The 75th Name-List of Variable Stars
We present the next regular Name-List of variable stars containinginformation on 916 variable stars recently designated in the system ofthe General Catalogue of Variable Stars.
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250 GHz observations of Be stars
New 250 GHz flux density measurements with the 30 m telescope at PicoVeleta are presented for 23 Be stars. We suggest that the radio spectralindex is typically close to 1.4 for these stars. We present in adiscusssion of own and literature data some evidence that in few casesslow variations with a time scale of about a year occur. Both evidenceis compatible with the idea that there is no stellar activity type radioemission of Be stars but a maybe slightly modulated quiescent radiationof the outer parts of selfsimilar circumstellar disks. An immediateimprovement of existing models is not possible.
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Radio observations of IRAS-selected Southern hemisphere classical Be stars
We present the first radio observations of a sample of 13 optically andIR-bright Southern hemisphere classical Be stars made from theAustralian Telescope Compact Array at 3.5 and 6.3 cm simultaneously. Onestar, delta Cen, was detected at 3.5 cm, and a second, mu Cen, was alsothought to have been detected; further observations of this source arerequired to confirm this detection. No sources were detected at 6.3 cm,although delta Cen was previously detected at this wavelength by otherobservers at a higher flux than our detection limit. The radioobservations show that the spectral energy distribution undergoes aturnover between the far-IR and radio wavelengths, as was seen inprevious studies. Likewise we find no simple correlation between far-IRand radio flux. Lower limits to the outer disc radius were found to beof the order of a few hundred solar radii i.e. of the order of thosefound previously by Taylor et al.
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Coupled long-term photometric and V/R variations in Be stars: evidence for prograde global one-armed disk oscillations.
We review theoretical work on global oscillations of Be star disks andsummarize possible observational tests. In addition, we analyze existingrecords on photometric data and V/R ratio for a sample of 6 V/R variableBe stars. Five stars showed coupled long-term photometric-V/Rvariations. In all cases the photometric extrema coincided with times ofV=R transits, the fainter state being followed by a V
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Observations of Ubiquitous Small-Scale Structure in the Diffuse Interstellar Medium
We present results of a study of the Na I D interstellar absorptiontoward 17 binary and/or common proper-motion systems (including twotriples). The stars range in spectral type from O6 to A5, lie atdistances between 85 and 1200 pc, and have stellar separations between480 and 29,000 AU. We compare the Na I absorption present in each of thetwo (or three) lines of sight and find that the line strength and/orprofile varies for all 17 of the systems examined. We infer thatsmall-scale structure in clouds containing Na I is ubiquitous anddiscuss the implications of that conclusion.
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Ultraviolet and Visible Spectropolarimetry of the Red Rectangle and HD 44179
We present the first ultraviolet and visible spectropolarimetry of thebiconical nebula the Red Rectangle and its associated binary HD 44179.These observations were made between 1992 November and 1995 Novemberusing the Faint Object Spectrograph on board the Hubble Space Telescopeand two separate ground-based observations. These new data gives moreclues to the geometrical picture of the region. Previous results havetypically reported linear polarizations in the visible and infrared of1%--2%. We present results that clearly show an increase in thecontinuum polarization shortward of 2000 A into the 10%--15% range. Inaddition, the position angle is seen to rotate by 65 deg in the samewavelength region, probably a result of the bipolar geometry and theexistence of an optically thick equatorial disk. It is also seen thatlines due to Mg II absorption, H alpha emission, and several lines dueto CO are polarized differently than the continuum. There also appear tobe features attributable to OH, which would be extremely unusualconsidering the assumed carbon-rich atmosphere that is present.
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Photographic observations of visual double stars.
We present the results of photographic observations of 399 visual doublestars of the Hipparcos Input Catalogue (HIC), observed in the years 1980and 1990-1991 with the 60-cm double-refractor of the Bosscha Observatoryat Lembang, Java.
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V/R variability and global oscillations in Be star disks.
We present high-resolution Hα and Fe II spectroscopic data on theemission line behaviour of five selected Be stars (HR 3237, δ Cen,48 Lib, α Ara, 66 Oph), four of them showing cyclic V/R lineprofile variability in the period 1982-1993. With the exception of theshell star 48 Lib, these stars temporarily also show a characteristicasymmetric (steeple-type) profile shape in their Fe II λ5317emission line (which we have chosen as characteristical optically thinemission line). These profiles are very similar in all three stars. Incontrast, the star α Ara has been selected because it exhibitssymmetric double-peak profiles for the whole investigated period.Steeple-type profiles are cyclically variable in the sense that theyshow asymmetric line profiles for almost half a cycle, then asymmetryinversion in the second half-cycle, and re-appear with the same shapeafter a full cycle which lasts about 8-10 years. In one star, 66 Oph, wereport the detection of V/R variability onset in the course of 1988,i.e. a sudden transition from a non-varying, symmetric to a variable,asymmetric line profile shape. We demonstrate that this characteristicsteeple-type profile shape and the long-term V/R variability patternknown since long are two manifestations of the same physical phenomenon.We provide arguments in favour of the global disk oscillation scenarioas causing a large-scale perturbation of the quasi-Kepleriancircumstellar disk which precesses under the influence of thenon-spherical gravitational potential of the central star. We finallyspeculate that the onset of such distortion, as observed in 66 Oph,might be related to some viscous instability in the circumstellar disk.
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The local distribution of NA I interstellar gas
We present high-resolution absorption measurements (lambda/Delta lambdaapproximately 75,000) of the interstellar Na I D lines at 5890 A toward80 southern hemisphere early-type stars located in the localinterstellar medium (LISM). Combining these results with other sodiummeasurements taken from the literature, we produce galactic maps of thedistribution of neutral sodium column density for a total of 293 starsgenerally lying within approximately 250 pc of the Sun. These mapsreveal the approximate shape of the mid-plane contours of the rarefiedregion of interstellar space termed the Local Bubble. Its shape is seenas highly asymmetric, with a radius ranging from 30 to 300 pc, and withan average radius of 60 pc. Similar plots of the Galactic mid-planedistribution of sources emitting extreme ultraviolet radiation show thatthey also trace out similar contours of the Local Bubble derived from NaI absorption measurements. We conclude that the Local Bubble absorptioninterface can be represented by a hydrogen column density,NuETA = 2 x 1019 cm-2, which explainsboth the local distribution of Na I absorption and the observed galacticdistribution of extreme ultraviolet sources. The derived mid-planecontours of the Bubble generally reproduce the large-scale featurescarved out in the interstellar medium by several nearby galactic shellstructures.
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Near-IR excess of Be stars.
The near-IR excess emission of 144 Be stars is derived from visual andnear-IR observations. The quasi-simultaneous nature of the observationsprovide colour excesses that are independent of temporal variations.Colour-colour diagrams are used to identify stars with excess coloursmarkedly different from the bulk of the sample stars. The near-IRemission of four stars that have markedly different colours isattributed to the presence of a binary companion or thermal dustemission. The percentage of stars with a significant excess increaseswith wavelength. The excess emission increases with wavelength and thelargest excesses occur in stars of earlier spectral type. The near-IRexcess colours are examined and compared to theoretical excess colourscalculated from a simple bremsstrahlung emitting disc model with aradial density distribution of the form ρ{prop.to}r^-β^. Theeffect of model parameters on the excess colours is discussed. Theobserved excesses for the bulk of the stars are well fit bycircumstellar discs with radii greater than ~10R_*_ and with a densityindex β, in the range 2.0-5.0. This is very similar to the range ofvalues previously determined by Waters et al. from IRAS far-IRobservations. A small number of stars cannot be reconciled with discswith a constant density index out to 10R_*_. It is argued that thecircumstellar plasma around these stars has a change in structure at~2-10R_*_. The possibilities of disc truncation or a change in thedensity index as the cause of the structure change are discussed.
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Differential UVBY photometry of southern Be stars. Highlights from the recent analysis of LTPV data.
Not Available
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Multi-wavelength spectroscopy of the stable shell star HD 193182
HD 193182 is one of the most interesting 'stable shell stars' andpresent stable shell features which seems to be constant over decades.In this research we analyzed optical, ultraviolet and near-infraredspectra of this little-studied shell star. In the meantime we appliedmodel calculations to the measured spectral parameters of HD 193182 inorder to present a more complete view of its stellar and envelopecharacteristics.
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Photographic observations of visual double stars
Results are presented of photographic observations of 186 pairs ofvisual double stars, carried out with the 60-cm visual refractor of theBosscha Observatory at Lembang (Java) between 1984 and 1986. Theprocedures used in observations, measurements, and reducing wereidentical to those described by van Albada-van Dien (1983).
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Long-term and mid-term spectroscopic variations of the Be-shell star HD 184279 (V1294 Aql). I - Observational data
Long-term and midterm spectroscopic variations of the Be-shell star HD184279 between 1971 and 1984 have been investigated using a set ofspectra with a dispersion of 12.3 A/mm in the blue spectral range. Deepradial velocity (RV) changes were found for all the observed shell lines(H, HeI, CaII, FeIII, MgII, FeII, and SiII), with a pseudo-period ofabout 5.5 years and an amplitude of 80-90 km/s. A close correlationbetween RVs of emission and absorption features on the H-beta lineprofile and those of other shell lines is noted. A strong variableprogression of Balmer series shell lines is observed, and drasticchanges in asymmetry for shell lines are shown. The HeI shell spectrumis present throughout all the observations. From the analysis, aprojected equatorial velocity of about 256 km/s and a spectral type ofB1 IV-V are found.
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IRAS observations of Be stars. II - Far-IR characteristics and mass loss rates
Observations of bright Be stars detected at 12, 25, and 60 microns bythe IRAS are discussed. Results show the presence of fully ionizedcircumstellar material, and provide no indication of dust. The rates ofmass loss from the IR in the circumstellar disk are found to be muchhigher than the rates derived from asymmetric UV resonance lines. Inaddition to radiation pressure, a Be mechanism (possibly related torotation and nonradial pulsations) may be an effective driving force.The results suggest that very luminous stars cannot form disks due tothe high radiation pressure that dominates the winds, and that mass lossdue to the Be mechanism is negligible.
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Catalog of O-B stars observed with Tokyo Meridian Circle
A catalog of the O-B stars, selected from 'Blaauw-Parenago' list andRubin's catalog, has been compiled on the FK4 system by the observationsmade with Gautier 8-inch Meridian Circle at the Tokyo AstronomicalObservatory during the period, 1971 to 1979. It contains 1059 stars andwas compiled for the future establishment of high precision propermotions of O-B stars.
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Micrometer measurements of visual double stars (3rd list)
Not Available
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Photographic observations of visual double stars
Photographic observations of 238 pairs of visual binaries obtained on770 plates using the 60-cm visual refractor of Bosscha Observatory(Lembang, Java) during 1976-1979 are reported, continuing the catalog ofvan Albada-van Dien (1983). The data-reduction procedures are brieflydescribed, and the data are presented in a table.
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Supernova progenitors and Be stars - Stellar variability from a 21 century perspective
An assessment of the possible value of the 21-century old Almagest starcatalog for contemporary astronomical investigations suggests that itmay be useful in the detection of intrinsic variation, despite presumedlow levels of precision. This possibility is further raised by thepresence of other interesting objects among those with discrepantobservations, including stars thought to be pulsating despite lyingoutside the blue edge, cooling primary/hot secondary composite spectrumsystems, and long unrecorded stars in regions where nearby dustconcentrations have been postulated. The unique potential offered by thecatalog's 21-century baseline makes it worthy of serious consideration.
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Interpretation of emission line profiles of rotating shells
Simple model calculations are carried out in order to demonstrate howshell properties (geometry, density gradient and rotation) influence theemission line profile. A convenient method is given which allows toderive shell parameters from measured line profiles. The procedure isapplied to the Be stars EW Lac, HD 193182, Pi Aqr, Beta Mon, 66 Oph,Kappa Dra, Zeta Tau, Psi Per, Phi Per. The resulting rotationalvelocities are comparable with those derived from photospheric lines.That means that the emitting region of all the stars considered beginsat the stellar photosphere. The radial extensions of these regions arebetween 3 and 5 photospheric radii. The density gradient does not show asevere deviation from that produced by continuous mass flow.
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Photographische Doppelsternmessungen mit Okularprojektion.
Not Available
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Stars having peculiar spectra.
Not Available
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INHABITED SKY
