A two channel high speed photometer for lunar occultation studies in the near - IR

Abstract

Lunar occultaion in the near infrared has been demonstrated by the PRL group to be an effective method of determining the angular size (in milliarcsecond range)and accurate effective temperature of red giants, supergiants and carbon stars. Many of these object (T lower script eff ~ 3000 K) have cooler circumstellar material at temperatures less than ~ 1000 K. A lunar occultaion observed simultaneously of such a star in the K(2.2 µm)and L(3.6 µm) filter bands can provide a complete high angular resolution infomation on both the star and the circumstellar region. For this purpose a two-channel fast photometer operating in the K and L bands has been developed recently at PRL. It incorporates a special dichroic beam-splitter for separating the K and L beams and several improvements over existing single channel system.