bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution of the Cluster X-Ray Luminosity Function
Authors: Perrenod Stephen C.
Published: July 2016

I predict the evolution of the X-ray luminosity function of clusters of galaxies. Predominantly, I treat the assumption that galaxies form first, then cluster purely due to gravitation. I show that the richness distribution of Abell clusters favors this scenario, rather than the protocluster hypothesis. The luminosity function is produced by combining a generalized (for all Ω) Press-Schechter evolutionary mass function for clusters (derived herein) with a power law X-ray luminosity-mass relation; a power law relation is supported by observations of low-redshift clusters.

I find very steep evolution in the luminosity function, and thus in the source counts, for large Ω, and moderate evolution for small Ω. For a variety of models for the gas supply rate to the intracluster medium, the evolution of the luminosity function does not vary greatly. Thus it appears that the Ω, dependence will dominate and that number counts of X-ray clusters will yield cosmological information. The power of a test of Ω with an evolving luminosity function is considerably enhanced relative to a test which involves solely global cosmological effects on a non-evolving population. This occurs because of the well-known result that, at late times, clustering tends to proceed slowly for universes of small Ω and rapidly for large Ω.
Extragalactic Work with IUE
Authors: Penston M. V.
Published: July 2016

The International Ultraviolet Explorer (IUE) is an 18 inch (45 cm) space telescope for ultraviolet spectrophotometry in geosynchronous orbit and is a joint project of the European Space Agency, the American National Aeronautics and Space Administration and the British Science Research Council. (Boggess et al. 1978 ab). It is a small instrument to use for objects of truly high redshift and therefore IUE observations relevant to extragalactic astronomy in general will be covered here.
Identification of Infrared Sources in “Empty” Fields
Authors: Rieke G. H. , Lebofsky M. J.
Published: July 2016

From infrared observation of a radio selected sample of QSOs, it is shown that optical identification programs produce samples biased against very red sources, even if identifications are made without regard to color.
Infrared Observations of Giant Elliptical Galaxies: (V-K) Colors and the Infrared Hubble Diagram
Authors: Grasdalen Gary L.
Published: July 2016

The (V-K) colors of giant elliptical galaxies as a function of redshift are discussed. Present data are consistent with mild color evolution at z ~ 0.45. An infrared Hubble (redshift-magnitude) diagram is given. Cosmological models with qo = 0 and no luminosity evolution are clearly excluded by the present data. A wide variety of models including those with qo = 0 are permissible if luminosity evolution is included. Instrumental and programmatic implications of these results are summarized.
Scattering of the Microwave Background in Clusters of Galaxies
Authors: Lake George
Published: July 2016

Evidence from X-ray observations of clusters of galaxies suggests that they contain intergalactic plasma at a temperature of approximately 108 K which emits thermal bremsstrahlung (cf. Lea et al. 1973). Although numerous models for the origin and distribution of the plasma have been presented (cf. Gould and Raphaeli 1978), the amount and distribution of the plasma is still not certain. Several years ago, Sunyaev and Zel-dovich (1972) pointed out another observable consequence of hot gas in clusters of galaxies: inverse Compton scattering by electrons in the plasma would increase the energy of photons of the microwave background as these photons pass through the cluster. The fractional change in intensity of the microwave background is:
Further Observations of the Structure of the Chromosphere-Corona Transition Region from Limb and Disk Intensities
Authors: Burton W. M. , Jordan C. , Ridgeley A. , Wilson R.
Published: July 2016

Further observations of limb and disk intensity ratios of emission lines in the EUV solar spectrum were obtained on a Skylark rocket flight on 5 August 1971. Analysis of the data has shown that the observations support the existence of a steep rise in temperature in the transition region between Te ~ 6 × 104 K and 3 × 105 K. The average absolute height of the transition region above the visible limb has been measured with a greater accuracy than previously possible and is 1700 km ± 700 km. An independent method using arc-length measurements of spectrum lines gives an absolute height of 2100 km ± 850 km. Emission from lines which are optically thick in spicules is observed to extend to heights of 10000 km above the transition region. The observed decrease of Fen emission with height is consistent with current spicule statistics.
Non-Static Structure of the Chromosphere-Corona Transition Region
Authors: Delache Philippe
Published: July 2016

The emission measure Ne2 dh, which is so useful in reducing XUV as well as radio data, is redefined as f(T) dT where f(T) is called ‘thermal emission measure’. Theoretical predictions for f(T) on the basis of a simple, one dimensional, steadily expanding atmosphere are presented. Depending upon the boundary conditions, and essentially upon the mass flux, two very different behaviours show up.

(1)

With a mass flux compatible with an extrapolation of the solar wind flux, f(T) would correspond to a transition region controlled by a constant conductive flux. It can be fitted, as was shown e.g. by Athay (1966), with the XUV observations of the integrated disk for lines formed at temperatures higher than about 2 × 105 K.

(2)

But only with a mass flux enhanced by a factor of 50 to 100, can we interpret the radio spectrum and the XUV observations of lines formed at temperatures less than 2 × 105 K.

The suggestion is made that a single model can reconcile both behaviours: below 2 × 105 K the emitting region is squeezed so that it covers 1–2% of the surface that it occupies at higher temperatures where all structures begin to merge, filling the whole corona. This variation with height compares with usual models derived from spatially resolved observations; as usual the underlying magnetic field is expected to support this channelling.
On the Design of Chromospheric Models
Authors: Grossmann-Doerth U.
Published: July 2016

The basic features of the so-called ‘cloud-model’ (Grossmann-Doerth and von Uexküll, 1971) are discussed. The model permits us to derive approximate values of certain properties of the elements of the chromospheric fine structure by comparing the observed profiles of strong Fraunhofer lines with a simple theoretical formula involving four free parameters. The method is only applicable if two basic conditions are met: (1) The absorption coefficient varies with wavelength according to a gaussian with a broadening parameter that is independent of height, (2) the variation of the source function Sv with height is sufficiently small so that
may be replaced by a constant. The validity of these assumptions, in particular the latter one, is discussed. It is shown that in the case of Hα there are reasons to believe that the assumption is valid provided the features are not very close to the limb (sin θ = 0.9 may constitute the border line). There is also some evidence to suggest that the cloud model will not work for the CaII K-line.
Motions of Chromospheric Fine Structures
Authors: Frazier Edward N.
Published: July 2016

This review concerns itself with the measurement of the effects of chromospheric motions and the diagnosis of those motions themselves over approximately the last ten years. The different types of observational techniques are described. The different size regimes of motions are reviewed and their possible effects on observable quantities are discussed. The different types of motion in the lower chromosphere are reviewed, including microturbulence, ‘layered’ motions, and observations and interpretation of asymmetries in the core of the CaII K line. The observation of motions in Hα mottles on the disk and spicules on the limb are reviewed, from the standpoint of both line profile analysis and broad-band measurements. The interpretation of these motions and attempts to construct empirical models of chromospheric fine structures are discussed.
Trapped Oscillations in the Chromosphere in the Presence of a Magnetic Field
Authors: Nakagawa Y.
Published: July 2016

In the presence of a magnetic field, three types of magnetoatmospheric waves - magnetoacoustic mode, magnetogravitational mode, and hydromagnetic mode - can propagate in a stratified atmosphere, in contrast to the propagation of two types of atmospheric waves - acoustic mode and gravitational mode - in the absence of a magnetic field. The exact manner of propagation of the magnetoatmospheric wave is extremely complex, and most studies have been confined to certain specific circumstances, such as an isothermal atmosphere permeated by a uniform magnetic field (McLellan and Winterberg, 1968; Bel and Mein, 1971; Michalitsanos, 1973), and atmosphere in magnetohydrostatic equilibrium (Yu, 1965; Chen and Lykoudis, 1972) and the propagation across a density discontinuity (Stein, 1971).
The Structure of the Prominence-Corona Interface
Authors: Orrall F. Q. , Speer R. J.
Published: July 2016

The relatively cool Hα emitting regions of solar prominences are evidently surrounded by an interface or structure of intermediate temperature that separates them from the surrounding hot corona. At present, very little is known about this prominence-corona interface (hereafter called the PC interface), because most of its distinctive radiation is in the EUV where observations of high spatial resolution have not been available. In this paper we report on studies made on photometrically calibrated monochromatic images of prominences and the surrounding corona recorded on slitless spectra made during the eclipse of 1970, March 7. These were obtained with a rocket-borne Wadsworth spectrograph flown by the consortium group (Speer et al., 1970) and cover the range λλ850–2159 with a spectral resolution of 0.17 Å and a spatial resolution better than 10″ over half the spectrum. They include spectral lines of a number of ionic species from Hi through Nixv. Because each species exists in a rather narrow temperature range, some of the monochromatic images show the low temperature prominence itself; some the coronal structure surrounding it; and some the intermediate structure we have called the PC interface.
On Stars with the most Favourable Background in Observational History
Authors: van Herk G.
Published: July 2016

The stars in the southern hemisphere with the best observational history in meridian work have been identified and listed at Leiden according to their positions in the sky. Variable and double stars and all stars with |b|10° were omitted. The work could be carried out only for the section from 0h to 16h right ascension. The criterion for good observational history was either to have eight or more catalogue entries in the GFH, or to have five or more entries in the Hamburger IdS.
Thoughts on the Future of Photographic Catalogues
Authors: Wood Harley
Published: July 2016

The current astrometric programmes of zone photography and minor planet observations at the Sydney Observatory are reviewed. Future instrumental requirements and resources needed for zone catalogue work are discussed.
Determination of an Extragalactic Radio Source Position Catalogue Suitable for Use in Monitoring Geophysical Phenomena
Authors: Fanselow John L. , Williams J. G.
Published: July 2016

The use of radio interferometric techniques to monitor geophysical phenomena such as UTI-UTC variations, polar motion, and tectonic plate motion requires that there be available a fairly uniform distribution of extragalactic radio sources whose relative positions are known to better than 0″.01. These sources must also have very small proper motion, and not be subject to asymmetric changes in radio structure or to very large variations in intensity. In addition, to facilitate tying this frame of reference to the optical star frames, it is desirable that many of these radio objects have optical counterparts. This paper describes our progress in obtaining such a frame and sets forth our desiderata for further work by radio and optical astronomers.
The U.S. Naval Observatory Parallax Program
Authors: Strand K. Aa. , Harrington R. S. , Dahn C. C.
Published: July 2016

The U.S. Naval Observatory program on trigonometric stellar parallaxes with the 61-in. astrometric reflector has been in progress since 1964. To date 201 definitive and 8 preliminary negligible parallaxes have been published, including the UBV photometry of these stars. Data for an additional 35 stars are still unpublished.

The mean error in position for an image of unit weight is 1.2 μ or 0″.016, of which 0.8 μ originates from the measuring error of the automatic measuring machine.

An error of the parallax of 0″.004 can usually be obtained with 40 or fewer plates and with an average parallax factor of 0.7.

A statistical investigation of the derived parallaxes shows that they are free from significant internal systematic errors.
Report on the Herstmonceux I.N.T. Parallax Programme
Authors: Jones B. F.
Published: July 2016

In 1971 a pilot parallax programme was initiated on the 98-in. Isaac Newton Telescope at the Royal Greenwich Observatory. Nineteen stars between visual magnitude 15 and 19 and of high proper motion were put on the programme. The plates were taken at prime focus through the Wynne corrector. Observations are now complete for two of these stars. Because of time allocations and the desire to observe at maximum parallax factor, observations are made at large hour angles. All stars in each field are being measured on the GALAXY measuring engine and parallaxes and proper motions will be computed for all stars. The fields are being reduced using an overlap reduction technique.
On the Project of a New Fourfold Coverage of the Northern Hemisphere
Authors: de Vegt Chr.
Published: July 2016

The fully inherent information of the AGK 2 plate material, covering the northern hemisphere down to δ= −2.5° with homogeneous epoch and limiting magnitude has not been used to establish the AGK2 catalogue. A new measurement will provide positions for all stars with at least mpg=2 in the FK4 system, yielding an estimated accuracy of σ = 0″.14.

In March 1973 a newly developed zone astrograph for the yellow spectral-region has been set in operation at the Hamburg observatory which would be available about 1975 for a new fourfold coverage of the northern hemisphere. A technical description of the instrument is given. Details of the fourfold plate coverage and the observing program are discussed. As a suitable reference star system the AGK3R catalogue, updated with recently derived proper motions to that epoch, is adopted. A final positional accuracy σ = 0″.11 of the new catalogue is expected. The available epoch difference of 45 years up to that date will then provide proper motions in the FK 4 system with an estimated accuracy of at least 0″.005/a for all stars of the northern hemisphere down to mpg=2.
The Results of Investigations of the Pulkovo Horizontal Meridian Circle (HMC)
Authors: Pinigin G. I. , Sukharev L. A. , Timashkova G. M.
Published: July 2016

The observations in R.A. with the Pulkovo HMC and investigations of the instrument, reported in Trans. IAUXIVA (p. 39), are being continued during the past two years (Pinigin, 1972, 1973). Some of the new results are as follows:
A General Computer Program for the Application of the Rigorous Block-Adjustment Solution in Photographic Astrometry
Authors: de Vegt Chr. , Ebner H.
Published: July 2016

The evaluation of stellar positions from overlapping plates by rigorous block-adjustment methods leads to a very large system of normal equations containing both stellar positions and plate constants as unknowns. These general normal equations can be reduced to a subsystem with banded-bordered coefficient matrix, containing only the plate constants as unknowns. In the case of a large photographic net covering a hemisphere or sphere with multiple overlap of the plates, the actual number of unknown plate constants may exceed 20000, depending on the adopted reduction model.
Distribution of the Mean Motions of Planets and Satellites and the Development of the Solar System
Authors: Jehle H.
Published: July 2016

In this paper the point of view is taken that the distribution of orbital elements in the solar system should be discussed first on a purely gravitational basis, i.e. on the basis of a set of particles entirely under gravitational interaction, before hydromagnetic and other effects are taken in consideration too. One might indeed assume that there has been a time in the history of the solar system from when on hydromagnetic and gas laws ceased to play an important role in comparison to gravity. In the epoch since that time the solar system might have developed from a set of a large number of smaller particles into the present solar system by way of transitions which these particles made to preferential orbital elements, and by accretion. Means had been found to handle the development of this set of particles under gravitational interaction, by defining the set appropriately in terms of a statistical distribution. In considering the problem of the evolution of the solar system, such a gravitational approach, which was encouraged by Einstein, seems the reasonable first step.
The Origin of Commensurabilities in the Satellite Systems
Authors: Dermott S. F.
Published: July 2016

The distribution of orbits in the satellite systems of the major planets is definitely nonrandom as there is a marked preference for commensurability among pairs of mean motions in these systems. If this preference is not the result of a formation process then it follows that since the time of satellite formation dynamical evolution has occurred. In this paper (a full version of which is to be submitted to another journal) I show that there is a bulk of evidence in favour of the hypothesis that orbital evolution has occurred as the result of tidal dissipation in the planets. This evidence can be listed as follows:

(i) In a tidally evolved satellite system there should be a linear correlation between log (orbital radius) and log (satellite mass). The expected correlation is observed among the inner satellites of Saturn and Uranus, the slope of the log-log plots being consistent with an amplitude and frequency independent Q (the tidal dissipation function). The correlation in Saturn's system must be largely due to either a formation process or possibly an early amplitude and frequency dependent tidal process, but certainly the present satellite distribution is completely consistent with the tidal hypothesis.

(ii) If Q is amplitude- and frequency-independent then the Mimas-Tethys and Enceladus-Dione resonances are stable under the action of tidal forces. This is an important result as it indicates that the necessary tidal dissipation occurred in the solid parts of the planets. Whether or not these planets have any solid parts at present is a matter of dispute.

(iii) The tidal hypothesis can account for the formation (capture into libration) of the Mimas-Tethys and Enceladus-Dione resonances.

(iv) If it is allowed that the age of the Mimas-Tethys resonance is not small (> 108 yr) in comparison with that of the solar system and that orbital evolution since the time of satellite formation has been appreciable then it can be shown that tidal forces (with Q amplitude- and frequency-independent) can account for the present large amplitude of libration of this resonance.

(v) If tidal evolution in the satellite systems of Jupiter and Saturn has been appreciable then from the present orbits of Io and Mimas it can be deduced that Q (Jupiter) ~1.1 × 105 and Q (Saturn) ~1.2 × 105. As the masses of the two satellites differ by a factor ~2000 and the amplitudes of the tides they raise on their respective planets differ by a factor ~ 5000 this agreement in the Q-values is somewhat remarkable. But as the stability of the Mimas-Tethys and Enceladus-Dione resonances demands that Q is amplitude- and frequency-independent and as the chemical compositions and structures of Jupiter and Saturn are probably similar then one should expect the Q's of these planets to be similar and thus the result supports the tidal hypothesis.

(vi) Finally, as the values of Q are so very high it would be remarkable if tidal evolution had not taken place.
The Global Solution in the Problem of the Critical Inclination
Authors: Garfinkel B.
Published: July 2016

The problem of the critical inclination in the artificial satellite theory can be regarded as a problem of resonance arising from the near-commensurability 1:1 between the anomalistic and the draconitic frequencies of the motion, n1 and n2. Let us define the main problem by the potential function
(1) with
(2)
On the Calculation of Secular Perturbations in the Case of Close Commensurability
Authors: Lobkova N. I. , Petrovskaya M. S.
Published: July 2016

In a previous paper the authors derived expansions of the derivatives of the disturbing function for the general case including the orbits close to intersection. The present paper deals especially with the case of close commensurability of the mean motions. A new variable v is introduced characterizing the deviation of the mean anomalies from the exact commensurability, and is considered further as an unknown quantity. In the equations of motion the short-period terms are eliminated. The form of expansions of the right-hand sides is chosen basing on the same principles as in the general case. The factors are separated, corresponding to the poles in the case of circular intersecting orbits. For rapidity of calculation the summation in powers of the major semi-axes ratio is made the inner one.
The Role of Binaries in Cluster Dynamics
Authors: Heggie D. C.
Published: July 2016

There is considerable empirical evidence on the behaviour of binary stars in computer simulations of isolated star clusters. Even when there are no binaries initially they form quickly if the mass spectrum of the stars is reasonably realistic. These phenomena are discussed by a combination of analytical and numerical techniques.
On the Disappearance of Isolating Integrals in Dynamical Systems with More than Two Degrees of Freedom
Authors: Froeschlé C. , Scheidecker J.-P.
Published: July 2016

We continue to study the number of isolating integrals in dynamical systems with three and four degrees of freedom, using as models the measure preserving mappings T already introduced in previous papers (Froeschlé, 1972; Froeschlé and Scheidecker, 1973a).

Thus, we use here a new numerical method which enables us to take as indicator of stochasticity the variation with n of the two (respectively three) largest eigenvalues - in absolute magnitude - of the linear tangential mapping Tn∗ of Tn. This variation appears to be a very good tool for studying the diffusion process which occurs during the disappearance of the isolating integrals, already shown in a previous paper (Froeschlé, 1971). In the case of systems with three degrees of freedom, we define and give an estimation of the diffusion time, and show that the gambler's ruin model is an approximation of this diffusion process.
EUV Observations of the Active Sun from the Harvard Experiment on ATM
Authors: Noyes R. W. , Foukal P. V. , Huber M. C. E. , Reeves E. M. , Schmahl E. J. , Timothy J. G. , Vernazza J. E. , Withbroe G. L.
Published: July 2016

In this paper we review some preliminary results from the Harvard College Observatory Extreme Ultraviolet Spectroheliometer on ATM that pertain to solar activity. The results reviewed here are described in more detail in other papers referred to in the text. In the following paragraphs we first describe the instrument and its capabilities, and then turn to results on active regions, sunspots, flares, EUV bright points, coronal holes, and prominences.
Solar Activity Observed in X-Rays and the EUV from OSO 7
Authors: Thomas Roger J.
Published: July 2016

Since 1971 the Goddard X-ray and EUV spectroheliograph aboard OSO 7 has been measuring the spatial distribution and time-variations of localized temperature and density features in solar active centers and flares. In some cases the sizes, shapes, orientations and locations of emitting plasmas at temperatures ranging from 104 K (Hα) to as high as 2 × 107 K (Fe xxv) have now been measured simultaneously. Our observations of active regions are consistent with the coronal structure being made up of nested systems of arches with footpoints in areas of opposite magnetic polarity. Temperatures seem to increase for arches nearer the center and also towards the top of any given magnetic arch, the innermost loops having the highest temperature gradients. There is also some evidence for electric current flow along such loops. Radiative cooling is significant for the region's hot central core which therefore must be maintained by a more or less continuous injection of energy.

A nested arch structure is also indicated for XUV flares of the two-component type, which likewise may require continuous energy input since conduction cooling should otherwise be very rapid. Multiple spikes during the impulsive phase seem to represent the consecutive triggering of different sources within the region and may occur outside of any detectable pre-existing coronal feature. Comparison of spatial distributions at several wavelengths during various stages of flare events provides information on interactions between the wide range of atmospheric levels involved. We have evidence for polarization of about 20% in a number of X-ray bursts, continuing throughout the decay phase. At least for some flares, our measurements seem to contradict the model of electron beams being radially injected into the chromosphere.
Interpretation of the X-Ray Spectra of Solar Active Regions
Authors: Walker Arthur B. C.
Published: July 2016

This paper presents a review of recent analytical studies of the coronal X-ray spectrum below 25 Å. The techniques used to compute the theoretical coronal spectrum, and the currently available atomic rate constant data are reviewed first. Spectroscopic techniques which have been proposed for the determination of coronal temperature and density structure, and the results derived from their application to coronal spectra are also reviewed.

A number of coronal models based on X-ray observations have been developed recently, and the coronal temperature structure and composition predicted by these models is discussed, and compared with models of the corona and transition region derived from studies of the solar EUV spectrum.
Flare-Like Ultraviolet Spectra of Active Regions
Authors: Brueckner G. E.
Published: July 2016

Some characteristic features of UV spectra which can be seen in flares (Brueckner, this Symposium, p. 135) can also be detected in active regions without the presence of typical other flare phenomena like X-ray enhancement. Another distinct difference between these ‘flare-like’ spectra and flare spectra is the absence of very high temperature ions like Fe XXI in the ‘flare-like’ spectra. They occur in small areas and can be detected as ‘fluctuating Hα bright points’ in broad band Hα. Simultaneously, a strong UV brightening can be seen. As reported by the Skylab crews, these brightenings occur more frequently and quasi-periodic prior to flares. Their spectra show the very broad transition zone lines and often strong line shifts toward the blue or red. Figure 1 shows a selection of typical spectra. One notices a very asymmetric Lα profile in one case. Spectra prior to, during, and after a flare are reproduced in Figure 2. One recognizes that the transition zone instability started intermittently prior to the flare and could be seen during short time intervals long after the flare had ceased.
X-Ray and EUV Spectra of Solar Flares and Laboratory Plasmas
Authors: Doschek G. A.
Published: July 2016

Recent laboratory work relevant to solar flares on the spectroscopy of highly ionized atoms is reviewed. Much of this work has concerned the X-ray and EUV spectrum of iron ions, Fe XVIII–Fe XXIV, which produce prominent emission lines in the spectra of solar flares. Also discussed are recently obtained laboratory X-ray spectra of emission lines of hydrogen-like and helium-like ions, and associated satellite lines due to transitions of the type, 1s2l—2p2l, 1s22l—1s2p2l, and 1s22l— —1s2l3p. Satellite lines have also been identified in spectra of solar flares, and can be used to determine the electron temperature of the plasma. The laboratory work is important in the planning of future experiments in solar flare X-ray and EUV spectroscopy.
Studies of the Dynamic Structure and Spectra of Solar X-Ray Flares
Authors: Kahler S. W. , Krieger A. S. , Silk J. K. , Simon R. W. , Timothy A. F. , Vaiana G.
Published: July 2016

Data from the AS & E X-ray spectrographic telescope on Skylab were used for a preliminary study of two solar flares on 1973, August 9 and September 5. Photographic images taken through broad band filters during the early flare onsets and subsequent evolution of the flares were analyzed by microdensitometry and subsequent conversion to energy maps of the flare areas.
Determination of the Height of Hard X-Ray Sources in the Solar Atmosphere by Measurement of Photospheric Albedo Photons
Authors: Brown John C. , Van Beek H. F.
Published: July 2016

The importance and difficulties of determining the height of hard X-ray sources in the solar atmosphere, in order to distinguish source models, have been discussed by Brown and McClymont (1974) and also in this Symposium (Brown, 1975; Datlowe, 1975). Theoretical predictions of this height, h, range between and 105 km above the photosphere for different models (Brown and McClymont, 1974; McClymont and Brown, 1974). Equally diverse values have been inferred from observations of synchronous chromospheric EUV bursts (Kane and Donnelly, 1971) on the one hand and from apparently behind-the-limb events (e.g. Datlowe, 1975) on the other.
Solar Flare X-Ray Measurements and Their Relation to Microwave Bursts
Authors: De Feiter L. D.
Published: July 2016

This review discusses the available observational material of solar hard X-ray bursts, their interpretation in terms of a model of the source region and their relation with other flash-phase phenomena, in particular the impulsive microwave bursts.
X- and γ-Ray Measurements During the 1972, August 2 and 7 Large Solar Flares
Authors: Talon R. , Vedrenne G. , Melioransky A. S. , Pissarenko N. F. , Shamolin V. M. , Likin O. B.
Published: July 2016

The solar X- and gamma-ray experiment aboard Prognoz 2 recorded solar gamma-radiation bursts during the 1972, August 2, 4 and 7 events. This work analyses the general evolution of the August 2 and 7 events and the possible evidence forγ-ray lines during these two events.
High Energy Gamma-Ray Radiation Above 300 KeV Associated with Solar Activity
Authors: Chupp E. L. , Forrest D. J. , Suri A. N.
Published: July 2016

The present status of our knowledge concerning the production of gamma-ray lines and continuum during the impulsive phase of solar flares is reviewed. Our data in this field is based solely on the OSO-7 observations made in 1972, August 4 and August 7. The experimental data will be reviewed. These observations along with theoretical work of Ramaty and Lingenfelter (1973a, b) and the charged secondary observations of the Chicago group (Anglin et al., 1973) lead to the investigation of different hypothetical models to explain the production of neutral and charged secondaries in the solar atmosphere. At the present time it is not possible to rule out the preflare and postflare accumulation models if all the data is considered. We will discuss the outstanding experimental questions to be answered in future investigations.
Physical and Dynamical Conditions in Interstellar Clouds
Authors: Evans N.J.
Published: July 2016

The most far-reaching result to come from the study of interstellar molecules has been the recognition of a new class of galactic structures - molecular clouds. These clouds appear to contain most of the mass of the interstellar medium and are the objects from which new stars are formed. Thus, a prerequisite for any understanding of the star formation process is a knowledge of the physical and dynamical conditions in molecular clouds.
Spectra of the 10-01 Transition of Sulfur Monoxide in Interstellar Clouds
Authors: Rydbeck O.E.H. , Hjalmarson Å. , Rydbeck G. , Elldér J. , Kollberg E. , Irvine W. M.
Published: July 2016

Emission from SO towards a number of HII regions and molecular clouds with embedded energy sources has been reported by several authors (e.g., Gottlieb et al. 1978; Clark et al. 1978; Wannier and Phillips 1977; and references therein; cf. also Loren et al., 1974; Loren et al. 1975; Lada et al. 1974). Transitions observed include the 45→44, 43→32, 32→21, 23→12, 22→11, 12→11, and 10→01, with the latter (to the ground state) seen only in Sgr B2. Recently Rydbeck et al. (1980) have detected SO in cold, dark clouds and have made the first astronomical measurements of the 10→01 transition in a variety of sources, including the corresponding 34SO line. The latter authors find that the 10→01 transition of SO is an excellent tracer of structure in dark clouds, and they discuss the fractional abundance [SO]/[H2] on the basis of column densities derived from observations of the two isotopic species. They also set limits to the magnetic field strength in dark clouds from the absence of observed Zeeman splitting. We shall provide here additional spectra and information on observing procedures, and shall discuss the rest frequencies for the SO and 34SO 10→01 transitions.
Detection of New Ammonia Sources
Authors: Macdonald G.H. , Brown A.T. , Little L.T. , Matheson D.N. , Felli M.
Published: July 2016

Ammonia is a favoured molecule for the study of molecular clouds since several important parameters of the cloud can be deduced from simple observations of the J,K=1,1 and 2,2 inversion doublet transitions and the hyperfine structure in the (1,1) line. With the additional knowledge of the kinetic temperature Tk from observations of CO, for example, it is possible to compute the excitation temperature of the (1,1) line (T11), the rotational temperature between the (1,1) and (2,2) levels (T21), the molecular hydrogen density n(H2) and ammonia column density N(NH3) (see, for example, Martin and Barrett, 1978).
Observations of NH3 Toward DR21
Authors: Pauls T. , Wilson T. L.
Published: July 2016

Figure 1 shows the (J,K) = (1,1), (2,2) and (3,3) spectra of NH3 observed toward the continuum peak of DR21 and four positions offset 50″ from the peak. These observations were made with the Effelsberg 100-m radio telescope, which has a half-power beam width of ∼43″ at these frequencies.
Formaldehyde in L1551, L134 and the Galactic Centre
Authors: Sandqvist Aa. , Bernes C.
Published: July 2016

The formaldehyde molecule is an excellent probe of physical conditions inside interstellar clouds. We illustrate this by presenting results of our recent series of observations using the MPIfR Effelsberg 100-m radio telescope for the 6-cm transition, the NRAO Green Bank 43-m radio telescope for the 2-cm transition and the NRAO Kitt Peak 11-m mm-wave telescope for the 2-mm transition.
Population Inversion and Suprathermal Excitation in Carbon Monoxide
Authors: Köppen J. , Kegel W. H.
Published: July 2016

We have investigated under which physical conditions (kinetic temperature, H2 density, CO column density) the CO molecule shows suprathermal excitation and population inversion. The computations are based on a model in which the excitation is basically due to collisions with H2 molecules. The collision cross-sections were taken from Green and Thaddeus (1976). The radiative transport in the molecular lines is treated in an on-the-spot approximation (see e.g. Kegel 1979)

J = S(1 - e-τ) + Ibge-τ

in order to keep the computing time low enough to permit the investigation of a wide range of parameters. Our approximation of the radiative transfer is mathematically equivalent to a formalism involving an escape probability β = e-τ. This escape probability arises from the fact that the radiative transfer in the line wings is neglected.
The Disruption of the Molecular Cloud Associated with the North America and Pelican Nebulae
Authors: Bally John
Published: July 2016

Giant molecular clouds can be destroyed in several ways: by conversion of gas into stars; by dissociation of H2 into HI; by ionization and formation of HII regions; and by dispersal of the cloud into cloudets. The relative importance of these processes can be assessed by observations of evolved HII regions and associated molecular clouds. A number of such complexes have been studied in 12CO at the Five College Radio Astronomy Observatory (FCRAO) as part of an extensive investigation of clouds associated with about 60 Sharpless HII regions. A particularly clear example of cloud disruption is found in the case of W80, the North America and Pelican Nebulae in Cygnus (Bally and Scoville 1980).
An ICR Study of Ion-Molecule Reactions in the C2H2/HCN System
Authors: Mcewan M.J. , Anicich V. G. , Huntress W.T.
Published: July 2016

Rate constants obtained by the ICR technique are reported for reaction (1), C2H2+ + HCN and reaction (2) HCN+ + C2H2 such that k1 = 3.6 × 10−10 and k2 = 6.9 × 10−10 cm3 molecule−1 s−1, respectively. Differences between these results and other measurements of reaction (1) are discussed. The relevance of reaction (1) to the formation of HC3N in interstellar clouds is also briefly assessed.
The Formation of Interstellar Molecules via Radiative Association Reactions
Authors: Smith David , Adams Nigel G.
Published: July 2016

The radiative association rate coefficients and their temperature dependences have been estimated for several likely interstellar ion-molecule reactions from laboratory collisional association rate data. They include the CH3+ + H2 and CH3+ + H2O reactions, which we suggest lead to CH4 and CH3OH respectively, and the critical association reaction C+ + H2.
Isotope Ratios in Interstellar Formaldehyde
Authors: Kutner Marc L. , Machnik Dennis E. , Tucker Kenneth D. , Massano William
Published: July 2016

Formaldehyde is an excellent molecule for studying isotopic abundances. It is easily observed in several connected transitions, allowing an analysis of excitation differences among species. With formaldehyde, one can also measure the same ratio using millimeter emission lines and centimeter absorption lines, which can often be interpreted more directly. A comparison of the results from the millimeter and centimeter lines can give an idea of the uncertainties in the analysis of millimeter emission lines.
Detection of Deuterated Formaldehyde in Interstellar Clouds
Authors: Langer William D. , Frerking Margaret A. , Linke Richard A. , Wilson Robert W.
Published: July 2016

Deuterated formaldehyde has been detected for the first time in interstellar clouds; the observed ratio HDCO/H2CO implies formation by gas phase chemistry.
The Pumping of Interstellar OH Main Line Masers: an Efficient Mechanism
Authors: Lucas Robert
Published: July 2016

Hyperfine components of the far-infrared lines of OH are separated by velocity intervals ranging from about .6 to 8.0 km s-1 (fig. 1). As early as 1969 Litvak had suggested that overlapping of these components due to either thermal or systematic motions could be the source of OH main line inversion. We investigate here the effects of overlapping due to systematic motions.
Time Variations of Interstellar Water Masers in HII Regions
Authors: White G.J. , Macdonald G.H.
Published: July 2016

Previous studies of time variations in water vapour sources associated with HII regions by Sullivan (1971, 1973) and Gammon (1976) have revealed variability on time-scales of 106-107s. Sullivan monitored nine sources over a period of 14 months and Gammon observed W49 (H2O) for 13 months. In an attempt to gather more complete information on the variability of interstellar water masers we have monitored 18 sources for the 32-month period 1974 September-1977 May. The sources selected are listed in Table 1. They were the strongest known at the beginning of the programme above declination −20°.
Role of Grains in the Drift of Plasma and Magnetic Field in Dense Interstellar Clouds
Authors: Umebayashi Toyoharu , Nakano Takenori
Published: July 2016

The magnetic flux through an interstellar cloud or through a part of the cloud must decrease considerably by the drift of plasma and magnetic field in order that stars form in the cloud. Because most grains are negatively charged in dense clouds (Elmegreen 1979; Umebayashi and Nakano 1980), they retard magnetic flux leakage in addition to ions (Elmegreen 1979). We investigate this effect for different situations and obtain the following results (for details, see Nakano and Umebayashi 1980):

1.

For nearly spherical clouds of mass ≳ 103M⊙ sustained by magnetic force the friction of grains is efficient at nH⊙ ≳ 105 cm−3, and the magnetic flux leakage time tB is greater than a few million years at any density. Grains drift as fast as ions and electrons.

2.

For spherical clouds of smaller mass and disk-shaped clouds, tB becomes much smaller and the drift of grains is much slower than ions and electrons at nH ≳ 106 cm−3.

3.

Thus magnetic flux leakage occurs mainly in the condensations described in 2, and the abundance of heavy elements in stars deviates little from that of the parent clouds because of small grain drift.
Growth and Sedimentation of Dust Grains in the Primordial Solar Nebula
Authors: Nakagawa Yoshitsugu , Nakazawa Kiyoshi , Hayashi Chushiro
Published: July 2016

Of the formation processes of the solar system, the process of growth and sedimentation of dust particles in the primordial solar nebula is investigated for a region near the Earth's orbit. The growth equation for dust particles, which are sinking as well as in thermal motion, is solved numerically in the wide mass range between 10−12 g and 106 g.
Thermonuclear Processes on Accreting Neutron Stars
Authors: Joss Paul C.
Published: July 2016

The observed properties of X-ray burst sources have recently been reviewed by Lewin and Clark (1980) and Lewin and Joss (1980). About thirty-five such sources are presently known, and they have a spatial distribution reminiscent of stellar Population II (see Figure 1). The salient features of these sources include burst rise times of ≲ls, decay time scales of ~3–100 s, peak luminosities of ~1039 ergs per burst, spectra that can generally be well fitted by blackbody emission from a surface with a constant effective radius of ~10 km and a peak temperature of ~3 × 107 K, and “tails” of softer X-ray emission that may persist for several minutes after the burst maximum. Profiles of bursts from some typical burst sources are shown in Figure 2. The intervals between bursts from a given source may be regular or erratic and are typically in the range of ~104−105 s; many sources undergo burst-inactive phases that can last for weeks or months. Most burst sources are also sources of persistent X-ray emission, and the ratio of average persistent luminosity to time-averaged burst luminosity is typically ~102 during burst-active phases. (The properties of the “Rapid Burster,” MXB1730-335, are different from those of all other known burst sources and will be discussed separately in §VI below.) There are few correlations among the burst flux, burst intervals, and persistent X-ray flux from any given source, and the detailed burst shapes vary from one source to another and often vary with time in a given source.
Isotopes in Galactic Cosmic Rays
Authors: Reeves Hubert
Published: July 2016

The data on isotopic ratios of elements in Galactic Cosmic Rays (GCR) is steadily improving and has recently reached the point where some information can be extracted, which has bearing on the problem of the origin of the cosmic rays. By and large, these data have generally confirmed the similarity between solar-type matter and GCR source, when spallation effects and selective acceleration are taken into account. The silicon and iron isotopic ratios, for instance, are consistent with meteoritic ratios. For iron, this is particularly important since two or perhaps even three different nucleosynthesis mechanisms are required to account for the species 54Fe, 56Fe, 58Fe. For carbon, nitrogen and oxygen the problem is that the spallation corrections are large compared to the solar system ratios but nevertheless the present upper limits are not in contradiction with the solar system ratios.
Isotopes of Cosmic Ray Elements from Neon to Nickel
Authors: Waddington C. J. , Freier P. S. , Fickle R. K. , Brewster N. R.
Published: July 2016

We are reporting here on the results obtained from a balloon exposure of a cosmic ray detector flown in 1977. This detector, described elsewhere, Gilman and Waddington (1975), Young (1979), measures elemental charge from scintillation and Cherenkov signals and mass from Cherenkov and total energy determined from a measure of residual range in nuclear emulsion. The charge resolution obtained ranged from 0.19 to 0.21 charge units between neon and nickel. This resolution was sufficient to ensure that all but a few percent of the nuclei were correctly identified, even for those elements of low abundance that have neighbors with high abundances, such as Cl or Al. The mass resolution obtained for those nuclei that stopped in the emulsions ranged from 0.40 to 0.70 amu for A between 20 and 60 amu. This was not adequate to uniquely resolve neighboring mass peaks in many cases, but was adequate to draw a number of conclusions regarding many of the more abundant elements.
Diffusion of High Energy Cosmic Rays from the Virgo Cluster
Authors: Giler M. , Wdowczyk J. , Wolfendale A. W.
Published: July 2016

The origin of the highest energy cosmic rays is unclear but the observation that many are seen to arrive from high Galactic latitudes supports the idea of Extragalactic sources. The characteristic features to be explained by any origin model are: the flattening of the energy spectrum above 1019eV and the apparent presence of a directional anisotropy which increases systematically with energy.
Features of the High Energy Electron Spectrum
Authors: Nishimura J.
Published: July 2016

Recent studies of the spectrum of high energy primary electrons using emulsion chambers have been made with an exposure factor some 10 to 100 times larger than those obtained by other experimental devices. The total exposure is now almost 6 m2-day-str., including the recent exposure at Palestine, Texas in May 1980, and it is now quite possible to extend observations of the electron spectrum into the TeV region with reliable accuracy in the next few years.