S Boötis should not be confused with Sigma Boötis.
S Boötis is a Mira variable in the constellation Boötes. It ranges between magnitudes 7.8 and 13.8 over a period of approximately 270 days. It is too faint to be seen with the naked eye, however when it is near maximum brightness it can be seen with binoculars.
S Boötis was discovered at Bonn Observatory by Friedrich Wilhelm Argelander in 1860.