bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolution Into Contact of the Low-Mass Close Binary Systems
Authors: Sarna M.J. , Fedorova A.V. 
Published: July 2016

AbstractWe investigated the effect of mass accretion on the secondary components in close binomy systems (Mtotal ≤ 2.5M⊙M2.0 ≤ 0.75M⊙) exchanging mass in the case A.
A Gentle Process for the Formation of Algols
Authors: Tout C. A. , Eggleton P. P. 
Published: July 2016

AbstractThis work is concerned with binary systems that we call ‘moderately close’. These are systems in which the primary (by which we mean the initially more massive star) fills its Roche lobe when it is on the giant branch with a deep convective envelope but before helium ignition (late case B). We find that if the mass ratio q(= M1/M2) < qCrit = 0.7 when the primary fills its Roche lobe positive feedback will lead to a rapid hydrodynamic phase of mass transfer which will probably lead to common envelope evolution and thence to either coalescence or possibly to a close binary in a planetary nebula. Although most Algols have probably filled their Roche lobes before evolving off the main-sequence we find that some could not have and are therefore ‘moderately close’. Since rapid overflow is unlikely to lead to an Algol-like system there must be some way of avoiding it. The most likely possibility is that the primary can lose sufficient mass to reduce q below qcrit before overflow begins. Ordinary mass loss rates are insufficient but evidence that enhanced mass loss does take place is provided by RS CVn systems that have inverted mass ratios but have not yet begun mass transfer. We postulate that the cause of enhanced mass loss lies in the heating of the corona by by magnetic fields maintained by an α-ω dynamo which is enhanced by tidal effects associated with corotation. In order to model the the effects of enhanced mass loss we ignore the details and adopt an empirical approach calibrating a simple formula with the RS CVn system Z Her. Using further empirical relations (deduced from detailed stellar models) that describe the evolution of red giants we have investigated the effect on a large number of systems of various initial mass ratios and periods. These are notable in that some systems can now enter a much gentler Algol-like overflow phase and others are prevented from transferring mass altogether. We have also investigated the effects of enhanced angular momentum loss induced by corotation of the wind in the strong magnetic fields and consider this in relation to observed period changes. We find that a typical ‘moderately close’ Algol-like system evolves through an RS CVn like system and then possibly a symbiotic state before becoming an Algol and then goes on through a red giant-white dwarf state which may become symbiotic before ending up as a double white dwarf system in either a close or wide orbit depending on how much mass is lost before the secondary fills its Roche lobe.
Determining Rotation Rates from Light Curves: RW Mon and RW Tau
Authors: Van Hamme W. 
Published: July 2016

AbstractWe present light curve solutions for the non-synchronously rotating Algols RW Mon and RW Tau, and we illustrate how rotation rates are determined from light curves. We find RW Mon’s primary component to spin at about 5 times the synchronous rate, which confirms the indication of fast rotation from reported emission line activity. RW Tau turns out to be only a mildly rapidly rotating Algol system, and our light curve solutions do not yield any firm value for the rotation rate of the primary component. It is suggested that continued efforts should be made to do good quality line broadening studies in order to find rotation rates for systems with only modest degrees of rapid rotation, and in order to further test photometric rotation rates against those of line broadening studies.
The Importance of Wide-System Studies for Stellar Evolution and Galactic Dynamics
Authors: Dommanget J. 
Published: July 2016

AbstractWide pairs and wide multiple systems have been too much neglected during many years by visual double star astronomers with the argument that only close visual pairs (short periods) may lead to mass-determinations in a relatively short time interval. But mass-determination should not be considered as the only interest of double star astronomy, even if it is of a fundamental nature.Today, it appears that researches on the origin and the evolution of the wide systems are urgently wanted, not only for the understanding of the evolution of the stellar medium, but also for a better knowledge of galactic dynamics. Some examples are given.Presently, the main task for double star specialists will be an important improvement in double and multiple star census for all kind of systems: close, medium, and wide. The Hipparcos satellite will probably add some important informations in that respect but ground-based observations also remain of the highest importance (radial velocities, photometry, astrometry, etc.).
Proper Elements, Families, and Belt Boundaries
Authors: Williams J.G. 
Published: July 2016

Families of asteroids were first found by Hirayama (1918, 1923, 1928). More recently Brouwer (1951) and Arnold (1969) have extended greatly the number of families known from the cataloged asteroids. The Palomar-Leiden survey (PLS) (van Houten et al., 1970), which mainly covered very faint, uncataloged objects, found several more families.Except for the work of Hirayama (1918), which used osculating elements, all of the above studies looked for clusterings of the semimajor axis a, the proper eccentricities é, and proper inclinations í. The calculation of proper elements involves using a theory of secular perturbations to remove the long-period, large-amplitude disturbances of the major planets. The theory used Up to now (Brouwer and van Woerkom, 1950; Brouwer and Clemence, 1961) involved a low-order expansion in the eccentricities and inclinations. There is now a theory available (Williams, 1969) that will accurately handle much higher eccentricities and inclinations than before.
Vacuum Ultraviolet Absorption of Dense Plasmas with Resonance Series of Be, B, C, N, Mg, Al and Si
Authors: Mehlman-Balloffet G. , Esteva J. M. 
Published: July 2016

AbstractAbsorption spectra of light elements were observed in the vacuum ultraviolet with an original technique described in an earlier paper (Mehlman-Balloffet and Esteva, 1969). The method utilizes a two-vacuum spark mounting: one of the sparks is emitting the continuous background, the other one generates the absorbing plasma. Several light element have been successsively introduced in the spark anode. For all of them new autoionizing levels have been observed in Rydberg series of resonances exhibiting the asymmetric ‘Beutler-Fano’ profile.In the beryllium and magnesium spectra three new series corresponding to two-electron excitation process have been identified while for boron, carbon, nitrogen, aluminium and silicon the resonances observed correspond to single subshell electron excitation such as: 2s22p2P0 → 2s2p(3P0)np2De for the case of boron.All these series lie in the photoionization continuum of the absorbing atomic species and usually between the first and second ionization limit. This means that they were observed with a normal incidence grating spectrograph in the spectral range 500–1500 Å. In the extreme ultraviolet some other transitions involving inner-shell electron excitation were observed. In the beryllium spectra a series lying between 100 and 110 Å was identified while, the magnesium spectra exhibited only isolated resonances in the 220-265 Å range together with an inner-shell 2p electron photoioniation continuum.A complete description of experimental results with numerical data is being submitted for publication (Esteva and Mehlman-Balloffet, 1972).
Dielectronic Satellite Spectra in the Soft X-Ray Region
Authors: Gabriel A.H. 
Published: July 2016

AbstractSatellite lines, situated on the long wavelength side of the helium-like ion resonance line, can be observed in highly-ionized ions both in laboratory sources and from the Sun. Although seen for more than 30 years, these lines have only recently been classified in detail as inner-shell transitions in lithium-like ions. Laboratory experiments have shown that under steady-state conditions these satellites are produced by dielectronic recombination, although in transient ionizing plasmas direct inner-shell excitation can be important. Detailed calculations have been carried out for high Z ions up to copper, and the results can be compared with solar flare spectra in iron. Such comparisons allow both the electron temperature and the transient state of the plasma to be determined. Laboratory spectra from such high-Z ions are different in appearance, and may be dominated by processes resulting from the transient ionizing state of the plasma.
Laboratory-Produced Radiation Related to the Solar Flare Emission
Authors: Elton R. C. , Lie T. N. 
Published: July 2016

AbstractA review is given of continuing efforts to generate laboratory spectra at photon energies above 1 keV from highly ionized atoms. Emphasis is placed on the most easily-interpreted highest ion stages such as the hydrogenic, helium-like and lithium-like species. The close similarities to solar flare observations of certain signatures, such as the line and continuum X-ray spectra and microwave emission as well as their sequence of occurrence, are pointed out and scaling factors are given.
Spectra of Symbiotic Stars
Authors: Netzer Hagai , Leibowitz Elia M. , Ferland Gary 
Published: July 2016

ABSTRACTWe have observed Z And and other symbiotic stars at the Wise Observatory and have obtained absolute flux measurements of many emission lines. Preliminary analysis of the data shows that the line emitting gas is probably photoionized by a hot, T* ≳ 200,000 OK continuum, which can explain the extremely strong Hell lines. The hydrogen Balmer line intensities are different from what is predicted by recombination theory and the optical depths in Hα and Hβ must be significant. Our photoionization model can be used to deduce the geometry, density and temperature of the line emitting gas, and the nature of the hot companion.
Did Nova Aquilae 1982 Possess a Supercritical Wind?
Authors: Friedjung M. 
Published: July 2016

AbstractThe extremely high velocity absorption components observed in the ultraviolet with IUE, could have been produced by a supercritical wind. In this case most radiation would have been emitted shortwards of Lyman a, even at the time of the first IUE observations.Nova Aquilae 1982 was discovered on January 27, but was difficult to observe at first because of closeness to the sun. A number of IUE spectra were obtained by Blades and Snijders from February 24, and the results were communicated to members of the ESA + SERC nova target of opportunity team. A preliminary report concerning these spectra has been made by Snijders, Seaton and Blades (1982).
Energy Distribution of Hard X-Ray Emitting Cataclysmic Variables
Authors: Mouchet Martine 
Published: July 2016

ABSTRACTWe present the energy distribution of three hard X-ray sources H2252-035, 4U1849-31 and 2A0526-328 identified with intermediate polars. The ultraviolet and optical continuum can be well described by the standard disc model but this requires rather large discs and high accretion rates. Other possible contributions to the energy distribution are estimated. The predicted high accretion rates as well as the amplitude of the optical pulsations are in disagreement with the observed X-ray luminosity suggesting the existence of an unseen soft X-ray or extreme UV component.
Circular Polarimetry of AM Herculis
Authors: Piirola V. , Vilhu O. , Tuominen I. 
Published: July 2016

ABSTRACTCircular polarimetry in the red and simultaneous photometric observations in the UBVRI bands during the period June 1-3, 1981, are discussed. The peak value of negative circular polarization PV ~ -15 % is stronger than observed in 1976-79. Variations in the shape of the polarization and light curves occur from night to night. The positive crossover and reversal of the sign of the circular polarization are only marginal. A probable explanation of the short term variations seems to be the changing shape and position of the accretion columns with respect to the magnetic axis
High Resolution Spectroscopy of Six New Extreme Helium Stars
Authors: Heber U. , Jonas G. , Drilling J.S. 
Published: July 2016

AbstractHigh resolution spectra of six newly discovered extreme helium stars are presented. LSS 5121 is shown to be a spectroscopical twin of the hot extreme helium star HD 160641. A preliminary LTE analysis of LSS 3184 yielded an effective temperature of 22000 K and a surface gravity of log g = 3.2. Four stars form a new subgroup, classified by sharp-lined He I spectra and pronounced 0 II spectra, and it is conjectured that these lie close to the Eddington limit. The whole group of extreme helium stars apparently is inhomogenous with respect to luminosity to mass ratio and chemical composition.
The Period of the Extreme Helium Star BD+1°4381
Authors: Jeffery C.S. , Hill P.W. , Morrison K. 
Published: July 2016

AbstractPhotometry of the variable extreme helium star BD+1°4381 is used to improve the 21.2 day period found by Jeffery & Malaney (1985). The amplitude of the light-curve appears to be variable, resembling that of RY Sgr. Variability in the extreme helium star BD−1°3438 is also reported.
SB 939 - A New Intermediate Helium Star at High Galactic Latitudes
Authors: Langhans G. , Heber U. 
Published: July 2016

AbstractSB 939 was analyzed spectroscopically for the basic atmospheric parameters Teff, log g and helium content. It was shown to be an intermediate helium star (helium abundance = 22% by number) situated unusually far away from star-forming regions.
Temperatures for Hot and Pulsating Helium-Rich (DB) White Dwarfs Obtained with the IUE Observatory
Authors: Liebert J. , Wesemael F. , Hansen C.J. , Fontaine G. , Shipman H.L. , Sion E.M. , Winget D.E. , Green R.F. 
Published: July 2016

AbstractUltraviolet energy distributions are analyzed for several hot, helium atmosphere DB white dwarfs, including the four known pulsating stars which define an empirical DB instability strip. Temperatures are derived exclusively from fits to the ultraviolet energy distributions. The blue edge of the empirical DB instability strip lies at 30,000 ± 4,000 K, and the red edge lies near 24,000 ± 2,000 K. The hottest DB star — and the only known one hotter than the instability strip — is PG0112+104 at or above 30,000 K. This leaves no known helium-atmosphere degenerate stars in the interval 30,000 ≤ Te ≤ 45.000K.
Detection of an Extremely Active State of AM Canum Venaticorum
Authors: Kutty K.R. Narayanan , Marar T.M.K. , Padmini V.N. , Seetha S. , Kasturirangan K. , Rao U.R. , Bhattacharyya J.C. , Mohin S. , Jayakumar K. 
Published: July 2016

Abstract:We report fast photometric observations on AM CANUM VENATICORUM (AM CVn) the ultra short period, hydrogen deficient variable. We have detected on 24th February, 1985 an intense flare of (Δm)peak≈0.34 in white light lasting over 200s. Following this flare we observe an enhanced double humped structure lasting for 1051s which is the dominant periodicity exhibited by AM CVn. We have also detected the 525s and 1051s periods. In addition, we report flickerings, lasting typically 1-2 minutes, that are characteristic of cataclysmic variables.
Pulsations of Hydrogen Deficient Stars
Authors: Saio Hideyuki 
Published: July 2016

AbstractA review is given on the properties of the pulsating hydrogen-deficient stars. Since they lie in a large area of the HR diagram, the properties of pulsations are greatly different among them. Pulsations tend to change from radial pulsations to non-radial pulsations as the surface gravity increases. Strong nonadiabaticity affects the dynamical properties of pulsations in high luminosity helium stars. The kappa and gamma mechanisms for helium ionization excite radial pulsations in relatively cool helium stars and nonradial pulsations in DB (helium atmosphere) white dwarfs, while the cyclical ionization of the K-shell electrons of carbon and oxygen seems to be responsible for the excitation of the nonradial pulsations in the GW Vir (PG1159-035) stars (very hot hydrogen-deficient pre-white dwarf stars). The excitation mechanism of the radial pulsations in a unique extreme helium star V652 Her (BD+13°3224) is not known. Period changes have been detected for many pulsating helium stars except the pulsating DB white dwarfs.
Does 𝓿 Cep indicate a non-axisymmetric dynamo?
Authors: Krause F. , Scholz G. 
Published: July 2016

AbstractAccording to observations of Scholz and Gerth the super-giant 𝓿 Cep has a magnetic field with a maximum field strength up to 2500 Gauss. This field shows a period of about 5 years. It is unplausible that this magnetic field is a relic since 𝓿 Cep was formed by expansion of a B-star. We claim here that 𝓿 Cep represents a dynamo exciting a magnetic field which in the average strongly deviates from symmetry about the rotation axis.
Characteristic Absorption Features in the Spectra of Ap-Si Stars between 1250 and 1850 Å.
Authors: Artru Marie-Christine , Lanz Thierry 
Published: July 2016

AbstractOn the basis of lUE data, the specific absorption features in the spectra of Ap-Si Stars are displayed in the 1250–1850 Å range and identified when possible. The contribution of the Si II multiplets is calculated in LTE for a typical overabundance × 102 of silicon. It accounts for only a small part of the observed absorption. Common unidentified structures, smaller than the 1400 Å depression are pointed out.
Systematics of CP Stars
Authors: Hensberge H. , Van Rensbergen W. 
Published: July 2016

AbstractThis review is concerned with the following topics: 1. The occurrence of chemical peculiar stars in binaries; 2. Determination of masses of CP stars; 3. Determination of radii of CP stars; 4. CP stars in clusters. The paper emphasizes the literature from the 23rd Liege Colloquium in 1981 on, and does not refer systematically to earlier papers.
Abundance Analysis of Three Ap Stars: Hd2453, Hd8441, and Hd192913
Authors: Ryabchikova T.A. , Ptitsyn D.A. 
Published: July 2016

AbstractUsing 9 Å/mm-dispersion spectra of two Ap stars (HD2453 and HD8441) from the list by Adelman (1973) and the SiCr star HD192913 the abundances of 19 elements are obtained by the model atmosphere technique. The curve-of-growth method is used to estimate the surface magnetic field from Fe, Cr, and Ti lines.
Some French Amateurs of the 2nd Half of the 19th Century
Authors: Hourmat Françoise 
Published: July 2016

At that period there was keen popular interest in astronomy, and in many Paris squares, astronomers with terrestrial refractors gave talks on astronomy for a small sum. Léon Joubert created a observatory for scientific research and popularisation, allowing anyone to learn about the universe and use good instruments. He made 120 instruments: refractors, reflectors, projectors, and photographic instruments.Hermann Goldschmidt (1802–1866), born at Frankfurt am Main 17 June 1802, had poor health, became a painter and sought his fortune in Paris. He became an astronomer by accident after following a course of lectures at the Sorbonne given by Le Verrier. From a modest studio on the 6th floor of an old house in the heart of Paris, he discovered 14 minor planets between 1852 and 1861, the first being called Lutetia by Arago.
Observations of Comets, Minor Planets and Meteors in Japan
Authors: Hasegawa Ichiro 
Published: July 2016

In the early period of this century, some comets were discovered by Japanese amateur astronomers. Just fifty years ago, in 1937, Minoru Honda began to search for systematically comets with his 15-cm reflector. He observed Comet Encke without an ephemeris in November, 1937, and made his firts discovery of a comet in 1940. This comet was also discovered independently by Shigeki Okabayashi (Comet Okabayashi-Honda, 1940e). Subsequently, Honda discovered Comet Friend-Reese-Honda (1941a) in 1941. Unfortunately, Okabayashi was killed at the Second World War in 1945.After the end of the war, Honda discovered ten comets during 1947 and 1968. In 1968, he discovered three comets in a year. He has been an active observer of comets and novae. Stimulated by Honda’s success, Tsutomu Seki began his comet hunting in 1950, and his long and patient efforts were rewarded with the discovery of Comet Seki, 1961f. Seki later discovered six comets, and rediscovered six short-period comets before 1981. In that year, Seizo Goto, a well-known telescope maker in Japan, donated a 60-cm reflector. Since then, with the Goto telescope, Seki has made many astronomic observations of comets and minor planets. He has rediscovered some periodic comets and has discovered many minor planets every year.
Image Digitizer
Authors: Magnien Pierre A. 
Published: July 2016

AbstractEquipment for digitizing 24 × 36 mm negatives was described. The sensing unit is a 1024-element CCD. Apart from the optical train, the transparency is held in a rigid carrier that is moved by a stepper motor to scan one row at a time. The whole operation is controlled by computer, and results in a 170.5 kb file for each image.
“Comet” Software
Authors: Butzbach P. , Parisot J.P. 
Published: July 2016

AbstractA suite of programs written in BASIC for use on Apple (II, IIe, etc.) computers was described. A data file, extracted from the general catalogue by Marsden is incorporated. The programs are applicable to any geographical location and allow the determination of positions (in both celestial and horizontal coordinates), times of rising, transit and setting, and the calculation of ephemerides from orbital elements.
Refining the Orbit of Visual Double Stars
Authors: Soulie Edgar 
Published: July 2016

AbstractAn iterative method of refining the orbital parameters of visual double stars was described. The sum of the least-square differences is minimized by the Levenberg-Marquardt method. The application to two examples was described, including one highly inclined orbit, ADS 8862 = Hussey 664 (i = 94.3 degrees).
Photographic Observation of Stellar Occultations
Authors: Tomić A. , Čabrić N. , Čelebonović V. 
Published: July 2016

Stellar occultations are usually observed visually, but this can also be done photographically. Our method has some advantages:
–the obtained moments of contacts refer to the smoothed lunar limb,–the error in the determination of contacts is calculable,–the error may be less than in visual work,–the reduction of photographs is fast, due to the application of an “on-line” computer [1].In order to achieve all this, it is necessary to make a series of photographs of the Moon and the object being occulted before the first and after the last contact. This is a crucial step in our method, because the photographs must be of high quality. This demands two things:
–the images of the occulted object and the Moon must be reliably recorded and–the illuminated limb of the Moon must give optimal darkening on the film.
Analysis of the Light-Curve of Comet P/Halley in 1985–1986
Authors: Valls-Gabaud David , Gómez Angel 
Published: July 2016

We analize the light curve of comet P/Halley resulting from 187 observations made by amateurs. We try to derive some constraints on the physical properties of the comet through the application of the semi-empirical photometric model (SEPM) developped by R.L. Newburn.The m1 (Fig. 2) and V(1,0) light curves show a clear transition phase in the pre-perihelion apparition, between ~ 1.9 and ~ 1.2 A.U. which supports the division into 3 parts made by Hasegawa. It is remarkable to find that the light curve obtained by amateurs is so close to those obtained by experienced observers.We derive an effective equivalent radius of β = 4.9 ± 0.8 (1σ) km, and a geometrical albedo of pυ = 0.06 ± 0.02 (1σ) using the method suggested by Delsemme and Rud.