I would give that a yes, with the caveat of exprimentation. I vaguelly remember my manual covering that. If not the manual, it was in one of the Oly publications from the late 80's. Never hurts to give a try.
Pop the flash on, then step the aperture back down to set the ratio between main light (sun, etc) and the fill flash. Flash expects f/2.8, so f/4 gives 1:2 or so for a lighting ratio, suits colur in my view. f/5.6 may be better for b&w.
The Oly manual gives the info. Attached are the tables that I paste onto the back of my XA's A16 flash, and the camera body.
Hi, Darrin, there are three flashes for the Olympus XA the little A9M which is manual the A11 is a computer flash that varies it's output, and so is the largest the A16 , which one are we talking about ?
A11 and A16 can be set as manual (set lens to exposure to match distance, with right guide number for film speed being used).
They also have auto settings for 100 and 400 speed films. These are set with a little lever beside the auto exposure eye on the flash.
The A16 has the most punch, but not much. The A11 is about 1 stop weaker. I think the numbers might be guide number in meters with 100asa film.
The A9M I have not used but I believe it was to be used for macro work with an XA3, and don't think it actually has an easily user replacable battery. Others may have better knowledge of the A9M.