bluuebunny/crossref_metadata_2025 huggingface dataset:
A microcomputer controlled CCD H-alpha spectrometer
Authors: McDavid David A.
Published: June 2019

A miniaturized spectrometer designed for mounting at the Cassegrain focus of a 40 cm telescope has been built and laboratory tested with promising results. The optical system consists of a slit, spherical mirror, and reflection grating in a Littrow configuration. The detector is a 128 element linear CCD cooled by an evacuated microminiature nitrogen refrigerator and interfaced to a microcomputer using direct memory access. Laboratory spectra of a mercury vapor discharge tube have been obtained and demonstrate 1 Angstrom resolution with low noise. The spectral coverage of about 100 Angstroms is suitable for measurement of stellar H-alpha line profiles, and it is anticipated that the instrument can be used to monitor bright Be stars.
Effective Operators in Charge Exchange Studies
Authors: Levy B. , Provost J. , Roueff E.
Published: June 2019

The rate coefficient for the charge transfer reaction C+2po + H → C 3p+ H+ is calculated with the introduction of the radial coupling between the two 3π states arising from both asymptotic atomic states. the derived rate coefficient at a temperature of 104K is 2 10−15 cm3s−1 which is two orders of magnitude larger than the value previously estimated by Butler and Dalgarno (1980) from a weak spin orbit coupling between the 3Σ− and 3Σ+ molecular states of CH+.
Tunable Ultraviolet Laser Studies of Photon-Molecular Interactions of Cometary Interest
Authors: Jackson William M.
Published: June 2019

Most of the cometary radicals are thought to be formed in the coma by photodissociation processes. Successful modeling of the coma requires a detailed knowledge of the products that are formed from the various parent molecules, and the energy partitioning among these products. This information has to be obtained as a function of wavelength, because the Sun is not a monochromatic source. in this review, the status of the experimental knowledge of some key molecules will be discussed, along with the prospects of some new laboratory techniques that can fill in the gaps in our present knowledge.
Chemistry in the Early Universe
Authors: Dalgarno A. , Lepp S.
Published: June 2019

The chemical processes which led to the formation of molecules in the early universe are described. Molecular hydrogen is formed by two sequences. in one, radiative attachment to form H− is followed by associative detachment and in the other radiative association to form H2+ is followed by a chemical reaction with H. Trace amounts of HD and the molecular ion LiH+ are formed by the reaction of D+ with H2 and by the radiative association of Li+ and H. The H2 molecular fraction in the expanding universe is about 10−6.

Because they are cooling agents, hydrogen molecules are significant in the collapse of pre-galactic clouds. With increasing density the hydrogen gas is converted to molecular hydrogen by three-body recombination and emission from the rotational and vibrational levels cools the cloud and slows the rise in temperature of the gravitationally collapsing object. Ultimately though, the radiation is trapped and the temperature rises. The H2 molecules are then destroyed by collision-induced dissociation. At still higher temperatures collisional ionization occurs, initiated most probably by the process of associative ionization.

Molecules may be significant also in galaxy formation if the explosive amplification model is correct. Heavy elements may be present in the shell of gas swept up by the blast waves of the exploded seed galaxies and chemical processes leading to the formation of molecular hydrides may take place, in a scenario analogous to the aftermath of an interstellar dissociative shock.
Observations of Molecules in Diffuse Clouds
Authors: Somerville W B
Published: June 2019

We are actively engaged in observing and analysing molecules in diffuse clouds, in the directions of reddened stars (1). This paper presents some recent results. In the ultraviolet, using the IUE satellite, we have so far observed 60 stars in a continuing programme to study interstellar CO, with more than 30 detections of 12CO and 10 of 13CO; almost all of these are new detections (2). the results have been compared with microwave observations of CO in selected directions, and with our own and other optical observations of CH, CH+ and CN.
Physical and Chemical Analysis of Orion KL
Authors: Ohishi Masatoshi , Kaifu Norio , Suzuki Hiroko , Morimoto Masaki
Published: June 2019

We studied excitation of interstellar molecules and chemical environment in Orion KL by analyzing more than 200 spectral lines detected by the 45-m telescope at Nobeyama Radio Observatory (NRO).
Astrochemistry of Interstellar Clouds: II. Molecular Formation in a Contracting Cloud
Authors: El Shalaby M.A. , Aiad A.
Published: June 2019

The chemistry of an 667 Mo interstellar cloud was studied using 142 reactions for 40 species during the contraction under self gravity in two steps. At first the contraction is allowed without gas phase reactions untill certain optical depth is reached. Secondly, at this optical depth the chemical reactions are started for sufficient cycles in a time dependant scheme till only very small additionally changes in the abundances occur. The so obtained, relative abundances and coulmn densities for different species represent a continous function of the optical depths. The values arround τ=6.3 represent the observations for H2, H2+, H3+, OH, OH+, CH, CH+, CH2, CH2+, CH3+, H2O and H3O+. The region of τ between 1 and 5 i.e. of particle density between 4 102–6 103 is the preferable formation place for the majority of molecules.
Chemistry in Interstellar Hydroxyl Maser Regions
Authors: Hartquist T. W.
Published: June 2019

The pumping of the upper levels of the 2π3/2 J=3/2 state of OH at sufficient rates to account for the observed strengths of interstellar hydroxyl masers requires that OH contains a substantial fraction of the oxygen. Shocks have been suggested as the sites of the OH production, but a better understanding of OH photodissociation and observations of hydroxyl maser kinematics have led to the realization that the original hydroxyl maser shock model must be revised. the possibility that interstellar hydroxyl masers occur in dense molecular photodissociation zones, heated by photoabsorption and perhaps by ion-neutral friction in the magnetic precursor of a shock, is considered. Possible infrared line emission from interstellar hydroxyl maser regions is mentioned.
The Relationship of OH and H2O Masers to the HII Regions in Cep A
Authors: Hughes V. A.
Published: June 2019

There is evidence to show that OH and H2O maser emission is associated with the early stages of star formation. But the complexity of both the HII regions and the distribution of maser sites, makes it difficult determine how they are associated. Recent high resolution radio observations of Cep A, obtained using the VLA (Hughes 1985), together with accurate positioning of OH and H2O masers using MERLIN (Cohen et al. 1985), may help in this matter.
Deuterated Molecules in Interstellar Clouds
Authors: Wootten Alwyn
Published: June 2019

We show that deuteration in DCN and HDCO probably derives from CH2D+ in warm clouds, and that the levels of deuteration observed in those clouds require that radiative association play an important role in the chemistry of interstellar clouds.
Dusty Knots in Supernova Remnants
Authors: Rengarajan T. N. , Verma R. P. , Iyengar K.V.K.
Published: June 2019

Dusty knots are known to exist within supernova remnants (SNRs). the dust in these knots could be sufficiently heated by the X-ray emitting plasma to radiate in the far-infrared (FIR) wavelengths. We have searched the IRAS Point Source Catalogue for FIR sources associated with 117 SNRs from the catalogue of van den Bergh. We selected IRAS sources with definite flux densities at 60 μm or 100 μm and the flux density increasing with wavelength beyond 25 μm. For each SNR, background source density was determined in an area surrounding the SNR and the number of excess sources within the SNR area (with 10% radial extension) was determined.
Abundance Determination in Wolf-Rayet Stars
Authors: Underhill Anne B.
Published: June 2019

Wolf-Rayet stars are rare and their basic properties such as mass, effective temperature, and luminosity are similar to those of 09 to B1 stars. the spectra of Wolf-Rayet stars from about 10 μm to 1000 Å consist of rather broad emission lines on a continuous spectrum. the continuous spectrum corresponds to effective temperatures in the range from 25000 to 30000 K (Underhill 1983b). A few shortward displaced absorption troughs appear and a few emission lines are flat topped. There is a strong infrared excess attributed to thermal bremsstrahlung (Cohen, Barlow, and Kuhi 1975), and there is rather strong 6 cm radiation (a fraction of a mJy from stars at distances of the order of 1500 pc), see for instance, Bieging, Abbott, and Churchwell (1982). the radio radiation can be attributed to thermal bremsstrahlung and to magnetic bremsstrahlung (cyclotron radiation), see Underhill (1983a). X rays have been measured from a few Wolf-Rayet stars (Sanders, et al. 1985).
Chemistry in Stellar Atmospheres: Theoretical Studies and Comparison with Observations
Authors: Vardya M. S.
Published: June 2019

The construction of model atmospheres is an eight-fold pathway. These pathways are described, with special reference to the chemistry of cool stars. A brief review of the present state of the art is presented, highlighting the outstanding problems. A few salient results are mentioned.
Detection of Unresolved Circumstellar Lines in Stellar Infrared Spectra and Discovery of Quasi-Static Molecular Envelope Around Red Giant Stars
Authors: Tsuji T.
Published: June 2019

It is found that the low excitation lines of the first overtone band of CO in the infrared spectra of normal red giant and supergiant stars include excess absorption that cannot be explained by the photospheric absorption alone. the excess absorption is shown to be due to unresolved circumstellar absorption originating from hitherto unrecognized quasi-static molecular envelope around normal red giant and supergiant stars. As contrasted to the previously known expanding circumstellar envelope recognized by Doppler-shifted absorption lines, the newly found static envelope has the following characteristics: (1) excitation temperature determined from CO lines is between 500 and 1000K, indicating that the envelope may be located at a few stellar radii above the photosphere, (2) turbulent velocity may be as high as 5km/s, (3) CO column density increases from 10+19/cm2 at early M giant to 10+20/cm2 at the latest non-Mira M-giant, and (4) molecular envelope and stellar photosphere show slight relative motion in general. Some implications of such a quasi-static molecular envelope on circumstellar chemistry as well as on stellar mass-loss are discussed.
Molecules in Comets: A Tool to Estimate the Low Energy Cosmic Ray Flux Outside the Solar System?
Authors: Pirronello Valerio
Published: June 2019

It is described a method for evaluating the low energy cosmic ray flux outside the heliosphere. It is based on the chemical modifications induced in cometary nuclei by impinging ions and on the release of synthesized chemical species by comets entering for the first time into the inner solar system.
Compositional Trends in Chondrules from Unequilibrated Enstatite Chondrite, Parsa
Authors: Shukla P. N. , Bhandari N.
Published: June 2019

Multielemental analysis of chondrules from unequilibrated E3 chondrite Parsa show that the lithophile elements, both refractory and volatile, are enriched and siderophiles are depleted relative to C1 abundances. This behaviour is generally similar to chondrules from unequilibrated ordinary chondrites (UOC). A detailed comparison of compositional trends in chondrules from E3 chondrites (Parsa and Quingzhen) with UOC's indicates that some of the precursor components of chondrules of E3's are different from those of UOC's.
The Role of Grains in Interstellar Chemistry
Authors: Williams D. A.
Published: June 2019

Grains affect interstellar chemistry in a variety of ways. Most obviously, they extinguish starlight and thus protect molecules in cloud interiors from photodestruction. The grains themselves contain substantial proportions of particular elements which are therefore less readily available for gas phase reactions and for processing into molecules. Grains in dense clouds are known to accrete molecular mantles which may be further processed; the mantle material is ultimately returned to the gas, either near hot stars or when the clouds are dissipated. Molecular hydrogen, the key to all gas phase chemistry, is undoubtedly formed efficiently on grains, and a plausible mechanism can now be identified. Other molecules, too, form preferentially at surfaces. Finally, the destruction of grains via chemical erosion and by sputtering in shocks provides a substantial molecular contribution to the gas in local regions.
The Role of Dust in Circumstellar Chemistry
Authors: Jura M.
Published: June 2019

The outer envelopes of the outflows from late-type stars where the dust and molecules have already been formed and the matter has been accelerated to its terminal velocity are the focus of this review. One major role for grains in the circumstellar chemistry is the protection of molecules against photodissociation by ambient interstellar ultraviolet photons. Also, in more distant regions where the grains become sufficiently cool as they flow away from the central star, the dust may serve as a condensation sink for molecules which can be bound into mantles.
Lists of Active Galaxies, Problems of Detection and Statistics
Authors: Cannon R. D.
Published: June 2019

The various techniques for discovering active galaxies are reviewed, the main emphasis being on optical techniques and their application to emission-line galaxies with active nuclei. The three principal sets of selection criteria involve morphology, colours and emission lines. The major extant lists of emission line galaxies are summarized. Problems of detection are discussed, including selection effects and the use of automatic plate measuring machines. The difficulties of generating useful statistics on different classes of objects are highlighted, but no attempt is made in deriving new statistics or to summarize those in the literature.
Low Frequency Cutoffs in the Spectra of Radioquiet Quasars
Authors: Antonucci R. , Barvainis R.
Published: June 2019

Radio-quiet and normal radio-loud quasars have very similar spectral properties in the ultraviolet, optical and near infrared regions, but their radio powers differ by several orders of magnitude. Somewhere between the near infrared and the radio their spectra must diverge dramatically.

The IRAS survey detected 17 radio quiet quasars and luminous Seyfert 1's with −29. 5 ≤ Mv ≤ −21.6 (for Ho = 75). By coadding the survey data and using pointed observations, we have detections of most of these objects in all four IRAS passbands. The spectra are all rising with wavelength all the way to 100μ. We are measuring fluxes in the centimeter, millimeter, and, together with R Cutri, the near infrared and optical regions for each of these objects. Our goal is to constrain the location, shape, and spectral context of the low frequency cutoffs. Here we present the IRAS, millimeter and centimeter data. Measurements at the other wavelengths are still in progress.

Although the spectra are rising steeply between 60μ and 100μ, we find that all of our objects are undetectable at 1.3 mm with the NRAO 12-m telescope. Our limits are typically an order of magnitude below the 100μ fluxes. (Ennis et al (1982) and Robson et al (1985) have already shown that the 1 mm fluxes of some radio quiet quasars must be below the extrapolation of the near infrared continuum.) Our objects are all extremely weak or undetected with the VLA at 2 cm and 1.3 cm, at levels typically three orders of magnitude below the 100μ fluxes. The sharpness of the required cutoffs allows us to rule out the hypothesis that the infrared is synchrotron radiation with the cutoff due to an absence of low energy electrons. The high frequency of the cutoffs makes free-free absorption implausible, but not impossible. It is possible that synchrotron self-absorption is suppressing the radio. There is circumstantial evidence that the far infrared is thermal dust emission. This would require a lower cutoff in the distribution of dust temperatures, which we think we can explain.
Statistical Studies of AGN and QSOs
Authors: Stasinska Grażyna
Published: June 2019

We present some preliminary results on the determination of the masses of the central bodies of AGN and QSOs. They are given as an example of the statistical studies we are performing, based on a catalogue which we are still improving, and which is to be a compilation of many observational parameters concerning these objects.
Kinematical and Spectral Evidences of Complex Structure of NGC 1275 Nucleus
Authors: Pronik V. I.
Published: June 2019

The analysis of the available data about spectral observations of nucleus and gas velocity field in NGC 1275 leads to a conclusion on the presence in the nucleus of several spatially separated variable sources responsible for a complex variable emission in Hβ and [OIII] lines profiles.
A Possible Mechanism to Explain the Narrow Line Variability of Seyfert Galaxies on Timescales of Months
Authors: Bochkarev Nikolay G.
Published: June 2019

Gas in the shadow of clouds in the outer parts of the broad line region can radiate a considerable fraction (dozens of percent) of the narrow emission line flux. The variability of the X-ray luminosity of the central source should result in significant variations of the gas emission on a timescale of months. Particularly strong changes of line intensities and column densities of gas in the shadow (~ 1023 cm−2) can be produced by phase transfer between two thermally stable fluids with temperatures 10–20×103 K and 40–100×103 K, which can exist in the shadow of clouds.
Nuclear Activity of Galaxies within Groups
Authors: Fricke K.J. , Kollatschny W.
Published: June 2019

Results from a spectroscopic survey of groups around Seyfert galaxies and of an appropriate control sample are reported. The groups are ≲1 Mpc across. A nuclear spectroscopic “activity class” is assigned to each group member. The active types show a peaked distribution around the Seyfert galaxy and are confined to a critical radius ~300 kpc while the nonactive members are uniformly distributed over the whole extent of the groups. These results are briefly discussed.
Seyfert 2 Galaxies with Double Nuclei
Authors: Fairall A.P.
Published: June 2019

At least two southern Seyfert 2 galaxies show a double peak in their [OIII] line profiles. Spatial spectroscopy shows each peak to associate with a separate Seyfert 2 nucleus. Separations are of the order of 1 arcsec (1 kpc). The implications and the status of these objects are discusssed.
The Role of Environment in the Origin of Radio Emission from Galaxies
Authors: Menon T.K.
Published: June 2019

The influence of the environment on the origin of radio radiation from galaxies is studied by compairing the occurence of radio emission in galaxies in compact high density groups of Hickson (1982) with that in field galaxies of similar types. The study shows that the fractional luminosity functions of elliptical and spiral galaxies in compact groups are similar in shape to that of field galaxies but the probability of a compact group galaxy being a radio source is 5 to 10 times greater than that of an isolated galaxy of the same type. Radio Loud group ellipticals tend to be the optically brightest galaxy in the group independent of their absolute luminosity.
A Search for Low-Level Seyfert Activity in the 500 Brightest Northern Galaxies
Authors: Filippenko Alexei V. , Sargent Wallace L. W.
Published: June 2019

A sensitive search for intrinsically faint Seyfert nuclei in the 500 brightest northern galaxies is being conducted with the Hale 5.08 m telescope. The primary aim is to extend the luminosity function of active galactic nuclei (AGNs) to lower luminosities. Thus far, we have detected Hα emission having full-width near zero-intensity (FWZI) ≳ 4000 km s−1 in a significant fraction (≳10%) of nearby galaxies. Moreover, the narrow emission lines in a given nucleus often have markedly different widths, as shown in detail for M81. Those associated with high critical densities are generally the broadest, indicating that a very wide range of densities is present in the narrow-line region. The relative intensities of the lines can readily be explained with models in which clouds of gas having ne ≈ 102 to 107 cm−3 are photoionized by nonstellar radiation such as that produced by QSOs and luminous Seyfert 1 galaxies.
Circumstellar radio emission from pre-main sequence stars
Authors: Brown Alexander
Published: June 2019

VLA radio continuum observations have been obtained for a number of pre-main sequence (PMS) stars in Corona Australis, Lupus, Scorpius and Taurus. A variety of PMS sources were detected and for other stars upper limits to the ionized mass loss rates were determined. A strong double source, showing two radio jets, was found associated with an embedded infra-red source in the R CrA molecular cloud. Some of the PMS stars show extended radio emission associated with ionized circumstellar envelopes, even though photoionization by EUV photons is not sufficient to produce the ionized regions.
The extended infrared radiation from the L1551 bipolar flow, L > 19 L⊙
Authors: Clark F.O. , Laureijs R.J. , Chlewicki G. , Zhang C.Y.
Published: June 2019

The infrared bolometric luminosity of the extended infrared emission from the L1551 flow is estimated as 19 (−4 +10) L⊙. Ultraviolet radiation from the shock associated with the flow appears to heat the surrounding dust. The extended infrared emission raises the total energy requirement for the flow over a 10^4 year lifetime to 10^46–47 ergs. If gravitational in origin, this energy likely originates from a region <10^13 cm. Infrared radiation offers a new probe for interstellar shocks by sampling the ultraviolet halo surrounding the shock.
Interferometric images of 13CO emission toward HL Tau
Authors: Beckwith Steven , Sargent Anneila
Published: June 2019

Millimeter wave interferometric images of HL Tau show a clear disk morphology with a nearly keplerian velocity curve. A few a few tenths of a solar mass are in orbit around the star.
On the line profiles of shell-shaped bipolar outflows
Authors: Silvestro G. , Robberto M.
Published: June 2019

High velocity molecular outflows with bipolar morphology are detected in association with young stellar objects within dense interstellar clouds. Recent observations suggest that the flow could be “confined to a relatively thin, swept-up shell surrounding an evacuated wind cavity” (1). A shell structure characteristic of the wind-cloud interaction had been predicted in earlier theoretical works (see for instance (2)). More recently, models with different (not shell-shaped) geometries were presented, e.g. (3).
Neutral oxygen in herbig Ae stars
Authors: Praderie F. , Catala C. , Czarny J. , Felenbok P.
Published: June 2019

In stars with dense envelopes such as classical Be and T Tauri stars, the near infrared lines of OI have been observed: λ 8446 Å in emission, λ 7772 Å in absorption or in emission (e.g. Polidan and Peters, 1976; Herbig and Soderblom, 1980). In Herbig stars, only low resolution (2-7 Å) material is available on a few objects (Shanin et al. 1975; Andrillat and Swings, 1976).
The circumstellar environment of chromospherically active T Tauri stars
Authors: Finkenzeller U. , Basri G.
Published: June 2019

We discuss new spectroscopic material on 7 T Tauri stars of low to intermediate activity level which have envelopes of low optical thickness and small circumstellar/interstellar extinction. We show that difference plots between the target star and appropriate standards are a powerful tool to probe the stellar envelope structure. In our sample we find 1 object with a P Cyg type, 3 with inverse P Cyg type, and 3 with symmetrical Balmer line profiles. We conclude that the physical processes in these T Tauri stars do not differ qualitatively from the ones found in extremely active ones. In particular, the inverse P Cyg type profiles are not restricted to stars with very opaque envelopes and are possibly a much more common attribute of young stellar objects.
The EINSTEIN survey of the young stars in the Orion nebula
Authors: Caillault Jean-Pierre , Zoonematkermani Saied
Published: June 2019

We report here on the complete EINSTEIN survey of Orion within the central 2° x 2° region centered on the Trapezium. We present an X-ray mosaic of the Nebula and a complete X-ray catalog (200 sources) for this very young cluster. In addition, we discuss in detail variability, early-type stars, solar-type stars, and K-M stars.
Evidence from optical polarimetry for spiral structure in the magnetic field and cloud density around newly-formed stars
Authors: Warren-Smith R.F. , Draper P. W. , Scarrott S. M.
Published: June 2019

Deep CCD imaging of the Serpens bipolar nebula shows it to be surrounded by molecular cloud material having spiral density structure. Polarization mapping indicates that the magnetic field in this material also exhibits spiral structure and we interpret this as the remains of the magnetically-braked collapse of a protostellar cloud. A binary star system has formed in the cloud core.
A polarization outburst in the T Tauri star UY Aurigae
Authors: Ménard F. , Bastien P.
Published: June 2019

During the course of a monitoring programme of the linear polarization of various T Tauri stars, UY Aur was observed to undergo a strong polarization burst between 1984 October and 1985 January. The linear polarization rised from about 1.5% early in 1984 to a maximum of 7.6% in 1984 October and declined back to the earlier value after 3 to 4 months. It is the first time that such a large increase in linear polarization is reported in a T Tauri star. However the interpretation is complicated by the fact that UY Aur is a visual binary with a separation of 0.8 and both components were included in the measurements.
Polarization measurements of some T Tauri stars
Authors: Joshi U. C. , Deshpande M. R. , Kulshrestha A. K.
Published: June 2019

T Tauri stars show linear polarization typically between 1–3%. A two band linear polarization survey of some T Tauri star was reported earlier by Bastien (1982). Most of the stars show pronounced time variability in polarization and position angle (Bastien, 1980; 1982). Wavelength dependence of polarization is important in determining the specific mechanism(s) producing polarization. For a systematic study of polarization in T Tauri stars, we have taken up an observing programme to measure linear polarization of some stars in Taurus-Auriga region. Polarization measurements of 9 T Tauri stars are reported here. Observations were made on January 8–11, 1984 with MINIPOL (Frecker and Serkowski, 1976) on 61“ telescope of University of Arizona.
Observations of jets from young stars
Authors: Brugel Edward W. , Mundt Reinhard , Bührke Thomas
Published: June 2019

Optical jets, and collimated outflows, are now recognized as a common phenomena associated with young stars (Mundt 1985, Strom et al. 1986). Presented here are the results of new CCD imaging and spatially resolved spectroscopy for ten such objects. Using these and previously published data on twenty known jets, we compiled a set of observational criteria describing the phenomena. From this compilation we addressed several physical questions pertaining to the nature of collimated outflows associated with young stars.
Bow shock models of Herbig-Haro objects
Authors: Raga A. C. , Böhm K.-H. , Mateo M.
Published: June 2019

It has recently been found that models of a radiating bow shock can explain qualitatively the strange emission line profiles observed in some Herbig-Haro (H-H) objects. It is also possible to compare directly the emission line intensity maps predicted from these models with CCD images of H-H objects. Such a comparison between our models and observations of HH 46/47 is presented, showing that the condensation HH 47A may tentatively be identified with a bow shock formed at the “head” of a jet.
Contribution of line emission to the IRAS measurements: NGC 6853
Authors: Zhang C. Y. , Leene A. , Pottasch S. R. , Mo J. E.
Published: June 2019

The contribution from the line emission of ions to the radiation at four IRAS bands has been estimated. The dust grains are likely to be mixed with ionized gas.
A statistical analysis of dust features in the IRAS low resolution spectra
Authors: Gal O. , Muizon M. de , Papoular R. , Pégourié B.
Published: June 2019

Using the IRAS catalog of low resolution spectra (LRS), we have analyzed the silicate features in emission and absorption, the carbon-rich emission features and the featureless spectra, in the range 8–22 μm. The sample sizes are large enough to allow average properties to be established (e.g. energy distributions), as well as correlations between luminosities, excesses, colors and coordinates, and histograms and galactic distributions, all with a good degree of confidence.
Acoustic wave driven mass loss in late-type giant stars
Authors: Cuntz M. , Hartmann L. , Ulmschneider P.
Published: June 2019

Mass loss generated by radiatively damped acoustic waves is investigated. We find that a persistent wave energy flux leads to extended chromospheres. Mass loss is quite likely produced if the wave field retains a transient character and if large wave periods are used.
Relations between coronal and chromospheric activity diagnostics in T Tauri stars
Authors: Bouvier J.
Published: June 2019

The study of the relationships between various activity diagnostics in T Tauri stars (TTS) suggests that the CaII K, MgII k and H∝ lines are formed in a similar region of TTS' atmosphere. For the more active TTS, an extended circumstellar region seems to be the major source of the emission, whereas a solar-type atmosphere alone may be able to account for the emission spectrum of low-activity TTS.
Neutral component of the outerstellar medium in the vicinity of the Sun
Authors: Kurt Vladimir G. , Bertaux Jean-Loup
Published: June 2019

Optical observations of the solar radiation resonance scattering in the hydrogen and helium lines (λ1216Å and 584Å) provide a unique opportunity for determining numerous parameters of the local interstellar medium closest to the Sun (LISM). The distance exceeds 10 to 102 AU where the interstellar medium is no longer perturbed by the gravity field, and the hard and corpuscular radiation of the Sun.
The velocity law of P Cygni
Authors: Duemmler Rudolf , Markova Nevena
Published: June 2019

The multiple absorption components in the Balmer lines of P Cygni indicate that shells are ejected regularly with a period of about 200 days. The newly found multiple, flat-topped emission components are attributed to thin, spherical, expanding shells. Together with the absorptions they allow the derivation of a velocity law, illustrated in the following by a sequence of figures.
Episodic dust formation in the wind of HD 193793
Authors: Williams P.M. , der Hucht K.A. Van , Florkowski D.R. , Pollock A.M.T. , Wamsteker W.M.
Published: June 2019

In 1985 April, the WC7+abs star HD 193793 was observed, using UKIRT, to have brightened significantly in the infrared owing to the formation of a new dust shell. Examination of infrared photometry of this star since 1979 and previously published data indicates that the dust formation occurs at intervals of 7.9 years. Phasing the published radial velocities of the absorption line component with this period confirms that it is a member of an eccentric (e = 0.7−0.8) binary system having periastron passage shortly before dust formation. The X-ray spectrum also changed between 1984 and 1985 in becoming significantly “harder” while the non-thermal radio source disappeared, both changes indicating greater extinction. This suggests a model wherein the source of the non-thermal radio and X-ray emission moves deep into the Wolf-Rayet wind.
Wolf-Rayet nebulae - Enrichment in He and N and effective temperatures of Wolf-Rayet stars
Authors: Rosa Michael R.
Published: June 2019

Nebulae surrounding isolated Pop I WR stars provide observational constraints on as yet poorly determined chemical surface abundances and FUV energy distributions of their central stars. An integral of the mass loss history and the chemical evolution is stored in those parts of the nebulae that have suffered only very little mixing with the ISM (cf. Kwitter 1984). Effective temperatures in the Lyman continuum region are reflected in the ionization structure of oxygen and sulfur (cf. Mathis 1982). For intrinsic problems involved refer to the papers cited above.
The R Aquarii jet
Authors: Cassatella A. , Kafatos M. , Michalitsianos A.G. , Piro L. , Viotti R.
Published: June 2019

The X-Ray (EXOSAT) and ultraviolet (IUE) observations of R Aqr and its jet are discussed in the light of a proposed model.
The enigma of RX Puppis
Authors: Wright Alan E. , Allen David A.
Published: June 2019

RX Puppis is a southern symbiotic star (R.A. 08h12m 28s.2, Dec. −41°33'18“ B1950). For almost a century it has been seen to have had a violent history at optical wavelengths. In 1974 it was discovered, at 5 GHz, to be a weak radio source. Shortly after, its radio spectrum was found to be of the optically thin type, having approximately the same flux density at all frequencies between 2.7 and 22 GHz. This implied that the RX Puppis system contained dispersed, ionized gas having a linear size >1015 cm.
Near IR observations of IRAS planetary nebulae
Authors: Persi P. , Preite-Martinez A. , Ferrari-Toniolo M. , Spinoglio L.
Published: June 2019

We have observed 117 faint planetary nebulae in the J, H, K, and sometimes L and M bands. The objects are all listed in the Perek-Kouteck (PK) catalogue and were observed by IRAS.
CO in planetary nebulae
Authors: Huggins P. J. , Healy A. P.
Published: June 2019

We report the first detection of millimeter CO emission in two highly evolved planetary nebulae: NGC 6720 and NGC 7293. The CO is a useful probe of the structure and kinematics of the molecular gas in the nebulae, and provides an estimate of the mass of material which remains un-ionized by the central star.
Anomalous [NII]-emission from Mz-3
Authors: Schnur G.F.O. , Kegel W.H.
Published: June 2019

We obtained high resolution spectra of the red [NII]-lines in the bipolar nebula Mz-3, This object probably is a protoplanetary nebula (see e.g. Lopez and Meaburn, 1983 and Meaburn and Walsh, 1985). The spectra were taken in July and September 1982 at La Silla using the Coudé Auxiliary Telescope (CAT) combined with the Coudé Echelle Spectrograph (CES). The resolution depending on the slit width was 30000 and 100000, respectively. Fig. 1 shows the [NII]-lines at 6583.6 and 6548.3 Å together with Hα. The structure of the 6583.6 Å line, which is quite complicated in detail, is dominated by two narrow peaks, similar to the profiles of circumstellar O H-masers. The profile varies strongly with the slit width and shows substantial differences between the observations in July and September. - The most striking result of our observations is that the intensity ratio 6584/6548 deviates strongly from the canonical value of 3 as shown in Fig. 2.
How unique is the protoplanetary nebula star HR 4049?
Authors: Waelkens C.L. , Waters L.B.F.M.
Published: June 2019

The late B-supergiant HR 4049 is peculiar in different respects: (1) It is located far from the galactic plane (b = 23°); (2) It is a variable with a large amplitude and on a long time scale (Waelkens and Rufener, 1983); (3) It has a spectacular infrared excess (Lamers et al., 1986). Two models were proposed: (i) HR 4049 is a runaway hypergiant embedded in a dust cloud, or (ii) HR 4049 is a low-mass star in a post-AGB stage of evolution. In this paper we present evidence that favours the second hypothesis. This evidence consists of new observational data on HR 4049 itself and of the discovery of a second very similar object, that is located still farther from the galactic plane.
Dust formation in M-stars
Authors: Gail H.-P.
Published: June 2019

A mechanism is proposed for the initiation of dust formation in stellar winds of M-type giants and supergiants. If Mg and Fe are ionized (M0…M4) dust formation is initiated by homogeneous nucleation of SiO, otherwise (later ≍ M2) by homogeneous nucleation of MgS. The condensation temperatures for these mechanisms agree well with observations.
Possible rôle of the white dwarf in grain formation in CV systems
Authors: Albinson J. S. , Evans A.
Published: June 2019

Zhilyaev & Zubko described white dwarf model atmospheres in which carbon might condense. Whittaker2 presented a version of the phase diagram for carbon on which there is a region where carbyne is thermodynamically favoured over graphite. Because the ratio of cross-section to mass is much higher for a thin cylinder, a carbyne cylinder has a much better chance of being blown out of a white dwarf atmosphere by radiation pressure. However even for small grains, gravity overcomes radiation pressure for cylinders, as it does for spherical grains. In the case of a non-polar cataclysmic variable (CV) system, the white dwarf is surrounded by an accretion disk and the luminosity of the disk may provide sufficient additional radiation pressure to drive a grain out of the system. If a grain can initially be transported out of the white dwarf atmosphere there may be several CV systems in which the combined radiation pressure of the disk and white dwarf can blow grains out of the system. For small grains and white dwarf masses ≳ 0.5 Mo radiation pressure can overcome gravity. These remarks also apply to grains that originate in the cooler regions of the disk, where the density may be high enough to sustain grain formation. Thus some non-polar CV systems may possess circumstellar dust shells, whose composition may reflect the nature of the white dwarf or secondary. For cases in which grains originate in the disk any circumstellar dust may be transient, as the mass transfer varies. Furthermore, in classical nova systems, this process may provide grain precursors, on which larger grains might grow during a noya outburst. A more complete discussion may be found in Albinson & Evans.
Circumstellar chemistry of cool evolved stars
Authors: Glassgold A. E. , Mamon G.
Published: June 2019

A status report is given of the continuing development of the photochemical model for circumstellar envelopes around cool evolved stars, with emphasis on molecular ions in both O-rich and C-rich envelopes.
The chemistry of cool circumstellar envelopes
Authors: Nejad L.A.M. , Millar T. J.
Published: June 2019

We have developed a time-dependent chemical kinetic model to describe the chemistry in the circumstellar envelopes of cool stars, with particular reference to IRC + 10216. Our detailed calculations show that ion-molecule reactions are important in the formation of many of the species observed in IRC + 10216.
Circumstellar matter, with particular reference to jets and molecular flows
Authors: Kahn F. D.
Published: June 2019

Circumstellar matter exists in many forms, such as winds from early and from late type stars, in infra-red sources and OH and H2O masers, in X-ray sources and jets, and molecular flows and Herbig-Haro objects. There is considerable diversity in the nature of the starlike bodies that underlie these phenomena. Here an attempt is made to trace the connection between some of the observations related to pre-main sequence stars and their surroundings, with emphasis on jets and molecular flows.
A Few Remarks on the Two Types of Pulsars
Authors: Deng Z.-G. , Huang J.-H. , Xia X.-Y.
Published: June 2019

Huang et al have classified pulsars into two types according to the role played by the superfluid neutron vortexes in the interior of neutron stars. They have also presented the formule of P for these two types of pulsars. In this short remark, we shall compare the conclusions about the evolutions of these two types of pulsars with the observational distributions. The consequences obtained are summarized as follws.
Toward an Empirical Theory of Pulsar Emission
Authors: Rankin Joanna M.
Published: June 2019

Polarized, pulsar profiles consist of two distinct types of emission units, core and conal components. Various configurations of these two basic units then underlie the 5 principal species of profile: conal and core single, conal double, triple, and multiple (5 comp.) profiles. Conal single profiles typically evolve through bifurcation into conal double forms at low frequency; whereas core single profiles evolve into triple forms at high frequency by adding pairs of conal “outriders”. Conal components and outrider pairs exhibit polarization properties compatible with a hollow-conical emission zone which spreads weakly at low frequency. The central core components in each profile species, by contrast, often exhibit circular polarization of symmetrically alternating sense. The triple profile is then most generally prototypical of pulsar emission, and the physical distinction between its outriding conal components and its central core emission feature are primary–implying two distinct corresponding radiation mechanism. (Ap. J. 274, 333/359).

The isolated core components of stars with core single profiles exhibit little ordered modulation, nor do they null or evince of any sort of mode changing; many have featureless fluctuation spectra, while others exhibit low-frequency (P3 = 15–50 periods/cycle) features with which no orderly “drift” is apparently associated. The core components in triple, double (“saddle” region), and multiple profiles also exhibit these stationary, low-frequency fluctuations. “Drifting” subpulses are then an exclusively conal phenomenon. Systematic subpulse modulation (P3 = 2–15 periods/cycle) is associated with the conal components of stars with double, triple, and multiple profiles, but progressive, orderly drifting is observed only in conal single stars. The ensemble P3 values associated with the conal components of the various profile species seem indistinguishable, again suggesting that these species are geometry-specific manifestations of a single physical configuration. Mode changing and pulse nulling are exclusively associated with neither core nor conal emission, but rather connect the two. Mode changing is typically manifest as a reorganization of the conal constituents of emission about the profile's core component. Finally, pulse nulling is not so closely associated with spindown age as has been thought. Pulsars which null are members of older profile species to be sure, but within a given species, those stars which null are no older than those that do not. (1986 Ap. J. 301, 901)
Pulse Asymmetry of Millisecond Pulsars
Authors: Chen Kai You , Shaham Jacob
Published: June 2019

By considering a simple model of slowly rotating neutron stars (for which the Schwartzschild metric could be used properly) whose emission is confined to circular antipolar caps, Pechenick, Ftaclas and Cohen (1983) studied the gravitational effects on the light curves. They found that for typical neutron star parameters, the light curves flattened out due to the bending of light in the neutron stellar gravity.
Polarization Angle Swings Rediscussed
Authors: Sieber W.
Published: June 2019

The polarization angle swing observed in some pulsars, e.g. PSR 0833-45, may be understood as the pattern which results when our line of sight cuts through the magnetic dipole field of a pulsar. In such a geometry the polarization angle χ is a function of μ, the angle between rotation axis and magnetic field axis and Δ, the angle between magnetic field and line of sight to the observer.
Neutron Star Coupling to its Environment
Authors: Salvati Marco , Pacini Franco
Published: June 2019

We review facts, myths and theories related to the formation of neutron stars and their coupling to the environment.
The Progenitors of Pulsars
Authors: Srinivasan G. , Bhattacharya D.
Published: June 2019

The progenitors of single as well as binary pulsars are discussed with special emphasis on binary pulsars with low mass companions. Several predictions are made concerning millisecond pulsars.
The Evolution of Young Supernova Remnants
Authors: Dickel John R. , Jones Eric M. , Eilek Jean A.
Published: June 2019

The remnants of the Kepler's and Tycho's supernovae show a thick shell structure with a sharp outer edge and significant brightness irregularities. Models of their expansion have been constructed using a one-dimensional spherical hydrodynamics code, which includes both a leading shock and a reverse shock moving back into the ejectum. The dynamics are controlled by conditions between these shocks. Synchrotron radio emission is produced by acceleration and amplification of initial relativistic particles and fields by eddy motion at the interface between the ejected and swept-up material and at the boundaries of clumps in the surroundings with a mean separation of 5×1017 cm, Gaussian sizes of 1×1017 cm and peak densities of 3.6×10−24 cm−3. The latter was typically 10 times the mean density between clumps. A net radial orientation of the magnetic fields is attributed to stretching by Rayleigh-Taylor instabilities at the contact surfaces. To simulate true three-dimensional structure with the one-dimensional model, random contributions from four runs with varying spacings for the clumps were summed along the line of sight. The results are shown in the figure. Without clumps the observed shell is much too narrow and steep on the inside. Whether the clumpiness is a result of presupernova mass loss or a general property of the interstellar medium is not known.
Supernova Remnants in the Magellanic Clouds Observed at the Molonglo Observatory
Authors: Turtle A.J.
Published: June 2019

Radio surveys of the Magellanic Clouds at 843 MHz have been made with the Molonglo Observatory Synthesis Telescope. An initial catalogue (Mills et al. 1984) presented details of 38 supernova remnants detected by a combination of X-ray, optical and radio observations. The subsequent completion of the radio survey has revealed at least a further 17 remnants, mainly of large diameter and undetected by the Einstein X-ray Observatory. Though a few remnants have their radio emission concentrated towards their centre there is no evidence in the Magellanic Clouds for a Crab-like plerion (without an associated shell). The two well-established plerions 0540-693 (with optical and X-ray pulsar) and 0538-691 (N157B) appear to be connected with partial shells of strong radio emission which are relatively weak in optical emission lines (0538-691 is superposed on an HII region). Four sources which have a central concentration show larger optical and X-ray shells. The optical spectra of three of these (0505-679, 0509-675 and 0519-690) are dominated by the emission lines of hydrogen and Tuohy et al. (1982) argue that they are remnants of Type I supernovae. The fourth source (0453-685) which has detectable [OIII] emission may be an older but similar type of remnant. A further remnant 0509-687 (N103B) is compact but its radio diameter of 6 pc agrees with the published X-ray result.
The X-ray Transient EXO 2030+375
Authors: Parmar A.N. , White N.E. , Stella L. , Ferri P.
Published: June 2019

EXOSAT has observed a bright transient X-ray pulsar EXO 2030+375 that decayed in intensity by a factor ∼5000 between 1985 May and August. The variations in 42s pulse period enable an orbital period of 37.9±1.3 days with an eccentricity of 0.31±0.02 to be determined. The spin-up timescale of ∼30 years suggests that this is a very large outburst of order a few 1038 ergs/s. The mass function of 5Mo is consistent with the unidentified companion being a Be star, similar to many other pulsing X-ray binaries. The position of EXO 2030+375, obtained with the EXOSAT Imaging Telescope, is RA: 20 30 21.25, Decl. +37 27 51 (1950; with an uncertainty radius of 10″).