Garrett Sussman hired as Head of Portfolio Management Apollo's Brooke Callaghan joins as Head of Investor Relations GREENWICH, Conn., July 10, 2019-- Prostar Capital ("Prostar"), a global private investment firm focused on midstream energy infrastructure assets, today announced that it has expanded its team with the appointments of Garrett Sussman and Brooke Callaghan as Head of Portfolio Management and Head of Investor Relations, respectively.