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.
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Pulkovo compilation of radial velocities for 35495 stars in a common system.
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Statistics of multiple stars
The statistics of stellar systems of multiplicity three and higher isreviewed. They are frequent, 0.15-0.25 of all stellar systems. Some 700multiples are expected among the 3383 stars of spectral type F, G, and Kwithin 50 pc, while only 76 of them are actually known. Many (if notall) close binaries have distant tertiary components, indicating thatangular momentum exchange within multiple systems was probably criticalin forming short-period binaries. The ratio of outer to inner periods inthe best-studied nearby multiples and in low-mass pre-main sequencemultiples does not exceed 104 at the formation epoch; largerratios are produced by subsequent orbital evolution. All multiples withwell-defined orbits are dynamically stable, the eccentricities of outerorbits obey the empirical stability limit P[out](1 - e[out])3/P[in] >5 that is more strict than current theoretical limits. Relativeorientation of orbits in triple stars shows some degree of alignment,especially in weakly-hierarchical systems. The statistics support theidea that most multiple stars originated from dynamical interactions insmall clusters.
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Contribution to the search for binaries among Am stars - III. HD 7119: a double-lined spectroscopic binary and a triple system
Radial velocity observations of HD 7119 with the CORAVEL instrument atObservatoire de Haute-Provence are reported. Known as anAmδδ Del metallic-line star, HD 7119 was included in ourspectroscopic survey of Am-type stars, the purpose of which was todetermine the frequency of binaries in this stellar family. This objectis found to be a double-lined spectroscopic binary with a variable valueof V0, the systematic velocity of the centre of gravity ofthe pair. The variation of this parameter is interpreted in terms of theorbital motion of an unseen third body with a much longer period. Theorbital elements were derived for both the short- and the long-periodorbits. These orbits can be considered to be well determined since theseobservations were performed on a regular basis over the 1992-1998period, covering more than 320 orbital cycles for the short-period (P=6.76 d) and 1.3 cycle for the long-period orbit (P~ 1700 d). As deducedfrom the ratio of the correlation dip areas, the magnitude difference ofthe components of the short-period system is 0.7 mag. Combined with theHipparcos data, this value leads to visual absolute magnitudes of 0.5and 1.2 for the primary and secondary components, respectively. Suchmagnitudes are consistent with evolved δ Del-type stars. The thirdbody could be a cool dwarf star with a minimum mass of 0.5Msolar, located at ~ 0.016 arcsec of the main system.Consequently, it cannot be the visual companion detected by Couteau witha separation of 3.35 arcsec. If this latter visual component were aphysical component (rather than an optical one), HD 7119 would be aquadruple system.
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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
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The Program to Link the HIPPARCOS Reference Frame to an Extragalactic Reference System Using the Fine Guidance Sensors of the Hubble Space Telescope
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.2796H&db_key=AST
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Mesures de vitesses radiales. VIII. Accompagnement AU sol DU programme d'observation DU satellite HIPPARCOS
We publish 1879 radial velocities of stars distributed in 105 fields of4^{\circ} \times 4^{\circ}. We continue the PPO series \cite[(Fehrenbachet al. 1987;]{Feh87} \cite[Duflot et al. 1990, 1992 and 1995),]{Du90}using the Fehrenbach objective prism method. Table 1 only available inelectronic form at CDS via to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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Mesures et decouvertes d'etoiles doubles effectuees a la lunette de 50cm de l'Observatoire de Nice. Measures and discoveries of visual double stars made with the 50cm refractor at the Nice Observatory.
Measures and discoveries of visual double stars made at the Observatoirede la Cote d'Azur at Nice, between 1988 and 1994, with the 50cmrefractor equipped with a filar micrometer and electronic recordingdevice. The programs proposed by J. Dommanget involve the complement ofthe C.C.D.M. (resolving problems of identification of double stars andof coherency in the Index) and the INput CAtalog Hipparcos (resolutionof ambiguities on the binarity and on the position of certain doublestars which have seldom or never been observed again from the epoch ortheir discovery). The author has discovered three new binaries: JCT1,JCT2 and JCT3.
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HD 7119: a Probable New Pulsating delta Delphini Star
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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.
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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
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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
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Catalogue of AM stars with known spectral types
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&AS...10..385H&db_key=AST
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Classification des spectres de 112 d'étoiles A et F dont 89 d'étoiles AM
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&AS....1....7B&db_key=AST
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Etoiles doubles nouvelles (3e serie) decouvertes a Nice avec la lunette de 50 centimetres.
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Slit Spectra of Some Peculiar and Metallic-Line A Stars
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INHABITED SKY
