New MuSiCoS circular polarisation observations and ultra-high
precision determinations of the longitudinal magnetic field of the
Cepheid variable Aql show no convincing evidence of a
photospheric magnetic field. This result is in agreement with
measurements by Borra et al. (1981), and in conflict with recent
claims by Plachinda (2000). At present, the simplest conclusion is
that
Aql is a non-magnetic star, at least at the level of
10 G.
Acknowledgements
This work has taken advantage of the Vienna Atomic Line Database (VALD). GAW acknowledges grant support from the Natural Sciences and Engineering Research Council of Canada, and the Canadian Department of National Defence. WWW acknowledges support by the Fonds zur Förderung der wissenschaftlichen Forschung (P14984) and the Hochschuljubiläumsstiftung der Stadt Wien. We also acknowledge the referee, C. Johns-Krull, for useful comments leading to the improvement of this manuscript.
Copyright ESO 2002