Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-03-13
Astronomy and Astrophysics
Astrophysics
10 pages, 6 figures; to appear in "Magnetic Stars 2006", SAO, Russian Academy of Sciences
Scientific paper
We present results of the Ca stratification analysis in the atmospheres of 21 magnetic chemically peculiar (Ap) stars. This analysis was based on the spectral observations carried out with the UVES spectrograph attached to the 8-m VLT telescope. Ca was found to be strongly stratified in all stars with different effective temperatures and magnetic field strengths. This element is overabundant by 1-1.5 dex below logtau_5000~-1 and strongly depleted above logtau_5000=-1.5. Based on the overall Ca abundance distributions, we modelled a profile of the IR-triplet Ca II 8498 line. It shows a significant contribution of the heavy isotopes 46Ca and 48Ca, which represent less than 1% of the solar Ca isotopic mixture. In Ap stars with the relatively small surface magnetic fields (<= 4-5 kG) the light 40Ca isotope is concentrated close to the photosphere, while the heavy isotopes are pushed towards the outer layers. Isotopic separation disappears in the atmospheres of stars with magnetic fields above 6-7 kG. The observed overall Ca stratification and isotopic anomalies may be explained by a combined action of the radiatively-driven diffusion and the light-induced drift.
Bagnulo Stefano
Kochukhov Oleg
Ryabchikova Tanya
No associations
LandOfFree
Ca isotopic anomaly in the atmospheres of Ap stars does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Ca isotopic anomaly in the atmospheres of Ap stars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ca isotopic anomaly in the atmospheres of Ap stars will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-438240