A PHOTOMETRIC AND SPECTROSCOPIC STUDY OF THE BRIGHTEST NORTHERN CEPHEIDS - II - FUNDAMENTAL PHYSICAL PARAMETERS

We present a new Cepheid reddening and effective temperature scale bas ed on the uvby photometry published in the first paper of this series. Using all available information about the companion stars in Cepheids with bright blue secondaries, we remove their light from the observed light and colour curves. The resulting corrections are as large as 0. 05-0.15 mag in several cases for different colour indices. A new photo metric approach based on the (b-y) versus (B-V) two-colour diagram is tested with three other previous calibrations taken from the literatur e. Two uvby relations in earlier studies turn out to be the most relia ble and consistent, and so they are used in deriving colour excesses. We determine systematically higher reddenings for Cepheids with a sign ificant secondary light correction. The dereddened Stromgren colours a re calibrated in terms of T-eff and log g using the most recent synthe tic colour grids. Our temperature scale is very close to that of Kraft , which is supported by other recent temperature determinations using the infrared flux method or Geneva photometry. The photometric graviti es fit some of the earlier theoretical and observational (mainly spect roscopic) results very well.