2004A&A...428..199R

We present a detailed spectroscopic study of line broadening in the A7IV-V star Altair. In a wavelength region covering 690Å we reconstruct the overall broadening profile taking into account more than 650 spectral lines. From the broadening profile we determine the projected rotational velocity vsini, derive an upper limit for the equatorial velocity v from the shape of the profile and search for signatures of differential rotation. Our redetermined value of vsini is (227±11)km/s. Measuring the first two zeros of the Fourier transformed broadening profile yields no signatures of differential rotation. We derive that Altair is seen under an inclination angle higher than i=68° and it rotates at v<245km/s or slower than 53% of breakup velocity on a 1σ level.