Tartalom
Képek
Kép feltöltése
DSS Images Other Images
Kapcsolódó cikkek
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
| Effective temperature scale and bolometric corrections from 2MASS photometry
We present a method to determine effective temperatures, angularsemi-diameters and bolometric corrections for population I and II FGKtype stars based on V and 2MASS IR photometry. Accurate calibration isaccomplished by using a sample of solar analogues, whose averagetemperature is assumed to be equal to the solar effective temperature of5777 K. By taking into account all possible sources of error we estimateassociated uncertainties to better than 1% in effective temperature andin the range 1.0-2.5% in angular semi-diameter for unreddened stars.Comparison of our new temperatures with other determinations extractedfrom the literature indicates, in general, remarkably good agreement.These results suggest that the effective temperaure scale of FGK starsis currently established with an accuracy better than 0.5%-1%. Theapplication of the method to a sample of 10 999 dwarfs in the Hipparcoscatalogue allows us to define temperature and bolometric correction (Kband) calibrations as a function of (V-K), [m/H] and log g. Bolometriccorrections in the V and K bands as a function of T_eff, [m/H] and log gare also given. We provide effective temperatures, angularsemi-diameters, radii and bolometric corrections in the V and K bandsfor the 10 999 FGK stars in our sample with the correspondinguncertainties.
| 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
| 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.
| Third preliminary catalogue of stars observed with the photoelectric astrolabe of the Beijing Astronomical Observatory.
Not Available
| Radial velocity measurements. I - Ground-based observations of the program stars for the HIPPARCOS satellite
The radial velocities of 272 stars brighter than m(pg) = 8.5 aredetermined by digital microphotometric measurement of plates obtainedwith dispersion 80 A/mm using the Marly slit spectrograph on the 120-cmtelescope of the Observatoire de Haute Provence. The objects wereselected as probable members of the input catalog for the ESA Hipparcosastrometric satellite. The measurement techniques and data-reductionprocedures are described in detail, and the results are presented inextensive tables and graphs and briefly characterized.
|
Új cikk hozzáadása
Kapcsolódó hivatkozások
- - (nincs kapcsolódó hivatkozás) -
Új link hozzáadása
Besorolás csoportokba:
|
Pozíciós és asztrometriai adatok
| Csillagkép: | Ikrek |
| Rektaszcenzió: | 07h57m32.62s |
| Deklináció: | +32°39'24.2" |
| Vizuális fényesség: | 7.131 |
| Távolság: | 116.144 parszek |
| RA sajátmozgás: | -38.9 |
| Dec sajátmozgás: | -15.1 |
| B-T magnitude: | 7.389 |
| V-T magnitude: | 7.153 |
Katalógusok és elnevezések:
|
