DENSITY, TEMPERATURE, AND ISOTOPIC ABUNDANCE IN MOLECULAR GAS AROUND ZETA-OPHIUCHI

The J = 2-1 lines of (CO)-C-12 and (CO)-C-13 have been observed around zeta Oph at positions corresponding to the earlier J = 1-0 data of Li szt, in order to determine the number density, temperature, and isotop ic abundance ratio. The observations are consistent with a range of ph ysical conditions. For temperatures of 20-40 K, the H-2 number density is only 50% higher at the J = 1-0 emission peak than toward the star, the column density N(CO) is larger by a factor of a few, and the (CO) -C-12/(CO)-C-13 column density ratio is 60. For T(k) less-than-or-equa l-to 10 K, both the CO column density and H-2 number density would be larger by factors of 5-20 (compared to the line of sight toward zeta O ph) and the isotope ratio in CO would be greater than 89.