-winds model consists of a point source of fast tenuous gas embedded in a flattened cloud of dense slow gas which is two-dimensional and cylindrically symmetric. I used a hydrocode specially designed to handle the extremely large gradients between the winds to second order accuracy. The outer shock shapes correspond very well to my analytic predictions. This shock may form cusps which compress the gas to form two rings on opposite sides of the equatorial plane.
Influence of the Stellar Winds on the Post-AGB Evolution
Authors: Szczerba R.
Published: June 2019

Modelling of evolution of dusty shells around post-AGB star of 0.598 M⊙ mass has been performed by means of the Yorke's hydrodynamical code. In this code dust and gas are treated as two separate components coupled by friction, and the spectral appearance of the model is computed by solving the angle and frequency dependent continuum radiation transfer problem. Calculations were carried out for dust composed of silicate grains. The emergent spectrum of the model has been convolved with the IRAS photometric band profiles to construct theoretical tracks on the IRAS two-color diagram.
A Very Rapid-Evolving Young Planetary Nebula
Authors: Manchado A. , García-Lario P. , Sahu K.C. , Pottasch S.R.
Published: June 2019

During a time interval of only 2 years, a sudden change has been detected in the emission line spectrum of a young planetary nebula IRAS 0656 2-0337, whose nature has been recently discussed by several authors, was firstly observed in December 1987 at La Silla (Chile) and in October 1988 at La Palma (Spain), showing only the Balmer lines in emission. A third spectrum, obtained at La Silla during February 1990, shows a quite different appearance, with forbidden emission lines typical of a planetary nebula. The electronic density is very high, and there is a high infrared excess too. An expansion velocity of 45 km s−1 has been estimated. It is shown that the effective temperature of the central star has significantly increased over this period of time. This is consistent with the evolution of a massive progenitor in the post-AGB phase, with L = 7000L⊙ at D = 4 kpc, in which the ionization of the neutral envelope, detected in CO, is now taking place.
The Peculiar Light Variation of the Planetary Nebula NGC 2346
Authors: Hao Xiang-Liang
Published: June 2019

Planetary nebula NGC 2346 is a well know butterfly bipolar nebula and the central star (AGK3–O°965) is known to be a spectroscopic binary with a period of about 16 days(1). This object has been observed frequently and no bright variations were noticed from at least 1899 to 1981 Nov(2). But in 1981 an unexpected large amplitude eclipse light variations were observed by Kohoutek(3). Since then a lot of observations have been reported by many authors. They have revealed that the central star V651 Mon showed fast and complex light variations due to eclipse and the amplitudes of the eclipse varied rapidly.
Influence of the Stellar Winds on the Evolution of the Planetary Nebula Nuclei
Authors: Górny S.K.
Published: June 2019

A grid of homogeneous models of evolution of hydrogen burning planetary nebulae nuclei, assuming different stellar winds and the zero points for the post-AGB evolution, have been constructed from original Schönberners tracks. Following a simplified line-driven wind theory the mass loss rate has been adopted to be
ROSAT Studies of the Composition and Structure of DA White Dwarf Atmospheres
Authors: Diamond C.J. , Barstow M.A. , Sansom A.E. , Marsh M.C. , Rosen S.R. , Fleming T.A. , Koester D. , Finley D.S. , Holberg J.B. , Kidder K.
Published: June 2019

We have made a detailed study of a sample of 28 hot DA white dwarfs detected in the ROSAT EUV and soft X-ray all-sky-survey.
Chemical Abundances in Galactic Bulge Pn
Authors: Walton N.A. , Barlow M.J. , Clegg R.E.S.
Published: June 2019

We present abundance determinations, in particular of carbon, and C/O ratios, for 11 Galactic bulge planetary nebulae (PN) based on our low resolution UV data from IUE observations and optical spectrophotometry from the Anglo-Australian Telescope. We compare the observed abundances with those predicted by dredge-up theory for the high metallicity Galactic bulge. The sample abundances are also contrasted with the abundances found for PN in the Galactic disk. The mean C/O ratio for the bulge PN is significantly lower than that found for Galactic disk PN. Further, we present an abundance analysis of the very metal-poor bulge PN M2-29. From an analysis of the differential extinction found from the observed ratios of the He ii 1640,4686Å lines, we find that the ultraviolet reddening law towards the bulge is steeper than in the solar neighbourhood.
Astrometry with the HST Fine Guidance Sensors
Authors: Lattanzi M. G. , Bucciarelli B. , Holfeltz S. T. , Taff L. G.
Published: June 2019

This paper presents an overview of the current status of astrometry with the Fine Guidance Sensors (FGSs) on the Hubble Space Telescope. The FGSs have two astrometric modes of operation, one for positional (POS) and one for transfer function (TRANS) astrometry. The positional mode is intended for parallax and angular velocity work. Owing to optical aberrations in the Optical Telescope Assembly (OTA) (i.e., the main telescope optics) beyond the spherical aberration, and instabilities within the combined OTA/FGS optical system, it is undergoing additional feasibility review. Preliminary engineering tests showed changes in stellar pair positions of ∼ 100 milli-arc seconds which are far too large to allow for the expected ∼ 1 mas calibration. Alternate calibration procedures and data reduction algorithms are currently being developed to maximize the scientific potential of this mode which can be fulfilled at the ∼ 3 mas level.

The other operational mode-primarily intended for work on double stars but also usable for angular diameter determination-has proven more stable. Even the deleterious effects of the thermally induced solar array jitter have mostly been overcome. A large collection of reduction and analysis software is available to support this measurement technique (Lattanzi, Bucciarelli, Holfeltz, and Taff 1992) and its calibration is proceeding apace. Interesting scientific work from the FGSs on bright Hyades binaries and the highly eccentric double star ADS 11300 has already been published (Franz et al. 1991, 1992).

Finally, a new FGS Instrument Handbook (Taff 1992a) has been prepared which should minimize the complications of dealing with the General Observer Proposal Forms.
Observations of Faint Stars Deep to 16th Magnitude with CCD Meridian Circle
Authors: Yoshizawa M. , Suzuki S. , Kuwabara T. , Ishizaki H.
Published: June 2019

The experimental works for the development of the CCD micrometer to be used in global astrometry are coming to the final stage at the National Astronomical Observatory, Mitaka. Our goal is to observe and determine the precise optical positions of faint celestial objects deep to 16th mag with meridian circle. The so-called drift scanning method is adopted as the basic electrical architecture to detect and accumulate the photons from the target objects. Reported in this paper are the performances and some results of the test observations made by using the CCD micrometer equipped to Gautier meridian circle at Mitaka. The present CCD meridian circle was used in 1991 to determine directly the optical position of 3C273B in the FK5 system. Also reported are the test observations of the Seyfert galaxy NGC 1068.
The Third Catalogue of Nearby Stars — Results and Conclusions
Authors: Jahreiß Hartmut , Gliese Wilhelm
Published: June 2019

The nearby stars constitute the statistically most complete and therefore most representative sample of stars in our Galaxy. Only this sample allows a direct investigation of luminosity function and kinematics of low-mass stars.

A study of the Third Catalogue of Nearby Stars reveals a considerable increase — not only in quantity but also in quality — in our knowledge of the immediate solar neighbourhood, and reflects very nicely the progress achieved during the last decades — especially in astrometry and photometry. Expectations for the near future (HIPPARCOS) and desiderata for further astrometric and photometric work will be discussed.
An Assessment of the Accuracy of the Deep Space Network Extragalactic Reference Frame
Authors: Jacobs C. S. , Sovers O. J.
Published: June 2019

The Deep Space Network (DSN) Radio Reference Frame consists of a catalog of angular positions for 281 extragalactic radio sources based on VLBI measurements made during the period from 1978 to 1992. A realistic assessment of the accuracy of these source position estimates must consider both modeled stochastic errors and systematic model deficiencies. Modeled stochastic errors include thermal noise (signal-to-noise ratio) and fluctuations in tropospheric refractivity due to the changing distribution of water vapor. These modeled errors result in a median formal position uncertainty of ≈0.3 milliarcseconds (mas). In particular, we examine the effect of changing the model for inter-observation correlations of water vapor fluctuations on estimated parameters. Next, a comparison of our radio source positions with independently determined positions is presented as evidence of systematic errors at ≤ 0.5 mas. We discuss several aspects of VLBI model accuracy focussing on tidal effects, antenna thermal expansion, pressure loading, source structure, precession and nutation. Prospects for reducing these errors are also discussed. We conclude by combining these estimates of modeled stochastic errors and systematic errors into an overall assessment of < 1.0 mas for the current accuracy of the DSN extragalactic radio frame.
Difference Filter and its Application in Separating Periodic Components of Polar Motion
Authors: Li Zheng-Xin , Qian Chang-Xia
Published: June 2019

A new filtering method, in which the difference of second order is used to filter a time series of equal interval, and an example of its application on the separation of Annual and Chandler wobbles of polar motion are given in the paper.
Variations of Short Periodical Oscillations of Earth Rotation
Authors: Kołaczek B.
Published: June 2019

The short periodical oscillations of variations of Earth rotation parameters (ERP) with periods of about 120, 100, 80, 60, 50 days are the most energetic oscillations after the Chandler and seasonal ones. These oscillations were analysed using SLR and VLBI data and the narrow Ormsby band-pass and Fourier Transformation filters. Polhodes of these oscillations for the last several years were computed. Amplitudes of these oscillations are of the order of 2–5 mas and are changeable. They are modulated with a period of about 600 days.
The International GPS Service for Geodynamics (IGS) and the Terrestrial Reference Frame
Authors: Mueller Ivan I.
Published: June 2019

At the 20th General Assembly of the IUGG in Vienna, Austria, in August, 1991, Resolution No. 5 recommended that the concept of an International GPS Service for Geodynamics (IGS) be explored over the next several years and that campaigns be conducted to test the practicality of the concept.
Astrometric Latitude and Time Observational Database at Shanghai Observatory
Authors: Li Zheng-Xin , Chen You-Fen , Qian Chang-Xia
Published: June 2019

After the closing of Bureau International de L'Heure (BIH) and the establishment of International Earth Rotation Service (IERS) at the end of 1987. Shanghai Observatory has been the institute where the astrometric latitude and time observational data are collected and treated. During the past four years, about 75,293 measurements in latitude or time determination have been obtained by the 64 optical astrometric instruments over the world from which the five-day Earth Rotation Parameters of the 1988–1990 period have still been reduced. Twelve Quarterly Report on the optical ERP have been distributed. Since the beginning of 1991 the regular reduction of the ERP has been stopped but the collecting of the observational data is still going on in Shanghai Observatory in order to meet the requirements of the scientists who are still interested on the studies concerned with these observations. There are still 42 optical astrometric instruments taking part into the regular observations at the moment.
The Hertzsprung-Russell diagrams of old stellar Populations
Authors: Baum W. A.
Published: June 2019

The color-magnitude diagrams of globular star clusters are described and attention is called to some evolutionary implications. The predominant stellar population of large elliptical galaxies is shown to be unlike that of globular star clusters but probably similar to that of the older stars in the disk of our Galaxy. The same is true of the population in the nuclei of spiral galaxies. Dwarf ellipticals, on the other hand, are found to have a globular-cluster-type population. The kind of stellar population predominant in a galaxy seems to depend upon the magnitude and the rotational flattening of the galaxy. A unified evolutionary hypothesis is proposed to account for the existence of galaxies of different types.
Sub-luminous blue stars and white dwarfs
Authors: Greenstein Jesse L.
Published: June 2019

Sub-luminous stars of high temperature show a wide variety of spectra and physical properties. Vorontsov-Velyaminov has called this region of the HR diagram the “blue-white sequence”. I wish to discuss the fainter members of this class. The growth of knowledge of colors and spectra has been rapid compared to that of the luminosities, and unfortunately only rough location in the HR diagram is yet possible. Figure 1 shows the general location and subdivision of sub-luminous stars. I shall discuss:

(1)

Old novae.

(2)

Horizontal-branch stars.

(3)

Hot subdwarfs.

(4)

White dwarfs.
The Hertzsprung-Russell diagrams for hot Stars and O- and T- associations
Authors: Kopylov I. M.
Published: June 2019

One of the most important points in the study of the problem of the origin and evolution of stars is a detailed analysis of the structure of the HR diagram as a whole, and the structure of its separate sequences.
Population Synthesis of Composite Systems
Authors: Pickles Andrew
Published: June 2019

Metallicity and age dispersion among the stars comprising stellar composite systems are discussed, with emphasis on the present and future implications for the technique of population synthesis.
Investigating the Scatter in the V26 – log σ relation
Authors: Gregg Michael , Dressler Alan
Published: June 2019

The nature and existence of a second parameter needed to characterize the family of normal elliptical galaxies has been much discussed. The need for a second parameter has been demonstrated by the correlation of the residuals from the well–known magnitude–velocity dispersion relation for ellipticals with other observables such as ellipticity, mass–to–light ratio and Mg line strength or metallicity. Here, evidence for a correlation between residuals in the V26 – log σ relation and the strength of Hβ is presented, suggesting that variations in the stellar populations in Virgo elliptical cores may be an important secondary parameter.
Disk Rotation Curves in Triaxial Potentials
Authors: Gerhard Ortwin E. , Vietri Mario
Published: June 2019

The apparent rotation curve of cold gas in a triaxial potential often differs from that in an axisymmetric system in characteristic ways. The data argue for triaxial bulges in our Galaxy and several others.
Spectroscopy of the Globular Clusters in M87
Authors: Mould J.R. , Oke J.B. , Nemec J.M.
Published: June 2019

With a velocity dispersion of 370 ± 50 km/sec the globular cluster system of M87 is kinematically hotter than the stars in the giant elliptical itself. This is consistent with the clusters' shallower density distribution for isotropic orbits. the mean metallicity of the 27 clusters in the sample analyzed here is no more than a factor of 2 more metal rich than the cluster system of the Milky Way, but considerably more metal poor than the integrated starlight in the field at a radius of 1' from the center of M87. There is no evidence for the existence of young clusters in the system. the mass-radius relation between 1' and 5' required to contain the globular clusters joins on to that required to contain the hot gas around M87.
Self-consistent Models of Perfect Triaxial Galaxies
Authors: Statler Thomas S.
Published: June 2019

We have used Schwarzschild's (1979) method to study the variety of self-consistent solutions available to the family of triaxial “perfect ellipsoids” (de Zeeuw 1985). the time-averaged density at 240 points within the mass model is computed for each of 1065 orbits distributed regularly in phase space and covering all four major orbit families. the underdetermined linear system thereby defined is solved in two ways. First, Lucy's (1974) iterative scheme is used to find a “smooth” solution, lying in the interior of the (mathematically-allowed) solution space. Second, linear programming is used, with linear combinations of the x and z components of the total angular momentum as cost functions, to delineate the boundary of the projection of the solution space in the Lx — Lz plane. the above procedure is applied to 21 figures, with axis ratios, b/a and c/a, chosen at equal intervals of 1/8.
On the Distribution Function of Elliptical Galaxies
Authors: Kashlinsky A.
Published: June 2019

Distribution functions containing cutoff in energy impose several limitations on systems they describe, e.g., no circular orbits are allowed in the major part of system and spatial boundary is poorly defined. As opposed to these functions, we present here distribution function that describes galaxies of finite extent (i.e., truncated in radius). We discuss properties of systems having this distribution function for spherical and axisymmetric cases and compare their surface brightness, isophotes, and rotation curves with observations of elliptical galaxies. This distribution function can easily be generalized to a triaxial galaxy.
A Survey of Radio Recombination Line Emission From the Galactic Center Region
Authors: Anantharamaiah K. R. , Yusef-Zadeh Farhad
Published: June 2019

Preliminary results of a systematic survey of H78α, H91α and H98β emission from the inner 40′ of the Galactic center region are presented. This region consists of two prominent continuum features, the Sgr A complex and the radio continuum Arc. In spite of much nonthermal emission arising from these two features, we detected strong line emission with large line widths in more than half of the observed 130 positions. Many of the detections are new, in particular −50 km s−1 ionized gas linking the Sgr A complex and the Arc, β line emission from GO.1+0.08 (the arched filaments), and α line emission from the loop-like structures which surround the non-thermal filaments near G0.2−0.05. We find that much of the detected lines are probably associated with the −50 km s−1 and the 20 km s−1 molecular clouds, known to lie near the Galactic center. We present line profiles of a number of Galactic center sources including Sgr B1, Sgr C and Sgr D.
The Circum-nuclear Disk
Authors: Genzel R.
Published: June 2019

This review summarizes our current knowledge about the interstellar matter between about 1.7 and 10 pc(a) from IRS16/SGR A∗, a region which now commonly is referred to as the circum-nuclear disk (CND). I will discuss first the spatial distribution of the neutral and partially ionized, interstellar matter, then its physical parameters and excitation and, finally its dynamics. For other recent reviews of the subject I refer to the articles by Güsten (1987), Genzel (1987), Genzel and Townes (1987) and Jaffe (1987).
The Compact Nonthermal Radio Source at the Galactic Center: an Update
Authors: Lo K. Y.
Published: June 2019

We review the current observational status of Sgr A∗, the compact nonthermal radio source at the galactic center. Sgr A∗ is a unique radio source at a unique location of the Galaxy. It is unlike any compact radio source associated with known stellar objects, but it is similar to extragalactic nuclear compact radio sources. The positional offset between Sgr A∗ and IRS16 places little constraint on the nature of the underlying energy source, since IRS16 need not be the core of the central star cluster. Sgr A∗ is still the best candidate for marking the location of a massive collapsed object.
Manifestations of a Massive Black Hole in the Galactic Center
Authors: Phinney E.S.
Published: June 2019

A young star cluster is a less contrived explanation than a massive black hole for many of the features seen in the Galactic center. However from a Copernican point of view, this explanation is less attractive than a black hole. The evidence for a ~ 106M⊙ black hole is becoming progressively less convincing, but the case against it is no stronger. We describe the development of a singular star cluster, as well as the processes of stellar disruption, merging, and gas accretion in such a cluster. Recently merged stars and tidally stripped giants may be detectable within an arcminute of the Galactic Center. We examine the physics of star formation in the inner parsecs of the galaxy, and the problem of maintaining the two parsec molecular torus.
Study of the Galactic Center with a High Resolution Gamma Ray Telescope
Authors: Fenyves Ervin J. , Balog Stephen N. , Cline David B. , Atac M.
Published: June 2019

It is generally accepted that massive black holes are the most likely source for the energy radiated from active galactic nuclei, and may explain the enormous amount of energy emitted by quasars, radio galaxies, Seyfert galaxies, and BL Lacertid objects. Although the detailed mechanisms of the black hole formation in galactic nuclei are not clear at present, it seems to be quite possible that the formation of massive black holes is a general outcome of the evolution of galactic nuclei.
Photoelectric observations of flares on UV Ceti
Authors: Melikian N.D. , Shevchenko V.S.
Published: June 2019

Synchronous observations of the UV Cet flares were carried out in 1987. Two 60-cm telescopes in U-band were used. Accuracy of syncronous registration on two telescopes is 0.001s. 15 flares were registered simultaneously during observations. Single short-time (up to 2s) light increases were observed in quiescent state and flares, which are the result of observation errors. No light increase with duration shorter than 10s was registered simultaneously on two telescopes.
Catalog of flare stars in Orion nebula region
Authors: Natsvlishvili R. Sh.
Published: June 2019

A Catalog of flare stars of the region around the Orion Trapezium is compiled. The results of photographic patrol observations of flare stars in this region carried out at the observatories: Abastumani, Asiago, Byurakan, La-Silla, Rojen, Tonantzintla and Uppsala, up to 1986 year are used. The Catalog contains infomation for 491 flare stars and their 654 flares. It is compared with the Catalog of flare stars in the Pleiades region.
Slow flares in stellar aggregates and solar vicinity
Authors: Parsamian E.S. , Ohanian G.B.
Published: June 2019

The study of slow flares in star clusters, associations and Solar Vicinity is carried out. The dependances of flare amplitude from the inverse velocity of flare increasing time in U, B, V bands are obtained. It is shown, that strong flares frequently take place in deep layers of stellar photosphere.
Some resolutions on T Tauri stars
Authors: Ambartsumian V.A.
Published: June 2019

This symposium is dedicated to the results of studies of flare stars. The necessity of the detailed analysis of observational data on flare stars follows from the very simple fact, that until now the theory has not found for the answer to the question: why the young stars of low luminosity are flaring.
Correlation between flare stars and other populations in young clusters and star forming regions
Authors: Shevchenko V. S. , Yakubov S. D.
Published: June 2019

Ratio between number OB-stars and that of comparatively bright flare stars in star forming reions are discussed.
H2O megamaser in Orion KL
Authors: Matveyenko L.I.
Published: June 2019

The region of the H2O megamaaer emission in Orion KL had been studied by VLBI method. The structure is a chain of the compact components oriented under the angle X ≅ −80°. The size of the components is ⩽ 0.1 A.U., the brightness temperature Tb ≅ 1017 K, the linewidth of each component is Δ f ⋜ 7 kHz. The emission has linear polarization P ⋝ 80 % and position angle is changed by 9.2 degree / A.U. The velocity of the components has a gradient 0.41 km/sec A.U. The masers are unsaturated, the kinetic temperature Tk ≤ 120 K. The structure corresponds to an expanding protoplanet rings, radius of which is equal R = 6 A.U. The rotation and the expanding velocities are equal 5 and 3.8 km/s accordingly. Mass of a protostar is ~ 0.7 M⊙.
On the connection between the IRAS point sources and galactic nonstable objects
Authors: Gyulbudaghian A.L. , Schwartz R.D. , Rodriguez L.F.
Published: June 2019

The connection between the IRAS point sources catalog and following objects is studied: 1. H2O masers, 2. Herbig - Haro objects, 3. Cometary nebulae, 4. Compact nebulae, situated in the large nebulae, and 5. Dark globules. It is shown, that more than 50% of the 1, 2, 3, and 4 type objects are connected with the IRAS sources. More than 10 new H2O masers, connected with IRAS sources are found, one of them having very unusual properties. More than 10 dark globules are found in the Cep OB2 association, which are connected with IRAS sources. One of these sources consists of 4 components, forming a Trapezium-like configuration.
The Balmer decrement in red dwarfs spectra during the flares and quiescent state
Authors: Katsova M.M.
Published: June 2019

The Balmer decrements observed from flare stars during the flares and out-of-flare are analyzed on the basis of our new consideration of hydrogen atom kinetics. The steep Balmer decrements correspond to the emission source with electron density ne ≤ 1013 cm−3 optical depth at the Lα line centre τ(Lα) ≤ 107 for T=104, The low-sloping Balmer decrement, being typical for flare maximum of red dwarfs as well as for several flare stars with measurable X-ray emission out-of-flare, are described by ne = 3 · 1013–1014 cm−3 and τ(Lα)= 107 − 108 for T=(1−1, 5) · 104 K.
Diffuse Reflectance Circular Dichroism for the Detection of Molecular Chirality: An Application in Remote Sensing of Flora
Authors: Wolstencroft Ramon D. , Tranter George E. , Le Pevelen Delphine D.
Published: June 2019

Terrestrial biochemistry is based upon chiral (handed) molecules, of which only one of the two possible hands is predominantly employed. This biomolecular “homochirality”, may be a universal “signature” of life. Along with all living organisms, plant leaves are constructed from arrays of chiral molecules of a single hand. Through the development of a new spectroscopic approach, Diffuse Reflectance Circular Dichroism in the UV-visible wavelength regions, we have detected this chirality non-invasively from non-specular light scattered by leaves. The characteristic spectra are sensitive to plant species and leaf age/health. The technique may provide a means of remote sensing the state of flora and, at closer range, an indicator of living organisms for interplanetary landers.
Synthesis of Organic Compounds in the Circumstellar Environment
Authors: Kwok Sun
Published: June 2019

Recent developments in infrared spectroscopy have made possible the detection of the stretching and bending modes of organic molecules in space. Infrared emission bands of the C-C and C-H stretching and bending modes of aromatic compounds have been widely observed in carbon-rich planetary nebulae, the descendents of carbon stars. Infrared spectra of the transition objects between carbon stars and planetary nebulae, called proto-planetary nebulae, have shown definite signatures of a variety of aliphatic side-groups attached to aromatic rings. This suggests that molecular synthesis is actively ongoing in the circumstellar environment and the chemical nature of these compounds evolve over time scales as short as several hundred years.
Quantum Mechanics and the Origin of Life
Authors: Davies Paul
Published: June 2019

The race to build a quantum computer has led to a radical re-evaluation of the concept of information. In this paper I conjecture that life, defined as an information processing and replicating system, may be exploiting the considerable efficiency advantages offered by quantum computation, and that quantum information processing may dramatically shorten the odds for life originating from a random chemical soup. The plausibility of this conjecture rests, however, on life somehow circumventing the decoherence effects of the environment. I offer some speculations on ways in which this might happen.
Origins of Life and the RNA World: Evolution of RNA-Replicase Recognition
Authors: Guogas Laura , Hogle James , Gehrke Lee
Published: June 2019

Central to understanding the origin of life is the elucidation of the first replication mechanism. The RNA World hypothesis suggests that the first self-replicating molecules were RNAs and that DNA later superceded RNA as the genetic material. RNA viruses were not subjected to the same evolutionary pressures as cellular organisms; consequently, they likely possess remnants of earlier replication strategies. Our laboratory investigates how members of the RNA virus family Bromoviridae can have structurally distinct 3' end tags yet are specifically recognized by conserved replication enzymes. This work addresses the idea that 3' tRNA tails were functionally replaced in some viruses by an RNA-protein complex. These viruses may serve as a timeline for the transition from the RNA world to DNA and protein based life.
Life, the Universe, and SETI in a Nutshell
Authors: Tarter Jill
Published: June 2019

To date, no SETI observing program has succeeded in detecting any unambiguous evidence of an extraterrestrial technology. Regrettably, this paper will therefore not dazzle you with the analysis of the contents of any interstellar messages. However, as is appropriate for a plenary presentation, this paper does provide an update on the state of SETI programs worldwide. It discusses the various “flavors” of observational SETI projects currently on the air, plans for future instrumentation, recent attempts to proactively plan for success, and the prospects for future public/private partnerships to fund these efforts. The paper concludes with some tentative responses to the “What if everybody is listening, and nobody is transmitting?” query.
A New Search for μs Time Scale Radio Pulses
Authors: Demorest Paul , Werthimer Dan , Anderson David , Golden Aaron , Ekers Ron
Published: June 2019

We describe a new search for intrinsically short (μs) dispersed pulses at 21 cm. This search uses coherent de-dispersion, implemented in a distributed computing framework. It will have a sensitivity of 10−18 W/m2 and cover the Arecibo sky ∼ 3 times.
The Rise of Complexity in Nature
Authors: Chaisson Eric J.
Published: June 2019

Cosmic evolution-change, broadly construed-has become a powerful unifying factor in all of science, underlying the rise of complexity throughout Nature writ large. That complexity can be defined and quantified for a whole hierarchy of ordered structures by examining the rate at which normalized energy flows through open, non-equilibrium, thermodynamic systems, from quark to quasar, microbe to mind.
Integrated Science General Education Program (ISGE): Bioastronomy Connections
Authors: Troncale Len
Published: June 2019

A new, NSF-supported, General Education (GE) science curriculum, synthesizes and unifies the key theories and evidence of seven natural sciences using natural systems processes as Integrative Themes. The considerably reformulated subject matter is completely built on interdisciplinary concepts and methods fundamental to newly emerging cross-disciplinary fields like bioastronomy. The year of ISGE study incorporates 15 built-in computer based multimedia features and 10 special learning features to help non-science students learn more science, faster, and with better understanding. Results from seven test course offerings are reported. ISGE intends to be an initial example of the “living, evolving” knowledge bases needed for a space-faring species.
Basic parameters and properties of Wolf-Rayet stars
Authors: van der Hucht Karel A.
Published: June 2019

The numbers, space distribution and energy distributions of Wolf-Rayet stars are reviewed. The numbers of known WR stars in the Galaxy, the LMC and the SMC are 189, 114, and 10, respectively. Distances and galactic distributions determined by various authors are compared and consequences for with evolutionary studies are discussed. Finally energy distributions from the optical to the radio regime are reviewed.
High resolution IRAS images of large shells around Wolf-Rayet stars
Authors: Manchado Arturo , García-Segura Guillermo , Chu You-Hua
Published: June 2019

High-resolution IRAS images, processed by HIRES, are ideal for the search of large, cold, fossil shell structures around Wolf-Rayet stars. In our preliminary effort, we have confirmed the large, 1.°5 — 2°, ring structures around NGC 6888 and RCW 58, which are clearly shown in the HIRES processed images. We interpret them as fossil bubbles blown by the main-sequence progenitors of the WR stars, although these large shells were previously suggested to be evolved supernova remnants.
WR+O binaries observed from the DAO
Authors: Hill G.M. , Underhill A.B.
Published: June 2019

We report here the results, to date, of our monitoring of northern WR stars. New orbits have been published for the short period binaries HD 193576 and HD 214419. Of particular interest are two long period binaries with fairly eccentric orbits, HD 190918 and HD 193793. A new orbit has been determined for HD 190918. We are currently analysing spectra obtained over one cycle of the 7.9 year period of HD 193793. Other stars on our primary target list include HD 192163, HD 192641, and HD 193077.
Evidence for shocking behaviour in WR133 (HD 190918, WN4.5+O9.5I)
Authors: Bertrand J. F.
Published: June 2019

Analysis of radial velocities of the WR binary WR133 yield semi-amplitudes KWR = 49±2 km s−1 and Ko = 21±2 kms−1 respectively and a mass ratio q = 0.43. The HeII 4686Â profiles show increased blue emission when the base of the wind-interaction cone is directed towards the observer.
Polarimetric versus photometric variability of Wolf-Rayet star winds
Authors: Richardson L. L. , Brown J. C.
Published: June 2019

Intensive broad band observations of WR stars by Moffat et al. reveals photometric and polarimetric variability on time-scales of hours, similar to that seen on narrow spectral features. The r.m.s. fractional photometric variation is found to be about 20 times the r.m.s. polarimetric variation whilst simple scattering theory predicts ratios of order unity. The possibility that this discrepancy is due to polarimetric cancellation of the Stokes parameters of light scattered from many dense blobs at random positions (known from spectrometric data to be present) is investigated analytically and by simulations. It is found that factors of 20 reduction in the polarimetric variability cannot be achieved for reasonable numbers of blobs and it is concluded that further polarimetric suppression by substantial blob optical depth and/or intrinsic blob emission must play a role. These results put further constraints on physical conditions in WR wind inhomogeneities.
MCA1B - A dormant LBV in M33?
Authors: Crowther Paul A. , Smith Linda J. , Willis Allan J.
Published: June 2019

A detailed study of the Ofpe/WN9 candidate MCA1b in M33 (Willis et al. 1992) is presented, based on new high-resolution observations. We re-classify MCA1b as WN9-10 and determine its physical parameters (T* = 29 kK, logL/L⊙ = 5.9, log· = −4.0, v∞ = 420 km s−1) and composition (H/He = 2.6, N/He = 0.003, C/N = 0.2) using the Wolf-Rayet standard model. Overall, MCA1b is very similar to the LMC stars R84 (WN9, Crowther et al. 1994) and R71 (LBV, Lennon et al. 1994) indicating a similar evolutionary status and metallicity.
Theory and observations of non-thermal phenomena in hot massive binaries
Authors: White Richard L. , Chen Wan
Published: June 2019

The shock between the colliding winds in binary systems containing two massive stars accelerates particles to relativistic energies. These energetic particles can produce observable non-thermal radiation from the radio to γ-rays. The important physical processes in such systems are very similar to those we have proposed for non-thermal emissions from single hot stars, which have shocks generated by instabilities in the radiatively driven stellar winds. This paper discusses the theory and observations of non-thermal radiation in the radio, X-ray, and γ-ray regions from both single stars and massive binaries. Similarities and differences between the two types of systems are outlined. We discuss two important physical effects that apparently have been neglected in previous theoretical work on colliding wind binaries.
Hydrodynamics and high-energy physics of Wolf-Rayet colliding winds
Authors: Usov Vladimir V.
Published: June 2019

The stellar winds flowing out of the components of WR+OB binaries can collide and shock waves are formed. Stellar wind collision, particle acceleration by the shocks and generation of X-ray, γ-ray, radio and IR emission in WR+OB binaries are discussed.
Search for short-time periodic variations among WR+C binaries
Authors: Marchenko S.V. , Antokhin I.I. , Bertrand J.-F. , Lamontagne R. , Moffat A.F.J. , Piceno A. , Matthews J.M.
Published: June 2019

During the 1992–1993 observing season, WR3, 6, 16, 40, 66, 82 and 134 were monitored in fast photometry mode with time-resolution 0.005—0.01 s. Only WR6 reveals a possible period of P = 0.11 s (semi-amplitude A = 0.025 mag), which is close to the derived equilibrium period of a new-born pulsar in a binary system after the rapid phase of Roche Lobe Over-Flow from the original secondary component.
Summary talk
Authors: Conti Peter S.
Published: June 2019

A personal, but critical summary of the papers at this conference is presented.
The Jodrell Bank - IAC 33 GHz Interferometer
Authors: Harrison D. L. , Watson R. A. , Rubiño-Martin J. A. , Macias-Perez J. F. , Davies R. D. , Rebolo R. , Gutiérrez C. M. , Davis R. J.
Published: June 2019

This paper presents results obtained with the Jodrell Bank - IAC two-element 33 GHz interferometer, located at the Teide Observatory on Tenerife, which is designed to measure the level of the Cosmic Microwave Background (CMB) fluctuations on angular scales of 1° and 2°. The result from a maximum likelihood analysis of observations taken at Dec +41° of δTl = 63+7-6μK at l = 208 ± 18 is comparable with those of Boomerang and Maxima. The contribution of possible foreground contaminants are considered.
The Sunyaev-Zel'dovich Effect and Cosmological Parameters
Authors: Birkinshaw Mark.
Published: June 2019

Improved Sunyaev-Zel'dovich effect data from interferometers and single dishes, and new X-ray data from Chandra and XMM, are allowing a more detailed examination of the Sunyaev-Zel'dovich effect/X-ray technique for the measurement of distance, and hence the Hubble constant. This article reviews progress so far and the current results for H0, and discusses the potential of surveys for the Sunyaev-Zel'dovich effect as tests for cosmological parameters and cluster evolution.
The Red-Sequence Cluster Survey: The Value of Ωm and σ8
Authors: Gladders Michael D. , Yee H. K. C.
Published: June 2019

The Red-Sequence Cluster Survey (RCS) is a 100 deg2 optical survey for high-redshift galaxy clusters. One of the goals of the survey is a measurement of Ωm and σ8 via the evolution of the mass spectrum of galaxy clusters. Herein we briefly describe how this will initially be done, and also demonstrate the eventual power of the RCS for this type of measurement by a qualitative analysis of the first 1/10th of the survey data.
Tenerife Experiments: Galactic Contribution to CMB Observations at 1° angular scales
Authors: Macias-Perez J. F. , Watson R. A. , Davies R. D. , Wilkinson A. , Rubiño-Martin J. A. , Gutierrez C. M. , Gallegos J. , Rebolo R. L. , Hoyland R. J.
Published: June 2019

Cosmic Microwave Observations at 1° scales are extremely important on the understanding of modern Cosmology. At those angular scales the CMB power spectrum presents the first Doppler Peak. The position and amplitude of this peak provide strong constraints on cosmological parameters as H0 and Ω0. The JBO-IAC interferometer has observed those angular scales as well as the BOOMERANG and MAXIMA teams. The results from these groups show the existence of the first Doppler Peak. We present a detailed estimate of the galactic contribution to the JBO-IAC interferometer data set using data from the Tenerife and COSMOSOMAS experiments.
Commissioning the Very Small Array
Authors: Rusholme Ben.
Published: June 2019

The Very Small Array (VSA) is a fourteen-element interferometer for sensitive measurement of the CMB anisotropies on scales of three degrees to ten arcminutes. The telescope is now observing on site in Tenerife after a period of commissioning, including the first map of the Sunyaev-Zel'dovich effect in the Coma cluster.

A distinguishing feature of the instrument is that each antenna in the array tracks quasi-independently, providing a characteristic fringe rate per baseline which can be used to reject many systematics. This effect has been optimised in the antenna array design.
VLA and MERLIN Monitoring Observations of the Gravitational Lens System B1030+074
Authors: Xanthopoulos E. , Browne I. W. A. , Patnaik A. R. , Wilkinson P. N.
Published: June 2019

We present VLA and MERLIN monitoring data of the JVAS gravitational lens system B1030+074. The system was monitored with the VLA from February 1998 to October 1998 at 8.4-GHz during which the VLA was at its A, BnA and B configuration. The 47 epochs of observations have an average spacing of approximately 5 days. Ten MERLIN snapshots were obtained in the L-band (1.7 GHz) during the months of April, May and June 1998. Preliminary light curves of the two components of the lens system obtained from the VLA data indicate that during the period of the monitoring the A flux density showed a steady decrease. No changes are observed in the B light curve.
Water masers and the near-stellar environment in YSOs
Authors: Claussen Mark J.
Published: June 2019

I present a review of observations of water masers, in particular very high angular resolution of water masers using Very Long Baseline Interferometry, with which it is possible to probe the environment of young stellar objects and forming stars within only a few A.U. of the protostar, its accretion disk, and therefore the base of outflowing material. Although reference is made to some high-luminosity sources, the main thrust of the review are the water masers found toward forming objects whose mass and luminosity will be approximately that of the Sun when they reach the main sequence.
Highly polarized burst of a water maser in Orion-KL
Authors: Horiuchi Shinji , Kameya Osamu
Published: June 2019

It has been reported that the 22 GHz water maser in the star forming region Orion-KL has started an outburst in rate 1997 (Omodaka et al. 1998, IAUC 6893). Using Mizusawa radio telescope we started a monitoring observation of the bursting maser. We measured the linear polarization of the maser after the burst, during a phase of rapid flux density decrease. We find that the total flux density of 2.4 × 106 Jy (December 1998) exhibits about 46% linear polarization. Over the next six months we find that the total intensity decrease about two orders of magnitude while the fractional linear polarization gradually fell to 30%. These results suggest that the present bursting phenomenon has an origin similar to the super maser event starting in 1979, and the phenomenon of the extremely bright masers in this region is geometric in nature and related to the strong magnetic field.
A study of the H2O maser emission from R Cas
Authors: Brand Jan , Baldacci Lara , Engels Dieter
Published: June 2019

Over the past decade we observed a sample of late-type stars (supergiants, semi-regular variables, OH/IR stars, and Mira's) 3-4 times per year in the 1.3-cm line of H2O. The observations were carried out with the Medicina 32-m and the Effelsberg 100-m telescopes. In addition, a sub-sample of these stars was observed at several epochs with the VLA. In our analysis we also use data from the literature, for instance on mass loss and optical variability. The aim is to investigate the properties of the circumstellar outflows and to elucidate the maser-pumping mechanism. In the conference poster we presented some preliminary results of a 4-star sub-set of the data base; in the small space available here, we briefly describe the monitoring program, and discuss the Mira-variable R Cas in some detail.