bluuebunny/crossref_metadata_2025 huggingface dataset:
Very Long Baseline Interferometry Observations Using the Tracking and Data Relay Satellite as an Orbiting Radio Telescope
Authors: Linfield R. P. , Levy G. S. , Ulvestad J. S. , Edwards C. D. , Jordan J. F. , DiNardo S. J. , Christensen C. S. , Preston R. A. , Skjerve L. J. , Stavert L. R. , Burke B. F. , Whitney A. R. , Cappallo R. J. , Rogers A. E. E. , Blaney K. B. , Maher M. J. , Ottenhoff C. H. , Jauncey D. L. , Reynolds J. E. , Nishimura T. , Hayashi T. , Takano T. , Yamada T. , Hirabayashi H. , Morimoto M. , Inoue M. , Tokumaru M. , Kawaguchi N. , Amagai J.
Published: June 2019

An antenna in geostationary orbit was used for VLBI observations at 2.3 GHz, in combination with ground antennas in Australia and Japan. 23 of the 25 observed sources were detected on orbiter-ground baselines, with baseline lengths as large as 2.15 earth diameters. Brightness temperatures between 1012 K and 4 × 1012 K were measured for 10 sources.
Chinese VLBI Network Project
Authors: Tongshan Wan , Zhihan Qian
Published: June 2019

The Chinese VLBI Network (CVN) project was proposed early in 1979, and since then VLBI research has been actively developed in Shanghai Observatory. However, only recently the whole project was accepted by the Astronomy Committee, Division of Mathematics and Physics, Academia Sinica.
The Parkes - Tidbinbilla Interferometer
Authors: Norris R. P. , Batty M. J. , Kesteven M. J. , Wellington K. J.
Published: June 2019

The Parkes - Tidbinbilla Interferometer is a radio-linked interferometer using the 64-m telescope at Parkes together with one of the NASA antennas (34-m or 64-m) at Tidbinbilla. With a baseline of 275km, it is currently the world's longest real-time interferometer, and is usable at frequencies of 1.6, 2.3, and 8.4 GHz to give angular resolutions of 0.13, 0.09, and 0.03 arcsec respectively, with a sensitivity of 1–2 mJy rms in 5 minutes at a bandwidth of up to 10MHz.
The Mark IIIA Correlator System
Authors: Whitney Alan R.
Published: June 2019

The Mark IIIA correlator system, developed at Haystack Observatory, is a second-generation version of the original Mark III correlator which adds significant new capabilities, such as double-speed operation, longer integration periods, and improved internal modelling. One Mark IIIA correlator is currently operational at the U.S. Naval Observatory in Washington, D.C., and another is being readied to replace the Mark III correlator at Haystack.

The Mark IIIA correlator can simultaneously process up to 10 baselines of 24-MHz BW data from 5 stations. Experiments including more than 5 stations may be processed with multiple passes through the correlator. The architecture of the correlator allows a future expansion to a maximum of 16 stations. Due to a simple modular design and the low cost of required computer-support equipment, expansion is straightforward and relatively economical.

Both astronomy and geodetic data processing are supported by the Mark IIIA system, including spectral line and pulsar gating. In addition, recent work has led to support of space-based VLBI observations; this capability was critical in supporting the first successful space-based VLBI astronomy observations between ground-based antennas and an orbiting satellite in August 1986.
Hydrogen Maser Support of VLBI for the NASA Crustal Dynamics Project
Authors: Price R. E. , Chandler M. J. , Schupler B. R. , Dachel P. R.
Published: June 2019

For the NASA Crustal Dynamics Project VLBI network, signals from quasars are recorded simultaneously at widely separated antennas. It is well known that hydrogen maser frequency standards provide the stable frequency reference used to precisely measure the difference in arrival time of the radio signals at the different antennas, enabling the determination of precise distances between the antennas. This paper reviews the practical requirements for maser support of VLBI for the Crustal Dynamics Project and describes the means used to meet these requirements for a network of eight fixed and three mobile stations which participate in approximately 200 VLBI experiments per year at locations in North America and the Pacific.
Developments in Continuum Imaging
Authors: Wilkinson P. N. , Conway J. , Biretta J.
Published: June 2019

We review recent progress in the practical aspects of making VLBI images from continuum data.
Test of Phase-Reference Mapping for Switched Observations
Authors: Alef Walter
Published: June 2019

An observing scheme and software for single frequency switched phase-referencing observations have been developed and tested on a source pair separated by 0.5° (0248+430, 0249+436). The phase connection was done utilizing closure properties of phase and phase-rate. A comparison of the phase-reference map with a hybrid map shows the success of the method.
Water Vapor Radiometry at the Onsala Space Observatory from 1980 to 1987
Authors: Johansson J. M. , Elgered G. , Rönnäng B. O.
Published: June 2019

Variations in atmospheric water vapor are difficult to correct for in geodetic, astrometric, and mm-wave astronomy VLBI. The use of a water vapor radiometer (WVR) has given promising results. The algorithm which relates the sky brightness temperatures observed by the WVR to the delay caused by atmopheric water vapor is discussed. Examples of WVR measurements made at the Onsala Space Observatory from 1980 to 1987 are presented.
The APM QSO Survey: Description and Status Report
Authors: Foltz Craig B. , Chaffee Frederic H. , Hewett Paul C. , Frye Brenda , Weymann Ray J. , Anderson Scott F. , Morris Simon L. , MacAlpine Gordon M. , Turnshek David A.
Published: June 2019

The APM QSO survey is a quantitative survey aimed at finding a large sample (∼ 1000) of QSOs using broadly-based selection criteria applied to machine-scanned UK Schmidt Telescope direct and objective-prism plates. The survey is currently entering its third year and, as of August 1988, the sample consists of ∼ 700 QSOs with mJ ≥ 18.75 in the range 0.2 ≤ z ≤ 3.3. Preliminary analysis suggests that the sample is relatively free of the selection effects endemic to most QSO surveys based on slitless spectroscopy.
A Complete Sample of Flat-Spectrum Radio Sources from the Parkes 2.7 GHz Survey
Authors: Savage Ann , Jauncey David L. , White Graeme L. , Peterson Bruce A. , Peters W. L. , Gulkis Samuel , Condon J. J.
Published: June 2019

A full version of this paper was presented at Workshop on Optical Surveys for Quasars (Tucson, January 1988) and will be published in the Proceedings.
Multivariate Statistical Analysis of the Sample of AGN
Authors: Petrosian A. R. , Karapetian M. Sh.
Published: June 2019

Radio, FIR, spectral and X-ray data by 11 parameters for the AGNs samples of Sy1, Sy1.5, Sy2 types and LINERs are compiled. All samples are processed by the multivariate statistical methods including factor and discriminant analysises. The following results are obtained:

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LINERs by principal factors, determining NLR and the central engine are clearly separated from the Seyfert galaxies.

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All types of the Seyfert galaxies in all have the same NLR.

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Intermediate Seyfert type is real. These AGNs are much more similar to Sy1 type objects than to Sy2.
Properties of a QSO Sample Selected Through Variability
Authors: Trevese D. , Koo D. C. , Kron R. G.
Published: June 2019

Variability of QSOs serves not only as an independent search technique but also as another parameter to correlate with such properties as luminosity (in radio, optical, X-ray), redshift, spectral features, color, etc., so as to better understand AGNs. We present some preliminary results on a variability study of an essentially complete sample using 4 m prime focus plates of a 0.3 deg2 field at the North Galactic Pole (SA57). The faintness of our survey, B ≈ 23; the precision of the measurements (σ ≤ 0.05 mag); and the availability of redshifts for many of the candidates provide an opportunity to study QSO variability in regimes previously unexplored (c.f. Bonoli et al. 1979 or Hawkins 1986).
The Masses of Quasars and AGN: Correlating the Accretion-Disk and the Emission-Line Methods
Authors: Wandel Amri
Published: June 2019

The UV continuum spectrum is used to extract the mass (and accretion rate) of quasars and AGN, assuming the UV is dominated by the emission from a thin accretion disk. This is done by fitting the observed luminosity and spectral slope in the UV by an accretion disk mode, giving the accretion parameters (black hole mass and accretion rate). An independent estimate of the mass is obtained using the emission-line method, which assumes that the velocity dispersion of the broad emission-line s is induced by the gravitational potential of the central compact object. For a sample of 36 quasars and Seyfert 1 galaxies, for which both data, the UV spectrum and the Hβ line width are available, the masses calculated with the two independent methods are in good agreement (within a factor of 2 for 75% of the sample) and highly correlated. Over three orders of magnitude in luminosity, the mass is found to increase less than linearely with luminosity, being in the range 108 < M < 1010M⊙, with L(1450A)/LEdd ranging from 0.001 for Seyferts to 0.03 for bright quasars.
Structure and Nature of AGNs
Authors: Netzer Hagai
Published: June 2019

This review discusses the present understanding of the inner region of AGN. Several fundamental questions are adressed, such as the determination of the central mass, the accretion rate and the presence or absence of massive accretion disks. The “standard model”, used until recently to deduce the density, ionization, geometry and other physical properties of AGN, is facing sever difficulties and several unsolved problems, such as the hydrogen line ratio, the FeII spectrum, the energy budget discrepency and the confinement of the broad line clouds may force us to abandon it all together. The new line-continuum reverberation measurements are perhaps the most important developement of recent years and their significance is discussed in relation to the other mentioned problems. Thin or thick accretion disks are likely to be present in the very center of AGNs. The theory of such disks is not advanced enough to provide accurate spectral calculations and the best way to identify them is to look for the signature of their nonisotropic radiation field in well selected samples. Several new developements and ideas, such as disk shaped emission line region, stars and stellar winds as broad line clouds, dust emission and very small-very dense BLR are also discussed.
Rapid Line Variations in High Luminosity AGN and Anisotropic Emission of the Optical/UV Continuum
Authors: Penston M V , Pérez E , Moles M
Published: June 2019

The emission lines of OVV quasars can vary significantly within a month, more rapidly than expected from photoionization models. This can be explained by anistropic continuum emission and joins several other lines of evidence suggesting anisotropic emission of the optical /uv continuum in AGN.
The NGC 1275 Galaxy Nucleus Emission Spectrum Variability at Various Stages of Activity
Authors: Pronik I. I.
Published: June 2019

Emission lines variability of Seyfert galaxy NGC 1275 nucleus in the scales of years and months has been observed since 1971 (I. Pronik, 1980). The photoelectric observations of I. Pronik and N. Merkulova (1987) show, that the variability in Hβ and 4959+ 5007 A [OIII] lines occurs also in the time scale of several days. Hereinafter the analysis of Hβ and [OIII] variable emission lines within months is presented according to photographic observations carried out from 1971 till 1982 by I. Pronik (1980), V. Doroshenko and V. Terebizh (1983) and K. Chuvaev (1985).
Investigations of Broad Line Region Structure and Kinematics Using Variability
Authors: Gaskell C. Martin , Koratkar Anuradha P. , Sparke Linda S.
Published: June 2019

Gaskell and Sparke (1986) showed that one can determine the sizes of BLRs more accurately that the mean sampling interval by cross-correlating the continuum flux time series with a line flux time series. The position of the peak in the cross-correlation function (CCF) and its shape give an indication of the BLR size. The technique is explained in detail in Gaskell and Peterson (1987). The widely propagated misunderstanding is that the method involves simply interpolating both time series and cross-correlating them (in which case the CCF is dominated by the cross-correlations of “made-up” data). Actually the method involves cross correlating the observed points in one time series (continuum, say) with the linear interpolations of the other series (line flux). The line flux time series must always be smoother than the continuum time series it is derived from. We have usually employed the method with the interpolation done both ways round and averaged them (to reduce errors due to the interpolation) and we can intercompare the two results (to investigate errors).
Emission-Line Variability in AGN
Authors: Maoz Dan
Published: June 2019

It has been apparent for some time that comparison of continuum and emission-line light curves of AGN may enable determination of the dimensions and structure of the Broad Line Region (BLR)(see Peterson 1988, and references therein). Observations to this end (Antonucci and Cohen 1983, Peterson et al. 1985, Clavel et al. 1987) and their analysis using cross-correlation to find the time lag between line and continuum variations (Gaskell and Sparke 1986), indicate BLR sizes an order of magnitude smaller than allowed by standard photoionization models for several AGN. Gaskell and Peterson (1987) analyzed errors in the cross-correlation method as applied to AGN time series in general and specifically to the Seyfert galaxy Akn120. In order to generalize and extend their analysis we investigated the significance of BLR sizes derived by cross-correlation under different model assumptions and observational circumstances (Maoz and Netzer 1988).
Broad Line Variations in NGC 5548
Authors: Rosenblatt Edward I. , Malkan Matthew A.
Published: June 2019

Since broad line variations can, in principle, constrain the structure and kinematics of the broad line region in active galaxies we have conducted a monitoring program of 20 Seyfert galaxies over a 5 year period in order to study broad line flux and profile changes. Included in our sample is the Seyfert 1.5 galaxy NGC 5548. Fifteen observations were taken from 1979 to 1984 mainly with the 60″ Palomar telescope and a SIT vidicon spectrograph. Measurements show (Fig. 1) that both the Hβ and Hγ line flux varied by 200% and the continuum varied by 300%. Furthermore, these changes were positively correlated as one would expect from photoionization by a central continuum source.
Soft X-ray Variability and the Covering Fraction of Active Galactic Nuclei
Authors: Strauss Michael A. , Wachter Kenneth W. , Filippenko Alexei V.
Published: June 2019

The variability of soft X-rays (0.2 – 2 keV) in some low-luminosity type 1 Seyferts may partly be due to an extrinsic mechanism: dense clouds of gas in the broad-line region, opaque to soft X-rays, move across our line of sight to the X-ray emitting portions of the accretion disk (Reichert, Mushotzky, and Holt 1986; Lawrence and Elvis 1982; Halpern 1984). As the clouds move, the covering fraction changes stochastically. Evidence for partial covering of the X-ray source in low-luminosity AGNs has been seen in soft X-ray spectra by Holt et al. (1980) and Reichert et al. (1985).
Physics of the Central Engine
Authors: Begelman Mitchell C.
Published: June 2019

I discuss physical processes which may be important in the central engines of AGNs. Black hole accretion models have been elaborated during the past few years, and provide a plausible framework for jet and spectrum formation. However, the specific mechanisms responsible for producing the observed continuum radiation remain uncertain. I consider nonthermal models for the IR continuum, constraints on thermal plasma, and the production of relativistic electrons.
Photon and Neutrino–Emission From Shockwaves in Active Galactic Nuclei
Authors: Biermann Peter L.
Published: June 2019

Many active galactic nuclei and/or associated jets and hot spots show a sharp cutoff in their nonthermal emission near ∼3 1014 Hz. Using the first order Fermi theory for particle acceleration at shocks we demonstrate that synchrotron emission and shock acceleration combine to give a maximum cutoff near to the observed frequency. We explore consequences: First, CCD-observations of the M87 jet demonstrate that the cutoff frequency decreases along the jet. Second, the detailed shape of the cutoff spectrum depends on the precise model for the turbulent wave field. Thirdly, an X-ray Synchrotron contribution from p-p and p-γ interactions exists which can match observed AGN spectra. Finally we apply the model to interpret the origin of very high energy cosmic rays, to the spectral behaviour of quasars and BL Lac's and deduce neutrino emission spectra of active galactic nuclei.
Observational Evidence for Supermassive Black Holes
Authors: Dressler Alan
Published: June 2019

A growing body of evidence from stellar dynamics in the nuclei of galaxies indicates that supermassive black holes of 107–109 M0 are common. The two best cases are M31 and M32, for which dark, central mass concentrations are the only straightforward interpretation. M87 continues to be a possible location of an even more massive black hole, but new observations and models by the author and D. Richstone effectively rule out the high black hole mass ∼5 × 109 M0 claimed by Sargent, Young, and collaborators. New data are available for several other nearby galaxies which also show kinematic signatures that could also be due to supermassive black holes. The Hubble Space Telescope will play the key role in strengthening these cases and eliminating, for the best examples, alternative models which do not require supermassive black holes.
Combined Accretion Disk and Nonthermal Source Model for AGN
Authors: Band D. L. , Malkan M. A.
Published: June 2019

We model the infrared through gamma ray AGN spectrum with a combined accretion disk and nonthermal source model and fit the spectra of a number of sources. The accretion disk model of Sun and Malkan (Sun 1987) adds relativistic effects to the emission from an optically thick, geometrically thin accretion disk; further details can be found in Sun and Malkan (1988) in these proceedings. In the nonthermal source model of Band and Grindlay (1986) relativistic electrons radiate the infrared continuum by synchrotron emission, and the X-ray spectrum by inverse Compton scattering of ultraviolet photons from the accretion disk. The electron distribution consists of a flat (n ∝ γ∼−2.4) low-energy component, and a steeper (n ∝ γ∼−3.4) high-energy component.
Calcium Infrared Triplet Emission in AGN
Authors: Persson S. E. , Ferland G. J.
Published: June 2019

Emission in the Ca II infrared triplet lines has been detected in 15 AGN. Correlations with optical Fe II emission and O I λ8446 linewidths indicate that Ca II emission comes from neutral gas within the BLR. A new series of ionization models that extend to column densities NH of 1025 cm−2 match the Ca II line strengths and various line ratios. The solution to the Ca II problem, which also solves the “Fe II problem” and the “energy puzzle”, is that a small amount of H− dominates the heating, even for NH ∼1022 cm−2, by absorbing the powerful near-infrared (1 μm) continuum.
Narrow Line Region in NGC 4151 Nucleus
Authors: Pronik V. I.
Published: June 2019

The well-known correlations of forbidden lines FWHM with the critical density for collisional de-excitation and with the ionization potential mean, that:

i.

the noticeable part of forbidden lines emission must arise in a gas of a rather high density n ∼ nc

ii.

the gas velocity, the density and the degree of ionization they all increase toward the centre of the nucleus.
Imaging Spectrophotometry of the Narrow-Line Region of NGC 1068
Authors: Cecil Gerald , Bland Joss
Published: June 2019

The NLR of the Sy 2 galaxy NGC 1068 has been studied with the Hawaii Imaging Fabry-Perot Interferometer on the U. Hawaii 2.2m telescope. Kinematics of [N II] λλ6548,6583 and Ha were mapped across the inner 1′-diameter by obtaining monochromatic images (65 km s−1 FWHM) with a low-noise (5e− RMS) CCD at sub-arcsecond spatial and ∼90 km s−1 effective velocity resolution. Our complete coverage of this nearby (14 Mpc; 1″ = 75 pc), spatially extended NLR allows unprecedented study of the interaction of a collimated radio “jet” (Wilson & Ulvestad 1983) with the warm ionized component of the ambient interstellar medium.
The Velocity Field of NGC 1068
Authors: Kaneko N. , Satoh T.
Published: June 2019

Sixty spectra taken at 24 position angles of every 15° were measured for NGC 1068. The result reveals that a noncircular motion of about 50 km/s occurs within a spiral disk of 30″–40″ in radius.
Millimeter Observations of Markarian Galaxies
Authors: Krügel Endrik
Published: June 2019

We report published data on dust emission from Markarian galaxies and discuss them together with recent spectroscopic work.
Are ELFs Little Monsters?
Authors: Norris R.P.
Published: June 2019

High resolution radio observations of Seyferts, starbursts, and ELFs are presented which suggest that (i) starburst galaxies do not generally possess a Seyfert-like core, (ii) some ELFs do have a Seyfert core, but only those with a Seyfert-like spectrum, (iii) other ELFs are more likely to be powered by starburst activity. Double compact sources are present in several ELFs, suggesting that we might be seeing the nuclei of two merging galaxies, and that the ELFs are conceived by the coupling of two monsters.
Spectral Energy Distributions of PG Quasars
Authors: Neugebauer G. , Sanders D. B. , Soifer B. T. , Phinney S. , Green R. F.
Published: June 2019

Between 1013 - 1017 Hz the continua of all PG quasars can be described in the most general terms by a model consisting of two broad peaks of thermal radiation. There is no evidence for energetically significant nonthermal radiation in this frequency range in the continua of the PG quasars. We have compiled continuum observations for PG quasars from 6 cm to 2 KeV, including IRAS data for all these objects and new ground-based infrared data at 10 μm for many of these quasars. Sixty-three of the PG quasars were detected by IRAS in at least one band. The overall energy distributions for these sixty-three PG quasars are shown in Figure 1.
Infrared Imaging and Photometry of a Sample of Seyfert Galaxies
Authors: Zitelli V. , Wade R. , Danese L. , De Zotti G. , Granato G. , Mandolesi N.
Published: June 2019

It is well know that the determination of the local luminosity function of Seyfert nuclei meets several difficulties produced by: the determination of a suitable sample, the estimation of the nuclear magnitudes biased from the contribution from the host galaxies, which may be dominant if the nucleus is faints and the presumably large errors associated with the estimated magnitudes.
Circumnuclear Emission in Nearby, Non-Interacting Seyfert Galaxies
Authors: Pogge Richard W.
Published: June 2019

An investigation of the physical conditions present in the circumnuclear regions of 20 nearby, non-interacting Seyfert galaxies is reported. Significant differences are observed between the circumnuclear properties of Seyfert 1s and Seyfert 2s with regards to extended ionized gas. The morphology and ionization of the circumnuclear gas suggests collimation of the nuclear ionizing radiation field; in 4 cases taking the form of distinct conical distributions of ionized gas emanating from the nucleus. Some of these properties are consistent with prevailing “unified” models for AGN. However, it is difficult to reconcile all of the observed differences between Seyfert 1s and 2s with this picture.
Bar Instabilities and Nuclear Activity in Disk Galaxies
Authors: Shlosman Isaac , Frank Juhan , Begelman Mitchell C.
Published: June 2019

A mechanism for fueling active galactic nuclei and nuclear starburst galaxies is suggested. It consists of two stages. First, a large-scale stellar bar sweeps the ISM into a gaseous disk of a few hundred pc radius. This disk may, under certain conditions, become dynamically unstable, induce radial flow, and feed viscosity-driven accretion flow around a black hole. It may lead to the formation of a black hole if none was present initially.
Low-Luminosity Active Galactic Nuclei
Authors: Filippenko Alexei V.
Published: June 2019

I review the basic properties of low-luminosity active galactic nuclei (LLAGNs) — objects in which activity similar to, but intrinsically milder than, that in QSOs and luminous Seyferts is believed to be present. Until recently, most LLAGNs were first recognized as such and studied at optical wavelengths, but evidence for activity and valuable information concerning its nature are now also being obtained in many other spectral ranges. Low-ionization nuclear emission-line regions (LINERs) are the most common LLAGNs; in a large fraction of them the emission lines come from clouds of gas probably photoionized by a nonstellar continuum, rather than heated by shocks. It is also clear, however, that there could be substantial heterogeneity among LINERs, particularly those with extended emission; some may be produced by cooling flows, supernova-driven winds, and galaxy interactions or mergers. LLAGNs can easily be hidden from sight in a variety of ways, including obscuration by galactic or circumnuclear disks and dilution by bursts of star formation. Direct imaging, spectroscopy, and spectropolarimetry can be used to isolate the different components, especially with high spatial and/or spectral resolution. A surprising result is that Seyfert nuclei are sometimes found in dwarf and very late-type galaxies. The nearby Sd III-IV galaxy NGC 4395 contains the intrinsically faintest known Seyfert 1 nucleus, with a broad Ha luminosity only ∼ 0.1 that of M81. The idea that the apparent “activity” in some galaxies is a direct consequence of vigorous star formation has some strong supporting evidence, and should seriously be considered. As an example, I focus on the peculiar supernova 1987F, whose optical spectrum bears a striking resemblance to that of typical Seyfert 1 nuclei.
High-Resolution Observations of the M81 Nucleus
Authors: Keel William C.
Published: June 2019

The nucleus of the nearby Sb galaxy M81 has been shown to exhibit many of the features prominent in luminous active galactic nuclei: a variable, compact VLBI radio source (Kellermann et al. 1976, Jones, Sramek and Terzian 1981), a central variable X-ray source (Elvis and van Speybroeck 1982, Fabbiano 1988), and broad wings of Balmer emission similar in extent to those typical to Seyfert 1 nuclei (Peimbert and Torres-Peimbert 1981, Shuder and Osterbrock 1981). The nucleus also shows a narrow-line spectrum in many ways typical of LINERs (Heckman 1980), now known to be representative of early-type spiral nuclei in general.
Activity in the Nuclei of Normal Sbc Galaxies - A Multiwavelength Study
Authors: Davies R. D. , Pedlar A. , Axon D.J. , Vila B. , Hummel E. , Wolstencroft R. D. , van der Hulst J.M.
Published: June 2019

This study of the activity in the nuclei of normal galaxies began as an investigation into the spread in the observed properties of normal galaxies used as standard candles in measurements of departures from the Hubble flow (Hart & Davies 1982). Extensive studies of the integrated properties of normal galaxies show the influence on these properties of quiescent star formation and embedded starburst-type activity (Staveley-Smith & Davies, 1987,1988). Normal galaxies have a significant level of nuclear activity, although it is not strongly correlated with their integrated properties. This investigation of nuclear activity is based on a sample of the 100 brightest nearby Sbc galaxies, a sample unbiassed in its selection of activity.
Physical Conditions in Active Galactic Nuclei
Authors: Artyukh V. S.
Published: June 2019

Self-absorption of synchrotron radiation in compact radio sources gives rise to a low-frequency cutoff in their spectra. To study this effect it is necessary to observe the radio sources at meter wavelengths with angular resolution < 1″. Such observations of compact radio sources located in active galactic nuclei lead to estimates of magnetic field strengths and relativistic electron number densities in the AGNs.
Lyman Edges in Quasar Spectra
Authors: Kinney A. L. , Antonucci R.R.J. , Ford H. C.
Published: June 2019

This is a study of the Lyman edge region in the spectra of eleven high redshift quasars. We present large aperture, low resolution data designed to detect broadened Lyman edge absorption predicted by thermal models of the Big Blue Bump continuum component. We also present high resolution data on the edge regions and the Lyman alpha emission line for nine of the objects. We show some partial absorption edges and discuss whether or not they can be interpreted as support for the accretion disk model.
Calcium Features in the “Featureless” Continuum of Seyfert Nuclei: Evidence for a Young Stellar Population?
Authors: Díaz Angeles I. , Terlevich Elena , Terlevich Roberto
Published: June 2019

We have obtained intermediate resolution spectra for about 30 galaxies, normal and active, in the near infrared region covering the CaII triplet (λλ 7800–9300 Å). The data were obtained with the INT at the Roque de los Muchachos Observatory in La Palma, Spain using the Intermediate Dispersion Spectrograph and a GEC CCD detector. Details of these observations are given elsewhere (Terlevich et al. 1988). Our data show that active (Seyfert galaxies and LINERS) and normal galaxies have comparable nuclear CaII strengths and line widths.
Prospects for space Telescope in the search for other Planetary Systems
Authors: Russell J. L.
Published: June 2019

The Hubble Space Telescope (ST) will be launched with five dedicated scientific instruments and a capability to do astrometric measurements with the fine guidance sensors. Four of these – the Faint Object Camera, the Wide Field Camera, the Fine Guidance Sensors and the High Speed Photometer – can be used in the search for extrasolar planetary systems. The Faint Object Camera will be able to directly detect planets around a few of the nearby bright stars. The Wide Field Camera and the Fine Guidance Sensors can be used astrometrically, both with an accuracy of about 2 mas per observation. The High Speed Photometer possibly can detect planets during occultation of stars by the moon and minor planets. The ST is expected to be launched in mid-1986 and these observations are the among the first planned with the instruments.
Detecting Distant Planets with Space Telescope
Authors: Page Thornton
Published: June 2019

In 1981 and in 1984, I offered at the University of Houston, CLC, a course on Space Telescope, the first of its kind. The 22 graduate students were assigned research projects of their own choosing designed for ST. Several chose the detection of planets of other stars, showing the popularity of the search for extraterrestrial life. Space Telescope's six instruments can be used for this purpose in several ways, and the students, most of them scientists and engineers at the NASA Johnson Space Center, proposed to use most of these after ST is launched in 1986 or 1987. The student proposals require a significant fraction of ST observing time over a period of five to ten years, indicating the over-subscription that faces the ST Science Institute. In this paper, I summarize the capability of ST instruments, and recount the techniques likely to be most effective in using them to detect planets of other stars.
SETI Observations Worldwide
Authors: Tarter Jill
Published: June 2019

This paper reviews all recent SETI observing programs that the author is aware of from the literature and private communication. The technical parameters of all known SETI efforts are summarized in an appendix containing references whenever possible.
The Ohio SETI Program - the First Decade
Authors: Dixon Robert S.
Published: June 2019

A full-time dedicated SETI progam has been in operation at Ohio State University since 1973. A 50-channel narrowband filter bank is in use near the 21 cm. hydrogen-line. All data is processed in real time and permanently recorded. A large portion of the northern sky has been surveyed and analyzed for large-scale structure. The only obvious non-random structure is caused by isolated narrowband pulses, which are anti-correlated with galactic latitude, and congregate in two specific areas. The origin of these pulses is unknown, although they may be partially due to instrumental effects.
Lunar Reflections of Terrestrial Radio Leakage
Authors: Sullivan Woodruff T. , Knowles Stephen H.
Published: June 2019

Terrestrial radio leakage as reflected off the moon has been observed with the Arecibo antenna. We find that military radars and television transmitters are main contributors in the 150–500 MHz range, as predicted in the model of Sullivan et al. (1978). The earth indeed is revealing itself (eventually) to any interstellar eavesdropper with an Arecibo-like antenna at distances up to 30 light years, and with a Cyclops-like system up to fifteen times farther.
Eavesdropping Detection of Radio Signals from Other Planets, with One Bit-Implementation Techniques Using Existing Computers
Authors: Knowles Stephen H.
Published: June 2019

Detection of other civilizations by “eavesdropping” on accidental radiation from television and other self-oriented signals is proposed. One-bit spectral analysis techniques to implement this are discussed. These can utilize existing general-purpose computers, and provide flexibility of strategy in the analysis. The first derivative of doppler shift from an unknown planet can be compensated for with increased integration times possible.
The 8-Million Channel Narrowband Analyzer
Authors: Horowitz Paul , Forster John , Linscott Ivan
Published: June 2019

An 8.4 million channel narrowband spectrum analyzer is nearing completion, and will be used to expand the frequency coverage of the ongoing search at Oak Ridge by a factor of 200. The new system – project META – will cover 420kHz at 0.05Hz resolution, utilizing a swept receiver to cancel the effect of the earth's rotation. The increased bandwidth will permit observation of CW beacons transmitted at magic frequencies in any of three preferred frames: the local standard of rest, the galactic barycenter, and the cosmic blackbody rest frame.
SETI: The Microwave Search Problem and the Nasa Sky Survey Approach
Authors: Klein Michael J. , Gulkis Samuel
Published: June 2019

NASA's microwave observing program for SETI is presented. This strategy is composed of a high sensitivity, narrow frequency coverage, Target Search and a low sensitivity, broad frequency coverage, Sky Survey. The complementary nature of this dual mode search strategy is discussed. An overview is given of ongoing work in the development of the search strategy for the Sky Survey.
Optimum Search Strategy for Randomly Distributed CW Transmitters
Authors: Gulkis Samuel
Published: June 2019

The relative probability of detecting randomly distributed CW transmitters as a function of the fraction of the sky which is searched (in a fixed time interval) is given. It is shown that the probability of detecting such a class of transmitters with a given receiving system is a maximum if the entire sky is searched, provided that the receiving system is sufficiently sensitive to detect the nearest transmitter in the allocated time and that the integration time - bandwidth product in a specified direction is greater than 8.
The Serendip II Design
Authors: Werthimer Dan , Tarter Jill , Bowyer Stuart
Published: June 2019

Serendip II is an automated system designed to perform a real time search for narrow band radio signals in the spectra of sources in a regularly scheduled, non-Seti, astronomical observing program. Because we expect Serendip II to run continuously without requiring dedicated observing time, we hope to survey a large portion of the sky at high sensitivity and low cost. Serendip II will compute the power spectrum using a 65,536 channel fast Fourier transform processor with a real time bandwidth of 128 KHz and 2 Hz per channel resolution. After searching for peaks in a 100 KHz portion of the radio telescope's IF band, Serendip II will move to the next 100 KHz portion using a programmable frequency synthesizer; when the whole IF band has been scanned, the process will start again. Unidentified peaks in the power spectra are candidates for further study and their celestial coordinates will be recorded along with the time and power, IF and RF frequency, and bandwidth of the peak.
Fermi Question, Fermi Paradox: One Hit, One Out
Authors: Seeger Charles L.
Published: June 2019

Our understanding of the universe and the history of life on Earth suggests we may not be alone in the Galaxy. Today we are ignorant of where “they” are, if they are, as was Fermi when he asked, “Where are they?” Many scientists believe the way to seek for answers is to search for “their” radiated signature. (Hence SETI, now.) But some have argued persistently that since they are not here, they are not out there, and a few insist the situation is paradoxical. This note samples speculations supporting this view and concludes one cannot make a worthy paradox from absent evidence, a belief that interstellar travel will soon be a cinch, and a willingness to predict the distant future of intelligent species.
Two Additional Comments
Authors: Ball John A.
Published: June 2019

Wandering in the wilderness (1) of search space and (2) among the stars.
A Look into the Future
Authors: Papagiannis Michael D.
Published: June 2019

The quest for extraterrestrial life and for other stellar civilizations has finally become an international scientific endeavor. As our technology advances and major astronomical observatories are established in space, we will be able to gain a better understanding of ourselves and the Cosmos.
Activities and Resolutions of IAU Commission 51
Authors: Papagiannis Michael D.
Published: June 2019

The origin of our Commission can be traced to a highly successful, one-day Session on “Strategies for the Search for Life in the Universe” which we organized in 1979 at the 17-th IAU General Assembly in Montreal. When on the next evening Frank Drake and myself gave a report on this Session to the IAU in an open meeting, the large auditorium of the University of Montreal was packed to standing room only with more than 1,000 astronomers from all around the world, confirming the unexpectedly strong interest that indeed existed among astronomers on this subject.
The Dynamics of 47 Tucanae
Authors: Da Costa G. S. , Freeman K. C.
Published: June 2019

Observations made at Las Campanas Observatory and at the Anglo-Australian Observatory have been used to determine line-of-sight velocities with an average accuracy of 3 kms−1 for 135 member stars in the globular cluster 47 Tucanae. The velocities were derived from cross-correlation techniques applied to 30 A/mm spectra obtained with digital sky-subtracting detectors. The spectra themselves have been used to analyze the cyanogen anomalies on the red giant branch in this cluster (Norris et al., 1984). When combined with the velocities published by the CORAVEL group (Mayor et al., 1983), these observations yield velocities for 212 stars with projected distances from the cluster center ranging from 3 to 68 core radii. After radial binning and analysis these observations yield the following results:

(i) The inner parts of the cluster show appreciable differential rotation with a maximum projected rotation velocity of approximately 6 kms−1 in the region 6–18 core radii. However, at larger radii the rotation declines rapidly and is essentially zero for radii greater than 30 core radii. This result is illustrated in Figure 1. To within the errors of the determinations, the position angle of the maximum rotation and that of the major axis of the stellar density distribution coincide.

(ii) In contrast to M3 (Gunn and Griffin 1979), “thermal equilibrium” multimass models (c.f. Da Costa and Freeman 1976) can ONLY reproduce the observed velocity dispersion values by including a substantial amount of “dark matter”; i.e. unlike M3, there is “missing mass” in 47 Tuc. In order to retain a fit to the surface brightness profile of the cluster, this “dark mass” (which provides perhaps 30 to 40 percent of the total cluster mass) cannot have a distribution much different from that of the cluster giants if it is in the form of stars and “thermal equilibrium” is maintained. In this case the obvious candidates for the dark matter are the white dwarf remnants of the stars more massive than the current turnoff mass, though many more such remnants are required than the number expected from extrapolating the present mass function. The difference between M3 and 47 Tuc in this case then implies that the 47 Tuc initial mass function had many more massive stars than did that for M3. The work of Freeman (1977), who demonstrated large IMF variations in the 8 − 1.5 solar mass range in young Magellanic Cloud clusters, provides observational support for this interpretation.
A Search for Post-Collapse Cores
Authors: Djorgovski S. , Penner H.
Published: June 2019

We report the preliminary results of a surface photometry survey of globular cluster cores. Two new cores with post-collapse morphology have been found, and two possible candidates. The estimated fraction of clusters with this core morphology in the Galaxy is only a few percent. Most clusters do not show a morphology similar to the predictions of the central black hole models.
Core and Tidal Radii of the Carina Dwarf Spheroidal Galaxy from UK Schmidt Telescope Plates
Authors: Godwin P. J.
Published: June 2019

Core and tidal radii of the Carina dwarf galaxy are determined by fitting King dynamical models to number count radial profiles, derived from COSMOS data. These values are compared with those of the other six known Local Group dwarf spheroidals.
Where's the CUSP? (or CCD Photometry of Globular Cluster Cores)
Authors: Lugger Phyllis M. , Cohn Haldan , Grindlay Jonathan E.
Published: June 2019

UBVR CCD surface photometry for a sample of 11 globular clusters has been obtained at the Kitt Peak National Observatory (KPNO) #1 0.9 m telescope as part of a major study of globular cluster core structure. These data are being used to test for the presence of central cusps in the surface brightness profiles', which are expected to be present in clusters which have already undergone core collapse (Cohn and Hut 1984).
A Search for Cataclysmic Binaries in the Globular Cluster M3
Authors: Shara M. M. , Moffat A. F. J. , Hanes D. A.
Published: June 2019

Deep Hβ narrowband and broadband images of M3 have been electronically blinked to search for cataclysmic binaries. Tests of the method on a known, faint cataclysmic enable us to set limits on the sensitivity of the technique. No bright (MB < 6) emission-line (equivalent width > 12 Å) cataclysmic binaries exist in M3 between 4 and 30 core radii from the center. Low luminosity globular X-ray sources could still be weak-lined (E.W. < 12 Å) and bright (MB ≃ +5 like some old novae) or strong-lined (E.W. ≃ 60 Å) and faint (MB > 7 like dwarf novae).
Rotation and Flattening of Globular Clusters
Authors: Fall S. Michael , Frenk Carlos S.
Published: June 2019

Pease and Shapley (1917) first remarked on the apparent flattening of several Galactic globular clusters, a view that has been confirmed by many subsequent studies. Tidal stresses, internal rotation, and velocity anisotropies can cause deviations from sphericity in stellar systems. In general, we might expect globular clusters to have some angular momentum at the time of formation and, if they collapsed from flattened initial conditions, to have anisotropic pressure support. Since the velocity distributions within the clusters can be altered by a variety of internal and external processes, their shapes are expected to evolve. In this article, we review the methods for measuring ellipticities and the results that have emerged from such studies. Our main purpose, however, is to discuss the processes that determine the shapes of globular clusters and the ways in which they change with time.
Minimum of the Eccentricity of the Galactic Globular Cluster Orbits
Authors: Colin Jacques
Published: June 2019

We determine if the orbits of the galactic globular clusters can be circular, using a spherical logarithmic potential. If they are not, we calculate their perigalactic distances and we deduce a pseudo-eccentricity. Using a numerical and geometrical method, we obtain the minimum of all the possible pseudo-eccentricities for each cluster. The corresponding perigalactic distances are compared with the values given by Innanen et al. (1983) with a different method.
Collisional Stellar Dynamics in General Relativity: An Overview
Authors: Kandrup Henry E.
Published: June 2019

Recently, Israel and Kandrup (1984; Kandrup 1984 a,b,c,d) have formulated a new, manifestly covariant approach to non-equilibrium statistical mechanics in classical general relativity. The object here is to indicate how that formalism may be used to construct a theory of ‘collisional’ stellar dynamics, valid for a collection of point mass stars in the limit that incoherent radiative effects may be neglected.
Physical Interactions Between Stars
Authors: Ostriker Jeremiah P.
Published: June 2019

Physical arguments are presented to show that two-body, tidal-capture binaries should form in abundance (Nb ~ 103) during the evolution of globular clusters by the time that core collapse begins. Interactions amongst these binaries and with core single stars will cause ejections from the cluster which pump energy into the system producing a bounce and re-expansion. Detailed numerical Fokker-Planck evolutionary calculations presented here confirm this scenario and indicate that this process is likely to be the dominant energy input for most clusters. During the re-expansion phase rcore ∝ t1/3, rhalf ∝ t2/3 with the core containing several hundred very close binary star systems.
Monte-Carlo Calculations
Authors: Stodółkiewicz J.S.
Published: June 2019

The evolution of a nonisolated globular cluster is presented. The binaries (both, tidally captured and formed in three-body interactions), outflow of mass from stellar envelopes and shocks are considered as sources of energy in the cluster.
The Dense Stellar Cores of Giant HII Regions
Authors: Moffat A.F.J. , Seggewiss W. , Shara M. M.
Published: June 2019

We explore the bright central diffuse objects of the closest visible giant HII regions 30 Dor (LMC) and NGC 3603 (Galaxy), with the aid of CCD imagery in 1′ seeing. Both central objects are interpreted as dense cluster cores composed of normal stars with masses ranging up to ≈ 100 M⊙. Each object appears to contain at least one close massive binary. Being significantly denser, the core of NGC 3603 seems to be dynamically more evolved than the core of 30 Dor.
A Proper Motion Study of the Pleiades Cluster
Authors: van Leeuwen Floor
Published: June 2019

The first results of an extensive proper motion study of the Pleiades cluster are presented. A total of 166 exposures covering a 3 by 3 degrees area are now incorporated. The accuracies of the centennial proper motions range from in the central region to in the outermost region.
Planetary perturbation equations based on relativistic Keplerian motion
Authors: Ashby Neil
Published: June 2019

Solutions of the geodesic equations for bound test particle motion in a Schwarzschild field are expressed using Jacobian elliptic functions. Keplerian orbital elements are identified and related to a set of canonical constants. Relativistic Lagrange planetary perturbation equations are derived.