Abstract. We present calibrations of the effective temperatures of giant stars versus [Fe/H] and colours (U. These calibrations are based on a large sample of field and globular cluster stars which roughly cover spectral types from F0 to K5. Their effective temperatures, scaled to direct T eff determinations via reliable angular diameter measurements, were derived by applying the infrared flux method. The empirical relations have been fitted to polynomials of the form θ eff = P (colour, [Fe/H]) by using the least squares method. The precision of the fits ranges from 40 K for (V −K) to 170 K for (J −H). We tabulate intrinsic colours of giant stars in the ranges: 3500 K ≤ T eff ≤ 8000 K; −3.0 ≤ [Fe/H] ≤ +0.5. We also present the calibration of BC(V) as a function of log(T eff ) and metallicity. Finally, we compare the resulting scale of temperatures with previous works.

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Abstract. -We have applied the InfraRed Flux Method (IRFM) to a sample of 475 dwarfs and subdwarfs in order to derive their effective temperatures with a mean accuracy of about 1.5%. We have used the new homogeneous grid of theoretical model atmosphere flux distributions developed by Kurucz (1991Kurucz ( , 1993 for the application of the IRFM. The atmospheric parameters of the stars cover, roughly, the ranges: 3500 K ≤ Teff ≤ 8000 K; −3.5 ≤ [Fe/H] ≤ +0.5; 3.5 ≤ log(g) ≤ 5. The monocromatic infrared fluxes at the continuum, and the bolometric fluxes are derived using recent results, which satisfy the accuracy requeriments of the work. Photometric calibrations have been revised and applied to estimate metallicities, although direct spectroscopic determinations were preferred when available. The adopted infrared absolute flux calibration, based on direct optical measurements of angular stellar diameters, sets the effective temperatures determined using the IRFM on the same scale than those obtained by direct methods. We derive three temperatures, TJ , TH and TK , for each star using the monochromatic fluxes at different infrared wavelengths in the photometric bands J , H, and K. They show good consistency over 4000 K, and no trend with wavelength may be appreciated. We provide a detailed description of the steps followed for the application of the IRFM, as well as the sources of the errors associated to the different inputs of the method, and their transmission into the final temperatures. We also provide comparison with previous works.

The sign of coefficient a(3) in the general formula of Table 2 should be plus instead of minus. Thus, the formula should read: θ eff = a 0 + a 1 X + a 2 X 2 + a 3 X[Fe/H] + a 4 [Fe/H] + a 5 [Fe/H] 2 .

A B S T R A C TWe present contemporaneous optical and infrared (IR) photometric observations of the Type IIn SN 1998S covering the period between 11 and 146 d after discovery. The IR data constitute the first ever IR light curves of a Type IIn supernova. We use blackbody and spline fits to the photometry to examine the luminosity evolution. During the first 2±3 months, the luminosity is dominated by the release of shock-deposited energy in the ejecta. After ,100 d the luminosity is powered mostly by the deposition of radioactive decay energy from 0X150X05 M ( of 56 Ni which was produced in the explosion. We also report the discovery of an astonishingly high IR excess, K 2 L H 2X5Y that was present at day 130. We interpret this as being due to thermal emission from dust grains in the vicinity of the supernova. We argue that to produce such a high IR luminosity so soon after the explosion, the dust must be preexisting and so is located in the circumstellar medium of the progenitor. The dust could be heated either by the UV/optical flash (IR echo) or by the X-rays from the interaction of the ejecta with the circumstellar material.