Are the antennae white or are they just catching the light?

I believe just catching the light. The sun was at a low angle when I took the picture.

As to gender I think male is correct. Nothing pronounced, but the wings have a slightly different coloration male to female.

As a side note, the Buckeyes play the Longhorns Monday evening, and even though I now live in Texas having lived in Ohio for 62 years, my allegiance is mixed.

I see a few other images have been marked m or f, but we don't have distinguishing marks listed in the guide yet.

It's usually not too difficult to tell, once you are familiar with most species of butterflies. In some there are dramatic differences in pattern, scaling, structure, or shape, but in most it is more subtle. Still in most butterflies there are differences that are pretty obvious once you know what to look for. In some groups (i.e. Swallowtails) you can immediately tell just by seeing the side or bottom of the tip of the abdomen, because the male claspers (=valvae) are very visible. In other groups (including the subfamily Nymphalinae, which includes Buckeyes) the claspers are harder to see, but are still there, and affect the shape of the abdomen. You can't always see the abdomen in photos, but when you can it is a good clue. The tip of the abdomen in males has the pair of claspers, which even if hidden by a clump of hair-like scales, gives the tip of the abdomen a blunt look from the side, and usually a slightly squared or bilobed look from above or below (nearly pointed in females). Also, the abdomen of females tends to be plump and rather symmetrical in shape, widest near the middle or sometimes the base, while the abdomen of the males is usually more slender and especially from the side less symmetrical in shape, with a tendency to be slightly widest near the end. Often males have proportionately longer abdomens, but this isn't very noticeable in Buckeyes. In most of the family Nymphalidae, the males have the wings less full and rounded, and often somewhat more angular in shape. The hind wing of males is often distinctly more anglular at the hind end (near the tip of the abdomen), while in females it is usually much more rounded. As for the pattern, Buckeye males and females look pretty similar, but the females usually have a somewhat different pattern toward the outer margin of the hind wings, with light areas usually better developed. Also, there is a tendency for females to have larger eye spots on the wings than males. Males are much more likely to have white antennae. and so on. On average males tend to be smaller than females, and often more active and more inclined to chase after things or act aggressively. Of course the best way to tell is to catch them and have an up close and personal look at the tip of the abdomen.

As I think other users would be interested in this response, I will write a comment so that this may be found from Beatriz's sex differentiation article, too.

Thanks, Hannah.