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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Proper Motions of Faint Ultraviolet-bright Sources in the Sandage Two-Color Survey of the Galactic Plane
Proper motions with values >=10 or <=-10 mas yr-1 havebeen extracted from the USNO-B1.0 and Tycho-2 catalogs for all LanningUV-bright sources identified in the Sandage Two-Color Survey of theGalactic Plane and presented in Papers I-VI. Of the 572 sourcesexamined, we find at least 213 that exhibit a significantly large propermotion. Based on the location of the sources in a reduced proper motiondiagram, we demonstrate that about two-thirds of the high proper motionsources are likely or very likely to be heretofore unidentified whitedwarfs.
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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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A Finding List of Faint UV-Bright Stars in the Galactic Plane III
Sixty UV-bright objects have been found on three two-color 48-inchSchmidt plates as part of the continuing survey centered on the galacticplane. The sources identified range in U-B color from near U-B ~ 0 toU-B ~ -1.0, and in magnitude from m_B~10 to ~19. Some potentiallyinteresting sources are discussed, and finding charts are provided forall sources listed. Correlations with previously identified objects inthe literature are also noted. (SECTION: Stars)
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Mesures de vitesses radiales. VII. Accompagnement AU sol DU programme d'observation DU satellite Hipparcos. Radial velocities. VII. Ground based measurements for Hipparcos.
We publish 734 radial velocities of stars distributed in 28 fields of4x4deg. We continue the PPO series (Fehrenbach et al. 1987; Duflot etal. 1990 and 1992), using the Fehrenbach objective prism method.
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A finding list of faint UV-bright stars in the galactic plane, 2
Fifty-three UV-bright stars have been found on three two-color 48-in.Schmidt plates centered on the galactic plane. The sources detectedrange in U-B color from near U- B = 0 to U - B = -1.5, and in magnitudefrom mB approximately = 10 to approximately 21. Some of themore interesting sources are discussed, and finding charts are includedfor all sources listed. Additionally, follow-up spectroscopic andpostitional information is provided for several objects first listed inPaper I of this series. One new cataclysmic variable discovered duringthe course of this portion of the survey has been published previouslyand is discussed herein.
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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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UBVRI photometry of 225 AM stars
UBVRI photometry of 225 Am stars taken from Mendoza's (1974) catalog ispresented. The results are compared with those obtained by Feinstein(1974) for 21 of the stars and with the values of Johnson et al. (1966).It is assumed that in the first approximation the (V-I) color index ofan unreddened Am star is equal to that of a normal main-sequence star; astandard main sequence is defined for A and early F stars, and thefive-color photometry is analyzed by means of plots of U-V vs. V-I, B-Vvs. V-I, and V-R vs. V-I. Mean color deficiencies of Am stars areexamined, and it is suggested that an unreddened star located below themain-sequence A0-F2 line in the (V-I, U-V) plane is a photometric Amstar. It is concluded that: (1) photometric Am stars have colordeficiencies (as a function of V-I) which, on the average, are 0.07 magin (U-V) color index and 0.025 mag in (B-V) color index; (2) Am starswith V-R less than 0.25 mag may also have a color deficiency of about0.01 mag; (3) Am stars with V-R greater than 0.3 mag may have a colorexcess of approximately 0.01 mag; and (4) Am stars with V-R between 0.25and 0.3 mag may have normal colors.
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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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Catalogue et bibliographie des étoiles A à spectre particulier - Deuxième supplément
Not Available
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Catalogue et bibliographie des étoiles A à spectre particulier Premier supplément
Not Available
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Peculiar and Metallic-Line a - Stars in a Galactic Zone.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1959ApJ...129...88S&db_key=AST
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INHABITED SKY
