bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Effect of Ocean Tides on the Secular Retardation of the Earth's Rotation
Authors: Pariisky N. N. , Kuznetsov M. V. , Kuznetsova L. V.
Published: July 2016

The classical problem of determining the secular retardation of the Earth's rotation due to the effect of tides (oceanic and bodily) has an important geophysical value in determining the possible existence of processes inside the Earth, which lead to secular variations of rotation of the whole Earth or its external layers.

Using new cotidal charts of the world ocean calculated by Bogdanov for the main tidal waves M2, S2, K1 and O1 and using the method of moments of tidal forces the retarding moment was found to be 8.3 × 1023 dyn cm. This is twice the amount of previous evaluations. (This method is superior to the method of calculating the dissipation of energy or the moments of frictional forces). This amount corresponds to a retardation of 3.8 μs/century in the speed of the Earth's rotation. But the observations of the Sun give only 1.9 μs/century for the retardation. Thus, there seem to be nontidal and probably internal processes, which accelerate the Earth's rotation by about 2 μs/century. And this is without taking account of additional smaller effects of bodily tides. The search for these processes is an important problem.

The full text of the paper will be published in the magazine Physics of the Earth, No. 2, 1972.
Spectroscopic Criteria for the Classification of Peculiar B-type Stars with Colour-Spectrum Discrepancies
Authors: Garrison R. F.
Published: July 2016

The so-called ‘weak helium’ stars are discussed from a spectral classification point of view. Several authors have included different kinds of objects in this class. Often, the only similarity is the discrepancy between the spectra and the colours. It is desirable to decouple the discovery of new members of the class from this dependence on colours so that the colour can be used as an independent parameter.
Spectroscopic Observations of the Sanduleak-Seggewiss Stars in NGC 6231
Authors: Milone L. A.
Published: July 2016

Sanduleak and independently Seggewiss discovered a very red star near the open cluster NGC 6231. Bessell and collaborators concluded it to be a variable of the R Coronae Borealis type.

A pair of spectrograms of this object were obtained in July 1970. The spectrograph dispersion in the range of 3800–4500 Å is around 80 Å mm−1 and in the range of 4500–7000 Å 155 Å mm−1.

An outstanding feature of the spectrograms is their ‘veiled’ aspect, making it rather difficult to observe the lines. We observe the 4226 Å of Ca I, H and K of Ca II, 4030/4034 Å of Mn I, the G band; and several lines belonging to the Fe I multiplets. The Hα and Hβ lines are clearly seen in emission. Hδ is absent or very faint. A spectrogram of RY Sagitarii taken in July 16, 1971, when the visual magnitude of the star was around 4 mag. below its maximum light, shows some similarities with the spectrograms of the Sanduleak-Seggewiss star, e.g. they do not show the ultraviolet CN absorption bands and in the spectra of both stars a line is seen at approximately 3896 Å, which may be H8.

If we accept that the star belongs to NGC 6231, its distance modulus is 11.5. Its intrinsic color may be assumed to be close to (B–F)0 = 1.0(G or K star). The observed color is (B–K) = 3.5. Adopting R = 3, the visual absorption is 7.5. As the visual magnitude of the star is V= 12.5, its absolute magnitude becomes – 6.5.

Details will be published elsewhere.
The Bonn Spectral Atlas: Part II
Authors: Seitter W. C.
Published: July 2016

Abstract and Summary

When work commenced on the Bonn Atlas for Objective Prism Spectra some years ago it was our intention to supply a tool for astronomers working with such widely different dispersions and resolutions as are used in the field of objective prism spectroscopy. This was to be accomplished through an atlas which contained and compared spectra of considerable difference in dispersion.

The Bonn Schmidt telescope which is used to obtain the observational material is equipped with three prisms giving linear reciprocal dispersions of 240, 645 and 1280 Å mm−1 at Hγ, thus covering a good part of the range generally used.

The first part of the atlas, containing spectra of the largest dispersion only, was published as soon as it was finished, while work on the second part with the two lower dispersions was still in progress. Thus, one of the main intended features of the complete publication, a comparison of criteria displayed at different dispersions, with a special interest in the appearance and disappearance of certain criteria as one goes from higher to lower dispersions, was not yet possible.

Now, work on the second part of the atlas has progressed far enough for sample pages of the lower dispersion plates to be distributed for inspection and discussion. Plate I gives examples of spectra that will be used on the S-plates (sequences of different spectral types for a given luminosity class) showing both spectra of 645 Å mm−1 (right hand side) and 1280 Å mm−1 (left hand side).

While the first part of the atlas tried to point out as much detail in the spectra as possible to make the atlas applicable for work with even higher dispersions, the second part concentrates only on those features which are important in the mediumto low-resolution range.

Originally, it was intended to use greater enlargements on the L-plates (sequences of different luminosity classes for a given spectral type). Yet, general agreement upon inspection of the sample plates, which are not shown here, was that the smaller enlargements are better and thus they will be used in the final version of the atlas.

A detailed explanation of the different spectral features useful in classification from medium- to low-dispersion plates will be possible only after completion of all observational work. So far it is indicated, as was to be expected from the work of other authors, that some of the most useful luminosity criteria overlap seriously with population criteria, e.g. the CN bands.

The discussion at the symposium revealed an interest in the sampling of peculiar spectra. Following this suggestion work has began on preparing for a third part of the atlas which is planned to contain spectra of about 70 peculiar stars taken with all three above-mentioned dispersions.
The Peculiar Stars and Spectral Classification
Authors: Kharadze E. K. , Bartaya R. A.
Published: July 2016

The spectral classification experiments with the 70-cm meniscus telescope and 8° objective prism of Abastumani Observatory (dispersion 166 Å mm-1) have shown that if we apply the Kodak IIa-O plates at the 0.4 mm widening of spectra and the 20 minutes exposure time, we can successfully classify with relatively high accuracy in two dimensional MK system the stars down to the 11th magnitude, with simultaneous discrimination of peculiars.

We have undertaken such determinations first of all in Kapteyn Selected Areas aiming to fill the gaps in existing data for these standard areas.

Finally we could mention the high quality of the meniscus telescope optics together with good seeing in Abastumani as favourable factors making the Abastumani spectra of 10–11th magn. stars comparable with the slit spectra of the same dispersion.

The Abastumani spectra allow to apply the Morgan and Kitt-Peak criteria of MK classification only with a slight modification.

We have two-dimensionally classified in MK system about ten thousand stars down to the 11th magnitude in KA Nos. 2–43 (4.°5 × 4°5 each). Among them 137 peculiar stars have been revealed. They are mainly Ap, Am and BaII (7 stars) and the stars with composed spectra (5). 97 stars have been first identified as peculiars.
Spectrophotometry of M and C Stars
Authors: Nandy K. , Smriglio P.
Published: July 2016

Abstract and Summary

Surveys of M and C stars down to infrared magnitudes 12.m0 in two galactic regions in the direction Cygnus and anticentre are described. Infrared magnitudes are derived by a new method of calibration based on the use of a combination of crossed calcite plates and Polaroid HN32. Spectral classification is based on spectrophotometric criteria which measure the relative strengths of the molecular bands visible in the infrared in the low dispersion objective prism spectra. Infrared absolute magnitudes and interstellar extinction in the infrared are obtained from the present material and published data, and the space densities of M stars are determined.

Full accounts have been published in Publ. Edinburgh Roy. Obs.7, 1 (1970) and 7, 73 (1971).
The Spectral Classification of Southern Carbon Stars
Authors: Rybski P. M.
Published: July 2016

Well-widened objective prism spectra of carbon stars south of −25° declination have been examined to determine their suitability for classification. These spectra, taken by Henize in the early 1950's from South Africa as part of the Michigan-Mt. Wilson Hα survey of the southern sky, have a reciprocal dispersion at Na I 5890 Å of 300 Å mm−1 and are in good focus in the range between 5100 and 6600 Å.

Compared with spectra of northern carbon stars taken by the writer at the Lindheimer Astronomical Research Center with the one meter reflecting telescope and Cassegrain spectrograph at a grating reciprocal dispersion of 263 Å mm-1, and compared with spectra taken by Sanford of carbon stars overlapping the Henize sample, the objective prism spectra have been found of sufficient quality to support their classification into five groups following the scheme as proposed by Keenan and Morgan in 1941 and as refined by Gordon in 1967.

The first group exhibit weak C2 and CN features and Hα in absorption; the second, features attributable to a low C12/C13 ratio; the third, strong C2 and CN features and only moderately strong Na i in absorption; the fourth, very strong Na i in absorption; and the fifth, Hα in emission. Examples are given of each group, stars not fitting well into any of these groups are discussed, and the significance of each group is mentioned in light of work by Bouigue, Gordon, Peery, and Richer.
Blue-Infrared Narrow-Band Photometry from Objective Prism Spectra
Authors: Cassatella A. , Maffei P. , Viotti R.
Published: July 2016

A technique for narrow-band photometry in the 3600–8400 Å spectral region from objective prism spectra is briefly described and applied to the Hyades.
Preliminary Investigation of Quantitative Spectral Classification by Means of Objective-Prism Spectra Obtained with the Broerfelde Schmidt Telescope
Authors: Clausen J. V.
Published: July 2016

Different methods, used for measuring the strength of hydrogen lines in objective-prism spectra, are discussed and the parameters are compared with the photoelectric β-index. It is found that for A5V–G1V stars β can be given with a mean error of ±0.m020 (one spectrum).
Photometric Data in Machine-Readable Form
Authors: Hauck B.
Published: July 2016

For two years we have undertaken the collection of photoelectric data in view of their utilization by computer techniques. At present we are preparing a fine for each photometric system with the measurements published. As a second step, we shall form another file, alike for each system, with homogeneous measurements. This file will be obtained with weighed means of the published measurements. For that we need to compare each published list with a standard list before attributing the weights.

After that, we shall form a file indicating in which system a star is measured.

This work is undertaken in connection with the Data Center of Strasbourg and the group on spectroscopic and photometric data of the Commission 45.
Spectral and UBV Data for 583 Stars (Supergiants and Foreground Stars) in the Direction of the Large Magellanic Cloud
Authors: Ardeberg A. , Brunet J. P. , Maurice E. , Prévot L.
Published: July 2016

The stars observed are mainly from the Catalogue by Fehrenbach and Duflot. Some other stars – overexposed on the objective-prism plates, faint blue stars in H ii regions, stars with overlapping objective-prism spectra – have been added.

The photoelectric UBV photometry was done with the 1-m telescope at La Silla. The UBV filters have always been those recommended by Johnson. Normally 3 measurements or more on different nights have been made for each star. For a single observation of a program star the internal standard deviations are

The spectra have been taken with a Cassegrain spectrograph mounted on the 1.52-m telescope at La Silla. The dispersion is 73 Å mm−1, the spectral range 3250-5000 Å, and the limiting resolution 1.3 Å.

As a result of our observations, we present 409 stars as members of the LMC, 42 as possible members and 132 as galactic foreground stars (19 of these having high radial velocity). Remarkable features regarding velocities, spectra, magnitudes and colors are noted and commented.

All stars down to B = 11.5 have been observed spectrographically as well as photometrically. This is also the case for the majority of the high-velocity stars down to B = 12.0. For fainter objects the photometry is quite representative, whereas the spectroscopy is more scarce. The limiting magnitude is B = 14.0.

As radial velocities were used as membership criterion, our data do not suffer from any spectral type selection effects.

It was easy to apply the MK criteria to our dispersion using the Yerkes atlas and the Bidelman list of supergiants. A continuous series of supergiant standards in the LMC has been established from 06 to G2. Comparison with Radcliffe data and with recent results of Divan gives a dispersion in spectral type of less than one tenth of a spectral class. Also the luminosity classification shows good agreement.

In the classification several difficulties were met:

(1) The LMC stars are very luminous objects. In the Galaxy we do not have many corresponding stars. This is especially so for later spectral types.

(2) With the dispersion used, the differences between IaO and la are not very pronounced, especially not for F-G type stars.

(3) Many of the LMC supergiants are P Cygni stars. They show very sharp, often asymmetric line profiles with a sharp rise to the long wavelength side. This might cause erroneous classification, and also affect radial velocities.

(4) The presence of an extended atmosphere, causing dilution effects, can give spurious spectral classification.

We have found 8 A type high-velocity stars. The UBV results confirm their classification. 11 G-K type stars have been found to be high-velocity stars, among which are two subdwarfs earlier discussed by Fehrenbach and Thackeray. The number of late type high-velocity stars is quite high.

Full accounts have been given in Astron. Astrophys. Suppl.6 (1972), 249.
The Construction and Documentation of the Celescope Catalog
Authors: Haramundanis K.
Published: July 2016

In this paper, I describe briefly the instrument and the reduction system we have used for obtaining ultraviolet magnitudes and present some information concerning the sky areas and types of stars we have observed. I shall also comment on our use of catalogs in machine-accessible form and make suggestions concerning the most useful identifications to be assigned to observed objects, particularly those in the southern hemisphere.
Expanding Envelopes of Stars
Authors: Boyarchuk A. A.
Published: July 2016

Observations of Be stars are summarized and discussed, with a view to establishing dimensions of, and physical conditions within, their envelopes. Shell stars and Be stars are considered together, the observed differences between them being considered as due to the size of the envelope and the angle that the rotational axis makes with the line of sight. Rotational ejection of matter is insufficient to account for the formation of the envelopes. Theories of the structure of envelopes are also discussed. The envelopes of Wolf-Rayet stars are considered in a similar way. The interpretation of these is complicated by the known binary nature of many Wolf-Rayet stars. Other groups of stars possessing envelope-like structures – U Gem stars and old novae, symbiotic stars, and T Tauri stars – are briefly mentioned. The problems of stellar envelopes, first listed by Struve thirty years ago, are still unsolved.
Summary
Authors: Sahade Jorge
Published: July 2016

I have been assigned the task of presenting a summary of the Conference that has just finished. Actually during the Symposium the review papers have touched upon many items, some of them apparently not strictly connected with the subject of the meeting but helpful to clarify the picture related to close binaries and aimed at establishing differences with single stars, whenever possible. Therefore, my task would be somewhat difficult it if were not that all the review papers were extremely clear, very well given and fully discussed and that there were so many contributions from the floor presented without any pressure from time or otherwise. Furthermore most of what I would say has been already said. All this makes my task a lot easier as it appears clear that I should confine myself to offer only a few comments. Let me start by saying that Dr. Struve would have felt most pleased to have been present at this meeting and realize how many astronomers are now interested, strongly interested, in the field of close binaries and how much the field has and is expanding taking also up the efforts of researchers that work in the radio and X-ray regions and attracting the attention of those who are interested in problems of general relativity.
The Equation of State of Matter at Sub-Nuclear Density
Authors: Negele J. W.
Published: July 2016

An extremely simple form for the energy density of a nuclear many-body system is derived from the two-body nucleon-nucleon interaction. This theory, which yields excellent results for energies and density distributions of finite nuclei, is used to determine the ground state configuration of matter at sub-nuclear density. As the baryon density is increased, nuclei become progressively more neutron rich until neutrons eventually escape, yielding a Coulomb lattice of bound neutron and proton clusters surrounded by a dilute neutron gas. The clusters enlarge and the lattice constant decreases with increasing density, approaching a completely uniform state near nuclear density.
‘Statistical Bootstrap’ Equation of State for Cold Ultra-Dense Matter
Authors: Wheeler J. Craig
Published: July 2016

The statistical bootstrap theory of hadrons predicts a particle level density which increases with mass like ϱ(m) = cmaexp bm. The motivation for this level density is explored and then it is used to derive an equation of state for zero-temperature ultra-dense (> 1017 g cm−3) matter. The nature, uses, and limitations of the equation of state are discussed.
Quantum Crystals in Neutron Stars
Authors: Canuto V. , Chitre S. M.
Published: July 2016

Using the many-body techniques appropriate for quantum crystals it is shown that the deep interior of a neutron star is most likely an orderly arrangement of neutrons, protons and hyperons forming a solid. It is shown that a liquid or gas arrangement would produce higher energy. If so, a neutron star can be viewed as two solids (crust and core) permeated by a layer of ordinary or (perhaps) superfluid liquid. Astronomical evidence is in favor of such a structure: the sudden jumps in the periods of the Crab and Vela pulsars that differ by a factor of ∼ 102 can be easily explained by the star-quake model. If the Crab is less massive than Vela (i.e., if it is not dense enough to have a solid core), the star-quakes take place in the crust whereas for Vela they occur in the core.
Superluminal Sound and Ferromagnetic Transition in the Zeldovich Model
Authors: Kalman G. , Lai S. T.
Published: July 2016

The implications of the Zeldovich model (baryons interacting through a massive vector field) for the problem of superluminal sound propagation and ferromagnetic transition are examined. In a classical baryon gas at high densities correlation effects lead to the pressure increasing faster than the energy, ultimately resulting in superluminal sound; crystallization phase transition appears however at comparable densities, thus competing with the onset of superluminal sound. For a high density fermi gas the domains of ferromagnetic transition are delineated, indicating a minimal and maximal density below and above which no ferromagnetic transition can be expected. The latter is further affected by relativistic effects requiring a different approach to the calculation of exchange energy and of the ferromagnetic phase.
Cooling of Dense Stars
Authors: Tsuruta Sachiko
Published: July 2016

Cooling rates are first calculated for neutron stars of about 1 M⊙ and 10 km radius, with magnetic fields from zero to about 1014 G, for two extreme cases of maximum and no superfluidity. The results show that most pulsars are so cold that thermal ionization of surface atoms would be negligible. Next, nucleon superfluidity and crystallization of heavy nuclei are treated more quantitatively, and more realistic hadron star models are chosen. Cooling rates are thus calculated for a stable hyperon star near the maximum mass limit, a medium weight neutron star, and a light neutron star with neutron-rich heavy nuclei near the minimum mass limit. Results show that cooling rates are a sensitive function of density. The lightest star is cooler than others in earlier stages but the trend is reversed later. The medium weight star is generally the coldest of all in lower temperature regions where the effect of superfluidity becomes significant. However, if a heavy star contains pions, its cooling will be even faster. The Crab pulsar and Vela pulsar, expected to be the two youngest, can be as hot as (2 ∼ 4) x 106 K (on the surface), comparable with the results obtained from internal frictional heating by Greenstein, if they are medium weight to heavy hadron stars. However, older pulsars are cold. In fact, at about a few million years, the age of average radio pulsars, the surface temperature becomes only several hundred to several thousand degrees. Thus, the earlier conclusions about cold pulsars are still valid. Cooling of a massive white dwarf star is also shown.
Models for Compact X-Ray Sources
Authors: Salpeter E. E.
Published: July 2016

A statistical analysis of the UHURU catalogue of X-ray sources leads to the following conclusions. If the weak sources are omitted, there is a strong concentration to low galactic latitude but the absence of a strong background and the presence of some strong sources at low galactic longitude indicate an appreciable number of sources of luminosity L ∼ 104L⊙ in the vicinity of the ‘nuclear bulge’. This region generally suggests ‘stellar population II’ and therefore stars of small mass. However, there is some suggestion of a second class of sources, distributed in the galactic plane like ‘stellar population I’ and suggesting large stellar masses.

There are three possible types of simple X-ray spectra, (a) optically thin bremsstrahlung, (b) black-body spectrum, and (c) power-law spectra. In this talk only theoretical models for type (a) are reviewed, including accretion, rotation and vibration for a white dwarf star and cocoons around a neutron star.
Pulsars and X-Ray Sources
Authors: Pacini F.
Published: July 2016

We summarize some theoretical aspects of the X-ray emission from genuine pulsars and their relation to the more general problems of X-ray sources.
Extragalactic X-Ray Sources
Authors: Burbidge G. R.
Published: July 2016

A review is given of the physical properties of extragalactic X-ray sources. The generation of X-rays as thermal bremsstrahlung, by the synchrotron mechanism or by Compton Scattering, is discussed. It is shown that each may be important depending on the circumstances. Only more detailed observations will enable us to decide which process dominates in any given source.
Extragalactic X-Ray Sources and Their Contribution to the Diffuse Background: Invited Paper
Authors: Setti G. , Woltjer L.
Published: July 2016

We present estimates of the integrated contribution of extragalactic sources to the diffuse X-ray background in the 2–10 keV energy interval. It appears that classes of objects already detected as X-ray sources easily account for at least 10% of the background. Quasistellar objects, and possibly Seyfert and radio galaxies might contribute a larger fraction of the background intensity.

We also suggest that several of the unidentified X-ray sources in the UHURU catalogue at high galactic latitudes may be bright QSO's as yet unknown. The detection of a larger number of QSO's in the X-ray band may allow a decisive test for the cosmological interpretation of the redshifts of QSO's.
The Soft X-Ray Background
Authors: Friedman H. , Fritz G. , Shulman S. D. , Henry R. C.
Published: July 2016

A survey of soft X-ray background observations in the 0.1–10 keV range is presented. In the region above 1 keV, recent results on point X-ray sources are discussed and their integrated contribution to the diffuse background is estimated. However, the average luminosity of various classes of extragalactic X-ray sources is still not sufficiently well known to permit this estimate to be made with any certainty. A discussion is given of recent observations at energies below 1 keV where the effects of interstellar absorption are important. It is argued that although some fraction of the background radiation in the 0.1–1 keV range must be galactic in origin, there is still substantial evidence for an extragalactic component. Proposed theories for generating both the galactic and extragalactic X-ray background are briefly reviewed.
‘Local’ Theories of the X-Ray Background
Authors: Felten James E.
Published: July 2016

Recent theories of the origins of diffuse-background X-rays are reviewed, with emphasis on theories of the soft flux in the galactic plane and at the poles. This is probably partly galactic and partly extragalactic in origin. Failure to observe absorption by the Small Magellanic Cloud and by galactic gas in neighboring directions may be due to sources in the Cloud and to statistical fluctuations in galactic emission and absorption. Several models for numerous low-luminosity sources in the Galaxy are available. True ‘diffuse’ emission seems unnecessary. Absorption by Galactic gas seems to agree roughly with theory. The soft extragalactic component may arise in a hot intergalactic medium.

The existence of a ‘diffuse’ galactic-plane excess in 1–100 keV is in some doubt. Low-luminosity sources may contribute to this as well.

For isotropic X-rays in 1 keV – 1 MeV, superposition theories involving clusters of galaxies, Seyfert galaxies, etc. over a cosmological path length are now roughly viable. Simple ‘metagalactic’ Compton theories seem excluded if the break at 40 keV is sharp, but this is now in doubt. A very hot intergalactic medium at T ≈ 3 × 108 K would give the possibility of a sharp break.

A recent upper limit on the line source strength of 100-MeV photons in the galactic plane may create some difficulties for cosmic-ray theory. The spectral shape of π-γ photons has become a matter of theoretical dispute.
Diffuse Background of Energetic X-Rays
Authors: Pal Yash
Published: July 2016

The experimental situation in regard to the extra-galactic diffuse background of photons of energy above 30 keV is critically reviewed in the light of discussions at this Symposium.

There seems to be some doubt about the spectral break at 40 keV. There is an indication of a small bump around 2 MeV and of a shoulder around 20 MeV. The spectrum below 1 MeV (down to 30 keV) can perhaps be represented as 25 (E/1 keV)–2.1. This spectrum also gives, roughly, the OSO III upper limit at 100 MeV, though it lies well below the two bumps mentioned above. A good deal of the discussion centres on the problem of backgrounds in different types of experiments to measure the diffuse X- andγ-ray fluxes.
Angular size of OH emission regions
Authors: Burke B. F. , Crowther P. P. , Moran J. M. , Rogers A. E. E. , Ball J. A. , Hyde G. M. , Meeks M. L.
Published: July 2016

Interferometry gives effective diameters less than 20″ for the OH emission sources in W3and Sgr B2. The sources in W49and NGC 6334 contain two or more components, some of which are smaller than 25″.
A possible supernova remnant observed in 21-cm emission
Authors: Shane W. W. , Katgert P.
Published: July 2016

In the course of one of the investigations listed in Paper 29, we have studied a disturbance in the observed neutral-hydrogen distribution in the galactic plane. The figures derived for this feature show excellent agreement with those quoted by Kahn and Woltjer (Paper 16) as the expected result of a supernova explosion.
Distribution and systematic motions of neutral hydrogen
Authors: Lindblad P. O.
Published: July 2016

Recent work on the rotation curve of the Galaxy has confirmed the large-scale asymmetry of the motion of neutral hydrogen. In addition it seems that the radial velocities at the subcentral points of the lines of sight vary with longitude in a rather unsmooth manner. These irregularities of the motions may be associated with the distribution of matter in spiral arms. Large-scale systematic deviations from circular motion, ranging up to at least 30 km/sec in the outer regions of the Galaxy, are shown by observations across the anti-centre.

Thus it presumably is impossible to describe the velocity field of the gas in terms of a simple general model, or to derive the force field without simultaneously solving the distribution problem. We may have to construct for each region, or for each separate feature of galactic structure, a special model that explains its radial-velocity properties. All these models must of course be in mutual agreement.

The most coherent picture of the large-scale motion of the interstellar hydrogen is still given by the early Dutch and Australian surveys. A number of surveys with higher resolution are at present well on their way, although most of them are limited to a rather narrow strip along the galactic equator.

In the interpretation of line profiles some method of analysis into Gaussian components is increasingly used, especially as an aid in following different structural features in diagrams giving velocity as a function of galactic longitude or latitude, and in separating these features in regions of velocity overlap. Applications of this technique and of simple model-making are demonstrated in connection with a discussion of the local and outer structure of the Galaxy.

Large-scale deviations from the galactic plane as found in recent work indicate that the ‘bending’ of the plane may be a complicated phenomenon. New observations outlining the true character of this bending are necessary for a decision between the different theories about these deviations.

The need for surveys with high frequency resolution and extending away from the galactic plane is emphasized. Optical identifications of members of the various structural features are highly desirable as an independent determination of parameters of structural models.
Progress report on 21-cm observations at low latitude between longitudes (l 11) 0° and 66°
Authors: Shane W. W.
Published: July 2016

In the course of several 21-cm observing programmes being carried out by the Leiden Observatory with the 25-meter telescope at Dwingeloo, a fairly complete, though inhomogeneous, survey of the regionl11= 0° to 66° at low galactic latitudes is becoming available. The essential data on this survey are presented in Table 1. Oort (1967) has given a preliminary report on the first and third investigations. The third is discussed briefly by Kerr in his introductory lecture on the galactic centre region (Paper 42). Burton (1966) has published provisional results of the fifth investigation, and I have discussed the sixth in Paper 19. All of the observations listed in the table have been completed, but we plan to extend investigation 3 to a much finer grid of positions.
The hydrogen distribution in galaxies
Authors: Roberts Morton S.
Published: July 2016

Results of 21-cm line observations with the 300-foot telescope are summarized. Along the major axis of M 31, the peaks in the distribution of neutral hydrogen correlate closely (but do not exactly coincide) with the optical spiral arms. The distribution of hydrogen over the galaxy shows a ring pattern; the same is true in M 33.

Resolution of such ring structures may be facilitated by consideration of profile integrals over a restricted velocity range around the systemic velocity. Out of nine spiral systems studied, with minor axis > 10′ (arc), only NGC 628 exhibits no ring. The ratios ring radius to ring width and optical radius to ring radius vary little about averages 2·5 and 1·7. In two irregular galaxies, no ring structure was observed.

Neutral-hydrogen haloes, if present, can only be studied in large edge-on systems. In NGC 4244 and 7640, the upper limit to the density of neutral hydrogen in the halo is 0·001 cm-3. Qualitative considerations indicate that a similar value may apply in the Galaxy.
Interferometric studies of H 11 regions
Authors: Courtés G.
Published: July 2016

The paper briefly summarizes the application of interference techniques to studies of structure and kinematics both of our Galaxy and of the nearest external galaxies.

Since the principal results of our work have been published elsewhere (Courtès 1960, Courtèset al.1966), we shall restrict ourselves here to a brief summary of the most important points, especially those related to radio-astronomical investigations.
Maser effects in the interstellar hydrogen clouds of the galactic halo
Authors: Šklovskij I. S.
Published: July 2016

It is suggested that the neutral hydrogen atoms in clouds with high negative velocities observed at high galactic latitudes may, when moving towards a galactic H 11 region, be excited by radiation in the red wing of the Lyman-α profile. The steepness of this wing may cause a population inversion of the hyperfine-structure levels. Consequently, estimates of the hydrogen density in the high-velocity clouds, and of the flow of matter towards the galactic plane (or into the Galaxy), when based on the assumption of collisional excitation, may be too high by two orders of magnitude.
The Zeeman effect in interstellar clouds
Authors: Verschuur G. L.
Published: July 2016

The interpretation of Zeeman-effect measurements in terms of interstellar magnetic fields is strongly involved with the problems of the nature of interstellar clouds, and of their relationship to the structure of the field. The best measurements furnish, for the mean longitudinal component of the spectrum of Tau A, a value of + 1·1 ± 3·0 μG (micro-gauss), and for that in the Orion-Arm feature in Cas A, - 0·8 ± 3·5 μG. These values are consistent with an upper limit of 7 μG to a uniform magnetic field, pervading the absorbing clouds and directed parallel to the local spiral arm.
Sagittarius A
Authors: Lequeux J.
Published: July 2016

The available high-resolution observations of the complex of radio sources in the region of the galactic centre are reviewed and analysed. As noted by Downes and Maxwell, the spectrum of the strong central source, Sagittarius A, is markedly non-thermal (index 0·7) at high frequencies; below 3000 MHz the spectrum may be flat, but flux values obtained at high angular resolution are badly needed.

Various arguments indicate that the whole source complex is located near the nucleus of the Galaxy. From the short-wave observations collected by Downes and Maxwell dimensions, densities and masses are estimated for the thermal sources. The total mass of ionized hydrogen in these sources is about 106M⊙; the mechanism of ionization is uncertain.

The non-thermal source Sgr A may be similar to the optical nuclei of external galaxies. Its synchrotron emission, as well as the outward motions and tilted features observed in the 21-cm line and continuum, are signs of activity in the galactic nucleus; but the time-scales of the various phenomena appear to disagree.
On the possible gamma-ray source in Cygnus
Authors: Duthie J. G. , Savedoff M. P. , Cobb R.
Published: July 2016

A source of gamma rays has been found at right ascension 20h15m, declination +35°, with an uncertainty of 6° in each coordinate. Its flux is (1·5 ± 0·8) x 10-4photons cm-2sec-1at 100 MeV. Possible identifications are reviewed, but no conclusion is reached. The mechanism producing the radiation is also uncertain.
Spectrophotométrie intégrée des galaxies proches dans L'ultraviolet (expérience persée)
Authors: Cruvellier P. , Roussin A. , Valerio Y.
Published: July 2016

Preliminary results obtained from a sounding rocket launched in December 1968 show a strong ultraviolet excess in the central part of the Andromeda nebula, as compared to the color of the sky background.

The color index of M 31 in this spectral range may be explained by an abnormally high proportion of B stars.
Photoelectric rocket spectra at 10 Å resolution
Authors: Stecher Theodore P.
Published: July 2016

Spectral scans of a number of early-type stars have been made with a three-channel spectrophotometer attached to a 32 cm telescope. The telescope was pointed at the individual program stars with an accuracy of at least 20 sec of arc. The spectral resolution was 10 Å over the range 1150 Å to 4000 Å. The data were recorded in digital form and processed in a computer.

The profile of hydrogen Ly-α, as smeared by the exit slit, was obtained for α Lyr, α CMA, β Ori, and β Tau. For the earlier-type stars observed the Ly-α line of the star is masked by interstellar hydrogen absorption. For ζ Oph and ζ Per the Ly-α absorption is considerably larger than for the other early-type stars. The identification of lines is relatively simple for the light elements but becomes more difficult with the heavier ions since there are many more weaker lines and 10 Å is then insufficient resolution. Extreme P Cygni profiles are present in the earliest stars and are interpreted as mass loss at high velocity.

A full description appears in Astrophys. J.159, Feb. 1970.
UV spectrophotometry of Canopus from Gemini XI
Authors: Kondo Y. , Henize K. G. , Kotila C. L.
Published: July 2016

The UV energy curve of Canopus in the 2400–4000 Å wavelength range has been obtained from spectrograms having a dispersion of 183 Å mm−1. This curve is in good agreement with previous observations and with a model atmosphere. The equivalent width of Mg11 2795 Å, 2802 Å is found to be 22 Å.
Review of ground-based observations of spectra relevant to the ultraviolet
Authors: Feast M. W.
Published: July 2016

Up to the present the chief results of investigations of stellar line spectra in the extreme ultraviolet have been limited to two fairly distinct fields. In the case of the Sun the data have referred mainly to the chromosphere and also to the region of the temperature minimum at the top of the photosphere and to the corona. We may hope that observations will eventually be extended to the chromospheric ultraviolet spectra of other stars. In the case of the early type stars the most spectacular results so far obtained have concerned the evidence for mass loss by several of these stars. I have therefore chosen to spend most of the available time discussing some of the ways of studying from the ground, first the chromospheres of stars other than the Sun and secondly mass loss from stars.
A high-resolution solar spectrum 2000 Å–2200 Å
Authors: Jones B. B. , Boland B. C. , Wilson R. , Engstrom S. T. F.
Published: July 2016

A high-resolution solar spectrum in the range 2000–2200 Å was obtained in a recent flight of a sunpointing Skylark rocket. This was launched at 04.21 hr UT on April 22, 1969 from Woomera and reached an apogee of 178 km. An optical alignment system operating on the main vehicle pointing system gave a net stabilisation of ±3 arc sec in the position of the solar image relative to the spectrograph slit. The slit, of length 1.0 mm, was set in the north-east quadrant parallel to and 5 arc min from the north/south axis, its lower edge being 1 arc min from the equator. The roll control of ±2.5° was provided entirely by the standard Elliott Bros. type of vehicle stabilisation.
Fabry-Pérot interferograms of the solar Mgii resonance lines
Authors: Bates B. , Bradley D. J. , McKeith C. D. , McKeith N. E. , Burton W. M. , Paxton H. J. B. , Shenton D. B. , Wilson R.
Published: July 2016

The resonance lines of Mgii occur at wavelengths (2802.7 Å, 2795.5 Å) just beyond the extinction limit of the Earth's atmosphere. At such wavelengths sophisticated optical techniques can now be employed and this fact, together with the high cosmic abundance of magnesium, makes these lines particularly important for study in UV Astronomy. In the case of the Sun, the lines consist of a broad absorption with a pronounced emission core.
Observations of interstellar Lyman-α with the Orbiting Astronomical Observatory
Authors: Savage B. D. , Code A. D.
Published: July 2016

The equivalent width of the blended line at Lyman α is given for 48 stars measured with the OAO-A2 scanning spectrometer. This provides an upper limit to the neutral hydrogen column density. In the Orion association these upper limits are significantly lower than the column densities determined from 21-cm emission line measurements. The determination of the Lyman α equivalent width for θ Ori by Carruthers is rediscussed and agreement between 21-cm absorption measures and Lyman α absorption is obtained for a spin temperature in the range of 40–70 K. It is suggested that the most likely explanation for the discrepancies found for the other Orion stars is that the 21-cm emission primarily occurs beyond the Belt stars.

The correlation between the OAO blended equivalent widths and color excess, 4430 Å absorption, and interstellar sodium absorption are examined. Excellent correlation between sodium and hydrogen column densities is found.
High spectral resolution interferometric planetary observations in the 7–25 μ region
Authors: Hanel R. A. , Kunde V. G. , Meilleur T. , Stambach G.
Published: July 2016

The thermal emission spectra of Venus, Mars, Jupiter, and the moon were observed at the coude focus of the McDonald Observatory 107-inch telescope in the 400–1400 cm−1 spectral range with spectral resolutions of 0.3–0.7 cm−1. A preliminary interpretation of the Venus/lunar ratio spectrum allows identification of four upper state CO2 bands in the Venusian atmosphere at 791, 828, 865, and 961 cm−1 and confirms previous observations of the broad absorption-like depression around 890 cm−1. The rotational structure of the 791 and 961 cm−1 bands is well developed at this spectral resolution.
Venus cloud contrasts
Authors: Coffeen David L.
Published: July 2016

Contrast of the Venus cloud patterns is measured by photoelectric scans using a sequence of narrow-band interference filters. The contrast appears constant in the range 3100–3600 Å, drops to the limit of detectability at about 4100 Å, and is absent at longer wavelengths.
Colorimetry of Martian features by means of area scanning
Authors: Boyce Peter B.
Published: July 2016

The contrast between light and dark areas on Mars has been the subject of two photoelectric studies by Younkin (1966) and McCord (1969), both of which were somewhat limited in scope. Younkin's data are based on one night's observations. McCord had a more suitable instrument for making a comparison between two areas on Mars, but still used only six nights. The agreement between these two studies is excellent. However, there is ample evidence from photographs that there are short-term changes in the contrast and brightness of Martian surface features, especially in the case of blue clearing. Visual observations are unsuitable for investigating these changes, due to the limited wavelength range of the eye's sensitivity, as well as the poor accuracy of the eye as a photometric instrument. Even photography is of limited usefulness when high accuracy is desired. Consequently, a program of continuous photoelectric observation of Mars was set up for the 1969 opposition. The technique of area scanning was chosen as the best method of recording the contrast of Martian surface features.
The contribution of atmospheric aerosols to the Martian opposition effect
Authors: Mead Jaylee M.
Published: July 2016

Mie scattering calculations have been made for atmospheric aerosols having various indices of refraction to determine their possible contribution to a Martian opposition effect, such as that reported by O'Leary in 1967. Neither substances with a real index between 1.20 and 1.50, such as ice, water, or solid CO2, nor highly absorbing materials, such as limonite, can produce the observed effect. Submicron-sized spherical particles with refractive indices of 1.55 to 2.00 do, on the other hand, exhibit a marked increase in reflectivity at small phase angles and might be responsible for the enhanced brightness at the shorter wavelengths.
Some problems of anisotropic scattering in planetary atmospheres
Authors: van de Hulst H. C.
Published: July 2016

The similarity rules to compare atmospheres with anisotropic and isotropic scattering are reviewed. Omission of a narrow diffraction peak in the scattering pattern is permitted and corresponds to a special application of the similarity rules. It is shown that the extrapolation length for conservative scattering can be found with great precision from a formula involving only ω2 and ω3. An asymptotic expression for high-order scattering in a semi-infinite atmosphere is given and it is shown by some examples that this expression can be used to find by interpolation the terms of any order. Finally, the way in which the contrast between a dark and bright area near the center of the disk of Mars is affected by an overlying haze is computed for isotropic and for anisotropic scattering.
Spectroscopic determination of surface pressure and elevation differences on Mars
Authors: Cruikshank D. P.
Published: July 2016

Observations of a carbon dioxide band at 1.2206 μ (8192.6 cm−1) made at the opposition of Mars in June, 1969, are used with laboratory data to derive a value for the pressure at the surface of Mars. This band is especially suitable because it is sensitive to pressure, lying in the transition region of the curve of growth, but is relatively free of telluric contamination. The pressure derived is , corresponding to the Martian desert region Amazonis.

Using a five-channel spectrometer, the strengths of two carbon dioxide bands at 1.5753 and 1.6057 μ (6347.8 and 6227.9 cm−1) were compared over a Martian dark area (Mare Acidalium) and a nearby bright area in Amazonis. The bands were 1.32 times stronger in the dark area than in the bright area. Interpreting this as evidence for elevation differences on the Martian surface, it is found that the dark Mare Acidalium is 2.5 km lower in elevation than the bright area with which it was compared.
Mariner 6: Ultraviolet spectrum of Mars upper atmosphere
Authors: Barth C. A. , Fastie W. G. , Hord C. W. , Pearce J. B. , Kelly K. K. , Stewart A. I. , Thomas G. E. , Anderson G. P. , Raper O. F.
Published: July 2016

Emission features from ionized carbon dioxide and carbon monoxide were measured in the 1900- to 4300-Å spectral region. The Lyman-α 1216-Å line of atomic hydrogen and the 1304-, 1356-, and 2972-Å lines of atomic oxygen were observed.