bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Spectrum Variable a Centauri (HD 125 823)
Authors: Klinglesmith D. A. , Bernacca P. L. , Frey H. 
Published: July 2016

AbstractHigh dispersion spectra in the blue violet region and OAO II spectral scans in the UV of the star a Centauri are presented. The variation of equivalent widths and radial velocity are presented. The appearance and disappearance of the forbidden lines of helium, the change in the wing structure of λ 4471 of He I, the strengthening of the UV resonance lines at phase 0.5 and the presence of the UV feature of λ 1720 indicate that the star’s atmosphere is experiencing drastic density changes.
A highly flattened Secondary Star in the Young Eclipsing Binary BM Orionis
Authors: Hall Douglas S. 
Published: July 2016

AbstractA model is proposed for BM Ori to explain why DOREMUS saw only the early B star in the spectrum, whereas the light curve seemed to predict an equally bright cooler star which should have been seen alone at supposed totality. The cool star is assumed to be a disk-shaped object, similar in shape to that proposed by HUANG for ε Aur, seen nearly edge-on. By means of various restraints, it is estimated that the disk covers about 55% of the B star at primary eclipse. This leads to the relative luminosities (Lh = 0.74, 0.87 and 0.92 in V, B, and U), the color of the disk (the opposite side of the disk has the color of a G or F giant), the relative geometrical dimensions (rB = 0.09, rD = 0.25, and the height of the disk h≈0.1), and the orbital inclination (i ≈ 90°). The model with these parameters predicts a theoretical light curve which represents the observations as well as did the solution of HALL and GARRISON, which was based on spherical stars.
Metal Line-Blanketing and Opacity in the UV of α2 CVn
Authors: Molnar Michael R. 
Published: July 2016

AbstractUltraviolet photometric observations by OAO-A2 were made of α2 CVn covering the entire 5ḍ5 period of this magnetic Ap variable. The light curves ranging from 1250A to 3330 A indicate the dominant role of rare-earth line-blanketing in redistributing flux. In a broad depression of the continuum covering 2300 A to 2600 A scanner observations identify strong lines of Eu III as major contributors to this feature. At maximum intensity of the rare-earth lines the ultraviolet continuum shortward of 2900 A is greatly diminished while the longer wavelength regions into the visual become brighter. Thus, the light variations in α2 CVn are: due to the variable strong line-blanketing by the abundant rare-earth elements.
Some Problems in the Study of Variable Stars in Globular Clusters
Authors: Kukarkin B. V. 
Published: July 2016

Three quarters of a century separates us from the beginning of systematic observations of variable stars in globular clusters. During the last 45 yr the name of Mrs Prof. Dr H. B. Sawyer Hogg has always been in the astronomical literature. Her activity is closely connected with investigations of variable stars in globular clusters.The complex dependences between the presence of variable stars of different types and the properties of the globular clusters were discovered long ago. For instance, the RR Lyr variables do not occur in clusters of high metallicity. Red variables on the contrary do not occur in clusters of very low metallicity. The presence and peculiarities of variable stars have been used for the classification of globular clusters (van Agt and Oosterhoff, 1959; Castellani et al., 1970).
An Abundance Analysis of Fehrenbach’s Star (HD 116745) in Omega Centauri
Authors: Dickens R.J. , Powell A. L. T. 
Published: July 2016

AbstractHD 116745 is an eleventh magnitude early F-type giant occurring in the field of the globular cluster ω Cen. Membership in the cluster appears virtually certain since the star’s radial velocity differs insignificantly from the mean cluster velocity of +238 km s-1. HD 116745 lies nearly 4 mag. above the horizontal branch in the HR diagram and is presumably in a rapid, advanced stage of evolution. Spectrograms at 22.5 Å mm-1 and 155 Å mm-1 have been obtained by one of us (R.J.D.) at the Radcliffe Observatory in South Africa using a McGee spectracon image tube. The lower dispersion spectra have been used to measure Hy profiles and the Balmer discontinuity, and one high dispersion film has provided the basis for a differential curve-of-growth analysis with respect to the Sun in order to determine some heavy element abundances. Physical data derived for the star are Mv= –3.32, θe=0.77±0.02, logg = 1.0±0.3 and Results of the curve-of-growth analysis, in which a model atmosphere was used to determine the curve appropriate to the star, yield a logarithmic iron-to-hydrogen abundance ratio with respect to the Sun of [Fe/H]= —1.2 with a provisional estimated uncertainty of about +0.2. This result is based on 28 lines of Fe i. Ti may be marginally overabundant, with a value of [Ti/Fe] = + 0.4, based on 7 lines of Ti II. Other elements and ionization states identified are Mg I, Al I, Si I, Ca I, Sc II, VI, VII, Mn I, Sr II, Zr II (Eu II).
On the fragmentation of asteroids
Authors: Levin B. J. 
Published: July 2016

AbstractMembers of each family or stream of asteroids represent fragments of a single collision of two parent asteroids. Therefore the mass distribution for family members is at the same time the distribution for such fragments. For 4 families with large numbers of known members the mass distribution can be approximated by an inverse power low withs≈ 1.7–2.0. The comparison of distributions for big and small members of these 4 families shows that the Palomar-Leiden Survey of faint asteroids contain about 1/60 of their true number which is thus of about 120000. About 1/3 of families contain from 1 to 4 big asteroids more than 10 times more massive than the remaining. Among 49 asteroids revealed to be of variable brightness, 18 are members of asteroid families and 17 of the latter are their biggest members.
Development of the theory of planetary perturbations in non-classical cases
Authors: Petrovskaya M. S. , Ivanova T. V. , Lobkova N. I. 
Published: July 2016

AbstractThree expansions of the perturbation function R have been suggested which remain valid when planetary orbits have points equidistant from the Sun. In the first two cases the exterior summations are extended over the powers of the eccentricities, whereas the interior series is developed in functions of the ratio of the semi-major axes. At the same time, factors have been found which could be carried out of the sums and represent the poles of R in an asymptotic case (the circular intersecting orbits of the same radius). In this way the convergence of the series is increased considerably for large values of the semi-major axes ratio. The third expansion differs from the previous ones by having the exterior sum with respect to the functions of the ratio of the semimajor axes, the interior expansions being in powers of eccentricities. This development of R may be useful in situations where the eccentricities are rather large and the distance between orbits is not too small.
Perihelion longitudes and Jacobi constants of Jupiter group comets as indicators of their possible origin from the two equilateral Trojan clouds
Authors: Rabe Eugene 
Published: July 2016

AbstractThe perihelion longitudes of the Jupiter comets can be divided into two unequal groups, associated with (π4– 60°) and π4– 60°), respectively. This finding favors the authors earlier suggestion that many of these comets may have originated from the correspondingL5andL4Trojan clouds, which today are known to contain many hundreds of Trojans brighter than magnitude 20.9. The proposed origin of the Jupiter group comets is supported also by the finding that the preceding Lagrangian pointL5is associated not only with distinctly more Trojans but also with more comets thanL4, as well as by the association of the largest Trojans with the larger and denser cloud aroundL5. The larger size of theL5cloud is suggested by the association with it of a significant number of comets with smaller Jacobi constantsCthan those found in theL4cloud. All the observed distribution anomalies, of the Trojans as well as of the Jupiter group comets, would follow automatically from the assumption that both groups of bodies originated from two primordial clouds of matter associated with the equilateral regions. These two clouds would have been of unequal size and density, perhaps due to some initial by-chance irregularities in the uniformity of the relevant parts of the solar nebula. As to the long-range survival of volatile matter embedded in solids, certain observations encourage the assumption of such a possibility, while simplified theoretical considerations apparently do not suffice to produce any meaningful constraints.
Nongravitational effects on comets: a progress report
Authors: Marsden B. G. 
Published: July 2016

AbstractNew developments since 1970 are discussed, notably the identification of the comets exhibiting sudden anomalies in their motions with those comets whose nongravitational effects normally increase with time (resulting in the eventual complete dissolution of these comets, rather than conversion into asteroidal objects) and the introduction of a law for the variation of the nongravitational forces with heliocentric distance that is based on the theory of vaporization of ice.
The vaporization of the volatile fraction in comets
Authors: Delsemme Armand H. 
Published: July 2016

AbstractVery large gas productions have been recently established for comets. They rule out desorption models of the cometary nucleus and strongly support the vaporization of an icy conglomerate. The vaporization theory of the cometary nucleus can also be used to predict, for different types of ice, the law of dependence of the non-gravitational force on heliocentric distance. The results are compared here with the empirical dependence that can be derived from Marsden’s recent work on comet Schwassmann-Wachmann II. The law, as deduced from this comet’s observations, rules out the vaporization of all gases with high vapor pressure, like CO, CH4, NH3etc., and even CO2, but coincides surprisingly well with a vaporization controlled by the latent heat and vaporization rate of water, as would be the case for pure water ice or for solid hydrates of gases. The fact that the gas molecules encaged in the cavities of the solid hydrates would simply be liberated in proportion by the vaporization of their water, seems therefore o be confirmed by the present results.
Automated Search for Flare Stars Continued
Authors: Winterberg J. , Nolte M. , Seitter W.C. , Duerbeck H.W. , Tsvetkov M.K. , Tsvetkova K.P. 
Published: July 2016

To date we obtained 511 blue plates with multiple exposures of nine young clusters and associations to be used for studying the flare activity-age relation. First attempts showed already that automatic search increases the number of discovered flares by 50% compared to visual inspection (Aniol et al. 1989). Improved algorithms have now been implemented and applied. Automated object identification in existing catalogues (FSDB, GCVS, SIMBAD) is also available.All plates are digitized with the PDS 2020 GMplus microdensitometers at AIM and reduced with the AIM software. Steps following the reconstruction of images include the transformation of plate to sky coordinates and matching of the multiple exposure chains with the stars on the deep reference plate. All complete chains (generally six exposures) are used to derive average light curves for all objects. For each magnitude interval 10-11, 11-12, … 15-16 the mean deviation and standard error of an image from the overall mean value of the respective chains is determined. If any image in a chain differs by more than a preset multiple of the mean error it is considered a potential flare event and registered for visual inspection, together with the chains immediately preceding and following the suspected flare event, to obtain information on the total duration of the outburst. The candidates are filed and the data of all stars are stored for checks of long-term variability.
The Role of Flare Stars in Cosmic-ray Origin
Authors: Shapiro Maurice M. 
Published: July 2016

AbstractSupernovae and their expanding shock fronts are evidently the main agents of cosmic-ray acceleration. The thermal gas in the interstellar medium has been regarded as the reservoir of seed particles destined to become cosmic-ray nuclei. This assumption is, however, at variance with the source composition of galactic cosmic iays. In an alternative hypothesis, the seed particles are injected into the interstellar material as suprathermal seed ions, and it has been surmised that flare stars provide the initial boost. We find that the dMe and dKe stars are probably the principal sources of cosmic-ray seed particles. Most stars in the Galaxy are red dwarfs and many of these flares much more powerfully and frequently than solar flares. Augmenting the optical data, recent X-ray and far-ultraviolet observations now permit a better estimate of the energy budget. Altogether, dMe and dKe stars seem to be the most promising class of cosmic-ray injectors.
Long-term Photometry of the Symbiotic Star AG Draconis
Authors: Luthardt R. 
Published: July 2016

Photoelectric UBV-observations of the well known symbiotic star AG Draconis were obtained between 1982 and 1984 with the 60cm photoelectric reflector II of Sonneberg Observatory. The light curve shows two large optical outbursts: (at JD = 244 5000…5500 and JD = 9000…9500) and two smaller eruptions (at JD = 6200, 6600). The recent outburst is the largest one since 1952.During the quiet stage a significant variability with an amplitude of about one magnitude is only visible in the U-band. L. Meinunger (1979) detected a period of 554 days and calculated the following ephemeris:Umax = 243 8900 + 554 · EAll outbursts and smaller eruptions are correlated with the period of the U-maxima, the outburst maxima always coincide with U-maxima of the quiet stage, calculated by the above formula.
TTM Observations of X1755-338
Authors: Pan H.C. , Skinner G.K. , Sunyaev R.A. , Borozdin K.N. 
Published: July 2016

X1755-338 is an X-ray binary source which displays X-ray dips with a 4.4 hour period (White et al. 1984). It was previously noted as an unusually soft X-ray source by Jones (1977) and was suggested later as a black-hole candidate (BHC) by White & Marshall (1984), and White et al. (1984), based on the similarity of its location in an X-ray colour-colour diagram to that of a group of BHCs.The TTM is a coded-mask imaging spectrometer on board the KVANT module of the MIR space station. It is capable of producing images in the 2 – 30 keV band with an energy resolution of about 18% at 6 keV. The instrumental details are given in Brinkman et al. (1985).We observed X1755-338 in 1989 March-September during the period of the TTM Galactic Centre Survey.
Oblique Pulsator Model for the Blazhko Effect of RR Lyrae Stars
Authors: Shibahashi Hiromoto , Takata Masao 
Published: July 2016

AbstractBy assuming that the RR Lyrae stars have fairly strong dipole magnetic fields with the symmetry axis oblique to the rotation axis of the star, we show that the oscillation mode which would be a pure radial oscillation in absence of the magnetic field has a quadrupole component, which is axisymmetric with respect to the magnetic axis. The aspect angle of the quadrupole component changes due to the stellar rotation, and this apparent variation is interpreted as the Blazhko effect in RR Lyrae stars.
New Results on Pulsating OB Stars
Authors: Moskalik Paweł 
Published: July 2016

AbstractUntil very recently the physical mechanism driving oscillations in β Cep and other early type stars has been a mystery. The breakthrough came with the publication of new OPAL and OP opacity data. Model calculations with the new opacities have demonstrated that the pulsations are driven by the familiar K-mechanism, acting in the metal opacity bump at T ≈ 2 × 105K. The mechanism excites the low order p- and g-modes in the upper part of the instability strip and the high order g-modes in the lower part of the strip. The theoretical instability domains agree well with the observed domains of the β Cep and the SPB stars. In this review I present these recent theoretical results and discuss their consequences for our understanding of B stars pulsations.
Variable Stars in the MACHO Collaboration Database
Authors: Cook Kem H. , Alcock C. , Allsman R.A. , Axelrod T.S. , Freeman K.C. , Peterson B.A. , Quinn P.J. , Rodgers A.W. , Bennett D.P. , Reimann J. , Griest K. , Marshall S.L. , Pratt M.R. , Stubbs C.W. , Sutherland W. , Welch D. 
Published: July 2016

AbstractThe MACHO Collaboration’s search for baryonic dark matter via its gravitational microlensing signature has generated a massive database of time ordered photometry of millions of stars in the LMC and the bulge of the Milky Way. The search’s experimental design and capabilities are reviewed and the dark matter results are briefly noted. Preliminary analysis of the ~ 39,000 variable stars discovered in the LMC database is presented and examples of periodic variables are shown. A class of a periodically variable Be star is described which is the closest background to microlensing which has been found. Plans for future work on variable stars using the MACHO data are described.
HIPPARCOS Data on Pulsating Stars
Authors: Turon Catherine , van Leeuwen Floor 
Published: July 2016

AbstractThe preliminary astrometric and photometric results obtained from the first 30 months of HIPPARCOS data are presented. Examples of the results obtained for the various categories of pulsating variables included in the HIPPARCOS programme are given. The perspectives opened by GAIA (Global Astrometric Interferometer for Astrophysics), the concept for an astrometric interferometer submitted in September 1994 to the ESA Horizon 2000+ survey committee, are briefly exposed.
Search for Pulsational Instability among h Persei Stars
Authors: Krzesinski J. 
Published: July 2016

AbstractThe northern-hemisphere double cluster h and χ Persei is one of the richest young open clusters. At least half of the brightest stars in the cluster appear to be variables and most of them axe Be stars. Till now there was no evidence for the presence of β Cephei stars in the cluster. It is remarkable that the similar age southern cluster NGC 3293 and other clusters belonging to the same age group are documented as clusters in which β Cephei stars have been observed. In this work we report finding one suspected β Cephei-like object, basing on our own observations.
Long-term Photometric Monitoring of Cool Hydrogen-deficient Carbon Stars
Authors: Cottrell P.L. , Gilmore A.C. , Kilmartin P.M. , Lawson W.A. 
Published: July 2016

Interest in the hydrogen-deficient carbon (HdC) stars, and the R Coronae Borealis (RCB) stars in particular, has been rekindled by the realisation that these stars provide the potential for testing models in a number of areas. These include: pulsation theory; grain formation; grain evolution; stellar nucleosynthesis and extended stellar atmospheres.Observational work on these objects has increased dramatically over the last 10 years. This has included both spectroscopic and photometric projects, see Lambert & Rao (1994) and Lawson et al. (1990).We have continued to observe a number of the cool HdC stars in the Galaxy and the LMC and now have light curves exceeding 2000 days in duration for many of these objects. In particular, we are observing the RCB stars to investigate both the low amplitude, pulsation-related variations present at maximum light and the photometric behaviour during the large amplitude declines.
Superhumps in the SU UMa Star AK CNC
Authors: Mennickent R. , Nogami D. , Kato T. , Worraker W. 
Published: July 2016

AbstractWe have observed AK Cnc during the 1995 March superoutburst, by means of differential V – U photometry. The observations were obtained at Las Campanas (Chile), Ouda Station (Kyoto, Japan) and in England. Superhumps with amplitude 0.2 mag appeared at least 4d after maximum. They evolved from a single peak structure, developing a secondary peak during decline, until they reached a double-wave modulation with 0.05 mag amplitude, after 8 d. After removing linear trends in our data, the following ephemeris was found:This superhump period was confirmed, independently, with our homogeneous set of 462 V magnitudes, obtained at LCO, then adding 63 U data points and finally considering all the dataset, consisting of 789 V + U magnitudes. The superhump period is slightly larger than that reported by Kato (1995) during the 1992 January superoutburst (0.06735(5)d). Our results imply an orbital period Porb = 0.065(2) d, using the relationship given by Howell & Hurst (1994). The eruption duration was ≳ 10 d, and its amplitude > 6 mag. An abrupt and short luminosity decrease occured ≈ 12 d after maximum. Eleven outbursts have been observed since 1992 January, being the minimum reported lag between successive eruptions: 40 d. More details will be given in a future publication.
A Quantitative Study of Limb Darkening in Accretion Disks
Authors: Diaz M. P. , Wade R. A. , Hubeny I. 
Published: July 2016

AbstractThe UV emission of accretion disks was synthesized for a grid of optically thick models that cover the high-Ṁ nova-like regime, aiming to quantify the effect of limb darkening in the integrated and radially resolved spectrum of the disk.
Disk Instabilities in the Black Hole Binaries
Authors: Cannizzo J. K. 
Published: July 2016

I will briefly review recent progress in our understanding of the global propagation of accretion disk instabilities operating in interacting binary systems in which the accreting star is a ~ 10 M⊙ black hole. A detailed discussion of this work can be found in Cannizzo, Chen & Livio (1995).The X-ray light curves of the brightest and best studied X-ray novae – systems such as A0620–00, GS2000+25, GS1124–68, and GRO J0422+32 – are notable in two respects: the rise times are fast (a few days) and the decays have an exponential character, where the e–folding time constant is about 30 to 40 d (Mineshige, Yamasaki, & Ishizaka 1993, hereafter MYI). It is noteworthy that outbursts in dwarf novae also decay exponentially, with the time constant being about a factor of 10 shorter. In this contribution I will discuss the constraints on the physics of accretion disks which the (observed) exponential decay enables us to make.
Radio Emitting X-Ray Binary Stars
Authors: Spencer R. E. 
Published: July 2016

Some of the most astrophysically interesting objects are found among the radio-emitting X-ray binary stars (REXRB). The class includes the well-studied objects such as SS 433, Cyg X-3 and Sco X-1. The recent discoveries of relativistic ejection of radio knots in the X-ray transients 1915+105 (Mirabel & Rodriguez 1994) and 1655–40 (Hjellming & Rupen 1995) well illustrate the extreme nature of some of these objects.X-ray binaries are semi-detached binary stars in which matter is transfered from a more or less normal star onto a neutron star or black hole. X-ray satellites have detected large numbers of these objects (193 in a recent catalogue by van Paradijs 1995). However only a small fraction of these are known to have radio emission (e.g. Hjellming 1988).