bluuebunny/crossref_metadata_2025_split huggingface dataset:
Arguments for a Mission to an Asteroid
Authors: Alfvén H. , Arrhenius G. 
Published: July 2016

With respect to their orbital parameters, the known asteroids fall into different groups:(1) Main belt asteroids orbit between Mars and Jupiter. Most of them have semimajor axes a in the range 2.0 < a > 3.5 AU.(2) Asteroids outside the main belt form a number of different groups,
such as the Trojans, Hildas, etc.(3) Mars-crossing asteroids are bodies with low a values and perihelia inside the Martian orbit; in several cases they are inside Earth’s orbit. They are the closest neighbors in space of the Earth-Moon system. A list of them is given by Marsden, table II. We select from these the ones with eccentricities in the range 0.2 to 0.4; they will be referred to as the Eros group, named after its largest member. The arguments for a mission to an asteroid refer especially to the Eros group as a first target.
Observations of the Profiles of Solar UV Emission Lines and their Analysis in Terms of the Heating and Production of the Corona
Authors: Boland B. C. , Engstrom S. F. T. , Jones B. B. , McWhirter R. W. P. , Thonemann P. C. , Wilson R. 
Published: July 2016

AbstractObservations of the solar spectrum have been made between 1200–2200 Å with high spectral resolution. The results were obtained with an all-reflecting echelle spectrograph carried by a stabilized Skylark rocket launched in April 1970. Measurements of the profiles of a number of emission lines due to SiII, CII, SiIII and CIV formed in the temperature range 104–105 K, indicate ion energies which are considerably in excess of the electron temperatures derived from the ionization balance. Since the ion/electron relaxation time is very short the observed ion energies cannot correspond to an ion temperature and hence a non-thermal mechanical energy component exists in the transition zone.
Recent Spectroscopy of X-Ray Sources and Systems Related to Cataclysmic Variables: I
Authors: Cowley A.P. , Crampton D. , Hutchings J.B. 
Published: July 2016

ABSTRACTWe present results of recent spectroscopic observations of A) some LMC X-ray sources, B) the X-ray burster 1735-44, and C) the peculiar emission-line binary BE UMa. From the short time scale variations and inferred low mass components each shows some similarities to more classical CV's.
On the Variation of the Orbital Period and the 67-Min Oscillations in EX Hydrae
Authors: Sterken C. , Vogt N. , Freeth R.F. , Kennedy H.D. , Marino B.F. , Page A.A. , Walker W.S.G. 
Published: July 2016

We report the first results of an observational campaign consisting of coordinated photoelectric photometry of Ex Hya from four observatories at different geographical longitudes for a total of 146 hours in April 1979.Ex Hya was monitored differentially for a total of 109 hours, partly simultaneously at different telescopes. The largest time-interval of uninterrupted observation is of nearly 18 hours. 68 times of eclipse, and 89 times of maxima in the 67-minute cycle have been obtained. Figure 1 is an 0-C diagram representing all residuals listed by Vogt et al. (1980), and those as obtained during this run.
AM Herculis Binaries: Particle Acceleration, Radio Emission and Synchronization
Authors: Chanmugam G. , Dulk G. A. 
Published: July 2016

ABSTRACTIt has been suggested that the recently discovered radio emission from AM Her arises as a result of gyrosynchrotron radiation from electrons at energies ≈400 keV in the magnetosphere of the white dwarf. However, no mechanism for producing such energetic electrons was discussed. In this paper, we argue that small departures from synchronous rotation can cause the companion star to act as a unipolar inductor. This leads to high voltages being produced across the companion star, which provides the necessary acceleration mechanism. This also implies that if the magnetic white dwarf was formed with a rapid rotation, synchronization would be achieved on a time scale ~104 yr.
Cataclysmic Binaries Containing a Black-Dwarf Secondary
Authors: Ritter H. 
Published: July 2016

ABSTRACTCataclysmic binaries with a black-dwarf secondary can in principle be distinguished from those containing a low-mass main-sequence secondary because of the differences of the corresponding eclipse light curves. However, due to the very low intrinsic luminosity of the systems containing a black dwarf, the probability of detection turns out to be smaller than the corresponding probability for an ordinary cataclysmic binary by about 1.5 to 3 orders of magnitude. Therefore, despite the fact that the predicted space density of these objects is quite high, systems containing a black-dwarf secondary must remain essentially undetectable.
Non-Radial Pulsations in the Extreme Helium Star HD 160641
Authors: Lynas-Gray A.E. , Kilkenny D. , Skillen I. , Jeffery C.S. 
Published: July 2016

AbstractSimultaneous radial velocity and photometric observations are reported for the variable extreme helium star HD 160641. Pulsation in the 1 - 4 mode could explain the observed variations; the corresponding Wesselink radius would be 8 ± 2 R⊙. The consequent luminosity of log (L/L⊙) - 4.8 ± 0.2 would be consistent with Schonberner's evolutionary model for a lM⊙ extreme helium star.
The Radial Velocity Curve of V652 Her (BD+13°3224)
Authors: Hill P.W. , Jeffery C.S. 
Published: July 2016

AbstractNew radial velocity data for the pulsating extreme helium star V652 Her (BD+13°3224) have been obtained with a time resolution of 100 s. High frequency structure in the radial velocity curve is detected, and a comparison with previous data suggests that the detailed shape of the velocity curve is variable. The data imply that the effective surface gravity must increase by a factor of 4 at minimum radius.
Distribution of Light Minima of R Coronae Borealis Type Stars
Authors: Rosenbush A.E. 
Published: July 2016

Deep light minima of R CrB type stars are considered to occur due to the carbon abundance excess in the atmospheres of these stars, and condensation of carbon into graphite dust leads to light decrease (Zhilyaev et al., 1978). The cause and conditions of dust formation are not clear. Therefore, it is necessary to find out regularities in the occuring of light minima and to search for correlations between different parameters of this type stars. This paper deals with the time intervals between the series of consecutive light minima.A long series of observations of the R Coronae Borealis variables brightness allowed to study repeatedly their light curves in order to obtain their periodicity or other parameters in occuring of deep light minima. The work by Sterne (1935) was the first, in which the conclusion was made that R CrB is an irregular variable. Next investigations contained the analyses of light curves and calculations of the number of minima planned in the definite intervals, f.ex., 0-300, 300-600 days etc. (Howarth, 1977; 1978). Other papers (Tempesti et al., 1975) considered the duration of minima and maxima states. In all these investigations the time was counted off from the moment when a star reached a definite light decrease magnitude, f.ex., Δ m = 1m. The conclusions obtained were similar: the considered parameters were in agreement with Poisson statistics.
Photometric and Radial Velocity Variations of R CrB Near Maximum Light
Authors: Raveendran A.V. , Ashoka B.N. , Kameswara Rao N. 
Published: July 2016

Abstract:Fourier analysis of the light curves of RCrB in V band near maximum shows that in addition to several significant short periods there is a modulation of the visual light with a period around 1170 day, similar to that of L band flux, noticed by strecker. This indicates that there is some contribution to the visual light variations of the star from the pulsating circumstellar dust. Radial velocities of R CrB obtained at Kavalur during February-May 1985 show variations with a period around 47 days.
On the Mass and Luminosity of V348 Sgr
Authors: Schönberner D. 
Published: July 2016

In this short note, an attempt has been made to estimate mass and luminosity of the unique object, V348 Sgr, which appears to be a “Rosetta Stone” for our understanding of late stages of stellar evolution, as
i)its photosphere is virtually hydrogen-free and carbon-rich as with an extreme helium star,ii)it fades irregularly as does a R CrB-star andiii)it is surrounded by a nebular shell similar to that surrounding Planetary Nebulae.We know a great deal more about the above-mentioned objects than about V348 Sgr and this knowledge can be used to obtain estimates on mass and luminosity of the latter.
Practical Problems in the Analysis of CP Stars
Authors: Cowley Charles R. , Johansson Sveneric 
Published: July 2016

AbstractSaturation and curve-of-growth effects remain a dominant source of errors in abundance work. We suggest that the use of low noise material will enable future users to work more easily with weak lines and avoid these difficulties. The method of wavelength coincidence statistics is reviewed within the context of line identifications and abundance work. This technique is readily implemented, and should be a standard part of the analytical spectroscopy of stars. Analysis of the ultraviolet spectra of CP stars is severely handicapped by missing atomic data. Synthetic spectra are displayed showing the possible effects of hitherto unknown lines on spectra of IUE resolution.
On the Duplicity of CP3 Stars
Authors: Schneider H. 
Published: July 2016

AbstractOut of 111 CP3 stars 56.7 percent are binaries and further 15.3 percent are probable binaries. The distribution of the periods shows a maximum around 7 days and the deficit of periods < 3 days is remarkable. Systems with periods < 15 days seem to rotate synchronously, while wider binaries do not. Photometric observations confirm these, and, in addition, point to an occurance of slow pulsation.
Frequency Analysis of the Rapidly Oscillating Ap Star HD 60435
Authors: Matthews Jaymie M. , Kurtz Donald W. , Wehlau William H. 
Published: July 2016

AbstractThe cool Ap star HD 60435 was monitored in a programme of rapid B photometry during 18 nights in January/February 1984, from two stations widely spaced in longitude (the University of Toronto 0.6-m telescope at the Carnegie Southern Observatory (CARSO) on Las Campanas, Chile, and the 0.5-m telescope of the South African Astronomical Observatory ( SAAO)). On six of those nights, contiguous light curves from both sites were obtained.Fourier analysis of these data confirms the rapid variability first reported by Kurtz (1984) and reveals several additional transient oscillations. HD 60435 exhibits persistent - but modulated - oscillations at a frequency near 1.4 IRHZ (period = 11.9 minutes), and short-lived oscillations at frequencies near 1.1 and 4.2 mHz (periods of 15.2 and 4.0 minutes, respectively). These latter two periods represent the longest and shortest yet observed in the class of rapidly oscillating Ap stars.We have applied the oblique pulsator model (Kurtz 1982) to the fine-scale splittings detected in the frequency spectra of the 1.4 and 1.1 mHz oscillations. Also, the series of frequencies close to 1.4 mHz which fall into a pattern of roughly equal spacing is compared to such spacings predicted for overtones in pulsating main-sequence A stars (Shibahashi and Saio 1984). Both approaches suggest that HD 60435 is undergoing non-radial pulsations of odd and even degree (probably with ℓ ≲ 3).The oblique pulsator interpretation of the splittings in the frequency spectrum and the amplitude modulation of the 1.4 mHz oscillations also predict: a rotation period of approximately eight days for this star. Mean photometry of HD 60435, collected by the authors, supports a similar value of 7.7 days for the period.Analysis of the oscillations is hampered by ambiguities due to daily aliases present in the data, and by the complicated structure and time-dependence of the frequency spectrum. Further observations of HD 60435 are essential if we are to fully understand its rapid variations.
Investigations of the Magnetic Star 53 Cam Variations Using the Spectra of High Time Resolution
Authors: Polosukhina N.S. , Malanushenko V.P. , Tuominen I. , Karttunen H. , Virtanen H. 
Published: July 2016

AbstractThe results of automatic reduction of spectral observations of 53 Cam with high time resolution are presented. The statistical analysis of deviations of individual spectrograms of a star from the averaged one for one night permits one to allocate variable details of spectra and estimate the amplitudes of their variability.
Non-Magnetic Intermediate-Temperature Stars: A Review
Authors: Dworetsky M.M. 
Published: July 2016

AbstractThe literature concerning spectroscopic studies, abundances, photometry, and systematics of intermediate-temperature (9500 K < Teff < 16000 K) normal, Hg-Mn, and related stars is reviewed. The review is restricted mainly to papers published since the last international meeting on chemically peculiar stars at Liège in June 1981, and is intended to be complete to 31 December 1984.
Amateur Astronomy in France, 1789–1830: Two Examples
Authors: Dumont Simone , Grillet Solange 
Published: July 2016

AbstractHistorical events affected astronomy in France at this period. Large instruments were also rare so amateurs were on equal terms with professionals. Two significant amateurs are described:Honoré Flaugerges (1755–1830), justice of the peace at Viviers (Ardèche), observed from 1782 until his death, in particular discovering two comets and recording sunspots.Anne-Jean P.C. Duc-Lachappelle (1765–1814), studied astronomy in Paris, and set up an observatory in Montauban in 1789, mainly observing planets and Mercury in particular. He had one pupil, Bernier, and set up a local society for arts and sciences in 1796.Both of these astronomers had numerous contacts with professional astronomers throughout Europe.
Studying “Luna Incognita”: The Region Near the South Pole
Authors: Legrand Michel 
Published: July 2016

AbstractA region of approximately 270 000 km2 near the south pole of the Moon has not been mapped by spacecraft and Dr John Westfall of ALPO proposed the “Luna Incognita” programme in 1972 to try to cover this area. A brief summary of the problems of observing this limb region was given, together with the author’s experience using the T60 and 1-m telescopes at Pic du Midi.
Space Exploration of Comets and the Evolution of Amateur-Professional Cooperation
Authors: Levasseur-Regourd A.-C. 
Published: July 2016

In 1985–86 when spaceprobes flew past P/Giacobini-Zinner and P/Halley, many amateurs observed these comets and submitted their results to national or international (IHW) organisations. Their visual, photographic, photometric and spectroscopic observations made a contribution to scientific knowledge. It is pertinent to ask if space programmes under consideration will allow similar cooperation to be continued.The least uncertain project is that of another cometary fly-past by GIOTTO. Following orbital corrections made between 1986 March 19 and April 2, (ΔV =115 ms−1), the European probe should pass 22 300 km from the Earth on 1990 July 2. The gravitational assist from our planet should then put it onto an orbit to pass P/Hartley 2, P/du Toit-Hartley or P/Grigg-Skjellerup (1992 July 10). This last comet appears to be the most desirable target; although the final decision will not be taken until autumn 1989, recommendations have been made (Morley, 1986) for an international astrometric campaign.
Amateur Astronomers and the Recovery of Periodic Comets
Authors: Martinez Patrick 
Published: July 2016

AbstractMost periodic comets are recovered by professional astronomers at faint magnitudes (18–21). Only Tsutomu Seki, using a 60-cm telescope has been an exception to this rule. Amateurs having access to large telescopes (such as the T 60 at Pic du Midi) now stand a chance of success. For example, using the T 60, the author photographed P/Halley at mag. 19–20 on forming-gas hypered Kodak TP2415 in a 1-hour exposure. Experiments by C. Buil suggest that the same telescope can reach magnitudes 21–22 with a CCD array cooled to – 50° C and a 30-minute integration time.
Amateurs’ Contribution to the PHEMU85 Campaign Observing Mutual Phenomena of Jupiter’s Satellites
Authors: Arlot J.E. 
Published: July 2016

Mutual events (occultations or eclipses) of Jupiter’s satellites occur every 6 years. The 1985 series was particularly favourable as it occurred when Jupiter was at opposition. An observing campaign (PHEMU85) was therefore organized by the Bureau des Longitudes, and sponsored by the CNRS under RCP (Coordinated Research Programme) 754.The interest in observing the events lies in the precise positional information that may be obtained. Conventional (photographic) astrometry gives results to within 400 km, but mutual events give an accuracy of at least 100 km. Observation of mutual events is easy in that the Galilean satellites are bright, so large telescopes do not have to be used, and photoelectric observations in particular can be obtained from urban sites or under poor meteorological conditions. The professional workers generally employed photoelectric photometers or vidicon-type detectors, while amateurs used visual, photographic, photometric and video techniques. Two groups of amateurs were particularly involved, GEOS (European) and GEA (Spain), but individual amateurs also contributed.
Methods of Popularizing Astronomy in Various Countries
Authors: Iwaniszewska Cecylia 
Published: July 2016

AbstractSome interesting methods of popularizing astronomy in various countries were reviewed, and may be divided into two types: active and passive methods. Active methods include:
1.Astronomy in the countryside. Astronomical camps for both children and grownups, who normally live in towns, to learn basic astronomical facts. (Italy)2.Astro-puppets. Visitors to an observatory are greeted by puppets (Copernicus, Galileo, etc.) who not only give talks, but also converse with the audience. (Argentina)3.Hand-operated devices. A simple orrery showing the movement of the Earth, and other devices that viewers operate for themselves. (India)4.Graphical calendars. Several popular observatories collaborate to produce a yearly calendar showing planetary rising and setting times, etc. (Czechoslovakia)5.Amateur clubs. High-school and university students became so interested in astronomy that they formed their own group and now produce a magazine and carry out observing, etc. in a country where there is no professional astronomical institution. (Paraguay)6.An interdisciplinary approach. Various meetings and workshops are arranged to bring together astronomy, physics, biology, geology, etc., leading to a better understanding of modern science. (Japan)7.Astronomical competitions. Everything from children’s drawings to special tests and papers, sometimes connected with special events. Also awards for the best work of popularization in a given year. (Worldwide)Passive methods are far more traditional, and include planetarium shows, including special ones for pilgrims (India); special exhibitions; radio and television programmes; public lectures; popular magazines usually edited for special groups of readers. Finally, what about humorous astronomical stories or pictures, is that active or passive?
Spectral Analysis of the Wolf-Rayet Star HD 50896
Authors: Hamann W.-R. , Schmutz W. , Wessolowski U. 
Published: July 2016

The helium spectrum of the WN5 star HD 50896 (EZ Canis Majoris, WR6) is studied. Our aim is to establish a technique which allows the determination of the parameters of a Wolf-Rayet star from a systematic analysis of its spectral lines. Since the method of “iteration with approximate Lambda operators” became available for application to expanding atmospheres (Hamann, 1986, 1987), we are now able to compare observed spectra to realistic model calculations (Hamann and Schmutz, 1987; Wessolowski et al., 1987).We consider the non-LTE spectral formation in a spherically expanding atmosphere. The velocity field v(r) is specified in its supersonic part by the usual analytical law with the parameters v∞ (final velocity) and the exponent ß=1. The temperature structure is derived from the assumption of radiative equilibrium, but only approximately evaluated for the grey LTE case. The atmosphere is assumed to consist of pure helium. The model atom has a total of 28 energy levels, among these 17 levels of He I. The line radiation transfer is treated in the “comoving frame”.
Call H and K Emission in the Secondary Component of U Cephei
Authors: Okazaki Akira , Nakamura Yasuhisa , Katahira Jun-Ichi 
Published: July 2016

U Cephei (V = 6.8–9.0, P = 2.493 d) is an eclipsing binary consisting of a B7V primary and a G8III-IV secondary component. This binary is one of the semidetached Algol systems showing soft X-ray emission which is probably associated with a hot corona surrounding the secondary component (White and Marshall 1983).We made spectroscopic observations of U Cep with the coudé image-tube spectrograph of the 1.9-m telescope at Okayama Astrophysical Observatory on October 14, 1986. We obtained four spectrograms with a dispersion of 16 Å mm-1 covering λ λ3700—4300 Å during the primary eclipse. The first two exposures were made in a total eclipse, while the last two were slightly after the third contact. The CaII H and K emission lines appear clearly in all the spectrograms. Figure 1 represents an intensity tracing of one of these spectrograms.
Photometric and Polarimetric Observations of the RV Tauri Star AR Puppis
Authors: Raveendran A.V. , Rao N. Kameswara 
Published: July 2016

RV Tauri stars are variable yellow supergiants and they display anomalous excesses in infrared radiation indicating the presence of cool and extended dust thermospheres, presumbly formed from the matter ejected by them (Gehrz 1972). AR Pup, recognised as a member of RV Tauri stars, shows strong CH and CN bands in the optical spectrum and is considered to be carbon-rich (Lloyd Evans 1974). During a programme of broad band polarimetric observations of carbon variables, AR Pup was found to exhibit a large and highly time-dependent linear polarisation (Raveendran & Kameswara Rao 1987).During the period from 1987 January 20 to April 6, AR Pup was observed on 33 nights through standard B and V filters with the 34-cm reflector of the Vainu Bappu Observatory, Kavalur. We also obtained UBVRI polarimetry of AR Pup with the PRL - Polarimeter (Deshpande et al. 1985) attached to the 102-cm reflector on six nights during the same period. Present observations clearly indicate that the large time dependent variations in polarisation, both in the amount and wavelength dependence, observed at earlier epochs by us were not isolated events but were segments of a continuous variation which is cyclic and related to the light curve.