HD 65949: Rosetta Stone or Red Herring

TL;DR

This study analyzes the peculiar chemical abundance pattern of the star HD 65949, revealing complex elemental anomalies and proposing a model involving accretion and diffusion processes to explain its unusual spectrum.

Contribution

It provides detailed abundance measurements for 58 elements in HD 65949 and introduces a novel model combining accretion and diffusion to explain its unique chemical profile.

Findings

Abundance pattern resembles the N=126 r-process peak of solar material.

Significant correlation between abundance excesses and second ionization potentials.

Model predicts primary and secondary masses near 3.3 and 1.6 solar masses.

Abstract

HD 65949 is a late B star with exceptionally strong Hg II at 3984[A], but it is not a typical HgMn star. The Re II spectrum is of extraordinary strength. Abundances, or upper limits are derived here for 58 elements based on a model with Teff = 13100K, and log(g) = 4.0. Even-Z elements through nickel show minor deviations from solar abundances. Anomalies among the odd-Z elements through copper are mostly small. Beyond the iron peak, a huge scatter is found. The abundance pattern of the heaviest elements resembles the N=126 r-process peak of solar material, though not in detail. We find a significant correlation of the abundance excesses with second ionization potentials for elements with Z > 30. This indicates the relevance of photospheric or near-photospheric processes. We explore a model with mass accretion of exotic material followed by the more commonly accepted differentiation by diffusion. That model leads to a number of predictions which challenge future work. Likely primary and secondary masses are near 3.3 and 1.6 M(solar), with a separation of ca. 0.25 AU. New atomic structure calculations are presented in two appendices.