Actor/screenwriter Robert Knott was in town this week celebrating the release of “Robert B. Parker’s Ironhorse,” the first of the Virgil Cole novels to be published since Robert Parker died three years ago. It’s Knott’s first novel. He previously co-wrote (with actor Ed Harris) the script for the film “Appaloosa,” the film based on Parker’s book of the same name. At his talk/signing at Porter Square Books, Knott was introduced by Joan Parker, the late writer’s widow. . . . Governor Deval Patrick and “Law & Order” actor Richard Brooks were in the audience at WGBH’s preview screening this week of “American Experience: The Abolitionists” at the Boston Public Library. . . . Houston Rockets forward Carlos Delfino dined at Bricco the other night. . . . Celtics rookie Jared Sullinger was among the first people in the door at this week’s reopening of Anthony Caturano’s Prezza, which had been closed after a kitchen fire over the summer. . . . Celtics coach Doc Rivers was spied supping at Scampo while Rockets guard James Harden was hanging out at Alibi. . . . Shag owner Sandy Poirier threw a birthday party for himself Thursday at Empire, but just as the place started rocking, Poirier worried that he was coming down with the flu and left.