Letter to the Editor

Effective temperatures and radii of planet-hosting stars from IR photometry

¹ Departament d'Astronomia i Meteorologia, Av. Diagonal, 647, 08028 Barcelona, Spain e-mail: emasana@am.ub.es
² Laboratorio de Astrofísica Espacial y Física Fundamental (LAEFF), Apdo. 50727, 28080 Madrid, Spain e-mail: esm@laeff.esa.es
³ Research and Scientific Support Department, ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands e-mail: agimenez@rssd.esa.int

Corresponding author: I. Ribas, iribas@am.ub.es

Received: 7 October 2003
Accepted: 16 October 2003

Abstract

In this paper we present and analyse determinations of effective temperatures of planet-hosting stars using infrared (IR) photometry. One of our goals is the comparison with spectroscopic temperatures to evaluate the presence of systematic effects that could alter the determination of metal abundances. To estimate the stellar temperatures we have followed a new approach based on fitting the observed 2MASS IR photometry with accurately calibrated synthetic photometry. Special care has been put in evaluating all sources of possible errors and incorporating them in the analysis. A comparison of our temperature determinations with spectroscopic temperatures published by different groups reveals the presence of no systematic trends and a scatter compatible with the quoted uncertainties of 0.5–1.3%. This mutual agreement strengthens the results of both the spectroscopic and IR photometry analyses. Comparisons with other photometric temperature calibrations, generally with poorer performances, are also presented. In addition, the method employed of fitting IR photometry naturally yields determinations of the stellar semi-angular diameters, which, when combined with the distances, results in estimations of the stellar radii with remarkable accuracies of ~2–4%. A comparison with the only star in the sample with an empirically determined radius (HD 209458 – from transit photometry) indicates excellent agreement.