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A search for SB2 systems among selected Am binaries
We report on the detection of secondary spectra in five spectroscopicbinary systems: HD 434, HD 861, HD 108642, HD 178449, and HD 216608.High signal-to-noise high resolution spectroscopic observations werecarried out at the Bulgarian NAO Rozhen as part of an extended projectconcerned mainly with Am stars in binary systems. Our knowledge aboutearly type binaries has serious gaps. This is true especially when it isonly based on older photographic techniques. We concluded thatphotographic data involving longer orbital periods (where Doppler shiftsdue to the orbital motion are comparable or even less than therotational broadening of the spectral lines) and early type stars (thathave only a few and usually broad lines) should be revisited or at leastused with caution. We demonstrate that for the five systems how CCDobservations made with 2-m class telescopes can discover the binarynature or secondary spectra of many currently unresolved SB1 systems.Important astrophysical information such as the atmospheric parametersand the mass ratios are used to unravel previous misinterpretations ofthe data leading often to spurious orbits.
| Spectral Classification of Stars in A Supplement to the Bright Star Catalogue
MK spectral types are given for about 584 stars in A Supplement to theBright Star Catalogue. These are compared with Hipparcos parallaxes tocheck the reliability of those classifications. The estimated errors are+/-1.2 subtypes, and 10% of the luminosity classes may be wrong.
| Photometric and Spectroscopic Study of Stars in the Field of the Young Open Cluster Roslund 4
We present photometric and spectroscopic observations performed in thefield of the Galactic open cluster Roslund 4, which contains the twocataloged nebulae IC 4954 and IC 4955. UBVRI photometry was carried outin a field of 11'×6' around the clustercenter. Medium-resolution optical spectroscopy has been obtained for 41stars, including previously selected main-sequence and pre-main-sequencecandidate cluster members. Narrowband Hα, [S II], and continuumimages have been secured. The observations allow us the measurement ofdifferent physical parameters for the cluster. Assuming an absorptioncoefficient AV/E(B-V)=3.1 and a reddening slopeE(U-B)/E(B-V)=0.72, we obtain a color excess E(B-V)=1.1+/-0.2 and adistance modulus DM0=11.7+/-0.5. Fitting of isochrones to thecolor-magnitude diagrams gives logage(yr)=7.2+/-0.2, and thespectroscopic measurements provide the value VR=-15.7+/-5.2km s-1 for the heliocentric radial velocity. Among the 41stars with spectroscopic data, 11 stars are probable cluster members onthe basis of their radial velocity, and another 10 are considered aspossible members. Two probable member stars of spectral types A5 and G1show hints of absorption in the Li I 6708 Å line, with respectiveequivalent widths of 0.10 and 0.28 Å, and 22 stars of spectraltypes from B2 to G0 show different degrees of emission in Hα, [NII], and [S II] lines. With the exception of three stars of spectraltype earlier than A0, the emission of which is mainly photospheric, allother emissions seen in Hα and forbidden lines have a nebularorigin. They arise in an ionized cloud that surrounds the cluster and iscausing diffuse emission and, possibly, local variations in theextinction law from star to star. In addition to the stars, spectra ofseveral nebular condensations with relatively higher excitation havebeen analyzed. Two of them have been suggested to be Herbig-Haro (HH)objects. Our spectra indicate that only one of these condensations couldbe considered as an HH object.
| The Pul-3 catalogue of 58483 stars in the Tycho-2 system
A catalogue of positions and proper motions of 58483 stars (Pul-3) hasbeen constructed at the Pulkovo observatory. The Pul-3 is based on theresults of measurements of photographic plates with galaxies (Deutsch'splan). All plates were taken using the Pulkovo Normal Astrograph (thefirst epoch is in the 1950s and the second epoch is in the 1970s).The Pul-3 catalogue contains stars of mainly 12 to 16.5 mag in 146fields with galaxies in the declination zone from -5o to+85o. The Tycho-2 has been used as a reference catalogue.The mean epoch of the Pul-3 is 1963.25. The internal positional accuracyof the Pul-3 catalogue at the mean epoch of observations is ±80mas. The accuracy of the proper motions is mostly within ±3mas/yr to ±12 mas/yr. Comparisons of the Pul-3 with Tycho-2 andARIHIP have been done at the mean epoch of the Pul-3. The Pul-3 externalpositional accuracy relative to Tycho-2 is ±150 mas.The catalogue is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/357
| Direct Mass Ratio Determination in the SB2 Systems HD 108642 and HD 434
We confirm the presence of the secondary spectrum in two SB2 systems: HD108642 and HD 434. Lines of both components in both systems are clearlytravelling and crossing. This enabled us to improve the previous massratio estimate in the case of HD 108642 and to determine it for the fisttime in HD 434.
| Discovery of a Secondary Spectrum in the SB1 System HD 434
We report detection of the secondary spectrum in the former SB1 systemHD 434. Both components exhibit pronounced Am anomalies. Their rotationis probably synchronized in spite of relatively long orbital period.
| 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
| 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_.
| 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.
| A search for radio emission from the 'nonmagnetic' chemically peculiar stars
We have observed 23 members of the Am and HgMn subclasses of chemicallypeculiar (CP) stars with the Very Large Array (VLA) to search fornonthermal radio emission at levels comparable to those found for the Siand He peculiar subclasses of the CP stars by Linsky et al. (1992). Thisstudy was motivated by recent claims that magnetic fields of kilogaussstrength are present in at least some of the Am and HgMn stars, contraryto previous beliefs, which would indicate that radio-emittingmagnetospheres could be present in these stars. We detected none of theAm and HgMn stars as radio emitters with upper limits typically lessthan 0.20 mJy. Applying a correlation between radio luminosity, surfacemagnetic field, and effective temperature derived from previous radiostudies of the Si and He peculiar CP stars, we find that the predictedradio luminosities of alpha And (an HgMn star) and Sirius (a hot Amstar) are more than an order of magnitude larger than the observed upperlimits, indicating that these stars lack magnetospheres, and, byinference, surface magnetic fields.
| Spectroscopic study of the strontium AM binaries HD 434 and 41 Sex A
Improved spectroscopic orbital elements of the single-line Am binary HD434 are presented, and cover large gaps in the radial velocity curveobtained earlier by Hube and Gulliver (1985). The MK morphology of thespectrum of HD 434 is examined, and the classification of its metallicline types in the violet and blue regions, along with its revised K- andH-line spectral types, are given for the first time. The strontiumanomaly in its spectrum is discussed. 41 Sex A is found to be aprototype of an Am star exhibiting transitional characteristics, formingan evolutionary link between Ap and Am groups of CP stars. Itsspectroscopic orbital elements are confirmed using our own velocities.The MK morphology of its spectrum and its spectral line behavior,especially that of the Sr II 4077 line, are briefly discussed.
| Spectroscopic orbits of AM stars. I - Seven field stars
New spectroscopic observations for a first sample of seven field Amstars are presented. The derived radial velocities are used to improvetheir spectroscopic orbits. The star HD 23848 (42 Per) is identified asa new mild Am star.
| Ultraviolet Observations with the Space Telescope Glazar
Not Available
| Spectroscopic binaries - 15th complementary catalog
Published observational data on the orbital characteristics of 436spectroscopic binaries, covering the period 1982-1986, are compiled intables. The data sources and the organization of the catalog are brieflydiscussed, and notes are provided for each item.
| Preliminary orbital elements for the AM binary HD 434
Preliminary spectroscopic orbital elements are presented for themetallic-lined A-star HD 434. Most of the orbital elements are basedonly on data obtained during the past eight years, but a few radialvelocities measured more than 4 decades earlier have contributed to thereliable determination of an orbital period of 34.26014 d. The systemhas the moderately large mass function of 0.122 solar mass.
| 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
| Apparent radii and other parameters for 416 B5 V-F5 V stars of the catalogue of the Geneva Observatory
Apparent radius, visual brightness, effective temperature and absoluteradius for 416 B5 v-F5 v stars of the catalogue of the GenevaObservatory (Rufener, 1976) have been determined. Twenty-eight stars,anomalous in log a" versus (m~)o diagrams, have been singled out. A goodcorrelation for seven stars, in common with the list of Hanbury Brown etal. (1974), has been found. Similar parameters determined for 279 B5v-F5 v stars of two preceding papers (Fracassini et al., 1973, 1975)have allowed us to determine the averaged diagrams , and versus (B -V)0 for 695 B5 v-F5 v stars. Moreover, in the present paper a goodcorrelation versus and carefulrelation = -7.40 + 3.31 for B5v-F5 V stars have been determined. Plain correlations between log R/R0and blanketing parameter m2 for some spectral types seem to point outthat there are real differences in the absolute radii of stars of thesame spectral type, in agreement with recent researches on the HRdiagram (Houck and Fesen, 1978). Systematic differences between double(spectroscopic and visual) and single stars are found. In particular,the averaged relation versus shows that A2v-F5 v double stars may have a higher metallicity index m2 and smallerabsolute radii than single stars. Finally, the diagram log v sin iversus log R/R0 confirms some properties of binary systems found byother researchers (Huang, 1966; Plavec, 1970; Levato, 1974; Kitamura andKondo, 1978)
| 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
| 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
| Photometric investigations of magnetic stars.
Abstract image available at:http://adsabs.harvard.edu/abs/1973A&A....22..209S
| 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
| List of newly identified matallic line A stars
Not Available
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לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | פגסוס |
| התרוממות ימנית: | 00h09m00.16s |
| סירוב: | +28°14'51.1" |
| גודל גלוי: | 6.472 |
| מרחק: | 115.607 פארסק |
| תנועה נכונה: | 4.9 |
| תנועה נכונה: | -7.1 |
| B-T magnitude: | 6.758 |
| V-T magnitude: | 6.496 |
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