bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physical Data of the Fundamental Stars
Authors: Dingjiang Luo , Baocai Zhang 
Published: July 2016

The precise positions and proper motions (J2000.0) of 1535 Basic FK5 stars in the FK5 system have been used in the reduction of the local vertical monitoring and the catalog observations at Beijing Astronomical Observatory. In addition, similar data for 1987 FK4 Sup stars, in which 980 stars indicated by “F” will be included in the FK5, were made available recently by Heidelberg via Prof. Tong Fu, director of Purple Mountain Observatory. The positions and proper motions of the other 1007 FK4 Sup stars in the FK5 system are provided by the Astronomisches Rechen-Institut with relatively low accuracies. However, the physical data, such as the visual magnitudes and the spectral types of these rs with rather large uncertainties have their origin in the Henry Draper Catalogue since the compilation of the FK4 and the FK4 Sup. More accurate visual magnitudes available in the well-defined photoelectric system and the spectrum types in the MK-system may be found, for example in the Bright Star Catalogue and its supplement.For the convenience of users of astrometric observations and for geodetic purposes, visual magnitudes (V), color indices (V-B), spectral types (Sp), tritonometric parallaxes (p in mas), and radial velocities (RV in km/sec) for the 1535 FK4 stars and 1987 FK4 Sup stars are available.These data are available from the authors in machine-readable form which includes the mean positions and proper motions of J2000.0 in the FK5 system and the cross-references to the GC of FK4 stars and FK4 Sup stars. Printed or magnetic versions of the data may be requested from the authors.
The Plasma Universe
Authors: Fälthammar Carl-Gunne 
Published: July 2016

The term “Plasma Universe”, coined by Hannes Alfvén, emphasizes the fact that plasma phenomena discovered in the laboratory and in accessible regions of space, must be important also in the rest of the universe, which consists almost entirely of matter in the plasma state.Relevant aspects of this concept will be discussed. They include the response of the plasma to electric currents, the support of magnetic-field aligned electric fields, violation of the frozen-field condition, rapid release of magnetically stored energy, acceleration of charged particles, chemical separation, filamentary and cellular structures, and critical velocity interaction.
Creep in the Earth and Planets (Invited Lecture)
Authors: Jeffreys Harold 
Published: July 2016

An outstanding problem is to reconcile the Moon's rotation with the persistence of its non-hydrostatic dynamical ellipticities. The first requires imperfection of elasticity under strains of order 10−7; the second apparently little under larger ones.Lomnitz gave experimental evidence that creep is linear at elastic shears from 10−5to 10−4, indicating that a linear rule could be right at still smaller values. Positive evidence for the Earth comes from the damping of the 14-monthly nutation, which has a relaxation time of the order of 30 yr. Most work on imperfect elasticity has assumed that under constant shear stress the strain increases with time either liket(elasticoviscosity) or like logt.If the result from the 14-monthly nutation, with elasticoviscosity, is applied to the Moon, the dynamical ellipticities would have subsided considerably in the last 200 yr. With the logarithmic rule anSpulse at 80° would have its beginning spread out over about 70 s and be unreadable. These contradictions are avoided if the increase under constant stress is about liket0.2. The resulting law involves two constants. Without change of these, applications are made to other phenomena. The rotations of the Moon and of other satellites whose rotations are known are explained; so is the persistence of the Moon's dynamical ellipticities; also the failure to detect three free oscillations that might theoretically exist. Elasticoviscosity would imply rapid disappearance of the non-hydrostatic second and third harmonics in the Earth's gravitational field; this is avoided with the new law. Study of damping of free vibrations of the Earth (including surface waves) has usually assumed the logarithmic law, but it appears that the new law fits the data at least as well, and that it may also explain those that have been interpreted in favour of layers of low velocity. It appears that the damping at depths up to 400 km or so is much more severe than the average for the Earth's shell, and more evidence for shorter periods is much needed.Any law with an index less than 1 would forbid thermal instability (convection) and continental drift.
On the Regularity of Fluctuations in Annual and Secular Polar Motions
Authors: Abraham H. J. 
Published: July 2016

It may become possible to explain much of the behaviour and remarkable regularity of fluctuations in reported annual and secular polar motions if the potential that causes an immediate excitation is also a factor in that excitation's rate of change afterwards.The Chandler frequency, for example, being a function of the deformation excitation, should then vary with the librational and nutational displacements of the pole of rotation. It is found that the frequency does in fact do so.The annual excitation would be affected as well. The steady and seasonal primary excitations are known to cause free and forced nutations that are accompanied by periodic secondary excitations. These would arise partly at once and partly in the course of time; they would modulate the primary annual excitation and also one another, according to the period of the beats between the annual and Chandler nutations. It is found that the reported annual excitation shows phase and amplitude fluctuations of this kind. (The data also show another large excitation that occurred briefly on two occasions).Finally, the amplitude and phase of the secular librations appear to have followed an expression that is obtained by integrating the rates of change of excitation. This expression is a function of the amplitude of the annual excitation and the period of the beats between the annual and Chandler nutations.
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 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 SummaryWhen 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 SummarySurveys 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.
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.
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.
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.
‘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.