NEW YORK—In a manner sources described as “effortlessly chill,” actress Chloë Sevigny reportedly said “Hey” Thursday in a cool, unaffected greeting to her firstborn child. “Oh, hey, what’s up?” said Sevigny, addressing her newborn son for the first time with mild interest as she glanced around the room. “New here? Mmm. So you’re a baby? I was once a baby. I like your name. Well, I got to run. Later.” At press time, sources confirmed Sevigny was laughing boisterously at something clever her baby must have said.