The heterogeneous class of lambda Bootis stars
We demonstrate that it is arduous to define the lambda Boo stars as aclass of objects exhibiting uniform abundance peculiarities which wouldbe generated by a mechanism altering the structure of their atmosphericlayers. We collected the stars classified as lambda Boo up to now anddiscuss their properties, in particular the important percentage ofconfirmed binaries producing composite spectra (including our adaptiveoptics observations) and of misclassified objects. The unexplained RVvariables (and thus suspected binaries), the known SB for which we lackinformation on the companion, the stars with an UV flux inconsistentwith their classification, and the fast rotating stars for which noaccurate abundance analysis can be performed, are also reviewed.Partly based on observations collected at the CFH Telescope (Hawaii) andat TBL of the Pic du Midi Observatory (France).Table \ref{tab5} is only available in electronic form athttp://www.edpsciences.org
|
Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i
This work is the second part of the set of measurements of v sin i forA-type stars, begun by Royer et al. (\cite{Ror_02a}). Spectra of 249 B8to F2-type stars brighter than V=7 have been collected at Observatoirede Haute-Provence (OHP). Fourier transforms of several line profiles inthe range 4200-4600 Å are used to derive v sin i from thefrequency of the first zero. Statistical analysis of the sampleindicates that measurement error mainly depends on v sin i and thisrelative error of the rotational velocity is found to be about 5% onaverage. The systematic shift with respect to standard values fromSlettebak et al. (\cite{Slk_75}), previously found in the first paper,is here confirmed. Comparisons with data from the literature agree withour findings: v sin i values from Slettebak et al. are underestimatedand the relation between both scales follows a linear law ensuremath vsin inew = 1.03 v sin iold+7.7. Finally, thesedata are combined with those from the previous paper (Royer et al.\cite{Ror_02a}), together with the catalogue of Abt & Morrell(\cite{AbtMol95}). The resulting sample includes some 2150 stars withhomogenized rotational velocities. Based on observations made atObservatoire de Haute Provence (CNRS), France. Tables \ref{results} and\ref{merging} are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/897
|
Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable 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/qcar?J/A+A/367/521
|
Photoelectric Photometry of Herbig Ae/be and Related Stars in the Vilnius Photometric System
A catalog of photoelectric photometry of 62 Herbig Ae/Be and relatedstars in the Vilnius system is presented. It contains stars down to V =12 mag located mainly in the northern hemisphere and observed in theperiod of 1994--1996.
|
New lambda Bootis stars with a shell
We publish here the second part of our spectroscopic survey at highdispersion of some known and suspected lambda Bootis stars with a viewto detecting circumstellar shell features. Eight stars of our sampleexhibit such features. These stars are fast rotators, a result which isin line with Hohlweger and Rentzsch-Holm's study (1995). The analysis ofthe photometric data has allowed us to confirm the exclusion of a fewstars misclassified from the lambda Bootis group.
|
A consolidated catalogue of lambda Bootis stars
lambda Bootis stars challenge our understanding of diffusion andaccretion processes related to stars and their circumstellarenvironment, and they are interesting components of the classicalinstability strip. Attempts to derive group properties with statisticalmethods are severely limited by the small number of unambiguouslyidentified lambda Bootis stars. In general, the subject appears to beobscured by incorrect memberships and it is therefore essential toprovide a sufficiently large catalogue of definitive group membersbefore modeling the lambda Bootis phenomenon. This paper describes thefirst steps towards this goal, based on our current knowledge of wellinvestigated members, leading to a concise definition of lambda Bootisstars: {Pop I hydrogen burning metal poor (except of C,N,O and S) A-typestars.} The definition does not depend on phenomenological features,like flux depressions, colour excesses, v sin i values, etc. Based on anew homogeneous catalogue with 45 lambda Bootis stars, we discussclassification criteria which can be used for a spectroscopic andphotometric all-sky survey for lambda Bootis stars in the field and inclusters of different ages. Based on observations obtained atESO-La,Silla, CTIO, Observatoire de Haute-Provence, OsservatorioAstronomico di Padua-Asiago, Univ. Toronto Southern Observatory,Observatorio do Pico dos Dias-LNA/CNPq/MCT (Brazil). Table 1 is alsoavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html.
|
The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..135A&db_key=AST
|
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.
|
Three other λ Bootis stars with a shell.
High signal-to-noise ratio spectra have been taken to detect a possiblecircumstellar shell around λ Boo stars. It is more and moreassumed that circumstellar matter can be found around such stars. Wehave considered the CaII K, Hγ and CaI λ4427 lines. Twospectra of λ Boo stars (HD 16955 and HD 104965) showcircumstellar shell features in the K-line. Such features could also bepresent in the spectrum of HD 220061 and we confirm the circumstellarshell recently found for 131 Tau by Bohlender & Walker (1994).
|
Catalogue of Lambda Bootis Candidates
Not Available
|
Further DA Photometry of I-Bootis Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989A&AS...81..335M&db_key=AST
|
Search for Lambda Bootis type candidates
An extensive search for Lambda Bootis candidates has been madethroughout the whole Geneva photometric catalogue and 17 stars have beenfound, matching the photometric conditions to be Lambda Bootis stars.Thirteen stars proposed by Abt (1984) as Lambda Bootis candidates, onthe basis of the weakness of the 4481 Mg II line, also match theseconditions.
|
Four-color and Hβ photometry for the brighter AO type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&AS....5..109C&db_key=AST
|
A catalogue of proper motions for 437 A stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&AS....1..189F&db_key=AST
|
Photoelectric observations of early A stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&AS....1..165J&db_key=AST
|
