Chemical Composition of the BA II Star HD 46407 and its Bearing on Element Synthesis in Stars.

Coude spectrograms of the Ba ii star HD 46407 and the standard G8 III star K Gem, obtained with the 1004nch telescope, have been measured for wave lengths and equivalent widths. The latter, which are listed in Table 1, have been used to construct curves of growth from which atmospheric abundances of the elements in HD 46407 relative to those in K Gem have been determined, after a preliminary comparison of K Gem with the sun. The atmospheric parameters have been found to be closely similar in the two stars: = 3900 , T1= = 42000, P = 0.5, opacity = solar opacity, and total velocity parameter (thermal plus turbulent) = 4 km/sec. Relative abundances of the following elements have been determined: sodium, magnesium, aluminum, silicon, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, strontium, yttrium, zirconium, barium, lanthanum, cerium, praseodymium, neodymium, and samarium; also less certain values have been found for copper, zinc, germanium, niobium, molybdenum, ruthenium, europium, gadolinium, ytterbium, and tungsten. Carbon has a slightly greater than normal abundance in HD 46407. The elements from sodium through germanium normal abundances, but most of the heavier elements from strontium on have abundances of order ten times normal; these are all given in Table 4. The results have been discussed in the context of a theory of the stellar origin of the elements in the universe and are found to give good support for it. On this theory certain isotopes of the elements heavier than iron are built by a slow neutron-capture process in the interiors of red giant stars. Abundance peaks are produced at nuclei having a magic number of neutrons, e.g., strontium, yttrium, zirconium, barium, lanthanum, cerium, praseodymium, and neodymium, all of which are overabundant in HD 46407. Europium, so prominent in peculiar A stars with magnetic fields, is not built predominantly by neutron capture on the time scale supposed to occur in red giant stars, and its abundance in HD 46407 is no larger than in K Gem. A brief discussion of the possible evolution of Ba ii and S stars is given.