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Contribution to the search for binaries among Am stars - VIII. New spectroscopic orbits of eight systems and statistical study of a sample of 91 Am stars
This paper is the last of a series devoted to the study of Am stars,with the monitoring of radial velocities of a sample of 91 objectsduring more than 20 yr. The purpose was to determine which stars weremembers of spectroscopic binaries (SBs) and study in detail thosesystems in order to obtain observational constraints on the origin ofthe Am phenomenon.In the first part, we present the results of a detailed study of eightAm stars (HD 32893, 60489, 109762, 111057, 113697, 204918, 219675 andBD+44° 4512) observed at the Haute-Provence and Cambridgeobservatories with CORAVEL instruments. We find that these objects aresingle-lined SBs whose orbital elements are determined for the firsttime. HD 32893 is found to be a triple spectroscopic system whose thirdbody might be detected by speckle interferometry. Physical parametersare inferred for the primaries of those SBs. We then investigate theinfluence of tidal interaction and find that it has already led to thesynchronism of the primaries and to the circularization of the orbits offour of those systems.In the second part of this paper, we present the main results of ourwhole programme and derive some statistical properties of Am stars. Wegive the recapitulating table of the orbital parameters found for theSBs of our whole sample and the list of those for which no evidence forradial velocity variations could be found during our monitoring. Ourstudy shows that at least 64 per cent of Am stars are members of SBs.This rate is significantly greater than that of normal stars. Althoughsome SBs may have been not detected, this study shows that a substantialfraction of Am stars do not belong to SBs: they are either isolatedstars or members of wide binary systems.We then present some statistical properties of the orbital parameters ofthe SBs whose primary is an Am star, on an extended sample obtained byadding 29 Am SB orbits published by other authors. The corresponding eversus logP diagram shows a cut-off between the circular and theeccentric systems at P ~ 5.6 +/- 0.5 d, which indicates a typical age of0.5 - 1 × 109 yr for the Am stars, which is inagreement with the values found in our previous detailed studies. AMonte Carlo analysis shows that the distribution of the mass functionvalues f(m) is compatible with a power-law distribution N(m) ~m-α of the masses m of the companions with α =0.3 +/- 0.2 or with a Gaussian distribution centred on 0.8 +/-0.5Msolar, which indicates that the companions of Am SBs aremostly dwarf stars of type G-K-M.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| The Naini Tal - Cape survey for pulsations in chemically peculiar A-type stars. I. Methods and preliminary results
A new survey for pulsating, chemically peculiar A- and F-type stars inthe northern hemisphere has been initiated using the 1-m telescope atUttar Pradesh State Observatory in Naini Tal. The survey is primarilystructured to reveal high-overtone pulsations in chemically peculiar A-Fstars, but it is also revealing low-overtone delta Scuti-type pulsationsin stars with peculiar colours. This paper describes the scope andmethods of the survey. Preliminary observations of 28 candidate starsare presented and the discovery of three new pulsators, HD 12098, HD13038 and HD 13079, is announced. Null results for the remaining 25stars are also discussed.
| 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
| Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
| Lists of photometric AM candidates
The Geneva photometric m parameter (Nicolet and Cramer, 1982) is used inorder to select Am photometric candidates from the Rufener (1981)catalogue. Two lists are given, the first containing field stars and thesecond cluster stars. According to the photometric criteria thediffusion process probably responsible for the Am phenomenon takes placerather quickly as Am candidates are present in young clusters. It isconfirmed that the phenomenon is enhanced by low rotational velocity andhigh metallicity. The age seems to slightly affect the Am phenomenon.
| Properties of AM stars in the Geneva photometric system
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....92..289H&db_key=AST
| A spectrophotometric survey of stars along the Milky Way. IV
In the present paper a catalogue of spectrophotometric quantities,spectral types, monochromatic magnitudes and colour equivalents is givenfor all stars brighter than the magnitude m4400 = 10.5 in aregion of the Milky Way in Perseus. No absorption is found for starscloser than about r = 100 pc. The absorbing clouds are situated atdistances closer than 1 kpc and at about 2.5 kpc in the local arm andthe Perseus arm, respectively. The space between the two arms is freefrom absorption. It is also concluded that the Perseus arm continuesbeyond l = 140 deg, containing not only hydrogen gas but also dust to atleast l = 150 deg), while the content of OB stars decreases abruptly atl = 140 deg.
| Classification spectrale d'etoiles AP et Am.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975A&AS...21...25F&db_key=AST
| Multicolor photometry of metallic-line stars. III. A photometric catalogue
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974RMxAA...1..175M&db_key=AST
| Slit Spectra of Some Peculiar and Metallic-Line A Stars
Not Available
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