Credit: George Pimentel/Getty Images Photo: Erin Darke.tiff

The Half-Blood Prince? More like, the half-stud prince!

Harry Potter star Daniel Radcliffe attended a party at the Sundance Film Festival on January 18 for his new film Kill Your Darlings. Erin Darke, his co-star in the film, was also there, and she and Daniel were spotted kissing at the party, with Daniel frequently rubbing her knee, according to People.

"They've been dating for a while but have been debating going public," says one partygoer.

Another partygoer who worked on the film referred to Erin as Daniel's "girlfriend." 

However, when asked about Erin, Daniel played it cool, pretending like he didn't even know who "Erin" was. 

"Erin? Oh, Erin Darke?" he responded. "Yeah, the whole cast is here. It's fantastic." Talk about a chamber of secrets.

Kill Your Darlings is about a muder involving the Beat Generation in the 1940s, with 23-year-old Daniel playing poet Allen Ginsburg.

Daniel reportedly broke up with his then-girlfriend in the fall of 2012 in order to start seeing Erin.

Best of luck to Daniel and his new "darling"!

Source: People