Revised Stromgren metallicity calibration for red giants
Abstract
A new calibration of the Stromgren (b - y), mi diagram in terms of iron abundance of red giants is presented. This calibration is based on a homogeneous sample of giants in the globular clusters omega Centauri, M 22, and M 55 as well as field giants from the list of Anthony-Twarog & Twarog (1998). Towards high metallicities, the new calibration is connected to a previous calibration by Grebel & Richtler (1992), which was unsatisfactory for iron abudances lower than -1.0 dex. The revised calibration is valid for CN-weak/normal red giants in the abundance range of -2.0 <[Fe/H]< 0.0 dex, and a color range of 0.5 < (b - y) < 1.1 mag.
As shown for red giants in omega Centauri, CN-weak stars with Stromgren metallicities higher than -1.0 dex cannot be distinguished in the (b - y), m(1) diagram from stars with lower iron abundances but higher CN band strengths.
As shown for red giants in omega Centauri, CN-weak stars with Stromgren metallicities higher than -1.0 dex cannot be distinguished in the (b - y), m(1) diagram from stars with lower iron abundances but higher CN band strengths.
Description
Keywords
stars : abundances, stars : chemically peculiar, stars : late-type, Galaxy : globular clusters : individual : omega Cen, Galaxy : globular clusters : individual : M 22