When referring to something that is currently happening or existing, the phrase "are on" can be replaced with several synonyms. For example, "are present," "are occurring," or "are taking place" can be used to convey the same meaning. "Are happening," "are underway," or "are in progress" are also suitable replacements. In a more casual tone, "are going down" or "are going on" can be used as well. It's important to remember that while these synonyms may vary in tone and formality, they all denote a current state or action.