High resolution UV stellar spectroscopy with the HST/GHRS, challenges and opportunities for atomic physics.

Abstract

The Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST) is producing ultraviolet spectra of unprecedented resolution and photometric quality. The authors illustrate this with observations of the ultra-sharp-lined, chemically peculiar B-type star, χ Lupi. The photosphere of this star is rich in heavy elements, and its UV spectrum is replete with transitions of species not commonly observed in astrophysical spectra. It is an excellent "laboratory" for atomic spectroscopy. Kurucz's comprehensive calculations of transition probabilities for the iron-group and other elements provides a reasonable starting point for theoretical spectrum synthesis. However, evidence is found of large systematic errors in his data base for transitions from particular energy levels in Fe II, Cr II, Co II, and other ions.