The Dyer-Roeder relation in a universe with particle production

We have obtained analytical exact solutions of the Dyer-Roeder equation in a cosmological model where creation of particles occurs at the expenses of the gravitational field. We discussed the influences of inhomogeneities in the path of a light beam on the apparent diameter of astrophysical objects and consider both redshift independent as redshift dependent distributions of the inhomogeneities.Comment: 7 pages, 4 figures. Accepted to be published in the Astronomy and Astrophysics Journa

Differential rotation in early type stars

Using 2D models of rotating stars, the interferometric measurements of alpha Eri and its fundamental parameters corrected for gravitational darkening effects we infer that the star might have a core rotating 2.7 times faster than the surface. We explore the consequences on spectral lines produced by surface differential rotation combined with the effects due to a kind of internal differential rotation with rotational energies higher than allowed for rigid rotation which induce geometrical deformations that do not distinguish strongly from those carried by the rigid rotation.Comment: 3 pages ; to appear in the proceedings of the Sapporo meeting on active OB stars ; ASP Conference Series ; eds: S. Stefl, S. Owocki and A. Okazak