Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
A catalogue of eclipsing variables
A new catalogue of 6330 eclipsing variable stars is presented. Thecatalogue was developed from the General Catalogue of Variable Stars(GCVS) and its textual remarks by including recently publishedinformation about classification of 843 systems and making correspondingcorrections of GCVS data. The catalogue1 represents thelargest list of eclipsing binaries classified from observations.
| Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters
The availability of the Hipparcos Catalogue has triggered many kinematicand dynamical studies of the solar neighbourhood. Nevertheless, thosestudies generally lacked the third component of the space velocities,i.e., the radial velocities. This work presents the kinematic analysisof 5952 K and 739 M giants in the solar neighbourhood which includes forthe first time radial velocity data from a large survey performed withthe CORAVEL spectrovelocimeter. It also uses proper motions from theTycho-2 catalogue, which are expected to be more accurate than theHipparcos ones. An important by-product of this study is the observedfraction of only 5.7% of spectroscopic binaries among M giants ascompared to 13.7% for K giants. After excluding the binaries for whichno center-of-mass velocity could be estimated, 5311 K and 719 M giantsremain in the final sample. The UV-plane constructed from these datafor the stars with precise parallaxes (σπ/π≤20%) reveals a rich small-scale structure, with several clumpscorresponding to the Hercules stream, the Sirius moving group, and theHyades and Pleiades superclusters. A maximum-likelihood method, based ona Bayesian approach, has been applied to the data, in order to make fulluse of all the available stars (not only those with precise parallaxes)and to derive the kinematic properties of these subgroups. Isochrones inthe Hertzsprung-Russell diagram reveal a very wide range of ages forstars belonging to these groups. These groups are most probably relatedto the dynamical perturbation by transient spiral waves (as recentlymodelled by De Simone et al. \cite{Simone2004}) rather than to clusterremnants. A possible explanation for the presence of younggroup/clusters in the same area of the UV-plane is that they have beenput there by the spiral wave associated with their formation, while thekinematics of the older stars of our sample has also been disturbed bythe same wave. The emerging picture is thus one of dynamical streamspervading the solar neighbourhood and travelling in the Galaxy withsimilar space velocities. The term dynamical stream is more appropriatethan the traditional term supercluster since it involves stars ofdifferent ages, not born at the same place nor at the same time. Theposition of those streams in the UV-plane is responsible for the vertexdeviation of 16.2o ± 5.6o for the wholesample. Our study suggests that the vertex deviation for youngerpopulations could have the same dynamical origin. The underlyingvelocity ellipsoid, extracted by the maximum-likelihood method afterremoval of the streams, is not centered on the value commonly acceptedfor the radial antisolar motion: it is centered on < U > =-2.78±1.07 km s-1. However, the full data set(including the various streams) does yield the usual value for theradial solar motion, when properly accounting for the biases inherent tothis kind of analysis (namely, < U > = -10.25±0.15 kms-1). This discrepancy clearly raises the essential questionof how to derive the solar motion in the presence of dynamicalperturbations altering the kinematics of the solar neighbourhood: doesthere exist in the solar neighbourhood a subset of stars having no netradial motion which can be used as a reference against which to measurethe solar motion?Based on observations performed at the Swiss 1m-telescope at OHP,France, and on data from the ESA Hipparcos astrometry satellite.Full Table \ref{taba1} is 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/430/165}
| Spectroscopic binary orbits from photoelectric radial velocities. Paper 171: HD 152028 and HDE 284195 (GK Dra and V1094 Tau)
The two stars that form the subject of this paper are both short-perioddouble- lined eclipsing binaries having non-circular orbits despitetheir short periods. Although the HD type of HD 152028 is G0, theintegrated spectral type of the system must actually be much earlier:the B-V colour index is only about 0.37 mag and the parallax indicatesan integrated absolute magnitude as bright as +1.4 mag. A publishedphotometric investigation suggests that the primary star exhibits deltaScuti pulsations, with a period of 0.1138 days. That period is notpresent in the radial velocities, but we have identified a comparableperiodicity in the initially excessive residuals (sigma of the order of2 km/s) in the radial velocities of the primary star: there is anasymmetrical pulsational velocity curve with a semi-amplitude of about 3km/s and a period of 0.1178 days. HDE 284195 was not observed byHipparcos, but its HDE type of G0 is in reasonable agreement with itscolour and the nature of its radial-velocity traces. The rotations ofboth stars appear to be pseudo-synchronized to the orbit. The orbitalinclinations are not formally determined but they must be veryhigh,however and there is specific evidence that the inclination of HD152028 is very close to 90 degrees,so it is permissible to assume thatthe masses are scarcely above the minimum values, which in the case ofHD 152028 are 1.78 and 1.42 solar mass and in that of HDE 284195 are1.10 and 1.01 solar mass, with uncertainties below 1%.(ABRIDGED)
| HD 98116 (FO Leonis) - not an eclipsing binary
Not Available
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Aslan |
| Sað Açýklýk: | 11h17m25.13s |
| Yükselim: | +22°49'40.3" |
| Görünürdeki Parlaklýk: | 8.489 |
| Uzaklýk: | 495.05 parsek |
| özdevim Sað Açýklýk: | -15.5 |
| özdevim Yükselim: | -3.8 |
| B-T magnitude: | 10.583 |
| V-T magnitude: | 8.662 |
Kataloglar ve belirtme:
|
