Near infrared photometry and analysis of OH maser stars of different types

Abstract

We give results of near infrared observations of 17 stars of different OH maser types including their J, H and K magnitudes and fluxes. Their IRAS conterparts are identified. From a simultaneous analysis of their near infrared, far infrared and OH radio data we derive their near and far infrared luminosities L 1 and L 2, infrared gradients S 1, characteristics S 10 of the silicate 10 μ feature and the mass loss rate of the central star M ̇ . We found that, for all OH maser types, L 1, L 2, S 1 and S 10 all tend to increase with increasing mass loss rate. This shows that, for the red giants in the AGB sub-branch, there exists indeed a tightly connected evolutionary sequence from optical Mira stars to optically invisible OH/IR stars, from OH-1665/1667 masers to OH-1612 masers.