Silene antirrhina
An annual found throughout the United States in various habitats. In southern New Mexico and southern Arizona where I have seen it it is a winter-annual of dry, rocky slopes and oak woodland. The flowers are closed for much of the day.
Plant habit in the Sand Tank Mountains, Sonoran Desert National Monument, Arizona, 8 Mar 2008.
Side view of flowers in the Sand Tank Mountains, 8 Mar 2008.
More flowers in the Sand Tank Mountains, Sonoran Desert National Monument, 8 Mar 2008.