G. Alecian, O. Richard and S. Vauclair (eds)
EAS Publications Series, 17 (2005) 253-262
Direct evidence for stratification in A/B stellar atmospheres
Institute of Astronomy Russian Academy of Sciences, Moscow, Russia
2 Institute of Astronomy Vienna University, Vienna, Austria
Abnormal line profiles and line intensities observed in Ap stars, and their deviations from those expected in homogeneous atmosphere provide a strong evidence for an existance of abundance stratification. For a sample of Ap stars in the effective temperature range 7000–9500 K abundance distributions of Mg, Si, Ca, Cr, Fe are derived from line profiles, and they are compared with the diffusion calculations. A special attention is paid to Ca distribution for which we found an evidence for the differential stratification of Ca isotopes. Temperature and magnetic field effects on the observed abundance distributions are discussed.
© EAS, EDP Sciences, 2005