bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectrophotometric Observations of R CrB During 1972, 74 Minima
Authors: Rao N. Kameswara , Vasundhara R. , Ashoka B.N. 
Published: July 2016

Abstract:The spectrophotometric observations obtained in the wavelength range 3400A to 8000A during 1974, 1972 minima of R CrB have been fitted with Mie scattering calculations assuming sperical graphite particles and various size distributions. Power law type distributions fit the observations fairly well, and indicate that there is decrease in mean particle size as the star comes out of minimum.
Analysis of the Helium Strong Star HD 37017
Authors: Odell Andrew P. 
Published: July 2016

AbstractHigh resolution and signal-to-noise spectra (0.22 A; S/N ≥ 50) of the H-alpha and He I 6678 A lines have been obtained over most of the cycle of the intermediate helium strong star HD 37017 with the Coude spectrograph and CCD camera at KPNO. These spectra are modeled with the non-LTE code of Mihalas to derive properties of the star. Both of the observed lines show small equivalent width variations on the previously known timescale of 0.901 days. The profiles can be simulated by a model with temperature 20,000K, log g=3.4, and helium number fraction 0.25, and which has a helium-rich spot of radius 40° and helium number fraction of 0.60 on the equator. Other possible models are discussed, as well as a model of the weak emission on the wings of H-alpha.
NLTE-Analysis of Three Extremely Helium-Rich O-Type Subdwarfs
Authors: Husfeld C. , Heber U. , Drilling J.S. 
Published: July 2016

AbstractThree extremely helium-rich sdO stars (LSE 153, LSE 259 and LSE 263) were analyzed spectroscopically by means of detailed NLTE model atmospheres. These stars are very hot, with effective temperatures ranging from 70000 to 75000 K and gravities between log g = 4.4 and 4.9. Upper limits for the hydrogen abundance were also derived. The evolutionary status of the sdO stars is discussed and it is concluded that they evolve from the asymptotic giant branch towards the white dwarf stage. A possible evolutionary link between these hot stars and the extreme helium stars of spectral type B is discussed.
The Origin and Structure of the Magnetic Fields of the Chemically Peculiar Stars
Authors: Moss David 
Published: July 2016

AbstractRival theories for the origin of the magnetic fields present in the CP stars are discussed, particular attention being paid to the claims of the ‘contemporary dynamo’ and ‘fossil’ theories. The internal structure of the field as predicted by calculations consistent with the fossil theory is discussed at length. It seems that current time dependent models can now give a coherent picture of the fields of the CP stars according to the fossil theory. Dynamo theory modelling has not been developed in such detail. As yet neither the theoretical predictions nor the observational material seem to be detailed enough to allow a decisive comparison between the theories.
The Magnetic Field and other Parameters of the Chemically Peculiar Stars
Authors: Yu.V. Glagolevskij , I.I. Romanyuk , N.M. Chunakova 
Published: July 2016

The surface field Bs ( but not the effective Be one ) is responsible for different processes occuring in the magnetic stars atmospheres. For this reason it is natural that different investigators are interested in working out and improving methods of determination of Bs. Especially great attention attracts the method based on using the multicolor Geneva photometry. Cramer and Maeder have found a dependence between Bs and parameter Z of multicolor photometry wich they use for the estimation of the surface field. But it is necessary to investigate this method before application. Due to this reason we have put the following two problems:A - The search for stars with a maximal predicted fieldB - Examination of calibration of Bs (Z).
Estimation of Stellar Surface Magnetic Fields by the Curve-of-Growth Method
Authors: Ryabchikova T.A. , Piskunov N.E. 
Published: July 2016

AbstractThe curve-or-growth method of estimating the stellar surface magnetic fields is applied to six Ap stars of different temperatures and one normal (or metallic-line) star σ Aqr. The values of Hs determined by the curve-of-growth technique are in good agreement with those obtained by the photometric method.
Spectroscopy of CP Stars in the Groups of Different Age
Authors: Klochkova V.G. , Kopylov I.M. 
Published: July 2016

AbstractThe observational results for 108 stars, members of 10 galactic groups at the age range of lg t = 6,4 - 8,7 (years), are briefly described. It is shown that the peculiarity index, rotational velocity and magnetic field strength of all the types of CP stars do not vary during their evolution across the main sequence stripe.
The Variability of the λ5200 Feature in CP2 Stars
Authors: Maitzen H.M. , Hensbergb H. 
Published: July 2016

Abstract32 stars have been checked for Δa variability, with the purpose to learn which factor(s) influence the strength of the λ 5200 continuum depression. One third of the stars appear to be constant within a range of 0.005 mag. The results on the remaining ones indicate that maximum strength is related to at least one of the magnetic poles, but spectral inhomogeneities are almost certainly responsible for the largest amplitudes.
A Photometric Investigation of the Magnetic Star 53 Cameloprdalis
Authors: Muciek M. , North P. , Rufener F. , Gertner J. 
Published: July 2016

AbstractGeneva photometry of the important and relatively well known Ap star 53 Cam (HR 3109, HD 65339) is presented. These 27 data, which cover rather evenly the rotational phase interval, are compared with the photometric data in ten bandpasses published by Musielok et al. (1980). They allow to show that at least four “null-wavelength regions” occur between 3400 and 7800 Å.
Computed Spectral Line Variations for Oblique Nonradial Pulsators
Authors: Baade Dietrich , Weiss Werner W. 
Published: July 2016

AbstractSpectral line profiles are computed for nonradially pulsating CP2 stars. For a range which currently is thought to be typical for these stars, the influence of six parameters on the line profiles is considered: mode order ℓ and degree m, pulsation velocity amplitude, the angle between the rotation and pulsation axis, the angle between the rotation axis and the line-of-sight, and the phase angle of the rotation. In view of the expected low signal-to-noise ratio of observational data it is investigated to what extent easily measurable, simple quantities can still be useful in discriminating between different modes.
The Ultraviolet Spectral Energy Distribution of the Magnetic Ap Star Hd 170000 Inside and Outside of the Spots
Authors: Schöneich W. , Hempelmann A. , Želwanowa E.I. 
Published: July 2016

AbstractSixty five TD-1 scans of the magnetic silicon star HD 170000 have been investigated using the method for lightcurves analysis proposed by Hempelmann and Schöneich. The fluxes originating in two spots and in the rest surface of the star have been separated. The conclusion is that the whole stellar surface is strongly peculiar. Spot 1 is a region with the same peculiarity as the rest surface, but strengthened, whereas spot 2 shows additional peculiarities with respect to spot 1 and the rest surface.
A Search for Heavy Elements in the Ultraviolet Spectra of Ap Stars
Authors: Severny A.B. , Lyubimkov L.S. 
Published: July 2016

AbstractThe earlier attempts to detect the lines of heavy elements (Pb, U, Th and others) in the spectra of Ap-stars from the ground-based observations are briefly discussed. UV observations of Ap-stars with the ultraviolet telescope aboard ASTRON space station are described. The reduction of these data is considered. Three spectral regions containing the lines PbIIλ2203.53, UIIλ2556.19 and ThIIλ2368.05 were analyzed by the method of synthetic spectra. It has been shown that relatively cool Ap-star 73 Dra (Teff = 8l50 K) has a great overabundance (≥ 103ε⊙) of heavy elements U, Th, Pb and W.
β CrB – a Rosetta Stone?
Authors: Oetken L. 
Published: July 2016

AbstractCombining the information from the speckle interferometric and spectroscopic binary βCrB a mass of 1.82 solar masses and an absolute visual magnitude Mv = 1m.42 is found, indicating that the star may be in that state of evolution, when the stellar core has shrinked after hydrogen exhaustion in it and the energy generation mainly comes from the envelope. The question whether all magnetic Ap stars are in that special evolutionary state is revived.
Some Structural Features of Magnetic Fields of the Chemically Peculiar Stars β CrB and α2CVn
Authors: Romanyuk I.I. 
Published: July 2016

In spectra of chemically peculiar (CT) stars the weak lines originate at very different levels on the both sides of the Balmer jump (λB = 3646 A): τ ≈ 0.01 at λ > 3646 Å and τ ≈ 0.5–1.0, when λ > 3646 Å (Khokhlova, 1978)To estimate the radial gradient of the magnetic field, we have observed two CP-stars β CrB and α2CVn. from 1979 to 1984 on the 6-meter telescope with an achromatic circular polarization analyzer (Glagolevskij et al.,1978). Compared with classical Zeeman analyzers, whose working wavelength band is only 300 Å, the achromatic analyzer covers a wide spectral region, enabling many more lines to be measured.A combination of camera and grating was chosen so as record the 3300 - 4000 Å region all on the same plate at the 6.7 A/mm dispersion. Since the lines used to measure the field on either side of λ 3646 Å are exposed simultaneously on a single plate, one avoids many of the systematic errors arising from various positional, photometric and polarization effects, all these should influence the short and long wave ends of the spectrogramm identically.
The Abundance of Gallium in B-Type Chemically Peculiar Stars
Authors: Takada-Hidai Masahide , Sadakane Kozo , Jugaku Jun 
Published: July 2016

AbstractQuantitative analyses of the Ga abundances in 27 Hg-Mn stars, 11 Si (magnetic) stars, 8 He-weak stars, and 7 normal stars are made with the resonance lines of Ga II at 1414 Å and Ga III at 1495 Å in IUE spectra. The Ga overabundances are confirmed as a genuine anomaly in many peculiar stars. Only upper limits of the Ga abundance can be obtained for some stars. However these upper limits are much lower than those inferred from visual spectra. Among the 27 Hg-Mn stars, 17 stars are distributed in the range of 2.0 – 3.8 dex of overabundances of Ga. Ten other stars show upper limits less than 2.1 dex. Fifteen stars of 20 hotter Hg-Mn stars with Teff > 11000 K show high overabundances in a narrow range of 2.6 – 3.8 dex, while, among 7 cooler Hg-Mn stars, the only star HR 7775 shows the same overabundance as in these 15 stars. Of 11 Si stars, 9 stars have Ga overabundances ranging from 1.9 to 3.2 dex. Gallium is overabundant in 5 out of 8 He-weak stars in the range of 1.7 – 3.2 dex, while in the three other stars the upper limits are less than 1.3 dex. The Ga abundances in normal stars are all upper limits which roughly correspond to the solar value.
The Metallic-Lined Star 32 Aquarii
Authors: Kocer Dursun , Bolcal Cetin , Adelman Saul J. 
Published: July 2016

AbstractPrelimary results from an optical region study of the metallic-lined star 32 Aquarii indicate Teff = 7600 K, log g = 3.10, ξ = 4.6 km s−1, and an iron abundance about one-half solar.
The Instruments of H.E. Dall
Authors: Hysom E.J. 
Published: July 2016

In 1926 Horace Dall commenced optical work, with interests covering both microscopes and telescopes. Soon (1928), he was making solid eyepieces of the Tolles type. Eventually he developed skills in making lenses of the smallest size to be incorporated into microscope objectives of the highest numerical aperture; this culminated in an objective with a N.A. of 1.92 (a record). The lenses were jewelled elements worked with diamond dust. During World War 2 he repaired all the microscope lenses damaged in the U.K. that had originated with the German firm of Leitz.Horace Dall had an exceptionally inventive mind – and was so active in developing his ideas that he had insufficient time to formally write them up, hence much of his work remains unpublished. He did, however, keep extensive notebooks of his researches into optics. These, along with many prototypes, are now in the custody of the Science Museum, London. Combining his interests in travel, optics, and astronomy, Dall developed a number of portable, ultra-lightweight telescopes. He discovered that by incorporating what is in effect a long working distance, low-power microscope with a Cassegrain telescope he had an instrument with several advantages. The image was erect, the secondary small, and by use of a suitably placed internal stop, sky-flooding was eliminated without the use of shade tubes. Always looking for improvements in optical performance he hit on the idea of modifying the classical Cassegrain telescope by employing a prolate ellipsoidal primary mirror with a spherical secondary: independently discovered by Kirkham in the U.S.A. the type is now universally known as the Dall-Kirkham.
Contributions of Amateur Astronomers to Variable-Star Observing
Authors: Mattei Janet Akyuz 
Published: July 2016

Astronomy is a unique field of science in which amateur astronomers have made and continue to make significant contributions.One major area of the science of astronomy is the study of variable stars. There are more than 28,000 known and catalogued stars that change in brightness – variable stars – and about 15,000 suspected to be variable. These stars need continuous and systematic observing over decades to determine their behaviour and to record any of their unusual or rare activity. However, there are not enough professional astronomers or telescopes to observe these stars regularly. Therefore, variable star astronomy needs amateur astronomers to be the record keepers for these stars. It was for this reason that as early as 1844 and continuing throughout the second half of the nineteenth and early twentieth centuries, the astronomers F.W. Argelander of Germany, Sir John Herschel and J. Baxendell of England, D.F.J. Arago of France, and E.C. Pickering of the United States all advocated systematic variable star observing for amateur astronomers. The encouraging appeals from these leading professional astronomers resulted in the formation of several organized groups of variable stars observers, first in England – the British Astronomical Association (1890), Variable Star Section; then followed by the American Association of Variable Star Observers (1911); the Association Française des Observateurs d’Etoiles Variables (1921); the Royal Astronomical Society of New Zealand, Variable Star Section (1927); and the Japanese Astronomical Study Association (1945). Today, there are about 25 variable star observer groups around the world.
The Effects of Light Pollution on Amateur Astronomy
Authors: Crawford David 
Published: July 2016

AbstractThe rapid increase in urban lighting, with the resultant increase in sky glow due to this lighting, has already severely affected both professional and amateur astronomy. It is not possible to observe as faint as was possible in the past from sites anywhere near large cities. Even those sites near smaller cities are compromised.There are other adverse effects of outdoor lighting. One in particular affects amateur astronomers (more than professionals, in fact). That is light trespass from a (usually) nearby source shining directly into the amateur’s observatory. It ruins dark adaption and can even affect photographic or photoelectric observations.Astronomers are pushing for communities and individuals to apply “solutions”, which can help greatly. These are: use the correct amount of light for the lighting task, not overkill; use controls on the lighting, such as shielding and correct placement (direct the light downward), and time controls; use low pressure sodium light sources whenever possible (especially in the vicinity of professional observing sites).Without the widespread application of such solutions, amateurs, professionals, and even the general public will likely lose forever their superb view of the universe, as seen from a prime dark sky site. These solutions also maximize the quality of any lighting installation, often at lower cost than bad lighting.
Using an Image-Intensifier in Astronomy
Authors: Midavaine Thierry 
Published: July 2016

AbstractThe use of an RTC XX1390 second-generation intensifier (which consists of a S20R photocathode, a micro-channel plate and a screen) was described. In visual work, very faint objects become visible. Photographically, an 18th-magnitude object has been detected through a layer of cirrus. The effective focal length used was 20 m, giving a resolution of 1 arcsecond, thanks to the short exposure times needed. With a Celestron C8 telescope, the coma of Comet Halley was photographed with 2-second exposures, allowing transitory phenomena to be detected. Used in conjunction with video techniques, high time-resolution images could be obtained, opening up the possiblity of new forms of observation of faint objects.
Reduction of Variable-Star Observations Using Basicode
Authors: Jurriens Theo 
Published: July 2016

The Dutch variable star section of the ‘Nederlandse Vereniging voor Weer-en Sterrenkunde’, founded in 1960, has about 10 to 15 regular observers. Depending on the weather conditions they perform 5 to 10 thousand observations a year. Our observation-recorder Henk Feijth collects the observations on paper and, since 1985, also on computer-cassette. From these contributions Feijth compiles a list on paper for the A.A.V.S.O. The cassette is written in a special format using the BASICODE program, see 2.The reduction of the observations can be described as following:1.Every observer and computer-owner enters each observation as a DATA statement in a BASIC program. So each DATA statement is a record representing one observation, each DATA statement contains 20 characters:1- 6 Starname7-10 int(JD-2440000)11-13 fractional part (3 decimals)14: or <15-17 estimate without decimal point18-20 observer codeSo a month of observations is simply a BASIC program consisting of just DATA statements.2.The Dutch broadcasting organization (NOS) has designed a kind of ‘Universal’ BASIC called BASICODE (version 2). With the aid of BASICODE computer X can read the programs of computer Y. The observer translates his data statements (the observations) into the BASICODE format. This is saved on cassette and sent to our recorder.3.Our recorder enters the monthly observations onto the BBC micro with the aid of the BASICODE translation program. Now the recorder runs a program that changes the star name into the Harvard number. This is done for the observations of every observer. After that the whole bunch of observations is sorted in ascending order of Harvard number and JD.4.The file of observations obtained in 3 is used as a source for our own reports, a graphic representation of the observations, and for simulating A.A.V.S.O. record sheets. This ‘end product’ we send to the A.A.V.S.O.
P/Halley: The Disconnection Event of 1986 April 11
Authors: Bergé P.M. , Mahoux G. , Levasseur-Regourd A.C. 
Published: July 2016

This work was carried out by an expedition organized by the S.A.F. in 1986 April to La Réunion. The aim was to observe and photograph P/Halley, within the framework of IHW, as part of the Island Network in the southern hemisphere. To be more precise, our work consisted of studying large-scale phenomena: the structure, dynamics and possible disconnection events in the plasma tail. We were lucky enough to observe one of the latter on the night of April 11/12, and describe it here.For the Island Network, IHW had a number of Schmidt telescopes (Celestron 8). One was lent to the S.A.F. and this is what we used. This telescope has a focal ratio of 1.5, with a 200-mm (8-inch) objective and 300-mm focal length. We used only Kodak TP2415 film, hypersensitized in forming gas (24h at 60°C).
New Trends in the Discovery of Comets by Amateurs
Authors: Merlin J.C. 
Published: July 2016

AbstractThe ways in which amateurs may increase their chances of discovering comets were described. Amateurs discover a considerable proportion of comets, but their contribution is greater among long-period comets. The relative proportions of short-period comets is revealing: 1 in 2 for professional astronomers, 1 in 8 for amateurs. Professional discoveries are largely a by-product of searches for asteroids: the comets have low inclinations (i< 30°) and are faint (m1> 14). Amateurs are most successful in areas close (<60°) to the Sun. Typical apertures are 150-mm, and most comets are brighter than magnitude 10.Past results show that there is a strong correlation between number of observers and number of discoveries. Several amateurs have discovered comets at great elongations with larger telescopes (≥ 400 mm). The comets tend to be fainter (10 <m1< 12). Several comets have been discovered with simple equipment (200- or 300-mm telephoto lenses) down to magnitude 13.Calculations of the distribution of discoverable comets show that an average of 14 comets (9 <m1< 14) are missed per year.
Observation and Analysis of Comet Tails
Authors: van de Weg R.L.W. 
Published: July 2016

AbstractDetails of H2O and dust production in P/Halley are mainly derived from amateur observations of cometary tails, leading to a gas/dust mass-ratio. The rotational period (2.21 day) is also found from amateur observations. Velocity and acceleration of the plasma and velocity and direction of the solar wind are also derived, together with size and indications of the mass-distribution function for dust particles.These techniques have been applied to other comets, giving interesting results on differences between various comets. There is a lot of information available in cometary photographs. The coordination and archival storage of such information is urgently required.
Long-term Monitoring of Solar Activity by Amateur Astronomers
Authors: Reinsch Klaus 
Published: July 2016

Professional solar astronomy concentrates on the study of the atmosphere and interior of the Sun. Little attention is given to “classical” programmes, mainly statistical investigations of solar activity. Although the main properties of phenomena associated with the solar cycle seem to be understood there are still enough details to be explained, making it worthwhile monitoring different indicators of solar activity, even if no immediate results are to be expected. Such routine observations are ideal work of amateur astronomers.Members of West German local astronomical societies founded the journal Sonne in 1977 to combine their efforts on solar observations. The first issue was presented at a conference on amateur solar observation held in Berlin in April 1977. Sonne is compiled by an editorial staff of 23 amateurs from all over West Germany, and is distributed among nearly 500 readers in 20 countries. With the increasing number of foreign readers, the main articles in Sonne are provided with English abstracts.
GEOS Results for PX Cephei
Authors: Boninsegna Roland 
Published: July 2016

This star’s variation was discovered photographically by Romano in 1957. It was included in the GCVS in 1978 as PXCep, and I started to observe it in 1983.The star is usually at maximum, but on several occasions I was able to observe either a rise or the start of a fall. Finally on 1984 October 21, the first minimum was observed, and then a second one ten days later.The star’s constant behavior, outside the minima, indicated that is was an EA type of eclipsing binary. The amplitude of the eclipses is about 2.6 mag. Secondary minimum therefore has an amplitude of 0.11 mag., which is undetectable visually.