Direct observations of rotationally distorted stars

We present infrared interferometric angular size measurements for rapidly rotating stars which indicate non-circular projected disk brightness distributions. For the A7IV-V star Altair, assuming that the apparent oblateness of the photosphere is due to the star's rapid rotation, a rigorous evaluation of the observation data in the context of a rigidly rotating Roche model shows that. an estimate of v sin i = 210 +/- 13 km s(-1) can be derived that is independent of spectroscopic techniques. Altair is the first main sequence star for which direct. observations of an oblate photosphere have been reported: and the first star for which v sin i has been established from observations of the stars photospheric geometry. Future prospects for this technique are considered, and a prospective catalog of 67 rotationally oblate targets is presented.