bluuebunny/crossref_metadata_2025 huggingface dataset:
Classification and Investigation of Solar Flare Situations Conformably to Interplanetary and Magnetospheric Disturbances
Authors: Ivanov K. G. , Mikerina N. V. , Evdokimova L. V.
Published: July 2016

A new classification of large solar flares is presented. If the time spacings between the flares are over 2.5 days, the flares and the corresponding interplanetary streams are classified as isolated ones. The concepts of the nearest, intermediate and distant flare zones (N, I and D zones) are introduced. The limits of the zones are determined at 30° longitude intervals and at 15° latitude ones. The classification is applied to the flares of 1966-1974 (Ivanov et al., 1979). It allows one to study the interplanetary and the magnetospherical disturbances more systematically.
Number Counts of Galaxies to B = 25
Authors: Karachentsev I. D.
Published: July 2016

Results are presented of counts of galaxies over the apparent magnitude range 21 ≤ B ≤ 25, which have been obtained at the 6–meter telescope using McMullan's electronographic camera. These data do not indicate evidence for rapid luminosity evolution of galaxies. It is noted that the faintest galaxies, on the whole, have bluish color and a small correlation function amplitude.
SIT Spectra of Faint Field Galaxies
Authors: Turner Edwin L.
Published: July 2016

Digital SIT spectra have been obtained in collaboration with J.E. Gunn and W.L.W. Sargent for a sample of 49 field galaxies chosen from Kron's survey of selected area 68. Most have apparent visual magnitudes in the range 19 to 21. Redshifts have been measured for 48 of the 49 galaxies. The redshift (or, equivalently, luminosity) distribution for the sample is anomalous in that ≥ 10% of the sample has z ≥ 0.3 (and, thus, L ≥ 6 L*). These high z and L galaxies are among the bluest objects in the sample. These data require substantial evolution of at least some galaxies at small z. It is tempting to speculate that this luminous, blue field galaxy population is related to the Butcher and Oemler blue cluster galaxies found in the same redshift range.
A Spectroscopic Search for Galaxies Associated with Quasi-Stellar Objects
Authors: Miller Joseph S. , French Howard B. , Hawley Steven A.
Published: July 2016

It is generally assumed that quasi-stellar objects represent phenomena taking place in galaxies. There are at least three lines of reasoning that lead to this viewpoint. First, there appears to be a continuity of properties extending from Seyfert galaxies and N systems to QSOs with the differences between the various groups principally a question of the contrast between the luminous central object and its surrounding galaxy. Since Seyfert galaxies and N systems are definitely in galaxies, it is concluded that QSOs must also be in galaxies which are not directly visible because of the high luminosity of the central object. A second argument is based on the result that QSOs do not appear to differ dramatically in abundances of elements from those which are typical of normal galaxies. With the prevailing view that virtually all the elements heavier than helium originated as a result of stellar processes, it would be concluded that QSOs must be associated with galaxies of stars that produced the heavier elements. A third, rather indirect argument is based on the results of Stockton (see his paper in this volume) and others that QSOs are often found in groups of galaxies and therefore are likely to be located in galaxies themselves (guilt by association). But the fact is that direct evidence that QSOs are in galaxies is sadly lacking.
IUE Observations of Quasars
Authors: Schmidt M. , Green R. F. , Pier J. R. , Estabrook F. B. , Lane A. L. , Wahlquist H. D.
Published: July 2016

Spectra of six quasars have been obtained with the International Ultraviolet Explorer Satellite. Five of the six show no evidence for strong Lyα absorption between the redshifted and rest wavelengths, for .23≤ zem ≤1.72. In addition, the quasar PG 1115+080 at z=1.72 shows no evidence for strong He I absorption from the resonance transition at λ584 Å. These results confirm that the intergalactic medium must be both tenuous and hot enough to produce an optical depth <0.1 in neutral hydrogen and helium. In no case was the Lyman edge detected in absorption near zem. Four of the objects produce an average Lyα/Hβ intensity ratio of 6.3, in disagreement with the theoretical prediction for Case B optically thick recombination of 30. Also, two of the objects show Lyγ in emission, a result unexpected from Case B line transfer assumptions. The Lyα emission line in 3C 351 shows the identical sharp core plus 20,000 km s−1 broad wings observed in Hβ and Mg II, implying a common origin in the same dynamical ensemble of emitting regions. These quasars show systematically steeper spectral indices when the energy distributions are fit from the ultraviolet through the visible than those derived from the visible spectra alone. PG 1115+080 shows a featureless continuum down to an observed λ1173 Å. The ionizing spectrum, with fν αν−2.0, therefore persists beyond 2 Rydbergs. The spectrum of PG 1247+268, with z=2.038, contains a strong absorption line at observed λ2697 Å, with no net flux detected from λ2000 Å down to the observed limit at λ1150 Å. This result is interpreted as absorption in Lyα and the Ly edge at z=1.218. Low dispersion optical spectra show no evidence for Mg II or C IV absorption in the same system; the signal to noise ratio is too low in the IUE spectrum to confirm Lyβ. We conclude that the line of sight intersects a metal-poor cloud with τ ≲ 1 in the Ly continuum, at (1+zem)/(1 + zabs) = 1.37.
Isotropy of Faint Sources
Authors: Fanti Carla
Published: July 2016

How matter distributes in the Universe is still an open question in spite of the many efforts people have done since early 1924 when Hubble first studied the distribution of bright galaxies.
New Observations with the VLA
Authors: Heeschen D. S.
Published: July 2016

The VLA, now under construction in New Mexico, is an aperture synthesis array of twenty-seven 25-meter diameter antennas, with overall dimension of about 35 km. At 6-cm wavelength it will have resolution of 0.6 arcseconds and sensitivity of 0.1 mJy, and should be a superb instrument for radio studies of objects of large redshift. A more detailed description of the VLA has been given by Heeschen (1975).
Infrared Observations of Elliptical Galaxies
Authors: Lebofsky M. J.
Published: July 2016

A program to search for luminosity evolution of giant elliptical galaxies at high redshift has been begun at 2.2μm. Observing at infrared wavelengths offers the possibility of avoiding large and uncertain K corrections at redshifts near 1. First results of this program are in agreement with conclusions drawn from much larger optical studies, and demonstrate that luminosity evolution may be present.
The Spectrum of the Microwave Background
Authors: Richards P. L. , Woody D. P.
Published: July 2016

The spectrum of the microwave background radiation closely resembles that of a blackbody with a peak at 6 cm−1. Many experimenters have contributed to the determination of this simple but important fact. In this review we describe the experimental difficulties which have plagued background measurements in the high frequency Wien region. An evaluation of the present status of our knowledge of the entire spectrum will be given and prospects for future experiments will be mentioned.
The Magnetic Structure of Plages
Authors: Zirin H.
Published: July 2016

Every sunspot group is surrounded by regions of weaker magnetic field; traditionally those parts which appear in emission in resonance lines are called plages. There is a more extensive region of enhanced magnetic field which is not bright because the magnetic field is horizontal; this region is easily discernible by dark horizontal fibrils in Hα and is included in our discussion. The plage includes most of the magnetic field in an active center and is the locus of most of the flares.
The Relation between Chromospheric and Photospheric Structures in Sunspot Groups
Authors: Bumba V. , Ambrož P.
Published: July 2016

Using the high resolution photographs of the photosphere taken at the Ondřejov observatory a comparison of positions and forms of some chromospheric features with the distribution of photospheric fine structure morphological elements in the August 1972 active region has been made. The close relationship between active filaments, chromospheric threads, fibrils and photospheric small nuclei, dark interpenumbral and intergranular spaces or rudimentar penumbra is shown. Some considerations are demonstrated with the aid of computed models of the horizontal component of the magnetic vector simulating the real distribution of magnetic fields in the studied region.
Streaming Magnetic Features near Sunspots
Authors: Vrabec Dale
Published: July 2016

Observations prompted by Sheeley's discovery of outflowing CN bright points from sunspots have established that there occur small moving magnetic features (MMF's) near sunspots. These MMF's exhibit a highly ordered pattern of movement directly related to the associated sunspot. The observations are consistent with the concept of magnetic flux outflow (MFO), a process whereby net magnetic flux of the same polarity as the sunspot is transferred from a decaying sunspot to the surrounding magnetic network. Small magnetic flux concentrations are apparently convected outward by a velocity cell centered on the sunspot. Doppler spectroheliograms have provided evidence for such systematic outward velocities extending as far as 10000 to 20000 km beyond the outer edge of the penumbra of some sunspots, which is comparable to the extent of MFO. While MFO is best observed by means of time-lapse movies of the magnetic fields, it is also manifested morphologically on individual magnetograms by features that resemble moats (or bays) and wreaths around only those sunspots where MFO is present. Two examples of magnetic features streaming toward and into rapidly forming sunspots are described, providing evidence for the occurrence of magnetic flux inflow (MFI) associated with the growth phase of sunspot development. It is, therefore, likely that MFI and MFO are basic aspects of the evolutionary development of sunspots. Observational and instrumental aspects relevant to the investigation of MMF's are described in the Appendix.
Evolution of Chromospheric Fine Structures on the Disk
Authors: Tanaka Katsuo
Published: July 2016

Evolution of chromospheric fine structures is discussed from observational points of view. First, various lifetime determinations are reviewed. Then chromospheric oscillation in the interior of supergranule cell is discussed in relation to chromospheric ‘grain’ structure. We show that the grains are collectively associated with the 180-s oscillations as well as that in K line the grain is identified with local disturbance generated at lower level and propagating to upper levels. Finally the details of evolution of individual mottles are presented. We show some cases which indicate the propagation of a disturbance along the mottle axis. Statistics of evolution patterns of mottles implies a significant tendency for a system of double dark mottles encasing a bright mottle.
A Magnetic Model of the Chromosphere-Corona Transition Region
Authors: Gabriel A. H.
Published: July 2016

The structure of the quiet solar atmosphere is dominated by effects due to the magnetic field distributions produced by field concentrations at the supergranual boundary regions. This effect has been studied by previous workers (Kopp and Kuperus, 1968, Kopp, 1972), and is also evident in the enhanced intensity at the SBR's of spectral lines formed in the upper chromosphere and transition region. An attempt is being made to evaluate the field distributions more precisely, taking into account the physical processes involved in the interactions between the field and plasma, and thereby to predict the intensity distributions expected for the EUV spectra. This work is not yet complete, but some important results can be foreseen.
New Impetus to Astrometry
Authors: Fricke Walter
Published: July 2016

In 1964 a conference was held at Flagstaff, Arizona, in honour of Ejnar Hertzsprung. At this conference Martin Schwarzschild presented the inaugural address. The title was ‘New Impetus to Astrometry’. I was so much impressed by everything what he, as an astrophysicist, had to say that I have always remembered his analysis of important astrometric problems with admiration. Nine years after the Flagstaff Conference, I find it appropriate to open this Symposium in referring to Schwarzschild's lecture and in presenting my views on recent developments and on progress which I expect in the future.
Observations Relevant to the Improvement of the Fundamental System
Authors: Gliese W.
Published: July 2016

Since 1950 about 150 observational catalogues have become available which may contribute to the improvement and extension of the FK4. Twenty-five of these have been classfied as ‘absolute’ or ‘quasi-absolute’ by their authors. Part of the observations, however, are not yet available in publications or in a form suited for data processing. Some of the absolute observations in R.A. suffer from insufficient determination of the azimuth and others in Decl. from unclear elimination of flexure. Main deficiencies in the system of the FK4 are inaccurate positions and proper motions in right ascensions south of − 35°.
Report on the Yale-Columbia Southern Proper Motion Program
Authors: Wesselink A. J.
Published: July 2016

This program is best introduced by saying that it constitutes the southern counterpart of the well known Lick proper motion program. In fact, it has been designed to be almost identical to that so that when the work on the materials from both hemispheres has been completed, a homogeneous set of data will be available for the entire celestial sphere.
Proper Motions of OB Stars in Both Hemispheres
Authors: Yasuda Haruo
Published: July 2016

From a comparison between the rotational velocities derived from radial velocities and space motions of OB stars, large systematic errors of FK4 proper motions in the southern hemisphere are evaluated; these may be expected, from the known accuracy of the FK4. The error of adopted distance scale is also examined. It is suggested that meridian observations of OB stars should be extended to the southern hemisphere to further researches, not only on stellar kinematics, but also on the fundamental system.
Que pourra-t-on deduire des mesures de distance terre-lune par laser?
Authors: Kovalevsky J.
Published: July 2016

Although several lunar laser ranging stations exist, only one is now fully operational: the McDonald station with internal observational errors of less than 15 cm. The interpretation of the data involves a great number of parameters relative to the Earth and the Moon which are listed.

The lunar laser is particularly fit for those parameters that pertain to the Moon, and with future lasers accurate to 2 or 3 cm, it may be expected that this accuracy will be projected into these parameters. The probable determination of the semi-major axis to 1 cm accuracy for a few months mean would imply a new means of determining the non conservative part of the motion of the Moon. A similar precision is to be expected for the rotation of the Moon. The situation for the Earth parameters (Earth rotation and polar motion) is not so good, because of a rather weak geometry of the problem and the monthly one week gap in the observations. Nevertheless, it will give a very useful external check on other competing methods (radio-interferometry, laser or radio-satellites).
A New High Speed Measuring Machine for Astrometric Plates
Authors: Routly P. M.
Published: July 2016

A new ‘Starscan’ measuring machine has been built by Optronics International, Chelmsford, Mass., to specifications drawn up by the U.S. Naval Observatory. The accuracy and speed of operation of Starscan have been optimized for the measurement of astrometric plates. The following features in the design and operation of Starscan are discussed: (a) the granite stages, (b) interferometric stage position encoders, (c) the star centroid and integrated opacity detector, (d) the image profile display system, and (e) the function of the computer in machine control and data manipulation. The performance of Starscan, in terms of operating speed and accuracy, is reported for astrometric plates.
Star Positions from Overlapping Plates in the Cape Zone −40° to −52°
Authors: Clube S. V. M.
Published: July 2016

A modification of the normal regression models used for the determination of star positions is described. Some preliminary results relating to accuracy are given.
The Yerkes Observatory Photoelectric Parallax Scanner
Authors: van Altena W. F.
Published: July 2016

A photoelectric parallax scanner designed and constructed at the Yerkes Observatory to measure parallaxes and proper motions at the telescope is described. The concept of the parallax scanner is similar to Griffin's radial velocity spectrometer except that the parallax star and the field stars are monitored separately, thus making the technique purely differential. Observations with the 40-in. refractor under less than ideal conditions gave the error of a single measurement as ±4.5 μ (s.e.). Observations under clear skies and with improved drive and guidance should decrease the error by a factor of 2 to 3.
On Inconsistencies Found in Long-Term Parallax Series
Authors: Heintz W. D.
Published: July 2016

Two recent papers (Hershey; Gatewood and Eichhorn; Astron. J., 1973) pointed out that:

(1) A proper motion irregularity interpreted as orbital motion was found duplicated in another field.

(2) The discontinuity found at one telescope failed to be confirmed by others, and might be ascribed to mere instrumental errors.

After the duplication was discovered two years ago, further measurements have revealed an identical pattern in at least seven parallax stars. Yet the cause of the effect, and the reason for its absence in other cases, have not been located. Colour effects and filter problems appear to be ruled out. Indications for discontinuities occurring at other epochs were found. Thus, the question cannot yet be safely answered whether the small variations (one or two micron) of proper motions reported in some cases are spurious; in any case, great caution should be exercised in interpreting one-micron effects unless confirmation from another instrument is obtained.
Stability Theory in Celestial Mechanics
Authors: Moser J.
Published: July 2016

This expository lecture surveys recent progress of the stability theory in Celestial Mechanics with emphasis on the analytical problems. In particular, the old question of convergence of perturbation series are discussed and positive results obtained, in the light of the work by Kolmogorov Arnold and Moser. For the three body problem, classes of quasi-periodic solutions and doubly asymptotic (or homoclinic) orbits are discussed.
Can the Solar System be Quantized?
Authors: Barnothy J. M.
Published: July 2016

It is suggested that the general form of the constant of quantization, K in Schrödinger's equation, is not h/2π, but K=2sα-k, with s being the spin of the orbiting object, α the fine structure constant (1/137.0361), and k a small positive integer, or zero. For atoms k = 0; for planets and satellites k = 2, 3 or 4; for the solar system as a whole, revolving around the center of the Galaxy, k = 6. The probability that 16 objects of the solar system would follow this quantum rule by chance alone is 1 in 1016, suggestive that quantum mechanics, as we know it today, can be seen as a special case of a more general quantum mechanics of the future; it also supports the view expressed by Dirac, that h is probably not a fundamental constant.

Section 1 contains the basic idea which induced me to undertake an investigation of a relationship between rotational and orbital angular momenta of planets; Sections 2–7 contain the experimental data, the application of the new quantum rule and the statistical evaluation whether the relationship proposed in Section 1, could have occurred by chance alone. The results obtained in Sections 2–7 are noteworthy in themselves, independently whether the basic idea is accepted or not.
The Motion of Comet Westphal in 1852–1974
Authors: Belous L. M.
Published: July 2016

Two apparitions of Comet Westphal in 1852 and 1913 have been linked on the basis of 101 observations, the mean errors being equal to ±2″55. The perturbations from nine major planets and the possible influence of nongravitational forces have been taken into account. The elements and the ephemeride for 1974 have been computed.
Sur un invariant intégral du problème des n corps: Conséquence de l'homogénéité du potentiel
Authors: Losco L.
Published: July 2016

An integral invariant is a generalization of first integrals to differential forms. Although this mathematical technique is more difficult, the integral invariants allow to obtain new properties for systems which have already well-known first integrals. Integral invariant of first order correspond to a ‘local first integral’ near any solution of motion. In this work I obtain an ‘11th local first integral’ for the gravitational n-body problem, or any homogeneous n-body problem as planetary systems. As this local first integral contains a secular term, a discussion of the stability is obtained. The integral invariant is used for the construction of very particular solutions (Levi Civita's or Poincaré's singular solutions). These solutions realize conditional maximum or minimum of the contraction of the system.
Numerical Experiments on Expanding Gravitational Systems
Authors: Janin G. , Haggerty M. J.
Published: July 2016

It has been suggested that particle positions in expanding N-body gravitational systems may become increasingly correlated. Such incoherent density fluctuations could develop into bound clusters. Similarly superclusters of such clusters may be dynamically created. We present results of explorations of this idea, using computer simulation. Accurate integrations are made of gravitationally interacting systems of a few hundred particles.
Classification of New Spectral Lines of Fe XVII Observed in Solar Active Regions
Authors: Hutcheon R. J.
Published: July 2016

This summary reports new emission lines of Fe XVII observed in two coronal active regions (McMath regions 12624, 12628). The lines were recorded by a Bragg plane crystal spectrometer collimated to 3′ FWHM, with a gypsum crystal scanning the wavelength range 8–14 Å. This spectrometer, part of a three spectrometer package previously used by Parkinson (1972, 1973), was mounted aboard a Skylark rocket (SL 1206) launched from Woomera at 0535 UT on 26th November 1973. One of the active regions studied (12624) was observed about 60 minutes after the peak of an importance – N class CO flare.
Measurements of A Gamma-Ray Burst above 1 MeV
Authors: Koga R. , Simnett G. M. , White R. S.
Published: July 2016

Observations of a burst of gamma radiation, starting at 201247 UT, 1972, May 14 are reported. The measurements were made with a 0.5 m2 actively shielded scintillator which was the front element of a double Compton telescope, during a balloon flight at an altitude of 5 mb from Palestine, Texas. The maximum intensity of the burst was 0.10±0.02 cm-2 s-1 above 1 MeV, and the duration was 3.5±0.4 min. The burst intensity during the first 2 min is constant to within 10%. No known electronic or detector malfunction could have produced this effect, and we believe it is a real event.
Detection of Submillimeter Lines of CO (0.65 mm) and H2O (0.79 mm)
Authors: Phillips T. G. , Kwan John , Huggins P. J.
Published: July 2016

The 91.5 cm telescope of NASA's Kuiper Airborne Observatory has been used, in conjunction with an InSb heterodyne receiver, to detect the J = 4-3 submillimeter transition of CO (461 GHz) and the 414−321 transition of H2O (380 GHz). The water emission was detected from the Orion “plateau” region.
New Detections of Spectral Lines in the Frequency Range 260-285 Ghz
Authors: Erickson N. , Davis J. H. , Evans N.J. , Loren R. B. , Mundy L. , Peters W.L. , Scholtes M. , Bout P.A. Vanden
Published: July 2016

The upper half of the frequency band lying between the atmospheric water lines at 183 and 323 GHz is virtually unexplored by spectroscopists of interstellar matter. The only published observations are those of Huggins et al. (1979) who detected the J=3-2 lines of HCN, HNC, and HCO+ in the Orion A molecular cloud (OMC-1). We report here the results of extensive observations made in March and April of 1979 with a University of California (Berkeley) receiver on the Texas 4.9-m antenna.
Radio-Frequency Observations of Interstellar CH4 and HC5N
Authors: Fox Kenneth , Jennings Donald E.
Published: July 2016

We detected new 12CH4 transitions at 21,303 and 94,089 MHz in emission from Orion A, and observed temporal variations of intensity among several velocity components at 76,700 MHz. We also detected an HC5N transition at 21,301 MHz in emission from IRC+10216.
Observations of HC5N (J=12-11 and 13-12) and HC7N (J=28-27), Including a Detection of B335
Authors: Hjalmarson Å. , Friberg P.
Published: July 2016

The Onsala 20 m telescope, equipped with a travelling wave maser (frequency range ∼29-35 GHz; zenith system noise temperature ∼90-160 K) has been used in a search for HC5N (J=12-11 and 13-12) and HC7N (J = 28-27) to a low detection limit. In addition to observations of the Taurus dust clouds TMC1, TMC2 and L1544, the HC5N (J =13-12) transition has been detected at a low level (TA∗ ∼ 0.1 K; p-t-p noise ∼ 0.1 K for a velocity resolution of 0.04 km s-1) in the isolated globule B335. The total HC5N column density estimated from the very narrow line (Δv ∼ 0.2 km s-1) is 6·1011 cm-2. From our non-detection of HC5N in L134N a total column density ≲ 5·1011 cm-2 is deduced.
Ammonia Observations of the Molecular Cloud Near S106
Authors: Little L.T. , Macdonald G.H. , Riley P.W. , Matheson D.N.
Published: July 2016

The region surrounding the optical nebula S106 has been mapped in the J=1,K=1 (1,1) transition of ammonia with a 2.2 arc min. beam. The source is observed as two components with the HII region sandwiched between them. It is likely that the asymmetry of the optical nebula is produced by preferential escape of u.v. radiation from the central source of excitation in directions of reduced density within the molecular condensation. Observations of the (1,1) and (2,2) transitions yield a kinetic temperature for the NH3 molecules in the range 18-22K. There is evidence for “clumpiness” in the distribution of matter.
The Core of a Quiescent Cloud, L183
Authors: Walmsley C. M. , Ungerechts H. , Winnewisser G.
Published: July 2016

Simultaneous observation of the J,K=1,1 and 2,2 inversion transitions of ammonia (NH3) with high spatial resolution (≲1 arc min) offers a powerful method of probing the core region of interstellar clouds for evidence of molecular clumping and of prevailing physical conditions which could lead to star formation. We have therefore used the Effelsberg 100-m radiotelescope to make an extensive study of the central region of the nearby dark dust cloud L183 (also known as L134N) in the NH3 (1,1) transition; the spatial resolution was 40 arcsec. The core region as mapped in the NH3 (1,1) transition with a velocity resolution of 0.08 km s-1 consists of two elongated condensations separated by about 2 arcmin in north-south direction (see Fig. 1). The central part of the NH3 cloud has an approximate dimension of 6′ (N-S) by 2′ (E-W) corresponding to a linear extent of 0.17 × 0.06 pc at an assumed distance of 100 pc. The measured velocity structure of the NH3 cloud seems to reflect the double peaked nature of the cloud in that it increases from 2.30 km s-1 in the south to about 2.5 km s-1 at the northern end of the southern NH3 peak, and then decreases again to 2.3 km s-1 towards the north. The intrinsic linewidths of NH3 (corrected for hyperfine blending) do not vary significantly with position and are between 0.2 and 0.3 km s-1. The two ammonia peaks are part of a central molecular ridge from which we have observed NH3 (2,2) emission at 9 positions (see Fig. 1). The rotation temperature T21 as determined from the optical depths of the (1,1) and (2,2) transitions is ∼9K for all positions, and hence the kinetic temperature Tkin seems close to this value as well, i.e. ∼10K throughout the central part of L183. A more detailed account is being publsihed elsewhere (Ungerechts, Walmsley and Winnewisser).
Surveys of the 4.8 Ghz Formaldehyde Absorption Line in Dark Clouds in M17 and NGC 2024
Authors: Minn Y. K.
Published: July 2016

The 4.8 GHz H2CO absorption line was mapped in the directions of the dark clouds in M17 and NGC 2024. The observations were made with a beamwidth of 6.6 arc min and a velocity resolution of 0.12 km s-1.
In Search of ≲ 5 K Galactic Molecular Gas
Authors: Rubin R. H. , Evans Neal J. , Zuckerman B.
Published: July 2016

Existing surveys of our galaxy are able to detect CO clouds with an excitation temperature Tex ≳ 5 K. We have made observations to determine if a substantial molecular component is colder than ∼ 5 K. We compared CO emission features with H2CO absorption against 17 continuum sources near the galactic plane. After elimination of features in the spectra that are probably associated with known H II regions, there were 39 clouds remaining, most of which show an excellent kinematic agreement between H2CO and CO. The results do not suggest the existence of a large amount of mass in ultra-cold molecular clouds.
CO Observations in the Southern Hemisphere
Authors: Gillespie A. R.
Published: July 2016

CO maps of areas around HII regions show many secondary hotspots. J=2-1 observations of 2 dark clouds are discussed.
A Nearby Example of a Giant Molecular Cloud
Authors: Barrett J. W. , deZafra R.L. , Sanders D. B. , Solomon P. M.
Published: July 2016

We have mapped an extensive molecular cloud in Perseus in the 115 GHz line of 12CO. Observations were made every 10′ in right ascension and declination over most of the cloud, and every 2′ in the regions of most intense emission, near the open cluster IC 348 and near the reflection nebula NGC 1333. We also obtained 110 GHz 13CO data every 2′ in the latter regions, as well as every 10′ in several long strips across the cloud. A total of 812 positions were observed in 12CO, and 200 in 13CO. This work was done using the 5 m antenna of the Millimeter Wave Observatory of the University of Texas. The half-power beam size was 2!6.
The Galactic Rotation Curve to R = 18 Kpc
Authors: Blitz Leo , Fich Michel , Stark Antony A.
Published: July 2016

The major stumbling block in the determination of a rotation curve beyond the solar circle has been the lack of a suitable set of objects with well defined and independently measured distances and velocities which can be observed to large galactocentric radii. Two things have changed this situation. The first was the realization that essentially all local HII regions have associated molecular material. The second was the acquisition of reliable distances to the stars exciting a sizable number of HII regions at large galactocentric radii (Moffat, FitzGerald, and Jackson 1979). Because the velocity of the associated molecular gas can be measured very accurately by means of radio observations of CO, we have been able to overcome the past difficulties and have measured the rotation curve of the Galaxy to a galactocentric distance of 18 kpc.
Far Infrared Laser Magnetic Resonance Spectroscopy
Authors: Evenson K. M. , Saykally R. J.
Published: July 2016

Within the last few years, laser magnetic resonance (LMR) has emerged as a powerful technique for the study of pure rotational spectra of transient species in the gas phase. The sensitivity of this method is considerably higher than that of competing techniques, such as conventional optical and microwave spectroscopy and gas-phase EPR, while the resolution attainable is comparable with that of the latter two methods. Its domain of applicability presently includes atoms, ground states of molecules with up to 5 atoms, and most recently, metastable molecular electronic states in the millisecond lifetime range, and molecular ions. The only rigorous constraint on this applicability is that the species of interest must be paramagnetic.
Charge Exchange and Fine Structure Excitation in O-H+ Collisions
Authors: Chambaud G. , Launay J. M. , Lévy B. , Millié P. , Roueff E. , Minh F. Tran
Published: July 2016

The charge - transfer reaction between protons and oxygen atoms is critical to the chemistry of the oxygen family; the corresponding rate was evaluated by Field and Steigman (1971) on the assumption of orbiting collisions and statistical probability distribution among the levels. We re-examine this reaction, including the fine-structure excitation process, basing our analysis on a careful description of the different potential curves arising from the O-H+ and 0+-H systems and on the evaluation of the coupling responsible for the transitions.
Gas Phase Synthesis of Amino-, Cyano- and Nitroso-Compounds in Interstellar Clouds
Authors: Adams Nigel G. , Smith David
Published: July 2016

From our laboratory data relating to several hundreds of ion-atom and ion-molecule reactions at thermal energies, we qualitatively describe probable chemical paths to the synthesis of amino-, cyano-and nitroso-compounds in interstellar clouds.
Correlations between the λ2200 Feature, the Diffuse λ4430 Band and EB-V
Authors: Danks A. C.
Published: July 2016

The λ2200 extinction feature has been measured from ANS observations of 30 stars. For each star, the depth of the λ2200 feature is compared to EB-V and the equivalent width of the diffuse band λ4430.

A good correlation appears out to EB-V = 1.13. The various mechanisms for producing the diffuse and λ2200 features are discussed, and a discriminatory test is put forward based on observations of the Magellanic Clouds.
CO Isotope Line Shapes in Dark Clouds
Authors: Myers P. C. , Buxton R. B. , Ho P.T.P.
Published: July 2016

The ratio of ground-state densities Ro ≡ N (13CO) / N (C18O) has been used to infer physical and chemical conditions in giant molecular clouds (Wannier et al. 1976) and dark clouds (Mahoney et al. 1976; Langer et al. 1979). In dark clouds Ro is found to vary from values near the terrestrial ratio [13C] [16O] / [12C] [18O] ∼ 5 at positions of high extinction to values ∼20 at positions of low extinction. In this paper we present high-resolution J = 1 → 0 spectra of CO, 13CO, and C18O at positions of high extinction in TMC-2, L134, and L134N. The C18O lines have non-Gaussian wings and are ∼ half as wide as the 13CO lines. We find that RO must vary across the line, from a minimum of R0 ∼ 4 at the peak of the C18O line to a maximum of RO ∼ 10 in the wings, unless the 13CO line has peak opacity ∼5. The variation of RO with position and with velocity is consistent with models of clouds which have a dense core with low velocity-dispersion and low fractionation, and a rarefied envelope with high velocity-dispersion and high fractionation.
Isotopic Fractionation in Interstellar Carbon-bearing Molecules Unrelated to Carbon Monoxide
Authors: Vanýsek V.
Published: July 2016

The isotopic abundance ratio 12C/13C in some carbon-bearing molecules is discussed in the context of chemical fractionation via ion-molecule and exchange reactions in dense interstellar clouds. These processes can lead to enhancement of 12C in molecules not related to carbon monoxide. The effect is transient and takes place preferentially outside the cores of the interstellar clouds. However, some enhancement of 12C should remain in gases frozen onto dust grains and may be reflected in larger objects such as cometary nuclei.
Theoretical Considerations of Shock Wave Behavior
Authors: Hollenbach David
Published: July 2016

Interstellar shock waves have a significant influence on the structure and dynamics of interstellar matter and probably trigger star formation in suitably dense regions. In this paper the overall structure of regions near shock waves is reviewed. In addition we discuss the main observational effects of shocks on interstellar molecules, including: (i) acceleration to velocities 1 km s-1 < vs < 100 km s-1 relative to the ambient gas, (ii) excitation of infrared lines in the heated postshock gas, and (iii) production of high abundances of certain molecular species such as H, OH, H2O, CH+, OCS, and SiO through high temperature chemical reactions in the T ≳ 1000 K postshock gas. The molecular region around the BN infrared source in Orion and the high velocity molecules in IC443 are discussed as possible examples of shocked molecular gas.
Observational Characteristics of Masers Associated with Stars
Authors: Snyder Lewis E.
Published: July 2016

OH, H2O and SiO are the 3 known molecular masers associated with stars. The known transitions, their line profiles, radial velocities, temporal intensity variations and polarization properties are discussed. Current work on determination of circumstellar shell sizes is reviewed. Possible future research topics are outlined.
Vibrationally Excited Silicon Monoxide Masers
Authors: Buhl D. , Clark F. O. , Chin G. , Glenar D. , Kostiuk T. , Mumma M. J. , Lovas F. J.
Published: July 2016

Published data on a select group of SiO maser sources have been analyzed for velocity variations as a function of phase. No apparent correlation was found to a level of about 2 km/s. This places constraints on the location of the maser molecules. Such a correlation should be present at some level. The implications for future high resolution infrared measurements are discussed.
Polarized Emission in the Broad SiO Feature from R Leo
Authors: Clark F. O. , Johnson D. R. , Troland T. H. , Heiles C. E.
Published: July 2016

Linearly polarized SiO emission spread over 12 km/s has been detected from the star R Leo. The position angle of polarized emission varies systematically with respect to the spectral line center. Interpreted in terms of radiative transfer theory, this change in position angle may be due to magnetorotation, which allows the determination of the magnetic field (9×10−3/cos θ Gauss), and the SiO systemic velocity (−1 ± 2 km/s).
The OH Circumstellar Maser in Late-Type Stars
Authors: Nguyen-Q-Rieu  , Bujarrabal V. , Guibert J. , Omont A.
Published: July 2016

A recent investigation based upon the OH luminosity distribution (Nguyen-Q-Rieu et al. 1979) has shown that Type I OH sources associated with Mira variables (OH Miras) are weak OH sources and are therefore only detected within ∼1 kpc from the Sun. Type II OH-Miras, which are more intense and rarer than Type I OH-Miras, are probably more distant objects. The group of unidentified Type II OH-IR sources probably consists of Type II OH-Miras of high OH luminosity. The IR colour index, which is usually higher for Type II sources, suggests that they have a colder and denser dust shell.
Pumping Mechanisms of OH Masers
Authors: Omont A. , Guibert J. , Guilloteau S. , Bujarrabal V. , Nguyen-Q-Rieu
Published: July 2016

We analyze in detail the pumping of 18 cm OH masers by the overlap of far infra-red lines in HII/OH regions and in circumstellar shells. We present some results of a model of pumping of HII/OH masers by thermal overlap. Pumping by overlap appears to be quite general but very complicated. It can account for the different observed main-line masers. However, other types of pumping, mainly by collisions with H or by near infra-red radiation, are possible if certain conditions are met for the physical and astrophysical parameters.
Acousto-Optic Radiosprectrometers for Mm-Wave Spectroscopy
Authors: Chikada Yoshihiro , Ukita Nobuharu , Inatani Junji , Kaifu Norio , Kodaira Shinji
Published: July 2016

In mm-wave spectroscopy, the acousto-optic spectrometer (AOS hereafter) compares favourably with conventional spectrometers such as filter-banks or autocorrelators. Although its frequency resolution is limited to 20 kHz and its instantaneous bandwidth is limited to several hundred MHz, it has 103 resolvable points. Because of the simplicity and stability of the AOS, it is not difficult to construct and maintain a system of 104 resolvable points by the parallel operation of spectrometers. At Tokyo Astronomical Observatory (TAO) a new AOS has been constructed which is equipped with two different types of TeO2 AO deflectors and provides high resolution (38 kHz) or wide band (220 MHz) spectra. It has 1728 frequency channels (figure 1). Another AOS has been built at Kisarazu Technical College (KTC) for a CO survey at 115 GHz. It has 256 frequency channels and a bandwidth of 230 MHz (figure 2).
Future Spectral Line Research with the VLA
Authors: Johnston K. J.
Published: July 2016

The Very Large Array (VLA) is presently being constructed on the Plains of San Augustine near Socorro, New Mexico by the National Radio Astronomy Observatory. The purpose for which this instrument is being constructed is to produce “radio images” of resolution comparable to that of large optical telescopes. There have already been several “test” observations, some successful, using the partially completed instrument to study the molecular species of OH, H2O, and NH3 with wide bandwidths (200-1500 kHz).
The Effects of Rotation during Star Formation
Authors: Bodenheimer Peter
Published: July 2016

Observations of molecular clouds show evidence of rotation and of fragmentation of subregions of the clouds into multiple stellar or protostellar systems. This review concentrates on the effects that rotation and pressure gradients have in a self-gravitating cloud to cause it to undergo the crucial process of fragmentation. Recent two-dimensional and three-dimensional numerical hydrodynamic calculations have made progress in determining these effects. In most cases the calculations are performed with modest spatial resolution and are limited to isothermal clouds with neglect of viscous and magnetic effects. The combined results of several calculations strongly suggest that rotating clouds that are unstable to collapse are also unstable to fragmentation.
The Role of Magnetic Fields in the Formation of Stars
Authors: Mouschovias Telemachos Ch.
Published: July 2016

We review the role of the interstellar magnetic field: (i) in the formation of interstellar clouds; (ii) in determining critical states for gravitational collapse; (iii) in affecting the collapse and fragmentation of interstellar clouds; and (iv) in resolving the “angular momentum problem” during star formation. Finally, we review the manner in which the field decouples from the matter via ambipolar diffusion; new time-dependent solutions are discussed.
The Formation of Binary Stars
Authors: Lucy L. B.
Published: July 2016

The speed and storage capacity of present-day computers have stimulated the development of numerical techniques allowing the investigation of three-dimensional gas dynamical problems of astronomical interest. Of the problems that can be attacked with these techniques, that of the formation of binaries has historically attracted the greatest interest. Several investigators have therefore tackled this problem, and their efforts will be discussed here insofar as they relate to the formation of close binaries. Earlier work, including the classical investigations of Kelvin, Poincaré, Jeans, and Cartan, have been reviewed by Chandrasekhar (1969) and Tassoul (1978).
Monitor Observations of the Orion SiO Maser
Authors: Ukita Nobuharu
Published: July 2016

Monitor observations of the SiO v=1, J=2−1 transition were made toward the Kleinman-Low infrared nebula. Observations were made from September 1976 to February 1980 with the 6 m mm-wave telescope of the Tokyo Astronomical Observatory. Data were taken with an acousto-optical spectrometer with a frequency resolution of about 50 kHz(Δv=0.17 km s−1).
Numerical Studies of the Fission Hypothesis for Rotating Polytropes
Authors: Durisen R. H. , Tohline J. E.
Published: July 2016

The fission hypothesis suggests that close binary stars form due to global nonaxisymmetric instabilities in rotating, quasistatically contracting stars. We study this hypothesis by using an explicit, donor cell, finite difference 3-D hydrodynamic code with self-gravitation to follow dynamic two-armed instabilities in rapidly rotating polytropes. Typical grids are 32 × 16 × 16 in cylindrical coordinates and assume reflection symmetry about the equator plane and rotation axis. Initial conditions are obtained by applying density perturbations δρ = aρ cos 2ϕ with a = 0.10 or 0.33 to axisymmetric equilibrium models with the same angular momentum distribution but with various values of polytropic index n and of β = T/|W| where T = total rotational kinetic energy and W = total gravitational energy. We find dynamic growth of perturbations when β ≳ 0.30 for both n = ½ and 3/2. To within the limitations of our methods, this agrees well with the classical dynamic stability limit of β ≈ 0.274 for the bar modes of the Maclaurin spheroids. An unstable case with n = 3/2 and β = 0.33 is evolved for about ten initial central rotation periods. The part of the star inside corotation develops into a stable bone-shaped or dumbbell-shaped structure after about three pattern rotations. At about the same time, material outside corotation is ejected in the form of two trailing spiral arms. These arms wrap due to differential rotation, merge into a detached disk, and eventually narrow into a radially expanding ring with slight cos 2ϕ density enhancements. The ring contains 16% of the mass but more than half the angular momentum. The central bone-shaped object is an analog of the Riemann S-type ellipsoids. Fluid circulates dynamically and stably from one knob of the bone to the other. In this sense, the object is probably better described as a triaxial star than as a contact binary. Similar behavior is exhibited by an extensive n = ½ and β = 0.33 evolution. This work was supported by U.S. National Science Foundation Grant AST-7821449.
Pre-Main-Sequence Evolution of Close Binaries with Mass Transfer
Authors: Chen Kwan-Yu
Published: July 2016

The scenario begins with two spherical masses of Roche radii, as given by Paczynski (1971), at a separation of centers, A. The mass flows from the initially more massive star a in rapid rotation to its companion b. The separation changes in accordance with the conservation of orbital angular momentum. The corresponding Roche radius of b is considered to be its radius. The luminosities of the stars are given in the approximate expressions following Schatzman (1963) for convective or radiative equilibrium. The luminosity of b determines the time for a given mass transfer with the use of the virial theorem. This time step and the virial theorem, then, determine the change of the radius of a. The angular speed of a is maintained such that the centrifugal and gravitational accelerations are equal at the equator. If the total angular momentum of the system is conserved, the angular momentum of b can be computed. Initially, b is considered to rotate in synchronism with the orbital revolution. The mass transfer stops when the centrifugal and gravitational accelerations become equal at the equator of b, or when the change in potential energy becomes zero. In the table, Sf is the ratio of final rotational and orbital angular speeds; t is the time interval in 103y; initial Ma is 3 solar masses; Mbi = 0.7 for part 1, and Ai = 32.2 solar radii for part 2.
Evolution of Close Binaries
Authors: Tutukov A. V.
Published: July 2016

Most stars of our Galaxy's disk are double. The existing estimation of duplicity ααrange from ~ 50-70 % (Abt, Levy, 1976, Abt, 1979) to ~ 100 % (Kraitcheva et al., 1978). About half of all stars are close binaries (CB) and hence their components fill their Roche lobes during evolution. This accounts for the constantly increasing interest to their evolution. Several review papers were published in the last years: Paczynski (1971), Tutukov et al. (1975), van den Heuvel (1976), Massevitch et al. (1976), Thomas (1977), Paczynski (1979), Webbink (1979b), Yungelson and Massevitch (1980). The subject matter of close binary evolution is very wide now, therefore, I will limit myself to the review of modern scenarios for evolution of massive (M ≳ 10 M⊙) close binaries (MCBS) and close binaries of moderate (M ≲ 10 M⊙) mass.