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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.
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Open clusters with Hipparcos. I. Mean astrometric parameters
New memberships, mean parallaxes and proper motions of all 9 openclusters closer than 300 pc (except the Hyades) and 9rich clusters between 300 and 500 pc have been computed using Hipparcosdata. Precisions, ranging from 0.2 to 0.5 mas for parallaxes and 0.1 to0.5 mas/yr for proper motions, are of great interest for calibratingphotometric parallaxes as well as for kinematical studies. Carefulinvestigations of possible biases have been performed and no evidence ofsignificant systematic errors on the mean cluster parallaxes has beenfound. The distances and proper motions of 32 more distant clusters,which may be used statistically, are also indicated. Based onobservations made with the ESA Hipparcos astrometry satellite
| Amendment of our method for deriving stellar membership of an open cluster
Our method for determining statistically the members of an open clusterby means of the proper motions (Missana et al.) is amended and itsvalidity is verified by applying it to the cluster IC 4756 with the datagiven by Herzog et al. (1975), adding nothing to their results. In thecomputation of the dispersion ellipses of the samples and of theChi2 for deriving the significance levels, the weights of theproper motions have been taken into account. The results obtained by thecriterion of the Chi2 and those obtained by Herzog et al. bythe criterion of the maximum likelihood of Sanders (1971) areconcordant.
| A four-color and Hbet study of the galactic cluster IC 4756.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978PASP...90..157S&db_key=AST
| Membership and photometry of the open cluster IC 4756
Probabilities of membership, based on relative proper motions, for 464stars in the field of IC 4756 are given. The cluster proper motiondispersion (m.e.) of 0.09 sec of arc yields 173 probable members.Photographic UBV magnitudes of 471 stars in the field are presented. Thecolor excess of IC 4756 is E(B-V) equal to 0.19 min; the apparentdistance modulus equals 8.5 min, corresponding to the true distance of400 pc. The membership probabilities of 6 blue stragglers and of thesupergiant HD 172365 (F9 Ib) are discussed.
| Untersuchung der offenen Sternhaufen IC 4665, NGC 6633, IC 4756
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Pozíciós és asztrometriai adatok
| Csillagkép: | Kígyó |
| Rektaszcenzió: | 18h39m48.18s |
| Deklináció: | +05°36'14.9" |
| Vizuális fényesség: | 9.647 |
| RA sajátmozgás: | 1.3 |
| Dec sajátmozgás: | -2.6 |
| B-T magnitude: | 10.079 |
| V-T magnitude: | 9.683 |
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