Identification of SH Delta v=1 ro-vibrational lines in R Andromedae

We report the identification of SH Delta upsilon, 1 re-vibrational lines in the published high-resolution infrared spectrum of the S-type star R Andromeda. This is the first astronomical detection of this molecule. The lines show inverse P Cygni profiles, indicating infall motion of the molecular layer due to stellar pulsation. A simple spherical shell model with a constant infall velocity is adopted to determine the condition of the layer. It is found that a single excitation temperature of 2200 K reproduces the observed line intensities satisfactorily. SH is located in a layer from 1.0 to similar to 1.1 stellar radii, which is moving inward with a velocity of 9 km s(-1). These results are consistent with the previous measurements of CO Delta upsilon = 3 transitions. The estimated molecular abundance SH/H is 1 x 10(-7), consistent with a thermal equilibrium calculation.