Here is a good refresher paper on starform histories SB types in general, incl. 5643 in passing:
arXiv:
astro-ph/0606460v2
Galaxyman's links to all the GALEX stuff is a siren song for someone chafing at lustrous skies arriving just in time for the full moon. I'd say the GALEX images will keep me off the streets for awhile, but my area is so remote there are no streets to be off of.
=Dana in SA