Contents
Images
Upload your image
DSS Images Other Images
Related articles
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.
| 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
| A Photometric Study of the delta Scuti Star FG Virginis Undertaken during 1985/6
93 hours of photoelectric photometry of FG Virginis were obtained during1985 and 1986. Seven frequencies of pulsation with significantdetections could be extracted from the photometry. The seven detectedfrequencies agree with those found in a larger, independent photometricstudy by Breger et al. carried out during 1993, in which ten frequencieswere found. The present data also show the 8th and 9th frequencies foundduring 1993, but below the signal-to-noise limit of significance adoptedin our studies. The y amplitudes determined from the present work andthe 1993 data agree to +- 1.0 millimag, suggesting that no significantamplitude variations occurred during the eight years. For the dominantfrequency of 12.72 c/d a phase shift of theta-b-y - theta-y = 7 degreesis found, compatible with a nonradial p mode of 1=1 and 2. (SECTION:Stars)
| Simultaneous intensive photometry and high resolution spectroscopy of Delta Scuti stars. 1: Mode typing of HD 106384 defined as FG Virginis
53 hours of photometric observations and 7 hours of consecutive highresolution spectroscopic observations of the Delta Scuti star HD 106384defined as FG Vir have been obtained. From photometry we were able todetect 7 pulsation modes, 4 of which were also seen in the time seriesdescribing the variations of line profiles. From spectroscopy we alsoderived v sin i = 21 km/s and estimated i approximately = 30 deg. Theensuing discussion of the combined results of the analyses ofphotometric and spectroscopic data suggests that the dominant 12.72 c/dterm is probably the first radial overtone mode, two other terms (9.66and 19.86 c/d) are nonradial non-axisymmetric modes, while a fourth term(24.22 c/d) is an axisymmetric mode (may be radial). Problems connectedto mode typing and possible effects due to rotational splitting are alsodiscussed.
| HD 105759, a New Short Period Variable Star
Not Available
| FG Vir, Additional Photoelectric Observations
Not Available
| Lunar occultation summary. III
Observations of 242 photoelectric lunar occultation events studied atErwin W. Fick Observatory are reported. Approximately one-fourth ofthese are reappearances. From each observation are estimated the minimummagnitude differences between the observed object and possibleundetected companions. Occultation observations are given of 23 starsbrighter than 6th mag, including Alpha Vir, Beta-1 Sco, Mu Gem, Xi-2Sgr, Zeta Tau, Lambda Gem, and Beta Cap.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
| Constellation: | Παρθένος |
| Right ascension: | 12h09m47.75s |
| Declination: | -05°13'32.7" |
| Apparent magnitude: | 7.221 |
| Distance: | 66.225 parsecs |
| Proper motion RA: | -45.4 |
| Proper motion Dec: | 13.6 |
| B-T magnitude: | 7.655 |
| V-T magnitude: | 7.257 |
Catalogs and designations:
|
INHABITED SKY
