The bar pattern speed of dwarf galaxy NGC 4431

We present surface photometry and stellar kinematics of NGC 4431, a barred dwarf galaxy in the Virgo Cluster undergoing a tidal interaction with one of its neighbors, NGC 4436. We measured its bar pattern speed using the Tremaine-Weinberg method and derived the ratio of the corotation radius, D-L, to the bar semimajor axis, a(B). We found D-L/a(B) = 0.06(-0.4)(+1.2) at 99% confidence level. Albeit with large uncertainity, the probability that the bar ends close to its corotation radius (i.e., 1.0 <= D-L/a(B) <= 1.4) is about twice as likely as that the bar is much shorter than the corotation radius ( i.e., D-L/a(B) > 1.4)