Polarization Measurements of Post-Asymptotic Giant Branch Candidates and Related Stars
We have obtained UBVRI polarization measurements of 26 post-asymptoticgiant branch (post-AGB) candidates and related stars. The extremelymetal-poor post-AGB star HR 4049 has been observed several times. Inmost cases we find the objects to be intrinsically polarized. Thepolarization measurements presented in this paper indicate asymmetriccircumstellar dust shells and disks around these stars. For some objectsthe steep percent polarization λ-dependence and large degree ofpolarization suggest that scattering by circumstellar dust grains may beresponsible for the observed polarizations in the blue.
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Coordinates and Identifications of Harvard Variables
Coordinates and identifications are presented for 726 Harvard Variablestars and suspected variables, discovered or studied by D. Hoffleit andannounced in Harvard Bulletins 874, 884, 887, 901, and 902; plus 141others, previously known, lying in the same fields.
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Water Masers Associated with Circumstellar Shells
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..106..579B&db_key=AST
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Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
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On the OH emission from RV Tauri variable stars
Consideration is given to OH emission at 18 cm toward nine RV Tau starsin order to determine the expansion velocities and to check for theprobable presence of molecular abundance anomalies in the envelope. Theonly two published detections, in TX Per and RV Tau, to a significantlybetter noise level are not confirmed. The only emission peak detectedtoward RV Tau at 1667 and 1665 MHz is identified as probablyinterstellar. It is concluded that the earlier determination of highexpansion velocities in the envelopes of RV Tau stars based on OH maseremission cannot be considered as reliable and a low expansion velocityis favored for these stars. The nondetection of OH emission and the weakCO emission can be interpreted in terms of a deficiency of molecules inthe envelopes of RV Tau stars. Possible evolutionary links between RVTau stars and other kinds of objects are discussed on the basis of theabsence of OH emission.
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The post-AGB evolution of low-mass stars
New molecular observations of RV Tauri variables and of the relatedobject 89 Her are presented, and the already existing data arere-examined. The molecular emission of these objects is analyzed usingnumerical models for excitation and line formation. The infraredemission of these stars and some low-mass protoplanetary nebulae (PPNe)is also studied. It is deduced that the envelopes around RV Tau starswere formed by mass loss processes at rates of 4 x 10 to the -7th to 7 x10 to the -6th solar mass/yr. Several low-luminosity PPNe that areprobably issued from objects similar to the RV tauri stars wereidentified. Several observable parameters varying during thepostasymptotic-giant-branch (AGB) evolution of low-mass objects aredetermined. It is found that, during this segment of the stellarevolution, phases of negligible mass loss alternate with others in whichmass loss is very important (up to 6 x 10 to the -7th solar mass/yr). Itis suggested that these protoplanetary mass loss processes are directlyrelated to the evolution itself.
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OH maser emission from warm variable stars
Main line (1665 MHz/1667 MHz) OH emission from three warm variablestars, TW Aql, TX Per, and RV Tau, has been discovered. These stars arespectral class G when they are warmest and are considerably hotter thannearly all known stellar masers. The discovery of maser emission fromthese stars greatly enlarges the range of stellar types from which maseremission is observed.
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Factor analysis of the DDO colours of RV Tauri and SRd stars
The properties of RV Tauri and SRd stars in the DDO photometric systemhave been examined by means of the factor analysis. Within the limitsdue to the restricted sample, this analysis supports the spectroscopicclassification of these objects, and confirms the usefulness of the DDOphotometry to study them. Some objects with peculiar characteristics arediscussed.
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On the Semiregular Variable Tw-Aquilae
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A photometric investigation of RV Tauri and yellow semiregular variables
Results are presented for DDO and UBV photoelectric photometry of 52 RVTau and semiregular variables and candidates. CN abundances, effectivetemperatures, surface gravities, absolute visual magnitudes, and massestimates are derived in the framework of the spectroscopic groupingsproposed by Preston et al. (1963). The photometry suggests a furtherdivision of Preston's group A, and a possible physical connection isindicated between this group and the semiregular variables. Thespectroscopic groups are shown to be well separated in the DDOcolor-color diagrams when mean colors are used for individual stars. Anupper limit of about 3 solar masses is determined for stars in eachgroup. A correlation between derived iron abundances and published IRexcesses obtained from flux measurements at 3.6 and 11.3 microns isfound which supports the contention that dust production incircumstellar shells increases with increasing metallicity.
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Observations d'étoiles variables. Années 1946 à 1952
Not Available
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Observation d'étoiles variables à longues périodes ou irrégulières, effectuées durant l'année 1953 à l'Observatoire de Lyon
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The Semiregular Variable Stars of the RV Tauri and Related Classes.
Abstract image available at:http://adsabs.harvard.edu/abs/1952ApJ...115...25J
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20 new variable stars in Harvard Map, Nos. 2, 5, 32, 44 and 53
Not Available
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