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The chemical composition of δ Scuti*
We present chemical abundances in the photosphere of δ Scuti(δ Sct) - a prototype of the class of pulsating variables -determined from the analysis of a spectrum obtained by using the 2-mtelescope at the Peak Terskol Observatory and a high-resolutionspectrometer with R= 52000, a signal-to-noise ratio 250 and fromInternational Ultraviolet Explorer spectra. The abundance pattern ofδ Sct consists of 49 chemical elements. The abundances of 19elements have not been investigated previously. The abundances of Pr andNd obtained from the lines of the second and third spectra are equal.The abundances of heavy elements indicate the overabundances withrespect to the solar system values up to 1 dex. The abundance pattern ofδ Sct is similar to the abundance patterns of Am-Fm or δ Deltype stars.A splitting of the cores of all clean lines is observed for the spectraof δ Sct and HD 57749. This can signify evidence of non-radialpulsations in these stars.
| The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/989
| Asteroseismology of HADS stars: V974 Oph, a radial pulsator flavoured by nonradial components
The analysis of a dense time-series on V974 Oph disclosed the richpulsational content (at least five independent terms) of thishigh-amplitude (0.60 mag in B-light) delta Scts star. A mode with afrequency very close to the main one (probably the fundamental radialmode) has been detected: such a doublet is not a common feature in starsof the same class. Also another term can be considered a radial one, butthe high ratio (0.786) raises some problems that can be solved only byadmitting very low metallicity. It is quite evident that someundetectable terms are again hidden in the noise, as the least-squaresfit leaves a rms residual much higher than the observational noise. Allthat considered, nonradial modes seem to play a key rôle in thelight variability of V974 Oph. Revealing an unsuspected asteroseismicinterest, V974 Oph provides a link between low- and high-amplitude deltaScts stars.Based on observations collected at Europan Southern Observatory, LaSilla, Chile
| Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i
This 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
| Beryllium in F and G Field Dwarfs from High-Resolution Canada-France-Hawaii Telescope Spectra
It is important to add observations of Be to the huge arsenal of Liobservations in order to identify the mechanisms operating in stellarinteriors that alter the surface composition of the light elements.Beryllium is more resistant to destruction than is Li, so information onthe abundances of both Li and Be reveals more information on theinternal processes than either element does alone. We have madeobservations of Be II at 3131 Å in 46 solar-type stars from theCanada-France-Hawaii Telescope with high spectral resolution and highsignal-to-noise ratios (S/N). Our Li I 6707 Å data for 39 of thesestars come from our high-resolution, high-S/N observations with theUniversity of Hawai`i 88 inch (2.2 m) telescope and coudéspectrograph and Keck I High Resolution Echelle Spectrometer and, forsix stars, from the literature. Most of the stars in our sample are Fand G dwarfs with Teff between 6100 and 6600 K and with[Fe/H] between -0.6 and +0.2. The abundances of Be have been determinedthrough spectrum synthesis, while Li has been analyzed as a blend tofind the Li abundance. We find a large range in both Li and Be in thesestars; for Be it is at least 2.5 dex and for Li at least 3 dex. However,there is an excellent correlation between Li and Be, as discovered byDeliyannis et al. from a smaller sample. We find that in the range ofTeff of 5850 K (near the Li ``peak'' in open clusters) to6680 K (at the bottom of the Li ``gap'' as defined by the Hyades), Liand Be appear to be depleted together. The slope of this remarkablelogarithmic relation is 0.36: as Li is reduced by a factor of 10, Be isreduced by only 2.2 times. There is some scant evidence for a change inthe slope between the cooler stars and the hotter stars such that thecooler stars deplete more Li relative to Be than the hotter stars. Theseresults are well matched by models that incorporate rotationally inducedslow mixing of the stellar surface material with the deeper layers ofthe star.
| Radial and Nonradial Oscillations of 44 Tauri
Evolutionary stellar models of 44 Tauri, a multiperiodic δ Scutistar, have been developed theoretically and compared with earlierobservational reports. The models depict 44 Tau at thehydrogen-shell-burning stage, when it is in radiative equilibrium with avery thin surface convective layer. Using the models, we performedcalculations to obtain radial and nonradial adiabatic oscillationfrequencies, and the equations were treated linearly. The results showedthat the radial fundamental (6.899 cycles day-1) andfirst-overtone (8.961 cycles day-1) frequencies and the fivenonradial modes of low harmonic degree that had been determinedtheoretically were in agreement with the observed values of previousauthors to an accuracy of a few parts in 103. However, adifference emerged in the nonradial frequencies, which we classified asg-modes of low harmonic degree, whereas the observational reports hadclassified them as p-modes. In addition, even though 44 Tau has arotation vsini=6.8 km s-1 (according to Solano and Fernley),which we considered negligible, we analyzed the effect of rotation. Ourfindings revealed that rotation modulated the oscillation frequencies ofthe nonrotating model on the order of 10-2.
| The proper motions of fundamental stars. I. 1535 stars from the Basic FK5
A direct combination of the positions given in the HIPPARCOS cataloguewith astrometric ground-based catalogues having epochs later than 1939allows us to obtain new proper motions for the 1535 stars of the BasicFK5. The results are presented as the catalogue Proper Motions ofFundamental Stars (PMFS), Part I. The median precision of the propermotions is 0.5 mas/year for mu alpha cos delta and 0.7mas/year for mu delta . The non-linear motions of thephotocentres of a few hundred astrometric binaries are separated intotheir linear and elliptic motions. Since the PMFS proper motions do notinclude the information given by the proper motions from othercatalogues (HIPPARCOS, FK5, FK6, etc.) this catalogue can be used as anindependent source of the proper motions of the fundamental stars.Catalogue (Table 3) is only available at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strastg.fr/cgi-bin/qcat?J/A+A/365/222
| On the Variability of F1-F9 Luminosity Class III-V Stars
Hipparcos Satellite photometry of F1-F9 luminosity class III-V starsindicates that most are not particularly variable. A few stars for whichfurther study is desirable are identified.
| Abundances of C, N, O, and other elements in the atmospheres of the δ Scuti variables 14 Aur, δ Sct, and HD 127986
Using high-resolution spectra, we have determined the abundances ofcarbon (logε(C)), nitrogen (logε(N)), oxygen (logε(O)),silicon (logε(Si)), sulphur (logε(S)), and some other elementsfor three δ Scuti stars. Logε(C) for all three stars andlogε(N) for δ Sct and HD 127986 are close to the solarvalues, while there appears to be a slight (0.15 dex) nitrogendeficiency for 14 Aur. The logε(O) values correspond to a 0.30-dexdeficiency for 14 Aur and δ Sct and a 0.20-dex deficiency for HD127986. The values of logε(Si) for the three stars are close tosolar, and the logε(S) values indicate a slight deficiency (0.10dex) for 14 Aur and HD 127986 and a 0.20-dex excess for δ Sct.Comparison of the elemental abundances for seven δ Scuti starswith those for Am stars shows that the mean deficiencies of C, N, and Oare smaller for pulsating δ Scuti stars than for Am stars withsimilar effective temperatures. The sulphur abundances are virtually thesame for both types of stars.
| 71 Tauri: Hyades Enigma Resolved?
71 Tauri (HD 28052; F0 IV-V) is an enigmatic object for two reasons: (1)it is the second brightest X-ray source in the Hyades, yet early F starsas a rule are not strong coronal emitters; and (2) it lies a magnitudeabove the cluster main sequence, but radial velocity studies and speckleimaging suggest that it is single. Recently, long-slit ultravioletspectra of the star, obtained with the Space Telescope ImagingSpectrograph (STIS), serendipitously have revealed the presence of astellar companion at a distance of 0.1" directly south of the primary.The companion is seen only in its far-UV chromospheric emission lines.The nature of this object cannot be determined from our STIS spectraalone, but its high emission levels are most readily explained if it isa close binary of coronally active dG/dK stars. The presence of thesecondary can account for the striking X-ray properties of 71 Tau butnot its unusual location in the cluster color-magnitude diagram. It isconceivable that the primary itself is a close double of nearly equalstars, making 71 Tau a possible quadruple system. The alternative-that71 Tau is ~150 Myr older than other members of the Hyades, approachingthe end of core hydrogen burning for a 2 Msolar star-wouldchallenge the presumed synchrony of star formation in the cluster.
| A revised catalogue of delta Sct stars
An extensive and up-dated list of delta Sct stars is presented here.More than 500 papers, published during the last few years, have beenrevised and 341 new variables have been added to our last list, sixyears ago. This catalogue is intended to be a comprehensive review onthe observational characteristics of all the delta Sct stars known untilnow, including stars contained in earlier catalogues together with othernew discovered variables, covering information published until January2000. In summary, 636 variables, 1149 references and 182 individualnotes are presented in this new list. Tables 1 and 2 will be accessibleonly in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over more than twocenturies and summarized in the FK5. Part I of the FK6 (abbreviatedFK6(I)) contains 878 basic fundamental stars with direct solutions. Suchdirect solutions are appropriate for single stars or for objects whichcan be treated like single stars. From the 878 stars in Part I, we haveselected 340 objects as "astrometrically excellent stars", since theirinstantaneous proper motions and mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,199 of the stars in Part I are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives in addition to the SI mode the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(I) proper motion in the single-star mode is 0.35 mas/year. This isabout a factor of two better than the typical HIPPARCOS errors for thesestars of 0.67 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(I) proper motions have atypical mean error of 0.50 mas/year, which is by a factor of more than 4better than the corresponding error for the HIPPARCOS values of 2.21mas/year (cosmic errors included).
| A Second Catalog of Orbiting Astronomical Observatory 2 Filter Photometry: Ultraviolet Photometry of 614 Stars
Ultraviolet photometry from the Wisconsin Experiment Package on theOrbiting Astronomical Observatory 2 (OAO 2) is presented for 614 stars.Previously unpublished magnitudes from 12 filter bandpasses withwavelengths ranging from 1330 to 4250 Å have been placed on thewhite dwarf model atmosphere absolute flux scale. The fluxes wereconverted to magnitudes using V=0 for F(V)=3.46x10^-9 ergs cm^-2 s^-1Å^-1, or m_lambda=-2.5logF_lambda-21.15. This second catalogeffectively doubles the amount of OAO 2 photometry available in theliterature and includes many objects too bright to be observed withmodern space observatories.
| The ROSAT all-sky survey catalogue of optically bright main-sequence stars and subgiant stars
We present X-ray data for all main-sequence and subgiant stars ofspectral types A, F, G, and K and luminosity classes IV and V listed inthe Bright Star Catalogue that have been detected as X-ray sources inthe ROSAT all-sky survey; several stars without luminosity class arealso included. The catalogue contains 980 entries yielding an averagedetection rate of 32 percent. In addition to count rates, sourcedetection parameters, hardness ratios, and X-ray fluxes we also listX-ray luminosities derived from Hipparcos parallaxes. The catalogue isalso available in electronic form via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| CCD photometry of a delta Scuti variable in an open cluster. III. V 465 Persei in the alpha Persei cluster
We present the results of real-time CCD differential photometry for thedelta Scuti variable V 465 Per. The observations were performed forthirteen nights between November, 1994 and January, 1995. Total 3345points of differential V magnitudes were collected during theobservation period of 76.4 hours. From the Fourier analysis, we havedetected four frequencies as follows; f_1=14.040 c/d, f_2=17.208 c/d,f_3=33.259 c/d and f_4=13.721 c/d. Two frequencies of 12.50 c/d and33.49 c/d detected previously by Slovak (1978, ApJ 223, 192) maycorrespond to our f_1 and f_3, respectively. For each frequency,pulsation constants of Q_1=0.0520+/-0.008, Q_2=0.0425+/-0.006,Q_3=0.0220+/-0.003 and Q_4=0.0533+/-0.008 were derived from severalobservational properties of V 465 Per. Only the value of Q_3 is found tobe within the range of theoretical p-mode oscillations and the otherones show large differences relative to the theoretical values. The highQ-values might be interpreted as the occurrence of g-mode oscillationsin V 465 Per, even though it can not rule out the possibility ofsystematic errors (Breger 1990; Delta Scuti Star Newsletter, 2, 13)related to rotational velocity.
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| Amplitude variations of the multimode nonradial δ Scuti pulsator 4 CVn
New photoelectric photometry of the δ Scuti variable 4 CVn revealslong-term slow variations of multimode pulsational frequencies and theiramplitudes. We have confirmed 5(f1, f2,f3, f5, f7) of the 7 frequenciesidentified in the literature. Besides presenting the long-termvariations of the different amplitudes, we have found three newsuspected frequencies in the new data. Although Blazhko effect and moderesonance along with its coupling between different nonradial modesthrough interaction can be reasonably used to explain the observedchanges of periods and amplitudes, it should be carefully checked andanalyzed before RR Lyr-like light curve shape and new pulsation modescan be established with certainty.
| Systematic Errors in the FK5 Catalog as Derived from CCD Observations in the Extragalactic Reference Frame.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114..850S&db_key=AST
| Amplitude variations of the multimode nonradial delta Scuti pulsator 4 CVn.
Not Available
| A catalogue of [Fe/H] determinations: 1996 edition
A fifth Edition of the Catalogue of [Fe/H] determinations is presentedherewith. It contains 5946 determinations for 3247 stars, including 751stars in 84 associations, clusters or galaxies. The literature iscomplete up to December 1995. The 700 bibliographical referencescorrespond to [Fe/H] determinations obtained from high resolutionspectroscopic observations and detailed analyses, most of them carriedout with the help of model-atmospheres. The Catalogue is made up ofthree formatted files: File 1: field stars, File 2: stars in galacticassociations and clusters, and stars in SMC, LMC, M33, File 3: numberedlist of bibliographical references The three files are only available inelectronic form at the Centre de Donnees Stellaires in Strasbourg, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5), or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Spectroscopic survey of delta Scuti stars. I. Rotation velocities and effective temperatures
Projected rotational velocities and effective temperatures for 68 deltaSct stars as well as 41 non-variable stars of similar spectral type andluminosity are presented here. The rotational velocities have beencalculated following the method developed in \cite[Gray (1992)]{ref38}and effective temperatures have been derived using the Balmer lineprofiles. The temperatures obtained from this method are shown to be inreasonable agreement with those calculated using the Infrared FluxMethod (IRFM) or spectrophotometric methods. This result has allowed usto use our temperatures to compare different uvby beta photometriccalibrations. We find that the calibration given by \cite[Moon \&Dworetsky (1985)]{ref72} is the most consistent. In the second part ofthis paper we have studied the relation between the pulsationalproperties (periods and amplitudes) and the physical parameters (v sin iand Teff). Where pulsation modes have been determined, thelow amplitude $\delta$ Scutis tend to be multimode (radial andnon-radial) pulsators, consistent with the theory that non-linearcoupling between modes acts to limit the amplitude in these stars. Wehave compared the distribution of v sin i for low amplitude $\delta$Scutis and non-variable stars. This shows the $\delta$ Scutis have abroader distribution in v sin i suggesting that a high rotation velocitymay favour pulsation. We find that the large amplitude delta Scuti starstend to have longer periods, cooler temperatures and lower rotationvelocities. Given that the large amplitude stars are also relativelyrare all the above are consistent with the hypothesis that these starsare more evolved (sub-giants) than the low amplitude delta Scutis (mainsequence or early post-main sequence).
| Luminosity and related parameters of δ Scuti stars from HIPPARCOS parallaxes. General properties of luminosity.
The absolute magnitudes of δ Scuti stars derived from parallaxesmeasured by the Hipparcos astrometric satellite are discussed andcompared with the previous estimates based on photometric uvbyβindices. There are significant differences which are related tophotometric effects of metallicity and rotational velocity, but thepossible effect of a close companion on the measured apparent magnitudeshould be also taken into account. The possibility of differentgroupings of δ Scuti stars based on the absolute magnitudes isbriefly discussed. Some high amplitude δ Scuti stars withintermediate or normal metallicity and small and uncertain parallax haveapparently a very low luminosity; this could be a systematic effectrelated to the observational errors.
| ICCD Speckle Observations of Binary Stars.XV.An Investigation of Lunar Occultation Systems
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2260M&db_key=AST
| γ Doradus and δ Scuti stars: cousins or twins?
γ Doradus stars are a group of slowly pulsating early F dwarfswith typical low frequencies near 1c/d. The pulsation modes are probablyg modes. These stars are slightly cooler than the typical δ Scutivariables, which pulsate with higher frequencies of typically 10c/d(mostly nonradial p modes). This paper examines the relationship betweenthe two groups of variables. Additional low-frequency variability hasbeen reported for fewer than 10% of the 300 δ Scuti starsexamined. In at least one case (1 Mon), the observational data areconsistent with an alternate interpretation in terms of a modeinteraction, f_1_-f_2_, between two p modes of higher frequency, ratherthan by the excitation of g modes. In several other stars (e.g. 4 CVn),the reported low-frequency variability may originate in the comparisonstar used. Arguments are given that for a number of stars the observedlow-frequency variations are caused by observational errors (such asinstrumental drift and transparency variations). A few δ Scutistars remain for which intrinsic γ Doradus-type variability mayalready have been discovered, although no case is well-studied. One ofthe best candidates is the star BI CMi, which is situated in the smallregion of overlap of the two groups of pulsators in theHertzsprung-Russell diagram. The star deserves further study.
| The stability of the frequency content in the light curves of the δ Scuti stars HD16439=V663 Cassiopeiae, AZ Canis Minoris, HD 223480=BF Phoenicis.
Within the frame of the study of the pulsational behaviour of δSct stars, multicolour photometry of (previously) consideredmonoperiodic or double mode pulsators was undertaken. The frequencycontent of the light variation of SAO 4710=HD 16439=V663 Cas is clearlychanging as a new frequency, not present in 1989, was observed in 1995;a slight decrease is also observed in the amplitude of the dominantterm. The light curve of V663 Cas is now explained by three frequencies,but the residual noise probably masks other terms. SAO 231800=HD223480=BF Phe is confirmed to be a monoperiodic δ Sct star, butcomparing the 1989 and 1993 photometric measurements a strong reductionin the b amplitude is observed; on the other hand, the V amplituderemained stable in 1991 and 1993. The monoperiodic light curve of HR2989=AZ CMi seems more stable, giving only slight hints that smallchanges occurred. The different photometric behaviours of these starsare discussed, also by comparing them with other monoperiodic pulsators(β Cas, 28 And, τ Peg).
| CCD photometry of a δ Scuti variable in an open cluster: V650 Tau in the Pleiades.
Time resolved CCD differential photometry was carried out for theδ Scuti variable V650 Tau on fourteen nights between November andDecember, 1993(total 3707 points of differential B magnitudes duringabout 81 hours observation). By applying the Fourier analysis to theobserved data, we have detected five frequencies(f_1_=377.7μHz,f_2_=197.3μHz, f_3_=292.8μHz, f_4_=333.0μHz, f_5_=214.1μHz).Among these, the amplitudes of two frequencies, f_1_ and f_2_, show somedifferences from the preliminary results of STEPHI network(Michel et al.1995). The comparison of observed frequency ratios and pulsationconstants with theoretical ones suggests that V650 Tau may pulsatesimultaneously in two dominant radial(F, 3H) and three nonradial modes.
| Carbon, nitrogen, oxygen and other elements abundances in the atmospheres of the delta Scuti pulsating variables. III. V644 Her.
Not Available
| Main Sequence Variables
The pulsators along and near the main sequence are well-suited forasteroseismology and provide a probe of the stellar interior and itschanges with evolution. With the exception of rapidly oscillating Apstars (roAp), the pulsation periods range from 0.5 h to days. Thisrequires multisite campaigns lasting several weeks. The delta Scuti,roAp and beta Cephei variables offer the greatest potential, while thelonger-period g-mode pulsators (SPB -- slowly pulsating B stars -- andgamma Doradus variables) are very difficult to study. A summary of themultiperiod structure of delta Scuti stars is given. The twobest-studied stars, FG Vir and CD--24(deg) 7599, both have been WETtargets. A preliminary analysis of the 1995 campaign of FG Vir hasalready detected 19 frequencies. The standard photometric WET techniquehas a high duty cycle since the variable star is observed continuouslywith one channel. The study of main sequence variables requiresphotometric stability at low frequencies. The extension of the WETtechnique to low frequencies and its modification are discussed.
| Stability of frequency content in light curves of 44 Tauri
A CCD time series photometry was performed for 44 Tau, a multiperiodicdelta Scuti star. The light curves were obtained over 19 nights from1992 October to 1993 February. From the analysis of the data by means ofFourier transform and nonlinear least-squares fitting, the sevenfrequencies identified by Poretti et al. (1992) were derived. Theanalysis of the new data confirmed the existence of two very closefrequencies, 6.90 and 7.01 c/d; it was also found that the frequencycomponent of 9.56 c/d which was the seventh strongest one three yearsago, was strengthened to the third during the period of ourobservations. On the other hand, the frequency of 9.12 c/d which was thethird strongest component three years ago, appeared as the weakest onein our observations.
| 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.
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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | שור |
| התרוממות ימנית: | 04h10m49.90s |
| סירוב: | +26°28'51.0" |
| גודל גלוי: | 5.41 |
| מרחק: | 59.809 פארסק |
| תנועה נכונה: | -31.4 |
| תנועה נכונה: | -35.8 |
| B-T magnitude: | 5.78 |
| V-T magnitude: | 5.427 |
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