Abundance anomalies in A and B stars and the accretion of nuclear-processed material from supernovae and evolved giants

Abstract

The probability is evaluated that peculiar A and B stars show abundance anomalies from nuclear processes which occurred in companions. The mass accreted from supernova ejecta and the frequency of the accretion both in binary systems and in associations are evaluated. The results show that only one A or B star in a few thousand is likely to show abundance anomalies caused by a nearby supernova. The possibility that the process causing Ba stars would lead to main-sequence counterparts is discussed in detail. The radius stars must reach to produce s-process elements is large and is the likely reason for the period distribution of Ba stars. It is then estimated that only 1.5 percent of all and B stars could have been affected by accretion of s-process material during the AGB phase of their companions. It is also found that at most 1.5 percent of Am-Fm stars formed by a process other than mass accretion could have had their abundances modified by the accretion of s-processed materials.