Abdul Kalam Asad, Satheesh Kumar (both 32) and Manjunathan (29) were arrested on a complaint from the Professor, who is also a Head of the Department, Inspector Kumaresan said.
The three students had written two obscene letters and when the Professor confronted them, they allegedly abused her verbally and threatened to murder her, he said.
They were booked under IPC section 294B (obscene act) and 506 (criminal intimidation) and the Tamil Nadu Prohibition of Harassment of Women Act.