Here's the official star alliance policy
Star Alliance Gold Customers Travelling in Any Class: Customers have access to any Star Alliance member carriers' owned lounges with the Star Alliance Gold logo at the entrance.
Customer must present proof of Star Alliance Gold level status via a valid frequent flyer program Star Alliance Gold level card or other valid indication of Star Alliance Gold level status
Customer must also present a boarding pass for travel on a Star Alliance flight departing from the local airport
Customer is entitled to one guest
Continental, United and US Airways Star Alliance Gold customers may only access the Red Carpet Clubs, US Airways Clubs and Presidents Clubs within the U.S. when travelling in conjunction with a Star Alliance international flight.