Malc's z=0.003943 value for N5643, coupled with Robert's Carnegie blue and now his Ha images showing irregular disk torques got me to thinking about ancient interactivity affecting the gx. There's a faint galaxy, PGC 538542, roughly 6' SSE with a
NED listed z=0.003595 (subject to important NED "See essential note" caveat) and Heliocentr.radial vel. of 1078 m/sec. No transverse velocity available, but a back-of-envelope (and part of front) calculation makes me wonder if the PGC may have grazed 5643's arm some 55+ myr ago. The locale of SN 2013aa 196 arcsec fm 5643's core (thanks again, Malc) still has me wondering how it got there. Now the thought comes it might be an ejected binary system.
I wonder if any of IIS's experienced AP hands might try some very deep field images in the B band seeking faint emissions not recorded in existing images. Then, as per Greg Bock's excl suggestion, overlay the images on the SN and see what turns up.