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Published online by Cambridge University Press: 03 August 2017
Drifts in radial velocities of OH maser features of the three semiregular variable stars R Crt, RT Vir and W Hya have been analyzed. The radial velocities of the extreme blue- and red-shifted features drifted by about 0.2 kms−1 to 1 km s−1 on time-scales of few months to several years. In the case of W Hya a blending effect of spectral features can account for those drifts. In the two other sources the velocity drifts are likely to be intrinsic to the clumps for which the velocities of peak emission vary due to appearance or disappearance of maser emission in the regions where circumstellar matter is still accelerated.