Popular southern film stars Ram Charan, Nivin Pauly and Sivakarthikeyan will grace the audio launch of Vikram-starrer upcoming Tamil actioner "Iru Mugan" here on August 2.In an official statement, the makers confirmed the participation of the three stars.The makers also said that they are in talks with a Bollywood star who could be the fourth guest of the event."It's going to be a mega event. Ram Charan, Nivin and Sivakarthikeyan have already committed to attend. If everything goes well, a leading Bollywood star might also attend the event," a source from the film's unit told IANS.Directed by Anand Shankar, "Iru Mugan" is a spy thriller also starring Nayanthara and Nithya Menen.The film, which is slated for October 2 release, is produced by Thameens Films.