bluuebunny/crossref_metadata_2025 huggingface dataset:
Type IA Supernovae
Authors: Wheeler J. Craig
Published: June 2019

Spectral calculations show that a model based on the thermonuclear explosion of a degenerate carbon/oxygen white dwarf provides excellent agreement with observations of Type Ia supernovae. Identification of suitable evolutionary progenitors remains a severe problem. General problems with estimation of supernova rates are outlined and the origin of Type Ia supernovae from double degenerate systems are discussed in the context of new rates of explosion per H band luminosity, the lack of observed candidates, and the likely presence of H in the vicinity of some SN Ia events. Re-examination of the problems of triggering Type Ia by accretion of hydrogen from a companion shows that there may be an avenue involving cataclysmic variables, especially if extreme hibernation occurs. Novae may channel accreting white dwarfs to a unique locus in accretion rate/mass space. Systems that undergo secular evolution to higher mass transfer rates could lead to just the conditions necessary for a Type Ia explosion. Tests involving fluorescence or absorption in a surrounding circumstellar medium and the detection of hydrogen stripped from a companion, which should appear at low velocity inside the white dwarf ejecta, are suggested. Possible observational confirmation of the former is described.
Y Cygni?
Authors: Batten Alan H.
Published: June 2019

It is often assumed that a binary begins to interact when one of its components makes contact with its Roche lobe, thus “switching on” a new evolutionary process. The example of Y Cygni is used to illustrate the view that the whole lifetime of a binary helps to determine whether or not its components will interact. Of particular importance is the interval between the formation of a binary and the arrival of its components on the main sequence, during which probably all binaries are interacting. Barring accidents, the properties of the components when they reach the main sequence will define the whole subsequent history of the system, including whether or not there will be subsequent phases of interaction triggered by contact with the Roche lobe. Like any other mechanical system a binary will tend towards the state of lowest energy consistent with the constraints on it. This it can do by losing mass, equalizing the component masses, or reducing its separation. We therefore expect systems to tend to small masses to mass-ratios of unity, or to coalesce into single stars. In any given system, probably all three tendencies exist, but one dominates. For example, W Ursae Majoris systems may be fusing into single stars. The rotation, chemical composition, and magnetic fields of the component stars may modify the evolution of a binary and be responsible for the variety of interacting systems that we observe. Most interacting pairs are losing mass to the interstellar medium, so a complete study of binary evolution must consider not only the dynamical, but also the chemical, effects of binary systems on the evolution of the Galaxy.
Recent Results on the Apsidal Motion Test in Eclipsing Binaries
Authors: Gimenez A. , Claret A.
Published: June 2019

A selected sample of eclipsing binaries with well-defined apsidal motion rates and accurate absolute dimensions has been analysed and compared with most recent evolutionary models of the stellar internal structure. A reasonably good agreement has been achieved when models including convective-core overshooting, mass loss, and stellar rotation in the evolutionary code, are used. The systematic difference in log k2 reported by previous authors between observed and theoretically predicted values is no longer detected for stars with well-determined absolute dimensions, and a few anomalous cases can be easily explained in terms of the validity of the adopted assumptions.
Evolutionary Sequences for Binary Stars in the Mass Range 9 to 40 M⊙
Authors: De Loore C. , De Greve J.P.
Published: June 2019

A set of evolutionary sequences for the two components of massive close binaries in the mass range 9 to 40 M⊙ for mass ratios 0.9 and 0.6 has been calculated. The used code accounts for mass transfer according to case B, i.e. mass exchange after core hydrogen exhaustion, during semi-detached and contact phases. All models were computed for a single initial chemical composition X = 0.7, Z = 0.02. Stellar wind mass losses were taken into account, as well as convective core overshooting (α = 0.25). The Roche lobe overflow was calculated according to a simplified hydrodynamical treatment. For the mixing of infalling material with the originally present layers the process of thermohaline mixing was adopted. It was assumed that 50% of the matter lost by the primary is accreted by the secondary.
Eclipsing Binaries in Multiple Star Systems
Authors: Chambliss C. R.
Published: June 2019

Although the majority of the known eclipsing binaries are in systems which consist of only the two eclipsing components, a significant number of them do occur as components of triple star systems or higher order multiple star systems. In this context this term is restricted to those systems whose components are in closed orbits. A recent survey of visual binaries with variable components is that by Proust et al. (1981), which details about 300 systems. Walker (1979) has also prepared a list of variables as components of double star systems, and this includes numerous systems not included in other lists.
Investigation of the Eclipsing Binary AN Tauri
Authors: Kreiner J.M. , Krzesinski J. , Pajdosz G. , Tremko J. , Zoła S.
Published: June 2019

AN Tau has been classified as the β Lyrae-type variable. The only visual light curve was published 55 years ago. The star was observed photoelectrically during a few last years at Mt. Suhora and Skalnaté Pleso Observatories. The complete light curve was obtained in B and V band passes. The preliminary physical parameters of the system were obtained using the Wilson-Devinney code. From the period study of AN Tau we derived new period of the system being 1d.6143843, which differs by 0d.00026 from the value obtained earlier. The orbital period of AN Tau seems to be constant.
A Spectrographic Study of the Interacting Eclipsing Binary RY Scuti: An Episode in the Rapid Mass Loss Stage or a Protoplanetary Nebula?
Authors: Sahade J. , West R.M. , Skulskij M. Yu.
Published: June 2019

RY Scuti, the 11-day [Fe III] eclipsing binary, has been reinvestigated on the basis of spectroscopic material secured at the European Southern Observatory (ESO), La Silla, Chile, and at the Cerro Tololo Interamerican Observatory (CTIO), Chile, that cover the regions 3400–5150 Å and 5700–6700 Å, and worked out with the measuring and computing facilities at the ESO Headquarters, Garching bei München, Germany. Ultraviolet observations taken with the IUE satellite were also analyzed.
Mass Transfer Characterization in Close Binary Stars
Authors: García J. M. , Giménez A.
Published: June 2019

A method for estimating representative values of the parameters that characterize the loss of mass and angular momentum occurred during the evolution of a close binary star is considered. Absolute dimensions previous to mass-transfer stage have been obtained for a select group of 43 semidetached systems adopting a grid of values of mass loss, angular momentum loss and initial mass ratio. Our study reveals a highly non-conservative scenario for the evolution towards an Algol-type system.
A Search for White Dwarf Companions of Be Stars
Authors: Piters A.J.M. , Meurs E.J.A. , Coté J. , Van Kerkwijk M.H. , Van Paradijs J. , Pols O.R. , Waters L.B.F.M.
Published: June 2019

Preliminary results of an extended multi-wavelength study of bright B- and Be-type stars are presented. This project aims at finding evidence for the existence of white-dwarf companions to Be stars which are predicted as the result of close binary evolution. Comparison of ROSAT all-sky survey data with simultaneous measurements of Hα profiles and infrared photometry suggests that there is no difference in the X-ray behaviour of Be stars with respect to that of normal B stars. The ROSAT X-ray luminosities of B and Be stars range from 10−8 to 10−5 times the bolometric luminosity.
Bolometric Light Curves of Symbiotic Novae
Authors: Mürset U. , Nussbaumer H.
Published: June 2019

We determine bolometric light curves and total energies radiated away during the outburst of symbiotic novae. Time integrated lower limits to the total energy of 0.9×1046<E[erg] < 7×1046are found. Thus, the output is comparable to, or larger than the total energy production of a classical nova outburst. From the mass-luminosity relation we find the underlying stellar masses to be 0.5 <M/M⊙< 1.1.
Outbursts by Low-Mass White Dwarfs in Symbiotic Variables
Authors: Sion Edward M. , Ready Christian J.
Published: June 2019

We have investigated the nature of P Cygni-like features in the high resolution IUE spectra of the symbiotic variables BF Cyg and EG And by looking for orbital phase-dependent variations in the structure and velocity of the C IV (1550 Å) resonance doublet in 10 archival IUE high-dispersion spectra of these systems and by comparing their profiles with P Cygni-like features seen in IUE high-dispersion spectra of other symbiotic stars. For BF Cyg, we find maximal P Cygni absorption equivalent widths and terminal velocities of ~ 900 mÅ and ~ −240 km s−1 respectively, full emission velocity widths at the 10% intensity level of 300–400 km s−1, depending on phase, Φ, variations in the width of the P Cygni absorption, shortward velocity shifts of the C IV emission line in all but two orbital phases, relative to the C IV velocity at Φ = 0.01, and absorption sub-structure within the C IV P Cygni lines which coincide in velocity from image to image. In EG And the C IV P Cygni absorption equivalent width is, on average, 300 mÅ with a terminal velocity of −217 km s−1 (which includes the systemic radial velocity contribution of -93 km s−1). The presence in one image, of a strong absorption feature at He II (1640), having a precise velocity coincidence with the C IV P Cygni absorption component, suggests that the absorbing material responsible for both line features is associated with outflow and P Cygni self-absorption from the vicinity of the hot component. In both BF Cyg and EG And, the structure and behavior of the P Cygni profiles may rule out their origin in the red giant wind or in an expanding circumbinary shell. Our results support the hot component wind interpretation of Mikolajewska et al. (1989). Motivated by the low-mass white dwarf shown to be present in BF Cyg (Mikolajewska et al. 1989), we have carried out quasi-static evolutionary model calculations with accretion onto a 0.55 M⊙ white dwarf accreting at the rate 2 × 10−8 M⊙ yr−1. The sequence of 3800 quasi-static models, the first to be reported for a low-mass hot white dwarf (Mwd < 0.8 M⊙) accreting at a high rate, yields an unexpected outburst behavior in response to accretion at that rate, when compared to evolutionary sequences with accretion onto higher mass white dwarfs. A series of three major thermonuclear shell flashes and one lower energy shell flash is revealed with the timescale during outburst and the inter-outburst timescale substantially shorter than expected for a 0.55 M⊙ white dwarf. Preliminary results on other sequences are also reported. Implications for the observations of symbiotic systems thought to contain low-mass white dwarfs, are discussed.
Note on LMC X-4
Authors: Herczeg Tibor J.
Published: June 2019

Orbital and stellar parameters of the massive X-ray binary LMC X-4 are rediscussed with particular attention to a possible “higher mass” (> 1.4 M⊙) neutron star in the system.
Interacting Binary White Dwarf Stars
Authors: Solheim J.-E.
Published: June 2019

This group of stars consists of 4 systems, also called helium cataclysmics. Three of them show photometric variations and have been studied by the Whole Earth Telescope (WET), which have revealed multiperiodic light curves showing the signature of g-mode non-radial pulsations on the accreting star. The combination of accretion and g-mode pulsations gives a unique opportunity to test models for the accreator's structural changes in response to accretion. IUE-spectra provide additional physical parameters.
Can Evolution in Close Binaries Account for the Blue Stragglers in M67?
Authors: Milone Alejandra A. E. , Latham David W. , Mathieu Robert D. , Morse Jon A. , Davis Robert J.
Published: June 2019

For the past 9 years we have been monitoring the radial velocities of 13 blue stragglers in the old open cluster M67. For the 9 blue stragglers with rotational velocities no larger than about 100 km s−1 we have used the CfA digital speedometers to measure more than 500 radial velocities. To get reliable velocity correlations we use synthetic rotating templates computed from a grid of Kurucz model atmospheres. Four of the blue stragglers rotate too rapidly to allow successful velocity correlations with the CfA instruments. For three of these we have used a CCD spectrograph at Kitt Peak and similar reduction procedures (Morse et al. 1991.
Constraints on the Cessation of Eclipses in SS Lacertae and Their Implications for System Evolution
Authors: Milone E. F. , Stagg C. R. , Schiller S. J.
Published: June 2019

SS Lac, a probable member of the open cluster NGC 7209, and a target system of several apsidal motion programs and of our binaries-in-clusters program for the past decade, is no longer eclipsing. The sudden disappearance of eclipses is now well documented. Zakirov and Azimov (IBVS 3487, 1990) and Schiller et al. (BAAS 23, 879, 1991) announced the current nonexistence of eclipses based on extensive photometry. Photographic and visual observations indicate cessation in the 1950–1951 season. Here we describe recent radial velocity work, modeling of published light curves, plans for further investigation and discuss implications of the cessation for system evolution.
CCD Photometry of the Eclipsing Binary HV 2274 in the Large Magellanic Cloud
Authors: Watson R.D. , West S.R.D. , Tobin William , Gilmore A.C.
Published: June 2019

B, V and Ic photometry of the eclipsing binary HV 2274, located in the LMC, was obtained with the CCD system at the Mount John University Observatory, Lake Tekapo, New Zealand during 1990. Over 100 data points were acquired in each filter to an estimated precision of 0.02 mag. The flat maxima evident in the light curves suggest that the system, which is currently classed as an interacting candidate, should probably be considered as a detached one. A revised orbital period based on the inclusion of current data is presented. Eclipse timings indicate an eccentric orbit. An apsidal period in the vicinity of 120 yr is likely.
Formation of the Solar 10830 Å Line
Authors: Avrett E. H. , Fontenla J. M. , Loeser R.
Published: June 2019

One-dimensional hydrostatic-equilibrium models are shown here for faint, average, and bright components of the quiet Sun, and for a plage region, describing in each case how the atmosphere is stratified through the photosphere, chromosphere, and transition region up to a temperature of 105 K. The observed coronal line radiation is assumed to be the inward incident radiation at the 105 K boundary. This coronal radiation penetrates into the upper chromosphere causing sufficient helium ionization to populate the lower level of the He I 10830 Å line, producing optically-thin absorption of the photospheric continuum at 10830 Å. The amount of absorption, which is proportional to the optical thickness of the upper chromosphere in the 10830 line, depends on 1) the strength of the coronal lines at wavelengths in the He I 504 Å ionizing continuum, and 2) the density and geometrical thickness of the upper chromosphere. The computed 10830 Å line is shown for the four atmospheric models and for three values of the coronal illumination. The calculated off-limb 10830 intensity distribution shows a minimum in the low chromosphere and a maximum at roughly 2000 km above the photosphere, in general agreement with observations, indicating that this is the predominant height of the transition region over most of the solar surface.
Submillimeter and Far Infrared Emission from Solar Flares
Authors: Petrosian Vahé
Published: June 2019

The mechanisms for emission in the submillimeter and far-infrared (1011 and 1013 Hz) regions by solar flares and expected fluxes at these frequencies are described and evaluated. These inferences are based on observations of flare emission at other frequencies and on models for these emissions. In the impulsive phase, non-thermal synchrotron emission by electrons responsible for > 10 MeV gamma-ray emission can give rise to significant radiation in the 1011 to 1013 Hz region from large flares. Free-free or thermal gyrosynchrotron from the hot plasma responsible for the gradual soft X-ray emission can produce significant radiation in the 1011 to 1013 Hz range. However, only radiation in the lower end of this range would have a brightness temperature exceeding the quiet sun brightness.
The Observed Spectrum of Solar Burst Continuum Emission in the Submillimeter Spectral Range
Authors: Correia E , Kaufmann P , Magun A
Published: June 2019

Observations of solar flares at high frequencies suggest that a considerable fraction of the events present flat or even increasing flux spectra at frequencies above 35 GHz. This imposes restrictions on the gyrosynchrotron emission mechanism and source parameters. We analysed a sample of 115 microwave events in order to investigate their spectra at peak flux. The analysis shows that about 50% of the sample exhibits a flat and 25% an increasing spectrum between 19 and 35 GHz. This class of events is significant and must be considered in the models. In order to better define the characteristics of this class of events it is necessary to carry out observations at frequencies well above 50 GHz with high time resolution and high sensitivity.
850 μm Observations of the 11 July 1991 Total Solar Eclipse
Authors: Ewell M. W. , Zirin H. , Jensen J. B. , Bastian T. S.
Published: June 2019

We present observations of the 11 July 1991 total solar eclipse made from the Caltech Submillimeter Observatory. The 850 μm limb is extended 3380±140 km above the visible limb, and there is a 10% brightening at the extreme limb. The measured limb height agrees with previous work at shorter and longer wavelengths. The run of limb heights with wavelength is well fit by a single electron density scale height. We argue that there is no need to invoke spicule geometry to explain the observations.
Observations of the 1991 Eclipse at 3.5 mm Wavelength
Authors: White S. M. , Kundu M. R.
Published: June 2019

We report preliminary results of the partial eclipse seen from the BIMA millimeter–wavelength interferometer in northern California. The use of an interferometer has many advantages over previous single–dish eclipse observations at 3 mm, and in particular it allows a quite different type of measurement of the height of the “3-mm limb” which is direct and precise: we find it to be 11.9″ ± 0.4″ above the optical limb.
IR Observations of the K and F Corona During the 1991 Eclipse
Authors: Kuhn J. R. , Lin H. , Lamy P. , Koutchmy S. , Smartt R. N.
Published: June 2019

The availability of relatively large format IR array detectors is incentive for reexamining the classic question of whether or not there are “dust rings” around the sun – a problem for which there are conflicting observational answers. The 1991 eclipse path included a high altitude observatory and provided a potentially ideal opportunity to study the infrared properties and dust content of the corona. Here we report results from an experiment conducted from Mauna Kea using a HgCdTe array detector sensitive to wavelengths between 1-2.5 μm. Surface brightness measurements in the H-band and polarization data in the J-band were obtained over a field-of-view of ±6 R⊙ while K-band images further extend to 15 R⊙ on the western side of the Sun. J-band polarization data and H and K-band surface brightness data clearly show the inhomogeneous structure in the K corona and the ecliptical flattening of the F corona. We see no evidence of a circumsolar, local dust corona (dust rings) out to 15 R⊙.
Infrared Coronal Observations at the 1991 Solar Eclipse
Authors: MacQueen R. M. , Hodapp K.-W. , Hall D. N. B.
Published: June 2019

Observations of the solar corona in a narrow band filter at wavelength 2.12 μm during the total solar eclipse of 11 July 1991 are described, and compared with results obtained by two observers during the eclipse of November 1966, and shortly thereafter. The lack of any observable signature of thermal emission in the 1991 results suggests that during 1966/67, the near-solar environs were subjected to a locally enhanced dust population, supplied by one or more sungrazer comets. Possible conditions which match the observational circumstances are discussed.
On the Coronal and Prominence Structures Observed at the Total Solar Eclipse of 11 July 1991
Authors: Suematsu Y. , Fukushima H. , Nishino Y.
Published: June 2019

Coronal images were taken in the light of the He I 10830 Å line, the 10000 Å continuum, and the Fe XIV 5303 Å line, with the aim of studying the thermal structure of the corona. In addition, spectroscopic observations were made in the violet wavelength region (3760-4060 Å) and near-infrared (10745-10835 Å), to obtain details of physical conditions of the corona, especially of its cool part. The data obtained do not show any distinct cool structures other than ordinary prominences. Some preliminary results concerning the corona and prominence structures are given.
The Infrared Granulation: Observations
Authors: Koutchmy Serge
Published: June 2019

High spatial resolution observations of the solar granulation up to 3 μm are possible on existing vacuum solar telescopes. They permit the analysis of the deepest photospheric layers near 1.7 μm. A high photometric accuracy is achieved using scanning techniques with a pinhole photometer; imaging methods are used for 2D-analysis. Statistically significant results on granulation, including power spectrum and histogram analysis, center-limb variations and lifetime analysis, are presented. Temperature fluctuations of periods near 5 minute are considered at 1.7 μm, as well as large-scale variations at the scale of the meso- and, especially, the super-granulation. We also discuss the “abnormal” granulation in magnetic regions and the umbral granulation in the cores of sunspots.
Atomic Physics of the 12-μm and Related Lines
Authors: Chang Edward S.
Published: June 2019

The 12 μm emission lines were unexpectedly detected about a decade ago. Great progress has been made in understanding the atomic physics underlying these high-l Rydberg transitions in Mg I and other atoms. In a magnetic field, their Landé g factor is shown to be unity. At disk center, the shift of the absorption trough relative to the emission peak is demonstrated to be due to the quadratic Stark Effect, permitting measurement of the photospheric electric field strengths. Other related lines of Mg I require accurate atomic fine structure data to interpret properly their complex line profiles. Related lines are found in the ATMOS spectra for C I, Na I, Al I, Si I, Ca I, and Fe I, in addition to H I.
The Formation of Infrared Rydberg Lines
Authors: Rutten Robert J. , Carlsson Mats
Published: June 2019

We review the formation of infrared solar spectral lines from highly excited levels in neutral atoms. The lines of Mg I and H I are the most interesting ones. We explain the NLTE processes by which they are affected and we study the sensitivity of the Mg I 12 μm lines to granulation and to flux tubes.
Theoretical Models of Magnetic Flux Tubes: Structure and Dynamics
Authors: Steiner O
Published: June 2019

Two types of model calculations for small scale magnetic flux tubes in the solar atmosphere are reviewed. In the first kind, one follows the temporal evolution governed by the complete set of the MHD and radiative transfer equations to a (quasi) stationary solution. From such a solution the continuum contrasts of a photospheric flux tube in the visible and in the infrared continuum at 1.6 μm have been computed and are briefly discussed. The second, more empirical type of method assumes the flux tubes to be in magnetohydrostatic equilibrium. It is computationally faster and more flexible and allows us to explore a wide range of parameters. Models and insights obtained from such parameter studies are discussed in some detail. These include an explanation for the peculiar variation of the area asymmetry of Stokes V profiles across the solar disk in terms of mass motions in the surroundings of magnetic flux tubes.

Furthermore, a two-dimensional model of the lower chromosphere that has been developed is presented. Emphasis is laid on the effect of thermal bifurcation of the lower chromosphere on the structure of the chromospheric magnetic field. If the cool carbon monoxide clouds, observed in the infrared, occupy the non-magnetic regions, the flux tubes expand very strongly and form a magnetic canopy with an almost horizontal base. This has consequences for the spatial distribution of the Ca II K spectral line emission.

Finally, some consideration is given to the formation and destruction of intense magnetic flux tubes in the solar photosphere. The formation is described as a consequence of the flux expulsion process that leads to a convective instability. A possible observational signature of this mechanism is proposed.
Near Infrared Imaging Magnetometry
Authors: Rabin Douglas
Published: June 2019

Infrared array detectors are a new and promising tool for investigating the properties of magnetic field concentrations in the solar photosphere. Array measurements provide large statistical samples of polarized line profiles and display the spatial organization of the magnetic field. The wavelength region near 1.6 μm has important advantages for magnetometry: spectral lines with magnetic sensitivites ranging from low to very high; low continuum opacity; high continuum flux; and the possibility of sub-arcsecond angular resolution with existing telescopes. Initial results have extended earlier work on the distribution of field strength and flux in plages and revealed new properties specifically connected with spatial structure. The quality and flexibility of near infrared magnetographs can be expected to improve rapidly.
Atomic Spectroscopy in the Infrared
Authors: Biémont E.
Published: June 2019

Some recent developments of atomic spectroscopy in the infrared spectral range are briefly summarized. Different topics of interest for astrophysics, such as term analysis, far infrared measurements, isotope shifts, hyperfine structure observations and transition probability determination, are briefly considered.
The Near-Infrared Capabilities of LEST
Authors: Engvold Oddbjørn
Published: June 2019

The Large Earth-based Solar Telescope (LEST) will be a powerful, next-generation telescope with unprecedented angular resolution, capable of highly accurate polarimetry of the Sun, covering the optical spectral range from about 300 nm into the near infrared to about 2.5 μm.

The telescope is a 2.4-m aperture, “polarization-free” concept based on a modified Gregorian optical system. A fast polarization modulator will be located close to the secondary focus of the system. An actively controlled NTT-type main mirror, a high precision pointing and tracking system, a helium-filled light path and a thin entrance window, together with an integrated adaptive optics system, will give the telescope near diffraction-limited performance in the visible. LEST will be sited on La Palma, in the Canary Islands, near the caldera rim on the Roque de los Muchachos Observatory, which often offers excellent seeing. A frequently occurring seeing parameter of ro = 15–20 cm in the visible will correspond to ro ≥ 1 m in the near IR.

The construction of LEST will begin in 1993, and the telescope is to be ready for “first light” in 1997. The telescope facility will accommodate a large number of focal plane instruments on a spacious instrument table. LEST will be made available for near-IR instrumentation from the start of its regular operation.
Near-IR Solar Coronal Observations with New-Technology Reflecting Coronographs
Authors: Smartt Raymond N. , Koutchmy Serge , NoëNs Jacques-Clair
Published: June 2019

Emission-line and K-coronal observations in the IR have the significant advantage of reduced sky brightness compared with the visible, while the effects of seeing are also reduced. Moreover, strong lines are available in the near-IR. Examples of the current capabilities of IR coronal observations using conventional Lyot coronagraphs are discussed briefly. Photometric measurements using the two IR lines of Fe XIII (10,747 Å and 10,798 Å), together with the Fe XIII 3,388 Å line, have provided a valuable electron-density diagnostic, but with low-angular-resolution. The 10,747 Å line has high intrinsic polarization. It has been used for extensive coronal magnetic field measurements, but only the direction of the field, and that with modest angular resolution, has been achieved due basically to flux limitations. Such studies suffer from the lack of high angular resolution and high photon flux. Moreover, the chromatic properties of a singlet objective lens preclude simultaneous observations at widely-differing wavelengths of the important inner coronal region. A coronagraph based on a mirror objective avoids such problems. Further, comparatively high-resolution and high-sensitivity arrays are now available with quantum efficiencies up to 90%. Reflecting coronagraphs with advanced arrays then provide the possibility of obtaining high-resolution images in the infrared to carry out a wide variety of studies crucial to many of the outstanding problems in coronal physics. A program for the development of reflecting coronagraphs is described briefly, with an emphasis on applications to IR coronal studies.
The Infrared Emission Features and Polycyclic Aromatic Hydrocarbons
Authors: Allamandola L. J.
Published: June 2019

The infrared evidence which supports the PAH hypothesis is briefly summarized. Rather than presenting a general discussion of these assignments, this paper focuses on the spectroscopic issues raised by recent observational and experimental developments. These issues include: the position and profile of the “1310” cm−1(“7.7” μm) feature, the position and intensities of the bands in the 910-710 cm−1(11-14 μm) region, the newly detected 1900 cm−1(5.3 μm) band, and the spatial and spectral variations in the 3000 cm−1(3 μm) region as well as in the 12 and 25 μm IRAS bands. It is concluded that the infrared evidence for interstellar PAHs and PAH-related species is compelling.
Dust Condensation in Stellar Outflows
Authors: Sedlmayr E.
Published: June 2019

The basic concepts of astrophysical dust formation are surveyed. The potentials, the limitations and the shortcomings of the various approaches are discussed.
An Upper Limit to the Intrinsic Anisotropy of the Microwave Background Radiation on a Scale of 7 Arc Minutes
Authors: Readhead A. C. S. , Lawrence C. R. , Myers S. T. , Sargent W. L. W.
Published: June 2019

For the last four years we have been engaged on a program to look for intrinsic variations in the Microwave Background Radiation (MBR) at the Owens Valley Radio Observatory (OVRO). We summarize here the results of this continuing search.
Evolution of Inhomogeneities in the Inflationary Universe -No Hair Theorem or Multi-Production of Universes?-
Authors: Sato Katsuhiko
Published: June 2019

Recent investigations on the evolution of the inhomogeneities in the inflationary universe are reviewed. 1) Strict cosmological no hair theorem does not hold, but the class of inhomogeneous universe which evolve to homogeneous de Sitter universe is finite, i.e, “weak cosmic no hair theorem” holds. 2) High density regions in the inhomogeneous universe evolve to wormholes provided that i) the size of the regions is greater than the horizon length, but smaller than a critical length which is the function of the density contrast, and ii) the density is three times higher than that of surrounding region. 3) If wormholes are formed copiously in the period of inflation, they evolve to causally disconnected “child- universes”. In this scenario, the universe we are now observing is one of the locally flat regions.
The Center for Astrophysics Redshift Survey
Authors: Huchra J. , Geller M. , de Lapparent V. , Burg R.
Published: June 2019

The first CfA Survey is now over 90% spectroscopically complete. Over 60% of all galaxies exhibit detectable emission lines. We have also completed five slices of the Center for Astrophysics (CfA) redshift survey extension. The geometry of the structures in the first slice persists; galaxies are distributed on thin surfaces of “bubble-like” structures. Empty regions or “voids” are common, come in a variety of sizes ranging up to 5,000 km s−1, and are underdense by factors of up to 5 w.r.t. the mean. These voids fill ∼ 80% of the volume of the local universe. Clusters of galaxies lie at the interstices of bubbles; some of the poor Abell clusters do not exist as “fingers” in redshift space. The surfaces are very thin with an average FWHM less than 500 km s−1 in redshift space (σ ∼ 200 to 250 km s−1).
The Large-Scale Distribution of Galaxies in the Southern Hemisphere
Authors: da Costa L. N. , Pellegrini P. S.
Published: June 2019

Here we present a first hand look at the space distribution of some 2000 galaxies from a recently completed redshift survey in the southern hemisphere. This sample extends to the southern skies the database of high-quality radial velocities of the CfA Redshift Survey, over a comparable volume of space.
Spiral Galaxies, Elliptical Galaxies and the Large-Scale Velocity Field Within 3500 km/s of the Local Group
Authors: Burstein David , Davies Roger L. , Dressler Alan , Faber S.M. , Lynden-Bell Donald , Terlevich Roberto , Wegner Gary
Published: June 2019

The peculiar motions for spiral galaxies and elliptical galaxies within V = 3500 km/s are compared to the model predictions of the mass concentration (MC) velocity field model of Lynden-Bell et al. The large-scale motions defined by over 600 galaxies from three independent sets of data (Aaronson et al.; de Vaucouleurs and Peters and elliptical galaxies) are in substantial agreement with this model.
A VLA Search for Cosmological H I
Authors: Noreau Louis , Hardy Eduardo
Published: June 2019

The recent commissioning of the 327 MHz (or P band) system at the NRAO Very Large Array opens the possibility for a new search for the 21 cm of H I redshifted to z ≈ 3.3 and perhaps observing the birth of galaxies as initially suggested by Sunyaev and Zel'dovich (1972, 1975). We present and discuss the results of our first observing run in January 1986, and report on the progress on our second run in April 1987.
A WSRT search for HI at z=3.35
Authors: de Bruyn A.G. , Wieringa M.H. , Katgert P. , Sancisi R.
Published: June 2019

The origin and evolution of the large-scale structures in the universe (from galaxies up to superclusters) forms one of the outstanding problems of present-day cosmology. Several attempts have been made to observe the precursors of the structures observed today, at epochs as early as possible. Results of a search for redshifted HI associated with “protoclusters” or “pancakes” were first reported by Davies et al. (1978). They used the Jodrell Bank Mark 1A-telescope at frequencies of 328 and 240 MHz (z=3.3 and 4.9 respectively). More recently Bebbington (1986) used the Cambridge 6C synthesis radio telescope for a search at 151 MHz (z=8.4). Both experiments gave negative results and raised the question whether the observations were matched to the “expected” properties of the structures that they looked for.
Superclustering and Motion of Galaxy Clusters*
Authors: Bahcall Neta A.
Published: June 2019

The evidence for the existence of very large scale structures, ∼ 100h−1 Mpc in size, as derived from the spatial distribution of clusters of galaxies is summarized. A “shell model” of galaxy clustering is described in which clusters of galaxies are located at shell intersections; the model yields results consistent with cluster observations. Detection of a ∼ 2000 km s−1 elongation in the redshift direction in the distribution of the clusters is also described. Possible causes of the effect are peculiar velocities of clusters on scales of 10–100h−1 Mpc and geometrical elongation of superclusters. If the effect is entirely due to the peculiar velocities of clusters, then superclusters have masses of order 1016,5M⊙ and may contain a larger amount of dark matter than previously anticipated.
The Pisces-Cetus Supercluster Complex
Authors: Tully R. Brent
Published: June 2019

It has been proposed in two recent articles by this author (Tully 1986, 1987) that rich clusters of galaxies tend to congregate in complexes involving of order 50 clusters over regions roughly 300 h75−1 Mpc across. The particular complex that we reside in has the additional remarkable property that the clusters are concentrated in a plane that is coincident with the plane described by the distribution of nearby galaxies. The extraordinary coincidence between the plane defined by rich clusters at a characteristic velocity of 15,000 km s−1 and the plane defined by galaxies at a characteristic velocity of 1500 km s−1 suggests a causal connection.
Two Questions about the Large-Scale Distribution of Galaxies
Authors: Geller Margaret J.
Published: June 2019

Observations and interpretation of the observations of the large-scale galaxy distribution prompt a number of profound questions to which we do not yet have clear answers. In this discussion I review two of the questions discussed during the symposium.
Galaxy Formation and Large-Scale Structures in a Two-Component Dark Matter Scenario
Authors: Umemura Masayuki
Published: June 2019

A universe dominated by both hot (HDM) and cold dark matter (CDM) is proposed. In this context, the new features for the formation of dwarf galaxies, Lyα clouds, galaxies, and large-scale structures are presented.
Biased Galaxy Formation and Dark Matter
Authors: Rees Martin J.
Published: June 2019

The clustering properties of galaxies are incompatible with a cosmological model with Ω = 1 unless the formation process for bright galaxies is ‘biased’ in the sense that their resultant distribution exaggerates the amplitude of large-scale inhomogeneities in the overall mass distribution. The mechanisms for such biasing are intimately connected with the nature of the dark matter. Various possibilities are summarised here.
Trinity Relations in the Universe
Authors: Suto Yasushi , Juskiewicz Roman , Silk Joseph
Published: June 2019

On large scales where linear perturbation theory is valid, the mean square values of the mass excess , the peculiar velocity ν and the microwave background anisotropy due to the Sachs-Wolfe effect, are simply expressed in terms of the present-day power spectrum of the density irregularity P(k):
Self-Similar Cosmological Models with a Cosmical Constant
Authors: Green Robin M. , Alexander David
Published: June 2019

The presence of the cosmical constant introduces a fundamental scale and prevents there being any simple self-symmetry. Henriksen, Emslie and Wesson (HEW), who studied spherically-symmetric models with a positive cosmical constant, have, however, demonstrated the possible existence of a self-similarity of the second kind and identified the similarity variable. They obtained interesting analytic solutions which are homogeneous in density, but not in pressure. We have extended this work and investigated the general behaviour of these cosmological models which possess a self-similarity of the second kind and in which the requirement of homogeneity is relaxed.
Solitons in Newtonian Gravity and Non-Linear Pancake Evolution
Authors: Götz Günter
Published: June 2019

It is shown that the solutions for the non-linear equations governing the motion of a stratified self-gravitating isothermal fluid are generated by a sine-Gordon equation (SG) which has well-known soliton solutions. Starting with two solutions of the SG-equation which are related via an auto-Baecklund-transformation, the physical quantities, density, velocity and gravitational potential are expressed in a parametric form in terms of characteristic coordinates. The zero-solution and the one-soliton solution of SG generate a single hump in the density moving with constant velocity. The typical non-linear feature is the relation between amplitude A and width (y = square of the speed of sound). The 1-soliton together with the 2-sollton solution of SG produces two moving humps in the density which come to rest asymptotically. As a result of the interaction the ratio amplitude/width is different from the corresponding ratio of the single soliton. Due to a certain exchange symmetry in the transformation procedure relating the SG to the gravity system it is possible to generate another solution out of the 2-soliton. Which represents a single hump moving on a homogeneous background. The remarkable property is that the density becomes infinite in a finite time depending on the amplitude. The “breather”-solutlon of SG produces a density distribution that represents two pulses colliding onto a central hump at rest which are separated from each other by a discontinuity in the density and the velocity field. These solutions may have applications to the non-linear evolution of flat structures arising in the process of galaxy formation.
The Center for Astrophysics Redshift Survey: Luminosity Function and Two-Point Correlation Function
Authors: de Lapparent Valérie , Geller Margaret J. , Huchra John P.
Published: June 2019

We compare the luminosity function and the two-point spatial correlation function for the two slices of the CfA redshift survey extension to mB(0) ≤ 15.5 [8h ≤ RA. ≤ 17h and 26.5° ≤ DEC. ≤ 38.5°], with those for the early survey limited to mB(0) ≤ 14.5 [bII ≥ 40°, and DEC. ≥ 0°]. The derived properties of the two samples agree within the errors. The parameters of the luminosity function are M* = −19.1±0.1 and α = −1.2±0.1 for the 15.5 sample, and M* = −19.3±0.1 and α = −1.1 ± 0.1 for the 14.5 sample. We use an inhomogeneity-independent method to calculate the luminosity function. The slopes of the correlation functions for the two samples are −1.5 ± 0.35, shallower than the canonical slope of −1.8. The correlation lengths are 7.5 ± 5h−1 Mpc, larger than the correlation length of 5h−1 Mpc matched to the theoretical models. Because of the 25% uncertainty in the mean density of the 15.5 sample, the correlation function is indeterminate on scales larger than ∼ 20h−1 Mpc.
A Search for a Vestigial Object in the Centre of a Cosmic Void
Authors: Ellis G.F.R. , Fairall A.P. , Maurellis A. , Matravers D.R.
Published: June 2019

The revelation that galaxies are apparently distributed on two dimensional surfaces that enclose bubble-like voids (de Lapparent et al. 1986, Fairall et al. 1985) has raised considerable interest. We have started an ongoing program to identify and confirm the existence of such structures - as extracted from our redshift database and others. We are concerned to measure how close to sphericity the bubbles fall and, in particular, to see how well their centres can be located.
Large-Scale Structure Among Abell Clusters and Comparisons to Models
Authors: Batuski David J. , Burns Jack O. , Melott Adrian
Published: June 2019

In a continuing redshift observation program, we have recently determined or confirmed the redshifts of 32 R ≥ 0 Abell clusters. With these data added to the previously measured cluster redshifts, there is now a sample of Abell clusters to z = 0.085 that is 92% complete in redshift measurements. The sample consists of 225 clusters in the North and South Galactic Caps, with latitude |b| > 30° to minimize obscuration effects. The longitude range 270° < l < 360° was also excluded for this sample because of an apparent large spur of galactic absorption.
Alignment of Clusters with Brightest Member Galaxies
Authors: Tucker Gregory S. , Peterson J. B.
Published: June 2019

We have obtained CCD images of the brightest elliptical galaxy in 27 clusters of galaxies with redshifts z < 0.1. For each galaxy we fitted elliptical isophotes to the galaxy image. We also measured the position angle of each cluster from the Palomar Observatory Sky Survey (POSS) prints. We find only marginal evidence for alignment of brightest cluster members (BCM) with their parent clusters, but we find that our CCD isophotes are well aligned with the POSS image.
Alignment Effects of Brightest Cluster Galaxies
Authors: Lambas D. G. , Peebles P. J. E. , Groth E. J.
Published: June 2019

We perform a test of reproducibility of the results of Argyres, et al. (A.J. 91, 3; 1986). Their conclusion is that there is marginal evidence for alignment of the brightest galaxies in rich Abell clusters in the northern galactic hemisphere with the surrounding large scale distribution of galaxies in the Lick map made by Seldner, et al. (A.J. 82, 249; 1977).
Angular Momentum Growth around Local Density Maxima
Authors: Heavens A. F. , Peacock J. A.
Published: June 2019

We have calculated the growth of angular momentum about local density maxima at early epochs. We find that high peaks experience higher torques than low peaks, counteracting the short collapse time during which the high peaks can acquire angular momentum. Which effect is dominant depends on the perturbation power spectrum: for power spectra characteristic of both cold dark matter and hot dark matter, the effects nearly cancel, and the total angular momentum acquired by a collapsing object is almost independent of the height of the peak. Furthermore, the distributions of angular momenta acquired by collapsing protosystems are extremely broad, for all power spectra, far exceeding any modest differences between peaks of different height.

These results indicate that it is not possible to account for the systematic differences in angular momentum properties of disk and elliptical galaxies simply by postulating that the latter arise from fluctuations of greater overdensity, contrary to some recent suggestions. The figure shows the probability distributions for the final angular momentum acquired by peaks of dimensionless height 1–4, for a power spectrum similar to cold dark matter. A fuller account of this work has been submitted to MNRAS.
Cosmic String Wakes and Large-Scale Structure
Authors: Stebbins A. , Veeraraghavan S. , Brandenberger R. , Silk J. , Turok N.
Published: June 2019

Cosmic Strings are one-dimensional topological defects that may be formed in the early universe during a phase transition, and which may be the source of all inhomogeneities in our universe. Their mass per unit length, μ, gives us a dimensionless parameter, μ6 ≡ 106Gμ/c2, which must be of order unity for strings to seed galaxy formation. Results to date from the ongoing CfA redshift survey suggest that galaxies are distributed on two-dimensional surfaces, whose typical separation is about 50h50−1 Mpc. The loop distribution is unlikely to imprint such large-scale patterns in the galaxy positions so we have examined whether this structure could be caused by infinite strings. Because an infinite string typically moves at a substantial fraction of the speed of light, it will leave behind a very large accretion wake in the ambient medium. Gravitational instablity causes these wakes to continue to accrete matter long after the string has moved elsewhere. These wakes form around the two-dimensional surfaces swept out by the long strings.
The Interaction of the Quasar PKS 0812+02 with the Surrounding Cluster of Galaxies
Authors: Guzzo L. , Danziger I.J. , Cristiani S. , Shaver P.A.
Published: June 2019

We present the results of long slit spectroscopy and deep imaging of the quasar PKS 0812+02 and its environment, obtained with the ESO 3.6m telescope using the ESO Faint Object Spectrograph and Camera (EFOSC) and the Boller and Chivens spectrograph.