Pablo Picasso and Marie-Thérèse Walter’s love affair was quiet but intense. When they began seeing each other, in 1927, she was a 17-year-old French model and he was 45—and still with his first wife, Olga Khokhlova. The lovers kept their affair secret until, in 1935, they had a child together. Though most of their relationship was conducted behind closed doors, Walter became known as Picasso’s “golden muse.” He drew her portrait repeatedly, inspired by her oval face and curves. On the 50th anniversary of the artist’s death, a still life that pays homage to Walter is going up for auction at Sotheby’s—it’s called Le Cirque (1933)—along with treasures by Philip Guston, Marc Chagall, Claude Monet, and Balthus. —Elena Clavarino