bluuebunny/crossref_metadata_2025 huggingface dataset:
The Clump Giants: A Spectroscopic Survey of G and K Giants in Open Clusters
Authors: Pilachowski Catherine A. , Bonsack Walter K.
Published: July 2016

The clump giants in old and middle-aged open clusters provide a sample of stars whose evolutionary state can be clearly identified as core helium burning (Cannon 1970). The evolutionary state of the Ba II stars, on the other hand, is at present undetermined. The enrichment of s-process elements in the atmospheres of these peculiar stars suggests that the stars have at least passed through double shell burning, where the heavy elements may be produced and mixed to the surface. The Ba II stars are, however, too faint to be associated with this phase of stellar evolution; the absolute magnitudes and temperatures are consistent with the core helium burning phase. The barium stars should then occur in the clumps of Population I clusters in similar proportion to their numbers among the field giants.
Measurements of Abundances and Ages of Old Disk Clusters
Authors: Hirshfeld Alan , McClure Robert D. , Twarog Bruce A.
Published: July 2016

The old disk clusters represent a striking contrast to the globular clusters which will be discussed extensively at this meeting in that the disk clusters show few anomalies. This makes a discussion of their abundance measurements of particular interest at this meeting, and may shed some light on the cause of the peculiar behavior of the halo objects. It is also appropriate to discuss the ages of the clusters since the HR diagram is a major tool for obtaining the ages of stars. A complete sequence of stars of one age in a cluster can be fitted to the ZAMS of theoretical models, and accurate abundances averaged over numerous stars in the cluster can be estimated. We will discuss the ages and abundances of 11 disk clusters for which UBV and DDO photometry are available in the literature. This limits the sample to those for which good color-magnitude (C-M) diagrams exist. In addition we present the C-M diagrams of two clusters that we have studied and that are not yet published elsewhere. We will use these clusters to illustrate our procedures.
A Combined Photometric/Spectroscopic Study of RR Lyrae Stars in the Globular Cluster Omega Centauri
Authors: Butler Dennis , Bell Roger A. , Dickens R. J. , Epps Elizabeth
Published: July 2016

Most CM diagrams of well observed galactic globular clusters have giant branch widths which are understandable in terms of realistic estimates of random (and systematic) error associated with data acquisition and reduction. Not Omega Centauri. The scatter in (B-V) color among Omega Centauri giant branch stars is considerably greater than that allowed by observational error, differential reddening, or star-to-star mass and/or helium abundance variation (Demarque and Geisler 1963; Woolley 1966; Dickens and Woolley 1967; Rood 1973; Cannon and Stobie 1973; Cannon and Kontizas 1974; Iben 1974; Norris and Bessell 1975; Hesseret al. 1976; 1977). This problem is an old one, but one which has recently received a flurry of attention. Indeed, our next speakers have investigated possible causal relationships between interior mixing and Omega Centauri giant (or subgiant) color. I see from the program that they intend to discuss such things today, so we shall try to avoid those topics as much as possible.
The Anomalous Giant Branch of ω Centauri
Authors: Evans T. Lloyd
Published: July 2016

The giant branch of ω Cen is much narrower in the I, (V-I) diagram than in the V, (B-V) diagram but at least 24 stars which lie on the red side of the giant branch are radial velocity members (Lloyd Evans 1977), (Lloyd Evans, to be published). Spectra of these stars show, with only one exception, stronger metal lines than stars of similar (V-I) color on the main giant branch (comparable to stars in 47 Tuc), strong CN bands where the stellar temperature allows and strong Ba II 4554 Å. The Ba II star RGO 371 (Dickens and Bell 1976) is a typical member of the group. The Cepheid V29 also shows strong CN bands and strong Ba II. A start has been made on a spectroscopic search for stars on the main giant branch showing these anomalies and the sample of stars with VI photometry is being enlarged. An explanation of the properties of these stars would appear to require both a large primordial metal content and mixing of processed material to the surface.
Luminosities of LMC OB Stars
Authors: Crampton David
Published: July 2016

Our knowledge of the spectra of stars in other galaxies is essentially limited to those which are extremely luminous. In the LMC, slit spectra of ~ 200 stars have been obtained (Feast, Thackeray and Wesselink 1960, Ardeberget al. 1972) down toUsing an objective prism technique, Brunetet al. (1975) have been able to detect 272 OB stars within the LMC. At the fainter limit this survey should include relatively normal 0 and early B dwarfs and giants. The principal aim of the present investigation was to obtain spectra of these stars for comparison with galactic stars and to apply the techniques of MK classification and measurement of Hγ equivalent widths to determine their luminosities and hence a distance modulus to the LMC.
Is it Possible to Derive the Position of a Star in the HR Diagram from Multicolor Photometry?
Authors: Perrin M.N. , de Strobel G. Cayrel
Published: July 2016

In the preceeding paper of this Symposium by Cayrel and Perrin (1978), HR diagrams have been discussed, in which the [Fe/H] ratio and effective temperatures are derived from model atmosphere analyses and absolute bolometric magnitude from apparent visual magnitude, parallax and bolometric correction. The use of parallaxes imposes a very severe restriction on the number of objects, as parallaxes of at least 0″.050 are needed to have an absolute magnitude good to ±0m.4.
On Magnetic Mixing and Rotation in Stellar Evolution
Authors: Gross Peter G.
Published: July 2016

In this paper some thoughts and problems are presented from the viewpoint that the evolution of stars may play a key role in generating magnetic fields which, in turn, may affect the mixing of nuclearly processed elements from the stellar interior to the surface. The relevant parameter is stellar rotation which, upon interaction with convective turbulence driven by thermal instabilities, leads to the generation of magnetic fields. A possible connection to Bidelman's hypothesis on the evolutionary status of Ap stars is also discussed in the context of a post-core-helium-flash hypothesis.
Survey of Some Recent Stellar-Evolution Calculations
Authors: Sweigart Allen V.
Published: July 2016

A basic objective of stellar-evolution theory is to provide detailed quantitative information on the evolutionary characteristics of stars with different compositions and masses. For the evolutionary phases from the zero-age main sequence (ZAMS) through core-helium burning the important physical processes are sufficiently well understood to justify a systematic investigation, and, indeed, extensive grids of evolutionary sequences have been constructed for these phases by many researchers. However, several difficulties are sometimes encountered when using the available calculations. For example, differences in numerical techniques and physical assumptions can give rise to systematic differences among the results of various investigations. Furthermore, the available calculations do not always explore the full ranges of the input parameters, and in some cases they neglect physical effects that are now believed to be important.
Evolution of Massive Stars: When Does an of Star Become a WR Star?
Authors: Conti Peter S.
Published: July 2016

Detailed spectroscopic work has begun for several stars that have been classified WN 7. All show absorption lines in the upper Balmer series and in ionized helium. The absolute magnitudes, established from cluster membership, are relatively brighter than those of most other WR stars. In this paper the outflow velocity near the stellar photosphere is shown to be similar to that in Of stars. These WN 7 stars show somewhat larger emission line widths and probably have less hydrogen in their envelopes, but otherwise have similar luminosities and temperatures as Of stars.
Sphericity Effects of Extended Atmospheres of Late-Type Giants in the HR Diagram
Authors: Kodaira Keiichi
Published: July 2016

In the late phases of stellar evolution, evolutionary tracks of stars with different masses come together along the Hayashi line in the HR diagram. The theoretical HR diagram (log L, log Teff) is accordingly partially degenerate in the domain of late-type giants and supergiants, with respect to the third parameter, the stellar mass M. The stellar radius, R, being determined by log L and log Teff, the mass determines the surface gravity log g at the radius R. These parameters enable us to transform a point in the theoretical HR diagram to the corresponding point in the empirical HR diagram MV, (R-I) or spectral type. This transformation is conventionally carried out within the framework of the plane-parallel approximation in stellar atmospheres, and the parameters for the abscissa of the empirical HR diagram are dependant upon Teffand log g alone, irrespective of the mass itself. In this case, the parameter M indirectly affects the observable quantities through log g, but the effects of a variation by Δlog g=±0.5, corresponding to Δlog M=±0.5, are almost insignificant (cf. Tsuji 1976). The transformation between the theoretical and the empirical HR diagram is, therefore, almost one-to-one, within the framework of the plane-parallel approximation. Late-type giants and supergiants, however, have moderately extended atmospheres in general (cf. Schmid-Burgk and Scholz 1975), and their photometric colors and spectra are expected to be influenced by the sphericity of the atmospheric structure. Consequently, in comparing empirical HR diagrams with theoretical ones, it is important to know how atmospheric sphericity affects the transformation in the degenerate domains of the theoretical diagram.
ON G.P. Kuiper's Work on the Stars of Large Proper Motion
Authors: Bidelman William P.
Published: July 2016

The writer is preparing for publication a complete listing of the late G.P. Kuiper's spectral classifications of stars of large proper motion north of δ=−50°. This work, resulting from his observations made at the Yerkes and McDonald Observatories some 35 years ago, has been only partially published; it is estimated that useful unpublished classifications exist for the order of 1000 stars. This paper discusses the background of his program and the procedures to be followed in making these data generally available.
The Main Sequence at G2 V
Authors: Hardorp Johannes
Published: July 2016

About 3/4 of the sky were searched spectroscopically for stars whose ultraviolet spectra (3640–4100 Å) match that of the Sun, at 20 Å resolution. Down to the limit of the BSC, only two were found: HR 7504 and HR 2290. No G2 V star matches the Sun. Stars that do match have (B-V) = 0m.66. The search has a bearing on effective temperatures of G dwarfs and on metal-abundances relative to the Sun.
Luminosity Calibration of Late-Type Stars by Statistical Parallax using AGK3 Proper Motions
Authors: Ishida Keiichi , Mikami Takao
Published: July 2016

The luminosity of individual late-type stars is estimated mainly by spectral features in the MK spectral classification system or by means of the Wilson-Bappu effect. The MK spectral type is given for spectra with a dispersion of about 100 Å mm−1which is within the reach of some Schmidt telescopes with objective prisms. On the other hand, the Wilson-Bappu effect is measured from spectra with a dispersion of about 10 Å mm−1, obtained by coudé spectrographs. In either case the luminosities must be calibrated by knowledge of apparent magnitudes and distances for some stars.
The Strömgren Four-Color System and the Log Teff, Log G Diagram
Authors: Relyea Lawrence J. , Davis Philip A.G.
Published: July 2016

Strömgren (1966) set up the four-color system of photometry as a means of studying early-type stars in the spectral range 0 through F. In this spectral range one of the important measures that can be made of a stellar spectrum is the magnitude of the Balmer jump. For stars of a given (b-y) color the discontinuity is very large for stars of high luminosity and small for low luminosity stars. For very hot stars (0 and B stars) this luminosity effect becomes too small to be used as a luminosity indicator, but because of this insensitivity to luminosity changes the magnitude of the Balmer discontinuity becomes a temperature indicator (see Philip and Newell 1974 and Davis and Shobbrook 1977). Photoelectric measures of the strength of the Hßline can be used in a similar, but reverse, manner. For the B and O stars the index is a measure of luminosity; for late A and F stars the index is a good temperature index. In the spectral range A0-A3 both the Balmer jump and the Beta index are functions of temperature and luminosity. For a bibliography of the many uses of Strömgren four-color and Hßphotometry see the paper prepared by Philip and Perry (1977).
The automatic detection of faint quasars from CFHT grens plates
Authors: Keable C.J. , Clowes R.G.
Published: July 2016

The automatic quasar detection system (AQD, see Clowes, 1984) has been used to successfully select quasars from prism plates taken by the United Kingdom Schmidt Telescope. Surveys compiled using this technique have a magnitude limit of B-19.5. We present work here which extends the possible survey limit to B-21. This is done by putting plates taken with the Canada-France-Hawaii Telescope's grens (see Richardson, 1984, for a description) through the AQD measuring system. We will follow this work with a comparable photometric survey of the same field.
Variability in the optical continuum of Type 1 Seyfert nuclei
Authors: de Ruiter H.R. , Lub J.
Published: July 2016

In 1979 we started a monitoring program of Seyfert galaxies, using various telescopes at ESO (La Silla, Chile). At present this program is still continuing, but here we discuss only the photometric data obtained in the period 1979–1982.
VLA observations of rapid variability in OJ287
Authors: Roberts David H. , Dreher John W. , Lehår Joseph
Published: July 2016

Using the VLA at 6 cm, we have detected non-periodic variations in the powerful BL Lacertae object OJ287 on timescales between minutes and hours at levels of the order of one percent. Brightness temperatures inferred from causality arguments range from 1016 to 1020 K. No periodic component was found to a limit of 0.1%.
Radio Emission From Optically Selected Quasars
Authors: Kellermann K. , Sramek R. , Shaffer D. , Green R. , Schmidt M.
Published: July 2016

Shortly after their discovery, it was realized that most quasars are not found in radio source catalogues, and a number of searches were initiated to try to detect weak radio emission from “optically selected quasars.”
A dependence between optical and radio luminosities of quasars after all?
Authors: Machalski Jerzy
Published: July 2016

It is still uncertain whether optical and radio emission mechanisms in AGNs are coupled or not, and how? New observational data give more light on this subject.
Radio and optical observations of “optically quiet quasars”
Authors: Cotton W. D. , Owen F. N. , Mahoney M. J.
Published: July 2016

In recent years a number of very steep spectrum, compact radio sources have been discovered (e.g. Cotton 1983, Cotton and Owen 1985, Ulvestad 1985) which have no optical counterpart to the limit of the Palomar Sky Survey. VLBI observations of a number of these have confirmed the very compact (<10 mas) nature of several of these sources. Analysis of the available data in terms of the standard synchrotron modal suggest that they contain very weak magnetic fields, large particle densities and may emit detectable infrared and optical emission by inverse Campton scattering in the compact radio source (Cotton 1983). This paper will report on an analysis including new VLBI observations, infrared and optical imaging at KPNO and low frequency radio observations at CLRO of a number of these objects.
A CCD survey of BL Lac objects
Authors: Kuhr Helmut , Fried Josef
Published: July 2016

A long term project was started at the Max-Planck-Institut fur Astronomie, Heidelberg, to study a complete sample of 46 northern and southern BL Lac objects with flux densities exceeding 1 Jy at 5 GHz using optical spectroscopy, optical polarimetry, and direct deep CCD imaging.
Environnement du noyau de 3C 120
Authors: Wlérick G. , Soubeyran A. , Servan B. , Renard L. , Horville D. , Bijaoui A. , Lelièvre G. , Bouchet P.
Published: July 2016

The region surrounding the nucleus of 3C 120 has been recorded on electronographic plates, in U, B, V and V' colours. It has been possible to substract the contributions of the bright nucleus and the galaxy. Faint condensations appear. Their colours show that they are probably not emitting synchrotron radiation. The brightest condensation A is located 4” West of the nucleus. It does not coïncide exactly with the knot of the radio jet and is very slightly displaced toward the North. It is probably of the same nature as Minkowski's Object: burst of star formation triggered by the collision of the jet with relatively dense extranuclear gas.
Superluminal motion in the quasar 3C 279
Authors: Unwin S. C.
Published: July 2016

We present the results of a program of monitoring structure changes in the radio core of the quasar 3C 279 (z = 0.538) using VLBI. In all, nine hybrid maps have been made from observations at frequencies of 5, 11, and 22 GHz, during the period 1981–1985. The VLBI structure shows many similarities with other ‘superluminal’ radio sources, e.g. 3C 273 (Unwin et al. 1985), such as alignment with a kiloparsec-scale jet, a one-sided spectral distribution, and superluminal motion. The proper motion measured from our observations is v/c ≈ 2, only one quarter of the previously published rate.
The nuclear jets in 3C309.1 & 3C380
Authors: Wilkinson P.N. , Kus A.J. , Pearson T.J. , Readhead A.C.S. , Cornwell T.J.
Published: July 2016

8 station VLBI maps of the nuclear jets in 3C309.1 and 3C380 reveal complex, bent, structures which seem hard to reconcile with the concept of ballistic outflow. Together with the observation of “flaring” in the MERLIN/EVN map of the 3C309.1 jet the maps point strongly to the jets being confined fluid flows.
Absorption lines and the radio structure of quasars
Authors: Swarup G. , Saikia D.J. , Beltrametti M. , Sinha R.P. , Salter C.J.
Published: July 2016

We have investigated a possible relationship between the radio structure of quasars and their absorption line systems with velocities, V, in the range 3000–18000 km s−1 and find a marginal trend for such quasars to have compact radio structures (Swarup et al. 1986).
Redshift distributions of steep and flat-spectrum radio quasars and relativistic beaming
Authors: Kapahi V.K. , Kulkarni V.K.
Published: July 2016

Redshift distributions of almost complete samples of steep as well as flat-spectrum radio quasars are investigated. It is found that flat-spectrum (core-dominated) quasars contain a higher fraction of high redshifts (z ≳ 1.4) compared to steep-spectrum ones. The difference can be understood in the ‘unified scheme’ in which the two types of quasars differ only in the orientation of their jet axes with respect to the observer.
Radio jet and lobe of 3C273
Authors: Davis R.J.
Published: July 2016

The ‘superluminal’ motion observed in the cores of radio sources such as 3C273 is now accepted as evidence of relativistic motion within a few parsecs of the centre, but it is less clear whether such speeds persist out to kiloparsec scales. The one-sidedness of such sources is often cited as evidence of relativistic Doppler beaming, but could equally be intrinsic. New MERLIN maps of 3C273 at 151 MHz and 408 MHz have been made with dynamic range of 4.103:1 and 104:1 respectively. These show that (i) there is an extended region or lobe to the south of the main jet; (ii) the radio emission of the jet is continuous from the core to beyond the limit of the optical jet; (iii) no counter-component can be found in the opposite direction to the jet. The ridge-line of the jet shows a ‘wiggle’, the wavelength of which decreases by a factor of 6 along its length. This is interpreted as a deceleration of the bulk flow along the jet.
The diverse soft X-ray slopes of QSOs
Authors: Wilkes Belinda , Elvis Martin
Published: July 2016

We present Einstein spectra for 30 QSOs which indicate a large diversity in their soft x-ray slopes, unlike the uniform slopes found for AGN higher x-ray energies. The slope is related to radio properties, x-ray luminosity or possibly redshift, but we cannot definitively distinguish these possibilities.
X-ray intensity variations in BL Lac sources H2155-304 and PKS 0548-322
Authors: Agrawal P.C. , Singh K.P. , Riegler G.R.
Published: July 2016

The X-ray Observations of two BL Lac Objects H2155-304 and PKS 0548-322 made with HRI and MPC on the Einstein Observatory show intensity variations on time scale of hours in both the sources. X-ray spectra of the two BL Lacs are derived. Limits on the mass of the accreting compact objects are obtained from time scale and magnitude of variations. Implications of the results are briefly discussed.
Theoretical Studies of the Line Emission Spectrum
Authors: Collin-Souffrin S.
Published: July 2016

Our knowledge of the physical conditions and of the structure of the broad line emissive region -the BLR- is reviewed. First we derive the model independent constraints on the different zones emitting the broad lines. Then we discuss photoionized models. In a first step the BLR is assumed to be made only of one type of cloud emitting all the broad lines. We show that this model is unable to explain the observed spectrum. We thus assume that the high and low ionization lines are emitted by different clouds, still photoionized. This assumption is also in contradiction with the observations and we are led to the idea of a large variety of emitting clouds. Finally the hypothesis of a purely radiative heating mechanism should also be questioned.
A detailed study of the CIV 1550 line profile and adjacent spectral features in NGC 4151 from 1978 up to 1983
Authors: Clavel J. , Altamore A. , Boksenberg A. , Bromage G.E. , Elvius A. , Pelat D. , Perola C. , Penston M.V. , Snijders M.A.J. , Ulrich M.H.
Published: July 2016

Fitting technics are applied to study the variations of the 1550 line profile and adjacent features in the IUE spectrum of the Seyfert galaxy NGC 4151, from 1978 up to 1983. New important results are found concerning the kinematics and physics of the emission line gas at a few light-days from the continuum source.
A shock model for quasars and active galactic nuclei
Authors: Pérez-Fournon I. , Biermann P.
Published: July 2016

First order Fermi acceleration is an efficient mechanism to produce relativistic particles in strong astrophysical shocks. We have developed a model using this theory to explain the non-thermal emission from non-relativistic jets in Quasars and AGNs. Fluid dynamical simulations of cosmic jets predict shock formation in them at quasi-periodic intervals. This is also suggested by observations of jets. We identify the shocks as the sites of reacceleration of the energetic particles required to explain the non-thermal emission of the jets. In order to facilitate the comparison with observations, we have done numerical simulations of the expected observational properties at high and low spatial resolution.
Models for extragalactic radio sources
Authors: Kundt W.
Published: July 2016

Doubt is cast on the reality of the following four assumptions commonly made in the treatment of extragalactic radio sources: (1) The central engine is a black hole; (2) Electrons can be accelerated in situ in the knots and heads of the jets, to large Lorentz factors γ ≥ 102, with an efficiency exceeding 30%; (3) The (non-thermal) radiation emitted by the beam fluid is isotropic in some (comoving) Lorentz frame; and (4) The flow velocity in the jets of SS 433 is v = 0.26 c.
A novel interpretation of the cosmic conspiracy in AGNs
Authors: Coleman Colin S.
Published: July 2016

The flat radio spectra of core dominated AGNs are often attributed to a superposition of optically thick synchrotron components. This is known as the cosmic conspirac A radio index pr ∼0 is not a natural consequence of this model, and an alternative model proposed here interprets the source components as regions in which relativistic electrons stream along a magnetic field. Stream collimation is determined by plasma instabilities, and components are assumed to be optically thin, with cyclotron turnover at low frequencies. An appealing feature of this model is that radio photon index depends only upon electron energy distribution, which may be obtained from the photon index above the turnover frequency. An energy power-law with index s≥3 is typical for these sources, and implies a flat radio spectrum with pr = (4/3)-p ∼0.
Clustering, Isotropy, and Redshift Cutoff
Authors: Osmer Patrick S.
Published: July 2016

The topics of clustering, isotropy, and redshift cutoff are in reality just different aspects of the problem of the three-dimensional distribution of quasars, assuming, of course that the redshifts are cosmological and therefore an indication of radial distance. The distribution in redshift has additional interest because of the substantial lookback times involved, up to four fifths of the age of the universe. The radial variation of quasar density between redshift zero and two, and the attendant questions of density and luminosity evolution, are discussed elsewhere in this symposium by Green and shall not be treated here. Rather we shall concern ourselves with the behavior at redshifts larger than two and the specific question of a steep decline of quasar density at redshifts near three. For simplicity we may characterize the problem as one of studying either the formation of quasars as we normally see them in a cosmologically short time or of the properties of the universe and its optical depth, should intergalactic absorption contribute significantly to blocking our view at redshift three. Of course other hypotheses are also possible.
Determination of the large-scale and super-large-scale structure by means of the space distribution of quasars
Authors: Zhou Y.Y. , Fang D.P. , Deng Z.G. , He X.T.
Published: July 2016

It is very important to study the large-scale structure by means of the space distribution of quasars. Using this method, one may search for the more distant superclusters and explore the super-large-scale structure, i.e., the existence of super-superclusters. The answer to the problem would be of great interest. It is related to the question about the transition of the clustering of galaxies on about 100 Mpc to the uniformity of the universe. Recently Oort et al and de Ruiter et al suggested that the quasars are located in superclusters. So we soppose that analysing the space distribution of quasars might give us some information about the super-large-scale structure of the universe. But up to the present the study of the clustering of quasars has not obtained universally accepted conclusions; in fact, some of them, including grouping and clustering (Arp; Chu and Zhu), no clustering (Chu and Zhu; Osmer; Webster), clustering for z < 2 and no clustering for z > 2 (Fang et al) and stringing (Deng et al), are contradictory.
Cosmological implication of the emission line redshift distribution of quasars
Authors: Zhou Y.Y. , Gao Y. , Deng Z.G. , Dai H.J.
Published: July 2016

The peaks and dips in the quasar redshift distribution seem to be incompatible with the cosmological principle. This lays the cosmological redshift hypothesis under suspicion and censure, and has been considered by some investigators as a manifestation of the intrinsic nature of quasar's redshift. So it is worthwhile studying whether the redshift distribution of quasars could be explained in the framework of cosmological redshift. As we know, this distribution is affected not only by the possible physical origin of redshift but also by the selection effects in the observations (Zhou, Deng, Zhou 1983). From this we have the redshift distribution function
f(z) = P(z)R(z),
where P(z) is the real distribution function which depends on the evolutionary properties of quasars and the space-time structure of the Universe, and R(z) is the factor caused by the selection effect in the line identification.
Quasars in the Virgo cluster region
Authors: He X.-T. , Smith M.G. , Cannon R.D. , Peacock J.A. , Oke J.B. , Impey C.D.
Published: July 2016

The region of the Virgo cluster is the subject of an intensive quasar search, since quasars mill provide valuable probes of absorption due to galaxy haloes or the intracluster medium. It is also interesting to test the quasar-galaxy association in such a region of the nearest major cluster of galaxies. More than 200 quasar candidates were found in the Virgo cluster region using both slitless technique and machine search, 32 of them have been confirmed as quasars.
Observations of close pairs of faint blue objects: towards mirage or reality
Authors: Reboul H. , Fringant A.M. , Vanderriest C.
Published: July 2016

We present the results of a prelim minary observational run of the FRV sample (Fringant et al, 1983) of close pairs of UVX objects at high galactic latitude. The extragalactic physical pairs are ∼30% and most of them do appear as “interactivating” AGNs. The method seems equally adapted to find new gravitational mirages as well as really double QSOs.
A search for QSOs in the fields of nearby galaxies
Authors: Pocock A S , Penston M V , Pettini M , Blades J C
Published: July 2016

The extent and physical conditions of diffuse gas in the outer regions of galaxies are currently the subject of considerable interest. A very sensitive way to probe the gas is by observing the absorption lines it produces in the spectra of background objects. However, a detailed investigation of the interstellar medium associated with external galaxies requires the availability, in the field of the galaxy under study, of several probes (QSOs, Active Galactic Nuclei, supernovae) which are: (a) sufficiently bright for high-resolution spectroscopy (B ≤ 17.5) and, (b) located over a range of projected distances from the galaxy, say from 10 to 200 kpc. As there are very few QSOs in the literature which meet these requirements, we have been carrying out a search of nearby galaxy fields for the specific purpose of finding a number of suitable background probes.
On the Origin of the Light Elements (D, 3He, 4He and 7Li)
Authors: Audouze Jean
Published: July 2016

The abundances of the very light elements (D, 3He, 4He and 7Li) constitute indeed one of the most powerful constraints in cosmology: they are known to fix very interesting limits on the baryonic density of the Universe and on the maximum number of neutrino (lepton) families in the frame of the simplest canonical models. Given the importance of these predictions, these models should be analysed very cautiously at the light of recent developments in the observations of these elements. In order to make the simplest models consistent with the observations, it is argued that a thorough destruction of D should occur during the galactic evolution. Moreover this review deals also with some models invoking the possible existence of massive unstable neutrinos, gravitinos or photinos which would decay into high energy photons or of quark nuggets which could be created during the quark-hadron phase transitions. Such models have been designed in an attempt to overcome the limitation on the Universe density coming from these abundance determinations. Although the simple canonical models are especially attractive such models cannot be disregarded.
Primordial Nucleosynthesis of 7Li
Authors: Duncan Douglas K. , Hobbs L. M.
Published: July 2016

We have observed 23 halo stars with space velocities and metallicities [Fe/H] ≤ −0.6. Twelve of these 23 show the more extreme properties and [Fe/H] ≤ −1.4 and should therefore constitute an especially old, homogeneous subgroup. The principal results for these 12 extreme halo stars and 5 similar stars observed in previous studies are that (1) a single, well defined relation, previously discovered and discussed by Spite and Spite, exists without exception between the atmospheric Li/H ratio and Te, and (2) at Te ≥ 5600 K the average lithium abundance is  = 1.2 ± 0.3 × 10−10. The latter value constitutes a lower limit on the 7Li fraction produced in primordial nucleosynthesis and thereby significantly constrains the cosmic ratio of baryons to photons.
Local Calibrators and H0: The Distance to M31 Using RR Lyrae Stars
Authors: Pritchet C.J.
Published: July 2016

We have used the CFH 3.6 m telescope in excellent seeing to observe RR Lyrae variables in a halo field in M31. From 32 variables found, we obtain (m - M)0 = 24.34 ± 0.15 for M31.
Estimates of Ω Based on Motions within the Local Supercluster
Authors: Tully R. Brent
Published: July 2016

Three ways to estimate Ω from the motions of nearby galaxies are reviewed: (i) comparisons can be made between observed local streaming motions and observed density fluctuations, (ii) a timing argument can give a value of f(Ω) = to Ho, and (iii) the motions in groups provide solid evidence regarding the amount of matter that is distributed like galaxies on a scale of 0.5 Mpc. In each case, the evidence suggests the Universe is open, but only by a factor of 3–5 and, given the uncertainties, a closed Universe definitely is not precluded.
Radio Bending at High Redshifts - A New Probe of Protogalaxies?
Authors: Miley G. K.
Published: July 2016

Evidence is presented that radio sources are more bent at larger redshifts. This effect is interpreted as due to interaction of the radio source with an ambient circumgalactic medium which must then have been clumpier at early epochs. It is suggested that the increased clumpiness could be associated with the late stages of galaxy formation and possibly also with CIV absorption line systems.
Topology of the Universe
Authors: Fang L. Z. , Mo H. J.
Published: July 2016

Topology of the universe is the remains of quantum cosmology. The theoretical and observational aspects for the topology of the universe are discussed to show that the significances of topology of the universe in present observations can shed some light on the properties of the universe in the quantum cosmological era.
Observations Requiring a Non-Standard Approach
Authors: Arp Halton
Published: July 2016

Extragalactic astronomy rests on the assumption that red-shifts are always equal to velocities and that large velocities are unambiguous distance indicators. There are now many observations which disprove this fundamental assumption. We here review the evidence which has been accumulating for 20 years with particular emphasis on the most recent developments.
Luminosity Segregation in Distant Galaxy Clusters
Authors: Mathez Guy , fèvre Olivier Le , Mellier Yannick , Soucail Genevieve , Mazure Alain
Published: July 2016

Angular separation-magnitude plots drawn from deep photometry of galaxies in distant clusters show evidence for luminosity segregation which cannot be accounted for by field contamination. This segregation, interpreted in terms of dynamical friction, allows one to determine (M/L)g, the mass-to-light ratio of galaxies from their velocity dispersion. In A370 (z=0.37) more than 30 velocities have been measured by multi-aperture spectroscopy, leading to (M/L)g ∼70. Values greater than 100 are found in 5 other distant clusters by deriving the velocity dispersion from the richness. The luminosity segregation, observed even inside each of the clumps of 3C299, could result either from dynamical friction inside the clumps or from some early environmental influence.
A Comment on the Seyfert Environment
Authors: Zhen-long Zou , Jian-shen Chen
Published: July 2016

The study on the Seyfert environment has been of considerable interest lately, since it is believed that the tidal force of a close companian may drive gas into the inner region and either fuel nuclear activity directly or lead to starbursts (Toomre et al., 1972, Byrd, 1987). Many authors noticed an excess of Seyfert among close pairs of galaxies (Adams, 1977, Kennicutt et al., 1984, Keel et al., 1984, Dahari, 1984, 1985 a, b). In a recent paper of ours (Chen and Zou, 1986), a neighborhood statistical study has been done for the galaxies in CfA sample (Huchra et al., 1983), and it is found that the fraction of Seyferts is 3 times higher than the average one, if the distances between them and its nearest neighbors are less than 20 kpc. The result would strengthen the opinion that the existance of close companian is a favourable environment to trigger Seyfert activities.
X-Ray Surveys as Tools to Investigate the Cosmological Evolution of Quasars, BL Lac Objects and Clusters of Galaxies
Authors: Gioia Isabella M. , Maccacaro Tommaso , Wolter Anna
Published: July 2016

We present a progress report on a major extension of the Einstein Observatory Medium Sensitivity Survey (MSS). The basic properties of the extragalactic sources identified with Active Galactic Nuclei (AGN) and clusters of galaxies are discussed. Results from previous work are briefly summarized.
Log N - Log S Slope Determination in Imaging X-Ray Astronomy
Authors: Maccacaro Tommaso , Romaine Suzanne , Schmitt Jurgen H.M.M.
Published: July 2016

We briefly discuss the problem of estimating the slope of the number-counts relations for the specific case of imaging X-ray surveys. Results have been obtained from extensive simulations of Einstein Observatory imaging X-ray data. We conclude that the bias which affects the X-ray number-counts slope determination is much smaller than that which affects the radio number-counts slope.
The EXOSAT High Galactic Latitude Survey
Authors: Giommi P. , Tagliaferri G.
Published: July 2016

We have performed a survey of ∼570 square degrees of high galactic latitude sky using a large number of EXOSAT X-ray images. 130 serendipitous sources were detected and ∼60% of them have been identified with catalogued objects. The large majority of the remaining sources have faint optical counterparts on POSS or ESO plates and are expected to be extragalactic. The comparison of our results with those of the Einstein Medium Sensitivity Survey and an analysis of the correlation between the spatial distribution of EXOSAT serendipitous sources and the amount of galactic Hydrogen column density indicate that the average spectral index of extragalactic X-ray sources is steeper than the canonical AGN slope.
Cosmic Distribution of Optically Selected Quasars
Authors: Schmidt Maarten
Published: July 2016

Counts of optically selected quasars as a function of magnitude and redshift show the effects of strong evolution. If quasars have relatively short life times, then the observed numbers at a given redshift are mostly determined by their birth rate and mean luminosity over their lifetime. In this case the evolution of the luminosity function can be described by density evolution, where the rate of evolution may depend on luminosity and other properties. On the other hand, if all quasars were formed at large redshift and have been decaying in luminosity since that time, then the evolution of the luminosity function is best described in terms of luminosity evolution. We discuss some of the consequences of luminosity evolution for the mass of quasars and for the X-ray background.

We explore the observational aspects of the redshift cutoff of quasars. The situation is complicated by the unavoidable bias in slitless surveys against weak-line objects. Since quasar emission lines show a wide range of equivalent widths, a spectral survey will be characterized by a distribution of limiting continuum magnitudes rather than by a single value. The decline in the space density of quasars at large redshift may depend on luminosity, and may also have structure, such as a steep drop, but not a total cutoff, in density at a redshift near 3.
Spatial Distribution of Quasars
Authors: Chu Yaoquan , Fang LiZhi
Published: July 2016

The distribution of quasars has become one of the most interesting problems in observational cosmology. This is due mainly to the development of theory of the formation of large scale structure in the universe. In recent years, several scenarios of clustering have been proposed. In the adiabatic case, the clustering process is from larger scales to smaller ones, i.e., the first systems to form out would be on the scale of superclusters, then these systems fragment to form smaller scale systems such as galaxies. In the isothermal case, the clustering is from smaller scales to larger ones, namely, galaxies condense out at first and larger scale systems, such as clusters and superclusters, then form later via hierachical build-up processes. In the universe contain two components, the scenario of clustering might be different from both standard adiabatic and isothermal cases(1). According to this new scenario, there should be two kinds of small scale objects, one is formed due to fragment of larger scale systems, another is formed before large scale systems form.
On Cosmological Evolution of Quasars
Authors: Machalski Jerzy
Published: July 2016

Hereafter the term “quasar” is applied to both optically selected (and/or spectroscopically confirmed) UVX objects, and to radio-detected objects of that kind. A recent attempt to model number-counts of radio-selected QSOs (Condon, private communication) has revealed that the counts cannot be modelled by simply translating the general radio luminosity function (RLF) leaving the cosmological evolution unchanged. While it may be true that the radio sources in QSOs evolve in the same way as do all radio sources (i.e. translation function), the radio sources are probably not always in QSOs. In particular, it may be that increasing the luminosity (especially the core luminosity) of a radio source increases the probability that it is in a QSO. If that is true, a radio detection rate of optical QSOs should be strongly dependent on the optical (core) luminosity, i.e. on the absolute magnitude.
The Space Distribution of Faint CFHT Quasars
Authors: Crampton D. , Cowley A.P. , Hartwick F.D.A.
Published: July 2016

The space distribution of quasars discovered in our CFHT blue grens survey is discussed in detail. Redshifts for about 200 of the quasar candidates show that the sample is relatively complete for 0.2 < z < 3.4 and m < 20.5. Two-thirds of the quasars have z < 1.8 and only 5% have z > 2.5, indicating that high redshift quasars are rare. The surface density of quasars brighter than m = 20.5 is 30 deg−2. Seven quasars with z = 1.165 ± 0.007 discovered in one of the fields have typical separations of ≈20 Mpc and may belong to a very large structure. Statistical tests on our data indicate that clustering among quasars is not common, however. The luminosity dependent density evolution models proposed by Schmidt and Green (1983) combined with a redshift cutoff at high redshift are consistent with our data and that of Schmidt and Green (1983), Marshall et al. (1984), Koo, Kron and Cudworth (1986), and Schmidt, Schneider and Gunn (1986). The model indicates that there was a broad maximum in the comoving density of quasars near z = 1.7. The results will be reported in detail in the March 1987 issue of The Astrophysical Journal.
The Evolution of Quasars Selected by Slitless Technique
Authors: Deng Z. G. , Zhou Y. Y. , Liu Y. Z.
Published: July 2016

After taking account of the selection effects in the identification of emission lines and choosing the sample within a narrow range of absolute magnitude, we can investigate the evolutionary function of quasars from their redshift distribution. From data given by slitless surveys with limiting apparent magnitude 19.5, we find that the evolutionary function takes form of ρ = ρo(1+z)6.5±1. The analysis has also showed that the observational redshift distribution of quasars is compatible with cosmological principle.
Axions in the Universe
Authors: Tsuruta S. , Nomoto K.
Published: July 2016

The observational evidence for the presence of dark matter is now generally accepted, with no lack of possible candidates (see e.g. Dekel, Einasto, and Rees 1986). The proposed candidates are devided into two groups, baryonic and non-baryonic. The latter is further devided to hot and cold dark matter. For the cold dark matter, among the first to be proposed is the axion. In this paper we shall not dwell on numerous cold dark matter candidates offered by particle physicists, for there are review articles on the subject (see e.g. Turner 1986, Primack 1986). The main purpose of the present report is to suggest that neutron star cooling theory and future space satellite programs (e.g. AXAF, XAO, LXAO) have a potential for offering the best astrophysical constraint on the axion mass and hence, giving valuable insight to some cosmological problems.
3C324: A Probable New Gravitational Lens
Authors: Hammer F. , Le fèvre O. , Nottale L.
Published: July 2016

3C324, a giant radiogalaxy at z = 1.206 has been suspected by us to be a gravitational lens: in a previous work, we have identified an additional line system at z = 0.845 in its spectrum. We present here new observations of 3C324 at C.F.H.T. in R broad band imaging and in adequate filters; they strongly suggest that 3C324 is the first example of a multiply imaged radiogalaxy. The 3C324 case is also a fair confirmation that gravitational lensing may well explain the overluminosity of distant radiogalaxies.
Astrophysical Applications of Gravitational Micro-Lensing
Authors: Kayser R. , Refsdal S. , Stabell R. , Grieger B.
Published: July 2016

Gravitational micro-lensing due to stars in the deflecting galaxy influences the brightness and the spectra of the macro-images. Thus differences in the spectra of different macro-images are not automatically an argument against gravitational lensing. Furthermore changes in the spectra due to micro-lensing may give informations on the quasar structure. From high amplification events the brightness profile of the source may be obtained. The time scale of the high amplification event is proportional to the source radius and inverse proportional to the transversal velocity. Due to the large brightness gradient by a high amplification event, a “parallax-effect” occurs, from which the transversal velocity may be obtained, and thereby the source radius (R=Δ t · VT). We roughly estimate 0.3 high amplication events per year for all gravitationally lensed quasars. Frequent monitoring should be carried out in order to predict high amplification events as early as possible.
Absorption Lines in QSOs
Authors: Chen Jian-Sheng
Published: July 2016

A comparison between three types of intervening absorption line systems: the Lyα forest, the Lyα damped systems and the narrow metal line systems has been done for the observational properties including the frequency of the systems, the equivalent width distribution, the two point correlation function, the metal abundances, and the dN/dz vs. z behavior.
Clustering of Quasars from the ROE/ESO Large-Scale AQD Survey for Quasars
Authors: Clowes Roger G. , Iovino Angela , Shaver Peter
Published: July 2016

The new ROE/ESO large-scale AQD survey for quasars forms a connected area of ∼ 200 deg2 near the south galactic pole, and has resulted in the discovery of a total number of quasar candidates that is comparable to the number previously published from all other sources (see the poster paper by Iovino, Clowes & Shaver at this conference). In this paper we describe the first results of a three-dimensional self-clustering analysis of ∼ 1100 “high-probability” candidates occupying the assigned-redshift band of 1.8 to 2.4. Although the analysis is sensitive to very weak clustering we find no evidence that quasars are distributed in any way other than randomly. The implications of this result are discussed.
Radio Properties of Quasars and AGN
Authors: I. Kellermann K.
Published: July 2016

We discuss the compact radio sources associated with quasars and AGN with particular emphasis on the implications of their structure and kinematics for relativistic beaming models.