bluuebunny/crossref_metadata_2025 huggingface dataset:
The s-Process in the Yellow Symbiotic AG Draconis
Authors: Cunha Katia , Smith Verne V. , Jorissen Alain
Published: July 2016

An abundance analysis of the yellow symbiotic system AG Draconis reveals it to be a metal-poor K giant ([Fe/H] = −1.3) which is enriched in the heavy s-process elements. This star thus provides a link between the symbiotic stars and the binary barium and CH stars which are also s-process enriched. These binary systems, which exhibit overabundances of the heavy elements, owe their abundance peculiarities to mass transfer from thermally-pulsing asymptotic giant branch stars, which have since evolved to become white-dwarf companions of the cool stars we now view as the chemically peculiar primaries. A comparison of the heavy-element abundance distribution in AG Dra with theoretical nucleosynthesis calculations shows that the s-process is defined by a relatively large neutron exposure (τ = 1.3 mb−1), while an analysis of the rubidium abundance suggests that the s-process occurred at a neutron density of about 2 × 108 cm−3. The derived spectroscopic orbit of AG Dra is similar to the orbits of barium and CH stars. Because the luminosity function of low-metallicity K giants is skewed towards higher luminosities by about 2 magnitudes relative to solar-metallicity giants, it is argued that the lower metallicity K giants have larger mass-loss rates. It is this larger mass-loss rate that drives the symbiotic phenomena in AG Dra and we suggest that the other yellow symbiotic stars are probably low-metallicity objects as well.
Mass-losing AGB Stars in the LMC
Authors: Van Loon Jacco Th. , Zijlstra Albert A. , Whitelock Patricia A. , Loup Cecile , Waters L.B.F.M.
Published: July 2016

We show the results of an infrared study of a sample of heavily obscured AGB stars in the LMC. Both carbon-rich and oxygen-rich mass-losing AGB stars can be found at both high and low luminosities, but the percentage of carbon stars decreases with increasing luminosity. The optical depth of the circumstellar envelopes also decreases with increasing luminosity, while the mass-loss rates are (nearly) constant with luminosity. We also show tentative evidence for having found the first post-AGB stars in the LMC.
The Variability of R, N, and C Stars from HIPPARCOS and AAVSO Data
Authors: Grenon Michel , Mattei Janet A. , Eyer Laurent , Foster Grant
Published: July 2016

Accurate photometry was obtained for all program stars during the 3.3-year HIPPARCOS mission. The final observing program included several hundred Mira (M), long-period semiregular (SR), and irregular (L) variables. A detailed calibration of the aging of the optics allowed the evaluation of very precise magnitudes over the whole range of star colors. Since the time coverage of the satellite observations was not sufficient to describe the behavior of M, SR, or L type variables, smooth curves were fitted statistically to the dense AAVSO observations. These curves were then transformed to the HIPPARCOS system in order to complement the HIPPARCOS photometry and thus produce precise light curves with fuller time coverage, for a set of several hundred late-type variables, including most carbon stars brighter than V = 12.4 at minimum luminosity. A preliminary discussion of the behavior of C stars, as observed from space in the broad Hp band, is given.
Infrared Light Curves of Carbon-Rich Variables
Authors: Whitelock Patricia
Published: July 2016

Long-term trends in the infrared (JHKL) light curves of various carbon variables are described. Some stars, e.g. the semi-regular variables R Scl and GM CMa, show multiple periodicities; others, particularly the Miras with moderately thick dust-shells, show more erratic long-term changes. The light curves for R For, which have been intensively monitored over 20 years, show a pattern which is reminiscent of that seen for R CrB stars. This pattern is superimposed on regular large-amplitude Mira pulsations. The multi-periodic and erratic behaviour of these stars is compared with the predictions from various models.
The Case for S Star Binaries
Authors: Ake Thomas B.
Published: July 2016

Several lines of evidence point to a scenario in which Tc-poor S stars are the cooler analogs to the Ba II stars, i.e. they are binary systems where the peculiar atmospheric composition of the primary star is due to mass accreted from a secondary star long ago. Cases have been found where such S stars have WD or main-sequence companions, but an increasing number are found to be in interactive, symbiotic-like systems. Evidence of wind shocks, gas-streaming, and/or accretion disks in these systems attest to the current proximity of the components and provide striking evidence that accretion can be an important mechanism in their chemical evolution. Interactive effects are not as prominent in Ba II stars, presumably because of the lack of a strong wind from the primary star.
Dust Emission from IRC+10216
Authors: Ivezić Željko , Elitzur Moshe
Published: July 2016

Infrared emission from the dust shell around IRC+10216 is analysed in detail, employing a self-consistent model for radiatively driven winds around late-type stars that couples the equations of motion and radiative transfer in the dust. The resulting model provides agreement with the wealth of available data, including the spectral energy distribution in the range 0.5-1000 μm, and visibility and array observations. Previous conclusions about two dust shells, derived from modelling the data with a few single-temperature components of different radii, are not supported by our results. The IR properties vary with the stellar phase, reflecting changes in both the dust condensation radius r1 and the overall optical depth τ - as the luminosity increases from minimum to maximum, r1 increases while τ decreases. We find that the angular size of the dust condensation zone varies from 0.″3 at minimum light to 0.″5 at maximum. The shortage of flux at short wavelengths encountered in previous studies is resolved by employing a grain size distribution that includes grains larger than ∼ 0.1 μm, required also for the visibility fits. This distribution is in agreement with the one recently proposed by Jura in a study that probed the outer regions of the envelope. Since our constraints on the size distribution mostly reflect the envelope's inner regions, the agreement of these independent studies is evidence against significant changes in grain sizes through effects like sputtering or grain growth after the initial formation at the dust condensation zone.
The Neutral Envelopes around AGB and Post-AGB Objects
Authors: Olofsson H.
Published: July 2016

This review discusses the large-scale geometry and kinematics of envelopes around evolved stars, as inferred from radio line observations of circumstellar molecules, as a function of the evolutionary stage of the central object. In particular, the drastic change in morphology from largely spherical envelopes around asymptotic giant branch stars to distinctly non-spherical neutral envelopes around planetary nebulae is addressed. In addition, the small-scale structure of the envelopes, i.e., whether the circumstellar medium is smooth or clumpy, is discussed. Finally, a scenario for the morphological evolution, based on the assumption of a highly clumped medium, is presented.
Extended Dust Shells around Carbon Stars in the Infrared and in Optical Light
Authors: Izumiura Hideyuki , Waters L.B.F.M. , De Jong T. , Loup C. , Hashimoto O.
Published: July 2016

We investigate the structure of extended dust shells around optical carbon stars in the far-infrared and in optical light. In the optical we have discovered that R Scl and U Ant are associated with circularly extended emission, the radii of which are about 20″ and 58″, respectively. The emission is probably scattered light of the central star by dust grains in their circumstellar shells. In the far-infrared we have discovered a double shell structure surrounding U Ant in high resolution IRAS images, which is direct evidence of a periodic change of mass-loss on a time-scale of the order of 104 years in the AGB evolution. Relating the two shells to two consecutive thermal pulses allows for a self-consistent determination of the interpulse period, core-mass, luminosity, and distance. Direct mapping of Y CVn at 90 and 160 μm with ISOPHOT on board ISO has revealed a very extended detached dust shell around this star. The mass-loss rate is found to have decreased drastically by two orders of magnitude 1.4×104 years ago, which should be an important clue to the understanding of J-type stars.
A New Optical Observatory in Turkey
Authors: Aslan Zeki , Selam Selim O. , Esendemir Akif
Published: July 2016

Site-testing observations carried out between 1982 and 1986 have shown that Southwest and Southeast Turkey contain good potential observatory sites. The mountain known as Bakirhtepe near the Mediterranean coast was found to be a good site with a high percentage of nights with clear skies and good seeing.

Here we summarize the results of the site-test observations and give general information about the site.
Intensities and spectra of several galactic X-ray sources
Authors: Batstone R. , Cooke B. , Gott R. , Stewardson E.
Published: July 2016

No text nor Summary was communicated by the Authors.
Sudden changes in the intensity of high energy X-rays from Sco X-1
Authors: Agrawal P. C. , Biswas S. , Gokhale G. S. , Iyengar V. S. , Kunte P. K. , Manchanda R. K. , Sreekantan B. V.
Published: July 2016

In this note we wish to report briefly the observation of sudden changes in the intensity of Sco X-1 by a factor of about 3 recorded in the energy interval 29.9–52.3 keV on December 22, 1968 between 04 h 27 m and 05 h 53 m UT. The observation was made with an X-ray telescope flown in a balloon from Hyderabad, India. The balloon was launched at 0200 hr UT and reached the ceiling of 7.5 g/cm2 of residual atmosphere at 0435 hr UT. The X-ray telescope consisted of a NaI(T1) crystal with an area of 97.3 cm2 and thickness 4 mm, surrounded by both active and passive collimators. The telescope was mounted on an oriented platform which was programmed to look in four specified directions successively, of azimuths, Φ=0°, 110°, 180° and 310° (Φ=0° being North and Φ=90°, West), spending about 4 min in each direction during a cycle of period of about 16 min. The axis of the telescope was inclined at an angle of 32° with respect to the zenith. A pair of crossed flux gate magnetometers provided information every 8.2 sec on the azimuth of the telescope. The pulse heights from the X-ray detector were sorted into several channels extending from 10 to 120 keV. An Am241 source came into the field of view of the telescope once in 15 min for about 30 sec to provide in-flight calibration of the detector. The meridian transit of Sco X-1 was at 0454 hr UT. Just before the balloon reached the ceiling Sco X-1 was in the field of view of the telescope for 3 min and 41 sec. After the balloon reached ceiling, Sco X-1 was in the field of view of the telescope on five occasions between 0443 and 0553 hr UT. During the last observation, however, the balloon had lost altitude by about 1 g/cm2. The excess counts due to Sco X-1 were obtained by subtracting the counting rates corresponding to the North direction which did not include any known X-ray sources. The observation on Sco X-1 in the 1st cycle was made while the balloon was still ascending and consequently the interposed grammage was changing from 10.5 to 9.7 g/cm2. However, for the energy range under consideration, the change in the background counting rate was not significant and there cannot be any doubt regarding the genuineness of the excess counts recorded.
Angular size and position of the X-ray source Cyg-X-1
Authors: Matsuoka M. , Miyamoto S. , Nishimura J. , Oda M. , Ogawara Y. , Wada M.
Published: July 2016

We performed a couple of balloon experiments to measure the size and the location of Cyg-X-1 using the techniques of the modulation collimator [1]. The angular periods of the modulation collimator were 26′ and 10′ for the respective flights corresponding to the approximate angular resolutions of the size determination and location, 3′ and 1′ respectively. Preliminary results of the experiment with 3′ resolution are reported here.
Interstellar absorption of X-rays emitted by supernova remnants
Authors: Gorenstein P. , Kellogg E. M. , Gursky H.
Published: July 2016

An X-ray observation of the Cassiopeia Region by the ASE group from a sounding rocket on December 5, 1968, has resulted in the determination of locations for two sources that are precise to about 0.1 of a square degree. The positions of two well-known radio sources Cas A and SN 1572 (Tycho's Supernova), objects which are remnants of relatively recent galactic supernova, are consistent with these locations. Inasmuch as that region of the galaxy does not appear to contain nearly as large a concentration of objects as the galactic center, it is reasonable to make the identification between the X-ray sources and the supernova remnants on the basis of there being a small a priori probability of having an accidental coincidence within 0.1 square degrees. Cas A is almost certainly the same source as Cas XR-1 which the NRL group saw in an earlier survey [1]. During the December flight the Crab nebula was also observed for a short time interval.
Ionospheric effects of X-rays from discrete galactic sources
Authors: Ananthakrishnan S. , Chakravarty S. C. , Ramanathan K. R.
Published: July 2016

Observation of the field strength of low frequency radio waves (164 kHz) transmitted during night hours from Tashkent and received at Ahmedabad show increased absorption around the sidereal times of the transit of the X ray stars Sco X-1 and Tau X-1. It is estimated that the ionization in the D region produced by these X-ray stars can explain the observed changes in field strength.
Identification of X-ray sources at Cerro Tololo inter-American observatory
Authors: Kunkel W. E. , Blanco V. M.
Published: July 2016

The telescope used for identification of X-ray sources at the Cerro Tololo Inter-American Observatory is the Curtis Schmidt Telescope. This telescope is located at Tololo by agreement with the University of Michigan. The field of the telescope is 5° × 5° and its correcting aspheric plate has negligible chromatic aberration over the range 3200 to 10000 Å. This latter feature makes it an ideal instrument for multicolor survey work.
X-ray pulsar in the Crab Nebula
Authors: Friedman H.
Published: July 2016

Prof. Friedman did not communicate any text or Summary of his communication.
A lower limit to the magnetic field in the Crab Nebula from cosmic γ-ray experiments at 1011 eV
Authors: Fazio G. G. , Helmken H. F. , Rieke G. H. , Weekes T. C.
Published: July 2016

The 10-m optical reflector at Mt. Hopkins, Arizona, has been used to search for cosmic γ-Rays by the detection of atmospheric Čerenkov radiation from energetic particle showers. Approximately 100 drift scans of the Crab Nebula during 1968–69 have yielded no positive evidence of a γ-Ray flux. The upper limit to the flux at 1.7 × 1011 eV is 2.0 × 10−10 photons/cm2 sec. Assuming γ-Rays of this energy are produced by Compton scattering, a lower limit on the average magnetic field in the Crab Nebula is 1.5 × 10−4 gauss. This experiment also verifies previous evidence that the high-energy electrons in the Crab Nebula are not the secondary products of high-energy proton interactions but must have been accelerated from lower energies.
Review of observational results on γ-ray background: (Invited discourse)
Authors: Clark G. W. , Garmire G. P. , Kraushaar W. L.
Published: July 2016

Recent observations in the X- and γ-Ray region of the electromagnetic spectrum have given strong evidence for the existence of an extragalactic intensity with a slowly steepening power law spectrum in the region 103 to 108 eV. Further data from the OSO-III high energy γ-Ray detector are in agreement with earlier published reports, and suggest that the γ-Rays from high galactic latitudes have a softer spectrum than those from the galactic plane.
The low energy diffuse cosmic X-radiation
Authors: Wilson B. G. , Baxter A. J.
Published: July 2016

Recent measurements of the low energy diffuse cosmic X-radiation are reported. The results indicate that the large flux observed below 1 keV is inconsistent with an extrapolation of the power law spectrum observed above 2 keV. While the radiation between 2 and 10 keV appears largely isotropic, at least to the limits of resolution of the detector, the 0.27 keV radiation shows significant asymmetry with respect to galactic latitude.
A model of γ-ray sources in the Galaxy
Authors: Hayakawa S. , Tanaka Y.
Published: July 2016

In a recent observation Clark et al. [1] have found that the intensity of γ-Rays of energies around 100 MeV is strong in the direction of the galactic plane; the observed intensity of the order of 10−4 cm−2 sec−1 rad−1 is greater by an order of magnitude than that predicted on the neutral pion decay hypothesis [2]. It should, however, be remarked that the theory is based on the assumption that cosmic rays are uniformly distributed in our galaxy. The assumption seems doubtful in view of the experimental result that the γ-Ray intensity depends rather strongly on the galactic longitude.
The X-ray emission of a hot dense intergalactic plasma
Authors: Bergeron J.
Published: July 2016

The implications of the existence of a dense, hot, intergalactic plasma are discussed for friedman universes with a zero cosmological constant. The points of interest are the temperature of the intergalactic gas and the degree of ionization of its constituents. The soft X-ray emission of this dense intergalactic gas must be in agreement with the actual observations of isotropic X-ray background around 1–3 keV and 0.27 keV. Moreover the model cannot be in contradiction with the lack of Lyman α absorption in the emission spectra of the quasi-stellar objects.
Galactic line emission from 1–10 keV
Authors: Steigman Gary , Silk Joseph
Published: July 2016

Calculations are given of K-series X-rays produced by interaction of both low energy cosmic rays and diffuse X-rays above 1 keV with heavier ions present in Hi regions. We further consider electron capture to excited states by cosmic ray nuclei of heavy elements, followed by cascades down to the ground state. It is found that the electron capture process may yield appreciable line intensities in the 1–10 keV range in the galactic plane.
Review of Cosmical Gas Dynamics
Authors: Van De Hulst H. C.
Published: July 2016

The subject allotted to me in the program is the ‘Summary of Symposia I–III: problems considered and present status of them’. Perhaps I should have been more cautious when I agreed to this title about two years ago. For it means that, if I do my job well, you will know the present status of all problems and the Symposium is finished today. However, I am sure that, no matter how I try, there will remain enough for other speakers and for other days of discussion. For this reason, in surveying the field, I shall not consciously try to avoid the topics of other speakers. Overlap will do no harm.
Discussion following van de Hulst's Report
Authors: Thomas R. N.
Published: July 2016

This discussion on the opening day of the Symposium started in the afternoon and was consequently rather short. The version presented here is even shorter since some extensive remarks by Zel'dovich and Sunyaev have been transferred to a more proper location, the discussion following the Reports by Weaver and by Field (p. 77).
Discussion following the Reports by Parker and Verschuur
Authors: Pikel'ner S. B.
Published: July 2016

The Discussion has been rearranged into four sections: 1. Various Questions; 2. The Galactic Halo; 3. The Origin of the Magnetic Field; 4. Summary. Section 4 is the outcome of another meeting (on September 17). One very extensive remark has been condensed. The latter part of the discussion on September 12 dealt with the informal meeting on Hi gas and is presented separately as Chapter 6.
Discussion following Lüst's Report
Authors: Weymann R.
Published: July 2016

This discussion actually took place after the Reports by Lüst and by Pottasch. However, the remarks pertaining to Pottasch's Report have been combined with the discussion following Boyarchuk's Report, since the latter two Reports appeared to have more in common than the first two. I have condensed several contributions, notably a very long remark by Gordon.
Mass Loss from Eruptive Stars
Authors: Boyarchuk A. A.
Published: July 2016

The previous reports by Lüst and by Pottasch concerned quasi-stationary mass loss. The loss is called quasi-stationary because the basic characteristics of a star, its temperature and its radius, do not change significantly during the time that a particle needs to flow from the stellar surface out to a point where the stellar influence is negligible. However there are many stars which show significant changes of temperature and radius within a short time. Very often these changes are accompanied by instantaneous ejection of a great amount of material. For example, during the outburst of a nova the ejected mass can reach 10−4M⊙. Such effects are very appreciable in the so-called ‘eruptive variables’, in which the brightness changes spasmodically. It is very likely that the rate and the mechanism of mass loss of eruptive variables are different from that of normal stars.
Electronographic Photometry of Stars in the Globular Clusters of the Magellanic Clouds
Authors: Walker M. F.
Published: July 2016

Due to the linearity, high quantum efficiency, and high storage capacity of electronographic image intensifies, their application to astronomical photometry constitutes an advance equal in importance to those that resulted from the introduction of the photographic plate and the photomultiplier. With existing electronographic image tubes and telescopes of 60-in. aperture stellar photometry is possible to about magnitude 23. Consequently a major advance in the study of the stellar contents of galaxies in the Local Group may now be made.

During 1968–69, the spectracon image intensifier was used on the 60-in. reflector of the Cerro Tololo Observatory for B, V observations of 14 globular clusters in the Magellanic Clouds. Details of the observing program and discussions of the observations so far reduced will appear shortly in papers in the Astrophysical Journal and in Sky and Telescope.
Observations of H II Regions in Sc Galaxies
Authors: Searle Leonard
Published: July 2016

A spectral survey of Hii regions in the galaxies M33, M51, M101, NGC 2403 and NGC 1232 has been carried out. Absolute fluxes have been measured photo-electrically. The energy distribution of the embedded O-association and the intensities of the emission lines have been obtained. The emission spectra can be classified in a one-parameter sequence which is the same for all the galaxies studied. The spectral type is independent of size, shape, surface brightness and density of the Hii region, but does depend on the location of the region in its galaxy.

In the galaxies surveyed there is a close correlation between the distance of an Hii region from the center of the galaxy and the appearance of its spectrum. The line ratios [OIII]/Hβ, Hα/[NII], and [OII]/[NII] all increase by large factors as one passes from regions in the inner spiral arms to those in the outermost arms. The average value of these ratios in a galaxy increases on going from early Sc galaxies to late Sc galaxies. The results show that the N/O abundance ratio (and probably also the O/H abundance ratio) is lowest in irregular galaxies and in the outer parts of late Sc galaxies. It increases towards the center of the spirals and it is highest in the inner spiral arms of the early Sc galaxies. In contrast, the He/H abundance ratio is constant across galactic disks and along the morphological sequence.
Thermal Radio Emission from Normal Galaxies
Authors: Terzian Yervant
Published: July 2016

Thermal radiation from normal spiral galaxies may be detectable at centimeter and millimeter wavelengths. Predictions have been made assuming free-free radiation from Hii regions at Te = 7000 K, and a range of mean electron densities and radii.
The Physical Properties of the Absorption Envelopes of Two QSOs
Authors: Scargle Jeffery D. , Caroff Lawrence J. , Noerdlinger Peter D.
Published: July 2016

The wide absorption troughs of certain resonance lines in the spectra of the QSOs PHL 5200 and RS 23 are produced by pure scattering and must therefore be compensated by an equal amount of emission. Analysis of the transfer of resonance-line radiation through a differentially expanding atmosphere shows that the absorption-emission profiles can be quantitatively understood on this basis.
The Balmer lines in the Seyfert Galaxies NGC 5548 and NGC 4151
Authors: Weymann R. , Cromwell R.
Published: July 2016

The profiles of the Balmer lines in NGC 5548 as reported by Dibai et al. (1968) were somewhat asymmetric, whereas those reported by Anderson (1970) are smooth and symmetric. We present profiles which are strongly asymmetric, resembling those of Dibai et al. Evidently electron scattering is not the sole principal broadening agent and we must deal with velocities ∼ 2500 km s−1 in a very small volume.

The transient nature of the P-Cygni type profiles in the Balmer lines of NGC 4151 has previously been noted (Cromwell and Weymann, 1970). These lines have since disappeared, at the resolution available to us, in a time of 3 months. A model in which frequent outbursts of shells or filaments produce transient features in the Balmer lines, while the accumulated material from past outbursts produces the relatively stable HeI λ 3889 feature, seems the most plausible.
Physical Conditions in Seyfert Type Galaxies Markarian 9, 10 and 42
Authors: Khachikian E. Ye.
Published: July 2016

I would like to present some new data concerning the Seyfert type galaxies Markarian 9, 10 and 42 (Khachikian, 1968; Arp et al., 1968; Khachikian and Weedman, 1969).
The Angular Structures of Some Compact Sources
Authors: Palmer H. P.
Published: July 2016

From 1965 to 1967 radio link interferometers were operated between Jodrell Bank and Malvern, at wavelengths of 21, 11, and 6 cm. Preliminary results were published by Adgie et al. (1965), Barber et al. (1966), Palmer et al. (1967) and Miley et al. (1967). The full analysis of these data has now been completed. Donaldson et al. (1969) report that six sources were unresolved, and they set size limits in the range 0.1 to 0.01 arc sec. Seven sources were found to contain unresolved components, and similar but less complete data were obtained on 33 other sources. Four sources (3C 119, 138, 147, and 237) were shown to have double or more complex structures. (Donaldson and Smith, 1970; Donaldson et al., 1970). The cores of 3C 274 and four other sources were shown to have elongations in the range 0.3 to 0.03 arc sec. One of these is 3C 287, and when the data on this source are combined with those of Clark et al. (1968) at 1660 MHz it appears that this source is a double of separation 0.08 arc sec in position angle 025°. This differs from the interpretation given by Clark et al. Some new data were also obtained on the well known double sources 3C 405 and 1938-15.
Observations of Variable Radio Sources at 8.2 mm
Authors: Efanov V. A. , Moiseev I. G. , Tovmasjan H. M. , Shteinshleger V. B. , Zagatin V. I.
Published: July 2016

Observations of the quasars 3C 273 and 3C 279 at 8 mm were begun in 1967 with the 22-m radio telescope of the Crimean Astrophysical Observatory of the Academy of Sciences of the USSR and have been continued subsequently (V. A. Efanov et al., 1968, 1969, 1970a, 1970b).
High-Resolution Observations of Variable Radio Sources
Authors: Moffet A. T. , Gubbay J. , Robertson D. S. , Legg A. J.
Published: July 2016

Preliminary results are reported of a long-term program to test models of variable radio sources by direct observations of diameter changes. Although further confirmation is needed, increase in angular diameter attributed to a centimetric component of 3C 279 found in 1966 implies relativistic expansion with α ≳ 2.

In order to sort out events taking place in variable sources it is necessary to observe frequently and at many wavelengths, especially at short wavelengths.
Polarization of Quasars
Authors: Conway R. G.
Published: July 2016

I report here work done at Jodrell Bank by Mr John Gilbert and myself at a wavelength of 49 cm, on the degree of linear polarization, m49. For most sources the polarization is considerably reduced from its short wavelength value. We presume that most of this depolarization is by Faraday rotation, or rather by Faraday dispersion, between different parts of the source.
Radio Observations of Neutral Hydrogen in Four Seyfert Galaxies
Authors: Allen Ronald J. , Darchy Bernard F. , Lauqué Robert
Published: July 2016

The 21-cm wavelength radiation from neutral hydrogen in NGC 1068, NGC 3227, NGC 4051 and NGC 4151 has been observed with the large radio telescope at Nanĉay, France. Since the angular sizes of these galaxies are of the same order as the telescope right ascension beam-width, no information on the angular distribution of the neutral hydrogen was obtained. However the radial velocity distribution of the total hydrogen (the ‘integrated profile’) of the whole galaxy was measured for each of the four galaxies. The hydrogen masses and total masses can be calculated from these profiles using simple models of galaxy shapes and rotation curves.

Optical spectra sometimes show evidence for explosive phenomena and radial outflow of gas in the central regions of Seyfert galaxies. We have examined the integrated radio profiles for indications of large-scale radial motions of neutral hydrogen in two ways. First, for all four galaxies observed, we compare the ratios of hydrogen mass to total mass with the values obtained from other galaxies (not Seyfert) of the same morphological type. Second, for these galaxies where the optical data are available, we compare the estimates of total mass obtained from the optical spectra with the estimates based on the width of the radio profile.

We conclude from these comparisons that the integrated profile of NGC 1068 is unusually broad. One possible interpretation which is qualitatively consistent with the optical data is that an appreciable fraction (about ⅓) of the neutral hydrogen content of NGC 1068 is moving radially outward with velocities of about 200 km s−1 An indication of similar phenomena (although less extreme) is obtained for NGC 4051. The widths of the integrated profiles of NGC 3227 and NGC 4151 do not seem unusual.
Theoretical Considerations of Compact Objects
Authors: Woltjer L.
Published: July 2016

The rotation of massive objects with magnetic fields may provide the highly efficient means of energy conversion required to explain the high luminosity of compact objects. Several variations of the ‘massive rotator’ model are discussed.
The Large-Scale Variations of Quasi-Stellar Objects
Authors: McCrea W. H.
Published: July 2016

The proposition for consideration is:

A QSO is an approximately standard object: it has an approximately standard history consisting mainly of an increase of optical brightness to a very high peak, and a subsequent decline. I suggest that the history has a relevant duration of about 106 yr, and that the total increase of brightness is by a factor about 103, while the mean brightness is of the order of 1% of the peak brightness (so that the peak is rather sharp).
A ‘Single Electron’ Synchrotron Radiation Model and the Quasi-Stellar Objects
Authors: Falla D. F. , Evans A.
Published: July 2016

In this synchrotron radiation model, the essential feature is that the basic form of the theoretical continuum is a characteristic of the energy evolution of a single electron. The model may be applied to sources containing high magnetic field regions where electrons have radiation lifetimes short compared with typical observation times; the electrons are generated in condensations of material which also amplify magnetic fields to values required for the emission of optical synchrotron radiation. A more specialized version of the model can provide a description of the QSOs that is consistent with their cosmological interpretation.
A Matter-Antimatter Model for Quasi-Stellar Objects
Authors: Elvius Aina
Published: July 2016

Observations of quasi-stellar objects and radio galaxies indicate that the total energy radiated from such objects is so large that the most likely source of energy is annihilation.

The demand for symmetry in the universe between ordinary matter and antimatter indicates that there must be equal quantities of the two kinds of matter in every galaxy. From this it seems likely that a galaxy is born as an ambiplasma body, in which separation of matter from antimatter leads to reasonably stable configurations.

The violent events observed in quasi-stellar objects are then interpreted in terms of collisions between stars of opposite kinds of matter. Such collisions are expected to occur frequently in very young galaxies with a high stellar density in the nucleus. Most of the gamma-radiation released in the annihilation will be absorbed in the gases of the colliding bodies, causing strong heating and violent explosions. Strong ionizing radiation and expanding gas clouds will give rise to the observed optical line emission. Expanding clouds of light ambiplasma will emit synchrotron radiation.
Problems Concerning the Extragalactic Distance Scale
Authors: Abell G. O.
Published: July 2016

The use of the brightest members of galaxy clusters as distance indicators is questioned because of a possible correlation between the absolute magnitude of the brightest galaxy and the richness of the cluster. Comparison of the clusters' luminosity functions is considered to be more appropriate. The difference between the two approaches is substantial when a comparison is made between the Coma and Virgo clusters. The value of the Hubble parameter may well be less than 50 km s−1 Mpc−1.
Rapid Evolution of Galactic Nuclei
Authors: Tifft William G.
Published: July 2016

An evolutionary sequence is suggested for Virgo cluster galaxies, in a radial velocity-nuclear magnitude diagram. This evolution, on a time scale of about 108 yr, is discussed in terms of the morphology and radial color variations of the galaxies, nuclear size and radio emission. An area scan and profiles of nuclei, obtained with image dissector equipment, are presented.
The Diameter-Redshift Relation
Authors: Baum W. A.
Published: July 2016

An observational investigation of the angular diameter-redshift relation for galaxies is described, using results from a ‘photographic galaxy synthesizer’. The observations give a value q0 = + 0.3 for the deceleration parameter.
Notes on Cosmology
Authors: Pachner J.
Published: July 2016

The present short notes on cosmology start with two conclusions based on observational data. The first of them is the well-known conclusion that the Universe from the global point of view is at the present epoch of its evolution in a uniform and isotropic expansion. If we accept the very convincing arguments of Bondi (1962) that the geometry of the cosmic space is Riemannian, its properties are described at the present epoch of the cosmic evolution by the well-known Robertson-Walker metric expressing the cosmological principle (Robertson, 1935, 1936; Walker, 1936). The form of the geodesical lines depends on the assumed theory of gravitation. For instance, in the closed Friedman world model they are cycloids with a singularity at the start of the expansion.
The N(S) Relationship at 1400 MHz
Authors: Bridle A. H. , Davis M. M.
Published: July 2016

The number-flux density relation for radio sources selected at 1400 MHz is discussed, the exponent of the counts being given for two flux density ranges. The accuracy of the exponents is limited only by the statistical size of the sample. The completeness of the catalogue is estimated. Results are compared with other flux density measurements.
Selection of Cosmological Models Using QSOs
Authors: Roeder R. C.
Published: July 2016

It is assumed that the QSOs are at cosmological distances as indicated by their emission-line redshifts. It is further assumed, as indicated by present evidence, that none of the 21 QSOs with emission-line redshifts, ze, of 2.0 ± 0.1 (or of the 30 with ze = 2.0 ± 0.2) is screened by an intervening normal galaxy. The simplest conclusion from these data is, then, that the screening probability must be less than 0.08 (or 0.06) at ze = 2.0. This, in turn, restricts allowable cosmological models in the (σ0, q0) diagram by providing lower limits for ß0 as a function of q0. One can also rank cosmological models in order of the probability that there be no screening of the 21 (or 30) objects. In either case the steady state model ranks higher than the general relativity models found by Peach to give the best fit in the (m – z) diagram.
Observations of Large-Scale Anisotropy in the 3 K Background Radiation
Authors: Conklin E. K.
Published: July 2016

Measurements of the background radiation were made at 8000 MHz with a beamwidth of 15 deg. Two antennas were used, arranged such that the equipment recorded the temperature difference between points five hours apart in right ascension and at declination + 32°. Data were taken only at night and at 3800 m altitude, in order to reduce systematic effects as much as possible. Two observing runs six months apart were combined; after subtracting Galactic non-thermal radiation, the remainder shows a significant dipole anisotropy, a possibly significant quadrupole anisotropy, and no detectable variations of smaller angular size: (Table I.)
Galactic and Metagalactic Magnetic Fields
Authors: Brecher K.
Published: July 2016

All of the possible sources of primeval magnetic fields are examined and found to be inadequate to account for the observed galacticB-fields (if the magnetic fields in galaxies are the direct result of the condensation of a magnetized metagalactic medium). Field amplification in dense rotating objects (perhaps neutron stars or galactic nuclei) may be responsible for the bulk of such fields. Most of the (hypothetical) intergalacticB-field then originates in galaxies and is dragged along with the cosmic rays escaping from them. Limits are placed on the value of any present intergalactic magnetic field of either primordial or ‘recent’ origin.
Cometary Observations and Variations in Cometary Brightness
Authors: Vsekhsvyatskij S. K.
Published: July 2016

The cometary observation service is surveyed. Absolute magnitudes and other physical characteristics are given for the comets that appeared during 1965–1970. The general laws of cometary brightness, in particular the secular decrease in brightness, are discussed. Remarks are made about the standardization of cometary photometry.
L'observation des comètes à l'astrographe de l'Observatoire de Nice
Authors: Milet B.
Published: July 2016

The programme of cometary observations at the Nice Observatory is described. Observations are made with the double astrograph by the Trépied-Metcalf method, offset motions of up to half a degree per hour being possible. Five reference stars are measured, and the reductions are made by the least-squares dependence method.
Orbital Characteristics of Comets Passing Through the 1:1 Commensurability with Jupiter
Authors: Rabe E.
Published: July 2016

When, in consequence of a close approach, a comet of the Jupiter group changes its osculating semimajor axis from a > 1 to a < 1 (á = 1 for Jupiter's orbit), or vice versa, then the normal case is that of an abrupt change from one side of Jupiter's orbit to the other one. Under special conditions, however, temporary capture into satellite or ‘Trojan’ status is possible. P/Slaughter-Burnham, the first known comet in temporary 1:1 resonance with Jupiter, sheds some light on the requirements for Trojan captures. In consideration of the recent finding that the Trojan ‘cloud’ around L4 contains probably as many as 700 Trojans brighter than magnitude 20.9, it is suggested that at least some comets of the Jupiter group may have originated among these accumulations around L4 and L5.
The Solution of Problems of Cometary Astronomy on Electronic Computers
Authors: Belyaev N. A.
Published: July 2016

A series of standard programmes has been developed for numerical integration by Cowell's method of the differential equations of motion of minor bodies. A variable step is used, and perturbations by eight major planets and nongravitational effects are taken into consideration. Further programmes have been constructed as part of a general attempt at ITA to produce numerical theories of cometary motion. They include the reduction of observations, the comparison of the observations with theory and the improvement of orbits. The programmes make it possible to calculate (O–C) residuals of up to 2000 observations simultaneously.
The Use of the Electronic Computer for the Urgent Publication of Astronomical Material
Authors: Ivakin V. A.
Published: July 2016

A system is described for processing scientific information with automatic type-setting of tabular text.
A Search for Encke's Comet in Ancient Chinese Records: A Progress Report
Authors: Whipple F. L. , Hamid S. E.
Published: July 2016

The catalog by Ho Peng Yoke lists ancient Chinese observations of 581 transient astronomical objects of which some 300 might conceivably have been P/Encke, between the years − 156 and + 1600. Using the Gauss-Hill method it was possible to establish roughly the plane of the orbit and the direction of perihelion for P/Encke over this interval of time. All but about 40 of the objects could be eliminated by comparing the observed locations with possible locations of P/Encke. Several more could be eliminated on the basis of their calculated magnitudes and general observability. Large uncertainties in the non-Newtonian motion as yet prevent our certain identification of P/Encke among the remaining possibilities.
Linkage of Seven Apparitions of Periodic Comet Faye 1925-1970 and Investigation of the Orbital Evolution During 1660–2060
Authors: Belyaev N. A. , Khanina F. B.
Published: July 2016

Seven apparitions of this comet, from 1925 to 1970, have been linked, with account taken of the perturbations by Venus to Neptune; 202 observations have been represented with mean square error ± 2′.15. The resulting orbit was integrated from 1947 back to 1843 and compared with Möller's results. The result of the comparison after 104 years was found to be very good. The comet's orbital evolution was studied altogether over a period of 400 yr (1660 to 2060). There were nine approaches within 1.5 AU of Jupiter, the comet on one occasion passing through Jupiter's sphere of action. The orbital evolution was free from catastrophic changes, the comet remaining in the Jupiter family throughout the interval. The problem of the comet's discovery was considered.
An Investigation of the Motion of Periodic Comet Borrelly from 1904 to 1967
Authors: Belous L. M.
Published: July 2016

The motion of P/Borrelly has been investigated using all precise published positions and taking into account the perturbations by Venus to Pluto. Nongravitational forces have been found to influence the motion of the comet considerably, formerly as a secular deceleration, more recently as a secular acceleration. By linking the seven apparitions 1904–1960, with allowance for the nongravitational effects, we have obtained a set of elements which represents 802 observations with a mean error of 1′.89.
On the Determination of Planetary Masses
Authors: Herget P.
Published: July 2016

A common method of determining the mass of a planet is to solve for the orbit of some other object several times with different trial values for the mass in question. It is pointed out that a parabola fitted to the values of the sums of the squares of the residuals may be used to obtain, not only the planetary mass, but also its probable error. Marsden's determination of the mass of Saturn from observations of Hidalgo is used as an example.
The Evolution of Cometary Nuclei
Authors: Shul'Man L. M.
Published: July 2016

The evolution of a cometary nucleus depends on the size distribution of the dust content. If all the dust particles are small enough, they will all be thrown off into the coma; the secular decrease in the comet's brightness is due simply to the decrease in the nuclear radius, and the comet eventually disintegrates. On the other hand, if larger grains are present, they will start to form spots of a low-emissivity mineral envelope on the surface of the nucleus; in this case, the decrease in brightness is due to the increase in the area of the screened part of the surface, and the reduction in the nuclear radius is comparatively small. It is shown that after about 90% of the surface has been screened, the rate of screening increases considerably, as smaller particles become trapped between the larger ones; and there will be a corresponding acceleration in the brightness decrease. These nuclei are eventually covered with a solid mineral envelope, and they are transformed into asteroids.
On Nongravitational Effects in two Classes of Models for Cometary Nuclei
Authors: Dobrovol'skij O. V. , Markovich M. Z.
Published: July 2016

Two types of cometary nuclei are considered: a homogeneous icy nucleus and an icy nucleus covered with a dispersive surface layer, 1 cm thick and having poor heat conductivity. The temperature of the evaporating ice surface of a nucleus rotating in a period of 6 hours about an axis perpendicular to the orbital plane was determined by numerical integration of the equation of heat conduction in the first case and of the Stefan problem in the second. For a nucleus of radius 105 cm and mass of 3.8 × 1015 g the reactive force was found to be about 107 dyn in either case, and the secular change in mean motion is of the order of the observed values. For the homogeneous nucleus the dependence of the reactive force on heliocentric distance is obtained.
Determination of the Form of the Oort Cometary Cloud as the Hill Surface in the Galactic Field
Authors: Antonov V. A. , Latyshev I. N.
Published: July 2016

An estimate is made of the maximum range over which the motion of a particle about the Sun and in the galactic field is stable in Hill's sense. An equation fitting the Hill surface is found, with allowance made for the fact that the galactic potential differs from that of a point mass. The volume enclosed by the surface is 3.35 cubic parsecs, the greatest distance from the Sun being 1.42 parsecs, this being along the line to the centre of the Galaxy.
On ‘New’ Comets and the Size of the Cometary Cloud
Authors: Yanovitskaya G. T.
Published: July 2016

By means of the Oort-Schmidt definition of ‘new’ comets, Sekanina's catalogue of original and future orbits, and the 2σ and 3σ rules, we have compiled a list of 33 ‘new’ comets. We draw some conclusions concerning the size of the cometary cloud.
New Estimates of Cometary Disintegration Times and the Implications for Diffusion Theory
Authors: Dobrovol'skij O. V.
Published: July 2016

Numerical methods are used to establish the fraction of solar radiation utilized in the sublimation of ice on the surface of a cometary nucleus. An estimate can then be made of the lifetime of the nucleus. For a nucleus of radius 2 × 105 cm in an orbit of semilatus rectum 0.6 AU the lifetime is 300 revolutions. Comparison with diffusion theory reveals a significant deficiency of the theory in the case of comets with small reciprocal semimajor axes.
The Effect of the Ellipticity of Jupiter's Orbit on the Capture of Comets to Short-Period Orbits
Authors: Everhart E.
Published: July 2016

Single, random, close encounters of long-period comets with Jupiter are studied. In contrast to earlier work, Jupiter's orbit is taken to be elliptical, but this has no effect on the rate of capture into short-period orbits and neither does it influence the distribution of longitudes of perihelion.