Definition: A voice or mask that an author, speaker, or performer puts on for a particular purpose.
EX1) "According to those who knew him well, Hemingway was a sensitive, often shy man whose enthusiasm for life was balanced by his ability to listen intently . . .. That was not the Hemingway of the news stories. The media wanted and encouraged a brawnier Hemingway, a two-fisted man whose life was fraught with dangers. The author, a newspaper man by training, was complicit in this creation of a public persona, a Hemingway that was not without factual basis, but also not the whole man. Critics, especially, but the public as well, Hemingway hinted in his 1933 letter to [Maxwell] Perkins, were eager 'automatically' to 'label' Hemingway's characters as himself, which helped establish the Hemingway persona, a media-created Hemingway that would shadow--and overshadow--the man and writer."
(Michael Reynolds, "Hemingway in Our Times." The New York Times, July 11, 1999)
EX2) "It is to my other self, to Borges, that things happen. I walk about Buenos Aires and I pause, almost mechanically, to contemplate the arch of an entry or the portal of a church; news of Borges comes to me in the mail, and I see his name on a short list of professors or in a biographical dictionary. I am fond of hour glasses, maps, 18th-century typography, the etymology of words, the tang of coffee, and the prose of Stevenson; the other one shares these enthusiasms, but in a rather vain, theatrical way... I cannot tell which one of us is writing this page." (Jorge Luis Borges on his public persona)