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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
| Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
| 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.
| Estimation of spectral classifications for bright northern stars with interesting Stromgren indices
The purpose of this investigation is to provide spectroscopic observerswith finding lists of potentially interesting objects. From anunpublished UVBY catalogue of 7026 northern stars (mostly brighter than8.3m) 1094 objects with interesting combinations of UVBY indices havebeen selected. Most stars with post-HD classifications have beenexcluded, as well as late F dwarfs belonging to the intermediatepopulation II. For the 792 remaining stars estimated spectralclassifications are given. The techniques and experience from a previouspaper dealing with southern stars have been utilized here. Among thepredicted spectral classifications are 40 OB stars; 262 Ap, Am, or Fmstars; 16 supergiants of types A to G; 110 bright giants of types A to K(class II); 156 double stars or objects with composite spectra; 26 lateF dwarfs; 91 weak-lined dwarf and giant stars of types F to K, includingearly F-type population II field blue stragglers; and a few possiblefield horizontal branch stars, lambda Bootis-type stars, and late-typehalo giants.
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| Takýmyýldýz: | Zurafa |
| Sað Açýklýk: | 04h23m34.69s |
| Yükselim: | +59°43'57.2" |
| Görünürdeki Parlaklýk: | 7.777 |
| Uzaklýk: | 390.625 parsek |
| özdevim Sað Açýklýk: | 2.7 |
| özdevim Yükselim: | -9.2 |
| B-T magnitude: | 8.464 |
| V-T magnitude: | 7.834 |
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