THE PATTERN SPEED OF THE BAR IN NGC-936

We have used the Tremaine-Weinberg method to measure the angular speed of rotation for the bar in the SBO galaxy NGC 936. With this techniqu e, the bar's pattern speed, Omega(p), can be derived from the luminosi ty and stellar-kinematic information in long-slit spectral observation s taken parallel to the major axis of the galaxy. The kinematic measur ement required is the mean line-of-sight velocity of all stellar light entering the slit. This quantity can only be calculated reliably if a ny asymmetry in the shape of the broadening function of the spectral l ines is also measured, and so we present a method which allows for suc h asymmetry. The technique also returns a true measure of the rms unce rtainty in the estimate. Application of the analysis to a set of long- slit spectra of NGC 936 returns four separate measures of Omega(p) whi ch are mutually consistent. Combination of these data produces a best estimate for the bar pattern speed of Omega(p), = 60 +/- 14 km s(-1) k pc(-1) (assuming a distance of 16.6 Mpc). This result refines the only previous attempt to make this measurement, which yielded an estimate for Omega(p), in NGC 936 of 104 +/- 37 km s(-1) kpc(-1) The new measur ement places the co-rotation radius just beyond the end of the bar, in agreement with theoretical calculations.