bluuebunny/crossref_metadata_2025 huggingface dataset:
Scattering of the Low Frequency Pulsar Radiation
Authors: Kuzmin Arkady
Published: July 2016

We report the results of the measurements and analysis of the pulse broadening due to interstellar scattering on 43 pulsars at 102 MHz. This is the largest uniform sample of direct measurements of pulsar scattering τsc, which make it feasible to analyze the dependence of this value on other pulsar parameters. The measured dependence of τsc on dispersion measure τsc(DM) = 40(DM /100)2.1 is close to theoretically expected relation τsc(DM) α DM2. A frequency dependence of the scattering pulse broadening is weaker than commonly accepted τsc α v−4.4.
Giant Radio Pulses from Pulsars
Authors: Singal Ashok K.
Published: July 2016

We present some results from our observations of giant pulses from PSR B0950+08 at 103 MHz. These observations, now extending over a year, have shown the highest rate of occurrence of giant pulses seen from any known pulsar. Large fluctuations in the intensity levels of individual giant pulses and in their occurrence rate per unit interval of time are seen during a single day’s observations, as well as from one day to the next. We conclude that these intensity variations are likely to be intrinsic to the pulsar.
Propagation of Electromagnetic Waves in Pulsar Magnetospheres
Authors: Istomin Ya.
Published: July 2016

We have developed a numerical code for the propagation of different electromagnetic modes in a pulsar magnetosphere filled by a relativistic, streaming electron-positron plasma in a strong, curved magnetic field. We determine the trajectories, limiting polarization and damping of the waves leaving the magnetosphere.
Multi-Frequency Studies of Intrinsic Intraday Variability
Authors: Wagner Stefan J.
Published: July 2016

Intraday variability is detected in Blazars throughout the electromagnetic spectrum. Only radio emission is affected by interstellar scintillation. The characteristics of variability observed at different frequencies are often similar and suggest that intrinsic variations also contribute to the changes detected in the radio wavelength regime. This in turn implies very high brightness temperatures.

Unambiguous signatures of scintillation and of intrinsic changes have been identified. The properties of intrinsic variations are reviewed to illustrate their potential contribution to variability in the radio domain. Such intrinsic changes need to be discriminated against when studying scintillation in quasars and BL Lac objects. Observations of scintillating sources and of sources with significant intrinsic IDV suggest interesting modifications to the standard paradigm of AGN.
Gravitational Lensing
Authors: Wambsganss Joachim
Published: July 2016

In the roughly 20 years of its existence as an observational science, gravitational lensing has established itself as a valuable tool in many astrophysical fields. In the introduction of this review we briefly present the basics of lensing. Then it is shown that the two propagation effects, lensing and scintillation, have a number of properties in common. In the main part various lensing phenomena are discussed with emphasis on recent observations.
Strong, Variable Circular Polarization in PKS 1519–273
Authors: MacQuart Jean-Pierre , Kedziora-Chudczer Lucyna , Jauncey David , Rayner David
Published: July 2016

We find strong (> 1%) circular polarization in the intraday-variable radio source PKS 1519–273. The source exhibits ~ 12 hourly variability in all four Stokes parameters at 4.8 and 8.6 GHz, and longer timescale variability at 2.5 and 1.4 GHz. The characteristics and frequency dependence of the variability suggest that it is due to interstellar scintillation. VSOP limits on the distance to the scattering screen constrain the brightness temperature to TB > 5 × 1013 K. The fluctuations in total intensity are well-correlated with those in circular polarization, implying that the variable component of the source is −3.8 ±0.4% circularly polarized at 4.8 GHz. The origin of the circular polarization is unclear.
Magnetic Fields in Quasar 3C147 on Milliarcsecond Scales
Authors: Zhang H.Y. , Nan R.D.
Published: July 2016

VLBA polarimetric observations of the steep-spectrum quasar 3C147 were made at four frequencies in the available 5 GHz band, from which polarization in one bright feature in the inner jet was detected. The rotation measure of this feature (~ 1300 rad m−2) agrees with the known high rotation measure of the source, which makes it possible to remove the Faraday screen pixel-by-pixel and obtain the intrinsic magnetic field structure. The arch shape of B vectors suggests that a relativistic and distorted jet is being seen in projection.
Extreme Scattering Events: An Observational Summary
Authors: Joseph T. , Lazio W. , Fey Alan L. , Gaume R.A.
Published: July 2016

We review observational constraints on the structures responsible for extreme scattering events, focussing on a series of observations of the quasar PKS 1741–038. VLA observations were conducted to search for changes in the rotation measure and HI absorption during the ESE, while VLBI observations sought ESE-induccd changes in the source’s image. No RM changes were found implying B‖ < 12 mG, and no HI opacity changes were found implying N(HI) < 6.4 × 1017 cm−2. No multiple imaging was observed, but the diameter of the source increased by 0.7 mas, contrary to what is predicted by simple refractive lens modeling of ESEs. We summarize what these limits imply about the structure responsible for this ESE.
Interstellar Scintillation and Clouds of the Interstellar Turbulent Plasma
Authors: Shishov V.I.
Published: July 2016

Data on interstellar diffraction and refraction scintillation of pulsars are analyzed. Comparison between theory and the observational data shows that two types of spectra for electron density fluctuations are realized in the interstellar medium: pure power law and piecewise with a break. The distribution of turbulent plasma in the Galaxy has a three component structure. Component A is diffuse and it is distributed outside of the spiral arms of the Galaxy. Component BI is cloudy and associated with Galactic arms. Component BII is extremely nonuniform and associated with HII regions and supernova remnants. The origin of the interstellar plasma turbulence is considered, and possible sources of turbulent energy are discussed. The contribution of supernova bursts in the interstellar gas ionization and generation of turbulence are analyzed among other factors.
Interstellar Scintillation Studies of Pulsars and Distribution of Scattering Plasma in the Local Interstellar Medium
Authors: Bhat N.D. Ramesh , Gupta Yashwant , Pramesh Rao A. , Preethi P.B.
Published: July 2016

Pulsar scintillation measurements from the Ooty Radio Telescope (ORT) are used to investigate the distribution of scattering in the Local Interstellar Medium (LISM; region of ≲ 1 kpc of the Sun), specifically the region in and around the Local Bubble. A 3-component model, where the Solar neighborhood is surrounded by a shell of enhanced plasma turbulence, is proposed for the LISM. Further, the Ooty data, along with those from Parkes and other telescopes are used for investigating the distribution of scattering towards the nearby Loop I Superbubble.
Australian Research Effort for the SKA
Authors: Brouw Wim
Published: July 2016

The next generation radio telescope being planned is the Square Kilometer Array (SKA): an international project which is currently in the research and development phase. Australia is one of the partner countries in the SKA consortium; here I describe some of the SKA research being undertaken in Australia.
Extending the Observable Zenith Angle of FAST Using an Offset Feed
Authors: Guoding Li , Nan R. , Peng B.
Published: July 2016

The five hundred meter aperture spherical radio telescope is will use an active spherical reflector. When the zenith scan angle is changed, the illuminated part of the reflecting surface is made to fit a paraboloid of revolution in real time by active control. The maximum zenith scan angle | ψmax | of FAST is 30° under conditions of the geometry selected in order that the feed does not illuminate the ground. The result of this paper shows that the maximum zenith scan angle | ψmax | can be extended to 69° by offsetting the feed.
Far-Red Spectroscopy of Peculiar Stars and the GAIA Mission
Authors: Munari Ulisse
Published: July 2016

The coming GAIA Cornerstone mission by ESA will provide micro-arcsec astrometry, ∼10 bands photometry and far-red spectroscopy for a huge number of stars in the Galaxy (109). GAIA spectroscopy will cover the range 8480–8740 Å which includes the CaII triplet and the head of the Paschen series. In this paper we address the diagnostic potential of this wavelength range toward detection of peculiar stars.
The Massive Close Binary in the δ Ori A Triple System
Authors: Harvin James A. , Gies Douglas R.
Published: July 2016

We present an analysis of short-wave, high-dispersion ultraviolet spectra of the triple star δ Ori A from the International Ultraviolet Explorer Satellite’s (IUE) Final Archive. These spectra were cross-correlated against AE Aur to find the components’ radial velocities, which were then used to produce the system’s orbital elements. The long-period tertiary star in the δ Ori A system was not seen in the resulting cross-correlation functions (CCFs). The close binary’s eclipses allow the orbit’s inclination to be estimated by modeling of its Hipparcos light curve. The primary star appears to have a mass of 11.2 M⊙ and the secondary seems to have a mass of 5.6 M⊙, both of which are about 1/3 of the expected values for stars of their MK types. Although we expected the massive close binary in the δ Ori A system to be a pre-Roche lobe overflow (RLOF) system, these masses appear to require that it be a post-RLOF system. The full description of this work, including the tomographic separation of the spectra for the close binary’s components, appears in Harvin et al. (2002).
Interferometric Observations of η Carinae - the VLTI Takes Its First Glimpse at the Central Source
Authors: Kervella P. , Schöller M. , van Boekel R. , di Folco E. , Correia S. , Glindemann A. , Paresce F. , Richichi A. , Tarenghi M. , Wittkowski M.
Published: July 2016

We describe the first long-baseline interferometric measurement ever made of the luminous blue variable η Carinae. η Car was observed with the Very Large Telescope Interferometer (VLTI) with the 8.2 m Unit Telescopes as well as with the 40 cm test siderostats on three different baselines. We will detail the measurements and data analysis and discuss briefly the implications of the derived visibility on the morphology of the central source. Furthermore we will discuss the future possibilities of interferometric observations and will show that η Car is one of the prime candidates for imaging with the VLTI.
The Interacting Binary Be Star HR 2142
Authors: Peters Geraldine J. , Gies Douglas R.
Published: July 2016

Current information on the nature of the HR 2142 system is presented. The circumstellar material (CSM) including the mass flow toward and away from the mass-gaining B star has been studied from ∼ 100 IUESWP HIRES images obtained from 1979–95 and ground-based CCD data from KPNO acquired between 1985–2001. The strength and velocity behavior of the infall components to the UV Si ɪɪ lines seen during the primary shell phase (PSP) from Φ ∼ 0.70−0.98 resembles that observed in conventional Algol systems, but the inferred mass infall rate is too small to account for the massive Hα-emitting disk about the B primary. The cause for the mass outflow observed during the secondary shell phase (SSP) remains unknown, but a localized plasma that has been identified from phase-dependent variations in the emission component to Heɪ λ6678 may be part of the SSP phenomenon. Although the secondary remains undetected in the optical/IR spectral regions, UV data currently do not yield strong support for the presence of an O subdwarf as in the Φ Per system. HR 2142 may represent and earlier evolutionary stage of Φ Per and a possibly similar Be binary 59 Cyg.
Fluorescence and Chromospheric Activity of V471 Tau
Authors: Vaccaro T.R. , Wilson R.E.
Published: July 2016

The red dwarf + white dwarf eclipsing binary V471 Tau shows a variable Hα feature that varies from absorption during eclipse to maximum emission during white dwarf transit. In 1998 we obtained simultaneous BVRI photometry and Hα spectroscopy, with thorough phase coverage of the 12.5 hour orbital period. A binary star model was used with our light curve, radial velocity, and Hα data to refine stellar and orbital parameters. Combined absorption-emission profiles were generated by the model and fit to the observations, yielding a red star radius of 0.94R⊙. Orbital inclination 78° is required with this size and other known parameters. The model includes three spots 1,000 K cooler than the surrounding photosphere. The variable Hα profile was modeled as a chromospheric fluorescing region (essentially on the surface of the red star) centered at the substellar point. Additional emission seen outside our modeled profiles may be large co-rotating prominences that complicate the picture.
Imaging Ejecta from the Final Flash Star V605 Aql
Authors: Hinkle Kenneth , Joyce Richard , Ridgway Steven , Close Laird , Lebzelter Thomas , Hron Josef , Andre Karin
Published: July 2016

The cloud of ejecta resulting from a final helium shell flash in V605 Aql has been imaged in both optical emission lines and infrared continuum. The obscuring circumstellar dust cloud, whose effects were first seen in 1923, is shown to be bipolar, suggesting dust formation takes place in a disk surrounding this star. The ongoing stellar mass loss in V605 Aql is part of the final flash episode, which has been ongoing since 1919. The pre-final flash planetary nebula, A58, is nearly circular. This implies that significant changes in the mass loss process occur between the AGB and final flash stages.
H 1504+65 – The Naked Stellar C/O Core of a Former Red Giant Observed with FUSE and Chandra
Authors: Werner Klaus , Rauch Thomas , Barstow Martin A. , Kruk Jeff W.
Published: July 2016

H 1504+65 is an extremely hot hydrogen-deficient white dwarf with an effective temperature close to 200 000 K. We present new FUV and soft X-ray spectra obtained with FUSE and Chandra, which confirm that H1504+65 has an atmosphere primarily composed of carbon and oxygen. The Chandra spectra show a wealth of absorption lines from highly ionized oxygen, neon and magnesium and suggest relatively high Ne and Mg abundances. This corroborates an earlier suggestion that H1504+65 represents a naked C/O stellar core or even the C/O envelope of an O/Ne/Mg white dwarf.
The Massive Contact Binary RY Scuti: A WR+OB Progenitor and Its Compact Nebula
Authors: Smith Nathan , Gehrz Robert D.
Published: July 2016

RY Scuti is a massive contact binary in a critical Roche-lobe overflow phase, and it may be an immediate progenitor of a WR+OB binary system like V444 Cygni. It may also have something in common with the eruptive binary HD 5980 in the SMC. RY Scuti is a nearby eclipsing binary, but basic parameters like the mass and evolutionary state of its individual components seem difficult to nail down because it is a common-envelope system. It is also surrounded by a compact double-ring nebula with geometry and kinematics that have interesting implications for its mass-loss mechanism. Some recent results of high-resolution imaging and spectroscopy of the nebula are reviewed here.
HD 101065 – Przybylski’s Star: A Most Peculiar Star
Authors: Kurtz D.W.
Published: July 2016

The story of HD 101065, Przybylski’s star, is one of a forty-year controversy over the nature of what is arguably the most peculiar star in the sky, a controversy that is only now being resolved fully. Our current understanding is that HD 101065 is the coolest (Teff ≈ 7400 K) and the most peculiar of the Ap SrCrEu stars. The existence of this most peculiar star, and other Ap stars, has been the source of some very interesting stellar astrophysics with applications far wider than the understanding of just the stars themselves.
The Characteristics of Magnetic CVs in the Period Gap
Authors: Tovmassian Gaghik , Zharikov Sergey , Mennickent Ronald , Greiner Jochen
Published: July 2016

We have observed several magnetic cataclysmic variables located in the range between 2 and 3 hours, known as the period gap. This work was prompted by the recent discovery of RXJ1554.2+2721. It has 2.54 hours orbital period and shows almost pure cyclotron continuum in a low luminosity state, similar to HS1023+3900, HS0922+1333 and RBS206. These are low accretion rate polars (LARPs) known to have mass transfer rates of order of a few 10-13M⊙/year. The aim of the study was to find out, if magnetic systems filling the period gap are in any way different from their counterparts outside that range of periods. The only significant difference we encounter is a much higher number of asynchronous magnetic systems towards longer periods than below the gap.
The Chandra Observation of the IP TX Col
Authors: Schlegel Eric M. , Salinas Anandi
Published: July 2016

We present a preliminary look at the serendipitous observation of the intermediate polar TX Col by Chandra. The ~52 ksec observation is uninterrupted, providing an opportunity to disentangle the light curve and power spectra components. We illustrate the energy-dependence of the power spectrum.
Hard X-ray Observations of Magnetic Cataclysmic Variables
Authors: Singh K. P. , Rana V. R. , Mukerjee K. , Barrett P. , Schlegel E. M.
Published: July 2016

Hard X-ray light curves and spectral parameters from our analysis of X-ray data of five AM Her type systems – V2301 Oph, V1432 Aql, EP Draconis, GG Leonis, & V834 Cen, and one intermediate polar – TV Col, observed using the Rossi X — ray Timing Explorer (RXTE) satellite are presented. A new improved ephemeris has been derived for V2301 Oph using the mid-eclipse timings. Average intensity variations, without any change of shape of the light curve or hardness ratio, are observed on timescales of a few days to a few months in V2301 Oph. V1432 Aql shows erratic variations on a timescale of a day, at least two sharp dips near orbital phases 0.35 and 0.5, and a total eclipse. Hard X-ray eclipses are also reported in EP Dra and GG Leo. V834 Cen shows intensity variations on yearly timescale and is found to be in a low state in 2002. In TV Col, a binary orbital modulation at 5.5h, in addition to the spin period of 1910s, is reported for the first time. Maximum spectral temperatures in Polars have been determined and used to estimate the masses of the white dwarfs.
Far-UV FUSE Spectra of Peculiar Magnetic Cataclysmic Variables
Authors: Mouchet Martine , Bonnet-Bidaud Jean-Marc , Roueff Evelyne , Abada-Simon Meil , Beuermann Klaus , de Martino Domitilla , Desert Jean-Michel , Ferlet Roger , Fried Robert , Gänsicke Boris , Howell Steve , Mukai Koji , Porquet Delphine , Szkody Paula
Published: July 2016

We present far-UV spectra of the three magnetic cataclysmic variables (MCVs) BY Cam, V1309 Ori and AE Aqr obtained with the FUSE satellite. These MCVs have revealed strongly unusual NV and CIV UV resonance lines. The FUSE spectra exhibit broad OVI lines as well as a strong NIII line at 991Å, while the CIII 1175Å line is nearly absent, supporting non-solar CNO abundances of the accreting matter in these sources. The spectrum of BY Cam shows molecular H2 lines which might be of circumstellar nature. The flaring activity of AE Aqr is also observed in the far-UV range. The radial velocities of the broad OVI components in AE Aqr are orbitally modulated and would indicate an emission region close to the magnetosphere.
The CNO problem in Magnetic Cataclysmic Variables
Authors: Bonnet-Bidaud Jean-Marc , Mouchet Martine
Published: July 2016

Some polars like BY Cam are characterized by unusual CNO line ratios compared to other polars and non-solar abundances have been suggested to explain this anomaly. We present here a first attempt to constrain the elemental abundances in these systems by applying a specific ionisation model combined with a geometrical description of the accretion column where these lines are thought to be formed. The line luminosities have been computed using the CLOUDY plasma code for different ionisation spectra and column extension. We show here selected results and compare to the values observed in “peculiar” magnetic CVs. The model applied to BY Cam confirms that ionization models with solar abundances fail to reproduce the observed line intensity ratios. Assuming the model to be valid, the induced best abundances imply an overabundance of N (x25), underabundance of C (:8) and nearly solar O (:2), in line with CNO reprocessing.
Cyclotron Emission Features in the Spectra of Polars with Low Accretion Rates
Authors: Gospodchikov E. D. , Serber A. V.
Published: July 2016

We calculate non-LTE transfer of cyclotron-harmonics radiation in the hot spot of an accreting magnetic white dwarf (WD) in the case where the contribution of the accretion column to the observed radiation is negligible. The observed cyclotron spectra of a polar with a low accretion rate are found. Based on the theory developed, we interpret the cyclotron emission line spectra of the systems and determine physical conditions in the emission regions of HS 1023+3900 and HS 0922+1333.
Accretion Flow along a Dipolar Field: Application to Intermediate Polars
Authors: Canalle João Batista Garcia , Wu Kinwah , Cropper Mark , Ramsay Gavin , Saxton Curtis J.
Published: July 2016

A hydrodynamic formulation for accretion flow channeled by a dipolar magnetic field is constructed using a curvi-linear coordinate system natural to the field structure. We solve the hydrodynamic equations and determine the velocity, density and temperature profiles of the post-shock accretion flow. The results are applied to accretion flows in intermediate polars. We have found that for systems with massive white dwarfs (~ 1 M⊙) the temperature profiles in the flow can differ significantly to those obtained from models in which the accretion column is assumed to be cylindrical.
An Investigation of Radio Emission in Magnetic Cataclysmic Variables
Authors: Mason Paul A. , Gray Candace
Published: July 2016

The origin of radio emission in magnetic CVs is a long standing problem without a satisfactory solution. We review the radio observations of both non-magnetic and magnetic CVs and discuss possible emission mechanisms. We pose the following questions: Is the presence of a magnetic white dwarf a necessary condition for radio emission? Is there a single cause for the radio emission or are there several radio emission mechanisms? We revisit the suggestion that asynchronism or at least the lack of strict magnetic locking might be a necessary condition for radio emission.
Bi-Modality in the short-term photometric Properties of the Intermediate Polar V1062 Tau
Authors: Lipkin Y. , Leibowitz E. M. , Orio M.
Published: July 2016

We conducted coordinated time-resolved observations of the long-period Intermediate Polar V1062 Tauri at the WIYN Observatory in Kitt Peak, Arizona and at Wise Observatory, Israel, and follow-up observations at the second site. We confirm the presence of two previously reported periodicities of the system: a long period (P≈10 h) which was interpreted as the orbital period of the underlying binary system, and a shorter one (P≈ 1 h), which was interpreted as the spin of the white dwarf. Our data also revealed a third photometric periodicity, corresponding to the orbital sideband of the spin period (OSB). The amplitude of the OSB was found to be strongly correlated with the varying brightness of the system at the orbital cycle.

Our observations suggest bi-modality in the photometric characteristics of the star. In one mode, the light of V1062 Tau varies with the spin period of the white dwarf, whereas the OSB is undetected. In the other mode, the OSB is the main modulation at short time-scales, and the spin period is absent from the light curve. Switching between the two modes occurred three times during the 10 weeks that spanned our observations. Also, we detected an outburst of 1.1 mag, which lasted between ~1 and ~5 days. In addition to the outburst, secular variations in the brightness of the star (0.3 mag on time scale of a few of tens of days) suggest that the system was in a brief low state during 2002 January.
The Secondary Stars in Short Period (Magnetic) Cataclysmic Variables
Authors: Howell Steve B.
Published: July 2016

We review the recent knowledge base pertaining to causes for mass accretion variations (high/low states) in highly magnetic cataclysmic variables (i.e. polars). We then examine what theory has to say about the properties of the secondary stars (the mass donors) with respect to those CVs with very short orbital periods. Finally, we use recent observations of EF Eri in an extended low state to provide direct observational evidence which shows that this CV, as well as a few others, likely contain very low mass, sub-stellar secondary stars.
Combination of Earth Rotation Parameters Obtained in 1980 by Various Techniques
Authors: Feissel Martine
Published: July 2016

In 1980, Earth rotation parameters have been measured by classical astrometry, Doppler and laser satellite techniques, Lunar Laser Ranging and radio-interferometry. The precision of the series and their systematic differences are investigated; a combination algorithm is applied to the series available throughout the year.
An Intercomparison of Connected-Element Interferometer and Lunar Laser Earth Rotation Parameters
Authors: McCarthy Dennis D.
Published: July 2016

The determination of Earth orientation parameters using techniques which promise an improvement in the precision of their measurements requires a careful evaluation of the systematic errors present in each series of observations. It is now possible to begin to inter-compare two of these sets of observations of the rotation of the Earth (UT1-UTC) obtained routinely and independently. These are the data obtained from laser ranging to the Moon and those derived from the connected-element interferometer information of the U. S. Naval Observatory. Although these data are available for a relatively short time span, it is possible to begin to inter-compare the observations in an effort to derive possible systematic errors existing in the data. This has been done using data from July 1979 to March 1980 in comparison with Bureau International de l’Heure (BIH) data. Using this information, the hypothesis that there is no correlation between the differences of the interferometer and laser ranging data with respect to the BIH must be rejected. This indicates that both sets of observations show that systematic errors do exist in the BIH data. The nature of the correlation of the two series is examined to establish possible models of the systematic errors. A much longer series of data from both techniques is necessary to improve the estimates, and the results will depend critically on adopted models used in the reductions and the degree of smoothing to which the raw data are subjected.
Dependence of the Lunisolar Perturbations in the Earth Rotation on the Adopted Earth Model
Authors: Capitaine Nicole
Published: July 2016

If no perturbation exists, the motion of the Earth around its center of mass would be a rigid rotation around a fixed axis in space with constant angular velocity.

In fact, many perturbations disturb this ideal motion and produce variations in both the celestial orientation of the rotation axis and the Earth’s angular velocity.

The mechanisms responsible for these perturbations are the changes in the total angular momentum due to external torques and also the changes in the inertia tensor of the Earth (due to deformations or motions of matter) or in the relative angular momentum in the terrestrial frame (due for instance to winds or to turbulent flow inside the core).
Modelling the Effect of Earth Tides in the Lunar Orbital Motion
Authors: Mulholland J. Derral , Calame Odile
Published: July 2016

The effect of tidal friction in the lunar orbit is one of the classic examples of ad hoc modelling of an unknown physical phenomenon. The two basic calculational approaches in current use are developed in some detail, and numerical tests and comparisons are presented. Although attention is normally concentrated on the acceleration in orbital longitude produced as a result of terrestrial dissipation, it is shown that the variation in Earth-Moon distance due to Earth tides is far from negligible. A significant, though minor, fraction of this variation is supplied by the radial component of the acceleration, which would exist even in the absence of tidal friction. In fact, this represents almost all the difference in the predictions of the two models.
The Relativistic Planetary Perturbations and the Orbital Motion of the Moon
Authors: Lestrade Jean-François , Chapront Jean , Chapront-Touzé Michelle
Published: July 2016

In this contribution, a review of the calculation of the lunar orbit in the relativistic framework is drawn up. Then, the particular dependence of the lunar orbit motion upon the relativistic perturbations of the motions of the planets themselves is put forth.
Comparison of ELP-2000 to a JPL Numerical Integration
Authors: Chapront Jean , Chapront-Touzé Michelle
Published: July 2016

This contribution is an outline of the main results obtained by the authors in comparing their solution ELP-2000, to a JPL numerical integration, LE-51. A full paper containing discussions and comments on the results will be proposed to Astronomy ’ Astrophysics.

A solution for the orbital motion of the Moon has been built by the authors. It is named ELP-2000, the epoch of reference being J2000. It is a semi-analytical solution, its structure being quite similar to Brown-Eckert’s one, as it appears in the Improved Lunar Ephemeris, ILE, j=2, (Eckert et al., 1954). The main purpose of this work is to present the results of a comparison of a provisional but complete solution, to an external numerical integration, LE-51, built at JPL (Williams, 1980), and fitted to lunar laser rangings. The JPL numerical integration is regarded as an “observational model”. It is a first attempt to compare as a whole, a new lunar ephemeris, derived from a semi-analytical theory, to observations, via a numerical integration.
Words for Searching - Key Words
Authors: Schmadel L. D.
Published: July 2016

The importance of key words for information retrieval processes in astronomical bibliographies and data bases is stressed. Construction principles of astronomical vocabularies are discussed with special regard to the practice at ‘Astronomy and Astrophysics Abstracts’.
The PHYS Database: A New Cooperation with AAA
Authors: Lück Wolfgang
Published: July 2016

Since 1979 the Fachinformationszentrum Karlsruhe produces the bibliographic database PHYS which covers the worldwide literature in physics. The database is available on STN International. The database contains about 1,2 million citations in all fields of physics ranging from mathematical physics, elementary particles and field theories, nuclear, atomic and molecular physics, optics, acoustics and fluid dynamics, plasma physics, condensed matter physics, materials science, physical chemistry and biophysics up to geophysics, astronomy and astrophysics. The annual update contains more than 120.000 citations. The database is updated bimonthly. All kinds of literature are included from journal articles, conference papers, books and reports up to dissertations. The citations in the database are in English, publications in other languages have translated English title and abstract. Astronomy and astrophysics are covered in PHYS completely as possible. In 1987 there were more than 21.000 citations in these fields. There are many citations which are classified in PHYS into other fields like atomic or plasma physics and optics and which are not numbered to astronomy but may have a specific relevance for astronomers.
The Union list of Astronomy Serials
Authors: Bausch Judith Lola
Published: July 2016

I would first like to present a little history of this project. I started working at Yerkes Observatory in March of 1972 and found out about the informal meeting in June of that year of observatory and astronomy librarians meeting at Harvard-Smithsonian after the Special Libraries Association meeting in Boston. I arranged to go to that one-day meeting to meet some of the people working in the field; especially in order to know who to call for some good advice once in a while.

My notes from the business meeting that day tell me that “a Union List of Observatory Publications/Astronomy Journals was discussed; no decision.” So I first heard about a union list of astronomy journals in 1972, but it may have been discussed many years before that. The Union List was further discussed at meetings in Pittsburgh in 1973, Toronto in 1974, Chicago in 1975, Denver in 1976, etc., etc.,
Library Collections of Machine-Readable Astronomical Catalogs
Authors: Warren Wayne H.
Published: July 2016

Major astronomical facilities generally use a large number of machine-readable catalogs and data sets. These are requested over a long period of time, usually by individual staff members who seldom request data through their library services. An important drawback of this procedure is that the same catalogs are often requested by different persons at the same institute, thus requiring a duplicate effort on the part of the service organization (usually the data centers) and longer than necessary delays for the persons requesting data. It is suggested that libraries at major facilities build collections of important data sets and maintain library catalogs of these collections for use by staff astronomers. This paper discusses simplified and efficient methods of building such collections and details possible ways of storing and retrieving particular catalogs easily when they are required by staff members.
The On-line IUE Uniform Low Dispersion Archive
Authors: Barylak M. , Wamsteker W. , Driessen C. , Munoz J.R. , Talavera A.
Published: July 2016

After a decade of IUE observations, the dearchiving rate for IUE data in the public domain is more than 1000 images per month, which is more than twice the number of images taken monthly at both groundstations (ie. Goddard Space Flight Center and the ESA Villafrance Satellite Tracking Station). Considering this high interest in IUE data, an effort was made to improve the accessibility of the IUE archive taking into account the availibility of current intercomputer networks.
Care and Handling of Bound Library Materials
Authors: Roosa Mark , Smith Merrily
Published: July 2016

The care and handling of library and archival materials has become a much - discussed topic in recent years. Considerable time, effort, and money are being invested by many libraries and archives in protective housing, rebinding, conservation, and preservation microfilming programs. These activities are expensive. Therefore it makes good fiscal sense to delay the need for these costly activities by making an effort to preserve library materials in good condition for as long as possible.
Sky Brightness at the Kitt Peak National Observatory
Authors: Pilachowski C.A. , Africano J.L. , Goodrich B.D. , Binkert W.S.
Published: July 2016

We report on the results of a program to measure the brightness of the night sky at the Kitt Peak National Observatory during the recent minimum in the solar cycle, a time noted for the darkest nighttime skies. We have measured sky brightness using a 0.9-meter telescope with a photoelectric photometer on seven nights in 1986 and the first half of 1987. During this period, the average sky brightness in the V (yellow) band is 21.92 magnitudes per square arc-sec. This corresponds to an increase of only 6.5 percent over the natural sky illumination, as compared to an increase of over 10 percent predicted by R. Garstang from the presence of cities and towns in southern Arizona. The continued dark skies over Kitt Peak, despite the rapid growth of Tucson’s population, can only be attributed to the effectiveness of light pollution control programs in place since 1972.
Light Trespass Countermeasures
Authors: Schreuder D. A.
Published: July 2016

Human life is geared to the rhythm of day and night. The day is committed to work and activity, and the night to rest, to leisure, but also to contemplation on the universe. Stars are the link between the earth-bound human existence and the eternal and infinite cosmos. So, humanity needs the night, requires the darkness – even if darkness is frightening and is considered as the personification of danger and evil.
Past and Present Studies Relating to the Illumination of the Night Sky
Authors: Walker Merle F.
Published: July 2016

During the period from 1965-1977, I was engaged in a program of selecting and acquiring a new dark sky site in California for the Lick Observatory. Even though the effort was, in the end, unsuccessful, this work did lead to several important advances in our understanding of the general problem of optimizing optical-region astronomical observing conditions. These included:

1)

The development of the polar star trail method of seeing measurement (Harlan and Walker 1965; Walker 1971).

2)

Definition of the conditions required to optimize the seeing through the use of the polar star trail method of measurement at a number of potential and established observing sites around the world (Walker 1970, 1971, 1983, 1984; McInnes and Walker 1974).

3)

Demonstration of the widespread effects of atmospheric pollution in reducing photometric quality at potential sites in California (Walker 1970).

4)

The first extensive study of the effects of light pollution on astronomical observations.
Publicizing Light Pollution and Its Cures
Authors: Schaaf Fred , Kurczewski Rick
Published: July 2016

Publicity is the first and most important tool in efforts to achieve control and reduction of light pollution. It should identify the ways in which light pollution is detrimental to vital human concerns, such as esthetic enjoyment of the heavens, scientific research, and the operation of cost efficient lighting, and take into account the relative importance of the various concerns for each prospective audience or readership.
Big Island Cities at Night
Authors: Westpfahl David
Published: July 2016

Photographs taken during a clear, moonless night from the walkway of the dome of the Canada-France-Hawaii Telescope on Mauna Kea show light trespass from street lighting in Hilo and in Waimea and the sky glow from the growing area around Kona. More full cut-off fixtures would help to prevent deterioration of the quality of the Mauna Kea site.
Radio Spectrum Management and RFI in the United States
Authors: Price R. Marcus
Published: July 2016

In the United States, civil common carrier telecommunications are provided by private companies, not by any agency of the government. Regulation of these services and spectrum management oversight is provided by the Federal Communications Commission (FCC), an agency of the government. Government telecommunications are operated by individual agencies, e.g. the Department of Defense, under the overall regulation of the Office of Spectrum Management of the National Telecommunications and Information Administration (NTIA), a government body separate from the FCC. In bands shared by the civil and government sectors, liaison and coordination is effected between the FCC and the NTIA.
How Geostar Radiodetermination Technology Minimizes Interference to Radioastronomy
Authors: Rothblatt Martin A.
Published: July 2016

Geostar Radiodetermination Satellite Service (RDSS) measures the position of vehicles on the earth using geostationary satellites and time-difference ranging techniques. One of the RDSS frequency bands overlaps with a radio astronomy frequency allocation. The Federal Communications Commission (FCC) mandated a unique spacetime frequency sharing rule to minimize interference.
Effects of RFI on Solar Microwave Bursts Observed with Hightime Resolution
Authors: Luo Xianhan
Published: July 2016

Solar microwave burst observations with high time resolution (~ 1 ms) are important but difficult to make. It is shown by the experiments of radiometer at wavelength 21 cm on 1 ms time scale that some ultrafast time structures in microwaves, which includes spike impulses, switch-on and switch-off structures, etc., may not be from solar emission but from RFI (radio-frequency interference) or from radiometer itself. Because of the uncertainty at 21 cm and other several wavelengths, we suggest that joint observations of the solar microwave bursts on 1 ms time scale should be carried out on the peak years of the 22nd solar activity cycle.
As Bad as Things are for Radio Astronomy in the Protected Bands -- They are Worse for SETI!
Authors: Tarter Jill
Published: July 2016

If the funding that has been requested in NASA’s FY89 budget is forthcoming, the Search for Extraterrestrial Intelligence (SETI) will inaugurate its microwave search program on Columbus Day, 1992. This systematic search for evidence of narrowband microwave signals generated by another technology will continue at several sites around the world until at least 1998. The search will be conducted in two modes: a sensitive targeted search of selected solar type stars covering 1 to 3 GHz, and an all sky survey that covers 1 to 10 GHz. This region of the spectrum is the quietest in terms of natural background noise from astrophysical sources and/or the terrestrial atmosphere, which is why it was chosen. Unfortunately, at the same time that terrestrial technology has enabled this systematic search, it also threatens to render the search all but impossible from the surface of the Earth. Terrestrial transmissions generated for an enormous number of different purposes will be the signals most frequently detected by the SETI systems! This paper describes the design decisions and observing plans that the SETI Program is now making in order to have a chance of successfully “listening” throujgh this heavily utilized portion of the spectrum. We do not yet know precisely how heroic our efforts to discriminate against and identify RFI may have to be, but we have been accumulating observational experience and data that demonstrate convincingly that the situation is rapidly growing worse. Because of the real-time nature of the signal processing being planned, SETI systems will provide an excellent opportunity to monitor, and perhaps identify, sources of narrowband interference within the radio astronomy bands at each site where observations are being conducted.
What are LBV’s? — Their characteristics and role in the upper H-R diagram
Authors: Humphreys Roberta M.
Published: July 2016

Only ten years ago a symposium on the special class of stars we now call Luminous Blue Variables (LBV’s) would not have been possible. At that time we were only just beginning to recognize the similarities among the stars we call S Doradus variables, P Cygni stars, and Hubble-Sandage variables, and their importance in the evolution of the most massive stars.

About a decade ago it became clear that the observed H-R diagram has an upper luminosity limit and thatηCar, P Cyg, and S Dor are all near the temperature-dependent boundary for hot stars. With hindsight the luminosity boundary can be seen in an H-R diagram for hot stars published by Hutchings (1976), but the full temperature range is necessary to show that it really exists. When more data became available in 1977—1978, including the evolved and cool supergiants, the upper luminosity limit became obvious; and we proposed that an instability causingrapidandunsteadymass loss (i.e., LBV’s) is the basic reason for this boundary (Humphreys and Davidson 1979). We emphasized the temperature-dependence of the boundary for the most luminous hot stars, the lack of cooler counterparts at similar luminosities, the nearly temperature-independent limit to the luminosities of cool hypergiants, and the critical role that objects likeηCar, P Cyg, and S Dor may play in the evolution of the most massive stars.
The H-R diagrams of the LMC and SMC
Authors: Garmany C. D. , Fitzpatrick E. L.
Published: July 2016

We present new determinations of the H-R diagrams for luminous, hot stars in the LMC and the SMC. Using all available photometric and spectroscopic data, we discuss the conversion of the observed measurements to temperature and luminosity. The resulting H-R diagrams for normal stars confirm the upper luminosity limit, and also show an interesting “ridge” not noted before.
“Normal” LBV eruptions à la S Doradus
Authors: Wolf B.
Published: July 2016

The main characteristics of the LBVs with “normal” S Dor-type outbursts are reviewed. At quiescence they are luminous (MBol≈ −9 to −10) OB supergiants (14 000 K ≲ Teff≲ 30 000 K) occupying an inclined instability strip in the HRD. The most luminous S Dor variables are the hottest ones. During outburst dense envelopes are expelled of equivalent spectral type middle A to early F. S Dor variables occupy at maximum a vertical strip in the HRD at T≈8000 K. The observed amplitudes in the visual range increase from 1 mag (e.g. R71; Teff= 14500 K at quiescence) to 2.5 mag (e.g. R127; Teff= 33000 K at quiescence). The existence of an amplitude-luminosity relation is suggested which can be used to derive extragalactic distances.
The formation of shells in the wind from P Cygni
Authors: Kahn F. D.
Published: July 2016

A mechanism is proposed for the formation of shells around P Cygni. These shells seem to arise at approximately two monthly intervals and each appears to undergo a steady acceleration of some 0.6 cm s-2during the six months that it is present. In the process to be described the formation of the shells takes place in a stellar wind that moves outwards ballistically from the photosphere. Small fluctuations in wind speed are introduced there and eventually lead to the condensation of shells at a radial distance of the order of 1014cm. The density in the shells is large enough to account for their acceleration by the Lyman continuum emitted by the star. It is also proposed here that the observed time scale of two months is set by the dynamics of the flow field in interaction with the random fluctuations imposed on it at the photosphere.
A source for mass-loss instabilities in LBV’s – the case of P Cygni
Authors: Pauldrach A.W.A. , Puls J. , Kudritzki R.P.
Published: July 2016

Since the basic mechanisms that produce photometric variations, shell ejections, and eruptions of LBV’s are still unknown, it is worthwhile to investigate whether instabilities can occur when the improved self-consistent NLTE treatment of radiation-driven winds (see Pauldrachet al. 1986, Pauldrach 1987, Puis 1987, Pauldrach & Herrero 1988) is applied to objects lying in the LBV part of the H-R diagram. The motivation is obvious: LBV’s have lost considerable fractions of their initial masses and hence have L/M ratios close to the Eddington limit. For such objects, radiation-driven wind theory predicts not only a strong dependence of the mass-loss rate on the self-consistently calculated parameters k, α, and δ, which result from the NLTE occupation numbers of the 133 ions contributing to the line force, but also on Γ (= L/LEdd): Ṁ ~ k1/(α – δ)(1 – Γ)(α – 1)/(α – δ). Here we investigate the dependences of Ṁ on M (through Γ) and on the physical environment of the atmosphere (through k,α, δ) separately. The calculations are performed over a large model grid of stellar parameters for P Cyg, a typical LBV (see Fig. 1).