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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 Dimensions of the A-Type Eclipsing Binary V364 Lacertae
We present photoelectric observations in B and V, as well asspectroscopic observations of the 7.3 day period double-lined eclipsingbinary V364 Lacertae. From the analysis of the light curves and theradial velocity curves we have determined the absolute dimensions of thecomponents with high precision (<~1%). The masses for the primary andsecondary are M_A=2.333+/-0.015 M_solar and M_B=2.296+/-0.025 M_solar,respectively, and the radii are R_A=3.307+/-0.038 R_solar andR_B=2.985+/-0.035 R_solar. We derive also effective temperatures ofT^A_eff=8250+/-150 K and T^B_eff=8500+/-150 K, and projected rotationalvelocities of v_Asini=45+/-1 km s^-1 and v_Bsini=15+/-1 km s^-1.Evolutionary tracks from current stellar evolution models are in goodagreement with the observations for a system age of logt=8.792 (6.2x10^8yr) and for solar metallicity. Hints of a lower metallicity fromspectroscopy and photometry appear to be ruled out by these models, buta definitive comparison must await a more accurate spectroscopicabundance determination. Analysis of all available eclipse timings alongwith our radial velocities of this moderately eccentric system(e=0.2873+/-0.0014) has revealed a small but significant motion of theline of apsides of ω=0.00258+/-0.00033 deg cycle^-1, correspondingto an apsidal period of U=2810+/-360 yr. The contribution from generalrelativity effects is significant (~17%). A comparison with predictionsfrom interior structure models shows the real stars to be lessconcentrated in mass than expected. Our measurements of the projectedrotational velocities indicate that the primary star is essentiallypseudosynchronized (synchronized at periastron), while the secondary isspinning 3 times more slowly and is not yet synchronized. Both therotational status of the stars and the nonzero eccentricity of the orbitare consistent with the predictions from tidal theory, specifically forthe radiative damping mechanism.
| Observations and period variation analysis of the W UMA type star SW Lac.
Abstract image available at:http://adsabs.harvard.edu/abs/1993RMxAA..25...63P
| The Light-Variability of Early B Giants.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1959ApJ...130..577L&db_key=AST
| 3 W UMa-type binaries with changing periods.
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Osservazione e dati astrometrici
| Costellazione: | Lucertola |
| Ascensione retta: | 22h53m31.25s |
| Declinazione: | +38°26'40.8" |
| Magnitudine apparente: | 7.84 |
| Distanza: | 203.252 parsec |
| Moto proprio RA: | 7.6 |
| Moto proprio Dec: | -1 |
| B-T magnitude: | 8.134 |
| V-T magnitude: | 7.865 |
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