I was offered admission to a Canadian Neuroscience MSc/Ph.D. program and the supervisor I indicated in my letter of interest accepted me. I received the official admission letter today. Meanwhile, I just found out that another supervisor who is world renown for his work had sent me an email in September (5 months ago) saying he had shortlisted me and wanted to set up an interview. I had missed this email for reasons that are too long to explain here. I emailed him back today told him that I have already secured a supervisor but would love to discuss my interests with him. I wasn't expecting to hear back, but he said he will review my application and will let me know if I'm shortlisted again since he's still looking to take students. My question is: is it ethical to agree to an interview with him even though another supervisor has sent me an official offer of admission and agreed to supervise me? Would I lose my current offer if he finds out I'm being considered by someone else in the department? Any advice would be appreciated