Spontaneous fission on the Ap star HR465

Abstract

THERE is an anomalously high abundance of heavy elements on the Cr-Eu subgroup on the Ap star HR465 (refs 1–3). The overall abundance pattern of elements with Z≳40 indicates that the heavy elements originate from r-process nucleosynthesis³. In the r-process abundance curve there is a broad peak in the rare earth region centred around Z ≏ 65 (A≏165). The rare earth elements on HR465, however, produce a peak centring near neodymium and samarium at Z = 60∼62 (ref. 3); this clearly differs from the trend of the r-abundance pattern. Nor does the rare earth peak on HR465 correspond to the s-process abundance peak around barium and lanthanum (A = 135∼140). Moreover the amount of barium on this star is too small to produce this rare earth peak by the local r-process, which begins from the s-process peak of barium and lanthanum⁴. Other explanations for the overabundance of rare earth elements on Ap stars do not seem appropriate for HR465 (ref. 1). I examine here an alternative possibility—that the rare earth anomaly on HR465 originates from asymmetric spontaneous fission.