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Search for pulsation among suspected A-type binaries and the new multiperiodic δ Scuti star HD 217860
Context: In the H-R diagram, the intersection of the main sequence andthe classical Cepheid instability strip corresponds to a domain where arich variety of atmospheric phenomena are at play (including pulsation,radiative diffusion, convection). Main-sequence A-type stars are amongthe best candidates to study the complex interplay between these variousphenomena. Aims: We have explored a sample of suspected A-type binariesin a systematic way, both spectroscopically and photometrically. Thesample consists of main-sequence A-type stars for which the few existingradial velocity measurements may show variability, but for which otheressential information is lacking. Due to their location in the H-Rdiagram, indications of pulsation and/or chemical peculiarities amongthese suspected binary (or multiple) systems may be found. Methods:High-resolution spectroscopy obtained with the ELODIE and MUSICOSspectrographs was used in combination with a few nights of differentialCCD photometry in order to search for pulsation(s). In order to searchas well for chemical peculiarities or for possible hidden component(s),we derived the atmospheric stellar parameters by fitting the observedspectra with LTE synthetic ones. Results: Of the 32 investigatedtargets, eight are spectroscopic binaries, one of which is a closebinary also showing eclipses, and three have been identified as δScuti pulsators with rapid line-profile variations. Conclusions: Amongthe latter stars, HD 217860 reveals interesting multiperiodicphotometric and spectroscopic variations, with up to eight frequenciescommon to two large photometric data sets. We suggest that at least oneradial overtone mode is excited among the two most dominant frequencies,on the basis of the computation of the pulsation constants as well as ofthe predicted frequencies and the expected behaviour of the amplituderatio and the phase difference in two passbands using adequatetheoretical modelling. We furthermore found evidence for a strongmodulation of the amplitude(s) and/or the (radial) frequency content ofthis intriguing δ Scuti star.This work is based on spectroscopic observations made at theHaute-Provence Observatory (OHP), the Observatoire du Pic du Midi (TBL)and the Bulgarian National Astronomical Observatory (NAO, Rozhen).Tables 1, 2, 4, 5 and Fig. 7 are only available in electronic form athttp://www.aanda.org
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| 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
| Optical Line Profile Variability of the B1+Neutron Star Binary System LS I +65 010 (2S 0114+650)
We present high-resolution spectroscopic observations of the massiveX-ray binary system LS I +65 010 (2S 0114+650) in the optical wavelengthregion. A correlation between equivalent width and radial velocity ofphotospheric absorption lines is found. The systemic velocity, inferredfrom the weaker lines, is V[helio] -31+/-5kms-1, which, if attributedsolely to the Galactic rotation curve, implies that LS I +65 010 lieswithin 3 kpc from the Sun. The ISM Na I D lines display 2 resolved highvelocity components at V[helio] -70, -48kms-1, possibly associated withgas surrounding the binary system, in addition to the -24 and -8kms-1ISM features due to the Orion and Perseus arm regions, respectively.Strong photospheric line profile variability is present on anight-to-night timescale, with He I 5875 Å displaying anadditional blue-shifted absorption in some of the spectra, similar towhat is observed in the optical counterpart of Vela X-1. A connectionbetween the extended blue wing and X-ray maximum is suggested. Shorttimescale variations in line profiles are detected on only two nights,but the evidence that these variations occur on the 2.78 hour X-rayflaring period is marginal.
| Radial velocities, rotations, and duplicity of a sample of early F-type dwarfs
We present new radial and rotational velocities for 595 nearby early Fdwarfs, based on digital spectra cross-correlated with individuallyoptimised synthetic template spectra. The selection of optimumtemplates, the determination of rotational velocities, and theextraction of velocities from the blended spectra of double-linedspectroscopic binaries are discussed in some detail. We find 170spectroscopic binaries in the sample and determine orbits for 18double-lined and 2 single-lined binaries, including some spectroscopictriples. 73 stars are listed with too rapid rotation to yield usefulradial velocities (i.e. v sin i > 120 km~s^-1). We discuss the binaryfrequency in the sample, and the influence of unrecognised binaries onthe definition of clean metallicity groups of young F dwarfs and thedetermination of their kinematical properties. Tables 1, 5 and 6 areonly available, and Tables 2-4 also available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html.
| Stroemgren photometry of F- and G-type stars brighter than V = 9.6. I. UVBY photometry
Within the framework of a large photometric observing program, designedto investigate the Galaxy's structure and evolution, Hβ photometryis being made for about 9000 stars. As a by-product, supplementary uvbyphotometry has been made. The results are presented in a cataloguecontaining 6924 uvby observations of 6190 stars, all south ofδ=+38deg. The overall internal rms errors of one observation(transformed to the standard system) of a program star in the interval6.5
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Membre dels grups següents:
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Dades d'Observació i Astrometria
| Constel·lació: | Cetus |
| Ascensió Recta: | 01h16m59.81s |
| Declinació: | -17°05'12.5" |
| Magnitud Aparent: | 8.303 |
| Distancia: | 191.205 parsecs |
| Moviment propi RA: | -29.1 |
| Moviment propi Dec: | -31.1 |
| B-T magnitude: | 8.735 |
| V-T magnitude: | 8.339 |
Catàlegs i designacions:
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