bluuebunny/crossref_metadata_2025 huggingface dataset:
Milestones of Information Exchange in Astronomy from Prehistory to the Present
Authors:   Magda Vargha Konkoly Observatory
Published: July 2016

“That tho’ a Man were admitted into Heaven to view the wonderful Fabrick of the World, and the Beauty of the Stars, yet what would be otherwise be Rapture and Extasie would be but a melancholy Amazement if he had not a Friend to communicate it to.”

Attributed to Archytas by Christian Huygens

The Beginnigs. The origins of astronomy as a science can be traced back to the time when watchers of the sky first began to record the results of their observations and transmit them succeeding generations. The media used by these earliest astronomers were various, from great megalithic monuments like Stonehenge to the clay tablets of the Babylonian ephemerists and the papyrus rolls of the Egyptians.

Even in Antiquity such records were the foundation for the advance of astronomical knowledge. Thus the Chaldean Tables of the Babylonian had a great influence on the development of Greek astronomy. And in 130 B.C. Hipparchus discovered the precession of the equinoxes by comparing his own observations with those of Timocharis a century and a half earlier. Later even Copernicus himself used the results of Timocharis, Ptolemy, and al-Battani.
Earth at Night: An Image of the Nighttime Earth Based on Cloud-Free Satellite Photographs
Authors: Sullivan Woodruff T.
Published: July 2016

An image of the entire earth at nighttime is assembled for the first time. It consists of a mosaic of photographs, all taken at local midnight in the 400-1100 nm band, made by the Defense Meteorological Satellite Program over the period 1974-84. Photographs were selected for freedom from clouds, lack of moonlight, high sensitivity, and suitability to illustrate various temporal phenomena. The image primarily reveals activities of humankind such as urban street lighting, rangeland burning, slash-and-burn agriculture, natural gas burnoffs in oilfields, and squidding. Although light pollution in urban areas creates a striking map, at the same time it devastates astronomical observation and removes much of humankind from any familiarity with the night sky.
Pollution and Pollution Control in the Third World
Authors: Stock J. , Marin Z.
Published: July 2016

In developing countries in Latin America, Asia, and Africa, light pollution takes a particular aspect due to the social and economical situation. The official reluctance to solve unpopular problems combined with a generalized ignorance create a hostile climate for any campaign in favor of astronomical observatories or amateur associations. The tropical climate makes most energy savings measures unnecessary. Obsolete industrial installations make the application of particle output control difficult or impossible. The most important contribution to air pollution, however, comes from forest fires, some of them as a cheap clearing method, others as an expressions of political discontent. To this must be added that most countries do not have yet a legislature which would permit the imposition of pollution control.
A Radio Frequency Interference Survey of Central Ohio
Authors: Dixon Robert S. , Ellingson Steven W. , Koch Ronald J.
Published: July 2016

A long-term radio frequency interference monitoring program is now in progress at the Ohio State University Radio Observatory. Current observations encompass the 1-2 GHz band, measuring the signal strength in each 150 KHz subband. Preliminary results show many strong and persistent signals, and wide bands in which no signals are detected. Daily and weekly variations appear to be correlated with periods of maximum human activity such as “rush hours”. It may be that aircraft reflections are causing many of the signals to be received, and that airline schedules correlate with “rush hours”. The program is being upgraded to automatically measure the direction of arrival of each signal, as an aid to further identify it. This directional information will also be used in designing rolled edges and side shields for the co-located OSU Radio Telescope, to further reduce its vulnerability to RFI.
Radio Frequency Interference Survey over the 1.0 - 10.4 GHz Frequency Range at the Goldstone - Venus Tracking Station
Authors: Gulkis S. , Olsen E. T. , Klein M. J. , Jackson E. B.
Published: July 2016

Plans are currently being made to carry out a comprehensive, all-sky search for radio signals of extraterrestrial origin. The survey will employ the Goldstone tracking station near Barstow, California, and other sites in the northern and southern hemispheres. The principal parameters of this survey are given in Table 1. In preparation for this search, we have constructed a radio spectrum surveillance system (RSSS), and made a series of measurements of the RFI environment at the Goldstone-Venus tracking station. We describe in this paper the receiving system used (Crow et al. 1985), and the results of a low-sensitivity survey performed during February 16-24,1987.
Reduction of Interference in Observations with the Westerbork Synthesis Radio Telescope
Authors: Spoelstra T.A. Th.
Published: July 2016

Radio astronomical observations are increasingly affected by man-made interference of various kinds. Sophisticated software tools have to be developed to cope with interference effects in the data. A calibration procedure is described in which the effects of different categories of errors are separated. If this separation can be performed for interference effects.

Interference effects remaining in the data are erroneously interpreted as source structure by self-calibration techniques. This is due to the fact that self-calibration alone does not properly take into account this separation. Some results for the Westerbork Synthesis Radio Telescope are given.
The Legal Defense of Radio Astronomy
Authors: Ennis James G.
Published: July 2016

The purpose of this paper is to describe one program of the National Academy of Sciences’ Committee on Radio Frequencies (“CORF”). This program uses legal means to protect radio astronomy frequencies from radio interference.

CORF is composed of eminent scientists from the fields of radio astronomy, space research, remote sensing, meteorology, and wildlife tracking who use radio frequencies in conducting their research. CORF’s primary objective is to limit the level of harmful man-made interference in the bands used by these scientists as much as possible.
Pollution of Geophysical Sites
Authors: Kovalevsky J.
Published: July 2016

Astronomy in all wavelengths is not the only science to suffer from various causes of pollution. Sites in which geophysical research is being conducted are also in danger due to a variety of external causes. Among them, the following are described and discussed in addition to electromagnetic nuisances that are common to geophysicists and astronomers: heat production, magnetic disturbances, artificial vibrations in seismic observatories, chemical pollution in atmospheric studies, signal jamming, vandalism and site modifications around automatic stations.
Modeling mass loss from B[e] stars
Authors: Cassinelli J.P. , Schulte-Ladbeck R.E. , Poe C.H. , Abbott M.
Published: July 2016

It has been suggested by Zickgraf et al. (1986) that the outer atmosphere of some B[e] stars has a two-component structure: a fast, radiation-driven wind from the pole, and a dense, slow outflow from the equator. This is also die basic picture investigated by Poe, Friend, and Cassinelli (1989) (hereafter PFC) to explain the momentum problem associated with Wolf-Rayet stars. Here we apply the PFC multiforce wind theory to model the B[e] outflow phenomenon.
Luminous Blue Variables need not be blue
Authors: de Jager Cornells , van Genderen Arnout M.
Published: July 2016

A number of yellow and red super- and hypergiants show phenomena that are similar to those shown by Luminous Blue Variables. The LBV phenomenon may not be restricted to the blue part of the Hertzsprung-Russell diagram and the conventional name ‘S Dor variables’ seems more appropriate.
Mass loss from Luminous Blue Variables
Authors: Lamers Henny J. G. L. M.
Published: July 2016

Luminous Blue Variables (LBV’s) are losing mass at a rate which is higher than in normal stars of the same luminosity. This high mass loss is evident from the occurrence of P Cygni profiles in the visual spectrum, the large numbers of UV lines which are Doppler shifted or show P Cygni profiles and the large IR excess or radio free-free emission. Mass loss from LBV’s is strongly variable on a wide range of timescales from months to centuries and possibly even millenia. During these variations the mass loss may vary from values as low as 10-6to 10-5M⊙/yr, when the star is quiet, to outbursts of the type observed in P Cygni in AD 1600 and n Car in 1837 (for reviews see Davidson, 1987; Lamers, 1986, 1987).
Atmospheric dynamics of luminous stars
Authors: de Jager Cornells , Carpay Joost , de Koter Alex , Nieuwenhuijzen Hans , Schellekens Erik
Published: July 2016

A review is given of data and theories on the motion fields in super and hypergiants with special reference to LBV’s. We show that the radiative momentum flux is incapable of driving the episodical bursts of mass loss of these stars, and that there are several indications that the LBV-phenomenon is hydrodynamically driven. The sum of turbulent and radiative accelerations in the atmospheres of the most luminous stars compensates the gravitational acceleration for stars near the Humphreys-Davidson limit. This explains their atmospheric near-instability. The motion field in the atmosphere of a typical LBV consists mainly of low-order gravity waves, while acoustic waves are rapidly damped. These gravitation waves may be stochastic rather than coherently ordered. These stochastic pulsations are assumed to be responsible for the LBV phenomenon.
P Cygni: The star that started it all
Authors: Groot Mart de
Published: July 2016

P Cygni was discovered in 1600 AD during an outburst when it reached 3rd magnitude. After another outburst in 1655 the star is now showing irregular photometric variations with an amplitude inVof ~ 0.2 magnitude. Because of these variations and of its peculiar spectral characteristics, P Cygni has been classified as anything between supernova and W UMa system. However, its light curve is unlike that of any other star and P Cygni could well be considered the first discovered LBV.

Over the last three years an accurate photoelectric light curve has been put together.

It is based on observations made by a number of amateur and professional observers around the world and shows the following features:

+ Variations are irregular with maxima and minima every 1 - 2 months;

+ The brightness variations seem to show more scatter when the star is faint.
Dynamics of Groups around Interacting Double Ellipticals: Measuring Dark Matter Haloes
Authors: Quintana H.
Published: July 2016

Binary galaxies, as binary stars, are important to measure masses, as suggested by Page (1952). Because three orbit parameters are measurable for galaxies at one instant of time, severe uncertainties remain in the orbit and mass determinations. These uncertainties can partly be overcome by statistical studies of selected samples and/or n-body simulations. Close double galaxies (and isolated galaxies) could also be useful to estimate dynamical masses if we can find test particles around them.

Interacting elliptical pairs or dumb-bell galaxies are found with a large range, between 0-1200 km s-1, of relative radial velocities. Standard 2-body orbit calculations, highly uncertain due to projection factors, suggest for the largest velocity differences very large galaxy masses, if the systems are bound and stationary. However, recent n-body simulations model these binaries as galaxies captured from hyperbolic orbits, requiring masses of order a few times 1011M⊙) (Borne et al. 1988), but producing systems that are short lived.
Geometrical Parameters of E+S Pairs
Authors: Rampazzo Roberto , Sulentic Jack W.
Published: July 2016

• Clues Concerning Galaxy Formation. Local environmental conditions (i.e. density and angular momentum properties of protogalactic clouds) are thought to be factors affecting the ultimate morphology of a galaxy. The existence of significant numbers of mixed morphology (E/SO + S) pairs of galaxies would represent a direct challenge to this idea unless all early-type components are formed by mergers. We wish to isolate candidate E+S pairs for detailed study with several questions in mind:

a) Are most of the pairs true E+S systems OR, as the theory would suggest more morphologically concordant pairs involving primarily late-type or disky galaxies alone (i.e. misclassified lenticulars)?

b) Assuming that many of the pairs are E+S, do their properties differ in any way from E and S galaxies in the field?

c) Is their evidence that E galaxies in mixed pairs are preferentially merger products?
Multi-Color Imaging of Selected Southern Interacting Galaxies
Authors: Smith Eric P. , Hintzen Paul
Published: July 2016

We present preliminary results from a study of selected Arp-Madore Southern Hemisphere peculiar galaxies. Broadband CCD images (BVRI) of a subset of these galaxies allow us to study each galaxy’s optical morphology, color, and (in a crude manner) degree of nuclear activity, and to compare them with similar data we possess on other active galaxies. Many of these galaxies have optical morphologies closely resembling those of powerful radio galaxies (Smith and Heckman 1989), yet their radio emission is unremarkable. Accurate positions for subsequent spectroscopic studies have been determined along with broad band photometry and morphology studies. Detailed observations of these comparatively bright, low-redshift, well-resolved interacting systems should aid our understanding of the role interactions play in triggering galaxy activity. This work is the initial effort in a long term project to study the role played by the dynamics of the interaction in the production and manifestations of activity in galaxies, and the frequency of galaxy mergers.
Tidal distortions in pairs of early-type galaxies
Authors: Prugniel Ph. , Davoust E.
Published: July 2016

We are conducting an imaging survey of pairs of elliptical galaxies which has already produced interesting results. Some pairs present a common pattern of distortion interpreted in terms of tidal effects (Davoust and Prugniel, 1988; Prugniel et al., 1989). Other examples drawn from the literature (Borne and Hoessel, 1988; Colina and Pérez-Fournon, 1990) share the same morphology. This Poster presents new cases and lists the characteristics of 24 such systems.

Our pairs are drawn from a sample of binary and multiple galaxies which has in turn been extracted from the CGCG, UGC (Nilson, 1973) and VV (Vorontsov-Velyaminov, 1959) catalogues. This sample includes that of Karachentsev (1972). It contains 1800 pairs, among which 700 are S – S or mixed morphology pairs. We are working on the remainder to produce a sample of close physical pairs of elliptical galaxies (we also include bulge dominated S0’s since the morphological discrimination from ellipticals is often ambiguous, in particular for interacting galaxies).
Observational Properties of Compact Groups of Galaxies
Authors: Hickson Paul
Published: July 2016

Compact groups are small, relatively isolated, systems of galaxies with projected separations comparable to the diameters of the galaxies themselves. Two well-known examples are Stephan’s Quintet (Stephan, 1877) and Seyfert’s Sextet (Seyfert 1948a,b). In groups such as these, the apparent space density of galaxies approaches 106 Mpc-3, denser even than the cores of rich clusters. The apparent unlikeliness of the chance occurance of such tight groupings lead Ambartsumyan (1958, 1975) to conclude that compact groups must be physically dense systems. This view is supported by clear signs of galaxy interactions that are seen in many groups. Spectroscopic observations reveal that typical relative velocities of galaxies in the groups are comparable to their internal stellar velocities. This should be conducive to strong gravitational interactions – more so than in rich clusters, where galaxy velocities are typically much higher. This suggests that compact groups could be excellent “laboratories” in which to study galaxy interactions and their effects.
A Spiral-Like Disk of Ionized Gas in IC 1459: Signature of a Merging Collision?
Authors: Goudfrooij Paul , Nørgaard-Nielsen H.U. , Jørgensen H.E. , Hansen L. , de Jong T.
Published: July 2016

We report the discovery of a large (15 kpc diameter) Hα+[NII] emission-line disk in the elliptical galaxy IC 1459, showing weak spiral structure. The line flux peaks strongly at the nucleus and is more concentrated than the stellar continuum. The major axis of the disk of ionized gas coincides with that of the stellar body of the galaxy. The mass of the ionized gas is estimated to be ~ 1 105 M⊙, less than 1% of the total mass of gas present in IC 1459. The total gas mass of 4 107 M⊙ has been estimated from the dust mass derived from a broad-band colour index image and the IRAS data. We speculate that the presence of dust and gas in IC 1459 is a signature of a merger event.
The Double Nucleus Galaxies MKN 423 and MKN 739
Authors: Rafanelli Piero , Marziani Paolo
Published: July 2016

Long slit spectroscopy and imaging of Mkn 423 and Mkn 739 have been performed at the 2.2 m and 3.5 m telescopes of the Calar Alto Observatory using both CCD and photographic detectors. Low and medium resolution spectra (1.8Å, 3.5Å, 6.0Å) together with V images have permitted to demonstrate the merging nature of Mkn 423 and the double structure of the NLR of its Seyfert component. This last feature has been found also in the NLR of the Seyfert component of Mkn 739, a double system the two components of which are counterrotating.
The Polar-Ring Galaxies NGC 2685 and NGC 3808B (W 300)
Authors: Reshetnikov V. P. , Yakovleva V. A.
Published: July 2016

Polar-ring galaxies (PRG) are among the most interesting examples of interaction between galaxies. A PRG is a galaxy with an elongated main body surrounded by a ring (or a disk) of stars, gas, and dust rotating in a near-polar plane (Schweizer, Whitmore, and Rubin, 1983). Accretion of matter by a massive lenticular galaxy from either intergalactic medium or a companion galaxy is usually considered as an explanation of the observed structure of PRG. In the latter case there are two possibilities: (1) capture and merging of a neighbor galaxy, and (2) accretion of mass from a companion galaxy during a close encounter. Two PRG formation scenarios just mentioned are illustrated here by the results of our observations of the peculiar galaxies NGC 2685 and NGC 3808B.
Alignment of cD-Galaxies with their Surroundings
Authors: van Kampen Eelco , Rhee George
Published: July 2016

For a sample of 122 rich Abell clusters we find a strong correlation of the position angle (orientation) of the first-ranked galaxy and its parent cluster. This alignment effect is strongest for cD-galaxies. Formation scenarios for cD galaxies, like the merging scenario, must produce such a strong alignment effect. We show some N-body simulations done for this purpose.
Statistics of Associations Among IR Galaxies
Authors: Gallimore Jack F. , Keel William C.
Published: July 2016

In the course of expanding the search of Kleinmann et.al. (1988) for distant, infrared-luminous objects, we noticed (as is often remarked) that a large number of infrared-selected galaxies have close neighbors or show merger characteristics (e.g. tidal tails, distorted disks). Because the sample size is large (567 infrared galaxies and 2182 field galaxies), this sample is ideal for statistically examining the importance of interactions among infrared galaxies. In particular, we compare the nearest-neighbor distribution and the two-point correlation function of our sample with that of a control sample of field galaxies.
Cool Infalling Gas and its Interaction with the Hot Ism of Elliptical Galaxies
Authors: Sparks W.B. , Macchetto F.D.
Published: July 2016

We describe work leading to the suggestion that interaction between infalling cool gas and ambient hot, coronal plasma in elliptical galaxies is responsible for emission filaments, and might remove the need for large mass depositions in cooling flows. A test of the hypothesis is undertaken — the run of surface brightness with radius for the emission lines — and the prediction agrees well with the data.
Radio Line and Continuum Observations of Quasar-Galaxy Pairs and the Origin of Low Redshift Quasar Absorption Line Systems
Authors: Carilli C.L. , Gorkom J.H. van , Hauxthausen E.M. , Stocke J.T. , Salzer J.
Published: July 2016

There are a number of known quasars for which our line of sight to the high redshift quasar passes within a few Holmberg radii of a low redshift galaxy. In a few of these cases, spectra of the quasar reveal absorption by gas associated with the low redshift galaxy. A number of these pairs imply absorption by gas which lies well outside the optical disk of the associated galaxy, leading to models of galaxies with ‘halos’ or ‘disks’ of gas extending to large radii. We present observations of 4 such pairs. In three of the four cases, we find that the associated galaxy is highly disturbed, typically due to a gravitational interaction with a companion galaxy, while in the fourth case the absorption can be explained by clouds in the optical disk of the associated galaxy. We are led to an alternative hypothesis concerning the origin of the low redshift absorption line systems: the absorption is by gas clouds which have been gravitationally stripped from the associated galaxy. These galaxies are rapidly evolving, and should not be used as examples of absorption by clouds in halos of field spirals. We conclude by considering the role extended gas in interacting systems plays in the origin of higher redshift quasar absorption line systems.
Dynamical Interactions of Galaxy Pairs
Authors: Athanassoula E.
Published: July 2016

As the dynamics of galaxy interactions is too broad a subject to be discussed in any depth in a single review, I will concentrate only on a few topics proposed to me by the organisers. Since a pair should be “two things of a kind”, I will not discuss merging and merger remnants. I will also leave out discussions on M/L and hence halo mass determinations. Good reviews covering these subjects, and some of the subjects treated here, have been given by Toomre (1977), Tremaine (1981), White (1982, 1983a), van Albada (1988), Barnes (1990) and others. Here I will briefly review the dynamics of sinking satellites and the effect of companions on elliptical galaxies, then discuss recent work on interacting disk systems, and finally focus on my favourite interacting pair NGC 5194/5195.
An Experimental Study of Counter-Rotating Cores in Elliptical Galaxies
Authors: Miller R. H. , Roelofs G. R. , Smith B. F.
Published: July 2016

Recent observational studies (Franx and Illingworth 1987; Jedrzejewski and Schechter 1988; Bender 1988; Illingworth and Franx 1989) have shown that some elliptical galaxies have a small region near the center that rotates in the opposite direction from the outer parts of the galaxy. Often the rotation in the central part is much faster than that in the outer part. A few other galaxies show a small region near the center that rotates in the same di rection as the rest of the galaxy, but much faster. Either way, the part near the center that shows a strange pattern of rotation (the “core”) has been interpreted as a distinct dynamical subsystem. Very briefly, the observational data seem to be that (1) anomalies show up in rotation curves near the centers of some elliptical galaxies and that (2) galaxies with these strange rotational properties do not show a photometric signature: there are no noticeable bumps in the brightness profile and no unusual shapes of isophotal contours that would suggest an excess of matter concentrated near the center. No strong color variations have been reported. The puzzle is to learn what we can about elliptical galaxies in general, and about galaxies with strange central regions in particular, from these observational facts.
The Spiral-Compact Galaxy Pair AM2208-251: Computer Simulations Versus Observations
Authors: Klarić Mario , Byrd Gene G.
Published: July 2016

The system AM2208-251 is a roughly edge-on spiral extending east-west with a smaller round compact E system about 60 arcsec east of the spiral nucleus along the major axis of the spiral (Fig. la). Further details are in A Catalog of Southern Peculiar Galaxies and Associations (Arp and Madore 1987).
Energy and Angular Momentum Transfer in Binary Galaxies
Authors: Namboodiri P.M.S. , Kochhar R.K.
Published: July 2016

We have numerically studied tidal effects of a massive perturber on a satellite galaxy. The model consists of a spherical satellite galaxy and a point mass perturber and the encounter is non-penetrating. A wide range of density ratios and eccentricities of the relative orbits have been considered. The disruption of the satellite galaxy has been observed when the numerical value of the fractional change in the energy is greater than two. The changes in the energy and angular momentum show smooth variation in the case of unbound orbits and irregular variation in the bound orbit cases. It is shown that for a constant pericentric distance, increasing the density ratio decreases the tidal effects; and for a given density ratio an increase in the eccentricity decreases the tidal effects.
Simulation of Disk-Disk Encounters with Co-Moving Polar Grids
Authors: Salo Heikki
Published: July 2016

Two-grid simulation method combining advantages of both polar and cartesian mesh-codes is described. In addition to stellar component reacting solely to gravitational forces, gas component is included with dissipatively colliding particles. This allows fairly realistic simulation of planar encounters where both systems contain star+gas disks.
Observations and Models of Star Formation in the Tidal Features of Interacting Galaxies
Authors: Wallin John F. , Schombert James M. , Struck-Marcell Curtis
Published: July 2016

Multi-color surface photometry (BVri) is presented for the tidal features in a sample of interacting galaxies. Large color variations are found between the morphological components and within the individual components. The blue colors in the primary and the tidal features are most dramatic in B-V, and not in V- i indicating that star formation instead of metallicity or age dominates the colors. Color variations between components is larger in systems shortly after interaction begins and diminishes to a very low level in systems which are merged. Photometric models for interacting systems are presented which suggest that a weak burst of star formation in the tidal features could cause the observed color distributions. Dynamical models indicate that compression occurs during the development of tidal features causing an increase in the local density by a factor of between 1.5 and 5. Assuming this density increase can be related to the star formation rate by a Schmidt law, the density increases observed in the dynamical models may be responsible for the variations in color seen in some of the interacting systems. Limitations of the dynamical models are also discussed.
Tomographic Separation of Composite Spectra of O-Type Stars
Authors: Bagnuolo W.G. , Gies D.R.
Published: July 2016

We have analyzed UV photospheric lines of three O-type binaries (AO Cas, Plaskett’s Star, and 29 UW CMa) by means of tomographic and cross-correlation analyses, with the goal of estimating the physical properties of the individual stars. The tomographic techniques allowed us to estimate Teff and log g the luminosity ratio, and rotational velocities. The mass ratios were obtained from a cross-correlation technique, applied to spectral regions in which preliminary tomography shows the secondary has strong photospheric line features.
Extracting Velocities for Faint Secondaries
Authors: Cohen D. , Latham D.W.
Published: July 2016

When velocities can be determined for both members of a double-lined spectroscopic binary, then the mass ratio can be calculated immediately. With the goal of measuring velocities for faint secondaries in single-lined spectroscopic binaries, we have experimented with a technique of first subtracting the spectrum of the primary using synthetic spectra calculated from Kurucz model stellar atmospheres and then correlating to get the velocity of the secondary. For half a dozen of the single-lined spectroscopic binaries in the Carney-Latham survey of proper-motion stars we have been able to extract velocities for the secondaries and to solve for double-lined orbits.
Colliding Stellar Winds in O-type Close Binary Systems
Authors: Gies D.R. , Wiggs M.S.
Published: July 2016

In close binary systems of O-type stars, the individual stellar winds will collide between the stars to form shock fronts (Stevens et al. 1992). Binaries with equally luminous stars will have winds of comparable strength, and the shock will occur near the mid-plane between the stars, but in binaries of unequal luminosity, the interaction will occur along a bow shock wrapped around the star with the weaker wind. The presence of the shock region can be detected through excess X-ray emission (Chlebowski & Garmany 1990), and orbital phase-related variations in the UV P Cygni lines (Shore & Brown 1988) and optical emission lines (formed in high density regions of circumstellar gas).

We have begun a search for colliding winds through a study of the optical emission lines and UV P Cygni lines in four massive binaries, AO Cas (Gies & Wiggs 1991), Plaskett’s star = HD 47129 (Wiggs & Gies 1992), 29 UW CMa and ι Ori. The optical observations consist of high S/N spectra of the Hα and He I λ6678 region obtained with the University of Texas McDonald Observatory 2.1-m telescope and coudé Reticon system. The UV observations were culled from archival IUE high dispersion spectra of several P Cygni features (N V λ1240, Si IV λ1400, C IV λ1550).
Infrared Spectroscopy of Multiple Star Systems
Authors: Hinkle Kenneth H. , Ridgway Stephen T. , Fekel Francis C.
Published: July 2016

Up to this time infrared spectroscopy has been only occasionally used in binary star research due to both the insensitivity of infrared spectrographs and the difficulty of getting observing time on a limited number of spectrographs. However, infrared spectroscopy has a number of interesting applications in binary star research. We present an example of an application to the long-period symbiotic system CH Cyg. Due to the recent development of infrared arrays, infrared spectroscopy (1) is becoming available at a much larger number of telescopes and (2) in the 1.0-2.5 μm region is capable of going to limiting magnitudes nearly as faint as those reached by CCD’s.
Detection of Spectroscopic Triples
Authors: Mazeh Tsevi , Krymolowski Yuval , Latham David W.
Published: July 2016

Several binary stars detected by the Center for Astrophysics (CfA) radial-velocity surveys were found to be members of triple systems. We present two examples, each requires a different analysis to discover its multiplicity.

One example is G176-46, a double-lined halo star of the Carney & Latham (1987) high proper-motion survey. The secondary star (G176-46b) displays large radial velocity variations, in contrast with the primary (G176-46a), which is constant within the error limits. Figure 1 shows two cross correlations of the stellar spectra against the same calculated template taken at different times, which indicate that only the secondary’s peak changes its position. A similar variation was observed previously for ADS 8811 (Mazeh & Latham 1988).

We have found the secondary radial velocity to vary with a period of 10.44 days, and therefore conclude that Gl76-46b is a member of a short-period binary system. The orbital solution has an amplitude of 38 km s−1 and eccentricity of 0.05.
Observational Programme for Classical and CCD Photometry of Visual Double and Multiple Systems
Authors: Oblak E. , Lampens P.
Published: July 2016

Complementary accurate photometric data with astrophysical content are needed for a well-chosen sample of binaries and multiple systems for which good-quality astrometric data already exist or will soon be available. The observational programme, started in the context of the European Network of Laboratories “Visual Double Stars” (Oblak et al. 1992), is therefore based on samples extracted from the “Catalogue des Composantes d’Etoiles Doubles et Multiples” (CCDM, Dommanget, 1989) and reported in Annex 1 (Double and Multiple Systems) of the HIPPARCOS Input Catalogue (C. Turon et al. 1992).

Systems with components in the HIPPARCOS Input Catalogue are selected for which the present photometric information is poor, i.e. not all components have been observed or they have colour indices and/or magnitudes of insufficient quality for extraction of astrophysical quantities (Figure 1).

Observations, performed in various observatories located in both hemispheres, must yield both classical and CCD photometric campaigns.
UBV CCD Photometry of “Close” Visual Double Stars
Authors: Van Dessel E. , Sinachopoulos D. , Prado P.
Published: July 2016

We use the CCD cameras of the 61-cm UTSO and the 90-cm Dutch telescopes of the Las Campanas and European Southern Observatories respectively in order to perform UBV photometry of visual double stars.

Our sample contains southern visual binaries with A–type (470 pairs) and G–type primaries (170 pairs), which have angular separations mainly between 1″.5 and 5″. The double stars of our sample have been selected from the WDS according to their astrophysical interest and the technological limits of contemporary CCDs.
Stellar Masses from Double Star Observations with the Mark III Interferometer
Authors: Armstrong J.T.
Published: July 2016

By improving on the angular resolution possible with conventional telescopes, speckle interferometry has been adding to the list of known masses, resolving binaries with separations of 30 mas. Interferometry with separate apertures offers the possibility of going to much higher resolution.

The Mark III Optical Interferometer on Mt. Wilson has been used for astrometry, for stellar diameter measurements, and for binary observations since routine operations began in late 1988. The fringe visibilty calibration uncertainty is ~1% for m < 4m at λ800 nm with good seeing, so that both binary components can be detected when the magnitude difference is 3.5m to 4m.

From Mark III data, masses of eight stars have been determined. The most precise determination is for the components of the ϕ Cygni system: 2.545 ± 0.085 and 2.445 ± 0.081 M⊙. To improve on this measurement, more precise spectroscopic data are needed, as is the case for most of the systems for which we have orbits or preliminary orbits.

The NRL/USNO Optical Interferometer Project is currently designing two more capable instruments: a four–element system for astrometric observations, and a six–element system for imaging. The ultimate 430-m maximum baseline and 35-cm apertures of the imaging interferometer will allow observations to 8th to 10th mag and resolution of binary components separated by as little as ≈ 200 µas.
Simultaneous Spectroscopic and Interferometric Measurements of Binaries with the GI2T
Authors: Mourard D. , Bonneau D. , Blazit A. , Labeyrie A. , Morand F. , Percheron I. , Tallon–Bosc I. , Vakili F.
Published: July 2016

The “Grand Interféromètre à deux Télescopes” (GI2T) is presently the largest operational interferometer operating at visible wavelengths (Labeyrie et al. 1986, Mourard et al. 1991). With two telescopes of 1.5-m aperture and baselines reaching 65 m in the North–South direction, it gives stellar spectra containing interference fringes, which provide high angular resolution measurements in the range of one milliarcsecond.

The GI2T optical combination follows the Michelson principle of output pupil remapping to preserve a constant fringe spacing on the detector for stable and economical spatial sampling. The stellar light is dispersed in order to study the fringes parameters simultaneously with the spectral information. The direction of dispersion is perpendicular to that of the recombined pupils. Due to atmospheric turbulence the instantaneous images contain about 100 speckles. To freeze the atmospheric turbulence a temporal resolution of at least 10 milliseconds is needed.
Interferometric Imaging of Nearby Low–Mass Spectroscopic Binaries. I. KPNO Observations
Authors: Duquennoy A. , Christou J. , Mariotti J.-M. , Mayor M. , Morbey C. , Perrier C. , Probst R. , Tessier E. , Ridgway S.
Published: July 2016

We present a preliminary report on radial–velocity and infrared interferometric observations, with emphasis on the newly resolved nearby sources Gl 609.2 and Gl 804. We briefly discuss their low–mass companions, their luminosities, and their individual masses inferred from the combined solution of their spectroscopic and visual orbits.
A Preliminary Speckle Orbit of the Old Disk Population Star HR 1071
Authors: McAlister H.A. , Hartkopf W.I. , Mason B.D.
Published: July 2016

The F7V star HR 1071 has attracted little individual attention in the literature. Eggen (1972, 1973) included HR 1071 among some 250 metal–deficient stars, of which 20 are halo population objects, in a photometric calibration of their absolute magnitudes. HR 1071 stands out in Eggen’s sample as a disk population star of extreme space velocity compared with stars of similar moderate metal deficiency, having (U, V, W) = (−60, −39, +8) km s−1. Kinematically, HR 1071 would be considered an old disk population star although this classification would be strengthened if the metallicity were lower. More recently, Balachandran (1990, hereafter BAL) took Eggen’s (1973) sample as a basis for studying the possible effects of rotational breaking on Li depletion in old–disk population F stars. HR 1071 possesses the fifth lowest Li abundance (the Li λ6707 Å equivalent width was less than 1 mÅ) and the third lowest observed rotational velocity of 5 km s−1 in BAL’s sample.
Occultation Binaries Observed from KPNO: Astrometry Corrections Using the Observed Rate of Lunar Motion
Authors: Schmidtke Paul C.
Published: July 2016

Lunar occultation data often are reduced by means of a multiparameter least-squares fitting routine. For binary stars the minimum number of free parameters is five: the time of geometric occultation for each star, the intensity of each component, and the background intensity. From these values the magnitude difference between components can be calculated as well as the angular separation of the binary in the direction perpendicular to the lunar limb (i.e. the lunar position angle). If the observed rate of motion of the lunar limb can be determined as an additional free parameter, then the difference between observed and predicted values can be interpreted in terms of a local lunar slope. Therefore, in principal the observed rate of motion can be used to correct the vector separation — both angular separation and direction — of the binary. In this paper four occultation binaries observed from KPNO are examined to determine whether binary-star astrometry can be improved using these corrections.
Speckle Interferometry at the U. S. Naval Observatory
Authors: Worley Charles E. , Douglass Geoffrey G.
Published: July 2016

A new speckle interferometer began operation with the 66-cm refractor in Oct. 1990. The interferometer is an improved version of the one operated by CHARA at Georgia State University. We describe the instrument, its calibration, and first observational results.
A Four Star Photometer
Authors: Valtier J.C. , Contel J.M. Le , Antonelli P. , Michel P. , Sareyan J.P.
Published: July 2016

A new photometer is presently being developed at the O.C.A. Observatory. It consists of four arms and a CCD camera situated in the focal plane of the telescope. Each arm can move in both directions and support a diaphragm and a liquid optic guide that directs the light to a photomultiplier. The simultaneous acquisition of the four signals enables to obtain magnitude differences between the objects in real time. A typical use of this photometer is to observe at the same time one or two variables, comparison stars and the sky background.
Instantaneous determination of a variable extinction coefficient in photoelectric photometry
Authors: Poretti E. , Zerbi F.
Published: July 2016

Observational evidence was found that even in good photometric sites the extinction coefficient can display large variations during a night. The authors propose a method to determine instantaneous values of the extinction coefficient: it is based on the knowledge of the extra-atmosphere instrumental magnitude m0 for a reference star. An analytical procedure is proposed to determine a reliable value for m0 and results are very satisfactory.
Extended Strömgren Photometry with CCD’s
Authors: Anthony-Twarog B.J. , Twarog B.A.
Published: July 2016

CCD’s have made possible the extension of intermediate-band photometric systems, including the Strömgren uvby system, to larger, fainter and cooler stars, with successful applications in old disk and globular clusters. Some of the applications in globular clusters demonstrate the ability to remove foreground stars from photometric diagrams and have enabled a re-evaluation of the evolutionary correction needed for distance modulus determination for metal-poor stars. We have developed an additional index based on measurement of the Ca II H and K lines which retains sensitivity to metallicity changes for extremely metal-poor stars. Finally, we are testing the utility of CCD H/β photometry in the unusual and old open cluster Melotte 66.
Photometry from Space
Authors: Bless R.C. , Taylor M.
Published: July 2016

After a brief review of the traditional opportunities as well as the problems of doing photometry from space vehicles over a wide variety of wavelength regimes, several topics will be discussed. These include the factors associated with various types of spacecraft orbits (for example, near-earth, geosynchronous, planetary cruise) and with the different kinds of vehicles and platforms used (expendable, shuttle attached payloads, permanent stations, multi-purpose spacecraft, small and large projects). Since ground-based capabilities are constantly improving and expanding, it is necessary to assess those that might compete with space-based photometry. Finally, the present state of space observations as they pertain to “classical,” high precision, high speed and multi-object photometry will be reviewed; possibilities for the future will be addressed briefly.
Recent Results from the High Speed Photometer
Authors: Taylor M. , Bless R.C. , Nelson M. , Percival J. , Bosh A. , Cooke M. , Elliot J. , van Citters W. , Dolan J. , Biggs J. , Wood J. , Robinson E.
Published: July 2016

One of the first stellar photometry programs completed with the High Speed Photometer (HSP) on the Hubble Space Telescope (HST) was visual and ultraviolet observations of the Crab pulsar. We obtained continuous observations on four consecutive days using a visual filter (4000 - 7000 Å) and an additional observation, approximately two months later, using an ultraviolet filter (1600 - 3000 Å). Each observation has a time resolution of 10.7 μsec and spans approximately 30 minutes in duration. In addition to the observations made with the HSP, contemporaneous UBVR observations were also made at Jodrell Bank and McDonald Observatory. Some of the more prominent results include the following: 1) the main pulse arrival time is the same in the UV as it is in the optical and the radio regions of the spectrum, 2) there is essentially no difference in the shape of the optical pulse from one observation to the next, 3) the “flatness” of the peak of the main pulse suggests that the main pulse has been resolved in time, and 4) in accordance with the trend of observations from the radio to infrared wavelengths, the main pulse is slightly narrower in the UV than in the optical.

A second HSP science observing program was a long-term program to monitor the eclipsing dwarf nova, Z Chamaeleontis (Porb = 107 minutes). We obtained a total of 42 observations of Z Cha in the UV (1120 - 1580 Å) each with a duration of approximately 45 minutes and separated by approximately three days. Although the majority of the observations cover the eclipse of the white dwarf and hot spot, a few observations were obtained outside-of-eclipse in order to obtain the complete light curve. During the course of this program, Z Cha underwent two “normal” outbursts in which the shape of the light curve changed dramatically. We will present a comparison of the light curve in quiescence with that during a “normal” outburst and quantify such geometrical and physical parameters as temperature and size of the white dwarf, hot spot, and accretion disk.
2D Simulations of Deflagrations in White Dwarfs
Authors: Livne Eli
Published: July 2016

The convective deflagration mechanism in white dwarfs became widely used to explain Type la Supernovae (SNIa) due the success of a single model, namely model W7 of Nomoto et al. (1984). Problems concerning the deflagration model were discussed by Sutherland & Wheeler (1984), Nomoto et al. (1984), Woosley & Weaver (1986), Woosley (1990), Khokhlov (1991a) and others. The main question however is still: does the deflagration model have any hydrodynamical basis, or, could the assumed Rayleigh Taylor instability accelerate the flame to the required speed?
Hydrodynamics and Theoretical Light Curves of SNe II
Authors: Imshennik V. S. , Blinnikov S. I.
Published: July 2016

We discuss a new scenario for the production of SNII explosion and present the results of numerical modelling studies of SNe II light curves which are being done in our group.
Historical Supernovae and Supernova Remnants
Authors: Wang Zhenru
Published: July 2016

The oldest historical supernova (SN), recorded by ancient Chinese in 14th Century B.C. on pieces of tortoise shells or bones, is identified with the aid of modern space γ-ray observations. Hard X-rays with energy up to 20 keV were observed from IC 443 by the X-ray satellite Ginga. We infer from these observations the age of IC 443 is ∼ 1000 — 1400 yrs. The result supports the hypothesis that IC 443 is the remnant of the historical SN 837 that occurred during the Tang Dynasty.

The association between the supernova remnant (SNR) CTB 80 and SN 1408 has been hotly debated for about ten years and is briefly reviewed and discussed here. A new picture is presented to explain this association.

High energy emission from historical SNRs can persist in a multiphase interstellar medium (ISM). As a result, the study of the relationship between SNRs and ancient guest stars has gained new vitality.
The Discovery of Double Stars at Occultations
Authors: Evans David S.
Published: July 2016

When systematic photoelectric observations of occultations were started some dozen years ago it was realised that they yielded a significant crop of double star discoveries and observations. The limitations of the method were well recognised: only about ten percent of the area of the sky would ever be available and one could not choose which stars to be observed. Moreover the data obtained from a successful observation of a double star are less comprehensive than the normal visual observation. The result is the vector separation or the true separation projected along a line perpendicular to the actual lunar limb, that is the position angle of the point of occultation modified by the slope of the limb at that point.
Photoelectric Observations of Stellar Occultations at Abastumani Observatory
Authors: Korol A. N. , Dzhapiashvili V. P.
Published: July 2016

The occultations observations are traditional at Abastumani Observatory. About 3 years ago the work was started on the development of the observational equipment for measuring different characteristics of various events under investigations with as high efficiency as possible, but using relatively small aperture telescope. The program is in progress, so, at present, the following pulse-counting system is built and put into operation.