First signatures of strong differential rotation in A-type stars

Details First signatures of strong differential rotation in A-type stars First signatures of strong differential rotation in A-type stars

Dec 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004iaus..224...95r&link_type=abstract

The A-Star Puzzle, held in Poprad, Slovakia, July 8-13, 2004. Edited by J. Zverko, J. Ziznovsky, S.J. Adelman, and W.W. Weiss,

Other

1

Stars: Rotation, Stars: Early-Type, Stars: Activity, Stars: Individual (Hd 6869, Hd 44892, Hd 60555, Hd 109238).

Scientific paper

We reanalyzed high quality spectra of 158 stars of spectral types A0-F1 and v sin{i} values 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. For 78 stars q2 could be determined and the ratio q2/q1 was used as a shape parameter sensitive to solar-like differential rotation (the equatorial velocity is faster than the near polar velocities). Seventy-four 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 their profiles shows any 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 these 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.

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