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 semi-major axis , a _ { B } .
We found D _ { L } / a _ { B } = 0.6 ^ { +1.2 } _ { -0.4 } at 99 \% confidence level .
Albeit with large uncertainty , the probability that the bar ends close to its corotation radius ( i.e. , 1.0 \leq D _ { L } / a _ { B } \leq 1.4 ) is about twice as likely as that the bar is much shorter than corotation radius ( i.e. , D _ { L } / a _ { B } > 1.4 ) .