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Published online by Cambridge University Press: 12 April 2016
The J=2-1, v=0 emissions of 28SiO, 29SiO, and 30SiO from three late-type stars were simultaneously observed with the Nobeyama 45-m telescope in Jaunuary 1987. The relative intensities of [29SiO] / [30SiO] were measured to be 2.4 for χ Cyg, 1.5 for NML Tau, and 2.9 for V1111 0ph. These values are lower limits for the relative isotope abundance of [29Si] / [30Si], and are larger than the terrestrial value of 1.51. Recext theoretical studies suggest that hydrostatic nucleosysnthesis and supernova explosions result in smaller values of [29Si / [30 Si] than solar. These models cannot explain the observed excess of 29Si.