The pursuit of heavy elements in the HgMn-type star Chi Lupi: Observations with the GHRS in the COSTAR ERA

Observations of the ultra-sharp-lined HgMn star chi Lupi made with the Goddard High Resolution Spectrograph after the Hubble Space Telescope First Servicing Mission display the effect of COSTAR corrective optics upon the spectral resolution of several observing modes. The resolution is restored to levels expected in the absence of the telescope spherical aberration for all observations made through the GHRS Large Science Aperture (LSA). The Small Science Aperture (SSA) spectra are nearly identical in resolution to the pre-COSTAR values while benefiting from higher throughput. The line spread function for the LSA relative to the SSA shows little wavelength dependence and reflects a Gaussian profile approximately 20%-30% broader than for SSA spectra. Absorption features containing components of As II and Bi II represent upper limit enhancements of 2.9 and 2.1 dex for As II and Bi II, respectively, relative to meteoritic abundance determinations