A Glimpse into the Post-COSTAR GHRS: Detections of As II and Bi II in the UV Spectrum of the HgMn Star $\chi$ Lupi

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Session 7 -- Stellar Abundances Across the H-R Diagram
Display presentation, Monday, 30, 1994, 9:20-6:30

[7.05] A Glimpse into the Post-COSTAR GHRS: Detections of As II and Bi II in the UV Spectrum of the HgMn Star $\chi$ Lupi

G.M. Wahlgren (CSC/GSFC), T. Brage (NRC/GSFC), R.L. Gilliland (STScI), Se. Johansson (Univ. Lund), D.S. Leckrone (NASA/GSFC), D.J. Lindler (ACC/GSFC)

Observations of the ultra-sharp lined HgMn star $\chi$ Lupi (B9.5p) made with the Goddard High Resolution Spectrograph after the HST First Servicing Mission are presented which display the effect of COSTAR corrective optics upon the spectral resolution of various observing modes. The resolution is restored to levels near those expected in the absence of spherical aberration for all observations made through the Large Science Aperture (LSA). Small Science Aperture (SSA) observations are nearly identical in resolution to the pre-COSTAR values. Deconvolution of LSA spectra by the SSA data at three widely separated wavelengths produce relative line spread functions whose breadth shows little wavelength dependence but is approximately 25 \% broader in the echelle data than it is for the first-order gratings. The wavelength dependent throughput of the instrument has been increased by approximately a factor of two over pre-COSTAR levels for SSA observations while the LSA throughput is found to be within 20 \% of pre-COSTAR levels. From first-order SSA observations we have identified line absorption from As II $\lambda$1375.07 \AA\ and tentatively from Bi II $\lambda$$\lambda$1372.6, 1902.3 \AA. A synthetic spectrum abundance analysis confirms that As II is enhanced by over two orders of magnitude over the solar value and is consistent with the As I abundance in this star. The strengths of the blended features containing the Bi II lines are also likely to result from a Bi abundance enhancement of between two and three orders of magnitude; however, uncertainties in the wavelengths and blending components only allow for abundance estimates at this time. Additional evidence for enhancements of both elements comes from comparison of the spectrum with GHRS spectra of Sirius (A1 V) which displays no line absorption from either element.

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