bluuebunny/crossref_metadata_2025 huggingface dataset:
The Transputer Based CCD Controller at ESO
Authors: Reiss Roland
Published: June 2019

A new controller concept based on transputer modules (TRAMs) and Digital Signal Processors (DSPs) has been developed at ESO. The Array Control Electronics (ACE) can handle single CCDs or CCD mosaics with 1 to 64 outputs and with up to 256 clocks with software programmable independent high and low voltages. The same basic concept will be used for slow scan scientific and fast scan auto guiding/wave front sensing applications. While the transputers are mainly used for data acquisition, communication and supervisory tasks, a DSP with very simple external logic performs the time-critical CCD clock pattern generation. The low noise, high speed clock driver with built-in telemetry is designed for highest operational safety. A newly designed video processor board has four video channels each with its own 16-bit ADC. ACE can easily be interfaced to various types of host computers like PCs, Unix workstations or ESO's VME-based LCUs (Local Control Units with VxWorks real-time operating system).
CCD Imagers by Enhanced UV Sensitivity for Industrial and Scientific Applications
Authors: Vishnevsky G. I. , Vydrevich M. G. , Lazovsky L. Yu. , Kossov V. G. , Tatautshchikov S. S.
Published: June 2019

A family of virtual phase (VP) CCD array image sensors for various industrial and scientific applications has been designed, fabricated and tested. All share the common concept of a “2.5-phase” photosensitive cell, combining the advantages of known “1.5-phase” VP devices (increased quantum efficiency, especially in the UV, and radiation hardness) with the simpler fabrication process and extended functionality of three-phase devices.
Intensified Electron-Bombarded CCD Images for Industrial and Scientific Applications
Authors: Dalinenko I. , Vishnevsky G. , Kossov V. , Lasovsky L. , Kuzmin G. , Malyarov A.
Published: June 2019

Electron-Bombarded CCD (EB-CCD) image intensifiers, based on the primary photoelectron multiplication effect in the CCD substrate, provide a number of advantages over routine intensified CCDs, optically coupled with the output of conventional image intensifiers. Despite this fact, there are no commercially available intensified EB-CCD imagers, though many CCD and image intensifier's manufactures put great efforts to design devices of such kind. This paper briefly reviews the results of more than a decade of work in the field of intensified EB-CCD imaging devices in the “Electron” National Research Institute, Russia's leader in optoelectronics.
Patchy Reconnection and Magnetic Ropes in Astrophysical Plasmas
Authors: Russell C. T.
Published: June 2019

Reconnection is clearly observed at the terrestrial magnetopause but seldom in the simple geometry originally proposed. Most often reconnection is patchy, forming tubes of twisted flux. The passage of one of these twisted tubes has been called a flux transfer event. Similar twisted tubes, or flux ropes, are formed at Venus by velocity shear. These tubes become so highly twisted that they become kink unstable. The presence of the kink instability suggests a way of creating compound flux ropes as have been postulated to be necessary to explain photospheric magnetic structure.
Quasi-Two-Dimensional Cosmic Jets
Authors: Tsinganos K. , Ferrari A. , Rosner R.
Published: June 2019

One of the major discoveries in solar physics over the past decade has been the association of coronal holes with high-speed solar wind streams (Zirker 1977 and references therein). On the other hand, advances in X-ray and radio instrumentation (e.g., Einstein, VLA, VLBI, etc.) in the past few years have allowed detailed observations of collimated outflows from rather more distant objects, such as young stars and active galaxies (Beer 1981, Lada 1982, Ferrari and Pacholczyk 1983 and references therein). The remarkable structural similarities between jets of magnetized gas from our Sun, other active stars, and active galactic nuclei suggest that these phenomena may be manifestations of similar hydrodynamic processes operating on both small and large scales. In this article, we shall use the experience gained by studying the nearest known astrophysical jet - high-speed solar wind streams - to address some of the problems of astrophysical jet acceleration and collimation associated with objects as diverse as SS 433, star-forming molecular clouds and, in particular, jets associated with galaxies and quasars.
Perspectives on Space and Astrophysical Plasma Physics
Authors: Kennel C. F. , Arons J. , Blandford R. , Coroniti F. , Israel M. , Lanzerotti L. , Lightman A. , Papadopoulos K. , Rosner R. , Scarf F.
Published: June 2019

We summarize the discussion of the current status and future prospects of space and astrophysical plasma research prepared by the Panel on Space and Astrophysical plasmas, a part of the study on Physics administered by the National Research Council of the National Academy of Sciences. The Study on Physics is chaired by W. Brinkman of Bell Laboratories and will be completed in 1984.
Statistical Analysis of Proper Motion Surveys
Authors: Hanson Robert B.
Published: June 2019

Proper motion surveys offer a great deal of data bearing on important astronomical problems such as stellar kinematics and the luminosity function in the solar neighborhood. Major obstacles to the full use of proper motions have long been posed by: (1) incompleteness of proper motion surveys, (2) proper motion bias in kinematic studies, and (3) the indirect approaches and kinematical assumptions needed in traditional luminosity studies.
The Conversion from the B1950 FK4-Based Position to the J2000 Position of Celestial Objects
Authors: Aoki S. , Sôma M. , Nakajima K. , Niimi Y. , Fujishita M. , Takahashi Y.
Published: June 2019

We present here the fundamental idea of the conversion method between old and new reference frameworks. Some practical applications are made for the optical observations for Tokyo PZT. The method can be also applied to the conversion of radio sources where we have met a great difficulty in performing the conversion because of no citation of observation epochs in general. We discuss their necessity in order to establish a concrete compilation of the position of the radio sources.
Proper Motions with Respect to Galaxies
Authors: Klemola A. R.
Published: June 2019

The Lick proper motion program with respect to galaxies is summarized. The subject of extragalactic astrometry is introduced with estimates of proper motions for selected members of the Local Group of galaxies and more distant systems. The problems of measuring proper motions for the Magellanic Clouds is described in more detail.
Vidicon Photometry and Astrometry Applied to Objects of the Solar System
Authors: Arlot J.-E. , Thuillot W.
Published: June 2019

A SIT-Vidicon camera has been used for astrometric and photometric observations: phenomena of the Galilean Satellites, occultations of stars by asteroids and comets, closest approaches of fast moving objects. This paper tries to give a preliminary evaluation of the efficiency of these observations.
Vacuum Meridian Marks of the Belgrade Large Transit Instrument
Authors: Mitic L. A. , Pakvor I.
Published: June 2019

More than a dozen years ago vacuum meridian marks were built for the Belgrade Large Transit Instrument with the purpose of completely keeping the air from interfering with the meridian mark readings. Information is presented on the favorable results achieved as regards both accidental and sytematic accuracy.
The Vacuum Mires of the Transit Instrument at Nikolaev
Authors: Petrov G. M. , Fedorova R. T. , Fedorov P. N.
Published: June 2019

At Nikolaev, in 1978, a system for the improvement in the stability of the light path between the transit instrument and the meridian mires was designed. Its purpose is to improve the accuracy of the azimuth determination and that of the collimation. This system consists of twelve sections of 8 mm thick steel tube with 160 mm diameter, each nine meters long. These tubes are lying in special steel cradles which rest on brick support columns spaced 8 meters apart, and these can be moved vertically and horizontally by 100 mm and 50 mm, respectively. Thus it is possible to align the axis of the tube exactly.
Space Telescope Motion Limitations for Fine Guidance Sensor Astrometry
Authors: Fresneau Alain
Published: June 2019

Basic Fine Guidance Sensor data have been simulated to correlate the Power Spectrum Densities (PSD) of the Space Telescope motion disturbances with the “seeing” of an astrometric target. The goal of this study is to describe whether a complete identification of the jitter of the line of sight during an astrometric observation is required to improve the precision of this observation. The present preliminary results indicate that the performance in Astrometry are close to the predictions.
Astrometric Desiderata for Nearby Stars
Authors: Gliese Wilhelm
Published: June 2019

Astrometric desiderata for nearby stars concern, in first line, the parallax measurements, avoidance and elimination of effects of bias in trigonometric parallax programs: Bias towards large proper motions, preference of parallaxes with positive accidental errors, the Malmquist bias. For some of the nearby stars we do not yet know accurate positions, for some other objects no reliable proper motions were measured. Finally, for calibrating color-luminosity relations the necessity to observe further precise trigonometric parallaxes is demonstrated and emphasized.
The Preparation and Distribution of Machine-Readable Astrometric Data
Authors: Warren Wayne H.
Published: June 2019

The acquisition, preparation and distribution of machine-readable astrometric data by the Astronomical Data Center (ADC) are described. Examples of certain general changes in data structure and format to improve compatability with other computers and software processing systems and to increase storage efficiency are discussed, as are the present data archive and request history of the ADC. Current development work in the areas of astrometric and positional catalogs is described.
On the Feasibility of a Star Coordinate Determination in the Radio Astrometry Reference System
Authors: Gubanov V.S.
Published: June 2019

At present it is evident that the stability of a celestial coordinates system with an accuracy of at least per century, with respect to an internal frame can be derived only from VLBI observations of compact extragalactic radio sources. At the same time it is expected that the need for improved stars' coordinates will be strongly felt at least up to the end of this century, because stars are important and more convenient observational objects then very weak extragalactic sources or artificial Earth satellites (AES). One therefore wonders if one can use the high precision and stability of the radio astrometric reference frame to stabilize and improve the reference frame given by star catalogues. The problem of the relationship between these systems has so far been investigated in the form of determining the parameters of their mutual orientation, and/or studying systematic errors of star catalogues (Gubanov, 1978; Gubanov and Kumkova, 1978, 1981). This problem has been attacked by direct photography of several optically identified radio sources or VLBI observations of few radio stars. The present paper shows the feasibility of determining the place of any star of sufficient magnitude with reference to the radio astrometric frame, as given by extragalactic source positions (Gubanov, 1983). This is done by introducing an AES, equipped with radio signal for VLBI observations and a corner reflector for laser ranging, which can be observed by radio methods as well as optically (Gubanov, 1976). This satellite should also be bright enough in the reflected sun's light to be observed in the star field with a precision photoelectric satellite camera.
Hot Spots in Compact Sources
Authors: Menon T. K.
Published: June 2019

The low-frequency turnover of a selected sample of quasars is found to be strongly correlated with their redshift (Menon 1983)). Assuming that the components which produce the low-frequency turnover are hot spots in the quasars I have derived the physical parameters of the hot spots and show that there is a continuity in the various parameters as the angular sizes of the hot spots vary from subarcseconds to milliarcseconds. Hence the low-frequency turnover can be used as a probe into the physical conditions at the earliest phases of quasar activity.
EVN Observations of Compact Steep Spectrum Radio Sources at 18 cm
Authors: Fanti C. , Fanti R. , Parma P. , Schilizzi R.T.
Published: June 2019

We consider the compact (≲ 2–4 asec) radio sources in the 3CR catalogue with normal (α ≲ 0.5) straight spectrum and low frequency (νc≲ 200 MHz) turnover. The curvature in the spectrum, if due to synchrotron self-absorption, implies structures of the order of tenths of an arcsec, while its straightness at high frequencies suggests that no dominant very compact (∼1 mas) feature is present. The radio sources matching the above requirements are listed in the Table. The sample is probably not complete but it is representative of the class.
The Radio Core of Markarian 348
Authors: Neff S. G. , de Bruyn A. G.
Published: June 2019

The type 2 Seyfert galaxy Markarian 348 (NGC 262) is a normal early-type disc galaxy (SO/a or Sa) surrounded by a very large HI envelope. The continuum radio source in the galaxy is unresolved by conventional interferometers on scales as small as an arcsecond, is variable on time scales of a few months, and is quite strong by Seyfert standards (300 mJy). Mkn 348 is relatively nearby, allowing one to study very small-scale structure in the galaxy (at the assumed distance of 60 Mpc (Ho = 75 km/sec/Mpc), one light year subtends an angle of about one mas). Both the relative proximity and the radio source strength make it a good candidate for VLBI studies.
Radio Astrometry
Authors: Johnston K. J.
Published: June 2019

Radio astrometry is now the premier astrometric technique for measuring the positions of celestial objects. The precision with which absolute positions can be determined is approaching a few milliarc-seconds. The progress towards establishing an almost inertial reference frame based upon the positions of extragalactic radio sources is reviewed as of June 1983. The outlook for relating this reference frame to optical reference frames is also reviewed.
White Dwarf Candidates for Trigonometrical Parallax Determinations
Authors: Moffett T. J. , Barnes Thomas G. , Evans David S.
Published: June 2019

The visual surface brightness relation is applied to the determination of parallaxes of white dwarfs on the assumption, borne out by previous studies of white dwarfs of known parallax, that these show only a small range of linear diameters.
The Absolute Dimensions and Masses of IQ Persei
Authors: Lacy Claud H.
Published: June 2019

High signal-to-noise ratio spectrometric observations of the large light-ratio eclipsing binary IQ Per (B7 + A2) have been obtained with the coudé Reticon spectrograph of the 2.7 m reflector at McDonald Observatory. Absorption lines of the secondary are seen at the 4481 Å MgII line and the 4549 Å TiII + FeII blend. Radial velocities of both components have been measured by cross-correlation techniques and spectroscopic orbits have been computed. The fitted orbits have an eccentricity (0.075 ± 0.007) that is consistent with the photometric orbit of Hall, Gertken and Burke (1970). Young's (1975) “provisional” estimate of K2 is about 14% too small. Absolute dimensions and masses have been computed from Hall et al.'s (1970) photometric orbit and the new spectroscopic orbit. Additionally, V-R photometric observations obtained by M. Frueh at McDonald Obs. have been analysed by Popper with light curve synthesis techniques (WINK and EBOP). The relative radii of the new photometric orbits differ by less than 2% from the previous orbits, and the other orbital elements also show excellent agreement. The absolute dimensions and masses are (3.51 ± 0.04m⊙, 2.46 ± 0.04 R⊙) for the primary and (1.73 ± 0.02m⊙, 1.50 ± 0.03 R⊙) for the secondary. Both stars are near the zero-age main sequence. The value of ω has changed significantly between the epoch of Hall, Gertken, and Burke's (1970) observations and my own due to apsidal motion. The apsidal motion period is estimated to be in the interval 90 ≤ τ ≤ 180 yr.
UV Spectral Classification of B Stars
Authors: Rountree Janet , Sonneborn George , Panek Robert J.
Published: June 2019

Previous studies of ultraviolet spectral classification have been insufficient to establish a comprehensive classification system for ultraviolet spectra of early-type stars because of inadequate spectral resolution. We have initiated a new study of ultraviolet spectral classification of B stars using high-dispersion IUE archival data. High-dispersion SWP spectra of MK standards and other B stars are retrieved from the IUE archives and numerically degraded to a uniform resolution of 0.25 or 0.50 Å. The spectra (in the form of plots or photowrites) are then visually examined with the aim of setting up a two-dimensional classification matrix. We follow the method used to create the MK classification system for visual spectra. The purpose of this work is to examine the applicability of the MK system (and in particular, the set of standard stars) in the ultraviolet, and to establish classification criteria in this spectral region.
Spectral Anomalies in the Hyades and Pleiades and in Field Stars with Active Chromospheres
Authors: Rose James A.
Published: June 2019

Widened photographic image-tube spectra at 50 Å mm−1 dispersion have been obtained for a large number of late-type field dwarfs and giants with well-determined atmospheric parameters and for 35 Hyades dwarfs and 31 Pleiades dwarfs. The spectra have a resolution of 2.5 Å and cover the wavelength range λλ3400–4500 Å. A new quantitative three-dimensional spectral classification system is derived for late-type stars and is calibrated using the sample of field dwarfs and giants with known atmospheric parameters. Diagnostic indices are defined by comparing the counts in the bottoms of two neighboring absorption lines or by comparing the counts in two neighboring pseudocontinuum peaks.

It is found that the Hyades and Pleiades dwarfs and field dwarfs with strong Ca II H and K emission reversals exhibit well-defined anomalies in their diagnostic indices when compared with normal field dwarfs. These results are summarized in Rose (1984). In LaBonte and Rose (1984), it is shown, from spectra of solar magnetic plages, that all spectral and photometric peculiarities of the Hyades discovered to date, including the original “Hyades anomaly” (Crawford 1969; Strömgren et al. 1982), are manifestations of plage activity.
About the Photometric Calibration of IUE High Resolution Spectra: Quantification of the Order Overlap for the SWP Camera
Authors: Bianchi Luciana , Bohlin Ralph
Published: June 2019

In order to quantify the errors in the IUE line profiles caused by the order overlap, we have compared line depths in IUE and Copernicus spectra. The excess line depth in IUE spectra suggests that the amount of order overlap is about 32% at 1150Å and decreases to zero at about 1400Å, for spectra extracted with the recent version of IUESISPS (the IUE standard extraction software). The transfer of a spectral feature from one order to the next is below the 5% level.

Based on these results, a correction technique is described.
On the Observational Determination of OB Standards
Authors: Krełowski J. , Strobel A.
Published: June 2019

Observational evaluation of intrinsic energy distributions in OB spectra is difficult as these stars are usually reddened and any dereddening procedure may change from place to place in the Galaxy. We compare two-color diagrams (UV vs. visual) from two stellar complexes of the same Sp/L class. The observed differences may be caused by additional far-UV reddening of distant objects as well as by intrinsic differences between stars belonging to different complexes. We argue in favor of the first possibility which would allow one to use the same standards in all of the Galaxy.
The Zero-Point of the IAU Standard Velocity System
Authors: Scarfe C. D.
Published: June 2019

Radial velocities of bright IAU standards have been obtained photographically over the past decade using the long camera of the DAO 1.2 meter telescope's coudé spectrograph. Most of the stars observed have been found to be constant in velocity to better than 0.15 km/s over that interval. The mean velocities agree with the IAU velocities, on the average, within 0.10 km/s, although mean velocities of some individual stars differ considerably more than this from the IAU value. A preliminary determination of the zero point of the long camera system, and hence of the IAU system, has been made from observations of the asteroid Vesta, whose actual radial velocity has been calculated from its orbital elements.
The Calibration of Stellar Spectra Used in Measurements of the Generalized Compton Shift
Authors: Missana M.
Published: June 2019

In the study of the changes induced by the Compton effect and Thomson scattering on the shape of spectral lines in light traversing a chromosphere or a planetary nebula it is necessary to have accurate wavelength measurements, central intensities and half widths (FWHM) of the lines. In the comparison of FWHM measures belonging to different spectra it is useful to have the intensities of the continuum at the wavelengths of the lines. The studied spectra should have a dispersion higher than 10 Å/mm and a spectral range larger than 700 Å. A short recommendation is also given about the comparison spectrum and the calibration plate.
Optical and Ultraviolet Absorption Studies of Cool Gas in the Milky Way Halo
Authors: Danly L.
Published: June 2019

Of the many and various means for observing the interstellar medium, and halo gas in particular, optical and ultraviolet absorption techniques provide both unique opportunities and unique limitations. As its title indicates, this article speaks specifically to the contributions from absorption methods to our knowledge of halo gas with temperatures below 105K. A brief description of the trade-offs and benefits of the methods is therefore useful to set the stage for interpreting the observations of halo gas.
Diffuse Ionized Gas in Nearby Galaxies
Authors: Walterbos R.A.M.
Published: June 2019

We discuss the distribution and spectral characteristics of diffuse ionized gas in nearby galaxies. The existence of this elusive component of the interstellar medium (ISM), also referred to as the Warm Ionized Medium, is by now well established from deep imaging and spectroscopic surveys in several emission lines in external galaxies. Diffuse ionized gas is characterized by a relatively high ratio of [SII] over Hα intensities, typically twice as high as for discrete HII regions. The diffuse gas has been mapped in both edge-on and more face-on galaxies providing information on the radial and vertical distribitions. Emission from diffuse ionized gas is strongest around star forming regions. The vertical distribution appears related to the radio continuum thick-disk emission. We also briefly discuss ionization mechanisms, and the connection between star formation characteristics and morphology of the interstellar medium.
Synchrotron Emission as a Tracer of the Outflow in M82
Authors: Seaquist E.R. , Odegard Nils
Published: June 2019

We report the discovery of radio synchrotron emission from the outflow in M82. The brightness morphology and radio spectral index distribution add new insights into the physical processes and origin of the wind, which are briefly discussed in this paper.
Positronium in Astrophysical Condition
Authors: Burdyuzha V.V. , V.L. Kauts , N.P. Yudin
Published: June 2019

From a physical point of view we analyzed the possibility of observation of the Lα-line of the positronium (Ps). In a broad range of temperatures the processes of recombination to states of Ps with different nl, collisions of Ps with electrons and protons of medium are examined.
Advancement of Photoionization and Photodissociation Rates Relevant to Astrochemistry
Authors: Tarafdar S P
Published: June 2019

The advancement of photoionization and photodissociation rates relevant for interstellar diffuse and dense clouds, circumstellar medium, cometary coma and planetary atmosphere has been reviewed with a mention of uncertainties involved in these rates.
Chemistry in the Early Universe
Authors: Shapiro Paul R.
Published: June 2019

Galaxies and the first stars in the universe formed billions of years ago as a result of the cooperative effects of gravitational collapse and nonequilibrium chemistry. Gravity drew the primordial gas together into lumps; the formation of the first molecules in the universe, simple diatomic molecules like H2, H2+, HD, HeH+, LiH, and LiH+, may then have ensured that the heat generated by gravitational collapse and shock waves was radiated away rapidly enough to allow the gravitational collapse and fragmentation of these gaseous lumps to proceed to the point of forming stars and galaxies. We briefly mention a few of the latest studies of this primordial chemistry, including that in the evolving intergalactic medium (IGM) in a Cold Dark Matter (CDM) model cosmology and that in radiative shocks in the early universe.
The Interstellar C-H Stretching Band Near 3.4 μm: Constraints on the Composition of Organic Material in the Diffuse ISM
Authors: Sandford S. A. , Allamandola L. J. , Tielens A. G. G. M. , Sellgren K. , Tapia M. , Pendleton Y.
Published: June 2019

The spectra of objects suffering extinction by diffuse interstellar dust contain a broad feature centered at ~3300 cm−1 (~3.0 μm), attributed to O-H stretching vibrations, and/or a feature near 2950 cm−1 (3.4 μm) attributed to C-H stretching vibrations. The 2950 cm−1 feature can be attributed to C-H stretching vibrations in the -CH2- and -CH3 groups of a fairly complex carbonaceous material containing aliphatic functional groups.
Are Carbon Clusters the Cause of Interstellar Diffuse Bands?
Authors: Tarafdar S P , Krishna Swamy K S , Badrinathan C. , Mathur D.
Published: June 2019

Theoretically determined vertical excitation energies of C5 and C7 molecules have been shown to agree with the strongest diffuse interstellar band at 4430Å. Several other weak diffuse bands can be identified with vibrational transitions, if 4430Å band is taken as 0-3 transition and vibrational constant have a value of 2190cm−1. The vertical excitation energy of a second electronic transition of C7 molecule agrees with diffuse band at 6177Å. This electronic band system may account for diffuse bands at 5778Å, 6660Å and other bands near them.
Diffuse, Translucent & High-Latitude Clouds: Theoretical Considerations
Authors: Van Dishoeck E.F.
Published: June 2019

The relative importance of gas-phase, shock and grain-surface chemistry is discussed with reference to recent observational data. The relation between diffuse, translucent and high-latitude clouds is illustrated with models in which carbon is transformed from atomic (C+, C) to molecular (CO) form with increasing extinction.
Interpretation of the level population distribution of highly rotationally excited H2 molecules in diffuse clouds
Authors: Wagenblast R.
Published: June 2019

The observed H2 level population distribution of the rotational levels J = 5, 6 and 7 in the ground electronic and vibrational state X(v = 0) is analysed using available Copernicus data (Spitzer and Morton, 1976) for the diffuse clouds toward the stars ζ Oph, δ Per and ξ Per. The abundances of H2 in these high purely rotationally excited energy levels are due to the influence of one or more of three possible excitation mechanisms: collisions with abundant particles (e.g. H atoms and H2 molecules), UV-photoexcitation and H2 formation.
Hot Cores and Cold Grains
Authors: Walmsley C. M. , Schilke P.
Published: June 2019

A review is given of the evidence for depletion of heavy elements in dense molecular cloud clumps onto dust grain surfaces. Particular attention is given to the recent controversy over the nature of the dense clumps in NGC 2024. We also discuss recent ammonia observations of“hot core” regions and evidence that the NH3 abundance is greatly enhanced.
CH+in Shocks, Cloud-Intercloud Interfaces, and Dense Photodissociation Regions
Authors: Duley W W , Hartquist T W , Sternberg A. , Wagenblast R. , Williams D A
Published: June 2019

Substantial CH+abundances are found in at least three types of environment (Lambert and Danks, 1985): atomic regions with little H2, N(CH+) ~ 1012cm−2; diffuse clouds such as that toward ζ Oph, N(CH+) ~ 1013cm−2; reddened (2 ≲ Av≲ 4) lines of sight to bright stars N(CH+) ~ 1014cm−2. We explore the view that several different mechanisms operate.
Results of the Monitoring of a Very Strong Water Maser Event in W49N
Authors: Scalise E. , Pacheco G. M. , Gómez Balboa A.M. , Abraham Z.
Published: June 2019

Since the discovery of the 616-523 rotational transition of interstellar water in maser emission, several hundred sources have been discovered. Their profiles are very variable, presenting correlated variability (Gammon, 1976) or anticorrelated variability (Cesaroni, 1990). Several models have been proposed to explain this variability. Strong Galactic masers, such as W49 and W51 (Kylafis et al. 1991), and also an extremely strong outburst detected by Abraham et al. (1981) in Orion, could not be fully explained based on current models. We have monitored from October 1989 to July 1991 a very strong water vapour eruption in the +28 km s−1 feature, originated from W49N. Here we present the results and discuss the possible correlated variability of this feature with the one that appeared at +62 km s−1.
Silicon Monoxide in Supernova SN1987A
Authors: Smith Craig H. , Aitken David K. , Roche Patrick F.
Published: June 2019

The 8.1 μm Δv = 1 emission band of silicon monoxide detected in SN 1987A is modelled. Near day 500 the SiO mass is 4 ± 2 10−6M⊙ and the excitation temperature is ~1500 K. The mass of SiO is about 10 percent of the mass of dust inferred from the mid infrared emission near day 600, while the temperature is close to the condensation temperature of silicate grains. The SiO molecules may have been precursors to dust grain formation.
The Cosmic-Ray Ionization Rate
Authors: Lepp Stephen
Published: June 2019

A wide variety of molecules have been observed in the interstellar clouds. They are believed to be formed by reaction networks which begin with ionization by cosmic-rays. Cosmic-rays are also an important heating mechanism for many astrophysical regions. In this paper I shall review the methods used to infer the cosmic-ray ionization rate and the values which have been measured.
Planetary Rings: Observational Constraints and Collision Dynamics
Authors: Brahic André , Ferrari Cécile
Published: June 2019

Since fifteen years, space and ground-based observations have completely renewed our image of planetary rings. Simultaneously, a wealth of theoretical and numerical models have flourished. Collisions between ring's particles and gravitational perturbations of nearby satellites should explain most of the ring's structures. However, important questions are still unanswered. We do not understand why the rings are so dissimilar. We do not know the ring's origin and their stability over billions of years. Most of the ring's complex structures, the existence of arcs, and color and optical depth variations are not yet explained. Among all the ring mysteries, the uniform precession of narrow ringlets and the azimuthal brightness asymmetries should receive a high priority.
Binary Asteroids: Secular Perturbations
Authors: De Moraes R. Vilhena , Winter S. M. G.
Published: June 2019

The motion of two small bodies orbiting each other whose barycenter is orbiting around a massive body is studied. The equations of motion are integrated considering the secular part of the disturbing function.
Krein Stability in the Disturbed Two-Body Problem
Authors: Cordeiro R. R. , Martins R. Vieira
Published: June 2019

We present a method for the study of the Krein signature in perturbed Hamiltonian integrable systems. The method is developed up to first order in the small parameter. We apply this method to a particular instance of the two-body problem in which the semi-major axis is not affected by the perturbation.
Neutral Hydrogen Associated with the Planetary Nebula NGC 6302
Authors: Rodríguez L.F. , Moran J. M.
Published: June 2019

Observations of HI in absorption made with the Very Large Array towards the thermal radio emission of the planetary nebula NGC 6302 show two velocity components at 6 and −40 km s−1 (radial velocity with respect to the local standard of rest). The 6 km s−1 component is almost certainly due to a line-of-sight cloud, but the −40 km s−1 component is most probably associated with NGC 6302. We interpret this absorption component as coming from the neutral, outer part of an expanding (~ 10 km s−1) ring whose inner part is ionized and produces the thermal continuum. The mass in atomic hydrogen of the outer (neutral) part of the ring is ~ 0.06 M⊙. NGC 6302 is in an evolutionary stage intermediate to those of protoplanetary nebulae such as GL 2688 and evolved planetary nebula such as NCG 7293. This is the first detection of neutral hydrogen associated with a planetary nebula.
Chemical Abundance Determinations in Gaseous Nebulae
Authors: Aldrovandi Sueli M.V.
Published: June 2019

The determination of the chemical abundances in planetary nebulae and HII regions from the observed intensities of emission lines usually needs a correction for the unseen ionization stages. An empirical correction was first introduced by Peimbert and Costero (1969) as a factor ICF (ionization correction factor) which was obtained assuming that ions with similar ionization potentials are equally populated. Recently, Natta et al. (1980) discussed the problem of sulphur abundance in nebulae and proposed an ICF for sulphur which takes into account the radiation field as well as the ionization equilibrium of 0+, 0++, S++ and S+3. However they did not consider the effect of the charge exchange reactions which can be very important in determining the ionization equilibrium of the gas (Pequignot et al., 1978).
A New Planetary Nebula with Independently Determined Distance and Mass
Authors: Henize K.G. , Fairall A.P.
Published: June 2019

A low surface brightness planetary nebula with weak ring structure and a diameter 22 arcsec has been discovered in the southwest edge of the open cluster NGC 6067. A calibrated spectrum shows strong He II 4686 (80% Hβ) and an Hα/Hβ ratio of 5.8. The Hα/Hβ ratio yields c = 0.88 which corresponds to Av = 1.88. This is significantly greater than Av for the cluster (1.17) and leads to a distance for the nebula of 3370 pc assuming extinction to be uniform with distance. This leads to a radius of 0.18 pc and a mass of 0.07 solar masses (assuming ε = 0.5).
The Lynds 204 Complex: Magnetic Field Controlled Evolution?
Authors: McCutcheon W.H. , Vrba F. J. , Dickman R. L. , Clemens D. P.
Published: June 2019

The L204 dark cloud complex is a highly elongated structure stretching over 4 degrees in declination. Its total mass is 400 M⊙ with the more tenuous sections of the cloud being displaced in right ascension from the more heavily obscured parts.
Laboratory Microwave Spectroscopy of Interstellar Molecules
Authors: Saito Shuji
Published: June 2019

One of the main difficulties to identify molecular species in space has been raised by the lack of reliable spectroscopic data for various molecules, especially for chemically active free radicals and molecular ions. Some of the free radicals and molecular ions have been fundamental to the study of chemistry in space but they are too active under terrestrial conditions and are hardly produced in concentrations enough for laboratory observations. We have developed a millimeter-wave spectrometer of high sensitivity suitable for observations of transient molecules. It covers the frequency region of 30 to 410 GHz and has the sensitivity enabling us to detect molecules in a concentration of 107 molecules/cm3 (about 30 ppb). This high sensitivity is achieved by a combination of low noise and high power microwave source, low noise detector, and low loss cell in the high frequency region, assisted by a mini-computer. We have studied various diatomic and polyatomic transient species, some of which may have likely astronomical significance. They are H2D+, PO, PO2, HPO, CCO, HCCN, SiN, FeO, and CH3O.
Small Galactic Nebulae
Authors: Terzian Yervant , Turner Kenneth C.
Published: June 2019

We have performed high resolution VLA radio observations for several small H II regions, including the cluster emission nebulae S258, S255, S257, and S256. The region (PP56) between S255 and S257 at λ2 cm reveals significant flux structure close to OH, H2O and infrared emitting sources as shown in Figure 1. The flux densities and positions are indicated in Table 1. Observations of the cometary nebula PP59 (S269) also reveal similar characteristics as shown in Figure 2. These regions are considered to be active star-forming clouds. The cometary nebula PP40 was also observed and we note that its physical parameters are very similar to those of a typical planetary nebula.
The Stellar Content of SCO OB2
Authors: de Geus Eugène , de Zeeuw Tim
Published: June 2019

The study of the stellar content of nearby OB associations is important for understanding the Initial Mass Function, the study of differential age effects and for a better knowledge of the ambient radiation field, which plays an important role in the interpretation of measurements of gas and dust. Unfortunately, even for the nearest OB associations membership is known very poorly. In most cases no main sequence members of spectral type later than B5 are known. Membership determination using colour-magnitude diagrams suffers from the large intrinsic distance spread. The large angular extent on the sky of most associations makes proper motion measurements difficult to compare because of problems connecting photographic plates with different plate centers. In order to remedy this situation a consortium called SPECTER has been formed at Leiden Observatory. It has been granted observing time on the HIPPARCOS satellite for measuring proper motions of about 10000 candidate members of the OB associations within 600 pc of the Sun. Candidates were selected according to spectral type (not later than F8) apparent magnitude, and location. In anticipation of the HIPPARCOS results, SPECTER will gather a variety of other data. We have nearly completed a program aimed at obtaining VBLUW-photometry (Lub and Pel 1977) of all candidate stars visible from the Southern Hemisphere. Here we discuss the preliminary results for the association Sco OB2.
Electromagnetic Jets Driven by Accretion Disks
Authors: Kaburaki Osamu , Itoh Motoyoshi
Published: June 2019

As a model of ionized jets from young stars, an analytic solution has been derived from the resistive MHD equations. The essence of our model and an outline of the calculation are presented.
Formation of Bipolar Flows in Star Forming Regions by Stellar Winds
Authors: Hanami Hitoshi , Sakashita Shiro
Published: June 2019

It is observed that a number of large-scale supersonic bipolar flows exist in star forming regions. Infrared sources which seem to excite active motions are usually found in the center of these objects (cf. the recent surveys by Bally and Lada 1983, Torrelleset al.1983, Snellet al.1984, Goldsmithet al.1984). From the observation of the high density gas, the bipolar flow seems to originate from the interaction of the isotropic stellar wind with a large scale flattened interstellar cloud from which the protostars are formed.
The Structure of the Interstellar Medium and Star Formation in the Magellanic Clouds
Authors: Dopita Michael A.
Published: June 2019

The Magellanic Clouds, by their proximity, offer a unique opportunity to study the detailed processes of star formation in a galactic context. This Review examines the dynamic and self-limiting feedback between star formation and the interstellar medium (ISM) in these galaxies. Energetic processes associated with star formation are responsible for pressurising the ISM, for maintaining the multi-phase structure of this medium and for ejecting copious quantities of both hot and cool gas to large heights above the galactic mid-plane. This circulation process determines the control of the star-formation rate.
CO Observations of the Central Bar of M83
Authors: Handa T. , Sofue Y. , Nakai N. , Fujimoto M. , Hayashi M.
Published: June 2019

CO observations of the nuclear region of the SABc galaxy M83 have been made with the 45-m telescope at NRO. A bar-like elongation of the CO emission along the optical bar and a velocity field which suggests noncircular motions are found. These results are consistent with predictions based on the theoretical model of barred spiral galaxies. The inflow and concentration of molecular gas in the nucleus of M83 may supply raw material which maintains a burst of star formation there.
Numerical Simulations of Star Formation Bursts Induced by the Galaxy-Galaxy Interaction
Authors: Noguchi Masafumi , Ishibashi Shiro
Published: June 2019

The galaxy-galaxy interaction has been proposed as a possible triggering mechanism of the star formation bursts in some galaxies (e.g. Larson and Tinsley 1978). To investigate the nature of star formation bursts triggered by interaction we have numerically simulated close encounters between disk galaxies, taking the star formation process into account (see Noguchi and Ishibashi 1986 for details). We used the cloud-particle model, in which gas clouds move as test particles in the gravitational field of the galaxies. When two clouds collide with each other, an OB-star is formed. The cloud system loses its kinetic energy by inelastic cloud-cloud collisions. The supernova explosion which follows the formation of an OB-star provides kinetic energy to the nearby clouds.
Current Work on Starforming Regions at UKIRT
Authors: Mountain C. M.
Published: June 2019

UKIRT offers unique flexibility in the range of instrumentation available to study starforming regions in the infrared. Because of this many aspects of starformation are currently under study and the latest developments from UKIRT are reviewed. Work ranges from detailed high resolution spectroscopic studies of outflow sources to IRAS “follow-up” of molecular clouds and large scale starformation in normal and interacting galaxies.
On the Inclination of the Lunar Axis
Authors: Moutsoulas M.
Published: June 2019

Since the days of Cassini (1693), study of the position of the lunar axis relative to an inertial system of reference has been based on the assumption that “the inclination of the Moon's equator to the plane of the ecliptic is constant”. And, although the actual value of that inclination has been subject to continuous changes and modifications, reduced from the originally suggested 4½° to 1°32′4″ (Koziel, 1967), no sufficient attention has been paid to the fact that, as the lunar globe moves within the field of varying external forces, the inclination of its axis cannot remain constant.
Some Differences Between Geometrical and Dynamical Figures of the Moon
Authors: Gavrilov I. V.
Published: June 2019

The geometrical shape of the Moon is determined from measurements of absolute heights of the lunar surface, while its dynamical shape is described by means of the Moon's gravity field parameters. All these data are derived from observations of the lunar artificial satellites (‘Luna-10’, ‘Orbiters 1-4’) and astronomical measurements.

In the paper differences of the lunar geometrical and dynamical figures are analysed. It is shown, that the homogeneous model of the Moon is not capable of explaining these differences. It is found, that the lunar centre of gravity situated about 0.9 km to the north, and 1.1 km nearer to the Earth, than the centre of its geometrical figure.
Formation of Lunar Glassy Spherules: A Dynamical Model
Authors: Carusi A. , Coradini A. , Fulchignoni M. , Magni G.
Published: June 2019

Glassy spherules ranging from 200μto 62μin size have been separated from lunar dust samples No. 12001.73, 12057.60, 12070.37. Most of them are regular in size (spherical, ellipsoidic, dumbbell, teardrop, etc.); some are irregularly shaped.

A tentative dynamical model of the evolution of a rotating melted spherical drop of homogeneous glassy material has been built in order to explain the observed forms. We suppose such fluid to be originated from the impact of meteoroids on the lunar surface. The energy balance between the projectile (meteoroid) and the target (lunar surface) has been calculated supposing that the impact gives rise to strong shock waves in both bodies.

Equations of the model have been solved numerically and a good agreement between these results and the experimental data regarding small spherules has been obtained.
The Valence States of 3d: Transition Elements in Apollo 11 and 12 Rocks
Authors: Cohen Alvin J.
Published: June 2019

The absorption spectra of Apollo 11 fine-grained rocks, 10017 and 10022 are due entirely to pyroxene minerals. Spectral bands due to Fe3+, Fe2+, Cr3+ and Ti4+ and Ti3+ are detected. Single crystals of olivine in rocks 12021 and 12018 show bands due to Fe3+, Fe2+, Cr3+, Ti3+, Mn3+, and Mn2+. Pyroxenes in the same rocks exhibit band maxima of the same cationic species as in the olivines. Spectral shifts are noted due to anisotrophy of the crystal structures.

Heating sections 10017, 10022, and 12018 from the rock interiors at 200–225°C for 2 h caused large decreases in the spectral intensity of Fe3+, Cr3+ and Ti3+, indicating the following reaction:

Fe3+ + Cr3+ + Ti3+ → Fe2+ + Cr2+ + Ti4+

This suggests that Fe3+, Cr3+ and (a portion of) Ti3+ are not in equilibrium. It is most probable that they were produced subsequent to the formation of the rocks by a combination of secondary ionization processes following cosmic ray bombardment and by trace radioactivity present in the rocks.

An orange glass, 150 μ in diam and 50 μ thick contained in brecciated rock, 10048.44, exhibited 15 identifiable absorption bands related to Fe2+, Cr3+, Ti3+, Mn3+ or Mn2+ ions.

Plagioclase in 12021.65 has perfect transmission over the region studied. The limit of Fe3+ is in the order of < 1 ppm and Fe2+, 1000 ppm or less in this plagioclase single crystal of dimensions 0.6 mm × 0.2 mm × 30 μ.
Low Energy Solar Nuclear Particle Irradiation of Lunar and Meteoritic Breccias
Authors: Dran J. C. , Duraud J. P. , Maurette M.
Published: June 2019

We have studied by combined high voltage and scanning electron microscopies both the latent and etched track distributions in lunar fragmental rocks as well as in solar type gas-rich meteorites. We have used a new experimental approach for studying gas-rich meteorites to avoid problems with the interpretation of the results. Some implications of the present results concerning the ancient solar flare cosmic rays and the origin of the track distributions in gas-rich meteorite crystals will be discussed.
The Particle Track Record of the Lunar Surface
Authors: Comstock G. M.
Published: June 2019

Information about lunar surface history revealed by fossil particle tracks is summarized. Such tracks are the result of damage left in dielectric materials by highly ionizing charged particles including heavy solar and galactic cosmic ray nuclei, heavy nuclei recoiling from cosmic ray induced spallation reactions and induced- and spontaneous-fission fragments. From the distribution of cosmic ray and spallation tracks in the lunar rock, surface residence times of 1 to 30 million yr and rock erosion rates of 1 to 10 Å/yr have been determined. Particle tracks also record surface orientation and depth history of the rocks and contain information about ancient solar activity. The distribution of particle tracks in lunar soil is found to be consistent with a model which includes repeated excavation, layering and burial. With this model one core 12025 + 28 soil layer can be identified as unmixed and weakly irradiated; the others contain soil which has been better and better mixed and more and more irradiated.