bluuebunny/crossref_metadata_2025 huggingface dataset:
Preliminary Study of the Stellar Populations and Density Profile of NGC 6624 Using HST
Authors: Guhathakurta Puragra , Yanny Brian , Bahcall John N. , Schneider Donald P.
Published: July 2016

We present preliminary results from an ongoing study of the central 5 arcmin2 of NGC 6624 based on short F336W, F439W, and F555W (UBV) Hubble Space Telescope WFPC2 exposures (Yanny et al. 1996). NGC 6624 is a dense, metal rich, post core collapse globular cluster at a distance of 8.1 kpc. Nearly 5000 stars with V ≳ 21 (1.5 mag below the turnoff) are detected within the 34′′ × 34′′ area of the PC1 CCD which imaged the cluster center. Individual stars brighter than V = 20 are easily identifiable in the central image section shown in Fig. 1. Image simulations and similar data on the denser cluster M15 indicate that the effects of incompleteness and photometric error are negligible on the V < 19.5 sample of stars in NGC 6624. The stellar surface density profile derived from such a sample is well approximated by a power law of index α = −0.85 (Fig. 2). The density profile shows no hint of flattening towards smaller radii in the radial range over which it is reliably measured (r ≳ 0′′.3). A B vs. U – V color-magnitude diagram of the r < 15′′ region (Fig. 3) shows a well defined blue straggler sequence. Our preliminary findings are consistent with an earlier study of this cluster by Sosin and King (1995) using pre-repair FOC images.
HST/FOS Discovery of Probable CVS in NGC 6397
Authors: Grindlay Jonathan E. , Cool Adrienne M.
Published: July 2016

Our recent HST/FOS spectra (Grindlay et al 1995; GC95) have spectro-scopically identified the 3 central Hα candidates (Cool et al 1995; CG95) as the probable cataclysmic variable (CV) counterparts of the the three central dim x-ray sources (Cool et al 1993; CG93) in the nearby core collapsed globular NGC 6397. Here we present the x-ray vs. optical properties of these three objects, derived from the FOS spectra presented in GC95 and the x-ray data of CG93, which strengthen the case that they are CVs and not quiescent LMXBs. Additional data and discussion are presented in the accompanying paper by Grindlay (these proceedings).
Environmental Influence on Stellar Evolution: The Horizontal Branch of NGC 1851
Authors: Saviane I. , Piotto G. , Capaccioli M. , Fagotto F.
Published: July 2016

The bimodal nature of the horizontal branch (HB) of NGC 1851 is known since Stetson (1981). In order to better understand the properties of its HB, we collected a set of data at the ESO-NTT telescope, which provides a full coverage of the cluster area. Additional archive images from the HST-WFPC camera have been used in order to study the central region. The resulting c-m diagram (CMD) for 20500 stars is presented in Fig. 1 (left). Despite its metallicity ([Fe/H]=−1.3), NGC 1851 presents a well defined blue HB tail, besides the expected red clump. The observed CMD has been compared with the synthetic ones. The bimodal HB can be reproduced assuming that there are two stellar populations in the cluster, with an age difference of ∼ 4 Gyr, hypothesis not supported by other properties of the CMD. On the other side, if we assume that the stars in NGC 1851 are 15 Gyr old (as suggested by the difference between the HB and the TO luminosities), only a bimodal mass loss can reproduce the HB morphology: only stars with higher than standard mass loss rate are able to populate the blue-HB (BHB) tail (Fig. 1,left). There are no observational evidences for a bimodal distribution of other parameters (He, CNO, etc.).
Spatial Structure of the Globular Cluster System around NGC 4472
Authors: Kim Eunhyeuk , Lee Myung Gyoon , Geisler Doug
Published: July 2016

NGC 4472 (M49) is a giant elliptical galaxy in the Virgo cluster, and has a rich GCS. Radial surface density profiles of the GCS in this galaxy are well-known (Cohen 1988, Harris 1986). However, little information is available for the ellipticity (e) and position angles of the GCS in NGC 4472. In this study we have investigated in detail the spatial structures of the GCS in NGC 4472 (the surface density, the ellipticity, the color, and the position angle) in comparison with those of the halo, using a large sample of the globular clusters located in a wide field (16′ × 16′) of NGC 4472.
Evolution of the Galactic Globular Cluster System
Authors: Vesperini E.
Published: July 2016

Recent surveys of the observational properties of galactic globular clusters have shown the existence of interesting correlations and trends between structural parameters and between structural parameters and location inside the Galaxy (Chernoff & Djorgovski 1989, Djorgovski & Meylan 1994). The origin of most of these correlations is not clear yet and it is not clear to what extent they reflect the primordial conditions or the result of evolution. We have carried out a set of simulations following the evolution of the properties of a globular cluster system (mass function, spatial distribution, correlations between structural parameters) starting from given initial conditions. The evolution of each individual cluster has been followed by the same method applied by Chernoff et al. (1986) and Chernoff & Shapiro (1987). The effects of internal relaxation, disk shocking and dynamical friction have been considered. The main goal of the analysis is that of establishing the role of initial conditions and evolutionary processes in determining the present observational properties.
What Theorists Think They Know about AGB Stars
Authors: Lattanzio John C.
Published: July 2016

In this paper I discuss our basic picture of the structure of AGB stars, and how their earlier evolution led them to this situation.
Understanding the Elusive Dwarf Carbon Star
Authors: Green Paul J.
Published: July 2016

Most stars in our Galaxy with photospheric C/O > 1 (carbon stars) are not giants but dwarfs. The newly-recognized class of dwarf carbon stars joins the growing family of stars with peculiar abundances that are now recognized as products of mass-transfer binary (MTB) evolution. The dozen examples now known span a wide range of evolutionary histories, ages, and abundances. These stars can already provide some much-needed constraints on the formation of AGB C stars in the disk and spheroid populations, and on the parameters characterizing binary evolution there. A larger sample, with some bright members, would hasten our progress.
Spectral Classification of Carbon-Peculiar G Stars
Authors: Koktay Tuba , Garrison R. F.
Published: July 2016

Spectroscopic observations at classification dispersion have been obtained for a set of stars having abnormal photometric indices on the Strömgren uvby system. Five of the stars observed have extreme carbon anomalies; two of these spectra are illustrated here.
Post-AGB Variables and Stellar Mass-Loss
Authors: Feast M. W.
Published: July 2016

A brief review is given of the various types of star which are thought to be in the immediate post-AGB stage of evolution. The paper then concentrates on the properties of the RCB stars and particularly on the mass-loss process in these stars. It is suggested that grain formation takes place over the cool regions of giant convection cells in a super-Eddington outflow and in the form of small clouds or puffs. Attention is drawn to observations which suggest that grain formation in the outer atmospheres of Miras and other cool giants may also take place in puffs rather than in spherical shells. Evidence on the long-term variation of the circumstellar dust emission from RCB stars is summarized.
Collimated Outflow from Stars: The Planetary Nebula Abell 78
Authors: Pişmiş Paris
Published: July 2016

The planetary nebula Abell 78 is slightly oval in an Hα image taken with a focal reducer attached to the 2.1-m telescope of San Pedro Mártir Observatory. Jacoby (1979) noted that the morphology of this PN in the [O III] λ5007 line is quite different from that shown on the POSS red plates.
Barium Stars and Tc-Poor S Stars: Binary Masqueraders within the Carbon-Star Family
Authors: Jorissen A. , Van Eck S.
Published: July 2016

Our current understanding of the origin of barium and S stars is briefly reviewed, based on new orbital elements and binary frequencies.
Light and Velocity Variability of Post-AGB Stars
Authors: Hrivnak Bruce J. , Lu Wenxian
Published: July 2016

We have monitored velocity variability in nine proto-planetary nebulae (PPN) over a 5 year interval and have monitored light variability in 40 PPN over a 2 year interval. We find all nine of the objects to vary in velocity and almost all of the 40 to vary in light. Three of the objects display a clear periodicity in their velocity variations, and in all three the light varies with the same period as the velocity. Periodic light variations are found in six other objects. We interpret these as due to pulsation in the PPN.
Carbon Star Dust from Meteorites
Authors: Jørgensen Uffe Gråe , Andersen Anja C.
Published: July 2016

Inside carbonaceous chondrite meteorites are tiny dust particles which, when heated, release noble gases with an isotopic composition different from what is found anywhere else in the solar system. For this reason it is believed that these grains are (inter)stellar dust which survived the collapse of the interstellar cloud that became the solar system. We will describe here why we believe that the most abundant of these grains, micro-diamonds, were formed in the atmospheres of carbon stars, and explain how this theory can be tested observationally.
Fluorine Production in Asymptotic Giant Branch Stars
Authors: Mowlavi N. , Jorissen A. , Arnould M.
Published: July 2016

The present status of our understanding of fluorine production in asymptotic giant branch stars is reviewed, and future perspectives are presented.
From the Tip of the AGB Towards a Planetary: A Hydrodynamical Simulation
Authors: Schönberner D. , Steffen M. , Stahlberg J. , Kifonidis K. , Blöcker T.
Published: July 2016

We present a first exploratory investigation of the dynamical evolution of a dusty stellar wind envelope along the upper AGB and its transformation into a planetary nebula. We find the existence of AGB stars with detached shells to be a natural consequence of the mass-loss variations during a thermal pulse. It is also demonstrated that due to the large dynamical effects caused by the ionizing radiation field and the fast wind of the central star, it is impossible to deduce the AGB mass loss history from the planetary's density and velocity distribution. The structure of the halo, however, is still determined by the AGB mass loss history. The rapid decline of mass loss expected in the aftermath of thermal pulses leads to extended shells of low densities and explains halos with sharp boundaries.
Variability Studies with International Networks
Authors: Querci François R. , Querci Monique
Published: July 2016

Variable stars can be monitored through observing campaigns which coordinate multi-site telescopes at various longitudes. A new practice is now being developed, involving devoted networks of robotic telescopes. We will review these two technologies and will emphasize the NORT (Network of Oriental Robotic Telescopes) project, which we are promoting in Middle Eastern countries.
General survey of X-ray sources: (Invited discourse)
Authors: Friedman H.
Published: July 2016

Prof. Friedman did not communicate any text or Summary of his invited discourse.
Techniques for improving the sensitivity of proportional counters used in X-ray astronomy
Authors: Sanford P. W. , Cruise A. M. , Culhane J. L.
Published: July 2016

The discovery and measurement of cosmic X-ray sources has almost invariably been performed with proportional counters which have large window areas. In the energy range from 1 to 50 keV, proportional counters have advantages over other types of detectors; they provide energy resolution and they can be made relatively easily with very large window areas.
A proposal for an X-ray experiment for Cos-B
Authors: Willmore A. P.
Published: July 2016

It was proposed that the COS payload should include an experiment to study cosmic γ-rays and one for cosmic X-rays. From a scientific point of view the association of these experiments is clearly valuable, the more so in view of Ogelmann's suggestion that the γ-rays observed by Clark, Garmire and Kranshaar and by Hutchinson represent the high energy extension of the spectra of galactic X-ray sources. It may, however, be argued that the X-ray sources can independently be studied and that, in any case, the most important sources near the galactic plane will be well enough known by the launch date of the COS satellite. This argument may not be valid in view of the observed variability of X-ray sources, but in any case a strong case can be made for the proposed kind of experiment.
Hard X-rays from the southern sky
Authors: Lewin Walter H. G. , Mcclintock Jeffrey E. , Smith William B.
Published: July 2016

On March 20, 1969, we scanned the Southern sky for 8 hours in a manner similar to that during our October 15, 1967 observations. A quick look at the data shows clearly that the brightness of Cen XR-2 in the energy range above 20 keV has significantly decreased since our first observation. At this stage of the data analysis we can put an upper limit on the intensity of Cen XR-2 which is 1/3 the intensity observed by us on October 15, 1967. From further data analyses we will be able to determine the intensity of the source more precisely.

During the same flight we observed Sco X-l, Nor XR-2, and the sources M-l, M-2, M-3, and M-4. Results on these observations will become available by May 1970.
X-ray polarization from Sco X-1 and Tau X-1
Authors: Novick R.
Published: July 2016

No text nor Summary was communicated by the Author.
Non-solar gamma and X-ray astronomy: optical observations: (Invited discourse)
Authors: Johnson Hugh M.
Published: July 2016

An optical astronomer enters this field only by courtesy of those X-ray astronomers who pay some attention to accurate positional measurements of X-ray sources. So my first and last words are to ask X-ray observers to give more time to establishing positions of X-ray sources. It appears that in fact most effort has been spent on spectral measurements of X-rays, and this has led just to the classification of sources according to either of two mechanisms for the production of the continuum. In one or two early instances the extrapolated X-ray spectrum has been useful for predicting the brightness of the optical counterpart to be found. A typical uncertainty of making optical identification is that of Vel XR-1 for which Gursky et al. (1968) have given a position with an error box of 3 square degrees. One candidate I can suggest for this is CU Vel, the only variable star of the 1958 General Catalogue of Variable Stars inside the error box. It is interesting because it is assigned to the U Gem class with a range of photographic magnitudes from 10.7 to 15.5. The stellar spectrum has not been observed.
A search for pulsed hard radiation from the Crab Nebula
Authors: Fishman G. J. , Harnden F. R. , Haymes R. C.
Published: July 2016

This paper reports the detection of repetitive pulses of hard X-rays and gamma rays in data obtained in mid-1967 from the Crab Nebula. The pulses are believed to originate from NP0532 since the observed repetition period is what would be expected on the basis of an extrapolation of recent optical data obtained for NP0532 back to the time of the observation.
Rotating neutron stars, pulsars, and cosmic X-ray sources
Authors: Tucker Wallace H.
Published: July 2016

The purpose of this paper is to discuss the relationship between rotating neutron stars, pulsars, and cosmic X-ray sources. The latter may be divided into at least two classes: the sources with large angular diameters, such as the Crab Nebula, and those with small angular diameter, such as Sco X-1. I submit that a basic model, consisting of a rotating neutron star losing mass in the presence of a large magnetic field, can account for both types of X-ray source. The extended sources represent the case where the energy in the ‘neutron-star wind’ is greater than the magnetic energy. The streaming protons and electrons deposit their energy far out into the nebula in a shock transition region. The relativistic electrons responsible for the extended sources of radio, optical and X-ray emission are produced in the transfer of energy between the protons and electrons in the shock wave, and by magnetic pumping in hydromagnetic waves which are generated by fluctuations in the mass loss rate. The compact sources, such as Sco X-1, represent the other extreme where the magnetic energy dominates, so that no mass loss occurs. The particles are then accelerated and radiate in radiation belts around the neutron star, resulting in a source with a small angular diameter.
Some possible implications of the radio emission of Sco X-1
Authors: Feldman P. A. , Silk J. I.
Published: July 2016

Recent observations of radio emission from Sco X-1 at centimeter wavelengths by Andrew and Purton (1968) and by Ables (1969) have added an important new dimension to the study of galactic X-ray sources. We have considered two alternative interpretations of the radio emission from this object. First, we discuss whether it is possible to attribute the radio emission of Sco X-1 to thermal bremsstrahlung from an optically thin plasma at a temperature of 15 to 20 keV. This interpretation would have the merit of relating the radio properties to the existence of a hot, flaring plasma component whose presence has been invoked to explain the observations of hard X-rays (≳ 35 keV) from this object (Peterson and Jacobson, 1966, Buselliet al., 1968, Riegleret al., 1968, Riegler, 1969, Agrawalet al., 1969a, McCracken, 1969). That the 6-cm radio emission and the hard X-radiation should be found to vary by similar amounts over similar time scales lends this hypothesis a certain appeal. However, the measurement at 11 cm of flux density amounting to ≈0.07 flux units (1 flux unit ≡ ≡ 10−23erg cm−2sec−1Hz−1) reported at this Symposium by McCracken makes it virtually untenable to regard the radio emission of Sco X-1 as arising from thermal origins. Excessive optical and infrared continuum radiation would be produced; moreover, the shape of the radio spectrum is inconsistent with any conceivable thermal model. An explanation for the radio emission of Sco X-1 must therefore be sought in terms of some non-thermal radiation mechanism.
2–20 keV X-ray sky background
Authors: Boldt E. A. , Desai U. D. , Holt S. S. , Serlemitsos P. J.
Published: July 2016

The diffuse background of 2–20 keV X-rays over a band of the sky extending from Scorpius to the North galactic pole is found to be isotropic to within 5%, with a spectrum given bywheren= (1.35 ±0.100.07).

A comparison with spectra at higher energies indicates that the lower energy spectrum is flatter, corresponding to an apparent unit change in spectral index within the band 20–80 keV. A spectral break in this energy region has been discussed in connection with the collisional energy loss lifetime for metagalactic protons that radiate X-rays via inverse bremsstrahlung collisions with the ambient electrons of the intergalactic medium (Boldt and Serlemitsos, 1969; Hayakawa, 1970).
Theoretical Description of the Interstellar Medium
Authors: Field George B.
Published: July 2016

As excellent reviews have appeared recently (Spitzer, 1968a; Pikel'ner, 1968a) we shall consider here only some special topics where progress is being made – thermal properties of Hi and Hii clouds, and shock waves. The components of the medium which are dynamically important are neutral atoms, charged ions and electrons, grains, cosmic rays, magnetic field, and light. In Table I we indicate the degree of momentum coupling among these components. The main mass of the medium, in ions and atoms, is well coupled through collisions, with a mean free path λ ≈ 10−3 pc, and may usually be treated hydrodynamically. Parker (1965) has shown that for many purposes the cosmic-rays can be considered as a separate gas, strongly coupled to the magnetic field. The coupling of the atom-ion gas to the magnetic field is through the magnetic forces on the ions, which transmit the forces to the neutral atoms by collisions unless the differential stresses on the two components are unusually large. Grains are not coupled strongly to any other component, as their stopping distances are of the order of parsecs and their gyro-periods of the order of 104 yr. The coupling of grains to radiation pressure can lead to interesting differential effects. Light is important in carrying away thermal energy but does not critically affect the momentum balance of the gas. A possible exception is the Ly-α radiation field discovered by Kurt and Sunyaev (1967) which has a pressure of 10−13 dyne cm−2. If this phenomenon is common in interstellar space, it could have effects.
Discussion following the Report by Kadomtsev and Tsytovich
Authors: Colgate S. A.
Published: July 2016

The following discussion was long and chaotic, in spite of the energetic efforts of the Chairman. Apparently the subject was unfamiliar to many participants. I did quite some reshuffling. A long contribution by Ozernoi on photon whirls in the primeval Metagalaxy has been transferred to Chapter 13.
Discussion following Mezger's Report
Authors: Shklovskii I. S.
Published: July 2016

The Discussion has been rearranged into five sections: 1. Density Concentrations, Cocoon Stars, and OH Sources; 2. The Carbon Recombination Line; 3. The He/H Abundance; 4. Various Shorter Comments; 5. A New Mechanism for Star Formation. A part of the Discussion which related to Spiegel's Report has been transferred to Chapter 13. A short exchange on Hi shells around Hii regions has been deleted and added to Chapter 5. A short part on the dust cloud in Orion at the end of Section 4 has been transferred from Tuesday, September 16.
The Gaseous Content of Galaxies
Authors: Roberts Morton S.
Published: July 2016

A general review is given of the content and distribution of interstellar gas within galaxies. The constancy of the ratio N(He)/N(H), independent of galaxy type (spirals and irregulars), is discussed and the possible mechanisms for this constancy are considered. The helium abundance does not vary across the disk of spirals, although nitrogen and possibly other elements do.

The gross features of the neutral hydrogen distribution in our Galaxy and other systems are described. In spirals, the peak of the radial distribution of Hi is located well away from the optical center. This is not the case for irregular-type systems. A possible correlation of the relative location of the maxima of Hi and Hii distributions with galaxy type is described. Many spirals studied with high enough relative angular resolution show concentrations of Hi in their outermost regions. These may be due to hydrogen companions or warps in the hydrogen plane. Hydrogen ‘bridges’ are described and a new example for the triple system M81–M82–NGC 3077 is given. This latter case may be an extreme example of distortion by companion galaxies of the Hi associated with a massive galaxy.

The neutral hydrogen content of a galaxy and its correlation with other integral properties is discussed. The absorption profile due to hydrogen associated with the radio galaxy Centaurus A is given. Comparison of optical and 21-cm measurements of galaxian redshifts shows excellent agreement over the radical velocity range −400 to + 5200 km s−1. There is, however, a systematic difference between 21 cm and optical redshifts over the range ∼ 1200 to ∼ 2400 km s−1 for optical values based on blue-sensitive spectra. The difference, ∼ 100 km s−1, is most likely due to blending of galaxian and night sky H and K absorption lines. The Hubble Constant is derived from a redshift-21 cm flux relation. Values in the range 78 to 109 km s−1 Mpc−1 are derived. A value of 97 kms−1 Mpc−1 is favored.
Structural and Kinematic Properties of Populations of the Andromeda Galaxy
Authors: Einasto J.
Published: July 2016

New observational data (Spinrad, 1970; Van den Bergh, 1970; Rubin and Ford, 1970) are used to determine structural and kinematic parameters of the nucleus, the subsystem of globular clusters, and interstellar hydrogen in M31.

The mass derived for the nucleus from the new spectrophotometric data is in good agreement with the virial mass 6 × 108M⊙. Model calculations show that there is no appreciable exchange of stars between the nucleus and the bulge. The rotation energy of the nucleus is only 7.5% of the total kinetic energy; the central density is 2 × 106M⊙ pc−3.

The mean radius of the subsystem of globular clusters is 4.5 kpc. This indicates that the subsystem of old stars is not identical with the spheroidal component of the galaxy, whose mean radius is only 1 kpc. Radial velocity dispersion of globular clusters is only half of that of the nucleus. This shows a strong dependence of the velocity dispersion on distance to the center of the galaxy and a bias in mass determination of a galaxy from velocity dispersion near the nucleus.

On the basis of data on rotation two mass distribution models have been found, differing from each other in respect of the mass concentration to the center. Spectrophotometric data on the stellar content of the bulge are urgently needed to solve the mass distribution problem.
The Population I Content of the Elliptical Companions of M31
Authors: Hodge P. W.
Published: July 2016

Twenty years ago Walter Baade pointed out the remarkable fact that two of the four elliptical galaxy companions of M31 (namely NGC 185 and 205) contained apparent Population I in their central areas, evidenced by the presence of dust clouds and a dozen or so OB stars. I wish to report here on some observations of these stars and absorption regions, made in an attempt to understand the origin of this anomalous material and its relevance, if any, to the pattern of galaxy development.
Radio-Emission from Supernovae Remnants in Distant Galaxies
Authors: Notni P. , Oleak H. , Richter G.-M.
Published: July 2016

It is suggested that some 5C2 radio sources previously identified with normal spiral galaxies, are associated with supernova remnants in these galaxies. This hypothesis is tested by the relative radio and optical positions and by luminosity estimates. It could be further tested by possible coincidences of Ohio radio sources with known supernovae, and also by predicted decreases in radio emission.
Mass-Luminosity Ratios and Sizes of Giant Elliptical Galaxies
Authors: King Ivan R. , Minkowski Rudolph
Published: July 2016

Observations of velocity dispersion and of light distribution at the centers of 22 galaxies, mostly ellipticals give M/L values of 15 to 40 for giants of all luminosities with smaller values for intrinsically faint galaxies. Core radii within which surface brightness drops by a factor of two are typically 50–100 pc with a range from 2 to several hundred parsecs. Elliptical galaxies fit the modified isothermal models used for clusters, while later types have a flatter density gradient. Complete results will be published elsewhere.
Infrared Radiation from Compact Objects
Authors: Neugebauer G.
Published: July 2016

Current infrared observations of Seyfert galaxies, QSOs, and compact galaxies in the lists of Markarian and Zwicky have been reviewed. The bright Seyfert galaxies generally show similar infrared excesses at the longer wavelengths accessible from the ground. Only NGC 1068 has been observed, by F. J. Low, in the 100μ region; if the spectral distributions of all Seyfert galaxies are similar to that of NGC 1068, the intrinsic luminosities vary from 1 to 100 × 1044 erg s−1. Measurements by Kleinmann and Low, Gillett and Stein, Pacholczyk, and Penston and Neugebauer at 10 and 2μ apparently confirm variability of NGC 1068 and NGC 4151 on a time scale too short to allow the infrared radiation to come predominantly from dust shells.

The published infrared observations of QSOs have been limited to wavelengths shorter than 3.5μ except for 3C 273. The energy distributions either show a power law fall-off, a flat spectrum, or a combination of these two. Those four QSOs which show large variability all have steep power law spectra. If one accepts that the distance of QSOs are cosmological, the extrapolated luminosity at 2μ of several QSOs exceeds that of 3C 273. The integrated luminosity of 3C 273 depends critically on the spectrum in the unobserved 10–1000μ region, but is probably in the range 1047 to 1048 erg s−1.

The infrared observations of the compact Markarian and Zwicky objects show a correlation between the infrared excess and the broad optical emission lines. Presumably the infrared can be used to differentiate between the stellar and non-thermal components of the radiation from these objects.
Compact Radio Sources in the Nuclei of Elliptical Galaxies
Authors: Ekers R. D.
Published: July 2016

Ten percent of the intrinsically bright elliptical galaxies contain compact radio sources (angular size < 3 arc sec) with radio luminosity ∼ 1040 erg s−1. The presence of a compact source is correlated with the presence of extended radio emission and with the presence of optical emission lines.
Identification Optique et Photométrie de Radiosources du Catalogue 3CR
Authors: Wlérick Gérard , Lelièvre Gérard , Véron Philippe
Published: July 2016

Using a Lallemand electronic camera, optical identifications for several 3CR radio sources have been made. Photometry has been obtained for objects as faint as B ≃ 21.25. It is suggested that some of the identifications may have redshifts in excess of z = 3.
A Probable Mechanism of Repeated Explosions of Compact Objects
Authors: Ozernoy L. M.
Published: July 2016

This paper considers a magnetoid model for nuclei of compact objects in which repeated explosions are caused by instability in twisted magnetic fields. The derived frequency and energy of individual explosions agrees with observations.
Cosmological Information from Galaxies and Radio Galaxies
Authors: Peach J. V.
Published: July 2016

An account is given of recent developments in the derivation of the value of the Hubble parameter applicable to regions beyond the local anisotropy. Recent observations relevant to interpretations of the magnitude-redshift diagram for cluster galaxies are discussed, in an attempt to assess uncertainties in the value of the deceleration parameter.
Ejection of Small Compact Galaxies from Larger Galaxies
Authors: Arp Halton C.
Published: July 2016

Recent observational evidence is discussed, showing that (1) Galaxies eject matter; (2) Ejection of matter tends to take place in approximately opposite directions; (3) When the ejected matter is in the form of a smaller, companion galaxy, that galaxy tends to have a relatively high surface brightness and small diameter; and (4) Compact companion galaxies generally have higher redshifts than the galaxies from which they were ejected.
Cosmological Evidence from QSOs and Radio Galaxies
Authors: Rees M. J.
Published: July 2016

Cosmological evidence provided by counts of radio and optical objects, and additional evidence yielded by QSO redshifts, are discussed. The nature of the QSO redshifts is considered, as are the evolutionary properties of these and other objects, and possibly important cosmological investigations using QSOs and radio sources are mentioned.
Radio Source-Counts and Cosmology
Authors: Rowan-Robinson M.
Published: July 2016

A review is given of the cosmological implications of radio source-counts.
Concerning the Primordial Abundance of Helium in Quasi-Stellar Sources
Authors: Silk Joseph
Published: July 2016

Primordial temperature fluctuations, which appear to be necessary in order to explain aspects of galaxy formation, can lead to observable effects in some objects. In QSS and other compact systems a correlation of absolute luminosity with primordial helium content is predicted.
General Remarks on Orbit and Ephemeris Computation
Authors: Marsden B. G.
Published: July 2016

Present and future requirements concerning ephemeris prediction for comets (particularly the short-period comets) are discussed, with reference to both positions and magnitudes.
On the Application of Hansen's Method of Partial Anomalies to the Calculation of Perturbations in Cometary Motions
Authors: Skripnichenko V. I.
Published: July 2016

The main points of the method of partial anomalies are described. The method makes it possible to obtain analytical solutions for comets moving in orbits with high eccentricities. The method may be applied, in particular, to systems in which the orbits of the disturbed and disturbing bodies have points equidistant from the Sun. The method is applied to the calculation of the general perturbations by Saturn on P/Tuttle.
A Numerical Method of Integration by Means of Taylor-Steffensen Series and Its Possible Use in the Study of the Motions of Comets and Minor Planets
Authors: Myachin V. F. , Sizova O. A.
Published: July 2016

The Taylor formula is used directly in a method of numerical integration of the n-body problem of celestial mechanics; the derivatives in the expansion of the coordinates are calculated successively at each integration step according to the generalized Steffensen rule. The proposed method is the most precise of all numerical methods based on the predetermined part of the Taylor series. The method is used with a variable number of derivatives at each integration step and also with a variable step. The cumulative error in the coordinates increases more slowly in our method than in any other. We can apply the method to the study of the motion of a comet or minor planet, taking into account the perturbations by eight major planets; the method allows for the simultaneous integration of a great number of objects of zero mass.
The Problem of Elaboration and Classification of Observational Material for One-Apparition Comets
Authors: Bielicki M.
Published: July 2016

A new, purely objective criterion is developed for the rejection of observations with nonaccidental errors. A mathematically rigorous procedure is devised for the determination of the weights of individual observations.
Nongravitational Forces and Periodic Comet Giacobini-Zinner
Authors: Yeomans D. K.
Published: July 2016

Observations of P/Giacobini-Zinner could not be successfully represented for more than two successive apparitions using Newtonian equations of motion. The comet's motion has a secular deceleration approximately equal to 0.08 day per (period)2. After extending the differential correction to include nongravitational terms in the equations of motion the observations were successfully represented over the time intervals 1900–1946, 1913–1959, and 1939–1965. There is an indication that the magnitude of the nongravitational forces increases with time and that the motion of the comet was discontinuous between 1959 and 1965. A Giacobinid meteor shower prediction has been provided for the 1972 return.
The Motion of Hidalgo and the Mass of Saturn
Authors: Marsden B. G.
Published: July 2016

The principal features of the motion of Hidalgo over the interval 1400–2900 are described. The possibility that this object is an extinct (or nearly extinct) comet nucleus is discussed. A determination of the mass of Saturn, using observations of Hidalgo during 1920–1964, is presented and compared with other recent determinations.
A Nongravitational Effect in the Simulation of Cometary Phenomena
Authors: Kajmakov E. A. , Sharkov V. I. , Zhuravlev S. S.
Published: July 2016

Experimental results for the determination of the exhaust thrust developed by vacuum-sublimation products of H2O ice and frozen aqueous electrolytes are described. The contribution of the exhaust thrust to nongravitational effects on comets is discussed.
The Major Planets as Powerful Transformers of Cometary Orbits
Authors: Kazimirchak-Polonskaya E. I.
Published: July 2016

The equations of motion of many of the comets of the Jupiter and Saturn families have been integrated for a period of 400 yr. Several examples illustrate the role of the major planets, especially Jupiter, in the evolution of these orbits: in such cases comets may be captured by Jupiter from Saturn's family or ejected from Jupiter's family into Saturn's, and so on; the possible escape of a comet along a hyperbolic orbit and the capture by Jupiter of a comet from a hyperbolic orbit are also demonstrated. Fictitious comets of the Uranus and Neptune families are also studied. It is concluded that a combination of diffusion theory and capture theory is in good agreement with the observations and makes it possible to consider both long- and short-period comets as part of a unified cometary complex.
On the Origin of Comets and Their Importance for the Cosmogony of the Solar System
Authors: Fesenkov V. G.
Published: July 2016

The processes in interstellar space, as well as the structure of nebulae – including the numerous small condensations around newly formed stars – suggest a relationship to the formation of the cometary cloud surrounding the Sun. Study of carbonaceous chondrites has revealed that in the earliest stage of the solar system's existence frequent periods of brief heating occurred, leading to the formation of very complex organic compounds and also of chondrules of crystalline structure. This was most probably a consequence of cometary collisions. The Tunguska phenomenon illustrates some consequences of a similar collision.
Investigation of the Orbital Stability of Minor Planets with Cometary Eccentricities
Authors: Chebotarev G. A. , Belyaev N. A. , Eremenko R. P.
Published: July 2016

The evolution of the orbits of 19 asteroids of particular interest has been studied over the interval 1660–2060, perturbations by Venus to Pluto being taken into account. Information was obtained about the encounters with Venus, the Earth, and Mars. A few approaches of Hidalgo to Jupiter were noted. In distinction to the orbits of short-period comets, the orbits of the 19 asteroids are stable throughout the 400-yr interval.
Theoretical Cometary Radiants and the Structure of Meteor Streams
Authors: Kramer E. N.
Published: July 2016

Observational data on radiants of meteor showers and the structure of meteor streams may be used as an indirect source of information about the evolution of cometary and meteor orbits. Investigation of the structure of some meteor streams provides evidence for comparatively high velocities of ejection of meteoroids from cometary nuclei. Further evolution of the streams is determined by planetary perturbations and other factors, the influence of which depends on the size and composition of the meteoroids.
Statistics of the Orbits of Meteor Streams and Comets
Authors: Lebedinets V. N. , Korpusov V. N. , Sosnova A. K.
Published: July 2016

From radar observations carried out during 1967–1968 a catalogue of 20 000 orbits was obtained. A method has been developed for identifying meteor streams and associations, and the orbits of the meteors recorded during January-April 1968 have been analysed. Among them 163 streams have been identified, and these contain 33.5% of the total number of orbits. Comparison with the orbits of the short-period comets of q < 1.1 AU shows considerable differences.
Formation of Comets in Meteor Streams
Authors: Trulsen J.
Published: July 2016

The temporary focusing effect of planetary perturbations on the particles of a meteor stream is studied. It is indicated that allowance for collisions could result in more permanent focusing, leading to the possible formation of a comet.
On the Production of Meteor Streams by Cometary Nuclei
Authors: Katasev L. A. , Kulikova N. V.
Published: July 2016

An attempt is made to use Monte-Carlo techniques to model the process of formation of meteor streams. It is supposed that meteor streams are formed as the result of ejection of meteoroids from a cometary nucleus at perihelion. Possible ejection velocities are determined for the Draconids, Perseids, Leonids, and Taurids. In general the values do not exceed 100 m s-1. The data obtained can also be used to estimate the ages of the streams.
On the Possible Common Origin of Minor Planets, Comets, and Meteors
Authors: Gaska S.
Published: July 2016

For the minor planets, comets, and meteors whose orbital elements are known values of the dispersions σi(a) of the inclination i for intervals of the semimajor axis a have been calculated. Calculations on the minor planets show that, from the point of view of secular perturbations, σi(a) is more stable than ī(a), and we have therefore taken it as a fundamental relation for further considerations. It has been found that the relations σi(a) are linear for minor planets, comets, and meteors with a > 2 AU. The lines are parallel, and for a > 2 AU the σi(a) are proportional to a. Meteors have a second straight line for a < 2 AU, and in this case σi(a) is proportional to 1/a. It is concluded that minor planets, comets, and meteors could have a common origin.
Differential Rotation and Giant Cell Circulation of the Solar Ca+-Network
Authors: Schröter E. H. , Wöhl H.
Published: July 2016

High precision computer controlled tracings of bright Ca+-mottles were performed during 1974 and 1975 at the Locarno Observatory of Göttingen to study solar differential rotation and to search for giant cell circulation pattern. Details of the observing method and the results from observations during 1974 have been published very recently (Schröter and Wöhl, 1975). Our method consists of measuring the position of 5–15 bright Ca+-mottles with respect to the center of the solar disc every 10 to 15 min during 4 h every day. A computer controlled program determines first the center of the disc and immediately afterwards the right ascension and declination of a Ca+-mottle which was centered by the observer into a 1′-diameter spectrograph pinhole by watching a TV-monitor displaying a Ca+-K-line solar image. From a linear least squares fit of the observed positions the solar latitude and longitude were computed for the beginning and the end of the daily 4 h observation period. From this the components in latitude and longitude of the proper motions were derived which result from the differential rotation, possible giant cell circulation and the small scale random walk of these features.
Velocities Observed in Supergranules
Authors: Worden S. P. , Simon G. W.
Published: July 2016

The evolution of the velocity and magnetic fields associated with supergranulation has been investigated using the Sacramento Peak Observatory Diode Array Magnetograph. The observations consist of time sequences of simultaneous velocity, magnetic field, and chromospheric network measurements. From these data it appears that the supergranular velocity cells have lifetimes in excess of 30 h. Magnetic field motions associated with supergranulation were infrequent and seem to be accompanied by changes in the velocity field. More prevalent was the slow dissipation and diffusion of stationary flux points. These observations suggest that surface motions do not exhibit the detailed flux redistribution expected in the random-walk diffusion of magnetic fields. It is suggested that the surface motions are only the reflection of magnetic field-convective motion interactions which occur deeper in the convection zone.
Dynamo Theory and the Solar Cycle
Authors: Stix M.
Published: July 2016

In this paper solutions of the mean field induction equation in a spherical geometry are discussed. In particular, the 22-year solar magnetic cycle is considered to be governed by an axisymmetric, periodic solution which is antisymmetric with respect to the equatorial plane. This solution essentially describes flux tubes travelling as waves from mid-latitudes towards the equator. In a layer of infinite extent the period of such dynamo waves solely depends on the strength of the two induction effects, differential rotation and α-effect (cyclonic turbulence). In a spherical shell, however, mean flux must be destroyed by turbulent diffusion, so the latter process might actually control the time scale of the solar cycle.

A special discussion is devoted to the question of whether the angular velocityincreaseswith increasing depth, as the dynamo waves seem to require, or whether itdecreases, as many theoretical models concerned with the Sun's differential rotation predict. Finally, theories for the sector structure of the large scale photospheric field are reviewed. These describe magnetic sectors as a consequence of the sectoral pattern in the underlying large scale convection, as non-axisymmetric solutions of the mean field induction equation, or as hydromagnetic waves, modified by rotational effects.
Absolute Fluxes of K Chromospheric Emission on the H-R Diagram
Authors: Blanco C. , Catalano S. , Marilli E.
Published: July 2016

Continuing our previous analysis of the chromospheric emission (Blanco et al., 1974), absolute fluxes of the K emission line have been evaluated from 10 Å mm−1 spectrograms of the O. C. Wilson collection for 31 F5-K7 main sequence stars and 172 G2-M5 giants.
On the Spectral Classification of Cool White Dwarfs
Authors: Bues I.
Published: July 2016

The Eggen-Greenstein (1965) classification of cool white dwarfs (DC, DF, DG, λ 4670, λ 4135) was based on the features visible in the spectra of low dispersion. Detailed model atmosphere computations (11000 ≥ Teff ≥ 7000 K) and comparison with spectra observed by Wegner (1974, 1975) show that the variety of the spectra is due to changes in the abundance ratios of C/O, C/H and H/He only. Thus the relative strengths of the C2 and CH-bands can be used for classification and guess of Teff in the range of Teff ≥ 6000 K.
Effects of Abundance Changes on the Spectra of Very Cool White Dwarfs
Authors: Wehrse R.
Published: July 2016

In order to study the atmospheres of cool white dwarfs of spectral types DA, DF and DG, model atmospheres have been calculated for temperatures 5000 ≤ Teff ≤ 7000 K and gravities 7 ≤ log g ≤ 8.5. The helium to hydrogen abundance ratio ranges from 0.1 to 1000. The abundances of the metals ∈M (relative to hydrogen) vary between the solar value ∈⊙M and ∈⊙M/1000. The models are hydrogen and metal line blanketed and in radiative equilibrium. The models with increased He abundance are characterized by a decreased mean opacity since the absorption cross-section of He is much smaller than that of H–. As a result, the spectral lines become stronger and – due to the much higher pressures – much broader. A reduction of the metal contents also increases the pressures. In this case it is caused by the shortage of electron suppliers. Here the spectral lines also become broader, but in general weaker.

These effects strengthen the overlap of the lines due to the high gravity of white dwarfs and more or less lead to a quasi-continuum which may be much below the true continuum. Because of the wavelength dependence of the line density the depression is strongest in the UV and blue spectral region, whereas for wavelengths λ ≥ 4500 Å the difference from the true continuum is only a few per cent. The details will be published elsewhere.
The Helium-to-Hydrogen Ratio of Stars in Young Clusters and Associations
Authors: Nissen P. E.
Published: July 2016

A photoelectric narrow-band index, I(4026), of the He I λ 4026 line has been observed with an echelle spectrometer for B-type stars in young clusters and associations.

Model-atmosphere computations of the Strömgren [c1] index, the Hβ index, and I(4026) as functions of Teff, g and the helium-to-hydrogen ratio have been used to derive these atmospheric parameters from the observed indices for each star.

For the OriOBIb, LacOBI and Sco-Cen associations 11 out of 48 stars in the temperature range from 14 000 to 20 000 K are found to be helium poor in the sense that the derived helium-to-hydrogen ratios lie in the range from 0.05 down to very low values. In the temperature range from 20 000 to 30 000 K no helium poor stars are found, but two stars in OriOBIb are helium rich. Both of these stars show rather strong variations of the I(4026) index.

All stars in h + χ Per and CepOBIII are apparently helium deficient compared to nearby field stars.