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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
| Near infrared light variations of chemically peculiar stars. The SrCrEu stars
Twenty magnetic Chemically Peculiar (CP2) stars of the SrCrEu subgroupmostly brighter than the 7.5 visual magnitude have been investigated inthe near infrared at 1.25, 1.6 and 2.2 mu . The stars HD 3980, HD 24712,HD 49976, HD 83368, HD 96616, HD 98088, HD 118022, HD 125248, HD 148898,HD 203006, and HD 220825 have been found to be variable in the infraredwith the same period as the visible light, spectrum, and magnetic fieldvariations. HD 221760 is also variable with a period of 12.45 days,which has to be confirmed. The stars HD 72968, HD 111133, HD 126515, HD153882, and HD 164258 do show some hint of variability, although thedata are too few. Infrared variability has been detected for the firsttime in the stars HD 101065, and HD 206088, which have not yet beenconsidered as variable. No variability has been detected for the star HD137949 within a time scale of the order of ten days. Based onobservations collected at the European Southern Observatory, La SillaChile.
| The light variations of some CP2 SrCrEu stars.
In the framework of a programme of checking the periods of chemicallypeculiar stars, eight southern stars have been observed in the uvbysystem. Seven stars have been previously known to be light variables,but for some stars the periods were not accurate enough to phasetogether different kinds of observations carried out several yearsapart. The periods of HD 83368, HD 98088, and HD 153882 are confirmed.For the stars HD 49976, HD 111133, HD 118022, and HD 164258 we presenthere more refined values of the period. No variability has been detectedfor the star HD 137949 within a time scale of the order of ten days.(The observations are available via ftp. 130.79.128.5 at the CDS).
| Red horizontal-branch stars in the galactic disk
A quantitative, three-dimensional spectral classification systemdeveloped by Rose (1984), which uses 2.5-A resolution spectra in theblue, has been used to identify a class of red horizontal branch (RHB)stars in the Galactic disk that are similar to those in the 'metal rich'globular cluster M 71. The RHB are denoted as evolved stars by their SrII 4077 line, and are distinguished from post-main sequence starsevolving through the same region of the HR diagram on the basis of theunique appearance of their CN 3883 and 4216 A bands. The RHB starsconsitute at least 5 percent of the entire giant branch population ofthe disk.
| Photoelectric filter photometry of the flux depression at 5200 A in Ap-stars
A new photometric index was used to characterize the flux depression at5200 A in a photoelectric filter photometric study of a large number ofnormal A-stars, Ap-stars, Am-stars, and Hg-Mn-stars. The new index isdefined as a = g - (h + y)/2, where g and h are the brightnesses at 5240and 5020 A, respectively, measured by interference filters, and y is thebrightness measured with a Stromgren filter. The index reveals a markedcontrast between normal and peculiar stars.
| On the variability of the peculiar A type star HD 49976.
Abstract image available at:http://adsabs.harvard.edu/abs/1975A&A....44..405M
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Observation and Astrometry data
| Constellation: | Monoceros |
| Right ascension: | 06h48m21.56s |
| Declination: | -07°45'16.6" |
| Apparent magnitude: | 6.881 |
| Distance: | 362.319 parsecs |
| Proper motion RA: | -3.6 |
| Proper motion Dec: | 3.2 |
| B-T magnitude: | 6.757 |
| V-T magnitude: | 6.871 |
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