Core-valence and core-core correlation effects on hyperfine-structure parameters and oscillator strengths in Tl

Atomic Data Requirements for the Analysis of Chemically Peculiar Spectra

For the past seven years a large, international team of astrophysicists and atomic physicists has been engaged in the systematic exploration and analysis of the extraordinary spectrum of one chemically-peculiar star, chi Lupi (B9.5pHgMn + A2 Vm). The observational data consist of 345 Ã of the star’s ultraviolet spectrum acquired with the Goddard High Resolution Spectrograph (GHRS) on board the Hubble Space Telescope (HST) at a resolving power of approximately 90,000 and an average S/N ratio of about 75 in the continuum. These data were supplemented with new optical-wavelength echelle spectra obtained at the AAT and at KPNO[l]. We have named this study “The x Lupi Pathfinder Project”, because it is in many respects similar to the initial exploration of a strange new land – never before has the ultraviolet spectrum of an ultra-sharp-lined star been observed at this level of detail and accuracy.