bluuebunny/crossref_metadata_2025 huggingface dataset:
A Quantitative Study of Magnetic Flux Transport on the Sun
Authors: Sheeley N.R. , Boris J.P. , Young T.R. , DeVore C.R. , Harvey K.L.
Published: June 2019

A computational model, based on diffusion, differential rotation, and meridional circulation, has been developed to simulate the transport of magnetic flux on the Sun. Using Kitt Peak magnetograms as input, we have determined a best-fit diffusion constant by comparing the computed and observed fields at later times. Our value of 730 ± 250 km2/s is consistent with Leighton's (1964) estimate of 770–1540 km2/s and is significantly larger than Mosher's (1977) estimate of 200–400 km2/s. This suggests that diffusion may be fast enough to account for the observed polar magnetic field reversal without requiring a significant assist from meridional currents.
On the Stellar Rotation-Activity Connection
Authors: Rosner Robert
Published: June 2019

I discuss the connection between the rotation rate of late-type dwarf stars and their level of surface “activity” (as deduced from visible, UV, and X-ray observations) from both theoretical and observational perspectives.
Amplification of Magnetic Fields by Compressible Convection
Authors: Proctor M.R.E.
Published: June 2019

Previous work on the concentration of magnetic field by cellular convection in a Boussinesq fluid is extended to a perfect gas, so that the gas pressure is reduced in the presence of a strong magnetic field. Attention is focussed on 2-dimensional flows and on the case of small layer depths, so that the pressure is effectively uniform in field free regions. It is shown that if the field is sufficiently strong, flux sheets with significantly reduced pressures and densities may form. Criteria are established which measure the relative importance of this effect to the more familiar ‘magnetic drag’ which acts to prevent the concentration of field by generating counter vorticity.
Expulsion of Magnetized Plasmas from Coronae
Authors: Low B. C.
Published: June 2019

A theory of the white light transient phenomena in the solar corona is given, based on recent analytic treatments of magnetohydrodynamics.
Star Counts in Fields Surrounding the LMC
Authors: Brück M.T.
Published: June 2019

Star counts in a number of fields near the Large Magellanic Cloud have shown a maximum extension of about 10° for the faint stars. The luminosity function in the outer regions of the LMC is consistent with an intermediate age population.
The Brightest Stars in the Magellanic Clouds and Other Late-Type Galaxies
Authors: Humphreys Roberta M.
Published: June 2019

The brightest stars always receive considerable attention in observational astronomy, but why are we so interested in these most luminous, and therefore most massive stars? These stars are our first probes for exploring the stellar content of distant galaxies. Admittedly, they are only the tip of the iceberg for the whole stellar population and very interesting processes are occurring among the less massive, older stars, but the most massive stars are our first indicators for studies of stellar evolution in other galaxies. They provide the first hint that stellar evolution may have been different in a particular galaxy because they evolve so quickly. The most luminous stars also highly influence their environments via their strong stellar winds and mass loss and eventually as supernovae.
A Survey for Red Variables in the Magellanic Clouds
Authors: Lloyd Evans T.
Published: June 2019

One LMC and two SMC fields of 0.3 sq. deg. have been searched for red variables. Carbon stars of V ~ 16–17 are common and are usually of small amplitude, while the LMC alone contains numerous faint M type variables of small amplitude. M giants of small amplitude generally have much shorter periods than carbon stars. The LMC contains numerous Miras with a P-L relation similar to that of galactic Miras, while the SMC has few Miras but many bright red variables of large amplitude which have a steeper P-L relation.
A More Complete Listing of LMC Planetary Nebulae
Authors: Sanduleak N.
Published: June 2019

In an earlier paper by Sanduleak et al. (1978) a listing was given of 102 confirmed and probable planetary nebulae in the Large Magellanic Cloud detected on objective-prism plates taken with the Curtis Schmidt telescope at Cerro Tololo. Subsequently, deeper coverage was obtained on nitrogen-baked Kodak IIIa-J plates plus GG 455 filter exposed for 90 minutes. The thin prism was again used to provide a dispersion of about 1500 Å mm−1 at Hβ and the spectra were unwidened. An additional 25 planetary nebula candidates were found on this new plate material to show the requisite characteristics, i.e. they display (a) a stellar appearance, (b) [OIII] λλ5007, 4959 strongly in emission, and (c) no evidence of a continuum.
A New 21-cm Line Survey of the LMC
Authors: Rohlfs K. , Kreitschmann J. , Feitzinger J. V.
Published: June 2019

The measurements were made in Feb. 1982 with the Parkes 64 m telescope using a corrugated waveguide horn with total half-power beam width of 15′, the first sidelobes being 19 dB down, resulting in an aperture efficiency ηA=0.53±0.007, a main beam efficiency of ηmb=0.80±0.005 and a ratio of source flux to antenna temperature of Γ=0.62±0.1 K/Jy (Murray, priv. comm.). A cooled two channel FET frontend used in the frequency switching mode with Δν = 2 MHz resulted in a system noise temperature at zenith of Tsyst = 40 K for one channel and Tsyst = 50 K for the other. Each frontend channel received a single polarization mode, and this radiation was then further analysed in a 2 × 512 channel autocorrelation spectrometer set at a channel separation of 3.906 KHz corresponding to a velocity resolution of V = 0.824 km s−1. Hanning smoothed this resulted in a σT = 0.05 K for the average of both polarization.
SMC: UV Extinction Curves, Gas to Color-Excess Ratios
Authors: Lequeux J. , Maurice E. , Prévot L. , Prévot-Burnichon M-L. , Rocca-Volmerange B.
Published: June 2019

We have made an extensive study of the far-UV extinction in SMC stars using IUE spectra mostly obtained by us. The studied stars are Sk 7, 13, 18, 32, 76, 82, 85, 103, 119, 124, 142, 143, 159, 191 and AV 398. A few other stars have also been observed but are unsuitable for extinction studies. We have obtained at ESO new photometry and spectral classifications for all the studied stars. The far-UV extinction curves derived from IUE spectra of matched star pairs are all similar, except for Sk 143 (Lequeux et al., 1982), Sk 124 and 191. The mean curve, which supersedes that of Rocca-Volmerange et al. (1981) is plotted Fig. 1 with the label SMC “normal”, as well as the curves for the three “anomalous” stars (full lines) For comparison, we also plot the LMC “normal” curve and that for the anomalous star Sk-69°108 (dotted-dashed curves), the “normal” galactic curve and the curves for two stars in Scorpius-Ophiuchus.
Calibration En Magnitudes Absolues De La Classification BCD. Application à La Détermination Du Module De Distance Du Grand Nuage De Magellan
Authors: Divan L.
Published: June 2019

The calibration of the BCD stellar classification in absolute magnitudes (classification in three parameters λ1, D, Φb) was used to determine the distance modulus of the Large Magellanic Cloud. The described method makes use of the spectrophotometric parameters of B and A supergiants of the Large Cloud and gives a value of the distance modulus which is independent from other determinations, in particular from those which are based on the RR Lyrae and the Cepheid variables. The value found for the distance is slightly smaller than those generally admitted. The results are still based only on a limited number of measurements and new observations are in process; however, it seems doubtful that one will obtain much larger values. In other respects, the observations have shown that the parameter λ1 was still sensitive to luminosity for the B and A stars brighter than M = −8 and that the calibration of the λ1D diagram in absolute magnitudes can be extended up to M = −9.
Absolute Solar Intensities and the Solar Constant
Authors: Neckel H. , Labs D.
Published: June 2019

Absolute intensity measurements made in high altitudes on board of an aircraft are of less accuracy than ground based observations made at locations with favourable atmospheric conditions. As things stand, the rms-errors appear to be ⩾ 3% and ⩽ 2% respectively. Some of the reasons are sketched.
Ultraviolet Energy Distribution of He-Weak Stars
Authors: Bernacca P. L.
Published: June 2019

Ultraviolet observations of Helium-weak stars carried out on OAO-2 indicate that temperature estimates from the ground based region of the spectrum may be unreliable.
Stellar Temperature Scale and Bolometric Corrections
Authors: Heintze J. R. W.
Published: June 2019

In chapter 1 basic methods are reviewed, and applications and suggestions for future work are presented. In chapter 2 a revision is given of the intrinsic-colour relation in the U, B, V system of hot main-sequence stars. Some temperature-colour relations are discussed in chapter 3, where also a correction formula is given for the effects of interstellar reddening on the effective temperatures of hot main-sequence stars. An empirical mass-luminosity relation is given in chapter 4.
Computation of Compilation Catalogs
Authors: Corbin Thomas E.
Published: June 2019

Currently the computation of mean positions and proper motions for the International Reference Stars (IRS) is hampered by large variations in the observational histories of the stars and lack of overlap between the magnitudes of the IRS and of the FK4. The poorest IRS observational histories are +60° to +80° in the north and −40° to −80° in the south. The much-needed extension of the fundamental system to the ninth magnitude will be made in the FK5. The Faint Fundamental Extension is currently being selected at the U. S. Naval Observatory. A proposed list of 1030 Faint Fundamental stars has been prepared for the Northern Hemisphere, and work has begun on the selection in the Southern Hemisphere.
Global Reduction of Fundamental Astrometric Data
Authors: Benevides-Soares P. , Clauzet L.B.F.
Published: June 2019

Fundamental observational programs are often lengthened because of the sparsity of data during bad weather seasons and the need of having strong links all over the 24h of right ascension. The global reduction procedure tries to minimize this problem by making more efficient use of the available information with full consideration of incomplete or isolated group observations. The whole set of observational material is treated as a single least squares problem, whose unknowns include corrections to the star positions. The problem is usually of huge dimensions, but we show that it can be reduced to quite tractable sizes. As an example, the method is applied to a two year series of astrolabe observations. The time and latitude curves are solved for under the form of cubic spline functions. The results are equivalent to those of conventional procedures, provided due account is given to the fact that, in the global reduction, long period components of image motion are fully included in the standard error estimates.
The JPL/DSN J2000 Radio Reference Frame
Authors: Niell A. E. , Fanselow J. L. , Liewer K. M. , Sovers O. J. , Thomas J. B. , Treuhaft R. N. , Wallace K. S.
Published: June 2019

Development of a radio reference frame of very high accuracy has become necessary in order to obtain the required accuracy in spacecraft navigation for current and future planetary missions. The antennas of the NASA Deep Space Network are being utilized on a regular basis to obtain the positions of over 100 compact extragalactic radio sources distributed over the sky down to a declination of −45 degrees with uncertainties of less than 0.005 arcseconds.
The Use of the RATAN-600 Radio Telescope in Astrometry
Authors: Afanasieva P. M. , Fomin V. A. , Zverev Yu K. , Mingaliev M. G. , L'Vov V. N. , Pozhalov A. A.
Published: June 2019

The RATAN-600 radio telescope (Kaidanovsky & al. 1972) was designed for solving various problems of astrophysics and radiophysics (Pariisky & al. 1972, Gelfreikh & al. 1972). Because of its high resolving power and large collecting area, this instrument can be used to measure accurate positions of radio sources.
Plans for the Second Epoch of the Southern Proper Motion Program
Authors: López Carlos E. , Lee Jin-Fuw , van Altena William
Published: June 2019

The first photographs for the Yale-San Juan Southern Proper Motion (SPM) program with respect to faint galaxies were taken with the collaboration of Columbia University in 1965. The first epoch photography was essentially completed in 1974 and plans are now under way to begin the second epoch observations in 1986.
Infrared Speckle Interferometry: A Sensitive Technique for Physical Measurements of Unseen Companions to Nearby Stars
Authors: McCarthy D. W.
Published: June 2019

Infrared speckle interferometry combines the full resolving power of large telescopes with high photometric sensitivity over the wavelength range 2.2 to 12 microns. Despite improved atmospheric seeing at these wavelengths, seeing fluctuations limit measurement precision. Astrometric companions have been detected with angular separations ≥0.1 arcsec and magnitude differences ≤3.7 mag. Results illustrate seeing limitations and show how the usual position angle ambiguity can be overcome. These measurements yield masses and absolute magnitudes for calibrating the lower main sequence. In some cases, orbital motion is detected. A method of “shift-and-add” enables detection of substellar (0.04 to 0.08 M⊙) companions. Future improvements involving detector arrays and seeing monitors are discussed.
Photoelectric Astrolabe and Astrolabe Star Catalogues
Authors: Ding-jiang Luo , Dong-ming Li
Published: June 2019

At the Shaanxi Observatory, regular observations with the prototype of the photoelectric astrolabe PAI have been carried out since 1973. Three photoelectric astrolabes of type Mark II (PAII) were mounted at the Shanghai, Beijing and Yunnan Observatories in 1974, 1976 and 1978, respectively. Details of the instruments and the results of the observation were published previously. (Photoelectric Astrolabe Developing Group 1973 and 1975, Second Group, First Divsion Shaanxi Observatory 1974, Astrolabe Data Analysis Group, First Division, Shaanxi Observatory 1975, Wang, L-j 1979, Astrolabe Group, First Division, Shanghai Observatory 1976, Wang, L-z and Luo 1979, Lu and Luo 1979). Time and latitude determinations by these sets of photoelectric astrolabes form a part in the international cooperation of BIH, IPMS as well as in the short campaign of project MERIT.
Carlsberg Automatic Transit Circle: First Two Test Catalogues and the Programme for La Palma
Authors: Morrison L V , Gibbs P
Published: June 2019

The first two catalogues produced from test observations made with the Carlsberg Automatic Transit Circle (CATC) at the Copenhagen University Observatory in the period 1981/83 have internal mean errors of 0″.21 in right ascension and 0″.22 in declination. In 1983 the CATC was moved to the international Observatorio del Roque de los Muchachos where it will begin a programme of differential and fundamental astrometry in 1984.
On Desiderata for Star Catalogs for the Remainder of the Twentieth Century: A Report on Catalog Work Now in Progress at the U.S. Naval Observatory
Authors: Smith Clayton
Published: June 2019

The results of observations of Southern Reference Stars (SRS) of all participants in the SRS program (1961–1973) have been received at the U.S. Naval Observatory. It is anticipated that compilation of the final SRS catalog of mean positions will be completed by the end of 1984.

A supplementary list to the International Reference Star (IRS) catalog is described. It has been selected with a view to improving areal density and distribution in spectral type.

A comparison of solutions for equator and equinox corrections and corrections to the assumed elements of the earth's orbit from daytime observations of the Sun, Mercury, and Venus and nighttime observations of Ceres, Pallas, Juno, and Vesta from Six-inch Transit Circle observations made during the W5-50 program (1963–1971) shows that a very significant part of the systematic daytime error has been removed. A problem remains for observations of the Sun, particularly in declination.
Chemical Reactions in Astrochemistry
Authors: Rowe B. R.
Published: June 2019

This paper is devoted to chemistry in the gas phase dealing firstly with ion-molecule reactions at extremely low temperature. The experimental techniques that have been used in this field are shortly presented and the reactions that have been studied using the CRESU(S) method reviewed. In the second part, the most recent measurements concerning dissociative recombination are discussed, including studies of branching ratio and new determination of the rate coefficient for H+3 ions.
Astrochemistry Library with Artificial Intelligence for Quality Control
Authors: Prasad Sheo S. , Gangopadhaya Pradip
Published: June 2019

Libraries of reactions used in astrochemistry modeling have seen an explosive increase in size in recent years. Their quality control by manual effort is almost impossible. Expert systems with artificial intelligence are now needed to ensure the quality of large scale astrochemistry libraries.
Infrared Spectroscopy of Interstellar and Solar System Ice Analogs: MEasurement of Optical Constants
Authors: Hudgins D.M. , Sandford S.A. , Tielens A.G.G.M. , Allamandola L.J.
Published: June 2019

Laboratory spectra through the mid-infrared have been used to calculate the optical constants (n and k) for a variety of pure and mixed molecular ices. The ices studied were H2O, CH3OH, CO2, OCS, CH4, CO2+CH4, CO2+OCS, CO+CH4, CO+OCS, O2+CH4, O2+OCS, N2+CH4, N2+OCS, H2O+CH4, H2O+OCS, and H2O+CH3OH+CO+NH3.
Computational Chemistry Approach to Space Chemistry
Authors: Ellinger Y.
Published: June 2019

This review paper presents the results of state of the art Quantum Chemistry calculations in the field of Astrochemistry. It provides selected examples to illustrate the possible contribution of molecular orbital theories to solving a number of problems of astrophysical interest ranging from identification of new molecules to IR emission analysis and rate constants determinations.
Grain Spectroscopy
Authors: Allamandola L. J.
Published: June 2019

Our fundamental knowledge of interstellar grain composition has grown substantially during the past two decades thanks to significant advances in two areas: astronomical infrared spectroscopy and laboratory astrophysics. The opening of the mid-infrared, the spectral range from 4000-400 cm−1 (2.5-25 μm), to spectroscopic study has been critical to this progress because spectroscopy in this region reveals more about a material's molecular composition and structure than any other physical property.
Primordial Molecular Hydrogen Production and the Formation of Population III Objects
Authors: de Araujo J.C.N. , Opher R.
Published: June 2019

We study the formation of Population III objects (and stars) taking into account the expansion of the Universe and a series of physical processes relevant to the primordial plasma. In particular, a very important way to cool the first condensations in the Universe is with molecular hydrogen. The minimum mass of the Population III objects formed is ~ 104M⊙. We show also that stars of mass ≳ 50M⊙ can be formed from the fragmentation of Population III objects of mass ~ 106M⊙.
Deuterium in the Solar System
Authors: Owen T.
Published: June 2019

Values of D/H measured in the methane on the giant planets and Titan indicate the presence of two distinct reservoirs of deuterium in the outer solar system. The dominant reservoir is in hydrogen gas, the second, multi-component reservoir is found in the hydrogen that is bound in condensed compounds. Both reservoirs appear to have originated in the interstellar medium. In contrast, the values of D/H in water vapor on Mars and Venus (especially) exhibit a large enrichment from the “condensed matter” starting value. Interpretation of this enrichment may illuminate the history of water on these two planets.
H2 Emission from External Galaxies
Authors: Kawara Kimiaki
Published: June 2019

2 μm spectroscopic observations by many authors have revealed significant rotation-vibrational H2 emission is widespread from starburst to bare nucleus galaxies. Near-IR H2 emission lines can arise from various excitation sources: UV radiation by hot stars, shock excitation by supernova remnants or AGN driven winds, and UV/X-ray radiation by an AGN. In this review recent data will be compared with such H2 excitation models.
Interstellar Polarization in the Small Magellanic Cloud
Authors: Rodrigues C. , Magalhãtes A.M. , Coyne G. , Piirola V.
Published: June 2019

Data of our on-going program on the interstellar polarization in the Small Magellanic Cloud (SMC) seem to show a correlation between the UV extinction and the parameters of the Serkowski law which describe the polarization. Fits of popular interstellar dust models to the polarization data are not always satisfactory, being better for stars with small wavelength of maximum polarization, λmax.
Chemical Effects of Shear Alfvén Waves in Molecular Clouds
Authors: Charnley S.B. , Roberge W.G.
Published: June 2019

We consider the propagation of low-amplitude MHD waves in partially-ionised plasmas. Ion-neutral drift (ambipolar diffusion) can lead to significant variations in the deuterium fractionation ratios of several molecules (e.g. HCO+ and N2H+) on spatial scales of between a few hundredths and a few tenths of a parsec, depending upon the fractional ionisation of the plasma. It is possible that interstellar Alfvén waves could be detected by molecular spectroscopy and that these waves may produce other small-scale abundance gradients in molecular clouds.
Abundance of DCO+ in Nearby Molecular Clouds
Authors: Butner Harold M.
Published: June 2019

DCO+ is one of the most common deuterated molecules in cold (TK ~ 10 K) molecular cloud cores such as TMC-1. We report the results of a survey for DCO+ and H13CO+ emission regions among a sample of low mass cloud cores. We compare the derived DCO+/HCO+ ratio (0.046±0.014) with current chemistry models for deuterium fractionation.
Molecular Abundance Variations Among and Within Cold, Dark Molecular Clouds
Authors: Ohishi Masatoshi , Irvine William M. , Kaifu Norio
Published: June 2019

The latest table of molecular abundances in the cold, dark clouds TMC-1 and L134N is presented. Molecular abundance variations between TMC-1 and L134N, those within TMC-1 and L134N, and those among 49 dark cloud cores surveyed by Suzuki et al. (1991) are interpreted as an effect of chemical evolution.
The Formation of Deuterated Molecules in Dense Clouds
Authors: Millar T J
Published: June 2019

In this article, I list the deuterated species detected so far, together with an estimate of their abundance ratios relative to their hydrogen bearing parent for a variety of astronomical regions, discuss the basic chemical processes which fractionate deuterium together with some simple estimates of the degree of fractionation which can result from these processes. I then discuss in detail the deuteration of hydrocarbon molecules and show that the effects of chemical reactions which can recycle parent species can appreciably affect estimates of fractionation. Finally I shall discuss how structural effects may inhibit fractionation in the cyanopolyynes and related species.
Radiation Transfer and Photochemical Effects in Inhomogeneous Dense Clouds
Authors: Aiello S. , Cecchi Pestellini C. , Tiné S.
Published: June 2019

UV radiation leads to photodissociation and photoionization of molecular species in diffuse clouds and in the extended envelopes of dark regions. In the inner part of heavily-obscured objects, the residual external field may be negligible; alternative mechanisms, such as cosmic-ray-induced H2 emission, appear to be efficient in photodestruction processes. We evaluate the relative importance of these radiation sources, and give some estimates of their effects on the mean lifetime of interstellar molecules, taking into account the cloud structure that significantly affects the penetration depth of UV radiation.
Observations of Shocked Regions
Authors: Ziurys L. M.
Published: June 2019

Recent observations of molecular clouds perturbed by interstellar shocks are reviewed. Effects of the shock waves on the chemical composition of these regions are discussed.
The C:O Ratio in Dark Clouds with Cyclic Star Formation
Authors: Nejad L A M , Williams D A
Published: June 2019

Observations (Goldsmith et al., 1986) indicate that the gas in dark clouds with embedded low-mass stars experiences a cycle, driven by stellar winds, between low and high density phases. The cycle time is sufficiently short that the chemistry never attains steady state. Icy mantles accumulating on grains during the collapse and dense core phases are thought to be removed in each cycle by low velocity shocks that terminate the low density phase. Models of this type give detailed point-by-point descriptions of both gas and solid phases in molecular clouds (Charnley et al., 1988; Nejad et al., 1990).
Chemical Gradients in the Orion Molecular Cloud
Authors: Ungerechts H. , Bergin E. A. , Carpenter J. , Goldsmith P. F. , Irvine W. M. , Lovell A. , Mcgonagle D. , Schloerb F. P. , Snell R. L.
Published: June 2019

We are mapping 29 rotational transitions of 21 chemical and isotopic molecular species in the central Orion molecular ridge with Nyquist sampling using the new 15-element focal plane array receiver QUARRY on the FCRAO 14 m telescope. Our goal is to obtain complete, unbiased data sets for a study of the interrelated physics and chemistry in GMC cores.
OH Masers in Outflow Regions
Authors: Gray M. D. , Field D. , Doel R. C.
Published: June 2019

We combine a sophisticated model of maser propagation with a simple model of an accelerating molecular outflow and show that the observation of different OH maser frequencies is consistent with emission from different parts of the outflow.
Observations of CII, CI and CO in Interface Regions
Authors: Stutzki Jürgen
Published: June 2019

UV-radiation longward of the Lyman edge (912 Å) can escape from HII-regions. It photodissociates carbon monoxide (λ < 1118 Å) and photoionizes neutral atomic carbon (λ < 1101 Å). The resulting CII/CI/CO transition zone on the edges of molecular clouds (photodissociation region or photodominated region: PDR) has been studied in great detail theoretically (Tielens & Hollenbach, 1985; van Dishoek & Black, 1988; Sternberg & Dalgarno, 1989) and these investigations have recently been extended to cover a wide range of densities and UV-intensities (Burton, Hollenbach & Tielens, 1990; Hollenbach, Takahashi & Tielens, 1991; see also A. Sternberg, this volume).
Hot Core Chemistry: Gas Phase Molecule Formation in situ
Authors: Charnley S.B. , Tielens A.G.G.M.
Published: June 2019

The possibility that the observed abundances of several molecules in the Orion Hot Core are due to gas phase neutral chemistry has been examined.
The Physical and Chemical Structure of Warm, Dense Regions: IC 63 and IC 443
Authors: Jansen D.J. , Van Dishoeck E.F. , Black J.H. , Phillips T.G.
Published: June 2019

Elevated temperatures in molecular clouds can result either from heating by ultraviolet photons or from the passage of shock waves. The effect that these processes have on the chemical abundances is not well established observationally, but is of great importance for the interpretation of molecular line observations not only in our own Galaxy, but also in external galaxies. We present here initial results from our study of two “template” regions: the photon-dominated region IC 63 and the shocked region IC 443.
Observations of Water and Molecular Oxygen in the Interstellar Gas
Authors: Neufeld David A.
Published: June 2019

Water and molecular oxygen are two simple molecules which are not easily observed in the interstellar medium. O2 emissions have yet to be detected from interstellar space, and H2O has been observed only in rather special environments where the interstellar gas has been warmed by embedded infrared sources or by shock waves. This sorry state of affairs does not necessarily reflect a low interstellar abundance for these species, but rather is a consequence of the very high abundance of O2 and H2O within our own atmosphere: strong atmospheric absorption lines make it extremely difficult to carry out observations of water and molecular oxygen emissions using ground-based or even airborne telescopes. Future observations from two orbiting telescopes scheduled for launch in the coming five years - the Infrared Space Observatory (ISO) and the Submillimeter Wave Astronomy Satellite (SWAS) - promise to improve radically the observational data on H2O and O2.
VLBI Observations of Ammonia (9,6) Masers
Authors: Pratap Preethi , Menten Karl M. , Reid Mark J. , Moran James M. , Malcolm Walmsley C.
Published: June 2019

We present the first VLBI measurement of interstellar ammonia (NH3) masers. Two masers were found toward the ultracompact Hii regions, W51-e1 and e2. The masers are unresolved in angle and smaller than 0.1 milliarcseconds. Unless these masers are highly beamed, they appear to be saturated.
H Atom Observations in Near-Stellar Environments
Authors: Rodriguez Luis F.
Published: June 2019

Interferometric observations of the 21-cm line of atomic hydrogen resolve out the emission from extended, line-of-sight clouds and allow the detailed study of compact H I structures in the surroundings of some stars. These atomic hydrogen components most probably are the result of photodissociation of gas that originally was in molecular form. They have been observed in H II regions, reflection nebulae, and planetary nebulae. The study of this atomic hydrogen component is important to determine the mass and physical conditions of gas in the environment of luminous stars and to test our theoretical knowledge of photodissociation regions.
Infall in Collapsing Protostars
Authors: Rawlings J M C , Hartquist T W , Menten K M , Williams D A
Published: June 2019

High spectral resolution observations of dense cores in lines of NH3 have provided no clear evidence for infall, even when the cores possess embedded low mass protostars or young stellar objects (Menten et al., 1984; Menten and Walmsley, 1985; Myers and Benson, 1983). Infall is expected to continue until protostellar winds begin to affect the dynamics of the cores.
Carbon to Helium Ratio in the Wind of Central Stars of Planetary Nebulae with WC Spectrum
Authors: De Freitas Pacheco J.A. , Costa R.D.D. , De Araújo F.X. , Petrini D.
Published: June 2019

We present C/He ratios in the wind of a sample of 5 central stars of planetary nebulae having WC spectrum. The resulting values are comparable to those observed in population I WR stars.
Molecules in Stellar Winds
Authors: Glassgold Alfred E.
Published: June 2019

High mass-loss molecular winds are characterstic of two important phases of stellar evolution, very young protostars and stars on the asymptotic branch. Novel chemical processes in these winds suggest a variety of new astronomical observations.
Excited Hydrogen Chemistry in Protostellar Outflows
Authors: Rawlings J.M.C. , Drew J.E. , Barlow M. J.
Published: June 2019

Chemical models of protostellar and other outflows have been reassessed in the light of new chemical data. In particular, reactions involving excited hydrogen (2s,p) are shown to be important in hot, dense outflows. The H(n=2) + H → H2 + hv reaction is much less of a contributor to the H2 formation rate than the recently measured H(n=2) + H → H2+ + e- reaction, providing conditions allow the 0.75eV endothermicity of this reaction to be overcome.
Molecules in the Envelopes of Late-Type Stars
Authors: Lucas R.
Published: June 2019

With physical conditions very similar to those of molecular clouds, circumstellar envelopes (CSEs) are the sites for a rich chemistry. Hovever their simpler geometries, the variations in elemental composition, and the short time scales of the outflows, make them objects of particular interest to the astrochemist. For a recent and general review of circumstellar chemistry the reader may refer to Omont (1990). Here we give only a very short overview (Section 2), then we report on some of the very recent observational advances in this field (Section 3).
Sub-Millimetre Observations Of SiCC in IRC 10216
Authors: Avery L.W. , Amano T. , Bell M.B. , Feldman P.A. , Johns J.W.C. , Macleod J.M. , Matthews H.E. , Morton D.C. , Watson J.K.G. , Turner B.E. , Hayashi S.S. , Watt G.D. , Webster A.S.
Published: June 2019

We have used the James Clerk Maxwell Telescope to observe 11 lines of SiCC with excitation energies up to 330 K above the ground state in IRC 10216. An excitation analysis indicates Trot = 43 ± 5 K within a given Ka ladder and Texc = 160 ± 50 K between Ka ladders. The column density of SiCC is estimated to be 3 × 1015 cm−2, more than an order of magnitude higher than previous estimates.
Carbon Stars with Oxygen-Rich Circumstellar Envelopes
Authors: Lorenz Martins Silvia , José Codina Landaberry Sayd
Published: June 2019

We observed two carbon stars with silicate emission, C1003 and BM GEM, and we calculated the abundances ratios. The results are compared with them of R0 stars (Dominy, 1984).
Are Molecules Responsible for Origin of Cold Giants Mass Loss?
Authors: Shmeld I. K. , Strelnitskij V. S. , Fedorova A. V. , Fedorova O. V.
Published: June 2019

It is shown that radiative pressure in vibronic transitions of molecules may play an important role in origin of mass outflow of cold giants and supergiants.
Diamagnetic Abundance Differentiation in the Solar System
Authors: Steinitz Raphael , Kunoff Estelle
Published: June 2019

Chemical abundances in the solar corona or solar wind compared to those in the photosphere differentiate according to first ionization potential (FIP). We suggest that the effect is the result of diamagnetic diffusion pumps operating in the presence of gravitation and diverging magnetic structures. We then comment briefly on implications concerning abundances in the solar system and chemically peculiar stars.
Laboratory Studies of Planetary Molecules and Ices: The Case of IO
Authors: Salama F. , Sandford S. A. , Allamandola L. J.
Published: June 2019

The techniques of low temperature spectroscopy are applied here to analyze infrared observational data of Io in the 2.0-5.0 μm range. The presence of solid H2S and traces of H2O in the SO2-dominant surface ices are derived from this analysis and it is suggested that CO2 clusters may as well be present near the surface of Io.
Dense Knots in High Latitude Molecular Clouds
Authors: Blitz Leo
Published: June 2019

The high latitude molecular clouds are discussed in the context of the formation of very low mass condensations: protojupiters. The ability to identify such objects is intimately tied to the resolution of the current debate concerning the density of the condensations inferred from observations of high density tracers. At the heart of the debate is whether inclusion of electron excitation plays an important role in the determination of column densities. A brief review of molecular abundances shows that with the possible exception of H2CO, the molecular abundances in the high latitude molecular clouds are not abnormal.
General Theory for the Outer Planets
Authors: Bretagnon P. , Francou G.
Published: June 2019

An iterative method for the construction of planetary theories has been developed in order to determine the high order perturbations with respect to the masses. These perturbations are indeed needed to enlarge the validity span of analytical theories up to some million years. The application to the simplified Sun-Jupiter-Saturn problem gives a solution accurate over several ten million years. Throughout the study of the four outer planets we meet with convergence difficulties especially in the determination of fundamental frequencies. One of the results of this study is it shows evidence of long period terms with large amplitude in the mean longitudes: 12 000″ in Saturn longitude, 20 000″ in that of Uranus.
Collisional Simulations of Isolated Lindblad Resonances
Authors: Hänninen J. , Salo H. , Lukkari J.
Published: June 2019

The influence of the perturbing satellite on the planetary ring at isolated Lindblad resonances is studied with numerical computer simulations, combining the Aarseth's force polynomial method for orbit integrations with the calculation of particle-particle impacts. Observed angular momentum exchange between the satellite and the dissipative, non-selfgravitating ring agrees with the Goldreich-Tremaine formula for gravitating ring within 20%, verifying that the exerted torque is not sensitive to the details of the dominant physical processes. The theoretically predicted angular momentum luminosity reversal was also observed.
An Integrable Model for Helene
Authors: Bevilacqua J.S. , Sessin W.
Published: June 2019

The goal of our work is to determine the influence of Enceladus in the motion of Helene. We constructed a model considering an oblated central body (Saturn) and three satellites (Enceladus, Dione and Helene) under the action of central forces. The development of the potential was made assuming small eccentricities, null inclinations and two resonances present in this system (2:1 between Enceladus and Dione and 1:1 between Dione and Helene). The mean Hamiltonian preserves terms derived of the oblateness of the central body and also terms of both resonant arguments. The auxiliary Hori's system generated by this Hamiltonian is completely integrable. In the solution for Helene we included the perturbative effects of Dione and Enceladus which extend the usual teatment.
The Long-Term Dynamical Behavior of Small Bodies in the Kuiper Belt
Authors: Levison Harold F.
Published: June 2019

Recent numerical calculations [1,2,3] have shown that Jupiter-family comets, which are on low inclination orbits, cannot originate from the gravitational scatter of long-period comets. Work by Quinn, Tremaine & Duncan [1] shows that objects originally on low-inclination, Neptune crossing orbits will evolve into a population of objects with orbital parameters consistent with those of Jupiter-family comets. However, they point out that the timescale to deplete this initial population of planet-crossing objects is short. Therefore, they conclude there must be a system of objects that are evolving into planet-crossers on the timescale of the age of the solar system. The most likely source of these objects is a region just beyond the orbit of Neptune, the Kuiper belt.
New Developments in Dynamics: Hyperbolicity and Chaotic Dynamics
Authors: Palis J.
Published: June 2019

Two important theories in Dynamical Systems were constructed in the sixties: the hyperbolic theory for general systems and the KAM (after Kolmogorov, Arnold and Moser) theory for conservative systems as the ones that appear in Celestial Mechanics. Most of our discussions here concern dissipative (or locally dissipative) systems, although most questions are now being posed for area preserving maps (symplectic maps in higher dimensions). Moreover, one can argue that understanding dynamically small dissipative perturbations of conservative systems is of much importance: indeed it has been recently shown that a KAM curve (tori in higher dimension) can be destroyed and in fact engulfed in the basin of attraction of a Hénon-like strange attractor as defined below.
Mappings for the First Order Asteroidal Resonance
Authors: Stuchi T. J. , Sessin W.
Published: June 2019

We construct a two step algebraic mapping from Sessin's simplified model for the first order resonance. The orbits obtained with this mapping are compared to the ones calculated with the exact solution. We also derive a reduced Hamiltonian. A plane Poincaré mapping, using delta periodic function, is constructed and compared to the reduced Hamiltonian contour curves showing the splitting of the separatrix due to delta perturbation technique.
The Shape of the Moon
Authors: Runcorn S. K. , Hofmann S.
Published: June 2019

The determination of the heights of points on the lunar surface by Earth based astronomy using the geometrical librations, although individually of low accuracy, still provides our best method of obtaining the global shape of the Moon. The intrinsic scatter of the results arises from the effects of ‘seeing’ and simple statistical analysis is required to derive valid conclusions about the shape. Baldwin's method of fitting ellipsoidal surfaces to the points on the maria and uplands, separately by the method of least squares proves to be a valuable tool.

Analyses of the ACIC points and of the Pic du Midi studies of G. A. Mills show that good first descriptions of the global shape of the Moon for both the maria and uplands are triaxial ellipsoids with their long axes within 10° of the Earth direction, the major axis of the maria being about 1.3 km smaller than that of the uplands. Of particular significance is that the ellipticity of these surfaces is about 2½ times greater than the dynamical ellipticity; thus the non-hydrostatic figure of the Moon is not simply the result of distortion from a uniform Moon during its early history. The angular variation in density within the Moon cannot be simply a phenomena within the crust but must extend to a great depth. Convection could provide an explanation.

The departures of the lunar surface from the idealised ellipsoids are also of interest. The circular maria are systematically depressed relative to the maria ellipsoid: can the mascons have adjusted isostatically since their formation? Systematic differences in height between the western and eastern southern uplands are also noted.
Large Disks as Representations for the Lunar Mascons with Implications Regarding Theories of Formation
Authors: Muller P. M. , Sjogren W. L.
Published: June 2019

It is shown that large (hundred-km diam) near-surface disks are capable of accurately representing the lunar mascons with very few parameters. While this does not ‘prove’ that the mascons are excess mass in disk form, it is highly suggestive. It is pointed out that virtually every proposed mascon theory is consistent with a disk shape for the excess mass. The tentative hypothesis is advanced that the mascons are, in fact, disk shaped mass excesses. The conditions for mascon formation and preservation are reviewed in the light of this hypothesis.
On the Interaction Between Tectonic Processes of the Earth and the Moon
Authors: Kozyrev N. A.
Published: June 2019

At present seismographs are operating on the Moon as well, installed there owing to the successful Apollo missions. However these data are insufficient for detailed statistic investigations. That is why in case of the Moon we are to use indirect indications of its activity, such as the data on transient light phenomena from the catalogues by Miss B. Middlehurst. Among the great number of earthquakes there were chosen only the strong earthquakes (magnitude 6.5) with focuses deeper than 70 km. According to these characteristics 630 earthquakes were selected from 1904 to 1967. In the Middlehurst catalogue during the same period about 370 transient events on the Moon are registrated. A distribution of lunar events on the days of an anomalistic month gives evidence of the influence of the Earth's tidal forces (the Middlehurst effect). It appears that the distribution of earthquakes gives a similar curve. Thus the tidal interaction of the Earth and the Moon establishes certain synchronism in tectonic activity of these planets. The further statistic analysis reveals some more causal relation between the processes of the Earth and the Moon. Strongly pronounced maximum of lunar events is observed with the interval of 2–3 days after the earthquakes and the maximum of earthquakes – with quite the same interval after the lunar events. The peaks of these maxima exceed the mean number of events by a factor 3. The Moon Earth system is the astronomical example of a direct interaction of the processes in the neighbouring celestial bodies.

The corresponding experiments, made at the Pulkovo Observatory, confirm the possibility of immediate interactions of irreversible processes due to the change of physical properties of time. Thus we can form a chronology of orogenesis on the Moon judging from the data on the history of the Earth. Tectonic processes of the Earth and the Moon seem to be in such a close interaction as if the Moon were in direct contact with the Earth, i.e. in other words, were its seventh continent. These conclusions give evidence of the extreme importance of regular seismic observations on the Moon.
Luminescence Excitation by Protons and Electrons, Applied to Apollo Lunar Samples
Authors: Geake J. E. , Walker G. , Mills A. A.
Published: June 2019

A proton accelerator, modified for work on lunar samples, is described; 60 keV protons at about 1 μA cm−2 are used. Luminescence emission spectra in the visible and near IR regions are shown for lunar samples from Apollo 11 and 12, and preliminary results are given for Apollo 14 samples. Lunar samples are compared with terrestrial and meteoritic materials. Plagioclase is found to be the most efficient luminescent material present in the lunar samples, and the activator for its dominant green peak is found to be Mn2+.

Apparatus is described for taking colour photographs of the luminescence emission from rock chips under 6 keV electron excitation. Most of the lunar samples investigated show only plagioclase emission, but one breccia shows a wide variety of colours from different luminescent constituents.
The Role of Occultations in the Improvement of the Lunar Ephemeris
Authors: Morrison L. V.
Published: June 2019

Analyses of occultation timings show that periodic correction terms with semi-amplitude as great as 0.″18 arise from corrections required to the empirical constants of the Brown/Eckert theory. Using the atomic time-scale, some of the occultation data have been used to determine a correction of – 30 ± 16″/cy2 to Spencer Jones' value for the secular acceleration of the Moon. In the light of this correction, and previous determinations, attention is drawn to the possible weakness of Spencer Jones' value, which is not reflected in his quoted error of ± 1″/cy2. Further analyses of 50000 occultations observed since 1943 promise to reveal more accurately-determined corrections.
On the Initial Distance of the Moon Forming in the Circumterrestrial Swarm
Authors: Ruskol E. L.
Published: June 2019

According to the Radzievskij-Artemjev hypothesis of the ‘locked’ revolution of the circumplanetary swarms around the Sun, the initial Moon-to-Earth distance and the angular momentum acquired by the Earth through the accretion of the inner part of the swarm can be evaluated. Depending on the concentration of the density to the centre of the swarm we obtain the initial distance for a single protomoon in the range 15–26 Earth radii R and for a system of 3-4 protomoons in the range 3–78 R, if the outer boundary of the swarm equals to the radius of the Hill's sphere (235 R). The total angular momentum acquired by the primitive Earth-Moon system through the accretion of the swarm particles is ½–⅔ of its present value. The rest of it should be acquired from the direct accretion of interplanetary particles by the Earth. The contribution of satellite swarms into the rotation of other planets is relatively less.
On the Possible Differences in the Bulk Chemical Composition of the Earth and the Moon Forming in the Circumterrestrial Swarm
Authors: Ruskol E. L.
Published: June 2019

The model of the origin of the Moon in the circumterrestrial swarm during the active stage of the Earth's growth [1, 2] receives now a support (see e.g. [3]). In this model the feeding substance is the same for both bodies. However two different processes may be mentioned of chemical fractionation between the Earth and the Moon.