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Doppler imaging results for Ap stars

Published online by Cambridge University Press:  25 May 2016

Artie P. Hatzes
Artie P. Hatzes*
Affiliation:
McDonald Observatory, University of Texas at Austin Austin, TX, 78712, USA

Abstract

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Doppler imaging results for the surface abundance distribution on Ap stars are reviewed. The silicon distribution on these stars is often characterized by depleted spots near the magnetic poles and enhancements in ring-like structures at intermediate magnetic latitudes. These results are consistent with the predictions of diffusion theory. On two stars, γ Ari and CU Vir, the silicon enhancements appear very close to a magnetic pole. This can be explained if silicon is enhanced where the magnetic field has its maximum horizontal field strength and these stars possess a decentered dipole field. Doppler images of abundance distributions on Ap stars may be used to accurately measure the obliquity angle and to estimate the decentering parameter for a dipole field. The chromium distribution on at least four Ap stars show a depleted band coincident with the magnetic equator and depleted spots at the magnetic poles. Such a distribution can only arise if the star has a predominantly quadrupole field, or if horizontal diffusion is playing a role in the distribution of elements.

Type
Session III: “Photospheric Phenomena: Results”
Information
Symposium - International Astronomical Union , Volume 176: Stellar Surface Structure , 1996 , pp. 305 - 320
Copyright
Copyright © Kluwer 1996 

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