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MOST Detects SPBe Pulsations in HD 127756 and HD 217543: Asteroseismic Rotation Rates Independent of vsini
The MOST (Microvariability and Oscillations of Stars ) satellite hasdiscovered SPBe (slowly pulsating Be) oscillations in the stars HD127756 (B1/B2 Vne) and HD 217543 (B3 Vpe). For HD 127756, 30 significantfrequencies are identified from 31 days of nearly continuous photometry;for HD 217543, up to 40 significant frequencies from 26 days of data. Inboth cases, the oscillations fall into three distinct frequency ranges,consistent with models of the stars. The variations are caused bynonradial g-modes (and possibly r-modes) distorted by rapid rotation andexcited by the opacity mechanism near the iron opacity bump. Acomparison of pulsation models and observed frequency groups yields arotation frequency for each star, independently of vsini. The rotationrates of these stars, as well as those of the SPBe stars previouslydiscovered by MOST, HD 163868 and ? CMi, are all close to theircritical values.Based on data from the MOST satellite, a Canadian Space Agency mission,jointly operated by Dynacon, Inc., the University of Toronto Instituteof Aerospace Studies, and the University of British Columbia with theassistance of the University of Vienna.
| β Cephei stars in the ASAS-3 data. II. 103 new β Cephei stars and a discussion of low-frequency modes
Context: The β Cephei stars have been studied for over a hundredyears. Despite this, many interesting problems related to this class ofvariable stars remain unsolved. Fortunately, these stars seem to bewell-suited to asteroseismology. Hence, the results of seismic analysisof β Cephei stars should help us to better understand pulsationsand the main sequence evolution of massive stars, particularly theeffect of rotation on mode excitation and internal structure. It istherefore extremely important to increase the sample of known βCephei stars and select targets that are useful for asteroseismology. Aims: We analysed ASAS-3 photometry of bright early-type stars with thegoal of finding new β Cephei stars. We were particularly interestedin β Cephei stars that would be good for seismic analysis, i.e.,stars that (i) have a large number of excited modes; (ii) showrotationally split modes; (iii) are components of eclipsing binarysystems; (iv) have low-frequency modes, that is, are hybrid βCephei/SPB stars. Methods: Our study was made with a homogeneous sampleof over 4100 stars having MK spectral type B5 or earlier. For thesestars, the ASAS-3 photometry was analysed by means of a Fourierperiodogram. Results: We have discovered 103 β Cephei stars,nearly doubling the number of previously known stars of this type. Amongthese stars, four are components of eclipsing binaries, seven have modesequidistant or nearly equidistant in frequency. In addition, we foundfive β Cephei stars that show low-frequency periodic variations,very likely due to pulsations. We therefore regard them as candidatehybrid β Cephei/SPB pulsators. All these stars are potentially veryuseful for seismic modeling. Moreover, we found β Cephei-typepulsations in three late O-type stars and fast period changes in one, HD168050.Table 2 and Figs. 2-14 are only available in electronic form athttp://www.aanda.org The V photometry for all 103 stars is available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/477/917
| Multiperiodicity in the newly discovered mid-late Be star V2104?Cygni
Aims:We obtained the first long, homogenous time-series of V2104 Cyg,consisting of 679 datapoints, with the uvby? photometers of theSierra Nevada and San Pedro Mártir Observatories. Our aim was todetect and subsequently interpret the intrinsic frequencies of thispreviously unstudied variable star, which turned out to be a Be star. Weevaluate its place among the variable B stars on the upper MainSequence. To obtain additional information on physical parameters wecollected a few spectra with the Elodie and FIES instruments. Methods: We searched for frequencies in the uvby passbands using 2different frequency analysis methods and used the S/N > 4 criterionto select the significant periodicities. We obtained an estimate of thephysical parameters of the underlying B star of spectral type between B5and B7, by correcting for the presence of a circumstellar disk using aformalism based on the strength of the H? line emission. Results: We detected 3 independent frequencies with amplitudes below0.01 mag, ?1 = 4.7126 d-1 , ?2 =2.2342 d-1 and ?3 = 4.671 d-1 , anddiscovered that V2104 Cyg is a Be star. The fast rotation (vsin i =290±10 km s-1, and 27°< i < 45°)hampered the investigation of the associated pulsational parameters ell.Conclusions: The most plausible explanation for the observedvariability of this mid-late type Be star is a non-radial pulsationmodel.Based on observations obtained at the Observatorio AstronómicoNacional San Pedro Mártir (Mexico), Observatorio de Sierra Nevada(Spain) and Observatoire de Haute Provence (France), and on observationsmade with the Nordic Optical Telescope, operated on the island of LaPalma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in theSpanish Observatorio del Roque de los Muchachos of the Instituto deAstrofísica de Canarias. Full Fig. 1 is only available inelectronic form at http://www.aanda.org
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| 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 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| UvbyHbeta_ photometry of main sequence A type stars.
We present Stroemgren uvby and Hbeta_ photometry for a set of575 northern main sequence A type stars, most of them belonging to theHipparcos Input Catalogue, with V from 5mag to 10mag and with knownradial velocities. These observations enlarge the catalogue we began tocompile some years ago to more than 1500 stars. Our catalogue includeskinematic and astrophysical data for each star. Our future goal is toperform an accurate analysis of the kinematical behaviour of these starsin the solar neighbourhood.
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Pozíciós és asztrometriai adatok
| Csillagkép: | Hattyú |
| Rektaszcenzió: | 20h01m45.54s |
| Deklináció: | +57°39'06.5" |
| Vizuális fényesség: | 7.677 |
| Távolság: | 617.284 parszek |
| RA sajátmozgás: | 4.5 |
| Dec sajátmozgás: | 5.4 |
| B-T magnitude: | 7.625 |
| V-T magnitude: | 7.673 |
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