|New periodic variables from the Hipparcos epoch photometry|
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
|The proper motions of fundamental stars. I. 1535 stars from the Basic FK5|
A direct combination of the positions given in the HIPPARCOS cataloguewith astrometric ground-based catalogues having epochs later than 1939allows us to obtain new proper motions for the 1535 stars of the BasicFK5. The results are presented as the catalogue Proper Motions ofFundamental Stars (PMFS), Part I. The median precision of the propermotions is 0.5 mas/year for mu alpha cos delta and 0.7mas/year for mu delta . The non-linear motions of thephotocentres of a few hundred astrometric binaries are separated intotheir linear and elliptic motions. Since the PMFS proper motions do notinclude the information given by the proper motions from othercatalogues (HIPPARCOS, FK5, FK6, etc.) this catalogue can be used as anindependent source of the proper motions of the fundamental stars.Catalogue (Table 3) is only available at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (220.127.116.11) or viahttp://cdsweb.u-strastg.fr/cgi-bin/qcat?J/A+A/365/222
|Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions|
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over more than twocenturies and summarized in the FK5. Part I of the FK6 (abbreviatedFK6(I)) contains 878 basic fundamental stars with direct solutions. Suchdirect solutions are appropriate for single stars or for objects whichcan be treated like single stars. From the 878 stars in Part I, we haveselected 340 objects as "astrometrically excellent stars", since theirinstantaneous proper motions and mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,199 of the stars in Part I are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives in addition to the SI mode the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(I) proper motion in the single-star mode is 0.35 mas/year. This isabout a factor of two better than the typical HIPPARCOS errors for thesestars of 0.67 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(I) proper motions have atypical mean error of 0.50 mas/year, which is by a factor of more than 4better than the corresponding error for the HIPPARCOS values of 2.21mas/year (cosmic errors included).
|The ROSAT all-sky survey catalogue of optically bright main-sequence stars and subgiant stars|
We present X-ray data for all main-sequence and subgiant stars ofspectral types A, F, G, and K and luminosity classes IV and V listed inthe Bright Star Catalogue that have been detected as X-ray sources inthe ROSAT all-sky survey; several stars without luminosity class arealso included. The catalogue contains 980 entries yielding an averagedetection rate of 32 percent. In addition to count rates, sourcedetection parameters, hardness ratios, and X-ray fluxes we also listX-ray luminosities derived from Hipparcos parallaxes. The catalogue isalso available in electronic form via anonymous ftp tocdsarc.u-strasbg.fr (18.104.22.168) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
|Convection, Thermal Bifurcation, and the Colors of A Stars|
Broadband ultraviolet photometry from the TD-1 satellite andlow-dispersion spectra from the short wavelength camera of IUE have beenused to investigate a long-standing proposal of Bohm-Vitense that thenormal main-sequence A and early-F stars may divide into two differenttemperature sequences: (1) a high-temperature branch (and plateau)comprised of slowly rotating convective stars, and (2) a low-temperaturebranch populated by rapidly rotating radiative stars. We find noevidence from either data set to support such a claim, or to confirm theexistence of an "A-star gap" in the B-V color range 0.22 <= B-V <=0.28 due to the sudden onset of convection. We do observe, nonetheless,a large scatter in the 1800--2000 A colors of the A--F stars, whichamounts to ~0.65 mag at a given B-V color index. The scatter is notcaused by interstellar or circumstellar reddening. A convincing case canalso be made against binarity and intrinsic variability due topulsations of delta Sct origin. We find no correlation with establishedchromospheric and coronal proxies of convection, and thus nodemonstrable link to the possible onset of convection among the A--Fstars. The scatter is not instrumental. Approximately 0.4 mag of thescatter is shown to arise from individual differences in surface gravityas well as a moderate spread (factor of ~3) in heavy metal abundance andUV line blanketing. A dispersion of ~0.25 mag remains, which has noclear and obvious explanation. The most likely cause, we believe, is aresidual imprecision in our correction for the spread in metalabundances. However, the existing data do not rule out possiblecontributions from intrinsic stellar variability or from differential UVline blanketing effects owing to a dispersion in microturbulentvelocity.
|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.
|Santiago Fundamental Catalogue - A catalogue of 1105 FK5 stars (equinox J2000.0)|
The positions in right ascension and declination of 1105 FK5 stars,observed with a Meridian Circle during the period 1979 to 1991, aregiven. The average mean square error of a position, for the wholecatalog, is +/- 0.009 s in right ascension and +/- 0.10 arcsec indeclination. The mean epoch of the catalog is 1983.148.
|Santiago declination catalogue. II - A declination catalogue of 493 FK5 stars (equinox J2000.0)|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1991A&AS...90..109C&db_key=AST
|Physical data of the fundamental stars.|
|Two-colour diagrams for differentially rotating stars|
|Santiago declination catalogue - A declination catalogue of 412 FK4 stars (equinox 1950.0)|
This catalog contains the positions in declination, of 412 FK4 stars.The observations were carried out with the Repsold Meridian Circle atCerro Calan National Astronomical Observatory, during the period1963-1968. The average mean square error of one observation (for thewhole catalog) is + or - 0.13 arcsec. The mean epoch of observation ofthe catalog is 1965.75.
|Erratum - Discordances Between SAO and HD Numbers for Bright Stars|
|Rotational Velocities and Spectral Types of Some A-Type Stars|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972PASP...84..584L&db_key=AST
|Four-colour and H BET photometry of some bright southern stars- II.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972MNRAS.160..155S&db_key=AST