The pattern speed in the SB0 galaxy NGC 936

The pattern speed Ωp of the bar in NGC 936 is derived for the first time using a method outlined by Tremaine and Weinberg that depends only on the kinematics of the bar. Luminosity and radial-velocity profiles have been measured for four slices parallel to but offset from the apparent major axis of the disk. These are used to derive an apparent pattern speed Ωp sin i = 5.5±1.9 km s-1arcsec-1, which corresponds to Ωp = 104 km s-1kpc-1 in the plane of the disk (D = 16.6 Mpc, i = 41°). Using the rotation curve measured by Kormendy, the corotation radius lies between 28arcsec and 63arcsec. For comparison, the bar length is 52arcsec. The systematic errors affecting Ωp are discussed in detail.