bluuebunny/crossref_metadata_2025 huggingface dataset:
A Study of the Irradiation of Secondaries of Algol Binaries
Authors: Gimenez A. , Claret A.
Published: July 2016

In order to investigate the effects of irradiation on the spectra of the cooler components of Algol binaries, a modified version of the Upsalla Model Atmosphere code (U.M.A.) has been used. The upper boundary condition was changed to take into account the external radiation field and an automatic procedure to prevent numerical oscillations was introduced. In order to simulate the external flux from the hot component we have used the Kurucz grid interpolated for the wavelenghts adopted in U.M.A. code. Since secondary stars of Algoltype binaries normally have deep convective layers, we impose the condition that the entropy of these zones must be the same in the irradiated and in the non-irradiated models.
AY Vulpeculae
Authors: Walker R.L.
Published: July 2016

The star AY Vulpeculae was recognized as variable and labeled as an Algol-type system by Hoffmeister, (A.N. 242, 133, 1931). Koch et al. (I.B.V.S. 1709 1979), included it in their list of eclipsing binaries for which photoelectric work was needed. The system is faint, but because its primary minimum is very deep it is of astrophysical interest. The observations of the present investigation represent the first definitive photometric study made of AY VUL and is one of several systems with periods greater than two days being observed with the 1.0 meter Ritchey-Chretian reflector at the Flagstaff Station . A total of 1242 observations of AY Vul (406 in V, 417 in B, and 419 in U) were obtained on 12 nights in 1986.

Orbital elements for AY VUL were obtained by using the Wood model, and the calculations were performed on the VAX 11/750 computer at the Flagstaff Station of the U. S. Naval Observatory. AY Vulpeculae can be regarded as a classical Algoltype semidetached system in which the secondary component fills its Roche lobe, while the primary lies well inside its own lobe. Both eclipses are partial. The orbital elements are listed below.
UV Observations of Three Classical Novae during Early Stages of Decline
Authors: Drechsel H. , Wargau W. , Rahe J.
Published: July 2016

We present IUE UV spectra of the three recent classical novae N Sgr 1982, N Ser 1983, and N Mus 1983, obtained during early decline, transitional stage, and nebular phase, respectively. The line spectra are discussed. Preliminary conclusions concerning CNO over-abundances, shell geometry, and speed classes are drawn.
Cataclysmic Variable Stars
Authors: Bath G. T.
Published: July 2016

The properties of cataclysmic variable outbursts are reviewed, and interpreted in terms of dynamical instabilities by the red component, and subsequent evolution of the white dwarf accretion disc subject to a mass transfer burst in the transfer stream.
The Hα Line Profile in Early Type-Binary Systems HD 47129 and γ Velorum
Authors: Rajamohan R.
Published: July 2016

A brief description of the variation of the Hα Line profile in γ Velorum and HD 47129 is given.
The Light Variability of BD + 25° 2511
Authors: Raveendran A. V.
Published: July 2016

Photometry of the spectroscopic binary BD + 25°2511 obtained during the 1981, 1982, and 1983 observing seasons shows that it is a variable with a period of about 3.5 days.
A Review of Early-Type Close Binary Systems
Authors: Leung K. C.
Published: July 2016

This is a review of close binary systems with very early spectral types (B, O, Of, and WR stars). We limit our selection to systems with Roche model photometric solution only. There are 10 contact systems known at present. Three of them (V701 Sco, BH Cen, and RZ Pyx) are located in the vicinity of the zero-age contact (ZC) according to a Spectral Type - Period diagram. Only the first two systems have absolute dimensions available. Both of these fall into the ZC zone in the logP - logm diagram and the logm - logR diagram. The system TU Mus was thought to be a ZC system is located in the evolved contact zone (EC) in the above diagrams. Both V701 Sco and BH Cen were thought to be having mass ratios about unity. With the much improved light curves of BH Cen and new analysis the mass ratio has been revised to 0.84! This result may favor Shu's model for early-type zero-age contact systems. The evolved systems might be undergone Case A mass exchange except for two systems (V729 Cyg and RY Set) which might be from Case B. The systems V367 Cyg was classified by Plavec as a W Ser system may be a evolved contact system.

It is interesting to note that V729 Cyg (07f + Ofla), UW CMa(07f + O) and CQ Cep(WN7 + O) are all highly evolved contact systems. The Max II of UW CMa and CQ Cep are displaced to 0.78 and 0.80 phase, respectively. The displacement for V729 Cyg is not known due to poor coverage at this phase. The most distinct feature going from Of to Wolf-Rayet stars is the increasing domination of emission lines. It is suspected that this phaseshifts reflect the increasing activity of mass-flow in the common envelope.

There are 8 semidetached systems with reliable absolute dimensions. It is believed that 6 of them are derived from Case A while the remaining 2 are from Case B mass exchange.
A Spectroscopic Study of Epsilon Aurigae
Authors: Saitō Mamoru , Kawabata Shusaku , Saijo Keiich , Sato Hideo
Published: July 2016

Epsilon Aurigae has been observed during ingress and totality between 1982 and 1983 at Okayama. Analyses of profiles of Ha line and of radial velocities of neutral hydrogen and metals show that the secondary component consists of at least three parts in structure.
The Method of Determining Infrared Diameters
Authors: Allen David A.
Published: July 2016

Over the past decade, largely because of the pioneer work of F. J. Low in Tucson, it has become possible to make accurate and reliable astronomical measurements at infrared wavelengths as long as 20 µm. At such wavelengths we see solar system bodies not by reflected sunlight but by their own thermal emission. The larger asteroids, though subtending small angles, give signals at 10 µm comparable in intensity with those from the brightest stars. It is now possible to determine the absolute flux from such asteroids to an accuracy of about 10 percent. Because an asteroid might reasonably be expected to have no atmosphere and no internal source of heat, the thermal radiation it emits must just balance the solar radiation it absorbs, and the measured flux will depend only upon its size. Infrared measurements therefore provide an opportunity to determine the diameters of the brighter asteroids.
Infrared Observations of Asteroids
Authors: Matson Dennis L.
Published: July 2016

This paper is a brief preliminary report about a program of reconnaissance photometry designed to study the thermal radiation emitted from asteroids. Observations of thermal radiation, and their subsequent interpretation, can provide new knowledge that presently cannot be gained by any other method. The emitted thermal power is by and large that portion of the insolation which is absorbed. Part of the asteroid’s emission spectrum can be observed through windows in Earth’s atmosphere. With the aid of models for the details of energy transfer at the asteroid’s surface, and accurate visual photometry, reliable estimates can be made for some of the important parameters in the models. Of particular interest are Bond albedo, size, emissivity, and thermal inertia.
Inferences From Optical Properties Concerning The Surface Texture and Composition of Asteroids
Authors: Hapke Bruce
Published: July 2016

The optical properties of the asteroids are compared with those of the Moon and various terrestrial, lunar, and meteoritic materials. It is concluded that the surfaces of most of the asteroids are covered with at least a thin layer of unconsolidated, fine-grained powder similar to lunar soil. None of the asteroids appear to have compositions corresponding to pure nickel/iron meteorites.
The Alinement of Asteroid Rotation
Authors: Burns Joseph A.
Published: July 2016

Data have been accumulating since the beginning of this century that indicate that most, if not all, large asteroids have periodic lightcurves. The variations that are seen have periods of the order of several hours and can be understood as being caused by bodily rotation, accompanied by changes in shape and/or surface properties. Because corresponding color changes are usually absent, the former explanation of a variation in cross section is probably the correct one.
Trojans and Comets of the Jupiter Group
Authors: Rabe Eugene
Published: July 2016

In a recent paper (Rabe, 1970), I suggested that at least some comets of the Jupiter group may have originated from the relatively dense Trojan clouds that, according to a recent survey by the van Houtens and Gehrels (1970), seem to be associated with the equilateral points L4 and L5 of the Jupiter orbit. This suggestion was inspired by the finding that the periodic comet Slaughter-Burnham has been captured (or perhaps recaptured) into unstable or temporary “Trojan” librations lasting approximately 2500 yr and by the circumstance that the Jacobi “constants” of most Jupiter group comets have values between 3.0 and 2.5, or just in that range which would also be occupied by all known and unknown Trojans associated with Jupiter in stable or unstable librations involving heliocentric eccentricities up to about 0.5 and inclinations as large as 30°. Moreover, it is well known that nearly all comets of the Jupiter group are able to approach Jupiter rather closely, thus providing the possibility for such drastic orbital changes as temporary capture into, or escape from, librational motion of the Trojan type. All, presumably stable, orbits of actual Trojan planets presently known have eccentricities e not exceeding 0.15, but we also know that stable short-period librations with much larger e values do exist in the restricted Sun-Jupiter problem, so that even in the real, nonrestricted situation there should be a possibility for corresponding librations with these more substantial short-period components. These librations may be unstable but may have long lifetimes nevertheless. The case of P/Slaughter-Burnham has proved that such motions are indeed possible, even with an e as large as 0.52.
Absolute Intensity Calibration at 26 Å by Branching Ratios to the Visible
Authors: Irons F. E. , Peacock N. J.
Published: July 2016

The technique for absolute calibration using the branching ratio of two transitions which have a common upper level but widely separated energies has been employed and described by Griffin and McWhirter (1961).

Using the plasma produced by irradiation of a carbon target with a 1 GW, 6 nsec duration, neodymium laser pulse, we have been able to calibrate a grazing incidence spectrograph at the wavelength (25.83 Å) of the 7–1 transition in C VI by direct comparison with the intensity of the 7–6 (3434 Å) transition emitted from the same ions in the plasma. The spectrum from a similar carbon plasma has been described by Boland et al. (1968) and in several ways is ideal for this type of measurement.
Identifications of Some Highly-Ionized Iron and Nickel Lines in the 200–400 Å Region of the Solar Spectrum
Authors: Widing K. G. , Sandlin G. , Cowan R.
Published: July 2016

A number of previously unclassified multiplets of FeXIV, XIII, XII, and XI produced by transitions of the type 3s23pn–3s3pn+1 are identified in the XUV spectrum of the Sun. The iron lines account for most of the previously unidentified strong lines between 330 and 370 Å. Solar observations of especial value for the investigation of the 300–400 Å region were the slitless spectroheliograms of September 22, 1968 (Purcell and Tousey, 1969) and November 4, 1969 (Tousey, 1971) – on which the image of a flare was recorded.

Other solar identifications in the same spectral region include the resonance lines of NiXVII and NiXVIII, and one 3p–3d multiplet of FeXIII. The solar blend at 417 Å involving the FeXV inter-combination line and SXIV is resolved.
On Special Features of Non-Thermal Solar X Radiation above 10 keV
Authors: Elwert G. , Haug E.
Published: July 2016

The polarization and angular distribution of solar hard X radiation above 10 keV was calculated under the assumption that the X rays originate as bremsstrahlung from energetic electrons moving in a preferred direction. The source electrons are supposed to have a power-law spectrum. These conditions are to be expected in the impulsive phase of an X-ray burst. The spiral orbits of the electrons around the magnetic field lines are taken into account.
The Periods of Cataclysmic Variable Stars
Authors: Robinson Edward L.
Published: July 2016

To understand the structure and evolution of the cataclysmic variables, we will need accurate values for their masses, dimensions, mass transfer rates, and other physical properties. Unfortunately, despite an abundance of observational data on these systems, there is a severe dearth of reliable, quantitative information about their fundamental physical properties. Only two cataclysmic variables, U Gem and EM Cyg, are simultaneously eclipsing binaries and double-lined spectroscopic binaries, and only for these two systems can masses and dimensions be determined with a minimum of assumptions (Stover 1981a; Stover, Robinson, and Nather 1981). Even if there were more systems like U Gem and EM Cyg, it is not obvious that our information would be any more reliable, because observers are often unable to agree on the values of the directly measured quantities used to determine physical properties. Thus, the radial velocity curve of the brightest dwarf nova, SS Cyg, has been measured independently 5 times in the last 30 years. The agreement among the measurements is unsatisfactory, and the reasons for the disagreement are not completely understood (Joy 1956; Kiplinger 1979; Stover et al. 1980; Cowley, Crampton, and Hutchings 1980; Walker 1981). The physical properties may still be unreliable when the disagreements are understood and eliminated, because there is considerable uncertainty about the proper way to extract physical properties from observational data. For example, the observed radial velocity curves of cataclysmic variables are believed to be different from the true radial velocity curves of their component stars, but the amount of difference and ways to correct for the difference are unknown.
Humps and Superhumps
Authors: Bath G.T. , Edwards A.C. , Mantle V.J.
Published: July 2016

It is now well established, following the classic work of Smak, Warner and Nather, that discs in dwarf novae possess an anisotropic radiation pattern responsible for the hump, or shoulder, that occurs prior to eclipse in the quiescent state, and, in systems with suitable inclination such as TT Gem, responsible also for the primary eclipse itself. In systems with higher inclination such as Z Cha, the primary eclipse is composed of both this anisotropic disc component and the inner-disc/white-dwarf primary component.
X-Ray Emission from Cataclysmic Variables
Authors: Lamb D. Q.
Published: July 2016

We review X-ray observations of cataclysmic variables and theoretical work on X-ray emission from them, emphasizing recent developments.
Photometric and Spectroscopic Variability of the Hydrogen-Deficient Binary CPD-58°2721
Authors: Morrison K. , Drilling J.S. , Heber U. , Hill P.W. , Jeffery C.S.
Published: July 2016

The hydrogen-deficient star CPD-58°2721 (=LSS1922) has been observed to show radial velocity variations with a range of 140 km s−1. It shows light and colour variations with amplitudes of 0T07 on a timescale of about 9 days. The absorption spectrum is nitrogen-rich and is seen to vary on a short timescale (4 days). CPD-58°2721 therefore appears to be a hydrogen-deficient binary similar to KS Per and v sgr. The photometric variability is attributed to radial pulsation.
Evolutionary Status and Origin of Extremely Hydrogen-Deficient Stars
Authors: Schönberner D.
Published: July 2016

Our present knowledge about the evolutionary status of extremely hydrogen-deficient stars is reviewed. Possible schemes for their creation are discussed, with special emphasis on a recently proposed binary scenario, according to which they are the result of the merging of two white dwarfs. Finally, the possible generic links between the different groups of extremely hydrogen-deficient stars are briefly discussed.
The Nonhomogeneous Distribution of Abundances and the Magnetic Field Measurements in CP Stars
Authors: Catalano F.A.
Published: July 2016

The influence of the non homogeneous distribution of the abundance of elements on the magnetic field measurements in chemically peculiar stars is discussed.
Spectrophotometry of the Broad Continuum Features in Magnetic AP Stars
Authors: Pyper Diane M. , Adelman Saul J.
Published: July 2016

The strongest broad absorption feature in the peculiar energy distributions of the Ap stars is that centered at about 5200 Å, thus the Stromgren y band and the Geneva VI band are most affected in stars in which this feature is strong. Fig. 1 shows bandpasses (full width at ½ intensity maximum) of three widely used photometric systems superimposed on two of our scans of Ap stars and two solar abundance line blanketed model atmospheres (Kurucz 1979). It is seen that both the y and VI bands fall entirely within the λ5200 feature. The plot (Fig. 2a) of b-y vs. Tpc (the color temperature of the red end of the Paschen continuum), shows that the b-y colors for most of our sample of Ap stars are displaced to the blue of the b-y, Teff relationship of Relyea and Kurucz (1978). In Fig. 2b, Δ(b−y) = (model b−y) − (observed b−y), for a given temperature is plotted vs. ΔWS2(5200), a spectrophotometric index measuring the equivalent width of the λ5200 feature. There is a strong correlation between Δ(b-y) and ΔWS2(5200), indicating quantitatively the large effect of the λ5200 feature on the y band, previously discussed by Adelman (1979). The deviations in Ap star B2-G values from the normal star B2-G vs. T curve are much less than for b-y, as the Geneva G band is largely outside the λ5200 feature (Fig. 2c). Thus B2-G is a better temperature indicator for Ap stars than is b-y (also see Hauck and North 1982).
β Lyrae - A Binary System with Anomalous Abundances and Magnetic Field
Authors: Skul'skij M.Yu.
Published: July 2016

Study of dependence of chemical abundance on conditions of excitation within the limits which could exist in the atmosphere of bright component have led to conclusion that by no modification of physical parameters a “normal” abundance of chemical elements in the atmosphere can be obtained. The variable effective magnetic field with mean value (−1350±50) Gauss is discovered.
Gallium Overabundance in the Ap-Si Star HD 25823
Authors: Artru Marie-Christine , Ferrero Rubens Freire
Published: July 2016

An anomalous enhancement of the resonance line of Ga II at 1414.44 Å is observed in IUE spectra of the silicon star HD 25823. High-resolution spectrum of this star is compared to synthetic spectra calculated in the range 1406–1422 Å. The LTE abundance of gallium is evaluated to log NGa = 6.3 ± 0.5 in the scale where log NH = 12.
Lithium in Am and δ Del Stars
Authors: Burkhart C. , Lunel M. , Coupry M.F. , Van’t Veer C.
Published: July 2016

High-resolution observations of the doublet LiI-6707 A were made to study the abundance of lithium in a sample of Am, δDel, and reference stars. It is found that Am and δDel stars may be underabundant, normal or overabundant in lithium (normal Li abundance meaning log NLi = 3.0 with log NH = 12).
The LI I 6708 Feature in CP Stars
Authors: Faraggiana R. , Castelli F. , Gerbaldi M. , Floquet M.
Published: July 2016

Preliminary results are presented on the behaviour of the feature at 6708 Å; the location of the observed feature coincides with the doublet of Li I 6707.761 and 6707.912 Å.
Seventeenth-Century Solar Observations: Fundamental Results with Amateur Instruments
Authors: Ribes-Nesme E. , Ribes J.C.
Published: July 2016

The equipment used by professional astronomers in past centuries was no better than that used by modern amateurs. Systematic observation of the Sun began in the 17th century and continuity of observations is very important for understanding the solar cycle.

Results obtained from historical observations were presented, in particular covering the Maunder Minimum.

Continued systematic observation is important for the understanding of long-term solar-terrestrial relations.
Sailors and Astronomy
Authors: Demerliac Antoine
Published: July 2016

Sailors are neither professional nor amateur astronomers, but people who have to observe the sky in the course of following their professional calling. As soon as sailors ventured far from the coast they required some guide and even in antiquity (as shown by mentions in Homer’s Odyssey and, considerably later, by Aratus) they used Ursa Minor and Ursa Major. With journeys farther afield, they gained some insight into latitude from the changes of the altitude of the circumpolar constellations above the horizon.

Although the very last Viking voyagers knew of the magnetic compass, earlier ones still relied on the Sun and the stars. Describing the methods used, Harald Akerlund says “One saga mentions a man, Oddi Heldagon, who was known as “Oddi the Star” and who served as long-distance pilot for an Icelandic magnate towards the end of the 900s. He left notes that included a complete table of the changes in declination of the Sun throughout the year, expressed as the height of the Sun on the meridian in semi-diameters. There is also a small table of azimuths giving the direction at different times of the year, of dawn twilight, defined as being a faint band of light on the horizon, visible before sunrise. We know nothing of the instrument used to measure the altitude of the Sun.”
Working with Amateur Astronomers
Authors: Edberg Stephen J.
Published: July 2016

Amateur astronomers have a vast store of talent and expertise in making astronomical observations. When carefully channelled, their enthusiasm coupled with these characteristics can lead to the acquisition of large volumes of high-quality astronomical data. The Amateur Observation Network of the International Halley Watch (IHW) was organized to encourage comet observations by amateurs, standardize techniques whenever possible, and then collect and archive these observations for use by the astronomical community in the near and distant future as part of the whole IHW archive. The lessons learned from this experience will be useful to organizers who plan observation campaigns involving amateur astronomers in the future.
Solar Spectroscopy with a CCD
Authors: Saint-Pé Olivier
Published: July 2016

The design of a spectrograph having spatial resolution and using a linear CCD was described, together with the optical solution adopted (an Ebert device) and the processing applied to the data obtained.
A Study of Disconnection Velocities in the Plasma Tail of P/Halley
Authors: Caron Roland , Koutchmy Serge , Sarrazin Michel
Published: July 2016

During a photographic campaign on Comet P/Halley in 1986 April, a considerable number of photographs were obtained, especially on April 8, of a disconnection event in the plasma tail. Initial details were presented at the Symposium in Heidelberg at the end of 1986.

The photographs were obtained with a camera five examples of which were specially constructed (by Carron), and known as the K600. The objective is a 100-mm OG, focal length 600 mm and the image is corrected with a field lens. The camera body is a Hasselblad, taking 120 roll film, which was Agfa 1000.
Chromospheric Eruptions Observed with a Wide Slit
Authors: Costard François
Published: July 2016

The method of placing the solar limb tangential to the slit, which is then widened, has been employed. The following phenomena have been observed: fast radial motion of low loops; extension of the main loop into the corona; ejection of material from the top of the loop; rotation of the structure as it relaxes.
The European Section of IOTA: Scientific Programme Coordination and Results
Authors: Breisker W. , Bode H.J.
Published: July 2016

Lunar occultations and occultations of stars by planets and asteroids are important tools in determining astrometric information as well as details about the occulting bodies. Successful work requires a relatively large number of small observatories, well-distributed over a large area of the Earth. This is particularly important in occultations by asteroids because the accuracy of the predictions is generally poor.

Cooperation is therefore essential. IOTA/ES (European Section of the International Occultation Timing Association) provides a means of cooperative work, and holds meetings in different European countries about once a year. Eastern European countries are included.

Some results of occultations were presented and future events discussed. A relatively cheap photoelectric system was described, very suitable for amateurs and public observatories.
Astronomical Publications
Authors: de la Cotardière Philippe
Published: July 2016

The glory of the heavens is available to everyone, and anyone, whatever their level of scientific knowledge, is able to appreciate their beauty, poetry and mystery. They are a window to the inaccessible and the unknown and have always attracted attention and aroused Man’s curiosity. This natural fascination for the universe is a precious card in the popularization of astronomy. Three centuries ago, Fontenelle knew how to exploit it in his Entretiens sur la pluralité des mondes, which made him famous. Many others followed him in the 18th and 19th centuries, of which Camille Flammarion may be mentioned especially. Printings of his famous Astronomie Populaire grossed 130000 copies between 1879 and 1924.

Science nowadays does not arouse the same enthusiasm as it did in Flammarion’s day. Since the development of astrophysics, astronomy has become ever more complex, making the task of those who wish to explain new developments more difficult.
The Solar System Promenade
Authors: Tarnutzer Andreas
Published: July 2016

In order to convey the dimensions and relative scale of the Solar System all sizes and distances are reduced by a factor of 109, resulting in a solar diameter of 1.4m, a diameter of 5 mm for Mercury, and a mean Sun–Pluto distance of close to 6 km. Stainless steel models of the planets (and the Moon) are mounted at appropriate distances from a yellow steel sphere representing the Sun. Ten of these Solar System Promenades have been constructed in Switzerland.
Efforts by the Instituto de Astrophisica de Canarias to Publicise Astronomy
Authors: Garcia de la Rosa Ignacio , Cepa J.I. , Kidger M.R. , Mampaso A. , Martinez L. , del Puerto F. , Sanchez C. , Tomas Ll.
Published: July 2016

The Institute provides facilities for school and group visits and these have also included “Astronomical Weeks” (held on more than one of the islands in the group) and yearly open days. In 1985 the formal opening of the Institute engendered so much publicity that at the first open day at the Rocque de los Muchachos Observatory, 15 000 people attended. (The island’s total population is 80 000.) During 1986, a special event organized at a beach on Tenerife was attended by an estimated 70 000 people, thousands more being prevented by an enormous traffic jam. A month later, the inhabitants of La Palma switched off all private and street lights throughout the island for a period of 3 hours. Because of the interest and demand from local people and tourists, additional visitors’ centres are planned.
Main Sequence Abundances: Observational Aspects
Authors: Jugaku Jun
Published: July 2016

Although once it was thought that main-sequence stars are remarkably homogeneous with respect to their chemical composition, the upper main-sequence stars (30000 > Te > 7000) show a variaety of chemically peculiar stars besides the so-called normal stars. Those include the Am, Ap, λ Bootis, He-deficient, and He-rich stars. This review summarizes the current data, which are necessary to construct and test the theoretical models of these stars. In the second half of the review we concentrate on Li. In the lower main-sequecnce stars abundances of Li have been determined in hundreds of stars. Some of the remarkable results are: (1) A uniform upper abundance value irrespective of stellar effective temperature, (2) abundance gap in the F stars of the Hyades, and (3) increasing depletion with smaller stellar mass for the Hyades.
The Point on the Theoretical Changes of Surface Chemistry During Massive Star Evolution
Authors: Maeder André
Published: July 2016

For main sequence stars, the central nuclear processing generally has no effect on surface abundances. Later in the evolution, the newly synthetized elements may be revealed at the stellar surface by processes such as mass loss, convective dredge-up, overshooting, diffusion, rotational and tidal mixing, etc. The changes of CNO abundances are the most conspicuous and the easiest to observe spectroscopically; some abundance ratios like C/N, O/N may undergo changes by more than 102. On the whole, surface chemistry is a most powerful diagnostics of stellar evolution, model assumptions and nuclear cross sections.
Accretion-Disk-Instability Model for Outbursts of FU Orionis
Authors: Hitoshi Hanami
Published: July 2016

The FU Orionis objects show us the abrupt brightening by ~5 map. The two best studied examples, FU ori and V1057Cyg, brightened and have remained very luminous for years and began to fade gradually (cf. Herbig 1977). On the other hand, a large number of young stellar objects have been discovered with energetic molecular bipolar outflows (Lada 1985, for a review). On high-resolution radio observations, the disks have been detected around the central infrared sources (cf. Kaifu et al. 1984, Hasegawa et al. 1984). Most of the disks seem to be perpendicular to the bipolar outflows. These observations suggests that the disk is strongly related with the energetics phenomena like bipolar outflow in star forming regions. (cf.Okuda and Ikeuchi 1986, Hanami and Sakashita 1986, Pudritz 1985, Shibata and Uchida 1985)
Nonlinear Oscillation of the Magnetosphere around Neutron Stars
Authors: Hanami Hitoshi
Published: July 2016

We investigate the unsteady motion of mass reservoir formed by the accretion onto the magnetosphere around rotating neutron stars. The unsteady motion of the reservoir induces secondary accretion to neutron star by R-T instability. The nonperiodic or quasiperiodic phenomena of X-ray bursters seems to be related to this property of mass reservoir on the magnetosphere. We classify the typical dynamical state of the reservoir into three types with the parameters which are accretion rate acc and angular velocity of neutron star Ωs. They are nonsequential oscillation, sequential periodic (quasi-periodic) oscillation, and chaotic oscillation states.
Mass Ejection During Helium Shell Flashes from a Massive White Dwarf
Authors: Saio Hideyuki , Kato Mariko , Hachisu Izumi
Published: July 2016

We have simulated the helium shell flashes on an 1.3 M⊙ white dwarf and estimated the amount of mass loss. Our results may suggest a serious difficulty for the theories of the formation of Type I supernovae and of the accretion-induced formation of neutron stars because a significant amount of envelope mass is ejected during a helium shell flash.
SN 1987a: Calculations Versus Observations
Authors: Wilson James R.
Published: July 2016

In this report the result of old calculations (Mayle 1985; Woosley, Wilson, Mayle 1986; Mayle, Wilson, Schramm 1987) of collapse driven explosions and new calculations of the kelvin-Helmholtz proto-neutron star cooling will be compared with the neutrino observations of supernova 1987a. The calculations are performed by a modern version of the computer model of Bowers and Wilson 1982. (See Mayle 1985 for more recent improvements).

First we give the results of the old calculations. In the collapse, bounce and cooling of the central iron core of a massive star, about 0.1% of the binding energy of the eventual neutron star is emitted in a short deleptonization burst as the bounce shock passes through the photosphere; 5% is emitted in the total deleptonization process; and 95% is released as thermal emission in all neutrino species. In a survey of a wide range of stellar masses, stars in the range 20 to 30 Mθ are found to have the most energetic antineutrino spectra . In calculations where black holes were formed (Woosley, Wilson, Mayle 1986 and Wilson 1971) very little neutrino emission was found associated with black hole formation. The neutrinos associated with BH formation also have low energies. The time history of the neutrino pulse is sensitive to the explosion mechanism. If the mechanism is a prompt exiting through the star of the bounce shock wave, the pulse has a high peak as the shock wave passes near the photosphere. It falls rapidly for the next first few tenths of a second and then declines slowly over several seconds to effectively zero. If no prompt explosion occurs then the shock becomes an accretion shock and matter continues to fall onto the proto-neutron star keeping up the luminosity. After the late time mechanism ejects the envelope the luminosity drops several fold to the luminosity associated with the bare proto-neutron star. During the accretion phase the energy rises to about 15 mev.
Hard X-Rays and Gamma-Rays from SN 1987A
Authors: Itoh M. , Kumagai S. , Shigeyama T. , Nomoto K. , Nishimura J.
Published: July 2016

Gamma-rays originating from radioactive decays of 56Ni and 56Co and hard X-rays due to Compton degradation of γ-rays have been predicted to emerge when the supernova becomes sufficiently thin. The X-ray detections by Ginga (Dotani et al. 1988) and Kvant (Sunyaev et al. 1988) and more recent report of γ-ray detections by SMM (Matz et al. 1988) were much earlier than the theoretical predictions. (See Itoh et al. 1987 and references therein.)

These observations would give important constraints on the distribution of the heavy elements and 56Co in the ejecta. We adopted the hydrodynamical model 11E1Y6 (Nomoto et al. 1988) and carried out Monte Carlo simulation for photon transfer. A step-like distribution of 56Co was assumed where the mass fraction of 56Co in the layers at Mr ≤ 4.6 M⊙, 4.6 − 6 M⊙, 6 − 8 M⊙, and 8 − 10 M⊙ are XCo = 0.0128, 0.0035, 0.0021, and 0.0011, respectively. Other heavy elements were distributed with mass fractions in proportion to 56Co.
Outflow of matter in the chromosphere of α Orionis
Authors: Goldberg L.
Published: July 2016

The spectrum of α Orionis is composite and consist of three components: 1) a photospheric spectrum characterized by symmetric absorption lines more or less typical of the spectrum of an M2 supergiant, except for their very great widths; 2) a shell spectrum consisting of P Cygnitype profiles of neutral and singly-ionized metallic lines of very low excitation potential; and 3) asymmetric absorption lines, including Hα Hβ , Fel lines of intermediate excitation potential and the infrared triplet of Ca+, which appear to be formed in a relatively warm layer, probably an extended chromosphere.
The ultraviolet to infrared spectrum of the large mass loss LMC supergiant S22 = HD 34664
Authors: Muratorio G. , Bensammar S. , Cassatella A. , Friedjung M. , Viotti R.
Published: July 2016

S22 is a peculiar supergiant in the Large Magellanic Cloud whose optical spectrum is characterized by numerous emission lines including Fell and [Fell] (Muratorio 1978). A detailed study performed by Friedjung and Muratorio (1980) led to two main conclusions: (a) A wind with a velocity of 70 km s-1 and a mass loss rate between 4x10-6 and 5x10-5 Mʘ yr-1 is suggested by the examination of the Balmer line P Cygni profiles, (b) The Fell and [Fell] emission lines come from a different region which is optically very thick in the permitted lines. Emission line curve-of-growth methods indicated that the region of line formation has a surface area perpendicular to the line of sight equal to that of a disk perpendicular to this direction with a radius between 3x1013 and 3x1014cm.
The influence of mass loss by stellar wind on the evolution of massive helium burning stars
Authors: Vanbeveren D.
Published: July 2016

Helium burning stars with masses between 10 Mo and 40 Mo are evolved up to core helium exhaustion including mass loss by stellar wind at rates between 10-5 Mo/yr and 10-4 Mo/yr appropriate for WR stars. Different M formalisms were used. It should however be noted that the results presented here are only marginally dependent on this formalism. The initial models contain a small hydrogen shell. The atmospherical hydrogen abundance Xatm = 0.2-0.3. These models correspond to primary remnants (with hydrogen ZAMS masses between 30 M0 and 100 M0) after a case B mode of mass transfer in close binaries, or to stars after a red giant phase of huge mass loss comparable to late case B remnants after Roche lobe overflow. Evolutionary details can be found elsewhere (Vanbeveren, D., Ph.D. Thesis, Vrije Universiteit Brussel) and will not be discussed here. I want to focus on two applications
Peculiarities in the distribution of galactic Wolf-Rayet stars: constraints on evolutionary scenarios?
Authors: Gomez Ana , Lortet Marie-Claire , Pitault Alain
Published: July 2016

The re-examination of the spatial distribution of 158 Wolf-Rayet stars in the Galaxy may help to define different breeds of Wolf-Rayet stars and put constraints on possible evolutionary scenarios.
Formation of a planetary nebula by continuous mass loss
Authors: Harpaz A. , Kovetz A.
Published: July 2016

The evolution of a 1.2Mʘ star along the asymptotic branch with continuous mass loss is presented, showing that this mass loss leads to the formation of a PN with a typical central star in its center.

A former investigation (Harpaz and Kovetz, 1980) has shown that mechanisms for PN creation based on sudden violent processes are not likely to work in the envelope of a red giant star. On the other hand, significant mass loss from red giants was observed as a general phenomenon.

We have followed the evolution of a 1.2Mʘ star along the asymptotic branch, including in the evolutionary calculations a mass loss according to Reimers’ empirical formula. It was found that towards the end of this stage, the mass loss rate was about 2.7xl0-6Mʘ/y, which is consistent with the formation of a typical PN within 30,000 years. When the mass content of the hydrogen rich envelope dropped to 1.5x10-3Mʘ, the star began to contract rapidly, forming a typical central star of 0.6Mʘ
On the consequences of mass loss from intermediate mass stars
Authors: Iben Icko
Published: July 2016

There are two major effects of mass loss from stars of intermediate mass. First, the ultimate fate of such stars--whether they become supernovae of the type that leave no condensed remnant or whether they become white dwarfs--is extremely sensitive to the rate at which they lose mass during the last portion of their nuclear-burning lives. Second, the contribution of intermediate-mass stars to the enrichment of the interstellar medium in helium, carbon, nitrogen, s-process isotopes, and possibly also in iron-peak elements and r-process isotopes is similarly sensitive to mass-loss rates during this last, quiet phase of nuclear burning.
What “masses” for Cepheids?
Authors: Davis Cecil G.
Published: July 2016

To understand the evolution of giant stars, it is important to pin down the masses for Cepheids. The 7– to 10–day “bump” Cepheids imply lower than evolutionary mass (60%). Recent theoretical work, though, indicates that for Cepheids with periods of 15 to 16 days, the best understanding of the light curves results from using evolutionary masses.
Non conservative evolutionary scenario for 100 Algols
Authors: Mardirossian F. , Giuricin G.
Published: July 2016

We have examined the observational data of 100 Algols in order to check the validity of several simple models of non-conservative mass transfer. Strong evidence of mass and angular momentum loss has been found at least in about 20% of our Algols. Case B mass exchange is favoured for low-mass Algols, while case A predominates, though not so widely as expected, in Algols of higher total mass.
Ultraviolet and optical observations of the mass-losing contact binary SV Centauri
Authors: Drechsel H. , Radecke H.D. , Rahe J. , Rupprecht G. , Wargau W. , Wolf B.
Published: July 2016

SV Cen is a well known early-type contact binary. The less massive component is a slightly evolved B1 star. The secondary is of spectral type B4 III. The period of the system is P = 1.6585 days. SV Cen shows with Ṗ/P = -2 10-5 yr-1 one of the largest known period decreases. We carried out ground-based photoelectric and spectroscopic (coudé) observations at ESO, and high dispersion UV observations at VILSPA, with the aim

a) to derive new orbital parameters of SV Cen

b) to determine further epochs of minima (i.e. to study the period variations)

c) to look for possible mass loss indicators in the ultraviolet range.
Evolutionary computations for intermediate mass close binary systems
Authors: van der Linden Th. J.
Published: July 2016

Numerical simulations of the evolution of close binaries with primary mass between 3 and 15 Mʘ and mass ratios of ~ 1.5 were carried out. These results show that after mass transfer the system consists of a bright main-sequence.star together with a faint He-star in a rather wide orbit (p> 60d) Evolution of this kind predicts isotope anomalies for the CNO-elements with respect to their solar values.
Detection of Solar Five-Minute Oscillations of Low Degree
Authors: Scherrer Philip H. , Wilcox John M. , Christensen-Dalsgaard J. , Gough D.O.
Published: July 2016

Solar five-minute oscillations of degree l = 3, 4, and 5 have been observed at Stanford, in the Doppler shift of the Fe 5124 line. The frequencies and amplitudes are in broad agreement with previous observations of modes with l ≤ 3, though we note that there are some systematic discrepancies between the results of different observers.
Statistical Considerations in the Analysis of Solar Oscillation Data by the Superposed Epoch Method
Authors: Forbush S. E. , Pomerantz M. A. , Duggal S. P. , Tsao C. H.
Published: July 2016

Although the method of superposed epochs (Chree analysis) has been utilized for seven decades, a procedure to determine the statistical significance of the results has not been available heretofore. Consequently, various subjective methods have been utilized in the interpretation of Chree analysis results in several fields. The major problem in the statistical treatment of Chree analysis results arises from the fact that in most studies of natural phenomena, data are neither random nor sequentially independent. In this paper, a statistical procedure which takes this factor into account is developed.
Chromospheric Emission and Rotation of Main Sequence Stars
Authors: Catalano S. , Marilli E.
Published: July 2016

Here we present a quatitative approach to the problem of the chromospheric emission and rotation in main sequence stars based on a consistent analysis of recent published data of stars from F8 to K5. This analysis has been performed using the following physical parameters:

a) total power emission in the Call K line, Lk;

b) stellar rotation period, Prot, from chromospheric emission variability;

c) stellar ages from lithium abundance.
Stellar Activity and Calcium Emission Variability
Authors: Baliunas Sallie L.
Published: July 2016

Time series analysis of fluctuations of Ca II H and K chromospheric emission has provided us with much information concerning stellar activity. On all timescales, events which parallel solar behavior can be observed: activity cycles, on timescales of years; rotation of stars and evolution of active areas on timescales of days to weeks; flare-like phenomena on timescales as short as minutes.

We expect that the analogues of solar activity exist on other stars . By studying stellar counterparts to solar activity, we can hope to investigate the physical parameters which are thought to influence chromospheric and coronal activity. The stellar surfaces are usually spatially unresolvable; it is thus difficult to measure directly either small-scale surface inhomogeneities or the associated magnetic fields expected from spatially restricted areas.

On the Sun, however, areas with strong surface magnetic fields show intense chromospheric Ca II H and K emission (Babcock and Babcock 1955; Skumanich et al 1975). Although indirect, the Ca II H and K features are good indicators of stellar magnetic activity. A major advantage of the Ca II features is their accessibility to ground-based observatories. Long-term synoptic programs are in progress to monitor stellar chromospheric activity, and this paper will highlight ongoing work at Mt. Wilson. Monitoring variations of Ca II H and K chromospheric emission over different timescales can reveal different physical phenomena: (1) Long-term (years) variations corresponding to stellar activity cycles; (2) intermediate term (days-months) variations indicating rotation or evolution of stellar active areas; (3) short-term (minutes-hours) variations resulting from impulsive and flare-like phenomena.
RS CVN Stars: Chromospheric Phenomena
Authors: Bopp Bernard W.
Published: July 2016

The observational information regarding chromospheric emission features in surface-active RS CVn stars is reviewed. Three optical features are considered in detail: Call H and K, Balmer H-alpha and Hel λ 10830. While the qualitative behavior of these lines is in accord with solar-analogy/rotation-activity ideas, the quantitative variation and scaling is very poorly understood. In many cases, the spectroscopic observations with sufficient S/N and resolution to decide these questions have simply not yet been made. The FK Com stars, in particular, present us with extreme examples of rotation that may well press our understanding of surface activity to its limits.
On the Distortion Wave in the Short Period RS CVn Type Eclipsing Binary WY Cancri
Authors: Vivekananda Rao P. , Sarma M.B.K.
Published: July 2016

The eclipsing binary WY Cancri (G5 V, M2 V), having a period of od. 82937122, has been classified as a short period RS CVn type binary (Hall, 1976). Chambliss (1965), Oliver (1976, Sarma (1976), Awadulla and Budding (1979) have reported observations of this system. In order to determine a more reliable period of the distortion wave, its source, nature and period of the overall luminosity change from one observing season to the next, we have included this star in the observing schedule of RS CVn binaries at our observatory. Observations were made in standard UBV filters using the ^48-inch reflector telescope of the Japal-Rangapur Observatory. The stars BD+28° 1672 and BD+27° 1701 were used as a comparison and check stars respectively.
Preliminary Results of a Five-Year Survey of Radio Emission from RS CVn and Similar Binaries
Authors: Feldman P.A.
Published: July 2016

This is a summary of the systematic program of A3cm radio observations of RS CVn and similar binaries which has been carried out since 1977 at the Algonquin Radio Observatory. The observations were made at X-band frequencies (10-11 GHz) with the 46m telescope using the same observing procedures described in Feldman et al. (1978). The detection limit is generally 25 mJy, although it is possible to do somewhat better than this if the star is located well off the galactic plane and if it maintains an elevated flux level (i.e. ≳ 15 mJy) for several hours. The observing list has grown roughly four-fold since the start of the program in 1977. It now encompasses 65 of the 69 “bona fide” RS CVn binaries compiled by Hall (1982); the rest are suspected RS CVn binaries, BY Dra variables, Algol-type binaries, and W UMa binaries. To date, a total of some 85 observing days, representing more than 1000 hours of telescope time, has been devoted to this program.
Eruptive Phenomena as a Source of the Observed Variations of Intrinsic Polarization in Long Period and T Tau Variables
Authors: Sole M. , Strazzulla G.
Published: July 2016

The correlation between the rapid rise of intrinsic polarization, increasing U-B and enhanced equivalent width of Balmer, H and K emission lines is interpreted as a consequence of the activation of colour centres in circumstellar silicate dust by X/UV photons from flares. The temperature dependence of bleaching is discussed and the number of centres producing polarization changes is estimated.