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Abundance analysis of prime B-type targets for asteroseismology. II. B6-B9.5 stars in the field of view of the CoRoT satellite
Context: Aims: The main goal of the ground-based seismologysupport program for the CoRoT mission was to obtain photometric andspectroscopic data for stars in the fields monitored by the satellite.These ground-based observations were collected in the GAUDI archive.High-resolution spectra of more than 200 B-type stars are available inthis database, and about 45% of them is analysed here. Methods:To derive the effective temperature of the stars, we used photometricindices. Surface gravities were obtained by comparing observed andtheoretical Balmer line profiles. To determine the chemical abundancesand rotational velocities, we used a spectrum synthesis method, whichconsisted of comparing the observed spectrum with theoretical ones basedon the assumption of LTE. Results: Atmospheric parameters,chemical abundances, and rotational velocities were determined for 89late-B stars. The dominant species in their spectra are iron-peakelements. The average Fe abundance is 7.24 ± 0.45 dex. Theaverage rotational velocity is 126 km s-1, but there are 13and 20 stars with low and moderate V sin i values, respectively. Theanalysis of this sample of 89 late B-type stars reveals many chemicallypeculiar (CP) stars. Some of them were previously known, but at least 9new CP candidates, among which at least two HgMn stars, are identifiedin our study. These CP stars as a group exhibit V sin i values lowerthan the stars with normal surface chemical composition.Atmospheric parameters and abundance analysis results are only 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/506/213 The CoRoT spacemission was developed and is operated by the French space agency CNES,with participation of ESA's RSSD and Science Programmes, Austria,Belgium, Brazil, Germany, and Spain. Tables [see full textsee full text]and [see full textsee full text] are only available in electronic format http://www.aanda.org
| A Search for Star Clusters from the HIPPARCOS Data
We present results of a search for nearby star clusters and associationsusing Hipparcos Catalogue data, restricting the sample to stars withparallaxes above 2 mas (d <~ 500 pc). Two new OB associations havebeen identified in the Carina-Vela and Cepheus-Cygnus-Lyra-Vulpecularegions. A very probable new open cluster has been discovered in Carina.The cluster, a Car, named after its brightest member, is young (60 Myr)and nearby (d = 132 pc). However, only seven bona fide members can bedrawn from the Hipparcos data. We report a detection of nine opencluster candidates in the distance range of 150 to 400 pc, and sixpossible associations almost all located within the Gould belt, althoughslightly older than the known nearby associations. In all cases, wepresent Yale theoretical isochrone fits to the color-magnitude diagrams,which indicate a moderate spread of ages between 60 to 200 Myr.Evidently, these young open cluster and association candidates arerelated to the overall distribution of young OB and A-type stars in thesolar neighborhood.
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Datos observacionales y astrométricos
| Constelación: | Unicornio |
| Ascensión Recta: | 06h54m18.78s |
| Declinación: | -06°23'21.3" |
| Magnitud Aparente: | 7.27 |
| Distancia: | 185.529 parsecs |
| Movimiento Propio en Ascensión Recta: | -7.3 |
| Movimiento Propio en Declinación: | -2.4 |
| B-T magnitude: | 7.169 |
| V-T magnitude: | 7.262 |
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