SiO isotope emissions from late-type stars

Abstract

The J=2-1, v=0 emissions of ²⁸Si0,²⁹Si0, and ³⁰Si0 from three late-type stars were simultaneously observed with the Nobeyama 45-m telescope in January 1987. The relative intensities of (²⁹Si0 ) / (³⁰Si0 ) were measured to be 2.4 for χ Cyg, 1.5 for NML Tau, and 2.9 for V1111 Oph. These values are lower limits for the relative isotope abundance of (²⁹Si) / [³⁰Si) , and are larger than the terrestrial value of 1.51. Recent theoretical studies suggest that hydrostatic nucleosysnthesis and supernova explosions result in smaller values of (²⁹Si) / (³⁰Si) than solar. These models cannot explain the observed excess of ²⁹Si.