Hi Andrew, hate to the bearer of bad news, but there is no way can be the companion to Antares, sorry.
The angular separtation between the two is listed as 0.55". Antares on your image is spread across a far greater angle. the companion is allways going to be lost in the glare of Antares except under special conditions or maybe the hubble scope or better.
Dave Gee did manage to video an occultation of the Moon and Antares which shows the secondary briefly before the main star cleared the limb of the moon and swamped out the secomdary.
His link seems to not work now, but he might be able/willing to reactivate it if requested.
His email is
dave4gee@yahoo.com.au
and the old link that seems not to work is
http://us.share.geocities.com/dave4gee/antares_r_clip.mpg
cheeres,
Doug