bluuebunny/crossref_metadata_2025 huggingface dataset:
The Environmental Condition (Light Pollution and Radio Interference) of Chinese Astronomical Observatories, Past, Present, and Future
Authors: Yang Jiang Shi
Published: July 2016

Although China is a backward developing country, the population of many big cities has increased more than 100 percent since 1950. The light and smoke pollution for Shanghai Observatory and Purple Mountain Observatory is very serious, and in Kunming, for Yunnan Observatory, is also quite a problem. Now the only one where the observational condition is still quite good is the optical station of the Beijing Observatory, in XingLong County, Hebei Province. For the future, we plan to do some testing work on the Tibet plateau, where the population if very low, so there is no light pollution at all.
Note on Mercury Light Pollution in Spectroscopic Observations
Authors: Changchun Huang
Published: July 2016

Mercury light pollution has appeared in our spectroscopic observations of the Comet 1980u made at the Observatoire de Haute Provence and spectroscopic observations of the Nova Andromeda 1986 made at the Purple Mountain Observatory. On spectra of an exposure of about one hour of the comet obtained at the 1.93m telescope of the OHP using the image tube spectrograph D (dispersion of 92 A/mm), the lines 4358, 4047 of Hgl are very strong. In the case of the nova, these lines are quite noticeable on spectra of exposure of 3 hours obtained at the 0.6m telescope of the PMO with the Marly-Nanjing spectrograph (dispersion 40 A/mm).
Economics of Light Pollution
Authors: Hunter Tim B. , Crawford David L.
Published: July 2016

Little attention has been directed toward the environmental and economic costs of light pollution. We estimate that 2.5 percent of the total United States electricity production is expended on nighttime outdoor lighting. About 30 percent of all outdoor nighttime lighting ends up in the night sky. This is equivalent to 17.4 billion kilowatt-hours of electricity, more than the individual electrical production of many countries, including Chile, Cuba, Hungary, Ireland, Indonesia, Israel, Libya, Peru, Syria, or Vietnam. About one half of light pollution arises from direct upward lighting and one half from reflections off the ground and buildings. Light pollution directly costs the country at least a billion dollars a year in unnecessary electricity charges, in addition to the associated environmental harm from the mining and burning of fossil fuels to generate this wasted electricity. The equivalent of 8.2 million tons of coal (or 30 million barrels of oil) are burned annually in the United States simply to light up the night sky. The proper use of full cut-off shielding, timers, and appropriate light levels, if widely instituted, could reduce the overall urban sky glow by at least a factor of four in the next few decades.
The Impact of Light Pollution on Amateur Astronomy and Public Awareness of the Night Sky
Authors: Chester Geoffrey
Published: July 2016

With the growing expansion of urban areas and their associated “domes” of artificial illumination, amateur astronomers have been forced to change many of their observing habits. This is reflected in the instruments today’s amateurs are using: highly portable telescopes of mostly commercial origin. Amateurs must travel further into the field to find dark skies, and this makes the hobby more discouraging. By discouraging the amateurs, an important education resource is lost to the public.
The International Dark-Sky Association, Inc.
Authors: Hunter Tim B. , Crawford David L. , Howell Libby , Knauss Daniel G.
Published: July 2016

The International Dark-Sky Association, Inc. (or IDA, Inc.) is a new tax-exempt, non-profit corporation formed to serve the public and the amateur and professional astronomer communities by providing information, education, and research on light pollution and related topics. IDA will share knowledge of the issue on a local, national, and international basis and will assist with members’ problems. It was organized for the purpose of preserving dark skies for astronomy and for the general public. Solutions to the problem of light pollution will, at the same time, also promote maximum effectiveness for all outdoor lighting and will conserve natural resources.
An Overview of the Space Debris Issue
Authors: Kessler Donald J.
Published: July 2016

The amount of man-made debris in orbit is now sufficient to create a flux in some regions of low Earth orbit which exceeds the flux of natural meteoroids. The primary source for this debris is from the fragmentation, or disintegration, of spacecraft. Future debris can be expected to result from random collisions between orbiting objects. This debris will require additional shielding for some spacecraft, will contaminate some types of meteoroid experiments, and contaminate some types of astronomical observations. Steps are being taken to minimize the accumulation of future debris.
Threat to Astronomy by Space Art
Authors: Murdin Paul
Published: July 2016

The Light Ring, proposed as a celebration of the centenary of the Eiffel Tower, and now withdrawn by its sponsors, demonstrated the feasibility to launch relatively inexpensive satellites which subtend an appreciable solid angle as seen from earth. Other satellites in the competition organized by the Eiffel Tower proposed configurations under the name of Space Art which could unacceptably increase the night sky background. Satellites of this nature, launched for noble but essentially frivolous motives, pose a threat to optical astronomy.
Space Object Traffic Control
Authors: Knowles Stephen H.
Published: July 2016

The task of avoiding collisions between orbiting objects requires more than a statistical description of the objects’ positions. The paper describes the general procedures used for such cataloging, together with an indication of the accuracy required for orbital collision avoidance.
The Nature of Radio Interference and Some Lines of Defense
Authors: Fisher J. Richard
Published: July 2016

As competition for radio spectrum space continues to increase, radio astronomers can expect to put more technical effort into ways of observing in the presence of interference. Much of the spectrum outside of exclusive radio astronomy frequency bands will continue to be available to the science if receivers and antennas are designed to make efficient use of times, frequencies, directions, and coherence envelopes that do not contain sources of interference. The paper outlines the state of the art in antenna sidelobe reduction, high dynamic range spectrometers, and receiver designs for handling large signals. Techniques for excising pulsed interference on very short timescales and a few thoughts on signal canceling techniques are discussed.
Interference Problems and Radio Astronomy in the UK
Authors: Cohen R. J.
Published: July 2016

The radio regulations often require frequency bands to be shared between radio astronomy and services which transmit. This poses severe problems in a small island, given the sensitivity of radio astronomy receivers. The survival of radio astronomy in these circumstances depends on wide awareness of the problems. Some of the current sharing problems in the UK are discussed.
Radio Astronomy at WARC MOB-87
Authors: Gergely T. E.
Published: July 2016

The World Administrative Radio Conference for the Mobile Services (WARC Mob-87), held in Geneva in September-October, 1987, took several actions that will have an impact on radio astronomy. Worldwide frequency allocations were made for the Radiodetermination Satellite Service (RDSS) in the 1610 to 1626.5 MHz band. The secondary allocation to radio astronomy in this band has received strong protection, however. The 1660 to 1660.5 MHz band, which radio astronomy shared on a primary basis with the Aeronautical Mobile Satellite Service has been reallocated to the Land Mobile Satellite Service, shared with radio astronomy on a similar basis. The impact that this reallocation will have on radio astronomy is not clear. Since the Radioastronomy Service is primary in the band, Mobile Satellite Systems that evolve will have to provide adequate protection. Perhaps most significantly, WARC Mob-87 recommended that a conference be convened to reallocate all bands in the 1 to 3 GHz range, no later than in 1992. Several other conferences dealing with particular services have been proposed. At first glance, some of these some of these proposals may not appear to have an impact on radio astronomy. They will, however, increase the pressure on the entire radio spectrum. Finally, it is highly likely that a General WARC will be proposed to be held before the end of the 1990s. The radio astronomy community will have to prepare for these conferences.
The role of rotation in Luminous Blue Variables
Authors: Sreenivasan S.R. , Wilson W.J.F.
Published: July 2016

We demonstrate that differential rotation plays a significant role in the essential features of LBV’s, among other types of objects.
On the interpretation of emission wings of balmer lines in LBV’s
Authors: Hubeny Ivan , Leitherer Claus
Published: July 2016

The optical spectra of Luminous Blue Variables (LBV’s) are characterized by strong Balraer emission lines. In many cases, the narrow emission component (FWHM ≤ 300 km/sec) shows extended emission wings reaching up to -1000 km/sec. These wings are generally attributed to electron scattering of line photons in the dense stellar wind (Bernat and Lambert 1978). In this paper we discuss an alternative mechanism which may partly contribute to the observed line wings.
Far-infrared circumstellar debris shells: Clues to the evolution of massive stars?
Authors: Stencel R.E. , Garmany C.D.
Published: July 2016

A survey of the infrared properties of late-type supergiant stars, using the IRAS database, reveals that about 25% of the stars possess resolved, extended circumstellar shells. These shells are typically several arc minutes in apparent size and therefore on the scale of parsecs at the source. Furthermore, among the resolved sources, there is an inverse correlation between physical size of the infrared shell and B-V color, suggesting that these shells are formed while the objects are red supergiants, but continue to expand ballistically, while the star evolves blueward from that extreme. These shells may be the material swept up into ring nebulae when the central star develops a fast wind.
Pairs of Galaxies in Low Density Regions of a Combined Redshift Catalog
Authors: Charlton Jane C. , Salpeter Edwin E.
Published: July 2016

The distributions of projected separations and radial velocity differences of pairs of galaxies in the CfA and SSRS redshift catalogs are examined. We focus on pairs that fall in low density environments rather than in clusters or large groups. The projected separation distribution is nearly flat, while uncorrelated galaxies would have given one linearly rising with rp. There is no break in this curve even below 50 kpc, the minimum halo size consistent with measured galaxy rotation curves. The significant number of pairs at small separations is inconsistent with the N-body result that galaxies with overlapping halos will rapidly merge, unless there are significant amounts of matter distributed out to a few hundred kpc of the galaxies. This dark matter may either be in distinct halos or more loosely distributed. Large halos would allow pairs at initially large separations to head toward merger, replenishing the distribution at small separations. In the context of this model, we estimate that roughly 10 — 25% of these low density galaxies are the product of a merger, compared with the elliptical / S0 fraction of 18%, observed in low density regions of the sample.
Multi-Waveband Observations of Colliding Galaxies
Authors: Appleton P.N. , Robson E.I. , Schombert J. M.
Published: July 2016

Colliding galaxies represent a major challenge to both theorists and observers because of the large variety of phenomina which are expected to come into play during the interaction. Strong gravitational fluctuations may drive non-linear waves and instabilities throughout the stars and gas leading to enhanced star formation, nuclear activity and ultimately a mixing of the morphological components of the original galaxies. One relatively uncomplicated class of colliding galaxy where stellar waves play an important role in star formation are “ring” galaxies. Ring galaxies are probably formed when a companion galaxy passes through the centre of a disk system driving circular waves through the disk (Lynds and Toomre 1976, Toomre 1978, Struck-Marcell 1990). Off-centre collisions can generate non-circular waves and can be loosely described as banana-shaped although they may exhibit more complex forms as the waves expand into the disk (See also Struck-Marcell; this volume). The propagation of such stellar and gaseous waves through the disk leads to enhanced star formation (e.g. Appleton and Struck-Marcell 1987a; Jeske 1986) and provides a unique probe of the response of the ISM to a propagating wave (See Appleton and Struck-Marcell 1987b).
Isolated Galaxies, Pairs and Groups of Galaxies
Authors: Kuneva I. , Kalinkov M.
Published: July 2016

We searched for isolated galaxies, pairs and groups of galaxies in the CfA survey (Huchra et al. 1983). It was assumed that the distances to galaxies are given by R = V/H0, where H0 = 100 km s−1 Mpc−1 and R> 6 Mpc.
Hidden Interaction in SBO galaxies
Authors: Galletta G. , Bettoni D. , Fasano G. , Oosterloo T.
Published: July 2016

Galaxies, like plants, show a large variety of grafts: an individual of some type connects physically with a neighborhood of same or different type. The effects of these interactions between galaxies have a broad range of morphologies depending, among other quantities, on the distance of the closest approach between systems and the relative size of the two galaxies. A sketch of the possible situations is shown in Table 1. This ‘botanical’ classification is just indicative, because the effects of interactions can be notable also at relatively large separations, when additional conditions are met: as for example low density of the interacting systems or the presence of intra-cluster gas. In spite of the large variety of encounters and effects, in the literature the same terms are often used to refer to different types of interactions.
New Data on the Peculiar Galaxy MRK 273
Authors: Asatrian A. S. , Petrosian A. R. , Börngen F.
Published: July 2016

On the basis of direct UBV and spectral observations at Tautenburg (DDR) 2m and Special Observatory (USSR) 6m telescopes respectively the colorimetric and spectral investigations of the megamaser galaxy MRK 273 are carried out. It is seen that: MRK 273 is in a physical group of galaxies, which contains at least five members. Two bright central condensations of MRK 273 are Seyfert nuclei. The area of the main body of MRK 273 which contains both Seyfert nuclei and from which comes out a straight tail, is redder than the remaining part of the galaxy. The tail has a pronounced blue color and most probably radiates in [OIII] λ5007 line. Observed radio continuum, OH and HI absorption features are related to bright “a” nucleus of galaxy. We come to the conclusion that MRK 273 which is the member of the group of the galaxies is itself a close system of two objects with AGNs. The tail, with radiation being of thermal origin, probably is the result of the interaction of these galaxies.
Radio Loud Far-Infrared Galaxies
Authors: Dey Arjun , van Breugel Wil , Shields Joseph C.
Published: July 2016

We present the first results of a multiwavelength study of IRAS galaxies with excess radio emission. The sample was selected by cross-correlating the IRAS Faint Source Survey (for |b| ≥ 50°) and the Point Source Catalogue (for 10° < |b| < 50°) with the Texas radio survey. Recent optical (imaging and spectroscopic) and radio (VLA) observations are discussed. These observations will be used to investigate possible connections between radio galaxy activity, star formation and galaxy interactions.
Galaxy Interactions and Star Formation: Results of a Survey of Global Ha Emission in Spiral Galaxies in 8 Clusters
Authors: Moss C.
Published: July 2016

Kennicutt & Kent (1983) have shown that the global Ha emission from a spiral galaxy is an indicator of the formation rate of massive stars. Moss, Whittle &: Irwin (1988) have surveyed two clusters (Abell 347 and 1367) for galaxies with Ha emission using a high dispersion objective prism technique. The purpose of the survey is to investigate environmental effects on star formation in spiral galaxies, and in particular to ascertain whether star formation is enhanced in cluster spirals. Approximately 20 % of CGCG galaxies were detected in emission. Two plates of excellent quality were obtained for each of the two clusters, and galaxies were only identified to have emission if this was detected on both plates of a plate pair. In this way, plate flaws and other spurious identifications of emission could be rejected, and weak emission confirmed.
Central Activity in 60 Micron Peakers
Authors: Heisler Charlene A. , Vader J.P. , Frogel Jay A.
Published: July 2016

We present CCD imaging results of our sample of IRAS galaxies with spectral energy distributions peaking at 60μm (Vader et al 1988). The results support our suggestion that the activity in 60μm peaking galaxies is centrally concentrated, and represents an early stage of dust-embedded nuclear activity. This activity is probably triggered by a recent interaction/merger event as indicated by their peculiar optical morphologies. We propose that 60μm peakers are the precursors of S0’s in the case of amorphous systems, and ellipticals in the case of interacting galaxies.
The Nature of the Emission-line Nebulae in Powerful Far-infrared Galaxies
Authors: Armus Lee , Heckman Timothy M. , Miley George K.
Published: July 2016

We discuss our program of narrow-band (Hα + [Nil]) imaging of a sample of 30 powerful far-infrared galaxies (FIRG’s) chosen to have far-infrared spectral energy distributions similar to the prototype FIRG’s Arp 220, NGC 3690, NGC 6240, and M82. The emission-line nebulae of these IR color-selected sample (ICSS) galaxies as a class are both impressively large (mean half light radius, r ~1.3 Kpc, and mean diameter, D ~16 Kpc) and luminous (LTOT ~108 Lo; uncorrected for internal extinction). The mean total Hα + [Nil] luminosity of the FIRG’s is comparable to that found for pairs of optically selected interacting galaxies (Bushouse, Lamb, and Werner 1988), but is a factor of ~5 greater than that of isolated spirals (Kennicutt and Kent 1983). Only ~25% of the nearby (z ≤ 0.10) FIRG’s have morphologies suggesting that large HII~regions contribuí significantly to their emission-line appearance. The broad-band morphologies of our IR color-selected galaxies fall into three major categories. Nearly 75% are single galaxy systems, with the remaining FIRG’s being either multiple nuclei systems, or members of interacting pairs. Since we see few (10%) currently interacting FIRG’s, yet many (80%) with highly distorted continuum morphologies, our IR color criteria may be preferentially selecting galaxies that have undergone highly inelastic, rapidly merging interactions.
Signs of Interaction of the NGC 1275 Nucleus with the High-Velocity System According to 0,″7 Seeing Observations
Authors: Dudinov V. N. , Tsvetkova V. S. , Novikov S. B. , Pronik I. I.
Published: July 2016

The nucleus of the Seyfert galaxy NGC 1275 was observed in the B system on 12-1-1989 with seeing 07 using the Zeiss-1000 telescope on Mount Majdanak in Central Asia. Special methods of processing reveal low-contrast details. The nucleus and circumnucleus are stretched in NW-SE direction. There are two narrow filaments near the nucleus in position angles roughly 340° and 320°. The first is directed near the radio jet of the nucleus, the second has broken details curved to the NW or toward the high-velocity system of NGC 1275.
Properties of the Redshift
Authors: Tifft W. G. , Cocke W. J.
Published: July 2016

Central to any analysis of dynamical systems, or large scale motion, is the interpretation of redshifts of galaxies as classical Doppler velocity shifts. This is a testable assumption and for many years evidence has accumulated that is inconsistent with the assumption. Here we review recent evidence suggesting systematic radial dependence and temporal variation of redshifts.
A Statistical Study of Merging Galaxies-Theory and Observations
Authors: Chatterjee Tapan K.
Published: July 2016

A study of the expected frequency of merging galaxies is conducted, using the impulsive approximation. Results indicate that if we consider mergers involving galaxy pairs without halos in a single crossing time or orbital period, the expected frequency of mergers is two orders of magnitude below the observed value for the present epoch. If we consider mergers invovling several orbital periods or crossing times, the expected frequency goes up by an order of magnitude. Preliminary calculation indicate that if we consider galaxy mergers between pairs with massive halos, the merger is very much hastened.
Probing the Tides in Interacting Galaxy Pairs
Authors: Borne Kirk D.
Published: July 2016

Detailed spectroscopic and imaging observations of colliding elliptical galaxies have revealed unmistakable diagnostic signatures of the tidal interactions. It is possible to compare both the distorted luminosity distributions and the disturbed internal rotation profiles with numerical simulations in order to model the strength of the tidal gravitational field acting within a given pair of galaxies. Using the best-fit numerical model, one can then measure directly the mass of a specific interacting binary system. This technique applies to individual pairs and therefore complements the classical methods of measuring the masses of galaxy pairs in well-defined statistical samples. The “personalized” modeling of galaxy pairs also permits the derivation of each binary’s orbit, spatial orientation, and interaction timescale. Similarly, one can probe the tides in less-detailed observations of disturbed galaxies in order to estimate some of the physical parameters for larger samples of interacting galaxy pairs. These parameters are useful inputs to the more universal problems of (1) the galaxy merger rate, (2) the strength and duration of the driving forces behind tidally-stimulated phenomena (e.g., starbursts and maybe QSOs), and (3) the identification of long-lived signatures of interaction/merger events.
Dynamical Friction in Pairs of Elliptical Galaxies
Authors: Prugniel Philippe , Combes Françoise
Published: July 2016

We present numerical experiments on dynamical friction in pairs of elliptical galaxies of unequal mass. We confirm that the self-gravity of the response is not important and show the drastic effect of the deformability of the companion which reduces the decay time by more than a factor 2. Almost the same amount of orbital energy is dissipated within the satellite than within the large galaxy. Finally, we discuss the importance of distant encounters for the dynamical evolution of systems of galaxies.
Dragging Force on Galaxies Due to Streaming Dark Matter
Authors: Hara Tetsuya , Miyoshi Shigeru
Published: July 2016

It has been reported that galaxies in large regions (~102Mpc), including some clusters of galaxies, may be streaming coherently with velocities up to 600km/sec or more with respect to the rest frame determined by the microwave background radiation.) On the other hand, it is suggested that the dominant mass component of the universe is dark matter. Because we can only speculate the motion of dark matter from the galaxy motions, much attention should be paid to the correlation of velocities between the observed galaxies and cold dark matter. So we investigate whether such coherent large-scale streaming velocities are due to dark matter or only to baryonic objects which may be formed by piling up of gases due to some explosive events.
Triplets of Galaxies: their Dynamics, Evolution and the Origin of Chaos in them
Authors: Chernin Arthur D. , Ivanov Alexei V.
Published: July 2016

1. Recently Karachentsev’s group at SAO (6-meter Telescope Observatory) published a list of 84 triple systems of galaxies with their distances, radial (line of sight) velocities, and angular sizes (Karachentseva et al., 1988). This gives a new ground for studies of the dark matter problem which fills the gap between the large cosmic scales (White, 1987; Dekel and Rees, 1987, and Einasto et al., 1977) and the scale of individual galaxies (Erickson et al., 1987). The data on the typical velocity dispersions and linear dimension of the triplets indicate that they contain considerable amounts of dark matter (see also earlier work of Karachentseva et al. (1979). Numerical simulations show that the statistical characteristics of the Karachentsev triplets can be imitated by model ensembles of triple systems with dark matter masses Md = (1 – 3) x 1012 Mo, which is almost ten times greater than the typical mass of stellar galaxies estimated by the standard mass-to-luminosity ratio (Kiseleva and Chernin, 1988).
Virial Coefficient and Hidden Mass in the Galaxy Groups
Authors: Anosova J. P. , Orlov V. V. , Kiseleva L. G.
Published: July 2016

The purpose of this work is a verification of the virial mass estimations for small galaxy groups. The dynamical evolution of triple and quintuple galaxies has been studied by the numerical simulations. The dependence of the virial coefficient k(t) versus time was derived. Initially k(0) = 0. The function k(t) has some strong oscillations from 0.02 to 0.99. Generally, these oscillations are quasiperiodical ones. Such a behavior of k(t) is caused by formation in a system of close isolated temporary double subsystems. A strong correlation between the virial coefficient and the least mutual distance in the system is observed.
Stationary Orbits of Satellites of Disk Galaxies
Authors: Polyachenko Valerij L.
Published: July 2016

The satellite of an S-galaxy will experience opposing dynamical-friction forces from the stars of the disk and the halo. If these forces are in balance, the satellite may travel in a stable, near-circular orbit whose radius, for a wide range of physical parameters, should be limited to a zone 1.2 to 1.4 times the disk radius, much as is observed.
Do elliptical galaxies have thick disks?
Authors: Thomson R C , Wright A E
Published: July 2016

We discuss new evidence which supports the existence of thick disks in elliptical/S0 galaxies. Numerical simulations of weak interactions with thick disk systems produce shell structures very similar in appearance to those observed in many shell galaxies. We think this model presents a more plausible explanation for the formation of shell structures in elliptical/S0 galaxies than does the merger model and, if correct, supports the existence of thick disks in elliptical/S0 galaxies.
Wing Galaxies: A Formation Mechanism of the Clumpy Irregular Galaxy Marrarian 297
Authors: Taniguchi Yoshiaki , Noguchi Masafumi
Published: July 2016

In order to contribute to an understanding of collision-induced staxburst activities, we present a detailed case study on the staxburst galaxy Maxkaxian 297 (= NGC 6052 = Arp 209; hereafter Mrk 297). This galaxy is classified as a clumpy irregular galaxy (hereafter CIGs) according to its morphological properties (cf. Heidmann, 1987). Two major clumps and many small clumps are observed in the entire region of Mrk 297 (Hecquet, Coupinot, and Maucherat 1987). A typical major clump of CIGs has a diameter of a few hundred pc and its dynamical mass is estimated as an order of 108M⊙ (Taniguchi and Tamura 1987).
The Multi-Telescope Telescope Project: An Inexpensive Spectroscopic Facility
Authors: Bagnuolo W.G. , Furenlid I.K. , Gies D.R. , Barry D.J. , Hopper C.H. , McAlister H.A. , Hartkopf W.I.
Published: July 2016

We have constructed a new facility at the Georgia State University Hard Labor Creek Observatory, consisting of a telescope and a fiber-fed spectrograph and detector. The Multi-Telescope Telescope (MTT) is an inexpensive one-meter light-collecting telescope whose ‘primary’ mirror consists of nine 33.3 cm mirrors. Each mirror of the MTT focuses light into a separate optical fiber, thus avoiding light losses of conventional fiber bundles. The optical fibers feed a modified ‘slightly’ off-plane Ebert-Fastie spectrograph. The detector is a CCD with low thermal noise characteristics, cooled to 200 K. The CHARA spectroscopic facility will be used for high precision radial velocity observations of binary orbits, tomographic separation of binary spectra, and observations of nonradial pulsations of Be stars.
Spectroscopic Binaries in the Open Cluster M67
Authors: Latham David W. , Mathieu Robert D. , Milone Alejandra A.E. , Davis Robert J.
Published: July 2016

For almost 400 members of M67 we have accumulated about 5,000 precise radial velocities. Already we have orbital solutions for more than 32 spectroscopic binaries in M67. Many of these orbits were derived by combining the Palomar and CfA observations, thus extending the time coverage to more than 20 years. The distribution of eccentricity versus period shows evidence for tidal circularization on the main sequence. The transition from circular orbits is fairly clean. Excluding the blue stragglers, the first eccentric orbit has a period of 11.0 days, while the last circular orbit has a period of 12.4 days. For longer periods the distribution of eccentricity is the same as for field stars. The blue straggler S1284 has an eccentric orbit despite its short period of 4.2 days.
Spectroscopic Binaries in the Halo
Authors: Latham David W. , Mazeh Tsevi , Stefanik Robert P. , Davis Robert J. , Carney Bruce W. , Torres Guillermo , Laird John B.
Published: July 2016

For almost 1500 stars in the Carney-Latham survey of proper-motion stars we have accumulated about 20,000 precise radial velocities. Already we have orbital solutions for more than 150 spectroscopic binaries in this sample, and about 100 additional binary candidates with variable velocity. We find that among the metal-poor halo field stars in this sample the frequency of short-period spectroscopic binaries is indistinguishable from that of the disk. The distribution of eccentricity versus period shows evidence for tidal circularization on the main sequence. For the binaries more metal poor than [m/H] = −1.6 there is a clean transition from circular to elliptical orbits at a period of about 19 days. For longer periods the distribution of eccentricity is the same as for stars in the disk of the Galaxy.
TODCOR: A Two-Dimensional Correlation of a Composite Spectrum to Derive the Radial Velocities of its Components
Authors: Mazeh Tsevi , Zucker Shay
Published: July 2016

Cross correlation is a frequently used technique to obtain the Doppler shifts of digitized celestial spectra. This method, suggested by Tonry & Davis (1979), cross correlates the observed spectrum against an assumed template, and obtains the stellar radial velocity by the location of the correlation maximum (Wyatt 1985). The technique finds the correct radial velocity even for extremely low S/N spectra.

Spectra composed of two components present a potential difficulty to this technique. The cross correlation of these spectra usually displays a double peak which can not be resolved whenever the relative velocity of the two components is small. To overcome this difficulty, we developed TODCOR — a new TwO-Dimensional CORrelation algorithm which can simultaneously derive the Doppler shifts of the two components.

TODCOR assumes that the observed spectrum is a combination of two known spectra with unknown shifts. Following the one-dimensional technique, the algorithm calculates the correlation of the observed spectrum against a set of combinations of two templates, with all possible shifts. The correlation, thus, is a two-dimensional function, whose two independent variables are the radial velocities of the two components. The location of the maximum of this function corresponds to the actual Doppler shifts of the two components.
Preliminary Orbits from Velocities with the CCD-Echelle Spectrometer at Lick
Authors: Popper Daniel M.
Published: July 2016

The Hamilton CCD-echelle spectrometer at the coudé focus of the 3-m Shane telescope of the Lick observatory has been described by Vogt (1987). Illustrations of some binary star spectra obtained with this instrument are given by Popper & Nelson (1990, B-type binaries with large magnitude differences) and by Popper (1992, G-type eclipsing binaries), where typical cross-correlation functions are also shown.

In this progress report, I give some initial preliminary orbital results. First is the bright early B binary, VV Ori, the orbits of which have been the subject of considerable controversy (Duerbeck 1975, Andersen 1976, Popper 1981). According to Chambliss & Leung (1982) and to the line ratios, the secondary component contributes about 10% of the light of the system in the visual region. Multiple (2 to 4) exposures of VV Ori have been obtained with the Hamilton on 7 nights. Velocities of the primary are determined from 13 lines, primarily of OII and HeI between 440 and 590 nm. The only lines found to be useful for the secondary are HeI 597.5 and 492.1. Analysis of the velocities is complicated by the poorly determined variation of the center-of-mass velocity, with a range of roughly 26 km s−1 and a period of roughly 120 days (e.g., Duerbeck 1975). Preliminary orbits based on this material lead to masses 11.1 and 4.7.M⊙, to be compared to Duerbeck’s values of 7.7 and 3.4. It is primarily the high signal/noise ratio, over 600, that enables this study to be carried out satisfactorily.
Gravitational Instabilities in Circumstellar Disks and the Formation of Binary Companions
Authors: Adams Fred C. , Benz Willy
Published: July 2016

We review recent work on gravitational instabilities in circumstellar disks and discuss implications for the possibility of forming binary companions within these disks. Linear stability analysis indicates that self-gravitating modes with azimuthal wavenumber m = 1 will grow strongly in star/disk systems with the physical properties observed in astrophysical systems. Smooth particle hydrodynamic simulations indicate that these self-gravitating instabilities (with m = 1 and higher) will grow into the nonlinear regime. In many cases, a spiral arm will collapse into a gravitationally bound “knot” of gas; these knots typically contain 1% of the mass of the disk and travel on elliptical orbits about the central star.
The Fragmentation Mechanism
Authors: Boss Alan P.
Published: July 2016

Binary and multiple star systems may form by fragmentation, that is, through break-up of a dense molecular cloud core during the dynamical collapse phase that leads to the formation of protostellar objects. This review concentrates on theoretical models of fragmentation based on numerical hydrodynamical calculations in three spatial dimensions, using both finite-difference and smoothed particle hydrodynamics techniques. A variety of recent results are described, including calculations of the fragmentation of bar-like (prolate) clouds, fragmentation in clouds with initial power-law density and angular velocity distributions, tidally-induced fragmentation, fragmentation in cooling clouds, formation of hierarchical systems, and the dividing line between clouds that fragment and those that appear to form single protostars. A brief comparison of the predicted physical and dynamical properties of the theoretical fragments with the observed properties of main-sequence and pre-main-sequence binary stars lends supports to the hypothesis that fragmentation is the dominant formation mechanism for binary and multiple star systems. The major uncertainties regarding fragmentation are the extent to which precollapse clouds are susceptible to fragmentation, and the degree to which binary fragments undergo orbital decay and possibly mergers through interactions with the enveloping disk.
The Formation of Non-Equal Mass Binary and Multiple Systems
Authors: Bonnell Ian , Bastien Pierre
Published: July 2016

Calculations of the formation of non-equal mass binary and multiple systems are presented. Binary formation results from the elongated shape of the initial cloud, one fragment forming on each side of the equatorial plane. Slight linear density gradients along the cloud’s major axis are sufficient to form non-equal mass fragments. Resultant mass ratios range from 0.1 to 1.0, in agreement with observations.

In the presence of rotation, the fragments form with surrounding disks. The primary forms with a larger disk than does the secondary. Due to it’s orbital motion around the primary, the secondary can directly accrete the matter that has gathered in the primary’s disk. The secondary is thus less likely to have an appreciable disk, accounting for a redder primary. The binary system’s initially high eccentricity decreases with the continued accretion of higher specific angular momentum at apastron and lower specific angular momentum matter at periastron. Non-coplanar multiple systems with unequal mass components are also formed. The systems are composed of an inner binary and a more distant companion. The mass ratio of the companion binary system is usually less than that of the binary.
A Review of Dynamical Studies of Multiple Stars
Authors: Harrington Robert S.
Published: July 2016

This is not going to be an exhaustive review of all of the literature on the subject of multiple star dynamics, although I will call your attention to the very recent review by Valtonen & Mikkola (1991) entitled “The Few-Body Problem in Astrophysics”. After all, from a dynamical point of view a multiple-star system is the physical realization of the n-body problem of celestial mechanics, and an enormous literature exists for that subject. Rather, this will be some personal thoughts on aspects of the few-body problem that are particularly relevant to the multiple-star astronomer.

One should not forget the case of n=2. Although the problem is completely solvable and contains no surprises, it is one of our reasons to exist. Especially if a binary is on a photographic program, which can yield a parallax, a total mass, and a mass-ratio, and if photometry exists, as is usually the case now for parallax stars, a real contribution is possible. Do an orbit, which is the dynamical problem, and you have two more good points for the empirical mass/luminosity relationship, which is not a bad day’s work for the astrophysicist.
Visual Binary Orbit Calculation with the Help of a PC: One Possible approach
Authors: Ćatović Z. , Olević D.
Published: July 2016

In this work we suggest one possible approach to “computerization” of the process of the visual double star orbit determination. Our computer program, based on the original method (Olević 1989), is interactive which means that the calculator of the orbit makes the final decision about the choice of the best orbit.
The Apparent Galactic Disc Scale Height
Authors: Kroupa Pavel
Published: July 2016

For stars fainter than Mv ≈ 6 the density distribution perpendicular to the Galactic midplane can be approximated by an exponential fall-off with a scale height of about 270 pc. We show that even if in fact constant an apparent decrease of the scale height to about 150 pc for stars with Mv ≈ 17 can be expected if all ‘stars’ measured in the photographic surveys are unresolved binaries. In principle measurements of the apparent scale-height allow the study of the mass-ratio distribution and the proportion among ‘stars’ of binary systems.
Binary Stars in Praesepe
Authors: Kroupa Pavel , Tout Christopher A.
Published: July 2016

In open clusters the scatter about the single-star main sequence is usually negligible. However, unresolved binary systems are brighter and redder than single stars, and thus some ‘stars’ appear shifted away from the main sequence. We make very simple models of the Praesepe cluster, and find evidence that low-mass systems prefer independent component masses, whereas systems of higher mass than the sun appear to favour some correlation towards equal-mass components.
Miras Without Masers are Symbiotic Stars
Authors: Lewis B.M.
Published: July 2016

About 40% of potential OH / IR stars, color selected from the IRAS Point Source Catalog, have no 1612 MHz masers. While these objects are rarely carbon rich, they are usually associated with circumstellar shells. The natural explanation for these “OH / IR star color mimics” is that they are systems with a degenerate companion collecting an accretion disk from a red giant wind. This provides them with an extra source of UV for dissociating their molecules. The persistent absence of the usual complement of masers from an O-rich shell is then a pointer to the presence of a degenerate companion. These occur in association with ~45% of old giant stars.
Calibration of the Mass-Luminosity Relation Using Trigonometric Parallaxes. I
Authors: Van Altena William F. , Girard Terrence M. , Lee John T.
Published: July 2016

The calibration of luminosities using trigonometric parallaxes introduces well-known errors that are a function of the ratio of the parallax error to the parallax, when the sample is chosen from stars with measured parallaxes larger than some minimum parallax. In this paper it is shown that similar errors are also introduced into the mass axis of the mass-luminosity relation (MLR) and can result in a biased MLR. The bias is shown to be related to the Lutz-Kelker correction to the absolute magnitude, as extended by Hanson for the case of selection effects in the data sample. The size of the correction in the mass axis is substantial and for the case of a uniform distribution in space, it can amount to a multiplicative factor of 1.17 in the mass for a ten sigma (σ/π = 0.10) parallax and a factor of 1.62 for a five sigma (σ/π = 0.20) parallax.
Is This Designation Really Necessary?
Authors: Griffin R.F.
Published: July 2016

The only reason that comes to mind why ‘visual’ binaries (whether discovered visually or not) conventionally receive discoverers’ designations, whereas spectroscopic ones do not, is that many visual binaries were discovered before most of the stars concerned had any other designations; spectroscopic binaries were not invented until after the B.D. was published. It is accordingly suggested, very gently, that it no longer serves a useful purpose to attach additional identification numbers to stars that are already well known, and it could even be argued that unnecessary proliferation of designations is best avoided.
The Astrometric Study of ADS 48 — a Nearby Double Star with a Probable Invisible Satellite
Authors: Kiyaeva O.V.
Published: July 2016

The orbit of the visual double star ADS 48 AB is determined on the basis of Pulkovo and Washington sets of observations. The similar deviations in observations of the both sets are discovered. It may be explained by the existence of the invisible satellite with a mass about 0.0lM⊙.
The Gaseous Envelope Structure of the Eclipsing Binary System V448 Cyg
Authors: Manilova (Volkova) G.V.
Published: July 2016

V448 Cyg (HD 190967 = BD+34°3871) represents rather an uncommon case, where the primary component (indicated by stronger lines in the combined spectrum) is the star exhibiting mass loss. The system has a circumstellar envelope, formed by mass flow from a primary component filling its Roche lobe, and by a stellar wind that is stimulated by the duplicity of this system of two hot stars (BO Ib + O9.5 V — see Glazunova et al. 1963). Ultraviolet, polarimetric, and spectral observations of V448 Cyg permitted us to form a model of the structure and parameters of this system’s circumstellar envelope.
Searching for Low–Mass Companions with the HST WF/PC
Authors: Baum William A.
Published: July 2016

Owing to the spherical aberration of the Hubble Space Telescope, prospects are now poor for the astrometric detection of low–mass companions of nearby stars with the Wide–Field / Planetary Camera. The installation of a new camera (WF/PC-II) incorporating an optical correction for the telescope will only partially recover the low–mass companion search capability.
Detection and Measurement of Binary Stars with the HST Fine Guidance Sensors
Authors: Franz O.G. , Kreidl T.J. , Wasserman L.H. , Bradley A. , Nelan E. , Story D. , Whipple A.L.
Published: July 2016

After briefly describing the operation of the Hubble Space Telescope Fine Guidance Sensors (HST–FGS) in the Transfer Function (TF) Scan mode, we discuss the reduction and analysis of scan data affected by HST jitter and Optical Field Angle Distortion (OFAD). We present relative positions and magnitude differences for the components of ADS 11300 = Hu 581 = WDS 18229+1458 derived from TF scans obtained on 17 February 1992. Residuals from a newly revised orbit provide a first indication of the accuracy of HST–FGS observations in the Transfer Function Scan mode.
HIPPARCOS First Results in the Double Star Processing by the FAST Consortium
Authors: Mignard F. , Badiali M. , Bernacca P.L. , Bernstein H. , Cardini D. , Emanuele A. , Falin J.L. , Froeschlé M. , Hering R. , Prezioso G.
Published: July 2016

After the processing of one year of observations carried out by HIPPARCOS it is possible to provide quantitative results as to the number of new double and multiple stars to be detected and the real capacity of this mission to perform relative astrometry on double stars. We present and discuss the methods developed to this end and include the first results concerning the detection statistics and the determination of separation and position angle for double stars. About 16,000 stars have been recognized as non-single, including 9,000 already known as double and mutliple before the mission. Also, a subset of 10,500 stars have been successfully solved for their relative coordinates with an accuracy in the range of 3 to 10 mas.
Search for Wide Double Stars in the Guide Star Catalog I. All Sky Properties of the Catalog
Authors: Bernacca P.L. , Bucciarelli B. , Lattanzi M.G. , Morbidelli R. , Pannunzio R. , Spagna A. , Sarasso M. , Volpicelli A.
Published: July 2016

The immediate object of this effort is the first systematic investigation of the guide star catalog as a new source list for the discovery of possible new visual binary stars. In this first paper of the series we detail on the way used to establish the properties of the catalog, i.e. techniques adopted to measure its completeness as a function of angular separation, magnitude of the primary, and magnitude differences among the components. We have employed the CCDM catalog as the source list of “certified” visual double and multiple stars. The CCDM stars were first matched (rediscovered) in the Guide Star Catalog and then used to build sufficient statistics to establish the relations among the parameters above. These calibrations are essential to properly correct the two– and three–point angular correlation functions, which are our fundamental tools for establishing lists of new probable visual binary and multiple stars.
Absolute Quadrant Determinations from Speckle Observations of Binary Stars
Authors: Bagnuolo W.G. , Mason B.D. , Barry D.J. , Hartkopf W.I. , McAlister H.A.
Published: July 2016

Reduction of speckle data obtained for binary stars is typically carried out using power spectrum or, equivalently, autocorrelation methods. An especially powerful algorithm from which accuate differential astronomy can be obtained is the vector autocorrelation technique. While such methods are highly suited to extracting astrometric information from very large volumes of speckle data in near real–time, they inherently introduce a 180° ambiguity in position angle measurement. We briefly summarize results with a new algorithm which maintains most of the simplicity of vector autocorrelation while removing the quadrant ambiguity.