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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.
| 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
| Young red supergiants and the near-infrared light appearance of disk galaxies
We have searched for spatial variations in the 2.3 m photometric COindex within the disks of three nearby galaxies. This index measures thestrength of the absorption bands of molecular CO in stellar atmospheresand is strong in cool, low surface gravity stars, reaching the largestvalues for red supergiants. We observe significant spatial CO indexvariations in two galaxies, indicating that the dominant stellarpopulation in the NIR is not everywhere the same. Central CO index peaksare present in two galaxies; these could be due to either metallicitygradients or to recent star formation activity. In addition, significantazimuthal CO index variations are observed in one. Because strongazimuthal metallicity gradients are physically implausible in diskgalaxies, these features are most naturally explained by the presence ofa young stellar population. The fraction of 2 m light due to youngstellar populations in star-forming regions can be calculated from ourdata. Overall, young stellar populations can contribute 3 percent of theNIR flux of a (normal) galaxy, which is consistent with other globalproperties. Locally, this fraction may rise to 33 percent. Thus, youngstars do not dominate the total NIR flux, but can be locally dominant instar-forming regions, and can bias estimates of spiral arm amplitude orother nonaxisymmetric structures in galaxies' mass distributions.
| VI photometry of selected SAO stars
Johnson V- and I-band photoelectric photometry has been obtained for 158SAO stars in a continuing program in support of the Near InfraredPhotographic Sky Survey. These data are utilized in the calibration ofthe survey photographs and are presented here to assist other programsreliant upon access to photometry in the photographic infrared.
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| Takýmyýldýz: | Koc |
| Sað Açýklýk: | 03h15m34.58s |
| Yükselim: | +26°54'12.1" |
| Görünürdeki Parlaklýk: | 7.945 |
| Uzaklýk: | 156.986 parsek |
| özdevim Sað Açýklýk: | 35.3 |
| özdevim Yükselim: | -32.4 |
| B-T magnitude: | 8.23 |
| V-T magnitude: | 7.969 |
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