When it comes to expressing the idea of being in control or responsible for something, there are many synonyms for the phrase "are in charge." One possible option is "have authority," which implies a certain level of power or command over a situation or group of people. Another option is "are in control," which suggests more direct managerial or oversight responsibilities. "Lead," "manage," and "supervise" are also commonly used synonyms for this concept. Each of these phrases can be used to convey a slightly different nuance of responsibility and authority, depending on the context and tone of the communication.