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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.
| Surface photometry and spectral analysis of Mk50 - A Seyfert 1 nucleus in an early type galaxy
Markarian 50 is analyzed using V and I CCD frames and IPCS and CCDspectra, obtained in June 1985, covering the range 3200-10,000 A. It isinferred from the surface brightness profiles derived from the imagesthat this is an early-type, elliptical, or S0 galaxy, which is supportedby the spectral analysis of the stellar population. After subtraction ofthe stellar population, the emission properties of the Seyfert 1 nucleusare studied. In the low state, a strong broad H-alpha with an FWHM of4500 km/s is detected, whereas H-beta is stronger than O III 5007 by afactor of about 2 (in flux). The stellar population fractions in thehigh-state continuum are 48 percent at 3800 A, 71 percent at 5000 A, and82 percent at 8900 A. Permitted Fe emission has similar intensities inthe high and low states, showing that its formation zone does notcoincide with that of the broad H I and He I lines, i.e., it is fartherthan five light-years from the central source.
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