- The Puzzle of the Metallic Line Stars
In the puzzle of the metallic line (Am) stars, there still seem to be missing pieces. While the “normal” A stars have elemental abundances close to solar, the classical Am stars show stronger absorption lines for most heavy elements in their spectra. Elements with ionization potentials that nearly agree with those of hydrogen or helium have reduced abundances. The Ca ii and Sc ii lines are especially weak. The Am stars have no ultraviolet emission lines. They are binaries that, with very few exceptions, have rotational velocities vsin i lower than 100 km s−1. Of the main‐sequence A stars, 20% to 30% are Am stars. Here we rediscuss previous suggestions that tried to explain the peculiar line strengths in the Am star spectra. In particular, we compare the well‐studied properties of Hyades A and Am stars in order to identify reasons that can or cannot explain the differences. We find that accretion of interstellar material by A stars with distorted magnetic fields, which are weaker than those in peculiar A (Ap) stars, has the best chance of explaining the main characteristics of the peculiar heavy‐element abundances in Am star photospheres. Charge‐exchange reactions also seem to be important.
- Roger Zelazny (Wikipedia)
Roger Joseph Zelazny (May 13, 1937 – June 14, 1995) was an American fantasy and science fiction writer known for his short stories and novels, best known for The Chronicles of Amber. He won the Nebula Award three times (out of 14 nominations) and the Hugo Award six times (also out of 14 nominations), including two Hugos for novels: the serialized novel …And Call Me Conrad (1965), subsequently published under the title This Immortal (1966), and the novel Lord of Light (1967).