An approach to effective temperature and surface gravity in post-AGB and RV Tauri stars at the near-IR region

Abstract

A number of empirical correlations that allows us to calculate the effective temperature and surface gravity for a set evolved post-AGB and RV Tauri stars are determined using as calibrators the intrinsic colours of 2MASS (Two Micron All Sky Survey) photometry. We have analyzed a total sample of 36 stars where 25 are post-AGB stars and 11 are RV Tauri stars, respectively. A group of 11 stars with parallaxes measures were used as calibrators of the absolute magnitude. The result for T_eff and log g from intrinsic colours (J-H)₀ and (H-K_s)₀ at the near-infrared pass bands reach a dispersion of 220 K and 0.27, respectively. We can estimate the absolute magnitude using the intrinsic colour in the near-infrared band with an uncertainty of 0.28 mag. This indicates that (J-H)₀ and (H-K_s)₀ show sensitivity to the absolute magnitude.