Photometry of Masing and Nonmasing OH/IR Stars

by Geoffrey Francis Lawrence

Under the supervision of Professor Robert Gehrz

ABSTRACT

Broadband infrared photometry was performed on a sample of 60 stars with IRAS colors in the range displayed by Type II OH/IR stars. All of the stars have been tested for 1612 MHz OH maser emission by Eder, Lewis and Terzian (1988), but emission has been detected in only 27 of them. A morphological comparison is made between the the masing and nonmasing groups to discern whether masering is correlated with near and middle infrared properties. Both groups have the same scale height perpendicular to the galactic plane and share many characteristics in groups overlap significantly, we find no statistically significant difference in the K-L color distribution. Using theoretical models relating this color and the strength of the 9.7 micron silicate feature to the optical depth of the circumstellar dust shell, we find that red giant dust shells need minimum optical depth of tau 9.7 0.1 to support maser emission.