Tartalom
Képek
Kép feltöltése
DSS Images Other Images
Kapcsolódó cikkek
The N2K Consortium. VII. Atmospheric Parameters of 1907 Metal-rich Stars: Finding Planet-Search Targets
We report high-precision atmospheric parameters for 1907 stars in theN2K low-resolution spectroscopic survey, designed to identify metal-richFGK dwarfs likely to harbor detectable planets. Of these stars, 284 arein the ideal temperature range for planet searches,Teff<=6000 K, and have a 10% or greater probability ofhosting planets based on their metallicities. The stars in thelow-resolution spectroscopic survey should eventually yield >60 newplanets, including 8-9 hot Jupiters. Short-period planets have alreadybeen discovered orbiting the survey targets HIP 14810 and HD 149143.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| 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.
| Evaluating Gaia performances on eclipsing binaries. IV. Orbits and stellar parameters for SV Cam, BS Dra and HP Dra
This is the fourth in a series of papers that aim both to providereasonable orbits for a number of eclipsing binaries and to evaluate theexpected performance of Gaia of these objects and the accuracy that isachievable in the determination of such fundamental stellar parametersas mass and radius. In this paper, we attempt to derive the orbits andphysical parameters for three eclipsing binaries in the mid-F to mid-Gspectral range. As for previous papers, only the H_P, V_T, BTphotometry from the Hipparcos/Tycho mission and ground-based radialvelocities from spectroscopy in the region 8480-8740 Å are used inthe analyses. These data sets simulate the photometric and spectroscopicdata that are expected to be obtained by Gaia, the approved ESACornerstone mission to be launched in 2011. The systems targeted in thispaper are SV Cam, BS Dra and HP Dra. SV Cam and BS Dra have been studiedpreviously, allowing comparisons of the derived parameters with thosefrom full scale and devoted ground-based investigations. HP Dra has nopublished orbital solution. SV Cam has a β Lyrae type light curveand the others have Algol-like light curves. SV Cam has the complicationof light curve anomalies, usually attributed to spots; BS Dra hasnon-solar metallicity, and HP Dra appears to have a small eccentricityand a sizeable time derivative in the argument of the periastron. Thusall three provide interesting and different test cases.
| Evaluating the Performance of the GAIA Space Mission on and with Eclipsing Binaries: Three Problematic Systems, SV Cam, BS Dra, HP Dra
GAIA is a reconfirmed Cornerstone Mission of ESA, with an anticipatedlaunch date of 2011. Its primary purpose is to study the kinematics andstructure of the galaxy for which it will be equipped to domicroarcsecond astrometry, multi-band photometry, and radial-velocityspectroscopy on a billion of the brightest stars. GAIA will carry outits five-year survey mission from the L2 point of the Earth's orbit. Itis expected to discover of order one million eclipsing binaries, whichalone may keep ground-based observatories busy on follow-up programs fordecades to follow. Here we will review the general benefits of GAIA forstellar and galactic astronomy, and discuss its potential for SB2eclipsing binaries in particular. A group headed by U. Munari (Univ.Padova) has demonstrated GAIA's importance in a series of tests of theprecision and accuracy of fundamental stellar parameters from analysesof light and RV curves of selected systems. The trials conservativelymake use only of Hipparcos-Tycho photometry and ground-based echellespectroscopy matching GAIA's spectral (Ca triplet) region andapproximate resolution (~12,000). Here, we describe the determinationsof fundamental parameters for three of the most recently studiedsystems: SV Cam with complicated light curves and, in the data analyzedin this study, only 1 RV curve; BS Dra with nonsolar metallicity; and HPDra with a small eccentricity and a significant time derivative of theargument of periastron. The latter two systems have partial, sparselyobserved eclipses, which make the radiative properties difficult todetermine. Although the three systems represent limiting cases, theresults are nevertheless encouraging, with uncertainties in one or morecomponents approaching 2% in some parameters, and derived distancesfalling close to or within the errors of the Hipparcos determinations,for all three systems. Some of the work described here was supported byNSERC grants to EFM.
| 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
| 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)
| Observations of Two HIPPARCOS Eclipsing Variables
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.
|
Új cikk hozzáadása
Kapcsolódó hivatkozások
- - (nincs kapcsolódó hivatkozás) -
Új link hozzáadása
Besorolás csoportokba:
|
Pozíciós és asztrometriai adatok
| Csillagkép: | Sárkány |
| Rektaszcenzió: | 18h54m53.48s |
| Deklináció: | +51°18'29.8" |
| Vizuális fényesség: | 7.939 |
| Távolság: | 80.321 parszek |
| RA sajátmozgás: | 23.9 |
| Dec sajátmozgás: | 83 |
| B-T magnitude: | 8.671 |
| V-T magnitude: | 8 |
Katalógusok és elnevezések:
|
