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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.
| SB9: The ninth catalogue of spectroscopic binary orbits
The Ninth Catalogue of Spectroscopic Binary Orbits(http://sb9.astro.ulb.ac.be) continues the series of compilations ofspectroscopic orbits carried out over the past 35 years by Batten andcollaborators. As of 2004 May 1st, the new Catalogue holds orbits for2386 systems. Some essential differences between this catalogue and itspredecessors are outlined and three straightforward applications arepresented: (1) completeness assessment: period distribution of SB1s andSB2s; (2) shortest periods across the H-R diagram; (3)period-eccentricity relation.
| Contribution to the search of binaries among Am stars. II. HD 81976 and HD 98880, double-lined spectroscopic binaries
We present the results of the observations of two Am stars of eighthmagnitude, the double-lined spectroscopic binaries HD 81976 and HD98880, carried out with the CORAVEL instrument at the Observatoire deHaute-Provence in order to determine their orbital elements. We found 1)for HD 81976: P = 5.655750 days, T = 2449785.941 HJD, omega =341.4deg, e = 0.061, K1 = 61.68 km s-1,K2 = 63.84 km s-1, V0 = 19.85 kms-1, a1 sin i = 4.788 Gm, a2 sin i =4.956 Gm, M1 sin 3 i = 0.5875 Msun,M2 sin 3 i = 0.5676 Msun, and 2) for HD98880: P = 14.20783 days, T0 = 2448682.883 HJD (ascendingnode), e = 0., K1 = 42.47 km s-1, K2 =49.16 km s-1, V0 = 2.40 km s-1,a1 sin i = 8.298 Gm, a2 sin i = 9.604 Gm,M1 sin 3 i = 0.6091 Msun, M2sin 3 i = 0.5262 Msun. The first of these twosystems, HD 81976, is formed by two quasi-identical stars, and theHipparcos data (MV, B-V) are consistent with late A stars ineffective temperature; it is likely that the components rotatesynchronised with the orbital motion. A third body may be present inthis system since (i) the orbit has a significant eccentricity despiteits short period and (ii) the systemic velocity V0 shows apossible drift. For the second system, HD 98880, we give DeltamB 1.25 and we propose a simple model based uponStrömgren photometric indices and the HR theoretical diagram ofSchaller et al (1992) in addition to orbital parameters and Hipparcosdata: Teff = 7000 K, log 10 g = 4.0, M1= 1.9 Msun, M2 = 1.6 Msun, log10(age) = 9.12. The components do not rotate synchronouslycontrary to HD 81976. Both binaries appear to be detached systemswithout possibility of eclipses. Based on observations made at theHaute-Provence Observatory, France.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Miscellaneous spectroscopic notes
Results of slit-spectrograph observations are reported for approximately260 stars. The data presented range from recognition of many new Ap, Am,and other unusual stars to H-alpha observations of early-typesupergiants and Be stars. The material discussed was obtained over thepast 40 years at a number of U.S. observatories and at the DominionAstrophysical Observatory in Victoria, B.C.
| Catalog of Indidual Radial Velocities, 0h-12h, Measured by Astronomers of the Mount Wilson Observatory
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJS...19..387A&db_key=AST
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Pozíciós és asztrometriai adatok
| Csillagkép: | Kis Oroszlán |
| Rektaszcenzió: | 09h30m02.17s |
| Deklináció: | +33°18'21.2" |
| Vizuális fényesség: | 8.187 |
| Távolság: | 176.991 parszek |
| RA sajátmozgás: | -26.1 |
| Dec sajátmozgás: | -16.1 |
| B-T magnitude: | 8.503 |
| V-T magnitude: | 8.214 |
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