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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.
| The nearby ellipsoidal variable TV Pictoris
TVPic is identified as a bright, near-contact mid-A+early-F binary seenunder a moderate inclination of 54degr . From the analyses reported inthis paper, it appears that both components are undermassive (1.2+0.4M_ȯ), and that the secondary rotates not synchronously but morethan twice as fast. These conclusions follow from the analysis of (1)high-dispersion spectra near both quadrature phases, to which thesecondary contributes roughly 10% in the visual light, and (2)light-curves in the Stromgren and Walraven system covering the interval3200-5600 { Angstroms} and a time span of more than 2600 rotationalperiods. The light-curves show a very pronounced O'Connell effect, andonly marginal colour variations. Models assuming a temperature spoteither on the primary or the secondary explain the major part of theasymmetry in the light-curves, and are intended to provide usefulinitial estimates for more advanced mathematical codes. However, a morerealistic physical model will require more discriminatory data,including spectroscopic observations in other spectral windows, andspectroscopy over the whole orbital cycle. Based on observationsobtained at the European Southern Observatory (ESO), La Silla, Chile
| A photoelectric investigation of light variability in AP stars
A study of the light variability of a number of peculiar A stars, mainlyin Stromgren colors u and v and in peculiarity index Delta-a, leads tothe proposal of the following light variability periods: (1) HD 5601,1.11 days; (2) HD 19712, 2.19 days; (3) HD 30849, 15.86 days; (4) HD38823, 8.64 days; (5) HD 53116, 11.98 or 18.10 days; (6) HD 56022, 0.92days; and (7) HD 81009, 33.97 days. In addition, evidence is given forvariability of HD 94660 on a time scale on the order of months or years,and it is shown that the rotation period proposed by Borra andLandstreet (1980) for HD 25267 is not supported by the light variationsobserved. The character of Delta-a variability is discussed.
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