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Marc Hempel

Publications and source records attributed to Marc Hempel.

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Do dusty A stars exhibit accretion signatures in their photospheres?

We determined abundances of O, Ca, Fe, Ba and Y for a sample of dusty and dust-free A stars, taken from the list of Cheng et al. (1992). Five of the stars have an infrared-excess due to circumstellar dust. Ongoing accretion from their circumstellar surroundings might have modified the abundances in the photospheres of these stars, but our results clearly show, that there is no difference in the photospheric composition of the dusty and dust-free stars. Instead all of them show the typical diffusion pattern which diminishes towards larger rotational velocities.

astro-ph

Dusty and dust-free A stars

We present preliminary results of our search for circumstellar absorption features in the Ca K lines based on high S/N observations obtained with the ESO CAT/CES system.

astro-ph