1 STRUCTURE AND EVOLUTION OF NEARBY OB ASSOCIATIONS
We present the rst results of a comprehensive census of the stellar content of the nearby OB associations based on Hipparcos positions, proper motions and parallaxes for 12842 candidate member stars distributed over 21 elds on the sky. We use a new method to identify moving groups in these elds (see de Bruijne et al., these proceedings). Previously, astrometric membership in nearly all the nearby OB associations was known only for stars with spectral types earlier than B5. The Hipparcos measurements now allow us to identify members down to late F. This census provides a rm basis for studies of galactic and extragalactic star forming regions.
Stellar evolution and nucleosynthesis: an introduction to nuclear astrophysics
The new book, An Introduction to Nuclear Astrophysics, by Jean Audouze and Sylvie Vauclair, fills the tremendous need for a work of book length that is more modern than the 1968 textbook. Audouze and vauclair excellently summarize the current status of the field. The book is written at a level that would be quite suitable for use in a beginning graduate or upper division undergraduate course. Audouze and Vauclair, both active French astrophysicists, have made numerous contributions to our understanding of nuclear astrophysics. Audouze in particular, is well known for his work on light element synthesis and on the chemical evolution of the galaxy, so it is understandable that these sections are extraordinarily well treated. However, the authors have also done quite an admirable job in treating the rest of the field: Big Bang nucleosynthesis, nuclear reaction rates, explosive nucleosynthesis and the synthesis of the heavy elements as well as the problems regarding the isotopic anomalies in the early solar system and the use of radioactive decay for estimating the age of the universe.
Preliminary results on an H-alpha map of the Gum nebula obtained with the D-z-A satellite
Hydrogen emissions, including telluric H alpha, in the terrestrial atmosphere were studied. The H alpha experiment was designed to use a monochromatic photometer that would provide measurements of weak H alpha emission originating at altitudes of a few hundred or thousand km, free of contamination by other telluric emissions. The Gum nebula was recorded by the instrument as a much more intense feature than the geocoronal emission. The spacecraft employed and the optical onboard equipment are described. Field of view, spectral response, absolute calibration, linearity, and inflight performance are discussed.