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Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters
The availability of the Hipparcos Catalogue has triggered many kinematicand dynamical studies of the solar neighbourhood. Nevertheless, thosestudies generally lacked the third component of the space velocities,i.e., the radial velocities. This work presents the kinematic analysisof 5952 K and 739 M giants in the solar neighbourhood which includes forthe first time radial velocity data from a large survey performed withthe CORAVEL spectrovelocimeter. It also uses proper motions from theTycho-2 catalogue, which are expected to be more accurate than theHipparcos ones. An important by-product of this study is the observedfraction of only 5.7% of spectroscopic binaries among M giants ascompared to 13.7% for K giants. After excluding the binaries for whichno center-of-mass velocity could be estimated, 5311 K and 719 M giantsremain in the final sample. The UV-plane constructed from these datafor the stars with precise parallaxes (σπ/π≤20%) reveals a rich small-scale structure, with several clumpscorresponding to the Hercules stream, the Sirius moving group, and theHyades and Pleiades superclusters. A maximum-likelihood method, based ona Bayesian approach, has been applied to the data, in order to make fulluse of all the available stars (not only those with precise parallaxes)and to derive the kinematic properties of these subgroups. Isochrones inthe Hertzsprung-Russell diagram reveal a very wide range of ages forstars belonging to these groups. These groups are most probably relatedto the dynamical perturbation by transient spiral waves (as recentlymodelled by De Simone et al. \cite{Simone2004}) rather than to clusterremnants. A possible explanation for the presence of younggroup/clusters in the same area of the UV-plane is that they have beenput there by the spiral wave associated with their formation, while thekinematics of the older stars of our sample has also been disturbed bythe same wave. The emerging picture is thus one of dynamical streamspervading the solar neighbourhood and travelling in the Galaxy withsimilar space velocities. The term dynamical stream is more appropriatethan the traditional term supercluster since it involves stars ofdifferent ages, not born at the same place nor at the same time. Theposition of those streams in the UV-plane is responsible for the vertexdeviation of 16.2o ± 5.6o for the wholesample. Our study suggests that the vertex deviation for youngerpopulations could have the same dynamical origin. The underlyingvelocity ellipsoid, extracted by the maximum-likelihood method afterremoval of the streams, is not centered on the value commonly acceptedfor the radial antisolar motion: it is centered on < U > =-2.78±1.07 km s-1. However, the full data set(including the various streams) does yield the usual value for theradial solar motion, when properly accounting for the biases inherent tothis kind of analysis (namely, < U > = -10.25±0.15 kms-1). This discrepancy clearly raises the essential questionof how to derive the solar motion in the presence of dynamicalperturbations altering the kinematics of the solar neighbourhood: doesthere exist in the solar neighbourhood a subset of stars having no netradial motion which can be used as a reference against which to measurethe solar motion?Based on observations performed at the Swiss 1m-telescope at OHP,France, and on data from the ESA Hipparcos astrometry satellite.Full Table \ref{taba1} is only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/430/165}
| Hipparcos red stars in the HpV_T2 and V I_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibratedinstantaneous (epoch) Cousins V - I color indices using newly derivedHpV_T2 photometry. Three new sets of ground-based Cousins V I data havebeen obtained for more than 170 carbon and red M giants. These datasetsin combination with the published sources of V I photometry served toobtain the calibration curves linking Hipparcos/Tycho Hp-V_T2 with theCousins V - I index. In total, 321 carbon stars and 4464 M- and S-typestars have new V - I indices. The standard error of the mean V - I isabout 0.1 mag or better down to Hp~9 although it deteriorates rapidly atfainter magnitudes. These V - I indices can be used to verify thepublished Hipparcos V - I color indices. Thus, we have identified ahandful of new cases where, instead of the real target, a random fieldstar has been observed. A considerable fraction of the DMSA/C and DMSA/Vsolutions for red stars appear not to be warranted. Most likely suchspurious solutions may originate from usage of a heavily biased color inthe astrometric processing.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).}\fnmsep\thanks{Table 7 is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/397/997
| Near-infrared observations of candidate extrinsic S stars
Photometric observations in the near infrared for 161 S stars, including18 Tc-rich (intrinsic) stars, 19 Tc-deficient (extrinsic) ones and 124candidates for Tc-deficient S stars, are presented in this paper. Basedon some further investigations into the infrared properties of bothTc-rich and Tc-deficient S stars, 104 candidates are identified as verylikely Tc-deficient S stars. The large number of infrared-selectedTc-deficient S stars provides a convenient way to study the physicalproperties and the evolutionary status of this species of S stars.
| Long period variable stars: galactic populations and infrared luminosity calibrations
In this paper HIPPARCOS astrometric and kinematic data are used tocalibrate both infrared luminosities and kinematical parameters of LongPeriod Variable stars (LPVs). Individual absolute K and IRAS 12 and 25luminosities of 800 LPVs are determined and made available in electronicform. The estimated mean kinematics is analyzed in terms of galacticpopulations. LPVs are found to belong to galactic populations rangingfrom the thin disk to the extended disk. An age range and a lower limitof the initial mass is given for stars of each population. A differenceof 1.3 mag in K for the upper limit of the Asymptotic Giant Branch isfound between the disk and old disk galactic populations, confirming itsdependence on the mass in the main sequence. LPVs with a thin envelopeare distinguished using the estimated mean IRAS luminosities. The levelof attraction (in the classification sense) of each group for the usualclassifying parameters of LPVs (variability and spectral types) isexamined. Table only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/374/968 or via ASTRIDdatabase (http://astrid.graal.univ-montp2.fr).
| Stellar Iron Abundances at the Galactic Center
We present measurements of [Fe/H] for six M supergiant stars and threegiant stars within 2.5 pc of the Galactic center (GC) and one Msupergiant star within 30 pc of the GC. The results are based onhigh-resolution (λ/Δλ=40,000) K-band spectra, takenwith CSHELL at the NASA Infrared Telescope Facility. We determine theiron abundance by detailed abundance analysis, performed with thespectral synthesis program MOOG. The mean [Fe/H] of the GC stars isdetermined to be near solar, [Fe/H]=+0.12+/-0.22. Our analysis is adifferential analysis, as we have observed and applied the same analysistechnique to 11 cool, luminous stars in the solar neighborhood withsimilar temperatures and luminosities as the GC stars. The mean [Fe/H]of the solar neighborhood comparison stars, [Fe/H]=+0.03+/-0.16, issimilar to that of the GC stars. The width of the GC [Fe/H] distributionis found to be narrower than the width of the [Fe/H] distribution ofBaade's window in the bulge but consistent with the width of the [Fe/H]distribution of giant and supergiant stars in the solar neighborhood.
| Speckle Interferometry of New and Problem HIPPARCOS Binaries
The ESA Hipparcos satellite made measurements of over 12,000 doublestars and discovered 3406 new systems. In addition to these, 4706entries in the Hipparcos Catalogue correspond to double star solutionsthat did not provide the classical parameters of separation and positionangle (rho,theta) but were the so-called problem stars, flagged ``G,''``O,'' ``V,'' or ``X'' (field H59 of the main catalog). An additionalsubset of 6981 entries were treated as single objects but classified byHipparcos as ``suspected nonsingle'' (flag ``S'' in field H61), thusyielding a total of 11,687 ``problem stars.'' Of the many ground-basedtechniques for the study of double stars, probably the one with thegreatest potential for exploration of these new and problem Hipparcosbinaries is speckle interferometry. Results are presented from aninspection of 848 new and problem Hipparcos binaries, using botharchival and new speckle observations obtained with the USNO and CHARAspeckle cameras.
| Period-Luminosity-Colour distribution and classification of Galactic oxygen-rich LPVs. I. Luminosity calibrations
The absolute K magnitudes and kinematic parameters of about 350oxygen-rich Long-Period Variable stars are calibrated, by means of anup-to-date maximum-likelihood method, using Hipparcos parallaxes andproper motions together with radial velocities and, as additional data,periods and V-K colour indices. Four groups, differing by theirkinematics and mean magnitudes, are found. For each of them, we alsoobtain the distributions of magnitude, period and de-reddened colour ofthe base population, as well as de-biased period-luminosity-colourrelations and their two-dimensional projections. The SRa semiregulars donot seem to constitute a separate class of LPVs. The SRb appear tobelong to two populations of different ages. In a PL diagram, theyconstitute two evolutionary sequences towards the Mira stage. The Mirasof the disk appear to pulsate on a lower-order mode. The slopes of theirde-biased PL and PC relations are found to be very different from theones of the Oxygen Miras of the LMC. This suggests that a significantnumber of so-called Miras of the LMC are misclassified. This alsosuggests that the Miras of the LMC do not constitute a homogeneousgroup, but include a significant proportion of metal-deficient stars,suggesting a relatively smooth star formation history. As a consequence,one may not trivially transpose the LMC period-luminosity relation fromone galaxy to the other Based on data from the Hipparcos astrometrysatellite. Appendix B is only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| On the Variability of S Stars as Observed by the Hipparcos
The Hipparcos photometry of S type stars shows that they are allvariable. The intrinsic S stars show a larger range of amplitudes thando the extrinsic S stars.
| Circumstellar shells and mass loss rates: Clues to the evolution of S stars
It is the purpose of this paper to rediscuss the circumstellarproperties of S stars and to put these properties in perspective withour current understanding of the evolutionary status of S stars, inparticular the intrinsic/extrinsic dichotomy. This dichotomy states thatonly Tc-rich (``intrinsic'') S stars are genuine thermally-pulsingasymptotic giant branch stars, possibly involved in the M-S-Cevolutionary sequence. Tc-poor S stars are referred to as ``extrinsic''S stars, because they are the cooler analogs of barium stars, and likethem, owe their chemical peculiarities to mass transfer across theirbinary system. Accordingly, an extensive data set probing thecircumstellar environment of S stars (IRAS flux densities, maseremission, CO rotational lines) has been collected and criticallyevaluated. This data set combines new observations (9 stars have beenobserved in the CO J=2-1 line and 3 in the CO J=3-2 line, with four newdetections) with existing material (all CO and maser observations of Sstars published in the literature). The IRAS flux densities of S starshave been re-evaluated by co-adding the individual scans, in order tobetter handle the intrinsic variability of these stars in the IRASbands, and possible contamination by Galactic cirrus. In the (K - [12],[25] - [60]) color-color diagram, S stars segregate into five distinctregions according to their Tc content and ZrO/TiO, C/O and IR spectralindices. Stars with photospheric colors (populating ``Region A'') may beidentified with extrinsic S stars. For the other regions characterizedby different excess levels in the 12, 25 and 60 mu m bands, severaldiagnostics (like the IRAS spectral class, maser emission, and shape ofCO rotational lines) have been collected to infer the physicalproperties of the dust shell. A simple radiative-transfer code has alsobeen used to infer the chemical nature (carbonaceous or silicate) of thedust grains from the observed IR colors. S stars with large K - [12]excesses and moderate [25] - [60] excesses (populating Regions B and C)exhibit the signatures of oxygen-rich shells (9.7 mu m silicate emissionand SiO maser emission). The situation is less clear for S stars withsmall K - [12] and moderate [25]-[60] indices (populating Regions D andE). Their IR colors are consistent with carbonaceous grains (as is theirfeatureless IRAS spectrum, and absence of silicate or SiO maseremission), but these features may equally well be explained by adetached shell. For many of these stars with a large 60 mu m excess, theshell is indeed resolved by the IRAS beam at 60 mu m. The prototypicalSC star FU Mon is among these. Since SC stars are believed to be in avery short-lived evolutionary phase where C/O = 1 within 1%, FU Mon maybe a good candidate for the ``interrupted mass-loss'' scenario advocatedby \cite[Willems & de Jong (1988).]{Wi88} The CO line profile of FUMon is also peculiar in being quite narrow (V_e = 2.8 km ssp {-1}),suggesting that the mass loss has just resumed in this star. Mass lossrates or upper limits have been derived for all S stars observed in theCO rotational lines, and range from < 2;10(-8) Msb ȯ y(-1) forextrinsic S stars to 1;10(-5) Msb ȯ y(-1) (the Mira S star W Aql).These mass-loss rates correlate well with the K - [12] color index,which probes the dust loss rate, provided that mathaccent 95 M ga 10({-)8} Msb ȯ y(-1) . Small mass-loss rates are found for extrinsic Sstars, consistent with their not being so evolved (RGB or Early-AGB) asthe Tc-rich S stars. This result does not support the claim often madein relation with symbiotic stars that binarity strongly enhances themass-loss rate. Based on observations carried out at the CaltechSubmillimeter Observatory (Mauna Kea, Hawaii).
| 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.
| Luminosity and Temperature from Near-Infrared Spectra of Late-Type Giant Stars
We present moderate resolution (lambda / Delta lambda ~ 1380 and lambda/ Delta lambda ~ 4830) spectra of 43 K0 to M6 III stars covering 2.19 -2.34 mu m and measure equivalent widths of the strongest absorptionfeatures - Na I, Ca I, and (12) CO(2,0) - present on the spectra. Thehigh resolution Wallace & Hinkle (1996) spectral atlas shows thatour moderate resolution measurements of the atomic features havesignificant contributions from other species, such as Sc, S, Fe, Ti, Si,and V. We also find that our measured equivalent widths are affected byCN absorption present in the continuum bands. In spite of this, theequivalent widths of Na I and Ca I features at moderate resolution stillshow a strong dependence on effective temperature. The CO equivalentwidth at moderate resolution is less affected by other lines andcontinuum placement than the atomic features, because of its relativelygreater strength. We compare our data to similar data taken forlate-type dwarf stars (Ali et al. 1995) and find that a two dimensionalspectral classification can be constructed based on the near-IR spectra.The quantity log[EW(CO)/(EW(Na)+EW(Ca))] is a strong luminosityindicator independent of effective temperature, while the equivalentwidth of (12) CO(2,0) has a well-defined dependence on effectivetemperature for a given luminosity. This two dimensional spectralclassification is ideal for cool stars obscured by dust in, for example,the central part of the Galactic bulge and regions of star formation.
| A catalogue of [Fe/H] determinations: 1996 edition
A fifth Edition of the Catalogue of [Fe/H] determinations is presentedherewith. It contains 5946 determinations for 3247 stars, including 751stars in 84 associations, clusters or galaxies. The literature iscomplete up to December 1995. The 700 bibliographical referencescorrespond to [Fe/H] determinations obtained from high resolutionspectroscopic observations and detailed analyses, most of them carriedout with the help of model-atmospheres. The Catalogue is made up ofthree formatted files: File 1: field stars, File 2: stars in galacticassociations and clusters, and stars in SMC, LMC, M33, File 3: numberedlist of bibliographical references The three files are only available inelectronic form at the Centre de Donnees Stellaires in Strasbourg, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5), or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The energy distribution in the visible spectrum for 27 class M giants and supergiants
Not Available
| The Chemical Composition of Red Giants. IV. The Neutron Density at the s-Process Site
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...450..302L&db_key=AST
| H-alpha measurements for cool giants
The H-alpha line in a cool star is usually an indication of theconditions in its chromosphere. I have collected H-alpha spectra of manynorthern G-M stars, which show how the strength and shape of the H-alphaline change with spectral type. These observations detect surprisinglittle variation in absoption-line depth (Rc approximately0.23 +/- 0.08), linewidth (FWHD approximately 1.44 +/- 0.22 A), orequivalent width (EW approximately 1.12 +/- 0.17 A) among G5-M5 IIIgiants. Lines in the more luminous stars tend to be broader and strongerby 30%-40% than in the Class III giants, while the H-alpha absorptiontends to weaken among the cooler M giants. Velocities of H-alpha andnearby photospheric lines are the same to within 1.4 +/- 4.4 km/s forthe whole group. To interpret these observations, I have calculatedH-alpha profiles, Ly-alpha strengths, and (C II) strengths for a seriesof model chromospheres representing a cool giant star like alpha Tau.Results are sensitive to the mass of the chromosphere, to chromospherictemperature, to clumping of the gas, and to the assumed physics of lineformation. The ubiquitous nature of H-alpha in cool giants and the greatdepth of observed lines argue that chromospheres of giants cover theirstellar disks uniformly and are homogeneous on a large scale. This isquite different from conditions on a small scale: To obtain a highenough electron density with the theoretical models, both to explain theexitation of hydrogen and possibly also to give the observed C IImultiplet ratios, the gas is probably clumped. The 6540-6580 A spectraof 240 stars are plotted in an Appendix, which identifies the date ofobservation and marks positions of strong telluric lines on eachspectrum. I assess the effects of telluric lines and estimates that thestrength of scattered light is approximately 5% of the continuum inthese spectra. I give the measurements of H-alpha as well as equivalentwidths of two prominent photospheric lines, Fe I lambda 6546 and Ca Ilambda 6572, which strengthen with advancing spectral type.
| 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.
| Evidence for sudden moderate mixing events in early M giants
We have determined the C-12/C-13 ratio in 8 M giants and combined ourdata with previous measurements to establish that in early M giantsC-12/C-13 = 11.8 +/- 3.8, where 3.8 is the dispersion, not the standarderror of the mean. This low ratio, comparable to the ratio in thecoolest red giants and clump stars in M67, has been combined withlithium abundances for the same stars, as reported in the literature.The Li abundances range over three orders of magnitude while theC-12/C-13 ratio is virtually constant. We interpret this as due to smallsudden mixing processes during the evolution of M giants that bringsrecently produced Li-7 to the stellar surface, without penetrating todepths at which the C-12/C-13 ratio would be modified.
| S stars: infrared colors, technetium, and binarity
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...271..463J&db_key=AST
| On the Infrared Properties of S-Stars with and Without Technetium
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...271..180G&db_key=AST
| Infrared spectroscopy of symbiotic stars - Carbon abundances and C-12/C-13 isotopic ratios
Intermediate-resolution spectra of a sample of symbiotic stars in the Kand L bands are obtained. Pfund and Brackett emission lines as well asthe first-overtone CO absorption bands are detected. Synthetic spectraare used to fit the CO absorption features and to obtain carbonabundances and C-12/C-13 ratios. Subsolar carbon abundances are found inthe symbiotic red giants with little scatter from star to star. TheC-12/C-13 ratios are also lower than the solar value. No modificationsdue to binarity are detected. The synthetic spectra were used to obtainangular diameters for some of the symbiotic red giants. A modifiedscheme applicable to symbiotic stars is given which enables accuratespectral classification of red giants embedded in strong nebularemission.
| A Photometric Survey of Small-Amplitude Red Variables
Not Available
| Asymptotic giant branch stars near the sun
Available red and near-infrared photometry and apparent motions of M, S,and C asymptotic giant branch (AGB) stars in the Bright Star Catalogueare tabulated and discussed. It is shown that the red and near infraredindices normally used for late-type stars are interchangeable except forcarbon stars. The M-type giants are variable with visual amplitudegreater than 0.05 mag. The reddening-free parameter m2 from Genevaphotometry is essentially a temperature parameter for M giants, whilethe reddening-free parameter d is a sensitive detector of blue stellarcompanions. The space density of AGB stars near the sun decreases by afactor of 35 in a temperature range 3800 to 3400 K. Two of the S starsnear the sun were found to have nearly equal space motions and may becomembers of the Arcturus group.
| A catalogue of Fe/H determinations - 1991 edition
A revised version of the catalog of Fe/H determinations published by G.Cayrel et al. (1985) is presented. The catalog contains 3252 Fe/Hdeterminations for 1676 stars. The literature is complete up to December1990. The catalog includes only Fe/H determinations obtained from highresolution spectroscopic observations based on detailed spectroscopicanalyses, most of them carried out with model atmospheres. The catalogcontains a good number of Fe/H determinations for stars from open andglobular clusters and for some supergiants in the Magellanic Clouds.
| The Longperiod Symbiotic Binary Ch-Cygni - Part Two - the M Giant Component - Increasing Pulsation Period and Spot-Like Activity
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1992A&A...254..127M&db_key=AST
| Echelle spectroscopy of the symbiotic star CH Cygni through quiescence
High- and low-resolution optical spectroscopy, coupled with opticalphotometry, of Ch Cygni during the period from June 1986 to May 1990 ispresented. The variation in Balmer line fluxes correlates with changesin emission from the hot component, and is consistent with thepreviously published orbital solution. Radial velocities for lines fromvarious parts of the system are determined and compared with previousresults. The origin of the double-peaked profiles of the Balmer lines isexplored. Variations in radial velocity about the orbital RV curve areargued to be greater than those normally observed for isolated redgiants. Observations of the forbidden O III 5007A emission line in June1986 confirm that if this originates in the gas associated with theradio jets, the jets are moving approximately in the plane of the sky. Acollimation mechanism associated with the orbital plane of the binary isinferred from this. Infrared spectroscopy in May 1990 indicates that thecool component is of the spectral type M7 or later.
| Infrared observational study of MS and CS stars
The results of JHK observation of a set of MS and CS stars arepresented. Combining IRAS, PSC, and LRS data, their propertiesthroughout the infrared are discussed, and their roles as intermediatetypes between the M and S stars and between the S and C stars arepointed out. The possible existence of an evolutionary series in thelate type stars, M-MS-S-SC-C, is shown.
| The chemical composition of red giants. III - Further CNO isotopic and s-process abundances in thermally pulsing asymptotic giant branch stars
Near-IR and IR spectra are analyzed to obtain elemental and isotopic C,N, and O abundance, iron peak abundances, and heavy element s-processabundances for a sample of M, MS, and S giants. The compositions of theM giants are similar to those of G and K giants and consistent withpredictions for giants that have deep convective envelopes and so haveexperienced the first dredge-up. The MS and S giants have compositionsthat show the signatures of the third dredge-up that occurs in thermallypulsing AGB stars. The sample shows that C-12, a principal product ofthe He-burning shell, has been added to the envelopes of MS and S stars.The C-12 enrichment is correlated with a more marked enrichment of thes-process elements that are predicted to be synthesized when a neutronsource is ignited in the He-burning shell. The MS and S giants show ahigher N abundance than the M giants, attributed to the expected deepmixing that occurs with the onset of the episodic third dredge-up.
| S stars without technetium - The binary star connection
An exploratory survey of non-Mira MS and S star radial velocities andthe He I 10830 A triplet are used to test the assertion that S starswithout Tc are spectroscopic binaries, probably with white-dwarfcompanions. It is found that the He I 10830 A triplet is a prominentfeature of the spectra of S stars without Tc, but the He I line isundetectable in the spectra of most S stars without Tc. Also, whenradial-velocity variations attributable to orbital motion are detectedfor S stars without Tc, the variations have a higher frequency that thatof S stars with Tc. The results suggest that the S stars without Tc arespectroscopic binaries and are probably related to the G and K giantBarium stars.
| Third preliminary catalogue of stars observed with the photoelectric astrolabe of the Beijing Astronomical Observatory.
Not Available
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Pozíciós és asztrometriai adatok
| Csillagkép: | Hattyú |
| Rektaszcenzió: | 19h33m41.60s |
| Deklináció: | +49°15'45.0" |
| Vizuális fényesség: | 5.96 |
| Távolság: | 448.43 parszek |
| RA sajátmozgás: | 4.1 |
| Dec sajátmozgás: | -12.2 |
| B-T magnitude: | 8.075 |
| V-T magnitude: | 6.231 |
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