EDP Sciences
Free access
Issue
A&A
Volume 430, Number 1, January IV 2005
Page(s) L17 - L20
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:200400120


A&A 430, L17-L20 (2005)
DOI: 10.1051/0004-6361:200400120

Letter

Strong latitudinal shear in the shallow convection zone of a rapidly rotating A-star

A. Reiners1, 2, M. Hünsch3, M. Hempel4 and J. H. M. M. Schmitt2

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
    e-mail: jschmitt@hs.uni-hamburg.de
3  Institut für Theoretische Physik und Astrophysik, Leibnizstrasse 15, 24098 Kiel, Germany
    e-mail: mhuensch@astrophysik.uni-kiel.de
4  Astrophysikalisches Institut Jena, Schillergäßchen 2-3, 07745 Jena, Germany
    e-mail: marc@astro.uni-jena.de

(Received 2 November 2004 / Accepted 9 December 2004 )

Abstract
We have derived the mean broadening profile of the star V 102 in the region of the open cluster IC 4665 from high resolution spectroscopy. At a projected equatorial rotation velocity of $v\,\sin{i} = (105 \pm 12)$ km s -1 we find strong deviation from classical rotation. We discuss several scenarios, the most plausible being strong differential rotation in latitudinal direction. For this scenario we find a difference in angular velocity of $\Delta\Omega = 3.6 \pm 0.8$ rad d -1 ( $\Delta\Omega/\Omega = 0.42 \pm 0.09)$. From the H $\alpha$ line we derive a spectral type of A9 and support photometric measurements classifying IC 4665 V 102 as a non-member of IC 4665. At such early spectral type this is the strongest case of differential rotation observed so far. Together with three similar stars, IC 4665 V 102 seems to form a new class of objects that exhibit extreme latitudinal shear in a very shallow convective envelope.


Key words: stars: rotation -- line: profiles -- stars: individual: IC 4665 V 102/P35 -- clusters: individual: IC 4665

SIMBAD Objects



© ESO 2005