Altair's inclination from line profile analysis^*

¹ Astronomy Department, University of California, Berkeley, CA 94720, USA e-mail: areiners@astron.berkeley.edu
² Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
³ Observatoire de Genève, 51 chemin des Maillettes, 1290 Sauverny, Switzerland e-mail: frederic.royer@obs.unige.ch
⁴ GEPI, CNRS UMR 8111, Observatoire de Paris, 5 place Janssen, 92195 Meudon Cedex, France

Received: 18 May 2004
Accepted: 9 August 2004

Abstract

We present a detailed spectroscopic study of line broadening in the A7IV-V star Altair. In a wavelength region covering 690 Å we reconstruct the overall broadening profile taking into account more than 650 spectral lines. From the broadening profile we determine the projected rotational velocity , 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 is () km s^-1. 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 and it rotates at  km s^-1 or slower than 53% of breakup velocity on a level.