bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic Mail
Authors: Benn Chris 
Published: July 2016

Astronomers have always had a special need for rapid communication over large distances, partly because of their interest in experiments requiring long baselines. Examples: Eratosthenes’ measurement of the circumference of the Earth; determination of longitude at sea; solar-eclipse tests of general relativity; very-long-baseline interferometry. Of these, at least the second has prompted innovations in communications techniques (beginning with the Greenwich time ball).More recently, the pressing need to travel widely for clean air and aether, and the international flavour of the resulting collaborations, has given astronomers particular incentive to explore the latest communications innovation: electronic mail.
A Proposal for Better Cooperation among Libraries of Astronomical Observatories
Authors: Dale Paul-Henri 
Published: July 2016

SummaryThe cooperation between libraries of astronomical Observatories remains clearly insufficient despite the numerous means of communication now available. The library of the Royal Observatory of Belgium therefore recommends the establishment of a “subgroup” of users (Libraries of Astronomical Observatories) within the already existing Dobis-Libis Users Group.
Administration of Libraries at Distant Sites and Remote Telescope Locations
Authors: Bouton Ellen , Gómez Maria Eugenia 
Published: July 2016

Many librarians are responsible for libraries at outstations and/or remote telescope sites. Such sites may range in size from facilities with as many personnel as the central headquarters to remote observing stations where only a few people are present at any one time. Sites may be only a few kilometers away, or they may be half way around the world. In an informal evening discussion, concerned librarians discussed issues and problems created by such far-flung library systems.Budgetary constraints are a primary problem in managing site libraries at most institutions. Staff and visiting scientists want duplicates at the sites of the books and journals they use regularly in their work, but with current prices it is often difficult to provide even the major astronomy journals for site as well as central libraries. Even when researchers are encouraged to do preparatory research before going to observe, some library materials may still be necessary. In the case of larger sites where people work on a permanent basis, larger collections will, of course, be needed. It is especially important at such sites to provide easy access for materials directly involved in preparation of observations, e.g. photographic sky atlases, reference catalogs of astronomical objects, etc. We discussed at length the problems of selection and acquisition of materials for remote libraries, including questions of purchasing and technical processing, binding, inventory, and bibliographic control.
Summary of a Survey of Astronomy Libraries
Authors: Vargha Magda , Mizser Attila 
Published: July 2016

AbstractA questionnaire about astronomy libraries was distributed in June 1988. The returns from 54 libraries are summarised; they show a large range in size, scope and procedures. Many libraries are connected to networks that give access to bibliographic databases, but only a small number use local computers for cataloguing. Some comments on the returns are given.
Site Preservation at Palomar Observatory
Authors: Brucato Robert J. 
Published: July 2016

ABSTRACTPalomar Mountain was selected as the site of the 200-inch Hale Telescope in 1934. Since then, and especially over the past decade, the population growth of southern California has had a growing adverse impact on the observatory’s environment. In 1981, a very active program was initiated to work with the local governmental agencies to prevent further deterioration of the conditions as the area continues to become increasingly urbanized. The character and scope of the program are described in the paper, as well as more general observations relating to the site preservations process.
Software Tools for Engineering Dark Skies
Authors: Smith A. M. , Dilaura D. L. 
Published: July 2016

ABSTRACTAtmospheric scattering of outdoor nighttime electric illumination produces the principal component of background sky luminance that seriously affects ground-based optical astronomy. The sources for this scattering are Tight emitted skyward directly from luminaires, and light reflected off the ground and other illuminated objects. Careful illumination engineering can thus significantly reduce background sky luminance in two ways: 1) by providing outdoor electric lighting equipment that controls the directions in which light is emitted, and; 2) by proper design of outdoor lighting systems which make efficient use of the east amount of light. Recent developments in applied mathematics and computer software have produced computational tools that are being used to design lighting equipment and lighting systems. The software system for luminaire design significantly reduces the cost of this process by eliminating the need for extensive prototyping and provides for inexpensive experimentation with new designs. The system for outdoor lighting calculations permits the design of highly controlled lighting systems that eliminate glare and upward directed light while providing light appropriate for the visual task. These two software systems are described, along with examples of their use in areas that directly affect astronomical observations.
The Measure of Light Pollution and the Populations of Cities
Authors: Upgren Arthur R. 
Published: July 2016

ABSTRACTA program to measure the night sky brightness has been in progress for some years in order to calibrate the extent of the night sky brightness surrounding the Van Vleck Observatory. Both the central intensity and the areal extent of the brightest sky caused by campus and city were repeatedly measured in order to gauge the extent of the problem. For this purpose, portable visual photometers were designed which have remained stable and usable for nearly a decade. They are now useful for the measurement of the effects of increases in urban growth and of the more flexible attitude of the campus administration toward excess campus lighting. The inability to define city populations which realistically model and predict the measured sky brightness is the largest source of uncertainty. The observatory is in the Northeastern Corridor where the observed brightness is the sum of the illumination from a number of overlapping city sources. Present light pollution studies have not correctly defined the model for the population of an urban area. The two paradigmatic definitions now available for use are shown to be flawed for light pollution comparisons. An algorithm, unlike any in present use, must be sought which distinguishes between individual core cities within metropolitan areas.
120 HZ Variations in Sky Brightness Over Vancouver, BC
Authors: Crabtree David , Westpfahl David , Richer Harvey 
Published: July 2016

ABSTRACTWe have detected a component of sky brightness varying with a frequency of 120 Hertz during high speed photometric observations of 40 Eridani with the 30-cm telescope of the University of British Columbia. The observations were made in 1974, but only recently has their significance to the field of urban illumination been realized. The 120 Hertz component was detected by Fourier analysis of data sets of the star and of the sky alone. We confirmed that the 120 Hertz component was due to urban lighting by direct observation of a “standard source,” a lamp on the campus.
SMM Coronagraph Observations of Particulate Contamination
Authors: St. Cyr O.C. , Warner T. 
Published: July 2016

ABSTRACTSome recent images taken by the white light coronagraph telescope aboard the Solar Maximum Mission (SMM) observatory show bright streaks that are apparently caused by particles associated with the spacecraft. In this report we describe these observations, and we analyze the times of their occurrence. We demonstrate that the sightings occur most often near SMM’s orbital dawn, and we speculate that thermal shock is the mechanism that produces the particles. Although these sightings have not seriously affected the coronagraph’s scientific operations, the unexpected passage of bright material through the field of view of sensitive spaceborne telescopes can lead to data loss or, in some cases, serious detector damage. The topic of space debris has become a significant concern for designers of both manned and unmanned orbiting platforms. The returned samples from the SMM spacecraft and the observations reported here provide a baseline of experience for future orbital platforms that plan long duration missions.
The Use of Meteor Radars in the Detection of Infalling Space Debris
Authors: Olsson-Steel D.I. , Elford W.G. 
Published: July 2016

ABSTRACTRadars of various configurations are used to detect the flux of meteors into the atmosphere, and therefore may be of use in characterizing the artificial meteors produced by small (100 microns - 1 cm) pieces of space debris upon re-entry. Both conventional and over-the-horizon radars are discussed here, and the ways in which they may be deployed in order to detect infalling space debris are outlined.
On the evolutionary status and instability mechanism of the Luminous Blue Variables (LBV)
Authors: Maeder André 
Published: July 2016

AbstractVarious evolutionary sequences leading to LBV are examined. The sequence O-Of-LBV-WR-SN is well supported by the models; some LBV with relatively lower luminosity may turn into OH/IR sources. The overall duration of the LBV phase depends mainly on the average mass loss rate; for &lt;Ṁ&gt; = 10−3M⊙y−1, it lasts about 104y.Very massive stars undergo, when they reach logTeff= 3.9, strong departure from hydrostatic equilibrium due to supra-Eddington luminosities at some depth in the outer layers. This results in heavy mass loss, as the growth rate of the instability is very fast. We suggest that the amount of mass ejected in a shell episode is mainly determined by the mass of such a layer that its thermal adjustment timescale is within an order of magnitude of the stellar dynamical timescale. Simulations of B-light curves due to shell ejections by LBV are performed and some sensitive properties are identified.
Age of Luminous Blue Variable candidates from their stellar and nebular environment
Authors: Lortet M.-C. 
Published: July 2016

AbstractThe study of the context of LBV stars, that is close neighbourhood (companions) and spatial relationship to young objects such as cepheids. stellar associations, red supergiants. enriched OB supergiants. Hll regions. WR stars can provide useful clues on their true luminosity, their age thus eventually initial mass and evolutionary status.
Circumstellar ejecta around LBV’s
Authors: Stahl O. 
Published: July 2016

AbstractThe properties of circumstellar shells around LBV’s are reviewed. Some LBV’s are surrounded by very extended nebulosities, similar to classical planetary nebulae, with AG Car as the prototype. The masses of these nebulae are of the order of a solar mass and their kinematic ages are about 104years. The origin of these nebula is still controversial, but they probably have been ejected in some major outburst in the past. It is then remarkable that the historical outburst of P Cyg has left no bright remnant. There is evidence for CNO processed matter in the ejecta. LBV’s with no detectable extended emission also commonly have nebular emission lines. Some of these nebulae are probably related to the resolved nebulae, but some certainly are very much smaller and have much higher densities.
Observational connections between LBV’s and other stars, with emphasis on Wolf-Rayet stars
Authors: Moffat A. F. J. , Drissen L. , Robert C. 
Published: July 2016

Abstract.We suggest that the LBV mechanism is an essential step to “force” massive stars (M(ZAMS) ≥ 40M⊙) to finally enter the Wolf-Rayet (W-R) domain in the Hertzsprung-Russel diagram (HRD). Just as massive supergiants showincreasingvariability as theyapproachthe Humphreys-Davidson (H-D)instability limit (horizontally in the HRD diagram), so the W-R stars showdecreasingvariability as theyrecede fromthe H-D limit (at first horizontally into the WNL domain, then, with their high mass loss rates, plunging irreversably downwards as ever hotter, smaller and fainter, strong-line W-R stars). Among the W-R stars, the luminous WNL subtypes (especially WN8) are the most variable, probably as a consequence of blob ejection in the wind. The underlying mechanism which triggers this ejection is possibly related to wind instabilities and may thus be quite different from the source of variability in luminous supergiants or LBV’s in quiescence, where photospheric effects dominate.
On the periodicity of Hubble-Sandage objects in M 31
Authors: Ivanov G. R. 
Published: July 2016

The spectral and photometric characteristics of the Hubble-Sandage objects (HSO) are similar to those of the η Car and S Dor variables. They are actually referred to as S Dor-type in the General Catalogue of Variable Stars. Their light variations differ from star to star.The aim of the present paper is to discuss a possible periodicity in HSOs in M 31. We used phtometry from Hubble(1929), Sharov(1973, 1981), Rosino and Bianchini(1973), and added some observations taken during 1980-87. The latter were obtained with the 2-m Ritchey-Chretien-Coude and 0.5-m Schmidt telescopes of the Bulgarian National Astronomical Observatory – Rozhen.
NLTE analysis of R84
Authors: Schmutz W. , Leitherer C. , Torres-Dodgen A.V. , Vogel M. , Conti P.S. , Hamann W.-R. , Wessolowski U. 
Published: July 2016

The LMC star R84 (-HDE 269227 -BR 18) belongs to the group of Ofpe/WN stars believed to be closely related to the Luminous Blue Variables. Support for such a relation comes from the spectral resemblance of these stars to AG Car during visual minimum, and from the observed outburst of the Ofpe/WN star R127.The spectral analysis of R84 presented here is based on model calculations with the NLTE comoving-frame code described by Wessolowski et al. (1988) and references therein. The helium model atom was represented by 28 levels and hydrogen by 9 levels. The free model parameters were varied until the observed line profiles and the absolutely calibrated and dereddened continuum flux were reproduced. The comparison of the theoretical continuum flux distribution with the observed one yields a reddening of EB-V=0.1.
High-dispersion spectroscopy of the B[e] supergiant S 111
Authors: Stahl O. , Smolinski J. , Wolf B. , Zickgraf F.-J. 
Published: July 2016

Abstract:We studied the luminous emission-line star S 111 in the LMC with high-dispersion spectroscopy and classified it as a new member of the class of B[e] sup ergi ants.
A Study of the Compact Group of Galaxies Shahbazian 4
Authors: Lynds C. R. , Khachikian E. Ye. , Amirkhanian A. S. 
Published: July 2016

AbstractFor the members of the compact group of galaxies Shahbazian 4 the radial velocities are defined. The velocity dispersion is 440 km s−1. Moreover the appparent and absolute magnitudes of galaxies in the V band as well as the mass-to-luminosity ratio are obtained. The latter is approximately 220 M⊙/L⊙. The “crossing time” for the group Shahbazian 4 is equal to 4.7 × 107 years. It is one of the densest group of galaxies with n ~ 104 galaxies Mpc−3.
Star Formation in Infrared Bright and Infrared Faint Starburst Interacting Galaxies
Authors: Lamb Susan A. , Bushouse Howard A. , Towns John W. 
Published: July 2016

AbstractShort wavelength IUE spectra of Arp 248b and UGC 8315N are combined with optical spectra and interpreted using a combination of spectrum synthesis and spectral diagnostics to place constraints on the massive star populations of the central regions of these galaxies and to deduce information about the star formation histories in the last 108 years. We find that both galaxies have substantial fractions of their optical light coming from massive stars and that Arp 248b may be dominated in the UV by WR stars. The UV spectra are dominated by radiation from evolved massive stars and we place an age on the burst in Arp 248b of a few tens of millions of years.
On a Connection between Supernova Occurrence and Tidal Interaction in Early Type Galaxies
Authors: Kochhar R.K. 
Published: July 2016

There are three types of supernovae: two subtypes SNIa and lb; and SNII. Late type galaxies produce all types of SN, whereas early types (E, SO, and non-Magellanic irregulars 10) have hosted only SNIa. The recently identified SNIb, like SNII, have massive stars as their progenitors.Reviving Oemler & Tinsley’s (1979) suggestion that SNIa also come from short-lived stars, we have asserted that they need not occur in all early-type galaxies. SNIa occur only in those galaxies that have access to gas and can form stars in their main body. (SN in nuclear regions are a different matter altogether). In this model, SNIa are not associated with typical stellar population of E/SOs but with regions of localized star formation. Note that data on SNIa from spirals is already consistent with this model (see Kochhar 1989 for references and details).
The Kinematics and Morphology of NGC 520: One, Two, or Three Galaxies?
Authors: Stanford S.A. , Balcells M. 
Published: July 2016

AbstractThe peculiar galaxy NGC 520 (Arp 157) is often interpreted as an interacting pair of galaxies. The identification of the two bulges and overall morphology of the two galaxies has long been a puzzle which we attempt to solve in this paper. New longslit optical spectroscopy and near-infrared images of NGC 520 are presented. These data suggest that the northwest peak is the bulge of one of two galaxies in the system. The other larger bulge is clearly evident in the K band image in the middle of the dust lane. The stellar radial velocity profile in the central 10” of the larger bulge is consistent with counterrotation seen in the molecular gas component. This kinematic subsystem could be the remains of a merged gas-rich irregular.
A Tentative Explanation of Cosmological Red Shift
Authors: Chang T. , Torr D. G. 
Published: July 2016

AbstractIn this paper we suggest a possible alternative explanation of cosmological red shift. We consider that there exists a background field in the universe, and that light (the photon) has an extremely weak interaction with this background, and as result, experiences an energy loss. By analogy with damped oscillations, we introduce a dumping term with the first derivative with respect to time in the wave equation. The solution yields a linearly reduced freguency of the light with travel distance. The purpose of this exercise is to demonstrate how a simple alternative interpretation of the Hubble relation can be generated.
Collisional Removal of Hi from the Inner Disks of Virgo Cluster Galaxies
Authors: Valluri Monica , Jog Chanda J. 
Published: July 2016

AbstractIn addition to the well established global HI-deficiency seen in Virgo cluster spirals, many of them are found to be HI-deficient in their inner disks. We show that collisions between galaxies in a cluster can lead to the preferential removal of HI from these galaxies. This follows directly from the application of the Spitzer-Baade collisional gas removal mechanism to galaxies consisting of stars and a two-component ISM of HI and H2, with HI having the largest filling factor. This can account for both the observed Hl-deficiency in the inner disks of these galaxies as well as their normal H2 contents. The frequency of galaxy collisions in the Virgo cluster is shown to be large enough to make collisional gas removal a viable mechanism.
A Two-Dimensional Near—Infrared Speckle Imaging Survey of T Tauri Stars in Taurus and Ophiuchus
Authors: Ghez A. , Neugebauer G. , Matthews K. 
Published: July 2016

AbstractWe present the results of a magnitude limited (K≤8.5 mag) multiplicity survey of T Tauri stars in the two nearest star forming regions, Taurus-Auriga and Ophiuchus-Scorpius (D = 150 pc), observable from the northern hemisphere. Each of the 70 stars in the sample was imaged at 2.2 μm using two-dimensional speckle interferometry resulting in a survey sensitive to binary stars with separations ranging from 0.″09 to about 2″.5.The frequency of double stars with separation in this range is 46±8%. A division between the classical T Tauri stars and the weak-lined T Tauri stars shows no distinction. Furthermore, no difference is observed between the binary frequencies in the two star forming regions although the clouds have very different properties.Given the limited angular separation range that this survey is sensitive to, both the spectroscopic and wide binaries will be missed. The rate at which binaries are detected suggests that most, if not all, T Tauri stars have companions.
The Murky Depths of the Main Sequence: Nearby Speckled Dwarfs and Elusive Brown Beasts
Authors: Henry Todd J. , McCarthy Donald W. 
Published: July 2016

AbstractUsing infrared speckle imaging techniques, we have completed a comprehensive survey of all northern (δ ≥ −25°) M dwarfs within 8 parsecs for low mass companions. Of the 74 targets searched, six new companions were found. Included in the final census are four objects orbiting their primaries at sub-arcsecond separations which have masses near 80 Jupiters, making them viable brown dwarf candidates. Three of these — LHS 1047B, GL 623B and G 208-44B — are the faintest red objects for which masses have been determined and represent the limit of our current knowledge about the faint end of the mass-luminosity relation.The complete sample includes 99 members, and under further analysis reveals fundamental facts about the red dwarf population that were unknown until the present study: 1) 30-40 % of M dwarf primaries have companions, 2) more companions are found orbiting 1-10 AU from the primary than in any other decade interval, and 3) there are 50% fewer red dwarfs known in the more distant half of the survey volume, presumably because the parallax and proper motion surveys are incomplete.In addition, we find that the infrared luminosity function (LF) is fiat or rising toward the end of the main sequence, while the visible LF may be flat, and we illustrate that the determination of an accurate LF is critically sensitive to the resolution of binaries. A better description of the stellar population, the mass function, is found to be undoubtedly rising to the stellar/substellar break. Finally, we have developed a much-needed mass-luminosity relation for stars of mass 1.2 to 0.08 M⊙, and using these relations find that the M dwarfs contribute ~0.2 M⊙/pc3 to the galactic mass.
The Short-Period Binary Frequency Among Low-Mass Pre-Main Sequence Stars
Authors: Mathieu Robert D. 
Published: July 2016

The pre-main sequence (PMS) binary frequency is a fundamental datum in the study of binary formation. It reflects on numerous basic issues, such as:• The formation process. Binary stars are the primary branch of the star-formation process, and thus their frequency is an essential challenge to star-formation theories. (Indeed, the infrequency of single-star formation is likely as significant as the binary frequency.)• The epoch of binary formation. Assessing whether the binary population exists in total by the pre-main sequence phase sets an upper limit on the binary formation timescale.• Early period evolution. The frequency distribution as a function of period of PMS binaries, when compared to the distribution at the zero-age main sequence, can shed light on early orbital evolution.• The interaction of binaries with disks. The formation and consequent dynamical evolution of a binary with semi-major axis less than typical disk radii must substantially modify disk structures and accretion flows. Thus the binary frequency might differ between PMS stars with and without associated disks.