Combined HST and HAR imaging and photometry of eruptive binaries in globular cluster cores

We have combined the complementary qualities of HSTs high astrometric precision with TRIFFIDs extended coverage and photometric precision to perform crowded-field photometry in the innermost region of the post core-collapse globular cluster M15. Our technique virtually eliminates the problem of extreme crowding which has hitherto hampered searches for the predicted binary population in globular cluster cores, and thereby provides an extension of the HSTs capability. Our photometric study produced evidence of faint variable stars. We stress that it will require longer period photometry to uniquely identify the type of variable: should they be confirmed as eruptive binaries this would represent a vital step in our understanding of globular cluster evolution and dynamics. An interesting by-product of our program is that candidate bright cluster variables detected with the HST have been confirmed and monitored over longer periods.