bluuebunny/crossref_metadata_2025 huggingface dataset:
Photospheric molecular line profiles in cool stars
Authors: Ridgway S.T. , Friel E.D.
Published: July 2016

Spectral lines of the ΔV=2 rotation vibration bands of CO are well suited for study of photospheric motions and the mass ejection process in cool stars. We have obtained high spectral resolution (1.8 km/sec) and high signal-to-noise (>102) line profiles for a selection of K and M giants. These profiles are being studied for evidence of gas motions in the photosphere and near circumstellar regions.
Line formation in the wind of Alpha Cygni
Authors: Kunasz P.B. , Praderie F.
Published: July 2016

We summarize the results of recent IUE observations of the spectra of α Cygni and discuss possible explanations for the Doppler-shifted pure absorption profiles in the resonance lines of the singly ionized metals. The results of detailed modeling for MgII λ 2795, 2802 are presented, and discussed in the context of observations of α Cyg in the radio, infrared, visible, ultraviolet and X-ray parts of the spectrum.
Radiative wind acceleration in early type stars
Authors: Panagia N. , Macchetto F.
Published: July 2016

The processes of radiative acceleration of stellar winds in OB stars by single and multiple photon scattering are considered. Single scattering can be the dominant accelerating process for stars later than B2 (Teff < 2 x 104 K) and can account for terminal velocities up to 500 – 1000 km s-1 . Multiple scattering of photons in the approximate range 200 – 500 A provides additional wind acceleration for stars earlier than B2 to reach terminal velocities of up to 2000 – 4000 km s-1 A systematic increase of the terminal velocity as a function of the effective temperature is predicted. Observational data confirm this expectation quite well.
The fluctuation theory of the stellar mass loss
Authors: Andriesse C.D.
Published: July 2016

That we cannot give a justification – or sufficient reasons – for our guesses does not mean that we may not have guessed the truth.

K.R. Popper

If studied in detail, the mass flows from the stars appear to be variable. “Mere inspection of solar wind data reveals large variations on a time scale of several days” (Hundhausen, 1972). Also, “it is obvious that mass loss from hot stars is not a stationary phenomenon but that variations on short timescale occur” (de Jager et. al., 1979). And a cool supergiant has “a photosphere fluctuating in both brightness and radial velocity, (and) an expanding chromosphere … uncoupled from motions in the photosphere” (Goldberg, 1979).
Mass loss and evolution of massive stars
Authors: Chiosi C.
Published: July 2016

In the past few years both growing observational evidence and theoretical understanding have shown that mass loss by stellar wind is a common occurrence in the evolutionary history of many types of star. Recent reviews on the subject may be found in Conti (1978), Cassinelli (1979), Conti and Mc Cray (1980), Hutchings (1980a), de Loore (1979, 1980) and Sreenivasan (1979).

Therefore, in this paper we will concentrate only on those observational and theoretical aspects of the problem that demand further investigation.
Effects of a stochastic initial mass function on the upper main sequence band
Authors: Chiosi C. , Greggio L.
Published: July 2016

The theoretical (Mb versus Log Te) HR diagram for the brightest galactic OB stars shows an upper boundary for the luminosity, which is characterized by a decreasing luminosity with decreasing effective temperature (Humphreys and Davidson, 1979). The existence of this limit was interpreted by Chiosi et al. (1978) as due to the effect of mass loss by stellar wind on the evolution of most massive stars in core H-burning phase. In fact, evolutionary models calculated at constant mass cover a wider and wider range in effective temperature as the initial mass increases during the main sequence phase. On the contrary, sufficiently high mass-loss rates make the evolutionary sequences of most massive stars (M 60⩾Mʘ) shrink toward the zero age main sequence whenever, due to mass loss, CNO processed material is brought to the surface (Chiosi et al., 1978; de Loore et al., 1978; Maeder, 1980).
A determination of the characteristics of Cepheids from B-type companions
Authors: McNamara D.H. , Feltz Kent A.
Published: July 2016

Photometry (uvbyβ) of five cepheids with B-type companions has been utilized to derive the spectral types and apparent magnitudes of the companions. By utilizing the period-luminosity relation it is possible to estimate the absolute magnitudes of the companions since the differences in magnitude between the companions and cepheids are known. The spectral types and absolute magnitudes of the B-type components indicate they are all evolved from the zero-age main sequence. By utilizing the ages of the B stars we can derive the ages of the cepheids under the assumptions that both stars of a binary were formed at the same time and the cepheids are more evolved than their B components. A period-age relation of the form log tage = 8.60 - 0.83 log P is found. Minimum masses of the cepheids can also be estimated from the data. No evidence of large mass loss is evident in the intermediate-band photometry of cepheids.
Mass transfer and stellar wind effects in the eclipsing binary RT Andromedae
Authors: Bakos G.A. , Tremko J.
Published: July 2016

In recent years the short period eclipsing binary RT And has been studied extensively by a number of authors. From photo electric observations the light curve and the photometric elements were derived by Dean (1974) and Mancuso et al. (1979). The geometric dimensions of the binary confirm that the system is detached consisting of two stars of spectral type F8 V and KO V. The mass ratio is 0.66. In spite of this classification, effects appearing among semidetached systems have been observed, namely, variations of the amplitude and the shape of the light curve and changes of the length of the orbital period.
Interacting stellar winds in a binary system
Authors: Kwok Sun
Published: July 2016

It is now known that strong stellar winds develop in stars mostly at the red and blue sides of the HR diagram. However, although the mass loss rates observed in O and M stars are comparable, the corresponding wind velocities are vastly different. It would thus be of great interest to find a binary system, containing both a cool and a hot star each with its own wind, and observe the resultant interaction. For a long time, α Sco (M1.5 Iab + B2.5 V) was the only known example (Kudritzki and Reimers 1978, van der Hucht et al. 1980). The situation in this case is best illustrated by a VLA map made by Gibson (1979) who finds that a shock develops at the surface of interaction of the two winds. In this paper I shall describe another binary system in which two stellar winds are interacting with dramatic effects.
Is this diagramme an argument for binary orbital evolution due to mass-loss?
Authors: Dommanget J.
Published: July 2016

In 1963, a diagramme has been established by the author, for visual and spectroscopic binaries, showing the existence of a real correlation between total mass and eccentricity.

The consideration of an up-dated material leads to-day to an identical diagramme confirming the reality and the stability of the mentioned correlation.

This diagramme is discussed with the assumption of a substantial secular mass-loss of the components of the considered binaries.
Nova AQL 1918: a nude old nova
Authors: Selvelli P.L. , Cassatella A.
Published: July 2016

IUE observations at high and low resolution of Nova Aql 1918 show neither evidence of outflow nor the presence of nebular lines. This indicates that the shell ejected at the time of the outburst and surrounding the system for many years (Mustel and Boyarchuck, 1970) has by now disappeared.

The high excitation spectrum presents rapid variations in the far UV and eclipse effects in the near UV that seem well correlated with the orbital phase.

The observations can be interpreted in terms of phenomena occurring in or near the accretion disk surrounding the white dwarf. However, the small inclination of the orbital axis raises serious problems in trying to model the system.
Full-Disk Observations of Solar Oscillations from the Geographic South Pole: Latest Results
Authors: Grec Gérard , Fossat Eric , Pomerantz Martin A.
Published: July 2016

This paper presents the latest results obtained from the analysis of the full-disk Doppler shift observations obtained at the geographic South Pole in 1981. About 80 normal modes of oscillation (l = 0–3) have now been identified. Their frequencies range from 1886 μHz (l = 1, n = 12) to 5074.5 μHz (l = 2, n = 35), and their amplitudes are as low as 2.5 cm s–1. Amplitude modulation occurs with periods of 1–2 days, and the individual oscillations appear to be excited randomly and independently. In cases where other groups have observed some of the modes identified by us, the agreement in frequency is good.
Spectral-Spatial Analysis of Wave Motions in the Region of Temperature Minimum of the Sun’s Atmosphere
Authors: Merkulenko V.E. , Polyakov V.I. , Palamarchuk L.E. , Larionov N.V.
Published: July 2016

A spectral-spatial analysis is made in the region of temperature minimum of the Sun's atmosphere. Filtergrams in the Ba II 4554 + 0.05 Å line have been used. The wavelengths corresponding to the sequence of peaks on the spectrum are in close agreement with those theoretically calculated by Ulrich and Rhodes (1977) for five-minute oscillations. We thus have good cause to surmize that the observed oscillations in the region of temperature minimum pertain to the p-mode class of general oscillations of the Sun, the main fraction of their energy falling on the period of 300 s.
Is There an Oblique Magnetic Rotator Inside the Sun?
Authors: Isaak G.R.
Published: July 2016

The size of the rotational splitting recently observed (Claverie et al., 1981) is correlated with the 12.2d variation in the measurements of solar oblateness observed by Dicke (1976) and implies a convection zone of depth of 0.1 Rʘ. The near equality of amplitudes of global velocity oscillations (Claverie et al, 1981) of the various m components of the l = 1 and l = 2 modes as seen from the Earth viewing the Sun nearly along the equator is unexpected for pure rotational splitting. It is suggested that a magnetic perturbation is present and an oblique asymmetric magnetic rotator with magnetic fields of a few million gauss is responsible. A more detailed account was submitted to Nature.
Derivation of the Amplitude Equations of Acoustic Modes of an Unstable Semi-Infinite Polytrope
Authors: Poyet Jean-Pierre
Published: July 2016

The coupling of non-radial pulsations and convection is studied on a simple example: an unstable semi-infinite polytrope. An expansion is proposed and the equations that should describe correctly the pulsations are isolated. The additional complications of the real solar case are discussed at the end.
Adiabatic Oscillations of a Differentially-Rotating Star. Second-Order Perturbation Theory
Authors: Vorontsov S. V.
Published: July 2016

Perturbation theory is developed for calculating the influence of slow differential rotation on the adiabatic nonradial modes of stellar oscillations. The effects of Coriolis forces and ellipticity are analysed simultaneously using the perturbation technique for Hermitian operators which is developed up to second order in eigenvalues and to first order in eigenvectors.
Stellar 5 min Oscillations
Authors: Christensen-Dalsgaard Jørgen , Frandsen Søren
Published: July 2016

Estimates are given for the amplitudes of stochastically excited oscillations in Main Sequence stars and cool giants; these were obtained using the equipartition between convective and pulsational energy which was originally proposed by Goldreich and Keeley. The amplitudes of both velocity and luminosity perturbation generally increase with increasing mass along the Main Sequence as long as convection transports a major fraction of the total flux, and the amplitudes also increase with the age of the model. The 1.5 Mʘ ZAMS model, of spectral type F0, has velocity amplitudes ten times larger than those found in the Sun. For very luminous red supergiants luminosity amplitudes of up to about 0ṃ.1 are predicted, in rough agreement with observations presented by Maeder.
Helioseismology in the Future
Authors: Bonnet R.M.
Published: July 2016

We review the observables of helioseismology that can contribute to our knowledge of the physical conditions in the solar interior. We discuss the limitations which presently prevent helioseismology from reaching its ultimate goal. We finally present a list of projects which either are already underway or that are planned for the near future, and we conclude by showing the crucial role that space observations may play in the future.
The Distribution of Chromospheric Emission Strengths Among Red Dwarfs
Authors: Soderblom David R.
Published: July 2016

The survey of Vaughan and Preston (1980, hereafter VP) of Ca II emission among solar neighborhood stars has shown the distribution of chromospheric emission (CE) of these stars. For stars bluer than (B-V)= 1.50, it is possible to transform VP's equivalent width S into a relative flux by use of Middelkoop's (1982) formulae. This enables construction of a chromospheric color-magnitude diagram (illustrated in Soderblom 1982), which shows the same general features as VP's log S vs. (B-V) plot, except that the CE (as a fraction of the stellar luminosity) declines with mass due to the decline of the ZAMS rotational velocity with mass (Soderblom 1983).
X-Ray Emission from Flare Stars
Authors: Agrawal P.C. , Rao A.R. , Sreekantan B.V.
Published: July 2016

Flare stars are a group of mostly dMe stars, which show intense flaring activity in the optical as well as in the radio and X-ray bands. These stars are characterized by the presence of chromospheric emission lines like % and Call H and K which are present even during the quiescent state. The presence of transition regions and coronae have been inferred from the detection of UV emission lines like NV, CIV, SiIV etc. with IUE and X-ray observations made with the Einstein Observatory. We report here X-ray observations of flare stars made with Einstein to measure their coronal X-ray emission during the quiescent state.
Variable K-TYPE Stars in the Pleiades
Authors: van Leeuwen Floor , Alphenaar Peter
Published: July 2016

Photometric observations in the VBLUW system (Lub, 1979) have been performed during 1980 and 1981 of 19 late G and early Ktype members of the Pleiades Cluster, in order to study their variability. All stars showed variations with amplitudes of 0.02 to 0.20 magn. in V. For 12 stars lightcurves were obtained which show periods that range from 0.24 to 1.22 days. The light curves are semi-regular and resemble those of BY Dra stars, although the periods are shorter.
An Unusual Flare on EV LAC
Authors: Andersen Bo Nyborg
Published: July 2016

It has long been noted that the characteristics of the intensity variations during a flare on UV Ceti stars depend on the observed spectral region. The intensity Increase being larger in the shorter wavelength region. Typical values for the ratioes between the relative intensity increases on EV Lac in the Johnson UBV-bands are òU/òB≈6 and òB/òV≈3. (Moffet 1974).
Results From Optical and UV Stellar Flare Spectroscopy
Authors: Giampapa Mark S.
Published: July 2016

Optical and ultraviolet spectroscopy can enable the assessment of the physical conditions characterizing a stellar flare atmosphere and thereby potentially elucidate the possible radiative and hydrodynamic transport mechanisms operative during stellar flares. In this review, I present illustrative examples of the spectroscopic diagnostic techniques that can be applied to the analysis of stellar flare spectroscopic data and the resulting inferences concerning stellar flare properties for M dwarf flare events.
IUE Spectra of The by Dra/Flare Star AU Mic
Authors: Butler C.J. , Andrews A.D. , Doyle J.G. , Byrne P.B. , Linsky J.L. , Simon T. , Marstad N. , Rodonò M. , Pazzani V.
Published: July 2016

A coordinated series of ground-based optical and IUE observations of BY Dra variables was undertaken to follow the spectral variation of these stars over one cycle. In the first series 20 LWR and 19 SWP trailed spectra were taken of AU Mic over a three day period 4-6 August 1980 .

In Figure 1 we show the mean integrated fluxes for the strong emission lines in the SWP spectra of AU Mic over the observed phase interval of 0.14 to 0.8 together with an approximate V light curve determined by the FES on IUE. From comparison of the emission line intensities and FES magnitudes in Figure 1 several points emerge.
Flare-Like Activity of Red Giant Stars
Authors: Stencel Robert E.
Published: July 2016

Evidence for magnetic surface activity among cool stars of low gravity is discussed.
Flares on the Sun: Selected Results from SMM
Authors: Simnett G.M.
Published: July 2016

Observationally the study of solar flares has reached the stage where intensity-time distributions of emission over broad and resolved regions of the electromagnetic spectrum are obtained for spatially resolved parts of the flare. Polarization measurements add an important diagnostic tool in some wavebands but we shall not report on these here. In the optical band good ground based observations have been available for many years, whereas in the UV, soft X-ray and hard X-ray (> 5 keV) bands recent spacecraft have greatly extended the data base. Good high resolution maps are being made in the microwave region with the ground based VIA. We are now at the point where significant progress into understanding the flare problem has been made, and will continue to be made, during the current solar maximum. This coincides with the development of soft X-ray instruments sensitive enough to detect transient and quiescent emission from flare stars, particularly red dwarfs in the solar neighbourhood (e.g. Kahn et al,1979, Haisch et al, 1980) which previously had only been detected in the optical and radio wavebands.
The Interpretation of EUV Spectra of Sunspots
Authors: Doyle J.G. , Raymond J.C. , Noyes R.W. , Kingston A.E.
Published: July 2016

We report here on EUV observations of a sunspot observed by the Harvard instrument on Skylab. The observational data used here have been presented in a previous paper by Noyes et al. (1982), in which line identifications and intensities for the wavelength region 350 – 1350 A were given. Several electron density sensitive line ratios suggest a constant density, rather than constant pressure, emitting region, while temperature diagnostic line ratios of several ions yield temperatures below the temperatures expected in ionization equilibrium.
RS CVn STARS: Photospheric Phenomena and Rotation
Authors: Catalano S.
Published: July 2016

This review presents a summary of observed photospheric phenomena on RS CVn stars: the amplitude, shape, evolution and migration rate of the photometric wave in relation to the rotational and orbital motion.

The main points considered are: 1) the activity level (maximum amplitude, short and long timescale variability) versus rotation period; 2) the activity cycles as inferred from changes in the wave migration rate and direction and from the variation of its amplitude; 3) the detection of differential rotation; 4) the connection between the orbital period variation and activity.
Recent Photometry of AR Lacertae
Authors: Kang Young Woon , Wood Frank Bradshaw
Published: July 2016

AR Lac is an eclipsing binary of the RS CVn type. The intrinsic variability of one of the components was first announced by Wood (1946) and the presence of sharp H and K emission lines was noted by Wyse (1934). More recent work by Nha and Kang (1982) shows clearly that the light curve varies from year to year. The period is variable.
RS CVn Systems: The High Energy Picture
Authors: Charles P.A.
Published: July 2016

The discovery of X-ray emission from RS CVn systems by HEAO-1 and subsequent surveys by the Einstein Observatory have shown that these close binaries exhibit greatly enhanced coronal activity. Here we review the 3 main observational areas: (1) results of the X-ray surveys of RS CVn systems and other late-type stars which indicate how the X-ray luminosity is correlated with the binary period (and hence stellar rotation) and other coronal activity indicators. This will be discussed in the context of scaled models of the solar corona; (2) X-ray spectroscopy of the most active systems which show multitemperature spectra and line emission consistent with solar abundances of the heavy elements; (3) observations of X-ray “flare-type” activity that has been associated with several RS CVn systems.
The VW Cephei System
Authors: Linnell Albert P. , Pettersen B.R.
Published: July 2016

It is well known that the original Lucy CCE model (Lucy, 1968a, 1968b) was unable to represent W-subclass light curves of W Ursae Majoris stars. Lucy's zero order barotropic model, with gray atmosphere limb darkening produces a deeper transit eclipse and zero color variation with phase. These predictions disagree with observation. Changing the limb darkening coefficient alone, within acceptable limits, cannot deepen occultation eclipse enough to make it deeper than the transit eclipse, as observations require.
Optical Monitoring of T Tauri Stars
Authors: Herbst William
Published: July 2016

At the Van Vleck Observatory of Wesleyan University, Middletown, Connecticut, we have initiated a program of monitoring T Tauri stars with the 24-inch reflector (Perkin Telescope). During the first observing season, we have obtained UBVRI and Hα (30Å and 150Å) data for five stars: T Tau, RY Tau, SU Aur, RW Aur, and CO Ori. The data will be presented elsewhere (Herbst, Holtzman and Phelps, 1982). Here we re-port some of our conclusions.
New Results on the Binary Companion of T Tauri
Authors: Simon Theodore , Schwartz P.R. , Dyck H.M. , Zuckerman B.
Published: July 2016

We have recently reported the discovery of a cool (650–800 K) low-luminosity companion to the pre-main-sequence star, T Tauri (Dyck et al. 1982). We proposed that the optical star and its infrared companion form a physical pair with a N-S separation of 100 a.u. However, there remained in our 2-5 μm speckle interferometry an ambiguity of 180° in the position angle of the secondary. In addition, Cohen et al. (1982) noted an 800 milliarcsec (mas) offset between the visual and 6 cm radio positions at T Tau. Both of these positional discrepancies have now been clarified by accurate visual and radio astrometry of T Tau, and by further near-IR speckle interferometry.
Magnetic Accretion Model for the Activities of Very Young Stars
Authors: Uchida Yutaka
Published: July 2016

A magnetodynamic model is proposed to interpret the observed inflow-outflow-X-ray emitting region complex in the atmospheres of T Tau stars.
Basic Parameters Determining X-Ray Emission Level in Stars of Spectral Type Later than F5
Authors: Paternò Lucio , Zuccarello Francesca
Published: July 2016

This is a merely exploratory search for estimating the importance of those stellar parameters which we believe to be relevant to the X-ray emission from stars possessing outer convective envelopes.

Belvedere et al.(1981,1982) have shown that a mechanism which converts magnetic into thermal energy is plausible for explaining the X-ray emission level in late type main sequence and giant stars. One of the main conclusions of their work is that the average surface X-ray flux Fx depends on the square of the average surface magnetic field strength B. The surface magnetic activity,in stars possessing outer convective envelopes, is likely due to the interaction of rotation with convection which produces both differential rotation (Belvedere et al. 1980a) and dynamo action by the α-effect (Belvedere et al. 1980b).Therefore we would expect that the level of magnetic field intensity depends on star's rotation Ω and the depth of the convection zone(c.z.) D,because both parameters are very important in determining the strength of the interaction.
Theory of the Libration of the Moon
Authors: Dubois-Moons M.
Published: July 2016

The paper presents a new theory of the libration of the Moon, completely analytical with respect to the harmonic coefficients of the lunar gravity field. This field is represented through its fourth degree harmonics for the torque due to the Earth (the second degree for the torque due to the Sun). The Moon is assumed to be rigid and its orbital motion is described by the ELP 2000 solution (Chapront and Chapront-Touzé 1981) for the main problem of lunar theory with planetary perturbations and influence of the non-sphericity of the Earth. Comparisons with other theories (Migus 1980 and Eckhardt 1981) are also presented.
The JPL “Long Ephemeris”, DE102/LE51
Authors: Standish E. Myles
Published: July 2016

A number of applications exist in astronomical research for planetary and lunar ephemerides covering an extended length of time. This paper discusses such a set of ephemerides, DE102/LE51, produced at JPL, covering the time 1411 B.C. to 3001 A.D. The ephemerides are dynamically self-consistent, in that the equations of motion were integrated simultaneously. They also represent the most accurately known positions covering such a time span. They have already been used by a number of different users in a variety of different applications.
A Collection of Galilean Satellite Eclipses 1652–1982
Authors: Lieske Jay H.
Published: July 2016

It is known that early (i.e. 17th-l8th century) visual observations of Jupiter's Galilean satellites are approximately as accurate as modern visually observed eclipses (Lieske 1982). In the early days the clocks were the primary source of error while in present days problems related to the Earth's and Jupiter's atmospheres have become the primary limiting factor. The early observations were generally made in local apparent time (i.e. related to the real hour angle of the sun). After the development by Huygens in 1656 of the pendulum clock, these early observations, when reduced to a modern UT system, have been shown to be quite accurate.
The Orbital Evolution of the Perseid and Quadrantid Meteor Streams
Authors: Fox Ken
Published: July 2016

Some mathematical models of the formation of meteor streams are developed. Some of the testable predictions of these models are compared with observations.
On the Ages of Asteroid Families
Authors: Yuasa Manabu
Published: July 2016

The ages of asteroid families are estimated by using a second order secular perturbation theory. Their ages are rather young. To explain these results we have some possible interpretations. The first interpretation is that in the theory of secular perturbation we do not include the effects of mutual perturbations of asteroids. The second is that we can regard these values as the minimum ages.
Stability and Bifurcations of Symmetric Periodic Orbits in the Restricted
3-Body Problem
Authors: Milani A.
Published: July 2016

The continuation of symmetric periodic orbits can be described in terms of “symmetry functions”; the branching of the zero-level lines in a neighbourhood of a critical point gives rise to the transition from “first kind” to “second kind” periodic orbits. When the families are parametrized with the Jacobi integral, the bifurcations can be described as “catastrophes” of the generating functions. However bifurcations of higher order are more complex than the generic catastrophes with one parameter: both symmetric and asymmetric bifurcations occur.

In this way the symmetric periodic orbits that do not have close approaches to the secondary body can be described in an analytic way and their stability can be deduced from simple bifurcation rules. However numerical experiments are required to determine the “natural termination” of the families.
Properties of symbiotic stars from studies in the optical region
Authors: Ciatti Franco
Published: July 2016

The traditional definition of Symbiotic Stars (SS) is that of objects which display a combination spectrum (e.g. Merrill, 1950) that is emission lines requiring high-excitation conditions, superposed to the continuum and absorption features of a low-temperature star, most commonly an M-type giant. About one hundred of SS are known and listed today. It is anyway apparent that the classification criteria are rather rough, and since the excitation varies from the simple Me to SS with coronal emission, it is not well defined where a clear division should be made. As a result, the available lists include a very heterogeneous set of objects, probably different phases in stellar evolution. Moreover it has been remarked that SS show a rather confusing variety in their spectroscopic and photometric behaviour. Different intensities of both absorption and emission lines are reported from star to star. These facts indicate a high degree of individuality among SS, which is partly cause and/or effect of the adopted definitions.
UV eclipse observations of CI Cyg
Authors: Michalitsianos A.G. , Kafatos M. , Stencel R.E. , Boyarchuk A.A.
Published: July 2016

Low spectral resolution observations (∼ 6 A) were obtained with the International Ultraviolet Explorer (IUE) during its eclipse phase. Additional data obtained by other IUE groups have been included in our eclipse observations, enabling us to examine the UV spectral properties of this system over nearly an entire orbit that spans early 1979 through mid-1981. Data obtained over this time interval suggest an overall decline in UV emission consistent with the decline of optical emission following the outburst of 1975, where CI Cyg attained an increase of ∼ 3 magnitudes in the visual. The short wavelength spectrum λλ1200-2000 A is characterized by numerous intense high excitation emission lines that become more prominent out of eclipse. The LWR wavelength range λλ2000-3200 A exhibits a few more additional lines of 0 III, Mg II and He II that are superimposed on continuum that rises gradually with increasing wavelength. Additionally, OH emission bands are identified at λλ3064, 2875 A (cf. Diecke and Crosswhite 1962). Collaborative ground-based observations of CI Cyg with W. Blair of McGraw Hill Observatory suggest the presence of the Balmer continuum jump at λ3646 A, and enables us to ascribe the UV continuum observed with IUE to mainly Balmer free-bound recombination emission.
Introductory remarks on the symbiotic star AG Draconis
Authors: Oliversen Nancy A. , Anderson Christopher M.
Published: July 2016

AG Draconis contains a relatively early cool component. Quoted spectral types range from dG7 (Wilson 1943) to K3III (Boyarchuck 1969). Most recently Smith and Bopp (1981) adopt G7IIIe. The optical spectrum shows in emission the permitted lines of hydrogen and helium, both neutral and singly ionized. At various times the spectrum of the late type component has been heavily veiled by a blue continuum and numerous lines of various stages of ionization of iron have been seen, including the 6830 A feature which Allen (1980) attributes to Fe VI. On the other hand, on a KPNO echelle spectrum taken by one of the current authors (CMA) in 1977 August, the late giant spectrum was very sharp and no iron or forbidden lines were present. The lack of the forbidden lines identifies AG Dra as a high density case and thus it conforms to the spectral type-density correlation found by Allen (1980).
RR Telescopii
Authors: Whitelock Patricia A. , Catchpole R.M. , Feast M. W.
Published: July 2016

In 1948 the South African amateur astronomers de Kock and Kirchhoff were the first to notice that RR Tel had brightened to 7th magnitude. Subsequent examination of the Harvard Patrol plates showed that it had in fact reached a maximum in 1944 after rapidly brightening 7 magnitudes (Mayall, 1949). Prior to 1944 the object showed variations with a period of 387 days and an amplitude of up to 2 magnitudes in the blue. After the outburst the spectrum evolved in a manner characteristic of very slow novae: an F5 supergiant absorption spectrum gave way to strong permitted and forbidden emission lines. The ionization levels characterising the emission increased with time. The spectral development has been extensively studied and has been well summarised for the period up to 1973 in the Thackeray's (1977) monograph on the subject.
A Type Stars as Probes of the Local Interstellar Medium
Authors: Ferrero R. Freire , Ferlet R. , Vidal-Madjar A.
Published: July 2016

With the aim to sample well the Local Interstellar Medium (LISM),we propose to use A stars as targets. The Mg II UV lines seems to be the best interstellar absorption candidates. Several hundreths of A stars can be reached within 100 pc. First preliminary results (20 lines of sight) are presented, based on previous Copernicus and actual IUE observations.
Distances of Local Clouds from Optical Line Observations
Authors: Crutcher Richard M. , Lien David J.
Published: July 2016

We observed the interstellar D-lines of Na I toward 49 stars in order to determine the distance (125 ± 25 pc) to a cold H I cloud. This sheet of gas may be part of the back side of the shell formed by the Loop I supernova.
A Large-Scale Dark Cloud System in the Northern Sky
Authors: Schlosser Wolfhard
Published: July 2016

Wide-angle photographs of the Northern Milky Way reveal a complex system of dark clouds covering the galactic longitudes from 1 = 90° to about 1 = 200° (fig.). This Northern Dark Cloud System is a coherent structure of individual clouds of preferentially cellular appearance. The cloud system has to be assigned to the local spiral arm. This is substantiated by the large extent in galactic latitudes and its proximity to well-established tracers of the local spiral arm.
Absorption and Emission of EUV Radiation by the Local ISM
Authors: Paresce Francesco
Published: July 2016

The Berkeley EUV telescope flown on the Apollo Soyuz mission in July, 1975 established the existence of a measurable flux of EUV radiation (100 ≤ λ ≤ 1000 Å) originating from sources outside the solar system. White dwarfs, flare stars and cataclysmic variables were discovered to be relatively intense compact sources of EUV photons. Moreover, this and other subsequent experiments have strongly suggested the presence of a truly diffuse component of the EUV radiation field possibly due to thermal emission from hot (T > 105 K) interstellar gas located in the general vicinity of the sun (r ≃ 100 parsecs.) Closer to the HI, 912 Å edge, the effect of a few hot O and B stars has been shown to be very important in establishing the interstellar flux density. All these results imply that the local ISM is immersed in a non-negligible EUV radiation field which, because of the strong coupling between EUV photons and matter, will play a crucial role in determining its physical structure. Conversely, of course, the local ISM is expected to leave a strong imprint on the EUV field reaching the terrestrial observer.

The objective of this review will be to assemble and critically analyze the available information on the local ISM derived from the limited EUV observations carried out so far. These include measurements of the spectra of bright EUV sources that reveal clear evidence of H photo absorption at λ > 400 Å and of the He ionization edge at 228 Å. The EUV diffuse background is found to convey interesting information on the density, temperature and possible location of the hot ISM component that can be profitably compared with similar data on far uv absorption lines, principally OVI. The results discussed in this context will be shown to be quite useful in illuminating the path that future EUV sensitive observatories such as EUVE and Columbus might profitably follow in the near future.
A Warm Magnetoactive Plasma in a Large Volume of Space
Authors: Heiles Carl
Published: July 2016

This paper will show that a diffuse ionized warm gas fills a large volume of space in the general direction of Radio Loop II. There are three types of observational evidence: Faraday rotation measures (RM's) of extragalactic sources; emission measures (EM's) derived from the Hα emission line in the diffuse interstellar medium; and magnetic field strengths in HI clouds derived from Zeeman splitting observations.
An Investigation of Small Scale H I Structure at High Galactic Latitude
Authors: Jahoda K. , Dickey J.M. , Lockman F.J. , McCammon D.
Published: July 2016

We present results of a search for small scale H I structure at high galactic latitudes using the NRAO 140 foot telescope, which has a 21' beam at 21 cm. We examined randomly selected 4° x 5° regions, as well as regions of particularly low total column density. The amount of apparent structure is small in directions with total column densities of a few times 1020 cm-2.
Magnetic Alignment Theory and the Interpretation of Polarization
Authors: Cugnon Pierre
Published: July 2016

This paper presents some reflexions about the theory of magnetic spinning alignment. It is shown that a classical enhanced thermal Davis and Greenstein mechanism may be considered as a limiting case of Purcell's suprathermal spinning alignment theory when the number of active sites on a given grain becomes very important and/or for very short-lived suprathermal sites.

This result is applied to the interstellar medium and some problems in which it may be important are briefly discussed, with special attention to local implications.
Dark Matter Near the Sun: Simulated Star Counts and the Oort Limit
Authors: Gilden David , Bahcall John N.
Published: July 2016

An ensemble of orbits passing through the solar position have been generated for a specific mass model of the galaxy. These orbits are randomly sampled to form simulated density distributions of tracer stars perpendicular to the galactic disk. The simulated distributions are analyzed in order to determine the sampling errors in a self-consistent derivation of the total amount of matter near the sun (the Oort limit).
Stellar Radial Velocities of High Precision: Techniques and Results
Authors: Campbell Bruce , Walker G.A.H.
Published: July 2016

Relative radial velocities can now be determined with internal errors as small as ~ 10 m s−l. A variety of techniques for achieving this level of precision are either presently running, or will soon be on-line. These could be used on several astronomical frontiers; the most demanding application is the search for extra-solar planetary systems. We briefly review these techniques, and highlight the results obtained to date.
Radial Velocities for the Hipparcos Program
Authors: Duflot M.
Published: July 2016

The studies by Fehrenbach show that objective prisms with normal fields are well adapted to a statistical study of stellar motions in our galaxy. Now, thanks to computers we can easily reduce the plates. Since the beginning of 1982 we have been engaged in obtaining radial velocities for the stars (m < 9.0) in the Hipparcos Input Catalogue. We have chosen fields with a large number of stars with spectral types earlier than F5 and with unknown radial velocities. However, in a given field we measure all of the stars.

In Table I we list our instruments and the stars for which they are used.
Largescale Problems of Galactic Structure and Dynamics
Authors: Freeman K.C.
Published: July 2016

In tills review, I will talk about some galactic problems for which stellar radial velocities are important. I will not attempt to be comprehensive, but will just pick out some problems which are being actively studied and which I find particularly interesting.

This is a classical problem. The aim is to estimate the total matter density near the Sun from the distribution and kinematics of a tracer population towards the galactic poles. Recently Bahcall (1984a,b,c) has made a major attack on this problem, using F stars and W giants. He finds that about half the total matter density near the Sun is unaccounted for. This is important. We know from work on other diek galaxies that about half their mass lies in a dark corona and the other half in the disk; the nature of this dark matter is not yet understood. If we also see that about half the mass of the disk itself is dark, then that is certainly worth knowing, because this dark matter has dissipated to the disk. That may help us to understand the nature of the dark matter.
A Search for Halo Binaries: the First Results
Authors: Latham David W. , Stefanik Robert P. , Carney Bruce W.
Published: July 2016

He report the first results from a program to monitor the stars in the Carney and Latham (1985) halo survey for velocity variations due to orbital motion. From the sample of 300 stars with high space velocities, 24 spectroscopie binaries candidates have been identified.

The Halo Survey of Carney and Latham (1985) has identified approximately 300 stars with space velocities greater than 200 km sec−l compared to the local standard of rest. The radial velocities of these stars have been monitored for typically two years, and at least 24 show evidence of possible variation. These stars are listed in Table I, which gives the star name, the number of observations, the number of days between the first and last observations, the mean velocity, the RMS, the U, V, and W velocities, and the speed compared to the galactic rest frame.

The error of a single measurement is perhaps ± 0.7 km sec−1, but depends to some extent on the metallicity and the quality of the spectrum. For a star to be included in Table I as a binary candidates we have chosen a threshold of ± 2.0 km sec−1 for the RMS, or approximately 3 sigma. We plan to monitor the radial velocities of these binary candidates closely over the next few years. We also plan to obtain b-y and V-K colors to search for the light of possible companions.
A Determination of the Radial Velocities of Galaxies
Authors: Popov V.S. , Polyakova G.D.
Published: July 2016

Fourteen galaxies were studied using 24 spectra, obtained with the 6 meter telescope of the Special Astrophysical Observatory of the USSR Academy of Sciences. The dispersion of the spectrograph in the primary focus of the telescope was 189 A/mm.

The neon spectrum was studied in order to determine the wavelengths of the comparison spectrum and to plot a dispersion curve. The following Ne I lines were used for a comparison: 6143, 6266, 6506, 6678, 6717, 6929 and 7032 A. In galactic spectra (wavelength range of 4300 - 7000 A) 21 absorption lines were detected. They belong to H, Na I, Ca I, Ca II, Mg I and otner chemical elements. Three emission lines of the night sky with wavelengths of 5577, 5890 and 6300 A are seen in the spectra of galaxies. They were also used as reference lines for our determination.
Two New Late–Type Degenerates: Implications for the White Dwarf Luminosity Function
Authors: Dahn Conard C. , Monet David G. , Harris Hugh C.
Published: July 2016

Recent preliminary USNO CCD parallax solutions for over 100 fields have yielded relative parallaxes with formal errors less than 0″.0030 for approximately 60 faint (15.9 ≤ V ≤ 20.3) stars. The stars observed include a variety of late-type dwarfs, extreme subdwarfs, and degenerates. Among the latter are the well-known, spectroscopically confirmed degenerates LP543–32/33 (= LHS239/240), LP131–66 (= LHS342), LP754–16 (= LHS483), LP702–7 (= LHS542), LP374–4 (= LHS2364), and LP322–800 (= LHS2673), all of which have Mv ≥ 15.0. In addition, two “new” (in terms of previously lacking both spectroscopic confirmations and absolute luminosity estimates) late-type degenerates were identified — LP53–7 (= LHS1405) and LP550–178 (= LHS2288) — both with proper motions in the range
PG 1707+427: The DOV Star with the Simplest Fourier Transform
Authors: Grauer Albert D. , Liebert James , Green Richard
Published: July 2016

PG 1707+427 was identified in the Palomar-Green survey (Green Schmidt and Liebert, 1986) as an object with a significant ultraviolet excess. Observations by Bond and Grauer in 1982 showed it to be a pulsating variable (Bond, Grauer, Green and Liebert, 1984). Fourier transforms of the discovery time-series photometric runs revealed power in PG 1707+427’s light curves in two bands with periods near 450-s and 333-s. The longer period peak was observed to have a variable amplitude while the other one appeared relatively constant in strength. Wesemael, Green and Liebert (1985) placed PG 1707+427 in the spectroscopic class of PG 1159–035 (DOV) pulsating variables.
Two New Faint Common Proper Motion Pairs
Authors: Ruiz María Teresa , Maza José
Published: July 2016

Spectrophotometry of the common proper motion pairs ES0439-162/163 and ESO440-55a/55b shows that the first is formed by an mv =18.8 magnetic DQ white dwarf and an mv = 19.8 DC9 white dwarf separated by 23”. ESO440-55a/55b has an mv = 20.2 red dwarf (ST=M5.1) component and a DZ7 white dwarf with mv = 19.3, their angular separation being The proper motion of the pairs is μ=0.38±0.03”/year and μ=0.22±0.04”/year respectively.
Far Ultraviolet Observations of Hot DA White Dwarfs
Authors: Finley David , Basri Gibor , Bowyer Stuart
Published: July 2016

Far ultraviolet (FUV) fluxes have been used for determining the effective temperatures of a number of DA white dwarfs hotter than 20,000 K. The spectra were obtained with the International Ultraviolet Explorer (IUE). The analysis consisted of comparing the observed FUV fluxes with model fluxes scaled to the V-band flux. After suitable corrections were performed for the time-dependent sensitivity degradation of the IUE, it was found that the available flux calibrations for the IUE were insufficiently accurate for precise temperature determinations. Accordingly, we used seven white dwarfs for which accurate, independent temperature determinations have been made from line profile analyses to improve the accuracy of the IUE flux calibration. The correction to the original calibration was as great as 20% in individual 5-Å wavelength bins, while the average over the IUE wavelength range was 5%. We present both our IUE flux correction and the temperatures obtained for the hot white dwarfs.
Scaleheights of Low Mass Stars from the Luminosity Function of the Local White Dwarfs
Authors: Rana N.C.
Published: July 2016

It is shown that a combination of the observed luminosity function of the local white dwarfs and the theoretical cooling rates of a typical white dwarf suggests an approximately constant rate of formation of the white dwarfs. This rate is found to be about a factor of three lower than the observed birthrate of their immediate progenitors. This discrepancy is here interpreted as a three-fold increase in the scaleheight of the white dwarfs due to dynamical interaction with stars, molecular clouds; an average white dwarf being much more aged than an average progenitor. Since the low mass stars on an average are even slightly more long-lived than these white dwarfs, one can place a lower bound on the scaleheights of the low mass stars to be given by the required scaleheights of the white dwarfs, which is, according to the present work, 660 pc in the solar neighbourhood.
The Effect of CNO Metal Abundances on the Soft X-Ray Emission from He Rich White Dwarfs
Authors: Barstow M.A.
Published: July 2016

Predicted soft X-ray fluxes for model atmospheres containing varying concentrations of CNO metals are compared with those observed by EXOSAT for the planetary nebula nucleus K1-16. An effective temperature in the range ≈ 125000 − 180000K is determined for K1-16 and a limit on the concentration of CNO in the atmosphere (between 0.02 and 20 ×solar relative to He) obtained. Some comments on the application of the models to the apparently metal rich star H1504+65 are included.
Spectroscopic Studies and Atmospheric Parameters of ZZ Ceti Stars
Authors: Daou D. , Wesemael F. , Bergeron P. , Fontaine G. , Holberg J. B.
Published: July 2016

The pulsating ZZ Ceti stars cover a narrow range of effective temperatures along the cooling sequence of DA white dwarfs (see, eg., Winget and Fontaine 1982). Fast-photometric searches for pulsating stars in that class have provided strong evidence that the ZZ Ceti phase is an evolutionary phase through which all cooling DA stars will eventually go through (Fontaine et al. 1982). Recent investigations, based on optical or ultraviolet photometry and spectrophotometry, have set the boundaries of the instability strip at temperatures near 10,000-11,000 K and 12,000-13,000 K, respectively (McGraw 1979; Greenstein 1982; Weidemann and Koester 1984; Fontaine et al. 1985; Wesemael, Lamontagne, and Fontaine 1986; Lamontagne, Wesemael, and Fontaine 1987, 1988).