The gushing fans might well have been tweens swooning over “Twilight” ’s Robert Pattinson . But the starstruck belonged to a slightly different demographic. They were members of WGBH’s Ralph Lowell Society (supporters who give $1,500 or more annually to the station) and their guests.

Their heels were largely sensible, their hair was often silver, many were men, but bosoms were heaving at WGBH’s Brighton studios on Saturday. Two of the biggest stars of “Downton Abbey ” had come to town: Lord Grantham (OK, the actor Hugh Bonneville ) and Thomas (really Rob James-Collier , wearing decidedly non-Thomas-like coral high-top Nikes, facial stubble, and shaggy hair).