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On the link between rotation, chromospheric activity and Li abundance in subgiant stars
The connection rotation-CaII emission flux-lithium abundance is analyzedfor a sample of bona fide subgiant stars, with evolutionary statusdetermined from HIPPARCOS trigonometric parallax measurements and fromthe Toulouse-Geneva code. The distribution of rotation and CaII emissionflux as a function of effective temperature shows a discontinuitylocated around the same spectral type, F8IV. Blueward of this spectraltype, subgiants have a large spread of values of rotation and CaII flux,whereas stars redward of F8IV show essentially low rotation and low CaIIflux. The strength of these declines depends on stellar mass. Theabundance of lithium also shows a sudden decrease. For subgiants withmass lower than about 1.2 Msun the decrease is located laterthan that in rotation and CaII flux, whereas for masses higher than 1.2Msun the decrease in lithium abundance is located around thespectral type F8IV. The discrepancy between the location of thediscontinuities of rotation and CaII emission flux and log n(Li) forstars with masses lower than 1.2 Msun seems to reflect thesensitivity of these phenomena to the mass of the convective envelope.The drop in rotation, which results mostly from a magnetic braking,requires an increase in the mass of the convective envelope less thanthat required for the decrease in log n(Li). The location of thediscontinuity in log n(Li) for stars with masses higher than 1.2Msun, in the same region of the discontinuities in rotationand CaII emission flux, may also be explained by the behavior of thedeepening of the convective envelope. The more massive the star is, theearlier is the increase of the convective envelope. In contrast to therelationship between rotation and CaII flux, which is fairly linear, therelationship between lithium abundance and rotation shows no cleartendency toward linear behavior. Similarly, no clear linear trend isobserved in the relationship between lithium abundance and CaII flux. Inspite of these facts, subgiants with high lithium content also have highrotation and high CaII emission flux.
| A catalog of rotational and radial velocities for evolved stars
Rotational and radial velocities have been measured for about 2000evolved stars of luminosity classes IV, III, II and Ib covering thespectral region F, G and K. The survey was carried out with the CORAVELspectrometer. The precision for the radial velocities is better than0.30 km s-1, whereas for the rotational velocity measurementsthe uncertainties are typically 1.0 km s-1 for subgiants andgiants and 2.0 km s-1 for class II giants and Ib supergiants.These data will add constraints to studies of the rotational behaviourof evolved stars as well as solid informations concerning the presenceof external rotational brakes, tidal interactions in evolved binarysystems and on the link between rotation, chemical abundance and stellaractivity. In this paper we present the rotational velocity v sin i andthe mean radial velocity for the stars of luminosity classes IV, III andII. Based on observations collected at the Haute--Provence Observatory,Saint--Michel, France and at the European Southern Observatory, LaSilla, Chile. Table \ref{tab5} also available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| 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.
| MK classification and photometry of stars used for time and latitude observations at Mizusawa and Washington
MK spectral classifications are given for 591 stars which are used fortime and latitude observations at Mizusawa and Washington. Theclassifications in the MK system were made by slit spectrograms ofdispersion 73 A/mm at H-gamma which were taken with the 91 cm reflectorat the Okayama Astrophysical Observatory. Photometric observations in UBV were made with the 1-meter reflector at the Flagstaff Station of U.S.Naval Observatory. The spectrum of HD 139216 was found to show a strongabsorption line of H-beta. The following new Am stars were found:HD9550, 25271, 32784, 57245, 71494, and 219109. The following new Apstars were found: HD6116, 143806, 166894, 185171, and 209260. The threestars, HD80492, 116204, and 211376, were found to show the emission inCaII H and K lines.
| ICCD speckle observations of binary stars. IV - Measurements during 1986-1988 from the Kitt Peak 4 M telescope
One thousand five hundred and fifty measurements of 1006 binary starsystems observed mostly during 1986 through mid-1988 by means of speckleinterferometry with the KPNO 4-m telescope are presented. Twenty-onesystems are directly resolved for the first time, including newcomponents to the cool supergiant Alpha Her A and the Pleiades shellstar Pleione. A continuing survey of The Bright Star Catalogue yieldedeight new binaries from 293 bright stars observed. Corrections tospeckle measures from the GSU/CHARA ICCD speckle camera previouslypublished are presented and discussed.
| MK spectral types for some F and G stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979PASP...91...83C&db_key=AST
| Star catalogs for the Washington and Richmond photographic zenith tubes.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973AJ.....78..642M&db_key=AST
| UBV Photometry of 173 PZT Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971PASP...83..177W&db_key=AST
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| Takýmyýldýz: | Coban |
| Sað Açýklýk: | 14h18m55.70s |
| Yükselim: | +38°46'03.0" |
| Görünürdeki Parlaklýk: | 6.86 |
| Uzaklýk: | 170.648 parsek |
| özdevim Sað Açýklýk: | 0.6 |
| özdevim Yükselim: | 26.6 |
| B-T magnitude: | 8.233 |
| V-T magnitude: | 6.985 |
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