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# HD 28204

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 Observed Orbital EccentricitiesFor 391 spectroscopic and visual binaries with known orbital elementsand having B0-F0 IV or V primaries, we collected the derivedeccentricities. As has been found by others, those binaries with periodsof a few days have been circularized. However, those with periods up toabout 1000 or more days show reduced eccentricities that asymptoticallyapproach a mean value of 0.5 for the longest periods. For those binarieswith periods greater than 1000 days their distribution of eccentricitiesis flat from 0 to nearly 1, indicating that in the formation of binariesthere is no preferential eccentricity. The binaries with intermediateperiods (10-100 days) lack highly eccentric orbits. Tidal Effects in Binaries of Various PeriodsWe found in the published literature the rotational velocities for 162B0-B9.5, 152 A0-A5, and 86 A6-F0 stars, all of luminosity classes V orIV, that are in spectroscopic or visual binaries with known orbitalelements. The data show that stars in binaries with periods of less thanabout 4 days have synchronized rotational and orbital motions. Stars inbinaries with periods of more than about 500 days have the samerotational velocities as single stars. However, the primaries inbinaries with periods of between 4 and 500 days have substantiallysmaller rotational velocities than single stars, implying that they havelost one-third to two-thirds of their angular momentum, presumablybecause of tidal interactions. The angular momentum losses increase withdecreasing binary separations or periods and increase with increasingage or decreasing mass. New periodic variables from the Hipparcos epoch photometryTwo selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcosunsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed. Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin iThis work is the second part of the set of measurements of v sin i forA-type stars, begun by Royer et al. (\cite{Ror_02a}). Spectra of 249 B8to F2-type stars brighter than V=7 have been collected at Observatoirede Haute-Provence (OHP). Fourier transforms of several line profiles inthe range 4200-4600 Å are used to derive v sin i from thefrequency of the first zero. Statistical analysis of the sampleindicates that measurement error mainly depends on v sin i and thisrelative error of the rotational velocity is found to be about 5% onaverage. The systematic shift with respect to standard values fromSlettebak et al. (\cite{Slk_75}), previously found in the first paper,is here confirmed. Comparisons with data from the literature agree withour findings: v sin i values from Slettebak et al. are underestimatedand the relation between both scales follows a linear law ensuremath vsin inew = 1.03 v sin iold+7.7. Finally, thesedata are combined with those from the previous paper (Royer et al.\cite{Ror_02a}), together with the catalogue of Abt & Morrell(\cite{AbtMol95}). The resulting sample includes some 2150 stars withhomogenized rotational velocities. Based on observations made atObservatoire de Haute Provence (CNRS), France. Tables \ref{results} and\ref{merging} are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/897 The nature of visual components in 82 multiple systems.Not Available On the HIPPARCOS photometry of chemically peculiar B, A, and F starsThe Hipparcos photometry of the Chemically Peculiar main sequence B, A,and F stars is examined for variability. Some non-magnetic CP stars,Mercury-Manganese and metallic-line stars, which according to canonicalwisdom should not be variable, may be variable and are identified forfurther study. Some potentially important magnetic CP stars are noted.Tables 1, 2, and 3 are available only in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html On the nature of the AM phenomenon or on a stabilization and the tidal mixing in binaries. II. Metallicity and pseudo-synchronization.We reveal sufficient evidences that for Am binaries the metallicitymight depend on their orbital periods, P_orb_, rather than on vsini. Inparticular, δm_1_ index seems to decrease with increasing orbitalperiod up to at least P_orb_=~50d, probably even up to P_orb_=~200d.This gives further support to our "tidal mixing + stabilization"hypothesis formulated in Part I. Moreover, while the most metallic Amstars seem to have rather large periods the slowest rotators are foundto exhibit substantially shorter P_orb_. A questioning eye is thus caston the generally adopted view that Am peculiarity is caused by asuppressed rotationally induced mixing in slowly rotating single'stars. The observed anticorrelation between rotation and metallicity mayhave also other than the `textbook' explanation, namely being the resultof the correlation between metallicity and orbital period, as themajority of Am binaries are possibly synchronized. We further argue thatthere is a tendency in Am binaries towards pseudo-synchronization up toP_orb_=~35d. This has, however, no serious impact on our conclusionsfrom Part I; on the contrary, they still hold even if this effect istaken into account. On the nature of the AM phenomenon or on a stabilization and the tidal mixing in binaries. I. Orbital periods and rotation.The paper casts a questioning eye on the unique role of the diffusiveparticle transport mechanism in explaining the Am phenomenon and arguesthat the so-called tidal effects might be of great importance incontrolling diffusion processes. A short period cutoff at =~1.2d as wellas a 180-800d gap were found in the orbital period distribution (OPD) ofAm binaries. The existence of the former can be ascribed to the state ofthe primaries with the almost-filled Roche lobes. The latter couldresult from the combined effects of the diffusion, tidal mixing andstabilization processes. Because the tidal mixing might surpassdiffusion in the binaries with the orbital periods P_orb_ less thanseveral hundred days and might thus sustain the He convection zone,which would otherwise disappear, no Am stars should lie below thisboundary. The fact that they are nevertheless seen there implies theexistence of some stabilization mechanism (as, e.g., that recentlyproposed by Tassoul & Tassoul 1992) for the binaries with orbitalperiods less than 180d. Further evidence is given to the fact that theOPD for the Am and the normal binaries with an A4-F1 primary arecomplementary to each other, from which it stems that Am stars are closeto the main sequence. There are, however, indications that they haveslightly larger radii (2.1-3 Rsun_) than expected for theirspectral type. The generally accepted rotational velocity cutoff at=~100km/s is shown to be of little value when applied on Am binaries ashere it is not a single quantity but, in fact, a function of P_orb_whose shape is strikingly similar to that of the curves of constantmetallicity as ascertained from observations. This also leads to thewell known overlap in rotational velocities of the normal and Am starsfor 402.5d.We have exploited this empirical cutoff function to calibrate thecorresponding turbulent diffusion coefficient associated with tidalmixing, having found out that the computed form of the lines of constantturbulence fits qualitatively the empirical shape of the curves ofconstant metallicity. As for larger orbital periods(20d55km/s found by Burkhart(1979) would then be nothing but a manifestation of insufficientlypopulated corresponding area of larger P_orb_. The Relation between Rotational Velocities and Spectral Peculiarities among A-Type StarsAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..135A&db_key=AST 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. Improved Mean Positions and Proper Motions for the 995 FK4 Sup Stars not Included in the FK5 ExtensionNot Available Carbon, nitrogen, and oxygen abundances in the chemically peculiar stars of the upper main sequenceLow-noise, high-resolution Reticon spectra are used to obtain C, N, andO abundances for chemically peculiar stars with surface temperaturesbetween 7,000 and 15,000 K. The analysis includes C I, C II, N I, and OI lines for 13 Am and related stars, nine Hg-Mn stars, 15 magnetic Apstars, and five standard stars. The C and O abundances show a roughlymonotonic increase with surface temperature. The C and O results are ingeneral agreement with radiative diffusion theory. The N abundances,however, show that N is slightly deficient in cool nonmagnetic stars andvery deficient above 10,000 K in nonmagnetic stars. The results for Ndisagree with simple diffusion predictions, suggesting that a moredetailed model is needed for partially ionized N near the stellarsurface. Third catalogue of AM stars with known spectral typesA catalogue has been compiled of Am stars with known spectral types withrespect to K-line, hydrogen-lines and metallic-lines. It contains 2269determinations for 1805 stars. UBV photometry of FK4 and FK4 supplement starsTraditional UBV filters, together with a photomultiplier, have been usedin 40-m Cassegrain telescope observations of all northern stars of theFK4 catalog and its supplement, which have heretofore lacked V and V-Bmeasurements. The resulting UBV photometry for 320 stars is presented intabular form. Lists of photometric AM candidatesThe 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 systemAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....92..289H&db_key=AST Seventh catalogue of the orbital elements of spectroscopic binary systems.Not Available Metallicism and pulsation - The marginal metallic line starsEvidence is presented that HR 4594 and HR 8210 are pulsating marginal Amstars. It is suggested that (1) classical Am stars do not pulsate, (2)evolved Am stars may pulsate, and (3) marginal Am stars may pulsate. Itis further suggested that, within the Am domain, temperature, age,rotation, and pulsation are sufficient to determine whether a star willbe Am, marginal Am, or spectrally normal. Statistical study of AM stars in spectroscopic binary systemsStatistics of spectroscopic binaries with Am spectra are analyzed. Thesystems considered include six double-line eclipsing binaries with knownphotometric elements, five single-line eclipsing binaries with knownmass functions, and 12 noneclipsing spectroscopic binaries with knowntrigonometric parallaxes larger than 0.020 arcsec. It is found that: (1)Am characteristics appear to be pronounced for a slightly evolved stagewith log g in the range from 3.8 to 4.2 and radii of 1.5 to 2.7 solarradii; (2) the helium content and mixing length are not uniform foratmospheres of Am stars; (3) synchronization between rotation andrevolution is characteristic of almost all Am binaries with orbitalperiods less than six days but depends on the stellar evolutionary agesfor Am binaries with orbital periods of six to ten days; and (4) themetallicity excess for Am spectroscopic binaries (including the effectof the secondary components) decreases significantly with the rotationalvelocity of the Am (primary) components. Bright metallic-line and pulsating A stars.Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976PASP...88..402E&db_key=AST Catalogue of early-type stars measured in a narrow-band photometric systemA compilation of the photoelectric measurements in the Barbier-Morguleffsystem is presented. The catalogue includes data for 773 stars ofspectral type 08 to F6. 706 stars have been measured at least twice. Multicolor photometry of metallic-line stars. III. A photometric catalogueAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974RMxAA...1..175M&db_key=AST Rotation and shell spectra among A-type dwarfs.Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973ApJ...182..809A&db_key=AST Catalogue of AM stars with known spectral typesAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&AS...10..385H&db_key=AST Rotational Velocities in Short-Period A-Type BinariesAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971ApJ...163..333A&db_key=AST Spectroscopic binaries with circular orbits.Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971AJ.....76..544L&db_key=AST Stellar kinematics and evolutionNot Available Classification des spectres de 112 d'étoiles A et F dont 89 d'étoiles AMAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&AS....1....7B&db_key=AST Spectral Classification of A-Type Spectroscopic BinariesAbstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969ApJ...158.1091A&db_key=AST Multicolor photoelectric photometry of the brighter planets. II. Observations from le Houga Observatory.Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73..251I&db_key=AST
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 Constellation: Giraffe Right ascension: 04h33m30.70s Declination: +72Â°31'43.0" Apparent magnitude: 5.94 Distance: 114.416 parsecs Proper motion RA: 30.1 Proper motion Dec: -90.4 B-T magnitude: 6.274 V-T magnitude: 5.964

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