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A&A 415, 325-329 (2004)
DOI: 10.1051/0004-6361:20034175
First signatures of strong differential rotation in A-type stars
A. Reiners1 and F. Royer2, 31 Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
e-mail: areiners@hs.uni-hamburg.de
2 Observatoire de Genève, 51 chemin des Maillettes, 1290 Sauverny, Switzerland
e-mail: frederic.royer@obs.unige.ch
3 GEPI, CNRS UMR 8111, Observatoire de Paris, 5 place Janssen, 92195 Meudon cedex, France
(Received 8 August 2003 / Accepted 6 November 2003)
Abstract
We reanalyzed high quality spectra of 158 stars of
spectral types A0-F1 and
between 60 and
150 km s
-1. Using a Least Squares Deconvolution technique
we extracted high
S/N broadening profiles and determined the
loci of the Fourier transform zeros
q1 and
q2 where the
S/N-ratio was high enough. The values of
were
redetermined and found to be consistent with the values derived
by (2002). For 78 stars
q2 could be determined and
the ratio
q2/q1 was used as a shape parameter sensitive
for solar-like differential rotation (Equator faster than Pole).
74 of the 78 stars have values of
q2/q1 consistent with
solid body rotation; in four of the 78 cases, values of
q2/q1 are not consistent with rigid rotation. Although
these stars may be binaries, none of the profiles shows signatures
of a companion. The Fourier transforms do not indicate any
distortions and the broadening profiles can be considered due to
single objects. One of those candidates may be an extremely rapid
rotator seen pole-on, but for the other three stars of spectral
types as early as A6, differential rotation seems to be the most
plausible explanation for the peculiar profiles.
Key words: stars: rotation -- stars: early-type -- stars: activity
Offprint request: A. Reiners, areiners@hs.uni-hamburg.de
SIMBAD Objects
© ESO 2004
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