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(gzipped) PostScript## Magnetic models of slowly rotating magnetic Ap stars: aligned magnetic and rotation axes
^{1} University of Western Ontario, Department of Physics &and Astronomy, London, Ontario, Canada N6A 3K7 (jlandstr@uwo.ca)^{2} European Southern Observatory, Casilla 19001, Santiago 19, Chile (gmathys@eso.org)
As a result of major surveys carried out during the past decade by Mathys and collaborators, we now have measurements with full phase coverage of several magnetic field moments, including the mean longitudinal field , the mean field modulus , and in most cases the mean quadratic field and mean crossover field , for a sample of 24 chemically peculiar magnetic (Ap) stars. This represents an increase of a factor of order five in the stellar sample with data of this quality, compared to the situation a decade ago. We exploit this dataset to derive general and statistical
properties of the stars in the sample, as follows. First, we fit the
available field moment observations assuming a simple, axisymmetric
multipole magnetic field expansion (with dipole, quadrupole, and
octupole components) over each stellar surface. We show that this
representation, though not exact, gives an adequate description of the
available data for all the stars in this sample, although the fit
parameters are in many cases not unique. We find that many of the
stars require an important quadrupole and/or octupole field component
to satisfy the observations, and that some (usually small) deviations
from our assumed axisymmetric field distributions are certainly
present. We examine the inclination
Online publication: June 30, 2000 |