Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veranderliche Sterne e.V.
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Secular Evolution in Mira Variable Pulsations
Stellar evolution theory predicts that asymptotic giant branch (AGB)stars undergo a series of short thermal pulses that significantly changetheir luminosity and mass on timescales of hundreds to thousands ofyears. These pulses are confirmed observationally by the existence ofthe short-lived radioisotope technetium in the spectra of some of thesestars, but other observational consequences of thermal pulses are subtleand may only be detected over many years of observations. Secularchanges in these stars resulting from thermal pulses can be detected asmeasurable changes in period if the star is undergoing Mira pulsations.It is known that a small fraction of Mira variables exhibit largesecular period changes, and the detection of these changes among alarger sample of stars could therefore be useful in evolutionary studiesof these stars. The American Association of Variable Star Observers(AAVSO) International Database currently contains visual data for over1500 Mira variables. Light curves for these stars span nearly a centuryin some cases, making it possible to study the secular evolution of thepulsation behavior on these timescales. In this paper we present theresults of our study of period change in 547 Mira variables using datafrom the AAVSO. We use wavelet analysis to measure the period changes inindividual Mira stars over the span of available data. By making linearfits to the period versus time measurements, we determine the averagerates of period change, dlnP/dt, for each of these stars. We findnonzero dlnP/dt at the 2 σ significance level in 57 of the 547stars, at the 3 σ level in 21 stars, and at the level of 6 σor greater in eight stars. The latter eight stars have been previouslynoted in the literature, and our derived rates of period change largelyagree with published values. The largest and most statisticallysignificant dlnP/dt are consistent with the rates of period changeexpected during thermal pulses on the AGB. A number of other starsexhibit nonmonotonic period change on decades-long timescales, the causeof which is not yet known. In the majority of stars, the periodvariations are smaller than our detection threshold, meaning theavailable data are not sufficient to unambiguously measure slowevolutionary changes in the pulsation period. It is unlikely that morestars with large period changes will be found among heretoforewell-observed Mira stars in the short term, but continued monitoring ofthese and other Mira stars may reveal new and serendipitous candidatesin the future.
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Galactic mass-losing AGB stars probed with the IRTS. II.
We are using the 2002 data-release from the Japanese space experimentIRTS to investigate the spatial distribution of galactic mass-losing(>2x 10-8 Msund) AGB stars and the relativecontribution of C-rich and O-rich ones to the replenishment of the ISM.Our sample contains 126 C-rich and 563 O-rich sources which are sortedon the basis of the molecular bands observed in the range 1.4-4.0 mu m,and for which we estimate distances and mass loss rates fromnear-infrared photometry (K and L'). There is a clear dependence ongalactocentric distance, with O-rich sources outnumbering C-rich onesfor rGC< 8 kpc, and the reverse for rGC> 10kpc. The contribution to the replenishment of the ISM by O-rich AGBstars relative to C-rich ones follows the same trend. Although they arerare ( ~ 10% in our sample), sources with 10-6Msund < dot {M} < 10-5 Msunddominate the replenishment of the ISM by contributing to ~ 50% of thetotal of the complete sample. We find 2 carbon stars at more than 1 kpcfrom the Galactic Plane, that probably belong to the halo of our Galaxy.The complete Tables \ref{tab_C-rich} and \ref{tab_O-rich} are availablein electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/403/943}
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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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Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
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Galactic mass-losing AGB stars probed with the IRTS. I.
AGB mass-losing sources are easy to identify and to characterize in thenear-infrared range (1-5 mu m). We make use of the near-infrared dataacquired by the Japanese space experiment IRTS to study a sample ofsources detected in the 2 celestial strips surveyed by the IRTS.Mass-loss rates and distances are estimated for 40 carbon-rich sourcesand 86 oxygen-rich sources of which 8 are probably of S-type. Althoughthe sample is small, one sees a dependence of the relative contributionof the two kinds of sources to the replenishment of the interstellarmedium (ISM) on the galactocentric distance. E.g. from 6 to 8 kpc,oxygen-rich sources in our sample contribute 10-12 times as much ascarbon rich sources, whereas from 10 to 12 kpc, the latters contribute3-4 times as much as the formers. Therefore, one would expect a gradientin the composition of the ISM between 6 and 12 kpc from the GalacticCentre, especially in its dust component. Most of the replenishment(>50%) by AGB stars is due to sources with mass-loss rate larger than10-6 Msun yr-1.
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Infrared Properties of SiO Maser Sources in Late-Type Stars
The results of an SiO maser survey for late-type stars selected by theIRTS (Infrared Telescope in Space) are presented. We have detected SiOJ=1-0, v=1 and/or v=2 lines in 27 stars out of 59 stars. The maserintensity increases with the depth of the H_2O absorption in theinfrared spectra and redness of the 2.2 and 12 mu m color. The columndensities of the water vapor in the target stars were estimated from thedepth of the water absorption in the IRTS spectra. We found that the SiOmaser was detected mostly in the stars with a column density of watervapor higher than 3*E19-3*E20 cm-2. Wefurther estimated the density of hydrogen molecules in the outeratmosphere corresponding to these column densities, obtaining109-1010 cm-3 as a lower limit. Thesevalues are roughly in agreement with the critical hydrogen densitypredicted by models for the excitation of SiO masers. It is possiblethat the SiO masers are excited in clumps with column density evenhigher than this value. The present results provide useful informationfor the understanding of the physical conditions of the outeratmospheres in late-type stars.
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Mira kinematics from Hipparcos data: a Galactic bar to beyond the Solar circle
The space motions of Mira variables are derived from radial velocities,Hipparcos proper motions and a period-luminosity relation. Thepreviously known dependence of Mira kinematics on the period ofpulsation is confirmed and refined. In addition, it is found that Miraswith periods in the range 145-200d in the general Solar neighbourhoodhave a net radial outward motion from the Galactic Centre of75+/-18kms-1. This, together with a lag behind the circularvelocity of Galactic rotation of 98+/-19kms-1, is interpretedas evidence for an elongation of their orbits, with their major axesaligned at an angle of ~17° with the Sun-Galactic Centre line,towards positive Galactic longitudes. This concentration seems to be acontinuation to the Solar circle and beyond of the bar-like structure ofthe Galactic bulge, with the orbits of some local Miras probablypenetrating into the bulge. These conclusions are not sensitive to thedistance scale adopted. A further analysis is given of the short-period(SP) red group of Miras discussed in companion papers in this series. InAppendix A the mean radial velocities and other data for 842 oxygen-richMira-like variables are tabulated. These velocities were derived frompublished optical and radio observations.
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Catalogue of H-alpha emission stars in the Northern Milky Way
The ``Catalogue of Stars in the Northern Milky Way Having H-alpha inEmission" appears in Abhandlungen aus der Hamburger Sternwarte, Band XIin the year 1997. It contains 4174 stars, range {32degr <= l() II< 214degr , -10degr < b() II < +10degr } having the Hαline in emission. HBH stars and stars of further 99 lists taken from theliterature till the end of 1994 were included in the catalogue. We givethe cross-identification of stars from all lists used. The catalogue isalso available in the Centre de Données, Strasbourg ftp130.79.128.5 or http://cdsweb.u-strasbg.fr and at the HamburgObservatory via internet.
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Classification and Identification of IRAS Sources with Low-Resolution Spectra
IRAS low-resolution spectra were extracted for 11,224 IRAS sources.These spectra were classified into astrophysical classes, based on thepresence of emission and absorption features and on the shape of thecontinuum. Counterparts of these IRAS sources in existing optical andinfrared catalogs are identified, and their optical spectral types arelisted if they are known. The correlations between thephotospheric/optical and circumstellar/infrared classification arediscussed.
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Catalogue of stars in the northern Milky Way having H-alpha in emission
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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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Search for stars with intrinsic polarization
Results of polarimetric observations of 55 late-type stars arepresented. Twenty of these stars were found to have appreciablepolarization. The dependence of the degree of polarization on wavelengthis given. It is considered very probable that the polarizations of thestars SAO 141881, 141898, and 160413 are intrinsic.
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Criteria for OH maser emission from circumstellar envelopes of oxygen-rich Mira-type red giants
A large and representative sample of oxygen-rich Mira stars was selectedand observed in the 18 cm OH lines at their optical maximum. A total of14 new OH sources were detected. The OH maser emission is found in theintrinsically bright far-IR objects with late M spectral type. Othercharacteristics of the Miras are high (H-K) and (K-L) colors. Theirperiods are on average longer and their (25-12) colors on average redderthan those of non-OH Miras. The (J-H) and (60-25) colors are the samefor OH and non-OH stars. In most cases, OH and H2O masers existsimultaneously. The observed stars form a sequence along which theperiod and the stellar luminosity increase, the stellar radiusincreases, the dust shell radius increases by a smaller factor, thephotospheric temperature decreases but the dust shell temperature isroughly constant, and the mass loss rate and thus the thickness and thebrighntess of the envelope increase considerably.
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Classification of Mira variables based on visual light curve shape
The paper presents classifications of 368 Mira variables of M, S and Cspectral classes based on the shape of their visual light curve. Theclassification is esentially based on Ludendorff's (1928) scheme and thelight curves used are mainly from the compilation of Campbell (1955).The distribution of light curves over period, mean amplitude, lightcurve asymmetry factor, period variability, and spectral class atmaximum is discussed.
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IRAS catalogues and atlases - Atlas of low-resolution spectra
Plots of all 5425 spectra in the IRAS catalogue of low-resolutionspectra are presented. The catalogue contains the average spectra ofmost IRAS poiont sources with 12 micron flux densities above 10 Jy.
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Mira Stars / X-Andromedae / V-Andromedae / Rt-Aquilae / Rv-Aquilae / Sy-Canis / V-Coronae / W-Draconis / U-Lyncis / S-Lyncis / W-Sagittae / Z-Tauri - Ru-Tauri / U-Virginis / Ru-Virginis
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Classification of 831 two-micron sky survey sources south of +5 degrees.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975AJ.....80.1011H&db_key=AST
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A photographic search for red stars in Aquila-Cygnus
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974A&AS...18..427A&db_key=AST
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Note on the HR-diagram of binary stars
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Spectral Classification of Red Variables Along the Galactic Equator.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956ApJ...124..346C&db_key=AST
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Catalogue and Bibliography of Emission-Line Stars of Types Later than B.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1954ApJS....1..175B&db_key=AST
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Stars having peculiar spectra. Thirteen new variable stars.
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