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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.
| Ultraviolet Imaging Observations of the cD Galaxy in Abell 1795: Further Evidence for Massive Star Formation in a Cooling Flow
We present images from the Ultraviolet Imaging Telescope (UIT) of theAbell 1795 cluster of galaxies. We compare the cD galaxy morphology andphotometry of these data with those from existing archival and publisheddata. The addition of a far-UV color helps us to construct and test starformation model scenarios for the sources of UV emission. Models of starformation with rates in the range ~5--20 Mȯ yr-1 indicate that thebest-fitting models are those with continuous star formation or a recent(~4 Myr old) burst superimposed on an old population. The presence ofdust in the galaxy, dramatically revealed by Hubble Space Telescopeimages, complicates the interpretation of UV data. However, we find thatthe broadband UV/optical colors of this cD galaxy can be reasonablymatched by models using a Galactic form for the extinction law with EB-V= 0.14. We also briefly discuss other objects in the large UIT field ofview.
| Kinematics and properties of F stars near the North Galactic Pole. II - The isothermal disc
Radial velocities are given for about 550 photometrically-identifieddisk-population F stars lying within 15 deg of the North Galactic Pole.The overall radial and z-velocity distributions are found to be closelyGaussian, with corrected rms and mean z velocities of 11.3 + or - 0.6and -9.5 + or - 0.5 km/s, respectively. The isothermal kinematics of thepopulation are reflected in the constant velocity dispersion to a zdistance of 400 pc. No systematic variation of either the velocitydispersion or the stellar age with the metallicity-sensitive Stromgrendelta m1 index is noted over a range of ages up to 5 Gyr.
| Further Studies of A-Stars and F-Stars in the Region of the North Galactic Pole - Part Four - a Catalogue of Uvbyr Photometry and Derived Quantities
Not Available
| Further Studies of A-Stars and F-Stars in the Region of the North Galactic Pole - Part Three - a Catalogue of Star Names and Positions
Not Available
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Osservazione e dati astrometrici
| Costellazione: | Boote |
| Ascensione retta: | 13h48m02.80s |
| Declinazione: | +26°30'55.5" |
| Magnitudine apparente: | 9.162 |
| Moto proprio RA: | -34 |
| Moto proprio Dec: | 13.8 |
| B-T magnitude: | 9.565 |
| V-T magnitude: | 9.196 |
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