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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.
| Interstellar polarization at high galactic latitudes from distant stars. 2: First results for Z less than or equal to 600 PC
We present the first results from our Crimean-Tuorla program forpolarimetry of distant stars at high galactic latitudes. The availableobservations reveal a clear increase in the interstellar linearpolarization of A and F stars, up to Z approximately equals 600 pc whereone reaches PV approximately equals 0.25%. This means anaverage AB greater than or equal to 0.11 mag over thenorthern polar cap for the diffuse component of the interstellarextinction that we are probing. There is no clear indication in the datathat the asymptotic level of PV has been reached, and withfuture observations above Z = 600 pc we shall investigate this question.The trend found is in agreement with the stellar reddening analysis byTeerikorpi (1990). The directions of the plane of vibration are inagreement with Markkanen's (1979) analysis of closer (Z less than 200pc) stars in his 'Area II'. Outside of this area we define two sectors Band C which encompass the Local Spiral Arm and had little stars inprevious investigations. Here the polarization vectors deviate stronglyfrom those in Markkanen's Area II, where one is probably looking at aninterarm region, close to the edge of the Local Spiral Arm. Ourmeasurements indicate for B and C average polarization vectorsconsistent with the direction l approximately equals 110 deg obtained byother authors for the magnetic field in the Local Spiral Arm using therotation measure method.
| 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
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| 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
| Studies of A and F stars in the region of the North galactic pole-II. uvby β photometry
Not Available
| A finding-list of stars of spectral type F2 and earlier in a north galactic pole region.
Not Available
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Observation and Astrometry data
| Constellation: | Άρκτος Μεγάλη |
| Right ascension: | 11h48m14.25s |
| Declination: | +31°54'32.7" |
| Apparent magnitude: | 10.093 |
| Proper motion RA: | -13.4 |
| Proper motion Dec: | 1.8 |
| B-T magnitude: | 10.478 |
| V-T magnitude: | 10.125 |
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