High resolution spectroscopy of circumstellar material around A stars

Abstract

We have analysed a time series of high resolution spectra () of the Caii K line of 9 stars which are candidates for the presence of circumstellar material from our previous studies. We have searched for variable narrow absorption components similar to those extensively studied in the case of β Pictoris. Our data show long-term variations in the spectra of HR 2550 and HR 3685 which can be attributed to the dynamics of circumstellar gas. About one third of the sample stars show variable line absorption but only β Pictoris seems to exhibit uniquely strong variations on short (nightly) timescales. In order to examine possible interstellar contributions we compared our results with interstellar data from the literature. The column densities of our absorption features are up to three orders of magnitude higher than those found for the Local Interstellar Cloud.