bluuebunny/crossref_metadata_2025 huggingface dataset:
Relaxation of Mass-Gaining Stars
Authors: Chen K-Y. , Mullen E.F.
Published: July 2016

The study of relaxing low-mass stars, after gaining mass, to their corresponding main-sequence counterparts is presented. An initial mass of the star was 0.56 M⊙ which was gaining mass at a rate increasing gradually from about 10−10 to about 10−8 M⊙y−1 . The initial chemical composition used for computation was: 75% H, 22.3% He, and 2.7% heavy elements. The mass-gaining stellar model is assumed to be spherically symmetric and in hydrostatic and thermal equilibrium; also it is assumed that mass is absorbed through the stellar envelope from a uniformly distributed outer shell. A sequence of static models was calculated with time steps between the models chosen in such a way as to maintain the changes in physical variables with certain limits from one model to the next. This series of mass-gaining calculations was carried out to the model of 0.835 M⊙. Another series of calculations was carried out in order to investigate the effects of stopping the mass transfer and allowing the star to relax. Each of the twelve selected mass-gaining models was used as the starting point for one of these relaxation sequences; and for each of these twelve masses, a zero-age main sequence model was calculated. The relaxation models were calculated from the same evolutionary technique except that the mass-transfer rate was set to zero. The criterion for stopping these relaxation runs was that the gravitational luminosity term in the envelope should have returned to the main sequence value. An interesting result of these calculations is the finding that in this region of the main sequence where stars have radiative cores, mass-gaining stars develop convective cores. In this particular model sequence, the convective instability first became evident in the model of 0.7125 M⊙ with the logorithm of the central temperature of 7.047. The result of the relaxation calculations shows that, in each case, the star did relax to its corresponding main sequence position. In general, the relaxation process compares favorably with the thermal time scale for these stars. For the model of 0.745 M⊙ at the time when the luminosity increases, indicating that the effective source is reaching the surface, the convective core begins to disappear. The star then decreases its surface temperature, moving to the right in the H-R diagram, while the convective core disappears completely. The H-R diagram track then turns upward toward its proper main sequence location while the contral density and temperature and the luminosity due to nuclear energy generation decrease to their normal values. During this time, the radius and the total luminosity increase to their normal main sequence values.
U Cephei Revisited
Authors: Nelson Burt , Davis Walter D.
Published: July 2016

Observations of U Cephei made by C. M. Huffer, et al, in 1950-51 and in 1959, are presented here to contrast with other observations made by Huffer and others.

In many cases, to see a light-curve of an eclipsing binary is to see all light-curves for that particular system. This is certainly not true of U Cephei which, because of its rapid variations, has held the attention of so many for so long.

The 1950-51 yellow and blue observations were made at Washburn Observatory, Madison. The data have been transcribed from Huffer’s note books to a floppy disk and are available.
Dust Shell around V718 Scorpii
Authors: Parthasarathy M.
Published: July 2016

V718 Sco (HD 145718 = SAO 184232) is an eclipsing-binary system with an orbital period of about 200d, depth of primary minimum about lṃ4 and a primary component of spectral type A2 (Wood et al., 1980). Neither period nor eclipse depth are well determined and the system has not been observed photoelectrically. The IRAS point-source catalogue (Beichman et al., 1985) contains an object having a far-infrared excess at a position closely agreeing with that given for V718 Scorpii in the S.A.0. catalogue. The fluxes (in Janskys) at 12 µm, 25 µm, 60 µm and 100 µm are 5.73, 5.92, 4.91, 3.37 respectively and this distribution suggests that V718 Sco is surrounded by a dust envelope in which there is a temperature gradient. From the ratios of the fluxes, a dust temperature of about 140 K is found; the fluxes at 60 μm and 100 μm would suggest a lower temperature.
A New Model for Algol (β Persei)
Authors: Richards Mercedes T. , Bolton C. T. , Mochnacki S. W.
Published: July 2016

We studied the circumstellar gas in Algol (β Persei) by analysing Hαdifference profiles (observed profiles minus composite theoretical (LTE) photospheric absorption line profiles of the stars), at 98 phases in the binary’s orbit (cf. Richards 1986, Ph.D. thesis, University of Toronto). The data were obtained from Sept. 1976 to Dec. 1977; with an average phase interval of 0.02 over the entire orbit.

There was a smooth change in the profiles from strong, redshifted emission just outside primary eclipse, to an almost flat profile at mid-secondary eclipse, to strong, blueshifted emission just before primary eclipse began. Absorption was detected throughout primary eclipse, and there were smooth transitions between pure absorption and pure emission. The emission and absorption had FWHM’s of ~200 km s−1 and ~200 to 450 km s−1, respectively; with line strengths up to 10% and 19% of the continuum, respectively.
Dust Envelopes and IR Excesses in a Sample of RS CVn-Type Binaries
Authors: Scaltriti F. , Busso M. , Robberto M. , Origlia L. , Ferrari-Toniolo M. , Persi P. , Silvestro G.
Published: July 2016

In recent years, we have been studying the energy distribution of RS CVn binaries from UV to far IR wave lengths, in order to derive general properties of the systems and to better understand their evolutionary scenario, including the history of mass loss (Busso et al., 1987, 1988). In this framework, we have so far analyzed, at different level of accuracy, a total of about 60 sources, among which 30 have been the object of detailed studies, on the basis of broad band photomertic observations from 0.35 to 60 µm, using ground-based telescopes (mainly at La Silla, ESO) and IRAS-PSC information. For these 30 binaries, the quasi-periodic variations due to the presence of photospheric spots have been carefully subtracted, to derive the energy distributions of the unperturbed systems.
CCD spectroscopy of the W Serpentis binaries KX And and RX Cas
Authors: Schneider H. , Pavlovski K.
Published: July 2016

Initial results are presented from a study of Hγ profiles in the two interacting binaries KX And and RX Cas of W Serpentis type. The used CCD spectra with a resolution of 0.13Å/px were obtained with the 2.2m telescope and the Coudé spectrograph at the German-Spanish Astronomical Center at Calar Alto/Spain.
V367 Cyg as the interacting binary
Authors: Schneider H. , Pavlovski K. , Akan M.C.
Published: July 2016

The interacting binary V367 Cyg is contained in the original list of W Serpentis stars discovered by Plavec and Koch (1978) in their initial UV study and has been subject of numerous studies, both photometric and spectroscopic.
Symbiotic Stars
Authors: Allen David A.
Published: July 2016

I review our current knowledge of symbiotic stars. A great many papers have graced the literature in the fifty years of their study, and many data are available on the spectral variations at optical wavelengths these stars undergo. I do not give extensive references to those data, for previous reviews have done so quite adequately. Rather, I concentrate on the extensive widening of the wavebands within which symbiotic stars have been studied over the past few years, and attempt to synthesise the data into a coherent picture.

Symbiotic stars are most readily explained as interacting binaries, though single star models may still be tenable for some systems. They are made much more complex than most other interacting binaries by the variety of accreting stars, and because gas flows may be highly structured. Moreover, their study is more difficult than that of dwarf novae because the orbital periods are long compared to the activity cycles of the accretion phenomena.

Our data base has expanded enormously with our present spectral Catholicism. But there remains much valuable work to be done with even simple equipment on small telescopes. I suggest in a final section areas for future work.
Observations of Binaries and Evolutionary Implications
Authors: De Loore C.
Published: July 2016

Comparison of the characteristics of groups of stars in various evolutionary phases and the study of individual systems allow to make estimates of the parameters governing mass loss and mass transfer. Observations enable us in a few cases to determine geometric models for binaries during or after the mass transfer phase (disks, rings, common envelopes, symbiotics, interacting binaries, compact components).

From spectra taken at different phases, radial velocity curves can be derived and masses and radii can be determined. In special cases spectra in different spectral ranges (visual, UV, X-ray) are required for the determination of the radial velocities of the two components (for X-ray binaries, for systems with hot and cool components). Information on parameters related to the mass transfer process enables us to consider non conservative evolution - i.e. the computation of evolutionary sequences with the assumption that mass and angular momentum not only are transferred from one of the components towards the other one, but that also mass and angular momentum can leave the system. Careful and detailed analysis of the observations allows in certain cases to determine the parameters governing this mass and angular momentum loss, and for contact phases, to determine the degree of contact.
Mass Loss in Semi-Detached Binaries
Authors: Abhyankar K. D.
Published: July 2016

Pre-Main-Sequence contracting objects, post-Main-Sequence expanding stars and mass-losing components of semi-detached systems all occupy more or less the same region in the conventional H-R-diagram. We make a transformation to variables Δ (logL) and Δ (log Te), where Δ is the difference between the observed quantity, log L or log Te, and the value of that quantity which a star of the same mass would have on the empirical Main Sequence. It is demonstrated that a plot between the new variables clearly separates the mass-losing stars from other objects which is essentially an effect of the increasing abundance of helium relative to hydrogen.
Constraints for Cataclysmic Binary Evolution as Derived from Space Distributions
Authors: Duerbeck H. W.
Published: July 2016

Space densities and galactic z-distributions of novae, recurrent novae, dwarf novae and symbiotic stars are newly determined and discussed in the context of earlier determinations. The data are then compared with the distributions of single and binary stars of possibly related types (late type giants, Mira variables, Algol systems, W UMa systems).

Novae and dwarf novae have similar distributions, those of fairly young stellar populations. The observed space density of potential novae (novalike objects) indicates that the mean recurrence time of novae might be as small as a few hundred years, which leads, with given nova shell masses and mass transfer rates in the minimum stage, to a secular decrease of the masses of the components undergoing nova outbursts.

Recurrent novae and symbiotic stars have distributions of older stellar populations, similar to those of late type giants and Mira variables.

On the basis of galactic distribution, novae and dwarf novae are closely related and may be final stages of W UMa systems, as well as progenitors of supernovae of type I. A small fraction of W UMa systems seems to belong to an older population. If evolutionary transitions between these types of stars can be substantiated, the presence of a minority of novae and dwarf novae in globular clusters and of supernovae I in elliptical galaxies can be explained.

Due to the lack of sufficiently well determined space distributions of Algol binaries, the suggestion that long-period Algol systems might be the progenitors of cataclysmic binaries can as yet neither be substantiated nor refuted. A very high space density of long-period Algol systems in the solar neighbourhood is derived. The observed space density of cataclysmic binaries could be explained by the transformation of a small percentage of the long-period Algol systems by common envelope evolution.
The Work at the Minor Planet Center
Authors: Herget Paul
Published: July 2016

The Minor Planet Center at the Cincinnati Observatory is engaged in three kinds of activities: (1) the publication and distribution of the Minor Planet Circulars (MPC’s), (2) the collection and maintenance of a complete file of minor planet observations, and (3) the computation of orbital elements and ephemerides.
Physical Studies of Asteroids By Polarization of the Light
Authors: Dollfus Audouin
Published: July 2016

Curves of polarization are available at present for asteroids Vesta, Ceres, Pallas, Iris, Flora, and Icarus. These curves are compared with those of the satellites of Jupiter and Mercury, the Moon, and Mars. Laboratory simulations had already proved that the Moon's surface behaves like a powder of pulverized basalts; the recent confirmation by direct exploration is proving the significance of the method for remote determination of the surface properties of celestial bodies. The simulation of the Martian surface is found on small grained powders oxidized by ferreous limonite or goethite. New laboratory measurements were conducted to prepare the simulation of the asteroidal surfaces. Samples of the lunar surface returned to Earth provide impact-generated regolith and bare rocks superficially pitted and etched by impacts of the types suggested to be found on asteroidal surfaces; they were analyzed polarimetrically.

Preliminary interpretations show that Vesta departs significantly from the other asteroids and cannot be covered by frost deposits or by aggregate cosmic dusts; a regolith-type surface generated by impacts or a coating of cohesive grains is indicated.

Ceres, Pallas, and Iris are darker, and their polarizations do not suggest a pure regolithic surface, but cohesive grains or aggregates of dust are indicated.

Icarus is 108 times smaller in mass; its polarization authorizes a fluffy, loosely aggregated dust deposit; however, a cometary model with stones embedded in ice is perhaps not ruled out on the basis of the present data.

The way in which deep-space missions near the asteroidal belt can improve these results is discussed.
Laboratory Work on the Shapes of Asteroids
Authors: Dunlap J.L.
Published: July 2016

Photometric lightcurves of about 50 asteroids have been obtained over the past 20 yr, yet very little is known about the shape of these objects. Perhaps 100 lightcurves (including photographic ones) of 433 Eros have been obtained with amplitudes up to 1.5 mag. Some authors have attempted to calculate the dimensions of Eros assuming it to be a three-axis ellipsoid. The most recent determination (35 km, 16 km, 7 km) was given by Roach and Stoddard in 1938. In the case of 624 Hektor, amplitudes up to 1.1 mag were observed on lightcurves in which the primary and secondary maxima differed by less than 0.04 mag. Van Houten (1963) noted that for lightcurve amplitudes greater than 0.2 mag, the two maxima were about the same level and differed by 0.04 mag on the average.
Asteroidal Theories and Experiments
Authors: Arrhenius Gustaf , Alfvén Hannes
Published: July 2016

Theories on the origin and evolution of asteroids are confronted with three types of experimental tests. The first refers to the dynamic state of the asteroids and consists of orbital and in some cases spin data for bodies as small as about 1 km. (There are reasons to assume that the size spectrum extends to very small objects but nothing is known about them.)

The second type consists of observations of the chemical and structural properties of objects fallen to Earth from space. Here the relationship to asteroids is much more tenuous. Nevertheless, the study of meteorites has provided important insight into the chemical evolution of small bodies in space. As long as one realizes that such data refer only to bodies of special structure, composition, velocity, and other orbital characteristics, they can be useful also for conjectures about asteroids.
Accumulation of Chondrules on Asteroids
Authors: Whipple Fred L.
Published: July 2016

It is suggested that aerodynamic forces played a significant role in the selective accumulation of chondrules on asteroids moving with respect to the gas in a primeval solar nebula. Particles smaller than millimeter chondrules would sweep by an asteroid moving in a critical velocity range, whereas larger particles could be accumulated by impact. Theory and calculation cover the case of subsonic velocity and asteroidal diameter up to 50 km for a nebula density up to 10-6 g/cm3, or higher for smaller asteroids.
Spatial Distribution of Interplanetary Dust
Authors: Roosen Robert G.
Published: July 2016

Interplanetary dust can be defined as solid particles outside Earth's atmosphere in the size range larger than a molecule and smaller than an asteroid. It is studied by a number of quite different techniques. For Earth-based observers, these techniques include measurement of the brightness and polarization of the interplanetary light, optical radar studies of particles entering the upper atmosphere, photographic and radar meteor observations, study of meteorites, and various methods of collecting dust particles in the atmosphere, in ice cores, and in deep sea sediments. Observations made from spacecraft include some interplanetary light observations and measurements of individual particles by means of microphones, penetration sensors, and collection experiments. These observational techniques are described by Millman (1969) and Bandermann (1969).
A Core-Mantle Model for Cometary Nuclei and Asteroids of Possible Cometary Origin
Authors: Sekanina Zdenek
Published: July 2016

Arguments for a long time have been brought forward in support of the idea that the minor planets with orbits approaching Earth's orbit might be of cometary origin. Our feeling is that before such hypotheses are considered for any particular object, it is necessary to prove that differences in physical appearance and dynamical behavior between a typical asteroid of the Apollo or Albert types and a typical short-period comet can be interpreted in terms of cometary evolution.

In this paper, we discuss models of cometary nuclei, transition of an object from cometary phase into asteroidal phase, and specific asteroidal objects that may be of cometary origin.
Interrelations of Meteorites, Asteroids, and Comets
Authors: Anders Edward
Published: July 2016

Most meteorites come from a small number of parent bodies (6 to 11), with radii mainly between 100 and 300 km. The most likely sources of meteorites are seven asteroid families between 1.9 and 2.8AU, whose eccentricities and inclinations are high enough to permit their collisional debris to cross the orbit of Mars. Comets are too small and too numerous to serve as a source of the major meteorite classes, but they may well be an important source of micrometeorites and carbonaceous chondrites.
Arguments for a Mission to an Asteroid
Authors: Alfvén H. , Arrhenius G.
Published: July 2016

With respect to their orbital parameters, the known asteroids fall into different groups:

(1) Main belt asteroids orbit between Mars and Jupiter. Most of them have semimajor axes a in the range 2.0 < a > 3.5 AU.

(2) Asteroids outside the main belt form a number of different groups,
such as the Trojans, Hildas, etc.

(3) Mars-crossing asteroids are bodies with low a values and perihelia inside the Martian orbit; in several cases they are inside Earth’s orbit. They are the closest neighbors in space of the Earth-Moon system. A list of them is given by Marsden, table II. We select from these the ones with eccentricities in the range 0.2 to 0.4; they will be referred to as the Eros group, named after its largest member. The arguments for a mission to an asteroid refer especially to the Eros group as a first target.
Description of Pioneer F and G Asteroid Belt Penetration Experiment
Authors: Kinard William H. , O’Neal Robert L.
Published: July 2016

A NASA Langley Research Center meteoroid detection experiment will be performed on both the Pioneer F and G missions. The objective of this experiment is to obtain data that will indicate the population of meteoroids in the 10-9 to 10-8 g mass range in interplanetary space and, in particular, the region of the asteroid belt, and establish a first indication of the meteoroid penetration hazard to spacecraft in the asteroid belt. Specifically, the experiment will detect meteoroid penetrations of stainless steel targets 25 and 50 µm (1 and 2 mils) thick as the Pioneer spacecraft travel in interplanetary space through the asteroid belt to Jupiter and beyond.
Observations of the Profiles of Solar UV Emission Lines and their Analysis in Terms of the Heating and Production of the Corona
Authors: Boland B. C. , Engstrom S. F. T. , Jones B. B. , McWhirter R. W. P. , Thonemann P. C. , Wilson R.
Published: July 2016

Observations of the solar spectrum have been made between 1200–2200 Å with high spectral resolution. The results were obtained with an all-reflecting echelle spectrograph carried by a stabilized Skylark rocket launched in April 1970. Measurements of the profiles of a number of emission lines due to SiII, CII, SiIII and CIV formed in the temperature range 104–105 K, indicate ion energies which are considerably in excess of the electron temperatures derived from the ionization balance. Since the ion/electron relaxation time is very short the observed ion energies cannot correspond to an ion temperature and hence a non-thermal mechanical energy component exists in the transition zone.
Calculations on the Solar Spectrum from 1 to 60 Å
Authors: Mewe R.
Published: July 2016

Over two hundred spectral line intensities between 1 and 60 Å from ions in the solar corona have been computed for electron temperatures ranging between 105 and 109 K (Mewe, 1972a). Also the continuum (ff+fb) radiation intensity has been computed. The calculations were set up to interprete soft X-ray measurements aboard the ESRO 2B satellite (IRIS): Wavelength bands 44–55 Å (experiment of Space Research Laboratory, Utrecht) and 1–3, 3–9, 6–18 Å(expt. of University College, London) (Brinkman and Shaw, 1972).
Recent Spectroscopy of X-Ray Sources and Systems Related to Cataclysmic Variables: I
Authors: Cowley A.P. , Crampton D. , Hutchings J.B.
Published: July 2016

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

We report the first results of an observational campaign consisting of coordinated photoelectric photometry of Ex Hya from four observatories at different geographical longitudes for a total of 146 hours in April 1979.

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

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

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

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

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

Deep light minima of R CrB type stars are considered to occur due to the carbon abundance excess in the atmospheres of these stars, and condensation of carbon into graphite dust leads to light decrease (Zhilyaev et al., 1978). The cause and conditions of dust formation are not clear. Therefore, it is necessary to find out regularities in the occuring of light minima and to search for correlations between different parameters of this type stars. This paper deals with the time intervals between the series of consecutive light minima.

A long series of observations of the R Coronae Borealis variables brightness allowed to study repeatedly their light curves in order to obtain their periodicity or other parameters in occuring of deep light minima. The work by Sterne (1935) was the first, in which the conclusion was made that R CrB is an irregular variable. Next investigations contained the analyses of light curves and calculations of the number of minima planned in the definite intervals, f.ex., 0-300, 300-600 days etc. (Howarth, 1977; 1978). Other papers (Tempesti et al., 1975) considered the duration of minima and maxima states. In all these investigations the time was counted off from the moment when a star reached a definite light decrease magnitude, f.ex., Δ m = 1m. The conclusions obtained were similar: the considered parameters were in agreement with Poisson statistics.
Photometric and Radial Velocity Variations of R CrB Near Maximum Light
Authors: Raveendran A.V. , Ashoka B.N. , Kameswara Rao N.
Published: July 2016

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

In this short note, an attempt has been made to estimate mass and luminosity of the unique object, V348 Sgr, which appears to be a “Rosetta Stone” for our understanding of late stages of stellar evolution, as

i)

its photosphere is virtually hydrogen-free and carbon-rich as with an extreme helium star,

ii)

it fades irregularly as does a R CrB-star and

iii)

it is surrounded by a nebular shell similar to that surrounding Planetary Nebulae.

We know a great deal more about the above-mentioned objects than about V348 Sgr and this knowledge can be used to obtain estimates on mass and luminosity of the latter.
Practical Problems in the Analysis of CP Stars
Authors: Cowley Charles R. , Johansson Sveneric
Published: July 2016

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

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

The cool Ap star HD 60435 was monitored in a programme of rapid B photometry during 18 nights in January/February 1984, from two stations widely spaced in longitude (the University of Toronto 0.6-m telescope at the Carnegie Southern Observatory (CARSO) on Las Campanas, Chile, and the 0.5-m telescope of the South African Astronomical Observatory ( SAAO)). On six of those nights, contiguous light curves from both sites were obtained.

Fourier analysis of these data confirms the rapid variability first reported by Kurtz (1984) and reveals several additional transient oscillations. HD 60435 exhibits persistent - but modulated - oscillations at a frequency near 1.4 IRHZ (period = 11.9 minutes), and short-lived oscillations at frequencies near 1.1 and 4.2 mHz (periods of 15.2 and 4.0 minutes, respectively). These latter two periods represent the longest and shortest yet observed in the class of rapidly oscillating Ap stars.

We have applied the oblique pulsator model (Kurtz 1982) to the fine-scale splittings detected in the frequency spectra of the 1.4 and 1.1 mHz oscillations. Also, the series of frequencies close to 1.4 mHz which fall into a pattern of roughly equal spacing is compared to such spacings predicted for overtones in pulsating main-sequence A stars (Shibahashi and Saio 1984). Both approaches suggest that HD 60435 is undergoing non-radial pulsations of odd and even degree (probably with ℓ ≲ 3).

The oblique pulsator interpretation of the splittings in the frequency spectrum and the amplitude modulation of the 1.4 mHz oscillations also predict: a rotation period of approximately eight days for this star. Mean photometry of HD 60435, collected by the authors, supports a similar value of 7.7 days for the period.

Analysis of the oscillations is hampered by ambiguities due to daily aliases present in the data, and by the complicated structure and time-dependence of the frequency spectrum. Further observations of HD 60435 are essential if we are to fully understand its rapid variations.
Investigations of the Magnetic Star 53 Cam Variations Using the Spectra of High Time Resolution
Authors: Polosukhina N.S. , Malanushenko V.P. , Tuominen I. , Karttunen H. , Virtanen H.
Published: July 2016

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

The literature concerning spectroscopic studies, abundances, photometry, and systematics of intermediate-temperature (9500 K < Teff < 16000 K) normal, Hg-Mn, and related stars is reviewed. The review is restricted mainly to papers published since the last international meeting on chemically peculiar stars at Liège in June 1981, and is intended to be complete to 31 December 1984.
Criteria for Identifying an Astronomer as an Amateur
Authors: Williams Thomas R.
Published: July 2016

While significant contributions of amateur astronomers are generally recognized in the literature, the identification of the individual as an amateur is frequently unclear. As a result, amateur astronomers today have a limited sense of the contributions of earlier amateur astronomers. In part, this problem stems from current usage of the word “amateurish” as a pejorative, representing something not well-done or lacking in quality. In addition, many individuals, who take pride in identifying themselves as amateur astronomers are neither inclined, nor in fact capable, of making a contribution to astronomy. It is important, however, for historians and others who write about the history of astronomy to recognize amateur astronomers and identify the significance of their contributions. For it is through such elaboration that other amateurs will recognize the possibilities and great value that may be associated with their own efforts. Therefore it is necessary to develop a common understanding of the characteristics that distinguish an amateur astronomer from what I identify in this paper as a “recreational sky observer”. Such a classification scheme should help future writers to correctly identify amateur astronomers and their contributions.
The Amateur and Eclipsing Binary Stars
Authors: Wood Frank Bradshaw
Published: July 2016

Probably no other branch of science has benefited as much from the work of dedicated amateurs as has the science of Astronomy. While some amateurs have made many useful types of astronomical observations– comets, meteors, occultations, etc. – perhaps none has been as extensive and as useful as those made in the field of variable stars. There are not nearly enough professional astronomers to keep under proper observation the increasingly large number of known variables. While all kinds of them are well worth continuous study, this paper will call attention to the importance of eclipsing variables and in particular the systematic and continuing observation of their times of minimum light.
Amateur Astronomy in France, 1789–1830: Two Examples
Authors: Dumont Simone , Grillet Solange
Published: July 2016

Historical events affected astronomy in France at this period. Large instruments were also rare so amateurs were on equal terms with professionals. Two significant amateurs are described:

Honoré Flaugerges (1755–1830), justice of the peace at Viviers (Ardèche), observed from 1782 until his death, in particular discovering two comets and recording sunspots.

Anne-Jean P.C. Duc-Lachappelle (1765–1814), studied astronomy in Paris, and set up an observatory in Montauban in 1789, mainly observing planets and Mercury in particular. He had one pupil, Bernier, and set up a local society for arts and sciences in 1796.

Both of these astronomers had numerous contacts with professional astronomers throughout Europe.
Comet Halley in 1910 in Franche-Comté: or Collective Memory at Fault
Authors: Heurtel A. , Rougeot M. , Parisot J.P.
Published: July 2016

When old people are questioned they often say that they vividly recall the appearance of Comet Halley in 1910. When, in 1985, we started to analyze that previous apparition, we fully expected to find remarkable accounts in the newspapers. But instead of dramatic stories of its appearance on the night of 1910 May 18–19, we find nothing was observed until May 28, because the sky over a large part of France (even Paris), was cloudy. Even then, it was described in terms such as “This wretched comet has a very over-inflated reputation, it appears more like a nebula than the object that we were led to expect.” So why then the popular excitment?
Amateur Astronomers and the IAU Central Bureau for Astronomical Telegrams and Minor Planet Center
Authors: Marsden Brian G.
Published: July 2016

Of all the sections of the International Astronomical Union the Central Bureau for Astronomical Telegrams is undoubtedly the one that most concerns amateur astronomers. Just about anybody in the world with at least some familiarity with the sky has the potential to discover (or to think he or she has discovered) a comet or nova. If the object is real and sufficiently bright, it is very probably already known. Somebody has to be the first discoverer of every comet or nova, however, and soon after the IAU was established in 1919 it set up the Central Bureau to receive and to disseminate to the astronomical community news of such discoveries. Discoveries of supernovae in other galaxies, natural satellites of the planets, erupting x-ray sources and transient features on the planets are also dealt with by the Central Bureau, which since 1965 has operated at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts. The Central Bureau handles unusual minor planets in the vicinity of the earth, although the thousand or more ordinary minor planets routinely discovered each year (and with which amateurs are being increasingly involved) are more appropriately the province of the Minor Planet Center, set up by the IAU in 1947 and since 1978 also operated at the Smithsonian Astrophysical Observatory. About one-quarter of the subscribers to the various services of the Central Bureau and/or the Minor Planet Center are individual amateur astronomers or organizations of amateurs.
An Improved Method of Photographic Measures of Double Stars
Authors: Rodriguez D. , Bernedo J.A. , Valls-Gabaud D.
Published: July 2016

We present a new technique in double star photography leading to high accuracy measurements in amateur-size instruments. The trailing method has been improved by the use of a chopper that cuts the trail into a number of segments. The chopper period is accurately known, so it is the length of each segment on the plate. In this way the scale factor is measured in each exposure. Fine-grain films, such as hyper-sensitized Kodak 2415, are used and all measurements are performed at the microscope. The same technique may also be applied to CCD cameras. A statistical analysis of errors shows that Δθ ≤ 30′ and Δρ/ρ ≈ 0.01 for most binaries with ρ ≥ 3″. This method has been applied to professional-amateur joint programs dealing with multiple systems with variable components and a survey of poorly-observed wide binaries.
Studying “Luna Incognita”: The Region Near the South Pole
Authors: Legrand Michel
Published: July 2016

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

In 1985–86 when spaceprobes flew past P/Giacobini-Zinner and P/Halley, many amateurs observed these comets and submitted their results to national or international (IHW) organisations. Their visual, photographic, photometric and spectroscopic observations made a contribution to scientific knowledge. It is pertinent to ask if space programmes under consideration will allow similar cooperation to be continued.

The least uncertain project is that of another cometary fly-past by GIOTTO. Following orbital corrections made between 1986 March 19 and April 2, (ΔV =115 ms−1), the European probe should pass 22 300 km from the Earth on 1990 July 2. The gravitational assist from our planet should then put it onto an orbit to pass P/Hartley 2, P/du Toit-Hartley or P/Grigg-Skjellerup (1992 July 10). This last comet appears to be the most desirable target; although the final decision will not be taken until autumn 1989, recommendations have been made (Morley, 1986) for an international astrometric campaign.
Amateur Astronomers and the Recovery of Periodic Comets
Authors: Martinez Patrick
Published: July 2016

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

Mutual events (occultations or eclipses) of Jupiter’s satellites occur every 6 years. The 1985 series was particularly favourable as it occurred when Jupiter was at opposition. An observing campaign (PHEMU85) was therefore organized by the Bureau des Longitudes, and sponsored by the CNRS under RCP (Coordinated Research Programme) 754.

The interest in observing the events lies in the precise positional information that may be obtained. Conventional (photographic) astrometry gives results to within 400 km, but mutual events give an accuracy of at least 100 km. Observation of mutual events is easy in that the Galilean satellites are bright, so large telescopes do not have to be used, and photoelectric observations in particular can be obtained from urban sites or under poor meteorological conditions. The professional workers generally employed photoelectric photometers or vidicon-type detectors, while amateurs used visual, photographic, photometric and video techniques. Two groups of amateurs were particularly involved, GEOS (European) and GEA (Spain), but individual amateurs also contributed.
Methods of Popularizing Astronomy in Various Countries
Authors: Iwaniszewska Cecylia
Published: July 2016

Some interesting methods of popularizing astronomy in various countries were reviewed, and may be divided into two types: active and passive methods. Active methods include:

1.

Astronomy in the countryside. Astronomical camps for both children and grownups, who normally live in towns, to learn basic astronomical facts. (Italy)

2.

Astro-puppets. Visitors to an observatory are greeted by puppets (Copernicus, Galileo, etc.) who not only give talks, but also converse with the audience. (Argentina)

3.

Hand-operated devices. A simple orrery showing the movement of the Earth, and other devices that viewers operate for themselves. (India)

4.

Graphical calendars. Several popular observatories collaborate to produce a yearly calendar showing planetary rising and setting times, etc. (Czechoslovakia)

5.

Amateur clubs. High-school and university students became so interested in astronomy that they formed their own group and now produce a magazine and carry out observing, etc. in a country where there is no professional astronomical institution. (Paraguay)

6.

An interdisciplinary approach. Various meetings and workshops are arranged to bring together astronomy, physics, biology, geology, etc., leading to a better understanding of modern science. (Japan)

7.

Astronomical competitions. Everything from children’s drawings to special tests and papers, sometimes connected with special events. Also awards for the best work of popularization in a given year. (Worldwide)

Passive methods are far more traditional, and include planetarium shows, including special ones for pilgrims (India); special exhibitions; radio and television programmes; public lectures; popular magazines usually edited for special groups of readers. Finally, what about humorous astronomical stories or pictures, is that active or passive?
The Planetarium as a Medium for Teaching Astronomy
Authors: Barve Kunda
Published: July 2016

Being sited in a large city (with about 10 million inhabitants), the planetarium at Bombay has to try to meet the requirements of a very wide range of visitors, some 3.3 million of whom have seen presentations. These visitors come from very different linguistic, cultural, religious, economic and educational backgrounds, which pose many problems in arranging suitable programmes. (There are 16 major languages and many less common ones.) School children make up the bulk of visitors and presentations for them are linked to their academic grade. Amateur astronomical organisations are gradually coming into existence in India, and the planetarium provides help and encouragement to them. Special shows are made for many individual groups of people, ranging from lovers of poetry and fine arts to invalids and the handicapped. A wide range of additional activities such as competitions, field trips and exhibitions is also provided.
Chemical Peculiarities, Mass Loss, and Final Evolution of AGB Stars in the Magellanic Clouds
Authors: Wood P.R.
Published: July 2016

The Magellanic Clouds are sufficiently close that evolved stars which exhibit chemical peculiarities and the effects of mass loss can be readily observed. Such objects include carbon stars, S stars, long-period variables, OH/IR stars and planetary nebulae. Because of the relatively well-known distances of the Magellanic Clouds, the intrinsic luminosities of these objects can be accurately determined, in contrast to the situation in the Galaxy where the great majority of asymptotic giant branch (AGB) stars occur in the field population. In this review, observations of AGB stars in the Magellanic Clouds will be discussed with particular reference to those features which can shed light on mass loss and chemical peculiarities resulting from stellar evolution.
Wolf-Rayet stars as a diagnostic of internal mixing processes in massive mass losing stars
Authors: Langer N.
Published: July 2016

Massive stars (MZAMS ≳ 30 M⊙) develop during their observable hydrostatic evolutionary phases — i.e. central H- and He-burning — three different large scale convective zones, which are: 1) The H-burning convective core, 2) the intermediate convective shell (ICZ) above the hydrogen shell source, which forms at time of hydrogen exhaustion, and 3) the He-burning convective core. The spatial extent of these convective regions, wherein the chemical structure is rapidly homogenised, can be predicted from theory only with a large uncertainty. Different assumptions on the efficiency of these mixing processes in stellar evolution calculations lead to quite different evolutionary pictures for massive stars, especially regarding their Wolf-Rayet (WR) phases. On the other side, many observational data concerning WR stars became available in recent years. For this reason, we attempt to perform a comparison of theoretical evolutionary sequences with observed properties of WR stars in order to derive restrictions on the efficiency of the three mixing processes mentioned above.