36,629 research outputs found
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
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